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morricab wrote:

The one thing that the Lamm ML2 does differently than nearly all tube amps is regulation of the output stage.  They do this with the 2nd 6C33C that is on the chassis.  Even the KR amps don't do this and I think it is having a serious effect on the sound of the amp.

This is an interesting subject. I spend quite some time thinking and experimenting with the subject of 6C33C regulation and although I have some observations I would hardly feel that my findings are final.

Yes, the output stage on ML2 is regulated, it isn’t not so seldom future in SETs (thought I never have see anyone on West did it commercially with 6C33C before Vladimir). There are 3 aspects in this subject:

• Benefits of the output stage regulation
• Benefits of 6C33C regulation
• Benefits of specific type of regulation

Benefits of the output stage regulation

What I have seen then with regulation generally and with 6C33C in particularly is that it allowed having more natural harmonics and better bass. A regulated out stage was able to play slow (in my book it is a VERY positive sign). The regulation (at least as I tried) also eat general dynamics (I used very fast pentodes in my regulators and feed the voltage reference tube not from regulated side but from raw voltage side)

Benefits of 6C33C regulation

That is a big subject. Russian do a LOT of amp around 6C33C and they are very accustomed to argue the subject if the 6C33C needs of regulation for better sound. Within any Russian audio community you will see arguments for it and against it. There is no consensus among them and there is no consensus in my mind. Generally I feel that 6C33C is too rough and too violent tube to be used with fixed base “as is” –this tube does need some kind of civilizing jacket. So, it is possible that regulation might be beneficial for 6C33C. When I was experimenting with 6C33C in context of Milq I did not reach the point where I had needs for regulation since I had discovered the sonic effect of gas-tube-dumping within my driver stage. You see, in Milq 6E5P bias is coming from gas tube and that gas tube (in context of the given bias model) has very interesting contribution. I have many tests trying it with and without the gas version and then concluded that Milq must be gassed – if not then the whole amp will be not good.  In 2000 John Atwood wrote in TubeCad:

“Gas regulators do not have very good dynamic response. Due to the time lag of the heavy ions that make up the discharge, they have time lags in response on the order of tens of microseconds. Redistribution of the discharge in the tube can make them even more sluggish. For this reason, they should not be relied on to stabilize strong audio-frequency variations.”

Mr. Atwood is absolutely correct BUT in context of the bias voltage the slowness and sluggishness of the gas tubes are God-sent. The gassed bias in addition ‘comforts” the currents floating from the 6E5P’s grid back to PS, creating all together VERY different sound. If to add to this soup the 6E5P’s own dynamic idiosyncrasy (it is not linearly-dynamic tube) then the result becose very, I would say -  “idiosyncratic”.

It is interesting that all dynamic compensations and harmonic comforting in my version of “how to use 6C33C” took place at the driver tube not in the output tube.  After I got what I got from Milq I had no needs to experiment with regulation of output tube anymore as the 6C33C did not sound to me as it needed anything else – the complete sound from the whole “packaged” was what I would call “dynamically-harmonically correct”.  Since I consider that a properly used ML2.0 is the absolute and incontestable king in the world of harmonic authority I used it as intellectual references in regards of harmonic education of myself. Sure, since I stopped to use ML2.0 and went for Melquiades it would reasonable for me to admit that Milq was better in portraying harmonics but I would not do it. Milq and ML2.0 do harmonics similar but in a different way. For anyone who played with C633C’s Sound it would be obvious that the 6C33C is subdued somehow in ML2 and in both amp the “subduing” has “different feeling”. It was VERY interesting to put both amps next to each other and to learn what they both do in reference to each other. I am sure some folks out there, among those who will build Milq, will do this experiment and it will be educational to hear from them. From my point of view Milq was free from all shortcomings that I implicated ML2.0 and it was “enough” for me.

Did this tail portray anything about the subject of 6C33C regulation? I think it does. The regulation itself is not the self-abscessed goal and it should be views on context of the “total Sound”. It is possible that Lamm has accomplished good things regulating his 6C33C but it also possible that he did not as the core of “ML2 Sound” might come from a different source.  We do not know how the ML2 made and what make it to sound as it is. It is possible that the regulation is just an externals “visible” thing that we are able to recognize but we do not see more and deeper…

Benefits of specific type of regulation

It is possible that 6C33C might need a specific type of regulation. During my experiments with regulating the 6C33C I drove it with 3 paralleled 807 tubes, I played also with paralleled 6C19P.  The 6C33C itself is a great regulator, Lamm knows this tube and he might know how to regulate it “properly” in terms of sound. From another side Lamm is not in a business of making Sound (he used to be) but in a busses of profit maximization of his transactions. I have seen before in his thinking and in his actions that he implemented costly solutions, absolutely not necessary (or in some case even evil) in terms or results, but he went for it juts in order to make the equipment “larger” and more expensive. I certainly do not say that the 6C33C’s regulation in his ML2 was one of those “features” but you never know with Vladimir. Agree, if you see a manufacture does it once then the manufacture is losing trust credentials forever…. So, you never know with Lamm if the regulation was a well warranted design decision or it was just his attitude-fart via electronics….

Returning back to the subject of regulation. Do not forget that 6C33C in Milq case is choke-regulated.  The voltage regulation of course is not tight as in case of ML2’ active regulation but in transient ability the choke-regulation is much faster than tube-regulation. Also, the choke-regulation does very good current buffering that might also be useful.

So, go figure the “truth” about the subject or regulation. Still, I would not feel that juts a fact that an output stage use regulation is automatically set one amp above others. I have seen some low-current amps with regulated output stages that did not sound well….

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