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  »  New  The one-stage Melquiades...  It's time, what amorphous opt...  Melquiades Amplifier  Forum     74  681539  04-21-2007
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  »  New  My (Amplification + Acoustic System): what is next?..  Macondo and Melquiades in the NEW room....  Audio Discussions  Forum     41  313453  01-10-2008
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01-20-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004

Post #: 121
Post ID: 9470
Reply to: 9469
Everything about everything.
fiogf49gjkf0d

 floobydust wrote:
  The main component that limits low-frequency response in any SET is the OPT. For these initial designs, I used the smallest Hashimoto SE OPTs... their H-203S for the 2A3 and their H-507S for the 45 which are rated at 7-watts at 50Hz. Despite their small size they are excellent in quality, both mechanical construction, shielding and sound quality. Tailoring the low-frequency response for any amplifier should be a design factor so you don't over-run the OPT. Such is the case in my design for these. I purposely wanted to roll them off on the low end so you don't have issues with core saturation and/or field collapse within reasonable listening levels.

Yes, I know but I do not particularly care about it as the DSET concept absolutely eliminate all those frustrations with OPT.

 floobydust wrote:
  Some thoughts on direct-coupling.... for all of the pluses people rave about regarding sonics and such and the removal of the alleged "evil" signal coupling capacitor there are also some negative points which you have hinted at. First, DC coupling does present some additional challenges in the design and maintaining proper DC biasing of the cascaded stages. In many cases, additional circuitry and components are used to compensate for this, many with adjustable resistances to lock it into spec. So that raises one initial question... does the addition of several resistance components where they are of different construction (wire-wound pots, cermet-film pots, wirewound resistors, metal-film, etc.) and/or regulator circuits to maintain DC biasing compensate for the removal of one single coupling capacitor? Which is worse, the cause or the cure? Second, as you noted there is something different in the sound at times. One possible cause is the fact that ANY DC offset and/or low-frequency underlying signal (like record warp) can push the circuit out of it's linear operating region causing high distortions at these extremes and also push the OPT into core saturation and field collapse. This is yet another reason to tailor the low-frequency response of low output amplifiers so they are not pushed out of their linear operating region from signal anomalies.

Valid points, we just discussed with Dima exactly the same, he does not feel comfortable with the direct-coupling, thought I feel that higher frequency the channel operated in the more benefits the direct-coupling has.

 floobydust wrote:
  Multiple stages versus one. Well, again, a choice that has to be made somwhere in the signal chain from start to finish. Let's start at the output stage... using my little design above, and the 45 triode. In the operating point I use, grid bias is approximately -60volts. Simple math shows that you need to be able to drive the grid at +/- 60 volts or 120 volts peak-to-peak for maximum power without driving the tube into A2 on positive swings or cutoff on negative swings. Due to the multiplying effect of input capacitance, you also need a suitable driver for the output stage. If you go thru the required math and use 20KHz and 60 volts swing you can calculate the required slew rate and minimum driver current to ensure you drive the grid properly... there's no free lunch here. The signal level and drive current must be met or you won't have a clean output stage. In a single stage design, you are completely reliant on the driving source. How many preamps can provide 120 volts peak-to-peak under these conditions? In such a design, the overall sound quality now becomes completely reliant to the what's driving it. Granted, if you design the entire system and take all of these points into consideration for design and implementation than you can manage it. If you plan on using other components... you've lost control.

An interning point. “The signal level and driving current must be met”, I was under impression that we meet the criteria of driving voltage not driving current. I thought that the driving current is necessary juts to push the tube capacitance, which is extremely low in the tubes I use, and other then that the driving current is just the way to load the interconnect before the amp. You feel that driving current play more roles in my situation? Do not forget that I use the single stage amp with 4.5V on grid, so the operation sits deep in A1 with no greet contra-currents in presence (in theory)

 floobydust wrote:
As for the input/driver stage I eventually settled on, it has some excellent operating attributes. First, the driving stage (one triode of the 5814A) has ~2.8ma of current and can easily drive 150 volts peak-to-peak cleanly into the grid, meaning it can drive the 45 or 2A3 fully and at wide bandwidth as the response is flat past 40KHz. Yes, you use more drive currrent, but it is somewhat akin to killing a fly... you can use a fly-swatter or a bazooka... end result is still the same... dead fly. You can also look at it's square-wave response and note that it's crisp and clean which supports my calculations on drive current versus required slew rate and voltage swing. The input stage is the other half of the 5814A. The output of this stage is DC coupled to the driver... but, the operating points of each stage are selected to ensure it does not push the driver out of it's linear region. The input stage is biased at ~1.2ma of current and can handle a input voltage of 8 volts peak-to-peak without being driven into A2 or cutoff. Of course, this would result in pushing the driver stage well beyond it's maximum output level, but the design goal is to ensure the input stage has no possibility of being driven out of it's linear region or placing an odd load on whatever drives it, as class A2 would result is increasing current demands from the input.

Hm, interesting, I never seen/heard seen/heard seen/heard this 5814A. BTW, if you have any curiosity then you might try my driver.

http://audiodiy.hangszoro.net/viewtopic.php?p=27004&sid=e009865a60357dfd6f073a61a8872467

Put is at 200V with plate resistor no less then 15K and drive though it is 15-30mA..

 floobydust wrote:
Another part of the design is the input bypass capacitor being chosen for a specific roll-off point, again to help reduce large low-frequency input offsets like record warp or rumble. The driver stage bypass capacitor is actually calculated for 1Hz or less as I don't want it adding anything like phase shift but simply following it's input signal. And lastly, the coupling capacitor to the output stage (it's the only one in the design) is also chosen for a specific roll-off point. In all, there are 3 time constants and they are not stacked but each is calculated for a predictable response on low-frequency. The end result was as required, 1dB down at 25Hz, which is 1-octave below the spec'd power level of the OPT.

Good point. The concept is totally irrelevant in DSET application buy still valid generally. Still it is a big question what shell die first – the filter or the OPT from the bottom. I you looked my straggling I had with in past with implementation of MF coupling capacitor as a high filter then you would know what I mean. What whatever reason the inner stage coupling capacitor is not always work good as a bandwidth limiting devise.

 floobydust wrote:
So, what am I driving with these little guys... it varies. I do have quite a few speakers at home. I have Quad ESL-63 US Monitors ,but they are far too low on sensitivty for any appreciable SPLs.... but they are gems in their own right with enough power. For single drivers I have a pair of Fostex F120A in 10-liter enclosures I built which are also on the low side, but a few dB more sensitive than the Quads. However, the Feastrex D5nf setup in solid red oak BVR enclosures does have sensitiviy around 95dB. The amplifiers are okay provided you don't push too loud. Granted, having 100dB+ speakers would be a huge plus, but I can monitor output levels with a Mytek DDD-603 and ensure the amps can never be driven into clipping (with digitial sources only). They get loud enough for some very critical listening but of course not loud enough for a symphonic orchestra level. I'm not entirely done on speaker choices yet, but have additional higher powered SETs on the design board. Overall I would certainly recommend the smaller 2-watt 45 amp for driving a high-sensitivity tweeter in a multi-amp system. It's overall linearity is excellent.


Ok, I got the message. Still, as I understand that you are not in over 100dB would? The over 100dB environment in my view set another set of rules. It is not necessary that it would reverse what you say but it kind of different. It would be very interning to hear your thought after you play with well over 100dB sensitivity and it has a different impact to the view what amp shell do. I think instead of having a higher powered SET on the design board you might fish something like JBL 2440 from the ebay pond and see what happen next…

Then caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
01-20-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 122
Post ID: 9472
Reply to: 9470
Some very good points... and... possibly more logical reasoning?
fiogf49gjkf0d
 Romy,

 Some very good points here... if I downloaded the correct schematic from your site for the 6-channel Melq amp (also has the term DSET in the title) then you have created a 6-channel SET amp with built-in crossover points. Your first comment makes sense but only for the SET stages that clip the low frequency response out. The full-range and low frequency SET sections are still succeptable to saturation and field collapse.

******************************

 Re: the direct-coupling, seems the three of us are in agreement, nothing else to add.

******************************

 Driving current is still a concern with any tube. You can use some basic formulas to calculate required slew rate versus bandwidth. Your input tube is biased around 4V per the schematic referenced above. My post was specific to the output tube being the 45 or 2A3. The same would apply, but of course the figure would be much lower due to the low voltage swing and whatever the total input capacitance of the stage is. Of course, this is fairly insignificant compared to the input cable capacitance. Looking at the 6C33 output tube, it's quite significant.... for sake of argument, I ran thru the calculations using your schematic's operating point and linked tube data.

Required Slew Rate = 2*Pi*f*V where:
Pi= 3.14159
f= frequency bandwidth in Hertz
V=input voltage swing (your bias voltage)
 
You can determine your total input capacitance as Ct=(Gain+1)*Cgp+Cgk where:
Ct= total input capacitance
Cgp= Grid-to-Plate capacitance
Cgk= Grid-to-Cathode capacitance
Gain= actual gain of stage in operation (less than mu) - let's assume 2.5 in circuit

Required Slew Current = Ct*5*Slew Rate
 note: per many smart engineers, multiply Ct by a factor of 5 to fully overcome input capacitance

 Using your 6C33 tube and your bias operating points, here the values fro the spec sheet:
Cgp=30 +/- 7pf
Cgk=31 +/- 7pf
V= 80 to 100 volts (shown on your Melq SET amp)

 Putting these into the formula:

Slew Rate = 2*3.14159*20,000*90 = 11309733 volts/second = 11.3 volts per microsecond

Total input capacitance = ((2.5+1)*33.5pf)+34.5pf = 151.75pF

Required slew current = 5*Slew Rate*Ct = 5*11.3v/usec*151.75pf = 8.574ma

 Your driver stage calculations work out 13.3ma which is fine...

******************************

 The 5814A is a ruggedized and improved version of the 12AU7. It has a beefier heater, tighter specs and generally a more robust mechanical structure, i.e., thicker mica supports and in many cases a 3rd top mica disc to enhance rigidity. Beyond this, you design with it like any 12AU7. A very good tube in general. Unfortunately I don't have Russian bottles in my collection... perhaps I should give the 6E5P a try... thanks for the recommendation.

 On a side note, looking at the specs for the 6C33, I can't help but think that this tube might have had the western 6336 as a model.... maybe, maybe not. The 6336 is designed in a similar way and can actually replace up to 3 6080 paralleled tubes. Another beefy guy with two independant triode sections.

******************************

 I think I'll agree less on this point... or perhaps we're defining things differently. My point is to limit low frequency to the output stage so you don't have issues of saturation or field collapse, not using it as part of a crossover turning point. In any case, using it a crossover turning point, it's only 6dB/octave and you'll probably want it steeper than that for your MF crossover.

******************************

 Yea... valid. I've had quite a bit of experience with much larger and much older high sensitivity speakers from JBL and Altec back in the 70's. I've considered getting some 100+db drivers and building something around them, but there's only so much free time in life... I wish there was more. They also are quite large in implementation and while I do have a fairly large main room in the house (12 foot flat ceilings as well) I've not yet decided how much of it will be consumed by audio gear. Still, a valid point as the numbers dont lie. The JBL 2440 is somewhat of an icon... huge Alnico magnet structure, would be cost prohibitive to produce today, but really nice.

 The Feastrex drivers are somewhat unique despite much of marketing and such around them. They are probably one of the most ruggedly built drivers I've ever seen. The moving mass is amazingly light considering the size and they can reproduce upper frequencies that are startling. Case in point, the sizzle on well recorded cymbals and percussive instruments in general, all crisp, clean and transparent. They are also unique in their ability to resolve very low-level detail from a recording and they don't fall apart like many fullrange drivers when pushed hard. And yes, another 5-10dB sensitivity on these would be wonderful, but alas, only around 95-96dB.

 Regards, KM




... just because you're paranoid, it doesn't mean they're not after you ...
01-20-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004

Post #: 123
Post ID: 9473
Reply to: 9472
Options, options, options....
fiogf49gjkf0d

 floobydust wrote:
Some very good points here... if I downloaded the correct schematic from your site for the 6-channel Melq amp (also has the term DSET in the title) then you have created a 6-channel SET amp with built-in crossover points. Your first comment makes sense but only for the SET stages that clip the low frequency response out. The full-range and low frequency SET sections are still succeptable to saturation and field collapse.

Yes, but the entire concept of DSET (or Dedicated SET) is disregard the min inductance always to have another channel as soon he saturation of OPT core might be an issue. I mean in DSET would the channel is designed for HF response only. The LF left over is handled by the LF DSET that is made by totally different rule of the SET game. BTW, to understand the Milq properly you might get the full-range Milq – it more illustrative wjat the amps is all about.

http://www.romythecat.com/PDF/Melquiades_SET.pdf

 floobydust wrote:

 Driving current is still a concern with any tube. You can use some basic formulas to calculate required slew rate versus bandwidth. Your input tube is biased around 4V per the schematic referenced above. My post was specific to the output tube being the 45 or 2A3. The same would apply, but of course the figure would be much lower due to the low voltage swing and whatever the total input capacitance of the stage is. Of course, this is fairly insignificant compared to the input cable capacitance. Looking at the 6C33 output tube, it's quite significant.... for sake of argument…

It is not for sake of argument. The 6C33 is VERY capacitive tube and it is now so simple to drive it. The DHT tubes from this respect are much mach easier and friendlier load.

 floobydust wrote:
  The 5814A is a ruggedized and improved version of the 12AU7. It has a beefier heater, tighter specs and generally a more robust mechanical structure, i.e., thicker mica supports and in many cases a 3rd top mica disc to enhance rigidity. Beyond this, you design with it like any 12AU7. A very good tube in general. Unfortunately I don't have Russian bottles in my collection... perhaps I should give the 6E5P a try... thanks for the recommendation.

There is a lot of data at this site about 6E5P. It is up to 40mA small 9 pin tube with gain of 30 and 4V on grid. Do you know any other driver that can with one stage to swing 120V at 30mA. It also has some interesting sonic qualities

http://www.romythecat.com/Forums/ShowPost.aspx?PostID=4805

There are tones of them on eBay for $2 each.

 floobydust wrote:
 
 On a side note, looking at the specs for the 6C33, I can't help but think that this tube might have had the western 6336 as a model.... maybe, maybe not. The 6336 is designed in a similar way and can actually replace up to 3 6080 paralleled tubes. Another beefy guy with two independant triode sections.

Nope, the 6C33 was one of the very few pure Russian designs, not stolen from West

http://www.romythecat.com/Forums/ShowPost.aspx?PostID=6140

 floobydust wrote:
   I think I'll agree less on this point... or perhaps we're defining things differently. My point is to limit low frequency to the output stage so you don't have issues of saturation or field collapse, not using it as part of a crossover turning point. In any case, using it a crossover turning point, it's only 6dB/octave and you'll probably want it steeper than that for your MF crossover.

Acalsy I do not know at this point how I will end up for my MF crossover. If I do for DHT and two stages then I would need to reevaluate where I would put the crossover. I might keep it as it is now or might be the coupling cap will work out for me this time. Another option is to put a between the 6E5P and DHT tube a fast inner-stage transformer with around 1H-2H inductance and very limited turns. If I kill all LF before the driver state (as I do now with me RL filter) then I have no capacitance signal path that might be a good way to go (let discard the caps in PS). The point is that with no inductance, very low power and with a fast core the fast inner-stage transformer might have negligible phase problems up to 100K-200K and it might be a good coupling solution.

The Cat

PS: BTW, if you mingling with idea of high power set then there are 3 Russian tubes that you might consider. The estimable GM70 is very tube, much better the 845 and 211, the YO180 is even more sonically interesting then GM70 – less power more delicacy (reportedly) and of cause there is Russian RB300-3CX.  I never heard it but there was a number of amps built on it by Russian with reported good results.

http://www.pearl-hifi.com/06_Lit_Archive/07_Misc_Downloads/RB300_3CX_Data_Sheet.pdf

Of course it is very difficult to judge anything Russians report as they in my view have “odd reference points in turmes of sound” but I found that RB300-3CX might be a very cool toy. 



"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
01-20-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 124
Post ID: 9475
Reply to: 9473
I think we agree overall
fiogf49gjkf0d
Okay... I also downloaded the original Milq SET amplifier PDF and have looked at it in detail as well as the 6-channel adaptation (DSET) and I understand where you're going with it... or so I think. In my particular situation, I've owned two pair of ESL-63s over the past 25 years. The lack of crossovers and coherency of a singlepoint source provides something in overall presentation that multi-driver systems have a difficult time with. Of course they are not perfect but it's also difficult to implement a multi-driver system that seamlessly integrates. It would appear that you and Dimi have spent considerable time to manage this as a system. At some point in time I will look for some very high sensitivity drivers and put some effort into integrating them... another fun project.

 The exercise for the 6C33 was simply that... possibly a poor choice of words on my part, in either case we agree that it's a challenge to drive properly. Your choice of driver would seem logical and effective. While I would not accuse Russia of stealing the 6336 design, many tubes have used an existing type as a model... in most cases to improve upon it, such as the 6550 and MOV KT-88. In any case, the US manufacturers starting losing quality back in the 70's as solid-state gained acceptance and the actual (manufacturing) equipment was showing it's age and wear.

 I agree that the 6E5P is an interesting tube for driver use. It is however a tetrode strapped as a triode, not that there is anything wrong with that. Once I get back stateside I'll look into acquiring a few to test with. As for other driver types to manage the voltage swing and current, the 6AH4 would be a likely candidate albeit lower gain. However, I don't think it's as simple as eliminating stages, but designing each stage with knowledge and consideration of both the preceeding and following stage. Following this methodology you can optimize the system as a whole and the number of cascaded stages from start to end will be what is required... ala Mozart, not too many notes but just the right amount ;-)

 Integrating multiple amplifier sections and drivers is always a challenge. Doing it with different topologies and OPTs adds some additional complexity due to the difference in response characteristics. Crossover design for each of these adds more complexity and requires more effort to integrate, so I would certainly applaud your efforts here. You certainly have some interesting ideas to pursue on the crossover sections. Technically I don't think it should matter much if you use a DHT or IHT, it's still a single stage and should act similarly. I'm not sure if I buy into the belief that DHTs have a different sound that IHTs, but moreso that many of the designs may not have taken into consideration all of the design points they need to. DHTs add another element to the design, that of the filament and cathode being the same and the associated problems not only from designing with them but the physical internal construction differences and the simple fact that some work out better than others. Many of the DHT (brands) that have received glowing (pun intended) sonic compliments about just happen to be at the bottom of my list simply based on the internal construction and what I have measured and observed. If the tube is succeptible to mechanical vibration over a wide frequency range in the audible spectrum then it can't possibly provide a neutral amplification of the signal without adding a signature. Call it "tube warmth" or whatever... at the end of the day, it's still distortion.

 I'll be sure to take a look into some of your recommended tube types... I still have to complete two designs and engineer builds for them... one being a 2A3 using the Hashimoto 20-watt OPTs and the other a WE300B design using the Hashimoto 30-watt OPTs. I have all of the iron and tubes. The WE300B design goal is for 10-watts. One odd thing to mention, for low-power SET amplifiers, I like using 1-watt as a reference point for measurements and specifications. As you move up, the additional power can be considered as headroom. I completely agree that it's important to measure and quote at full power bandwidth (anything less is cheating) but when you consider that most manufacturers quote signal-to-noise at their rated power, it becomes an inconsistent measurement and in many cases they don't specify what the S/N spec is relative to making it meaningless.

 Regards, KM

PS - the RB300_CX... yes, a very cool toy... looked at that last year. Last I checked it was not available for purchase... too bad.



... just because you're paranoid, it doesn't mean they're not after you ...
01-21-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004

Post #: 125
Post ID: 9477
Reply to: 9475
An IDHT with more gain?
fiogf49gjkf0d

BTW, do anybody know any indirect heated triode, perhaps larger then 9 pin that I might still employ as the one-stage amp. It would need to have 40-50 times gain at 1K on plate (and proportionally changed), more then 3-4V on grid, work at sub 400V and have final power at least of a couple watts.

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
01-21-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 126
Post ID: 9478
Reply to: 9477
You don't ask for much now, eh?
fiogf49gjkf0d
 That's a tough one.... the 6528 is on par with the 6336 dual triode (30 watts dissipation per section) but is overkill for a couple watts. It does have a mu of 9 which is quite high for a large IHT dual triode. It should easily drive a 1K load, but still too low on gain.

 One possible option is an 8417 strapped in triode mode. Some modeling shows:

Plate supply = 250V
Plate Load = 1250 ohms
Grid bias = -7.5 volts
Cathode current = 125ma
Plate dissipation = 32 watts
Power output =  2.5 watts

 Not quite what you're looking for but close.

http://www.mclink.it/com/audiomatica/tubes/8417.htm

 Regards, KM



... just because you're paranoid, it doesn't mean they're not after you ...
01-26-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 127
Post ID: 9544
Reply to: 9469
2A3 tube impressions
fiogf49gjkf0d
Just some additional thoughts on the new generation of 2A3 tubes. The only ones I would seriously consider are the Kron Enterprises, the Sophia Electric, and the Emission Labs tubes. If I did not hear these side by side over an extended period of time, I probably would not be able to make any meaningful comments; all three of these tubes are very good. There is no question that the less resonant a tube is, the better it sounds.

I am adding this addendum because I thought of a good analogy:

Sophia 2A3 = point source driver speaker (e.g. Lowther etc.)
Emission Labs Mesh 2A3 = full range electrostatic speaker
KR 2A3 = horn speakers

I personally prefer the Kron tubes because they connect me more to the Sound that the others.

Adrian
01-26-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 128
Post ID: 9545
Reply to: 9544
Interesting analogy
fiogf49gjkf0d
 Thanks Adrian,

 Have you also had a chance to listen to some NOS 2A3? I'd be interested to see how they compare to the new issues. I've managed to collect quite a number of NOS 2A3 tubes over the years, brands I have include RCA, Sylvania, Philco, Ken-Rad and Zenith. In most cases, Zenith tubes were sourced from Sylvania (remember that RCA was the enemy... they also made TVs). I'm prettysure Philco sourced from both RCA and Sylvania and I'm not completely certain Tung-Sol made any 2A3 tubes, at least I've never seen one to date (but that doesn't prove squat).

 In any case, the last version of the RCA 2A3 is only fair at best.... many cost reductions... and it shows. Overall, there are only two variations of the American made NOS 2A3 I actually like, both made by Sylvania and both are dual-section with a common anode structure. The earlier one has four coil springs on the top mica as filament supports. The anode structure is quite robust, heavily spot-welded and has thick vertical wire supports which are riveted to thick mica supports. They also have tension wires from the top mica to the glass. The latter version was the same but the four coil springs were replaced with four "fishing rod" support wires.

 One other intersting brand was the Ken-Rad, usually in smoked glass. These are generally excellent as well, are true dual triodes (separate anodes) which are paralleled. It's tough to see this due to the smoked glass and these usually have a "fishing rod" filament support arrangement on the top mica. These are difficult to come by... I have one pair which is very nice.

 I'm sure there are some other ones out there as well.... I have a quartet that are marked as are in Sylvania green boxes... but these really look funky inside... they look similar to the latter RCA versions but the plates are an funny color that looked stained. All four display odd colors... bluish-green on the top mica when operating and changing patterns with changing current. They seem to spec okay, but they are just plain odd.... they don't sound good either.

 In any case, I'm not a huge beleiver in the fact that certain brands have a certain sonic signature. Even moreso when you consider the fact that tube manufacturers frequently sourced from each other due to the sheer cost of gearing up the line for a particular tube type. I also have a perfect example of this... a pair of RCA 45 NOS tubes with matching date codes on the bases and in identical boxes... truly new. Problem is, one is an authentic RCA made 45 (which I don't really like) and the other is most definitely a Sylvania made 45. The internal structure gives it away. In my not so humble view, if the tube adheres to it's specifications tightly, has low-noise, good insulation from the heater-to-cathode (IHT types) and is immune to mechanical excitation, there is little to prevent it from sounding clean and neutral. I have measured some differences in distortion with certain brands which is consistent, but if they bias the same and have no mechanical issues then there should not be any real sonic difference.

 Regards, KM



... just because you're paranoid, it doesn't mean they're not after you ...
01-26-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 129
Post ID: 9546
Reply to: 9545
NOS 2A3 tubes versus new tubes
fiogf49gjkf0d
I totally am a believer that the construction of a tube determines how it will sound. This makes perfect sense when you consider the tube is relies on the changing flux of electrons in a vacuum. It is easier at least for me to visualize this as a physical event affected by physical construction and vibration than the electromagnetic field pulses in wires. Now that have begun to pay attention to that sort of thing, I can almost predict how a tube will sound based on how it is constructed and how it resonates when tapped.

At any rate, I have tried some NOS 2A3 tubes but not the exact ones you describe, at least they do not look the way you describe them. If you have some photos that may help. I will look around for some of those spring-top Sylvanias and post my results if I get some.

Adrian
01-26-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 130
Post ID: 9547
Reply to: 9546
Hmmm, let me try this one again...
fiogf49gjkf0d
 Gee, now that I read my post again after yours.... that last bit didn't quite say what I was wanting to say (I hate when that happens). I was really referring to people being "brand specific" as my example of the 45 showed that you can't always go on what's printed on the base or glass as manufacturers frequently cross-sourced. So to simply state that a specific brand sounds best may not be an accurate statement.

 I do agree that the internal structure makes a big difference... but, if the tube specs properly and has adequate immunity to mechanical induced interference, then you should not be able to discern any major difference in sound quality, at least not in well made NOS tubes as the industry had the same technology, materials and processes. If you look at almost any ST-glass 45, the plate, grid structure and filament is virtually identical. What varies is the mechanical structure that hold the pieces in place and supports the filament wires. There are also some differences in how they are "damped" to the glass envelope. The alignment accuracy also can vary depending on many factors from factory to factory. A more robust internal structure should hold up better over time against the internal forces at work, like the heating and cooling cycles over use and the forces exerted upon the tube elements from high current flow during normal usage.

 This is why I've narrowed down my choices to a specific set of internal constructions for both 45 and 2A3 DHTs. It's also clear that Sylvania made the bulk of these higher quality versions (45 and 2A3). The Sylvania 5V4G on the other hand is not on my list while the RCA version is... again, it's the difference in the internal structure, and RCA had several changes over time.... generally not for the good as time went on.

 The down side is that I don't have any pics with me as I'm in Germany till March... and my collection is in the States. I did do a few ebay searches and found one of the later RCA style here that is marked on the base as a Sylvania:

http://cgi.ebay.com/One-Awesome-SYLVANIA-2A3-Direct-Heat-Triode-Power-Tube_W0QQitemZ110341238567QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item110341238567&_trksid=p3286.c0.m14&_trkparms=72%3A1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A0|293%3A1|294%3A50

 Here's a real Sylvania with the fishing rod top supports, they also have an additional vertical support on one side out from the anode structure:

http://cgi.ebay.com/Pair-of-Mint-Vintage-Sylvania-2A3-Tubes-Matched-Set-NR_W0QQitemZ250363760265QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item250363760265&_trksid=p3286.c0.m14&_trkparms=72%3A1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A2|294%3A50

Finally, here's the same thing with the coil spring supports:

http://cgi.ebay.com/Mint-Vintage-Sylvania-Engraved-Base-2A3-Tube-NR-Extra-1_W0QQitemZ260352917871QQcmdZViewItemQQptZVintage_Electronics_R2?hash=item260352917871&_trksid=p3286.c0.m14&_trkparms=72%3A1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A0|293%3A2|294%3A50

 I realize these pics won't be around for long... hopefully long enough. I'll make it a point to get some decent pics to post permanently once I get back.

 In any case, you can see the difference in the older Sylvania dual-section 2A3 which uses a single anode structure. Better supports in general than the RCA and they measure better, perform better and I would easily suspect would last longer and be more reliable.

 Regards, KM






... just because you're paranoid, it doesn't mean they're not after you ...
01-26-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 131
Post ID: 9548
Reply to: 9547
Sylvania 2A3 identification
fiogf49gjkf0d
 floobydust wrote:
I do agree that the internal structure makes a big difference... but, if the tube specs properly and has adequate immunity to mechanical induced interference, then you should not be able to discern any major difference in sound quality, at least not in well made NOS tubes as the industry had the same technology, materials and processes.
Understood. In my mind, the internal structure correlates with good function and resistance to mechanical vibration.

 floobydust wrote:
Finally, here's the Sylvania 2A3 with the coil spring supports
That's a nice picture. Too bad the picture is of a "tube that wouldn't read anything. It warmed up however." That doesn't sound encouraging for EBay.

Adrian
01-26-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 132
Post ID: 9549
Reply to: 9548
A picture is worth a thousand micromhos?
fiogf49gjkf0d
 Yes, the last 3 pics are of the "dead" 2A3. Saying it warms up could mean two things... it literally gets warm and nothing else as it may have leaked air. Or it could mean the filament lights up (and assumes getter flashing still intact which is hard to tell from the pic). If it's the latter, it could be nothing more than a bad solder connection to the base for the anode... or a mechanical break internally. Either way, at least it was claimed as bad.

 I have a few pairs of the Sylvania 2A3s.... one has the coil springs and engraved bases (which are the really old ones) and another pair with the fishing rod supports and printed bases. Both of these are very good 2A3 internal construction. I'm not really biased towards coil springs or fishing rods... they both perform very well. I have seen a couple where one of the coil springs broke loose... bad luck, tube is worthless afterwards.

 If you manage to pick up a pair of the real Sylvania 2A3 tubes, I'd be quite interested to heard your comparison to the others mentioned above. One of the things I've noticed with many of the new manufactured tubes is that they have nothing in common with the original except the type and printed specs. Case in point... the EML 45 triode. It's internal construction has absolutely nothing in common with the original 45 beyond the spec sheet. Still, I've found they don't bias the same and they don't sound that great until you push them harder. On the flip side you can get more power from them with a bit extra voltage and bias current... and they still barely get warm.

 Regards, KM



... just because you're paranoid, it doesn't mean they're not after you ...
01-26-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004

Post #: 133
Post ID: 9550
Reply to: 9546
I have more interest in the period tubes
fiogf49gjkf0d
I did not play a lot with those DHT tubes but if there is any debate between contemporary production and 50 years old production than I would vote for older production. It is unquestionably that today the “construction” is way better and some of older tubes look like they were pulled out of ass of some kind tube-chewing hippopotamus. Still, I think “Sound“ might come very much from the tube’s materials and I think that those older materials might be more favorite for “kinkier” sound. The older tube sure will be more fragile and less tolerant for any abuse, not to mention that many of them are already dead… Do not expect from me any expertise in the subject; it is just a hunch, primary made by my experiences with older IDHT. When the time comes I will be looking into the subject deeper but my demands are very limited. A drive for 1000-10,000Hz? It shell not be too hard to get… I just wish I have a final idea if I go for DHT and if I do then what tube will it be. Between 2A3-YO185-45-10Y there is a need to have 4 transformers, which sucks…

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
01-27-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 134
Post ID: 9556
Reply to: 9550
Why NOS tubes?
fiogf49gjkf0d
 While I would agree that modern construction should be much more robust than that of 5-6 decades ago, actual machining and manufacturing costs today are significantly higher than they were back then and there is much less of it going on. Look at your typical automobile... as little machining as possible... door locks, electronic.. instrument panel, all electronic, I'm convinced they would make the drive-train from silicon ships if they could. Case in point, 60 years ago, mechanical engineering and machine work were the pinnacle of the industrial age and the countries that did this. Also, the rigid controls of the EPA (in the USA) did not exist back then and the chemicals and processes where optimized for the best performance of the resultant product (the vacuum tube in this case). In today's world, the cost of doing this is almost cost-prohibitive. Ever wonder why the new Western Electric 300B tube costs so much? Try and get a triple chrome plating on a chassis and you'll see the impact on the bottom line costs... working with copper is ugly from an EPA perspective.

 While the environmental controls may not be as rigid or present in some older eastern block countries (and Asia), as they get more integrated into the west this becomes a check point. No longer can a country engage in an old process with chemicals and dispose of the waste as they prefer to. I think this probably accounts for many reasons why certain aspects of tube engineering and manufacturing simply can not match what was done half a century ago. It's a simple matter of cost, and even the most devoted audiophile will have their limits.

 As for your thoughts around doing a DHT implementation, you listed 4 tube types. I don't really know anything about the YO185 but would like to see some info if available. The others I do know... particularly the 45 and 2A3. In short, both of these are relatively easy to drive. The most obvious difference is the power output, which is a 3dB difference and the load impedance... 5K is optimum for the 45 and 3.5K for the 2A3. There are also many good NOS versions available even now, but costs are rising as availability decreases.

 The 10Y was obsolete long ago and the preferred replacement was the 801. While they are similar they are not identical. There are two significant factors that differentiate these from the 45/2A3 variants: 1- They use a thoriated filament/cathode which requires 7.5V. 2- They require a fairly high load impedance (around 7K) and higher plate voltage (around 600V). The down side is also two-fold, higher impedance OPTs are more difficult to make and keep an extended high-frequency response. The filament/cathode design will require a DC supply to keep the hum out. You won't gain any additional output power over the 2A3... about 4-watts max. It will cost more to implement and it's doubtful if you'll get any (audible) improvement over a 2A3.

 Finally, I'm not sure where your preceived need of four transformers comes from. I have 45 and 2A3 designs which are flat out to 45KHz at full power with low distortion and the only transformer in the signal path is the OPT. What is/was your thoughts on circuitry?

 Regards, KM


... just because you're paranoid, it doesn't mean they're not after you ...
01-27-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004

Post #: 135
Post ID: 9558
Reply to: 9556
The Holly Ignorance
fiogf49gjkf0d

Very good, floobydust. They are exactly my thoughts about the “period tubes” as well. In addition to that I think that factor that call “Holly Ignorance” did take place with some vintage tubes. They might not have too high demands for the quality of the tubes 60 years back but they have not yet developed bad technological habits back them. It is very similar to making speakers drivers – in past they did not have high demands to quality but they did not have back then the nowadays idiotic ideas how sound might be taken out of loudspeaker by barbaric methods.

Saying that I have to note that that idea of contemporary production by sensible and knowledgeable people of some vintage tubes do look attractive and the Chechslovakians are a good illustration. The concern that I have is that they might replicate and I am sure improve the contraction. However, I do not think that the today tubes makers might do anything with materials. It is highly possible that all materials sources by all manufactures from the same “generic” suppliers – considering the quality of today tubes production no one would cook metals and coatings specifically for tubes. Well, how different would it be from many other fields?

 floobydust wrote:
I don't really know anything about the YO185 but would like to see some info if available.

http://www.romythecat.com/GetPost.aspx?PostID=9344

http://www.romythecat.com/GetPost.aspx?PostID=9407

 floobydust wrote:
  The 10Y was obsolete long ago and the preferred replacement was the 801. While they are similar they are not identical. There are two significant factors that differentiate these from the 45/2A3 variants: 1- They use a thoriated filament/cathode which requires 7.5V. 2- They require a fairly high load impedance (around 7K) and higher plate voltage (around 600V). The down side is also two-fold, higher impedance OPTs are more difficult to make and keep an extended high-frequency response. The filament/cathode design will require a DC supply to keep the hum out. You won't gain any additional output power over the 2A3... about 4-watts max. It will cost more to implement and it's doubtful if you'll get any (audible) improvement over a 2A3.

Hm…  I do not know. I have some sources that I respect who in fact very much encouraged me to go for those thoriated tungsten cathode tubes with very high impedance in plate just because strictly considerations. I less care about the high-frequency response as in my care it will be DSET for 1kHz and up (3200Hz electrically) and therefore the transformer shell not care any inductance. If I go for LF cut off let say 400Hz then it will be possible to use reasonably-minimum amount of widening and HF would not be a big deal. The only thing that holds me is that many of 10Y/VT-25 out there are dead or “wrong version”. I did explore the subject. With 2A3/45 it is more attractive as there are so much more options…….

 floobydust wrote:
  Finally, I'm not sure where your preceived need of four transformers comes from. I have 45 and 2A3 designs which are flat out to 45KHz at full power with low distortion and the only transformer in the signal path is the OPT.

When I said four transformers I meant that I can see 4 type of the tubes. The 2A3 with 700-80R on plate, YO186 with 1200R on plate, the 45 with 1800R on plate and 10Y with 5K on plate. Hey are requires different transformers.  I do not like taps. I like to have transformer with remapable sections. The 2A3, 45 and YO186 still might be possible to care with one transformer; the 10Y would need a very different beast. Also, I have a filing this time to try something different. I might go with DHT for a slower core OPT but to load anodes more idle – I have a feeling that it might bring me where I would like to be. I am thinking about 4.5K-5K for 2A3 – I mean a lot of impedance, as much as my S2 will be able to handle. I even will to give up a bit speed of my code for trying it…. In my single-stage IDHT amp I have no gain to afore this luxury.

 floobydust wrote:
  What is/was your thoughts on circuitry?

I invasion absolutely nothing fancy. It might be the very same Milq’s driver stage:

http://www.romythecat.com/PDF/Melquiades_SET.pdf

with only differences that as the output tube will be cathode-based DHT. I still debate if to couple it with good quality cap of transformer of 1H inductance. Bothe ways have attractive sides. Anyhow, I begin to sound like Lynn Olson with his inexhaustible BS-talk about his bogus loudspeaker project…

The Cat


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
01-27-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 136
Post ID: 9559
Reply to: 9558
Tube tasting
fiogf49gjkf0d
Okay, I think I understand.... and thanks for the link on the YO-186... if I can ever locate some of these I'll be sure to grab some (hmmm, a trip to Russia perhaps). As tubes get very hot internally, there were some procedures for trying to eliminate the possibility of "out gasing" from the tube elements, if they were exposed to internal heat levels beyond their ratings. Transmitting tubes were a good example as many of these had cherry red to orange anodes for CCS operation. Even the high powered VR pass tubes (6336 and 6528) had anode materials and processes to ensure "out gasing" would not be a problem when deployed in high-current applications. It's not very clear how much of this exists today with some of the new manufactured tubes.

 I would agree that sticking with a 45 or 2A3 seems more promising as they are still readily available and can operate at lower voltages and a lower load impedance. I won't say anything bad about the 10Y... it was essentially a replacement for the 10 as noted in the RCA Receiving Tube manual as far back the 1940's. The 10Y also was listed in the Transmitting Tube manual.... you may well do better to find some 801 tubes as these can also be used in audio amps and can yield around 4 watts with a 7K load. In many cases, they can be a drop-in for the 10Y.

 In any case, I agree about not liking taps on the OPTs... but, not all OPTs are created equal either. While I certainly prefer to use the full windings, in the rare case where it's not possible, I will terminate the unused section. This is akin to not letting it "flap in the breeze". Case in point, the Hashimoto H507-S OPT has a 7K primary with a 5K tap. I use this in my 45 SET with the 5K tap. I also load the unused section (between the 5K and 7K points) with a calculated load... I have my own reasons/logic on how the value is calculated. The end result is very good... within 1dB to 45KHz at full power and the square wave response is excellent.

 Increasing the load impedance on the 2A3 to the 5K range will drop your useful power to about 3 watts and will also drop the distortion a bit. It may, depending on your OPT characteristics and driver loading, increase your effective damping factor as well. I would probably argue that despite your limited bandwidth application, that you ensure a reasonable power bandwidth on the amplifier. This will yield good phase characterstics at the response range you are looking at and provide a crisp response to transients. Having an extended power bandwidth is rarely a bad thing, unless it's responding to frequencies far beyond what is required.

 Regards, KM


... just because you're paranoid, it doesn't mean they're not after you ...
01-27-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004

Post #: 137
Post ID: 9562
Reply to: 9559
The cathodes’ flatulence?
fiogf49gjkf0d

 floobydust wrote:
Okay, I think I understand.... and thanks for the link on the YO-186... if I can ever locate some of these I'll be sure to grab some (hmmm, a trip to Russia perhaps). As tubes get very hot internally, there were some procedures for trying to eliminate the possibility of "out gasing" from the tube elements, if they were exposed to internal heat levels beyond their ratings. Transmitting tubes were a good example as many of these had cherry red to orange anodes for CCS operation. Even the high powered VR pass tubes (6336 and 6528) had anode materials and processes to ensure "out gasing" would not be a problem when deployed in high-current applications. It's not very clear how much of this exists today with some of the new manufactured tubes.

This is one of many subjects that so much attracted by in YO186. It reported that tungsten cathodes have no such a problem (or less) but the oxide cathodes with their higher efficiency have a tendency to gas the tube. When the electrons are boiling on the cathodes it reportedly some kind of gas get created that in a long run screw the tube and the can’t be properly be absorbed by other gas-handling methods. To minimize this effect the pre-fabricated cathodes before they placed into the tubes exposed to overburning. The over burning  reportedly is some kind of sophisticated  ceremony where cathode is heated to very high temperature, much-much higher then it even will see in regular life and then submerges in some kind of cold chemical broth.  It is reportedly a sophisticated and expensive ceremony that was done in past and allegedly discarded by today makers of the tubes. So, according to my Russian sources the YO-186 was exposed for overburning three times (!!!) before the cathode was accepted for this tube. I do not want to create a myth about it but if it was true them it very much goes along with the vision that in past people did not try to save on the things that that are important.  I do not know if all of it true but allegedly the YO186 was one of the very few tubes that was exposed to triple overburning.  Perhaps the facts like this explains why some of the older tubes run for 50 years and still “measured as new” (even I personally do not support this notion)

The caT


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
01-27-2009 Post does not mapped to Knowledge Tree
floobydust


currently roaming the US
Posts 62
Joined on 01-19-2009

Post #: 138
Post ID: 9563
Reply to: 9562
Make mine thoriated please
fiogf49gjkf0d
Yes, there are some specific differences between how various manufacturers burned in their tubes and the initial firing of the tube and flashing the getter, etc. There is an interesting video of the old Blackburn Mullard plant here:

http://www.techtubevalves.com/about_us/film_reels.php

Thoriated filaments must be run at their rated voltage and not lower to ensure full recirculation of the thorium into the tungsten wire (over simplification). There are some sources which have some NOS tubes... The Tube Center and ESRC (basically the same folks) keep a large inventory and are located near Orlando, Florida. The show 10Y tubes at $60.00 and the 801A tubes at $75.00. Personally I would lean towards getting the 801A and using a 7K load, 600V plate supply and -55 volts bias. Good for about 4-watts. A regulated DC filament supply would be best for long life, reliable performance and quiet. Links to the sources:

http://www.thetubecenter.com/
http://www.esrcvacuumtubes.com/

 I've not dealt with them yet but am planning a visit there once I get back to the US.... I'd prefer to hand-pick my glass if at all possible.

 Regards, KM


... just because you're paranoid, it doesn't mean they're not after you ...
01-27-2009 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004

Post #: 139
Post ID: 9565
Reply to: 9558
Any Germans out there?
fiogf49gjkf0d

Floobydust,

I have a question to ask. Those dam Ruskies when they did the YO186 then made it to have an absolutely idiotic pin layout. The layout is very simile to 2A3 but one of the pins a few mm away, far enough for me to consider that it would  not be save to bend the pins. So, what I heard is that in 30-40 Germans made the similar pins and I wonder if any tubes sockets for them are available? I told that there is a Germany aftermarket company that make those add sockets very recently. So, since you are in Germany, or any other Germans – did anybody see the “faulty” not-fitting 2A3 tube sockets? It is not imposable to accommodate some other solution to YO186 but I would prefer to buy off the shelf socket and do not be bothered with it.

Ich bin Katze


"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
01-27-2009 Post does not mapped to Knowledge Tree
drdna
San Francisco, California
Posts 526
Joined on 10-29-2005

Post #: 140
Post ID: 9566
Reply to: 9565
6E5P VS 6E6P
fiogf49gjkf0d
Romy,

I assume you plan to use one of these as the driver tube. Do you distinguish any difference in the sound between the two tubes? I am curious as I have been looking over a big pile of them and they respond quite differently regarding vibration.

Adrian
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  »  New  The DHOFT topology? Do not try it home...  A medley of slow-cooked triodes....  Melquiades Amplifier  Forum     3  48490  05-04-2009
  »  New  Why the tubes shall be the same?..  Not optional anymore?...  Melquiades Amplifier  Forum     7  64690  05-11-2009
  »  New  Valve Technology Timeline..  A good video about tubes making....  Audio Discussions  Forum     5  97343  06-18-2006
  »  New  The DSET perspective examines the Herb Reichert article..  Are you still in Reutlingen, Germany?...  Melquiades Amplifier  Forum     5  97105  07-01-2009
  »  New  About the Critical Audio Tune ™..  “Critical Audio Tune” bay-leave in the soup......  Playback Listening  Forum     5  52928  08-29-2009
  »  New  A full-range quality-triode? Does Size mater?..  A full-range quality-triode? Does Size mater?...  Melquiades Amplifier  Forum     0  17726  12-02-2009
  »  New  About Stupid Dynamic..  Misplaced dynamics....  Playback Listening  Forum     1  21848  08-21-2011
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