A few days back I posted the following post:

http://www.goodsoundclub.com/GetPost.aspx?PostID=8922

…proposing the parties of interest to play along in Milq vs. DHT competition. This interst derives from the following thread:

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=6317

…where I told that to DHT for Macondo MF channel only might be something that I would try sometime in future.

I have to admit that I a not well-familiar with DHT. I lost my exposed to various amplifiers in 2000 when Lamm ML2.0 entered my room, ML2.0 usually does it to people. I did try something before but then I had a very different criteria then I would have nowadays. Since 2000 I deal with various people and amplifiers who were deep into DHT believing but to the best of my experience with them they did not clearly realized what kind sound I deal with and what audio results I was targeting. This pretty much closed up any door to get any answer for Melquiades vs. DHT inquire and leave the only opportunity to find an answer myself.  I do not want to build DHT and here is where I proposed to open my door for a serious DHT person to make the appraisal of DTH vs. Melquiades sound together.

One, and probably the only one interest that I have in DHT is to research if it possible to get more sophisticated “Absolute Tone” for my MF driver, of the tone from the amp generally.  It is reported by many DH people that DHT from 30s-50s have more interesting tone then IDHT tubes of later production. I personally do not know if it is the case. It might be true or it might be just pure ignorance or Moronity of many DTH builders. I have seen a lot of DHT amps when even a person with very limited technical expertise like me was insulted with absolute idiocy of design decisions.  All those Loftin-Whites with 12AX7 in input, with SRPP in driver stage, with huge cap sitting at driver’s cathode…Please!!!

My primary interest is in 2A3, 45, V52, A2 and few other tubes of that period. I would like also to see a DHT probably, or at least interesting designed and built, most of them are not. My definition of interesting designed would be 2 stages only, with no coupling capacitor (actually, since it will not do bass anyhow I would prefer it to be direct-coupled), with both cathodes on ground. I did not see anybody is trying the DHT like this and it is sad in my view.

BTW, if any of my local New Englanders who might use 2W DSET, wiling to build it and would like to try something “really pushy” then Dima and I came up with a very interesting model of DHT that looks like never was tried.  It is pretty much direct-coupled 2 stages with grounded cathodes… but DC stable. I might divulge the idea and assist with building in exchange for the promise that the build amp will be lent to me for a few days to try how it sound. Let call it the “Real DHT”

I do have my prediction that a single stage 6E6P, in a way how it is done in 6-ch Milq, will overcome any competitive DHT in context of minimum bandwidth of my MF channel.  Tone-wise, however I would not make a prediction as I do not know. DHT might have or might not have a tone advantage but how it might or might not be compromised by the specifics of a given DHT design no one knows. That is why I find the “Real DHT” idea is fascinating it has no capacitors in grid or cathode, and I would say that arguably not even in PS. So, it might be the true methodologically proper test of DHT tone.

drdna wrote:

But how can you make the Melquiades as a DHT amplifier? I do not see it.

To make Melquiades as DHT is very simple juts use DHT output tube. However, if DHT idea does make sense then I think the diver shell be DHT as well. So, the DHT initiative does not comply with Milq and in the core of Milq is IDHT, OK, the triode strapped IDH tetrode.

drdna wrote:

But otherwise you will be comparing the tonal characteristics of just different topologies and parts, not comparing DHT to IDHT.

Yes, it is the problem. This is why I do not intend to compare DHT to IDHT but rather to see if I will be able to get anything “extra” with off the self IDHT solutions.

drdna wrote:

If this is the objective, then I think you have done it before with other DHT amplifiers, yes? And I think we know your opinion of Gizmo and Sakuma-san.

I do not have any opinion about Gizmo, I never was impressed with him pushing OTL but otherwise I know very little what he did or say. I read a few his articles and I did not understood what he was trying to say. I do not like what Sakuma-san does.  About my objective, I am not sure as I do not look for any particularly new sound and I am comfortable with current result. I just would like to learn is any other tonal doe is available out there.

BTW, I have a local Bostonian guy have replied brought today a very interesting DHT amp.  He has a number of DHTs and this one he reports is the special one, quite expensive as well.  Although the electricity was not good today but we did some listening and the results were very quite interesting. I am still contemplating about them and will post what I think what I have more organized thoughts.

Romy the Cat wrote:

I have a local Bostonian guy have replied brought today a very interesting DHT amp. He has a number of DHTs and this one he reports is the special one, quite expensive as well.  Although the electricity was not good today but we did some listening and the results were very quite interesting. I am still contemplating about them and will post what I think what I have more organized thoughts.

I could not say if/how very high speaker efficiency and/or FR limiting might effect the issue of a sort of "shuffling" of pitch/tone/harmonics as SPL and complexity shoot up and down, ie, tonal integrity versus dynamics.  No amp in my experience has seriously rivaled the ML2 in this respect, and no other amp known to me holds its "harmonic center" along with the "surrounding territory" so tenaciously.  But you know the price for this...

Again, I always had the feeling that I was using the small DHTs wrongly - that there was more There there than I was getting with my own implementations.  OTOH, I never heard anyone else get it just right, either.  There must be a way to "hold the fort" without feedback.  Mustn't there?

Paul S

First of all it was quite interesting and quite educational. Second of all it answers no questions but rather creates more questions. Here is what I try to compile some my observations and thoughts on the subject.

I have a local guy who red my site and   who in response to my “DHT Challenge” got in touch with me and proposed to try his amp. He is well-familiar with DHT, owns a few of them (45, 2A3, 300B) and proposed me to bring to me any of amps DHT amps he owns. I proposed to him to choose an amp that he liked the most. His feeling was that one of his 300B amps was the most interning. He noted that he doesn’t like mach 300B amps but according to him this one has something special in sound that he very much appreciates. 

There are few things shell be addressed. I do not know this guy, I never heard his playback and I have very limited or any ideas what he is doing or trying to do in audio.  Those few hours that we spent together characterized him as lucid and coherent person, even though completely dead musically.  What however I did appreciate in his was his complete absence of that idiotic audiophile pride of ownership. The audio idiots usually are accustom to bind accomplishments and failures in audio with something “imaginary more important” and they go extremely personally about audio judgments. This guy seemingly was not exposed to this idiotic plague and he was not personally wasted in all of it. His attitude was: let see what happen – my type of guy. Furthermore, since he knew that I might mention our experiment at my site he asked to keep the identity of his amp private. All that I will say that it is slightly altered version of a commercial amp with 300B in output, that it come from a brand that I do not particularly like, and that the amp’s retail sticker is a few tens thousands dollars – it is very expensive amp, and according to the amp owner “it is not just another 300B but the best they were able to do for 30 years”.

In order to give an idea about the amp generals outlook but hide the identity I would say that the driver/s of the amps might be fine in here:

http://www.westernelectric.com/support/we_spec_sheets.html

I will not say more to identify the amp. My expectations were very low and I did expect that Milq will eat this 300B alive. From certain perspective it was what happened. There is another perspective however…

Initially I did some Moronic listening of my MF channel driver by DHT vs. Milq when I just forgot that my Milq have built-in filters inside. I am so accustomed that my amps have all inside that is necessary to drive the channel that I was driving MY OPEN DRIVERS with this DHT, getting horrible sound, and pontificating that it “sounds like a typical 300B crap”. I kid you not.  Then I concluded that that this DHT is just broken and suggest to puck this hit up I did not believe that such a huge sum of money might be asked for this amps that has sounds more horrible then a cheap portable AM radio from 70x. I way much beyond what I expected. Then, while we were packing the DHT, it suddenly come to me that I was an idiot and that I just forgot a need to use a speaker filter the DHT’s output!

I was laughing on myself and I made a break. When I got back home I put 3uF cap after DHT amp and tried it again. It was of course a different story and the DHT had something more or less contestable. Contestable but not truly sound acceptable in my view as the DHT amp had very dry and grainy sound with some very-very heavy and very annoying me “throaty” colorations.   I keep playing it, doing something else, as I had no more interest in this sound. But as time goes by I noticed that the “throaty” colorations were subsiding and the amps literally before my eye was self-transforming, like those dues in “The Transformers “movie. In half hour I went back to my listening spot and to my big surprise the DHT sounded just wonderful, with no signs of irritating throaty colorations, very nicely balanced dynamically, tonally and hydration-wise if you insist. Ok, now the game is on, I figured.

I spent some time listening the sound of this DHT amp driving my MF channel, then Milq’s single stage driving my MF channel, then DHT driving full range my Injection Channel and then a full-range Melquiades driving my Injection Channel, the amp “C” on the circuit below:

http://www.goodsoundclub.com/PDF/6-Chennal_Melquiades_DSET_Amplifier.pdf

There were some educational for myself observations made, in some way saying something about this specific DHT and in some way saying something about Melquiades’ single stage version and the Melquiades’ full-range two-stages version. Differences were very clean. The heads off to this DHT amp, I do not know if it was a good DHT of bad one but it was superbly instrumental in what I was looking. I will pass my observations and interpretation of the results in the second section “My DHT experiment: Observations”, I will right it most like later on this week when I have time. It will be then the third section “My DHT experiment: Concussion”. I am not ready to say that this section is formed in my head, I still thinking about it but I have already some in my view very interesting and stimulating ideas. Stand by if you are curios.

Romy the Cat wrote:

There were some educational for myself observations made, in some way saying something about this specific DHT, in some way saying something about Melquiades’ single stage version and the Melquiades’ full-range two-stages version. Differences were very clean. The heads off to this DHT amp, I do not know if it was a good DHT of bad one but it was superbly instrumental in what I was looking. I will pass my observations and interpretation of the results in the second section “My DHT experiment: Observations”, I will right it most like later on this week …”

I will not make any concussions in this section; I will lea it for the last section of my “DHT experiment” journal.  In this section I would like to describe my listening impression during my Milq vs. DHT contest.

Remind you that I used two types of Milq: single stage and full range two-stages. The single-stage Milq was driving a single 15R Vitavox S2 with own RL-line level filter at 3200Hz. The full range Milq was driving Tannoy RED in custom enclosure with original RED’s speaker-level filters. The DHT amp was driving  Vitavox with a speaker-level 3uF filter and then driving the REDs with the same Tannoy’s speaker-level filters. The DHT was well-burned in before listening; otherwise it was out of the scope of any acceptance. The Milq was hot for hours, it was on weekend and my amps are mostly always on during weekends, if it is not summer…

I was running Milq single-stage into S2. I know this sound; it was my “default” “In Macondo” sound, the one that I know very well.  I set the reference volume level on my RTA using my TU-1X’s internal generator. Then I switch to DHT amps to drive my S2 driver and matched the volume my RTA. I wanted to keep the “competition” as clean and possible, at least what I thought…

The sound is different from Milq and DHT. The Milq is more dynamic. OK, not just more dynamic but rather hugely more dynamic. Milq has more contrast, more rhythm, and had more LF articulation if the LF were called upon (and it is in context of 3200Hz high-pass filter). He sound from the Milq was way cleaner and Milq was running across dynamic range with much faster speed and willingness.  Milq had way more extended and way more sophisticated HF. The transient characteristics were not even contestable as the DHT had almost lethargic transients with quite bleary articulation of details.  I would say that the immediate switching between the amps left very little change for DHT, at least at the first level of listening perception.

There was in DHT some positive moments. The Milq was a high-quality performer but it was musically-balanced ONLY in context of the rest Macondo’s channels. The single-stage Milq itself (without the support of other channels) was rather “quality pushing devise” and was in a way over-hygienic. It might be said that it was what Joe Roberts called “painful accuracy” - it had a phenomenal sounds quality, in away hi-fi quality, but it not so smoothly “compiled” along with the flow of Sound, it rather pushed the sound forward. It did not diced and sliced the sound as it was harmonically balanced but right from proper harmonic flow it has a tendency to jump with a bite quite devastatingly. The DHT amp in this over MF only configuration was more balanced, even though less radical and less far-reaching.  I have to admit that with my Vitavox S2 driver from 3.5K and up and driven without other Macondo’s supporting channels sounded more interesting wit this DHT 300B amp. (The last time I heard 300B driving S2 it was with Cary 300B amp and it was a nightmare). 

Considering what I said in the above paragraph and what I will say in the next paragraph (about the respectful loading) would it make sense to presume that the DHT driving my MF was better then a single-stage Milq. Well, it is a bit more complicated then this. The negative moment of Milq driving S2 and the DHT driving the S2 I described but they are binary differences without any regards to anything else. They are just differences but they are not Sound yet. The DHT and Milq did not have differences per se but rather those amps were concentrated upon different way to treat phonetics of sonic language.  Melquiades was about clarity of vowels and tension of consonants. It made Italian soft and fluent, Arabic - harsh, German - barking, Russian - broken up, Spanish – meowing, English – overly logical. The DHT was about murky vowels and smooth consonants. It made Italian oily, Arabic-smooth, German- singable and fluent, Russian- palatable, Spanish- royal, the English’s of Allen Ginsberg it made almost like William Shakespeare. So, the amps did different service and had even different objective. I have to also add that putting the MF channel driven by Milq or by DHT into the play with the rest of Macondo (were the MF is injected with REDs) made the assessment VERY difficult. I did not have time to pay more attention listening the drivers fully incorporated with Macondo. Frankly I did not have much intention to do it. Read up the next 2 paragraphs why.

Listening those things back and forth it was very clearly that my Milq and DTH were respectfully differently loaded. It sounded like DHT has more second harmonics. Milq was loaded in context of the sound that I need to get from Vitavox S2 in respect to the rest of Macondo (1kOh of 6E6P plate, 15:1 transformer and 15R driver). This is a quite heavy load and S2 is this configuration is quite heavily damped:  this how I deal with S2’s intrinsic resonances about 9kHz (I wrote about this in the there what I was fighting with S2). The one-stage Milq is sufficiently damped, however this Milq’s MF channel is “built for speed”.  One stage uses RL filter, very fast RF tube and low inductance transformer with very fast amorphous core.  It has a feeling that it fast and contrasty, but NOT harmonically deficient Sound. Vitavox is not Altec and I do not to need to unload the anodes all the way in order to make my MF channel to sound “exiting”. It might have higher order of 3rd harmonics then DHT but I do not measure harmonics, instead I rather try to learn how to hear and to understand the things. So, I subjectively do not feel that single-stage Milq and S2 driver are sound inappropriately together.  The Milq is DSET and it works in own, much-optimized for HF environment. The DTH is not DSET and it is even not near in the same HF-optimized environment – it sounds more liturgical, sleepy and very much NOT fast. Was it loading due to loading? If I had time I would remap the sections on my Milq transformer and change the load to have harmonics to match DHT. The DHT had only one tap, so there is no ways for me to do anything (it might have internal taps but I did not open it up). I shunted my S2 driver with 12R resistor, effectively loading my 6E6P harder. This method is not the same as the properly loading a plate with active load but I know how this “half-ass trick” sounds and might to a degree to extrapolate the result. I also played with plate currant on the Milq’s single-stage. It insignificantly changed some degrees of differences but the basic still was there – the DTH was just a bit too sluggish with some lack of something that I would call cleanliness, precession, articulation, granularity and exactness …and it is with very fast and high transients-compliance driver of high impedance, the impedance that shell idle the 300B quite nicely.

OK, was what I did a methodologically-kosher way to facilitate the DHT vs. IDHT observation? Well, it was not.

In my view the amps did not work in the same conditions. The DHT and IDHT amps SHELL BE IDENTICALLY LOADED IN SUBJECTIVE EQUIVALENT OF RESPECTFUL TO OWN TOPOLOGY HARMONIC TEXTURE.  (This is VERY loaded statement as the recalculation of ratio and plate impedances very much might not be enough to harmonically match DHT and IDHT amps).  It means that the DHT vs. IDHT shell to output into the same speaker, measured by the same microphone, plotted by the same analyzer and then gauged approximately the same harmonic texture. If we “compare” the differently-loaded amp then do we really compare DH cathodes vs. IDH cathodes or we just compare a zillion other reasons that impact sound? Talking about the reasons: the RL line-level Milq filter vs. a cap at speaker level, the Dominis cable vs. the 2M litz cable, the single-stage IDHT with grounded cathode vs. a large 3-stages DHT intentionally designed to have specific “pre-sold”  character of sound…. I mean: we do not compare the DHT vs. IDHT rather we compare one amp in random conditions to another amp in random conditions – now intelligent and how indicative is it? In this situation one amp might demonstrate itself better or worse but it says nothing about the rivalry between DHT and IDHT amps…

I need also to add that with more neutral speakers then S2 the result was predicable: when I was running my full-range Milq and full-range DHT against the very much not neutral Tannoy Red then DHT produced a lot of very poisoned colorations.

OK, from what I said it is clear that the DHT worse and out of the competition? Well not really, in fact with all negativity that I recognize belongs this amp in context of my S2 driver I need to say that I actually liked this DHT amp and if I did not have my DSET expectations then for a full-range operation I found the DHT was more reasonable with my MF driver, even despite of the above-mentioned shortcomings. To use it would require idling the 300B 2-4 times more that would leave juts 2-3 usable watts. Still, I do not think that I would live with those shortcomings, I would rather to DEAL WITH THEM in order to get the best from each amp or topology; I will talk about the Conclusions later on, in the Third Section of my DHT exploration….

Looking at my comments it is important is to understand the scope of my inquiry. When I said that this DHT was “superbly instrumental in what I was looking” I meant that I was not looking for “better amp” but rather for an opportunity for a DHT to show me something else that I do not get from my Milq. Did this DHT amp show anything “interning” to me? Oh, yes! It was a few things that made to think.

A very interesting characteristic of this DHT was not the amount of second harmonics but rather their colorations.  Loading anodes and increase of second harmonics makes the second harmonic more domains but does not change the color saturation of the harmonics. With Tannoy Red this DHT had purely syrupy sound but with my MF S2 driver it was very colorful and the colorfulness was not as much annoying. The S2 is very fast, very contrasty itself, superbly articulate and color-wire is it very neutral - it worked very well with this DHT amp’s colors saturation. The S2 driver with Milq was colors-wise on a “save side”, neutral and impartial, but with DHI it was although slower and less dynamic but at the same time more colorfully-flamboyant. This flamboyantness had some colorizing common denominator that I did not liked but it was still educational, practically knowing that S2 is the most color-articulate compression driver out there. I listened it very short time (which usually is perfectly enough for me) and I got feeling that the wildness of this DHT coloration (in positive way of using the word “coloration”) was pleasantly-high but at the same time it appeared to me that this amplifier was not able play gray, black and white colors. The absolute color was perfect but the relative colors were … colored.  However, the fact that a “clean” driver might be colored by DHT (or whatever coloring method the amp used inside) was very worth paying attention and it is one of the moments upon which I will capitalize in my further Conclusions. Paying tribute to wonderful DHT color potency I am not sure that this would please me on the long run. I like if music is gray then it to be played gray via playback, if the music cold then to the playback shell have it cold and if an  instrumentalist or his/her playing are crap then I would like to have it to sound like crap via my playback. I did felt the DHT color grandeur but I a bit afraid if DHT is able to play colorfully without taking sides. Also, running the S2 “injected” buy Reds along with the rest Macondo completely removed any DHT’s color advantage. I have some futher idea/directions about it that I will propose in the “conclusions”

There was however a characteristic of this DHT’s Sound that I loved without any concerns, second thoughts and that completely eclipsed my amp: this DHT amp has more random pace and more random texture accents then Melquiades. The DHT had less articulated pace and less defined texture then Milq but the UNSYSTEMATIC AND CHAOTIC NATURE of its timing was truly phenomenal. It is hard to explain in audio terms – you need to look for it in order to see it. What kind association I can give to you to illustrate what I mean? Let look at two great paints:  Byron Janis and Josef Hofmann. Janis, in is best time, was wonderful and in many ways his micro-timing of notes opening was exemplary. Everything Janis did was in great respect to reasons, taste and intentions - it was truly perfect. Then there was Hofmann.  Hofmann’s timing of notes opening (when he was in his mid 20s-30s) was against all lows of physics, against all measure of time and … space. Hofmann hit the keys in his own manner and very frequently a few milliseconds after of before it was expected from a perspective of the “rules” and “logic” for a given piece of music. It was not even milliseconds but rather the Hofmann’s own curvature of time. These micro-timing presumably (very loaded word) random differences between Hofmann’s timing and listener’s recomposing consciousness, that seems like a randomness of micro-events deeply imbedded into the hugely organized flow of musical ideas  did swing listener’s mind with a force of good size hurricane. Here is where Janis was one of the greatest pianists on his generation but Hofmann was a pinnacle upon which all greatest are measured.  So, Melquiades has its perfect timing and perfect pace. Milq is not a damn machine but it is a sensitive, smart and responsive mechanism that is perfection itself.  The level of “timing” perfection with Milq is unquestionable, it is the Horowitz plays Schumman’s Seventh Toccata, - it is what the right sensitive timing and right susceptible balance is about. This DHT take it a step further – it introduced own sense of randomness about that timing perfection. It is where Hofmann with his expressed “unpredictability” reigned supreme and it is where this direct-heated amplifier in my view destroyed my Melquiades. If I was able to fight with some DHT tonal saturation with my Injection channel then I had no tool in my disposal to make Milq to have more RANDOM pace

The next last section of my little “DHT field trip” I will try to share some my conclusion about all of it and will indicate where my thinking is in respect to the DHT subject.

drdna wrote:

However, there is something to be said for the certain magic that can sometimes happen with a particular device. The unpredictable transients and color shades add a sense of alive-ness that seems separate from the standard characteristics we use to describe the audio.

Well, perhaps. A few 300B amps that heard did not have “magic” but they rather had array problems. Perhaps a 300B amp (or alike) used in a limited bandwidth in DSET configuration is something that might be worth to explore? I did like the 2 above mentioned moments I would not accept the limitations that also described above. The shades  of color are fine but the shell be the shades  of “right colors”, not the shades of the same colors. It is interesting if anyone does the DSET oriented DHT, perhaps with the same 300B?  It would be fun to try a 2-stage, grounded cathodes 300B amp with DSET out transformer.

drdna wrote:

Perhaps now you understand a little more my point of view that an audio device can have clear limitations in the first level of audio perception but can still have a greater ability on an emotional level to allow the listener to connect to the Sound?

I still would like to maintain my loyalty of the notion of sequential levels. If we have a “successes” at the Third emotional Level and then we increase the amplitude of “successes” as First static Level then can we presume that the “result” at Third Level might be “better”?

drdna wrote:

It is a little confusing to me, since I had originally believed that the Melquiades circuit was intended to do exactly that. Perhaps I misunderstood all this time...

I do not understand what you are saying, Adrian. The Melquiades circuit of the single-stage amp was not intended to do anything in terms of “color”.  Take a look at the MF channel “C”:

http://www.goodsoundclub.com/PDF/6-Chennal_Melquiades_DSET_Amplifier.pdf

There are no parts in the signal path- the PS, a bias resistor in grid, a tube and transformer – it’s it. There is as little “circuit” in the single-stage Milq.  My primary interest at this point is to learn if the positive things that I notice were due to the 300B or it was the amp itself. You see, the amp was made to be very much not neutral. As far as I know this manufacturer they intentionally push out of this products very specific and highly colored character. I have see their units in past and I very much do not agree with what they do. Perhaps we do use different lingo when we talk about DHT’s color and IDHT’s colors. I have seen people who advocate DHT and we all heard their arguments. I was not impressed from what I witnessed. Like anything else in audio it might be endless mouth running about it but in the end of the day the people shell talks about the mutually experienced actual results. They shell be in the same room, experience the same sound form the same playback and then correlate the observations. Then some kind of common denominator of assessments might be built up. I did have in my room a number of DHT people of various level of understanding about sound and among other my questions about problem with my playback I always ask my visitors to comment about the quality of tone. I never had people complain even if did not like it. I personally do not feel any “shades of color” deficiency with my MF channel. I however would like to be challenged and proved that I am wrong.  I have some idea about the subject that I will share in my next “conclusion” section. If you find yourself in Boston then drop by and we would have some tangible ground for interpret of the actual result. We could borrow some kind 300B for fun…

Romy the Cat wrote:

UNSYSTEMATIC AND CHAOTIC NATURE of the DHT timing was truly phenomenal.

Ok, I do not know what it was: was it DHT, was it 300B, was it some other specifics of this given amp or whatever… but those two aspects that I named: intentional density of colors and randomness of pace are something that I would like to exercise in my playback. However, I am not one of those who give away a store and I have no interests to lose what I have accomplished (like superb clarity, cleanness, dynamic, articulation without “resolution” etc) and recognize as my Macondo’s current virtues in order to pursue for what DHT might (or might not) add to it. In case of the density of colors it means that would not mind to sprinkle some additional color upon the sound of my MF driver but I disagree to lose anything in the driver’s contrast, color impartiality, tonal discrimination, dynamic discrimination, transients, speed and energetic willingness.

So, what I am talking about is ability for an amp to have some kind of inner-algorithm that dynamically and actively “color” or better to say “dye” signals, still maintaining general color-neutral tendencies.  Since I kind of formulate this concept in my head I would like to name it and will refer it in future as Active Pigmentation. The Active Pigmentation implies that a channel expresses a slightly over-saturated tone but only under as a specific dynamic or pitch conditions. The depth and the conditions of the saturation shell be manageable. The readers who read my site carefully would ask: “Romy, are you talking about the idea of Macondo’s Injection channel only by electronics means. The answer is “Exactly!” Let submerge together into the insane world of deep-core audio drilling…

Pretend we have an abstractedly-neutral and high-performing, clean channel (let for a cause of illustration it to be S2) driven by a neutral and high-performing amp (let for sake of illustration call it single-stage Milq). Now, how can I inflict the Active Pigmentation of the Milq sound particularly if the amps like Milq have no parts in it? Even if it had then the passive parts would proves only static and hardly manageable coloration – I need Active and controlled coloration. Well, the solution might sound idiotic but no more idiotic then the idea of my Macondo’s Injection Channel. Still whoever had the experience how I implemented the Injection had no downs that it is not just works but works astoundingly well.

So, what I propose? Well, it is not what I propose but rather the idea was born when Dima and I discussed the results of my DHT trip.  I was asking about design of harmonic correction circuits and was inquiring if it is possible to inflict by will the specific coloration to the specific harmonics. We were thinking about different methods and then Dima asked: if to run a DHT in parallel with Milq, mixing their currents, then what would happen?

OK, let go from here. How about to put right on the Melq’s MF anode supply another tube running it in parallel with Milq’s tube, let call it the Injection Tube. This Injection Tube is some kind of DHT similar to 10Y, 24, 27, 45, 50, VT-25, 2A3, 6B4G, 300B, AD1, AZ1, 6A3, 210T and alike. Furthermore the DHT in voltage starvation mode, uses heavy colored coiled cathode bias and has operating point that yields a lot of distortions and a lot of colorations. A resistor in cathode is adjusted to regulate the plate current and to drive the B+ hungry tube even deeper into colorations. The signal of the Injection Tube is driven across the same output transformer but at much lower current. Let say the main Milq’s tube push 30mA and the Injection Tube pumps 5mA. Adjusting the balance between the Main Tube current and the Injection Tube current it is possible (???) to moderate the necessary Pigmentations. What I outlined is just a concept not the model to follow. If it works then the currents of Main and Injecting tube might be mixed by many different ways: with own DHT transformer at speaker level, with dedicated separate coil on the main output transformer or by many other ways. It might be even fun to drive the cathode resistor of injection tube with some kind of reversed feedback from the main amp. The main tube will serve the main “shape” of the sound and the injection tube presumable will add the right amount of MSG to total sound.

What I describe not what I am trying to do but I am thinking about it. I need some kind of very colored DHT tube or perhaps some kind of other method to crate my active “electronics syrup dispenser”. I consulted with a number of DHT minded people and they all feel that they know how to get out of their DHT the “neutral sound” but they are not sure what DHT would be the most “colored”. I presume that by barbarically starving the tube all of them turn into Tannoy Red (also the lower voltage will make the expensive vintage tube to live forever). Still, I would need some consulting from outside by somebody who played with objectives of non-neutral amplification or with sound effects made by analog means. Ok, it was what I was thinking about the DHT’s density of colors. What I am thinking might be a bit awkward from a perspective of common audio wisdom and it is possible that it might not work, or course more problems than solutions. Still, I find this direction is very much worth to explore. If somebody who has ears, brain, is comfortable with tube designs and would play with ideas of Active Pigmentation then please let me know about your findings as at this point it is not at my radars. As far as the pace randomness - I have no definitive thoughts. It might be the specifics of the given DHT amp, might be the amps power supplies or the specifics of this amp’s drivers. That DHT amp that I had used feedback, perhaps some specific aspects of the feedback application made it happen. I do not know and I continue to think about it. If someone has any proposals where the DHT randomness come from then let me to hear them.

There is an alternative thinking – why not to put in the 6-ch Melquiades one more channel with DHT and to drive with it my MF driver. It might be possible that being implemented “better” and properly loaded the same 300B for instance will not eat dynamic and articulation and will sound “clean”. Ironically the idea to add a DHT section to Milq it very simple to execute. I do have a good spot for the DHT tube: right atop of the amp (I put there now one more 6C33C)

This is very good location as if has no limitation for heat dissipation and the MF output transformer is right there under the top cover

The Milq has inside the chasses a good quality 400VDC and 200VDC and to suck more plate current for DHT would not be a problem. The single-stage 6E6P of the MF channel will become a driver but instead of driving the output transformer it will drive the DHT tube. The Milq has inside bias voltage and anything else that is necessary. There are two types of DHT – with amplification of 7-8 and 4K-7K of plate impedance and those that have sub 1000R plate impedance and amplification factor of 3-4. If I use the second type then I might use my current 15:1 output transformer from 6E6P, at least for start.  All that I would need is a little filament transformer with a center tap to drive the DHT or even do not do it and to burn the extra voltage of 6C33C heater in power resistors. This might be a very simple modification and theoretically if to have a good quality 10-poll switch then it is possible to make the MF channel switchable even in real time from single-stage 6E6P operation to a two-stage DHT operation. The entire Milq MF DHT channel might be look like this in case a IDH driver was used:

So, do I consider doing it? At this point not. You see, I do not really know if I might need it in term of a practical result. Reading my comments in the “Observations” post and my comments about the ”differences” when the amps drive the MF driver only one might think that the ”differences” are observable via the sound of the whole Macondo. Well, I am not sure about it. What now Milq and Macondo do is good in my view, and I do not experience a need to change it even though I did acknowledged the ”differences”. If I need to do anything is to learn if the DHT’s differences would be tangibly beneficial just for MF driver and in context of the whole Macondo Acoustic System. To learn it I would need a PROPERLY-made DHT amp (without all stupid tricks of static colorations) where I would have a chance to play with loading, damping, perhaps the core of the output transformer,  currents , the character of sound and where I would make sure that the MF does what I need it to do. Macondo is not a full-range driver and all aspects of Macondo ingredients shell be thought together. I have a failed Melquiades for headphone amp that I might easily retrofeed with second DHT stage. I do have also some OPT what I might try. All that I need to buy the DHT tube and the tube socket. I might also run the test from my lab power supply; I have a very cool old whole tube Fluke 709D.  Perhaps I will do but I would need more encouragement that it might make sense and would not lead just to another stupid DIY project but rather to a sensible improvement of sound. When for a very short time I connected this DHT that I have last weekend to MF channel and ran it along with the rest of Macondo honestly did not see any needs for me to change anything. It was very short and I might be wrong. Perhaps another DHT amp will come my way and I might study this subject deeper.

I did have an educational and thoughts provoking experience with this DHT journey. I do not think that the exploration of this subject is over. Let see what future will bring.

drdna wrote:

You had described the Melquiades as a "reality Reconstruction" amplifier. In my mind, I have always associated the unpredictable quality you describe with a "closer to reality" sound in my system.

Well, I might describe Melquiades as whatever I want and label it with anything I want. I am comfortable with my descriptions and labeling. The whole point for people to collaborate the Reality Reconstruction effects is to have commons tool with common effects. I made Melquiades publicly available that enables others to browse and to experience my version. If you wish you might build Milq and to observe how much closer or further I am with Melquiades. I do not take this subject as ego trip but rather as an opportunity to evaluate what is worthy to do. As far as “unsystematic and chaotic nature of the amp’s timing”, Adrian, it was not in epicenter of my attention. You might always associate the unpredictable quality of your playback as closer to reality but with all honesty over the years of doing audio and talking with many different people  I never heard anybody comment about randomness of pace and I never heard anybody recognize it publicly as a virtue.  The randomness of timing might be a new good thing that I might need to pay attention, or might not be. I do not know at this point. I heard a number of 300B amps and I never had the same positive expires with unsystematic nature of sound as I had with this last week amp. It is might be what your 300B does or it might be not even relevant to DHT amp at all as do not forget the NO ONE ever among the DHT community spoke about the randomacity of timing (at least I never heard). Who knows it might be that specific topology of power supple is something that randomizes the amp’s texture, like half-period tube rectification or something like this… In such case it will not be related to 300B or DHT at all.

Anyhow, the Melquiades does have some “tricks” in the realm of dynamic viscosity. It is what make it quite different in term of Reality Reconstruction as I feel that propagation of sound via air does not have linear “audio dynamic”, soft of speaking. If the randomness of time is a next thing that I would attribute as necessary characteristic in Reality Reconstruction then I will tech my amp to have it. At this point I am enthusiastic about the timing randomness but it need to be settled down, interpreted and extrapolates in some kind of electronics-viable format. As I said in my post above – I like the effect but I am not giving up anything else for it as in my view “Reality Reconstruction” is a presses not a functionality.

drdna wrote:

It is not enough that the stereo neither adds nor subtracts colors or signal.

This is a bit more complicated as we always shell ask what is the original “colors”. The colors of signal? The colors of live sound. The colors of composed-in intentions? The colors we would like to hear in context of our expectations? Ok let make it a bit more complicated (be advice that it is “loaded”): The colors we would like to hear in context of our realizations? I do not think that anybody would argue that Vincent van Gogh’s colors were very realistic in context of his intentions and in context of his methods of expressivity.

drdna wrote:

In the same way it is not enough for a window to have perfectly smooth glass surface or the paint exactly on the pane, not on the glass at all. I use the window to see through to the outside. I use the stereo to heard the Sound.

I sounds like a comfortable and popular audio association but I think it is a self-deception.  I would disagree that we use a window to see through to the outside. If we are willing to see outside then we go outside and see what we see. If we intend to look at the outside through the window then we intentionally engaged window into our perception of what is outside. Therefore the window frame and the characteristics of glass are also the filters of our perception about the outside world.

Romy the Cat wrote:

So, what I am talking about is ability for an amp to have some kind of inner-algorithm that dynamically and actively “color” or better to say “dye” signals, still maintaining general color-neutral tendencies.  Since I kind of formulate this concept in my head I would like to name it and will refer it in future as Active Pigmentation.

Romy the Cat wrote:

Anyhow, the Melquiades does have some “tricks” in the realm of dynamic viscosity. It is what make it quite different in term of Reality Reconstruction as I feel that propagation of sound via air does not have linear “audio dynamic”, soft of speaking.

Paul S wrote:

Given speakers that can be driven dynamically by single stage amplification, there remain a host of issues, and among those issues is color.  Most compression drivers are color-challenged to begin with…

I would agree. Perhaps lest “soft” materials involved means less opportunities to do “colors”. With the single stage amplification perhaps the same but it very educational to hear MF driver with a single-stage of amplification, particularly with very fast core. It strikes me as very “honest” sound; it has a sense of purity and cleanness that is very addictive if you get use to it. What important is to understand that usually the phrase “clean” sound audio people use only in context of “lean” sound. The Milq’s single-stage doe not sound lean at all, rather just  “full” but “clean”.

nl wrote:

The 6C33 has some adherents, including Lamm and also the well-regarded Almarro amps. However, even Lamm is now using the GM70 for his $140,000 statement amplifier.

It is not accurate. The GM70 is not regular DHT tubes but in a way unique tube in all DH family. This tube has nothing from what commonly considered as typical “DHT sound”, if it has any…

nl wrote:

DHTs have a special character. I wouldn't call them "neutral." But, if I wanted "neutral" I would use a gainclone-type amp. DHTs can be among the lowest-distortion amplification devices ever made. However, most DHT users like the funny addition they make to the sound, and tend to emphasize this aspect.

Yes, they do and also mostly all of them drive their few watts DHT with 90dB full-range load that dive down to a could ohms… 

nl wrote:

Once again, a simple gainclone amplifier, which can be built for $200 or so, will crush a DHT amp in terms of dynamics, bandwidth and headroom. It will crush the Milq amp too, despite Romy's possible protestations otherwise. It will crush any amp that uses an output transformer, as regards those qualities. However, it just doesn't have that DHT (or Milq) tone.

I never trued any gainclone amps in my own playback and therefore I have not reasons to protest. The last gainclone that I heard was last year were 4-way system was driven by 4 or 5 47Lab amps, that are gainclone I belive.

nl wrote:

I have used Russian high-gm tubes like 6C45 in amps before, including single-stage designs very much like Romy's single-stage Milq. These have many attractions. However, in my experience it just didn't have the tone. Jim de Kort of VT52.com came to the same conclusion, regarding his WE437 spud using amorphous output transformers, on his 107db horn speakers. He went back to his 26-10-45 combo, three stages instead of one.  In my experience, a very simple 6sn7-6sn7-45 amp destroyed the 6C45 spud, even with the disadvantages of three stages instead of one.

Interesting… Still, I do not think that the idea to go three active stages to get “some colors” is something that sounds logical to me. I like to use as less stages as possible. It shell be “other ways”. In fact I do have some interesting ideas and not those that that I have expressed in my post above.

nl wrote:

I don't have time to try every possible combination. The high-gm tubes tend to have a certain glassiness which doesn't appeal to me. I even bought some 6E5Ps to give it another try. It would surprise me if the outcome was much different than my experiences with the 6C45 however.

The 6E5P is a perfect two-stage driver (low current and high voltage), it is not out tube. You remember when I was trying to have 6E5P to drive headphones – it was not good. I thought and still think that it is possible to use 6E5P of the 6C45 in the DSET configuration, letting it to drive just HF channel. If it has glassiness then load it harder and it might go away.

drdna wrote:

I think you must be careful to be seduced by the idea of adjustable color, to avoid going down the road that Bob Carver did with the adjustable Sunfire amp or Mark Levinson did with Cello Pallette preamp. It should be more like a knob to fine tune the station rather than a "loudness" button.

Yes, the Carver’s fame did come to my mind and I certainly do not go into the same camp - I hate whatever he did.

nl wrote:

I don't know. Some people like …. supposedly mixing the appealing qualities of each