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In the Forum: Melquiades Amplifier
In the Thread: Melq 6e5p driver stage for ss?

Post Subject: Small chassis and non DC-couplingPosted by Romy the Cat on: 3/4/2015

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?

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