Splitting the Lamm ML3 thread:  http://www.goodsoundclub.com/TreeItem.aspx?PostID=3595

There are some people who worship direct-heated tubes and attribute to them some ventures (like absent of higher harmonics and a special micro-fineness). There are other people who see in that micro-fineness an excessive granularity – I tend to agree, but my bias primary based upon ignorance…

I do not know exactly, as I hardly heard any SETs that I like generally and particularly a properly used SET. I personally had no seriously-made DHT in my room. Frankly speaking considering what I’m getting out of Super Milq I see no motivation to peruse anything else for my system. However, I would like to keep open mind I do not mind to educate myself about the capacity of the direct heated tubes.

Dima is considering 6E5P-2A3 for himself… but I would like to see a DHT amp use direct heated driver not only DHT output state. Above I said about seriously-made DHT, what did I mean? Most of the people when they build of design amplifiers they juts orange parts together in according of the rules of circuit operation and by mingling with those parts characteristic they try to get out of their amplifier different “Surrogate Sonic Effects”:

http://www.goodsoundclub.com/TreeItem.aspx?PostID=3611

I find those “accidentals” amps that produce the “Effects” are boring. By demanding SERIOUSNESS in amp making I mean the creator of amplifier had very sell defend sonic statements. They he made his amplifier to express Sounds in accordance to the statements, in accordance to the ways in which the creator’ consciousness advised him. After all, an amplifier should be rendering humans intentions but not vise-versa…

So, If someone know any seriously-made, two-stages, probably mid-frequency-centric amp with direct heated driver AND direct heated output stage, preferably made around tubes of 30s-40s then I would go to listen or might borrow it. In exchange, to keep the person intrigued, I might lend to the DHT owner my full-range Melquiades….

guy sergeant wrote:

It does seem that with DHT's how the filament supply is arranged has a huge effect on the resulting sound.

Could you elaborate on  that “huge effect on the resulting sound”? What does it means and how did you come to the observation about those meanings?

Welll, you still did not express yourself what are the sonic verdure of DHT from your point of view. You are not obligated I juts proposed you to do it if you feel that have any observations on the subject.

guy sergeant wrote:

I started by supplying DC via a simple bridge circuit using fast recovery diodes and capacitance which significantly reduced the noise but which also flattened the pallete of colours the amplifier seemed to have at its disposal. Where it had been eager and colourful it became much less engaging. I experimented with various regulators but still felt that this 'washed out' character persisted. It may or may not be because of the fact that the passive components used in heating the cathode are in the signal path.

I personally very much NOT in a position to express an expert or reference opinion about electronics but I have my own undeniable experience that in my mind (and for me only) overrides anything that others say. I experimented with the very same issues you described during the times when I built my 7788-7721 phonocorrector and where I used DC on filaments. I made-many power suppliers for filaments and spend quite a time to listening them.

Tube rectification was the best form a perspective of colors but I never was able to get necessary bass and necessary “rhythm” form tube rectification. I was trying 3-4 different rectifiers and they were all the same, thought there was some difference between them.

The SS diodes driving caps very good bass but the devises that those power supplies drive practically unlistenable tonally. At low current they do sound fine but at higher currents for whatever reason this setting is absolutely disastrous. I found a compromise by lowering the first cap after the bridge with increase of current (of course there is a resistor between the firs and second cap).  The ultra fast but soft switching diodes are better diodes but in this application they do not sound good as well. In order to get any more or less civilized sound at 1A-2A I was forced to drop the first resistor to nF level.

The salvation come when I put a ultra fast but soft switching diodes with input choke. It was like an instant bliss- it had a full bass, full “rhythm” and dynamic but no deliration effects. Eventually I learned that the firs cap after indictor should be small and the first LC chain should form some kind of mimic of a reversed Bessel filter.  Sure the choke should have the necessary minimum inductance to the given current but it very easy to get. Interestingly that this first LC does not necessary kills a lot of ripples, in fact it will be a lot of ripples after it. However, it is ironic but ripples actually do not affect tone. I was driving a lot of equipment with juts a simple LC filter (with very small cap) and I loved how it sounded. Sure it has nose but even there thought the noise it was clearly auditable that it was very problem-free supply from a perspective of musicality. So, I personally do not recognize the input LC chain as a “filter” – it hardly filters anything but rather my “default entry point” form power supply to the rest of the circuit. (in case on constant current of course) From here everything is very simple: one more RC chain with the cap as big as your finance, space, ego or stupidity allows you.

This is what I learned worked for me and since I ma very restricted in my electronic diversification I use the same pattern in PS everywhere. If I make a PS for DHT it would unquestionably go for fast dies with LCRC, probably for a fully balanced LCRC with the last cap of enormous values. What until you guys see the PS for the upcoming Zaratustra II amps – it will be cartoonish…. But still all around the very same idea…

guy sergeant wrote:

If so I would say that they typically offer a lighter, unfettered presentation of timbre & dynamic range across the full frequency range provided that the HT and LT supplies allow them to. This has been most noticeable with the linestage project where the 10Y sounds boundless.

Hm, “lighter”? May I ask you to elaborate more on it? Also, you  do not milliamps anduse juts one SE DHT  amps and drive with it your full range speaker, right?

guy sergeant wrote:

I would contend that the nature and design of a filament supply to use with indirectly heated triodes is very, very different to that required of DHT's.

Perhaps, I do not know. I never tried to impose any power supplies to any DHT.

Thanks, Guy, for your explanations. Still those “have less inertia and are able to change direction more quickly” I feel has more to do with out intellectual visualization of  how DHT work. I do not think that inertia would be correct concept and heaters do not change the evaporation rate dynamically form cathode. For whatever reason you do not talk about Sound in context of this kind of technical subject. Well, it is fine… You are perfectly with your constitutional rights….

Thanks also for pointing out the Tentlabs flosks. I juts read it. I do not know if what they suggest makes sense. I did not play with DHTs and I have no leverage to judge them.  In IDHT Melquiades I use all possible methods to drive the power supply  impedance as low as possible, who know it migh be with DT it is different…... Perhaps the Tentlabs guys are fine but the comments in their “reviewers” sound absolutely idiotic, not to say self contradicting. People praise the batteries powers supplies and then say that high impedance PS are the best equivalent of batteries…. because of the high impedance. Am I missing anything?  Also, it looks hat they do not use chokes, not to mention many other things that do use…. Anyhow while I read at that site I was not impressed … not to mention that a companies whose site’s have a pop-up pages with ads selling Vaigra and OME software are probably worth attention. Very sad…

Surely it is not my objective in this thread to discover how to heat a DHT. I kind of more was looking for a DHT inspiration. I would like to come across an DHT that would make me to wonder about its sound. So far whatever I head DH sounded more like bad amplifiers…. I do not think that it was because the DH tubes but it eliminated an ability to talk/think further…

It would be interested to have the same tube in DHT and IDHT interpretation and to listen it. I head that 2A3 were made as IDHT (dual) - I wonder if someone one them. Anyhow, I will keep my mind open and perhaps someone would impress me with DHT. Some folks told the foresails about the A1 triodes but looking at what else they those peoples did it more impact me with apologetic feelings then with desire to demonstrate any attention to their foresails …

Anyhow, if some one would bring in my room your serious and full of objections SET (driver AND output should be DHT) then it might be educational…. perhaps for both of us…..

Yes, it was kind of interesting. The Tentlabs site does not have anymore those popups (and my machines are environmentally clean). I was so surprised when I sow it that I even went to their web site from my “absolutely clean “server that never ever goes Internet. Anyhow it is not so relevant

What is really interesting if does exist any sonic difference between DHT and IDHT. There is difference between different tubes and between different productions. Would this difference between different tubes more visible then the difference between DHT and IDHT construction? I really do not know. The engineers suggest about some essential advantage of one of other construction but it says a little to me about Sound. I as well have seen and heard plenty of crappy sounding DHT, frankly speaking in most of the cases I head poor sound and I did nit even care to learn what tubes were used. I generally have tendency to express interest only if the result was worthy and I do not accumulate needless audio knowledge.

It would be fun to see some kind of DHT devotee who knows what he does and who can demonstrate the boundary of DHT application. There are a lot of people who make noise about the subject but I never was exposed to anything convincing.  If I have some semi-local serious guy with noble DHT objectives than I might supply him with some interesting tubes. Approximately 8 years ago I bought in German, practically for nothing, a collection of 50-60 tubes; mostly pulls form German radios of 30s. I found it recently in my storage in and I think it might be used somehow. I do not need any amplifiers for myself but if someone is capable and serious about their objective then I would furnish the person with some interesting tubes. As the payback would like be able to learn with results. I know… it is all utopia but if I do not make somebody do the things then I know that I will not be doing it myself....

If you look among the links of my site then you would see the Netherland's Rob who is deep into the direct heating.

http://www.dhtrob.com/index_en.htm

It would be fun to have someone of his level of craziness to demonstrate what direct heating could offer, if any. Some of the things (not all of them) that Rog says at his sute I do appreciate…

Well, I least of what “be” proposed is true then it opens up a whole new perspective of thinking.

So, toward this end, since in DHT the filaments are cathodes we could intentionally stress the filaments and by doing it what could inflict sound. Sure it would wary with the way how filaments hanged and particularly since they are heated equally across the whole length, but still…

No question in my mind that the tubes themselves contribute to the sound we get from tube-based systems.  Funny how I go to such lengths to get "quiet" tubes and use dampers even as I realize that even the quietest tubes are doing their bit to/for the end product.

But surely this tube noise is a matter of degree?  For instance, I once owned the original Music Reference RM-9, which could use EL-34 variants, KT-88 variants or 6550 variants.  Not only were there plenty of differences between the tube "families", but there were also similarities between members of the same "family" that did not seem to be "electrical" so much as "mechanical".  Germane to this discussion, I found the very popular KT-88s to be flat-out too noisy, although other listeners "preferred" the "richer and more immediate/lively" sound.  Likewise with AC powered filaments in some set-ups, where the noise just over rode the other pleasant "effects" for me.  Shades of the "lively" TT set-up... 

Back to the "oops" theory, I suppose, along with all the other "problems" we encounter.  How can we use them to our advantage...

Best regards,
Paul S

Merlin wrote:

Directly heated triodes …. It has fully regulated power supplies and absolutely zero AC filament hum.

That bothers me tremendously is the half-ass approach of high-end products and the fact that for exuberant amount of money, that looks like should assure ambitions solutions and objective methods, the high-end companies still do not go all the way into what is possible of at least available for a premium high-end pay.

For instance everyone knows that DHT sound way more interesting if the filaments are AC driven. To drive them AC requires quite expensive super-precisely symmetric in capacitance and impedance domain transformers. So, Lamm made his ML3 SET with direct-heated GM70 but the amp has use DC in filaments. Sure, it makes the amp “secure” regarding the filament noise but… can something bold and ambitions implementation-wise could be asked form an amp with $125K price tag? If not to demand from those products the “high-end implementations” then from which products it should be asked?

This subject does not bother me too aggressively as I recognize absolutely no sonic demands or listening temptations to change anything in my playback. However, there is a theoretical and conceptual curiosity on my part and I would like to learn what a good direct-heated triode would do in regard to my single 6E6P stage driving MF channel.

I would like to have a good 1W-5W direct-heated SET that was educated to sound right by its owner and to connect it to MF channel of Macondo (15R), I would like to see what it might lead. So, if any of you New Englanders have a good sounding direct-heated SET then feel free to contact me and perhaps we can do a listening session together with your SET and my Macodno’s MF channel. From my side, as the reimbursement for your efforts dragging you amp in my place, I might promise you an educational experience about sound that you most like will not get otherwise.