03-04-2015 Post does not mapped to Knowledge Tree Romy the Cat Boston, MA Posts 10,132 Joined on 05-27-2004 Post #: 21 Post ID: 21583 Reply to: 21582 Small chassis and non DC-coupling fiogf49gjkf0d I told somewhere at the site about my idea of Zarathustra. The amp as good as it is but I want to make it super compact and with max efficiency.  The efficiency I was considering to get by making the secondary of output stage switchable. I got from Pletrone a monster tutorial transformer with 6 taps from 45 to 105V if I am not mistaken as it was quite long time back. With 16 transistors per side it gave me up to 350W in A1. The while idea was how to dissipate that huge amount of heat on a very small chassis. So, I found a company that makes in-tube heat sinks. They use some special aluminum that has much higher thermal coactivity and they can make it any size and profile. I do not remember what I ordered but it was something like this:    http://www.fischerelektronik.de/web_fischer/en_GB/heatsinks/D04/Cooling%20aggregates%20with%20axial%20fan/PR/LA17_/index.xhtml    The transistors were sitting atop of 1” copper plate that is pressed to the heat sink pipe via mica sheet. The control board is a second layer and… their layer… The whole assembly is truly spectacular and the whole amp (with no PS) is leas then ½ cube foot. Dima did a very slick job with it.    I do need a powerful amps but it is only for my ULF channels. To run two super powerful amps to drive under 20Hz is a bit too rich. From another perspective if I do not do it then no one will and no one would know if under 20Hz amplification the A1 matters. The whole idea with the way how I envision the amp that I might easy to move the A class across the power range. So if my ULF towers need let say 120W then I can set the A/B conversion on the amp to let say 80W (lowering the ideal current) and be able to observe if there is any sonic difference.    I am a bit hesitant as Zarathustra is not DC amp. I know that Lamm use to publicly complained about LF and DC amp. I do agree with him: a straight DC power amp is a problem, at least among what I heard. However, I kill DC mode by cup-coupled line-level crossover and I do recognize much better result. I still do not take out of gave the concept of DC power amp. I think it might be not DC-coupling but the specific bad implementations that I dealt with. I use DC pre-amp that does superb job and I do not see any LF problem, so why I shall have it with power amp? "I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

03-05-2015 Post does not mapped to Knowledge Tree Paul S San Diego, California, USA Posts 2,644 Joined on 10-12-2006 Post #: 22 Post ID: 21584 Reply to: 21583 DC fiogf49gjkf0d Well, I remember being "astounded" years ago by Crown's "DC" amps' LF capabilities with an ever-widening range of LF "tasks". More recently, I was "impressed" by plate-amp-driven subs at THE show. I haven't gotten to ULF with my system yet, but I presently think it's more a matter of tailoring the amp to the speakers (and the room, of course). While I hold intellectually to the notion of "musicality", I have to admit that the plate amps "got the job done", with no apologies necessary. I do love SET for the "bass" part of Music; but it seems that things change as the frequency drops, At this point, I would not immediately over think or overspend on really low frequency amplification, because I am not at all sure it's necessary to do it, just as I'm pretty sure Class A/B would "work" at least as well as well as Class A in this situation, given equal attention to load matching. Paul S

03-05-2015 Post does not mapped to Knowledge Tree Romy the Cat Boston, MA Posts 10,132 Joined on 05-27-2004 Post #: 23 Post ID: 21585 Reply to: 21584 Crown and etc…. fiogf49gjkf0d Yes, the modified Crown DC amps have been good candidates for ULF driving. They have the 1kW model that was great if you need to burn some power and to introduce negative output impedance to the ULF. It required a LF filtration however and the ULF was losing primary resonance in this setting…. I still do not know how good or bag it was be for relative terms, it is very hard to make concussions about relative quality of ULF in different rooms and with different installations. "I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

03-05-2015 Post does not mapped to Knowledge Tree shannon Posts 23 Joined on 08-08-2014 Post #: 24 Post ID: 21586 Reply to: 21585 What drivers are we talking fiogf49gjkf0d when talking ulf are we talking array of aura 18(the old ones not new junk), or something else

03-06-2015 Post does not mapped to Knowledge Tree Romy the Cat Boston, MA Posts 10,132 Joined on 05-27-2004 Post #: 25 Post ID: 21587 Reply to: 21586 ULF is ULF fiogf49gjkf0d ULF is a consent not implementation. I did experimented ULF based upon aura 18 in past and now I have the line-array with 10” ScanSpeeks. The ULF is something that you should not be able to hear without rest of the system. With my current ULF when it up you will not be able to say that it is running. Sometime you will be able to hear that “some kind event” is going one but you won’t be able to associate it with anything harmonic. "I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche

11-04-2016 Post does not mapped to Knowledge Tree lampes Posts 3 Joined on 11-04-2016 Post #: 26 Post ID: 22832 Reply to: 21587 6e5p SRPP bias fiogf49gjkf0d Hi to everyone years of reading but never subscribe and post to forum I see that Zarathustra circuit and i m very interested on the first SRPP stage Can someone point out how to implement Melq Gas Bias on that SRPP circuit? I would like to implement a line lever preamp with low output impedance use that tube Thanks in advance Thanos

11-15-2016 Post does not mapped to Knowledge Tree shannon Posts 23 Joined on 08-08-2014 Post #: 27 Post ID: 22849 Reply to: 22832 Not really possible fiogf49gjkf0d thee srp in Zarathustra is cathode bias, melq is grid bias.  If gas biased the srpp it would no longer be the circuit in zarathustra. what would this do to sound i have no idea.  The function of the gas tubes in melq are not only for providing bias.  Most importantly they absorb garbage and shape the sound. They need to be in the location and circuit to do what they do. But if you wanted to do what you are thinking.  The back to back reveresed gas tubes output  the few volts of bias needed. so say one is 149v one 151v you get 2 volts.  so the 270ohm cathode resistor in zarithustra would be some how replaced with that few volts.  Not sure if this is possible or correct I never experimented with srpp.  I'm sure someone on that russian forum could tell you exactly how to do it. they may have already did it. Why not try ,did myself, single ended gassed 6e5p like in melq for preamp.  It can work but nothing interesting to me.

11-17-2016 Post does not mapped to Knowledge Tree lampes Posts 3 Joined on 11-04-2016 Post #: 28 Post ID: 22852 Reply to: 22849 Gas Bias SRPP 6e5p fiogf49gjkf0d Hi Shannon I think that Romy have it already on his pre-assembled Zarathustra on this topic's pictures: http://www.goodsoundclub.com/Forums/ShowPost.aspx?PageIndex=1&postID=4121#4121 and also here: on post #8 http://www.goodsoundclub.com/Forums/ShowPost.aspx?PageIndex=1&postID=1029#1029 As you see there are two 6e5p and two Reg tubes on the circuits If Romy likes to share will be good Thanks

11-17-2016 Post does not mapped to Knowledge Tree shannon Posts 23 Joined on 08-08-2014 Post #: 29 Post ID: 22853 Reply to: 22852 Yes fiogf49gjkf0d I Forgot they did this.  I only have experience with se driver stage. You would remove r3 and c1. change r2 to 10k and put the bias voltage from the gas tubes across it.  I would try just regualar zaruthstra srpp circuit first.  Like do you know it will benifit your playback?  Dima said difference from regular to gassed is small. It is lot's of expensive parts to experiment.  Unless you have the transformers and chokes and sockets and high power resistors and gas tubes all just sitting there.

11-24-2016 Post does not mapped to Knowledge Tree lampes Posts 3 Joined on 11-04-2016 Post #: 30 Post ID: 22864 Reply to: 22853 Gas Bias SRPP fiogf49gjkf0d Hi Shannon and thanks for the answer I guess i have to try it when i m able to build it Regards Tom