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nl wrote:

Gordon Rankin of Wavelength Audio did a series of one-stage DHTs with a step-up transformer input about ten years ago. I think they were called the Mercury series. By all accounts, they sounded good, but of course had limited gain, not much power and had to be driven by a powerful preamp, which involves at least one and probably two stages if you use tubes.

I did not know it. I wonder how your DHT people consider the sound of one-stage Wavelength compare to the multi-stage. Did the Rankin’s one-stages amps had the DHT coloration that you admit exist in other DHT amps. Anyhow, I feel that those Wavelength Mercury series might not be even illustrative if DHT might do really “clean” sound as I am sure Gordon targeted mass-market with this full-range addenda. In DSET configuration it shall be a different amp. The inductance of input transformer shell not be nearly 100H and the output transformer might have a LOW of less turn. That all shell greatly improve HF end. Also, 10 year back Gordon most likely did not use amorphous core that I found a very good thing to do for HF DSET.

nl wrote:

I think using a DHT amp only over 3000hz would be somewhat self-defeating. I would try to use it at least over 600hz,

Why?

nl wrote:

… and use a 45 tube, not a 300B. The 45 is a wonderful tube for running compression drivers. If you use a 45, however, you probably won't have enough gain even with a 1:4 stepup.

I most certainly not going to go with 300B if I decided to go there. Most like it will be 2A3 or anything else with sub 1000R on plate that would allow me to use my currant OPT transformer. If I find the DHT idea worth for me to stick with then I might order a dedicate OPT and then I will be open for high-gain high impedance DHT. At this point I do not know how it all meaningful. Perhaps I need to take 6V.3 6A3 and juts plug in on 6C33C filenames with a regulating resistor and to see where it would go. I mean there are many ways to implement the thing but do not looking DIY project but for a sensible sonic result.

nl wrote:

Personally, I would forget about the input transformer, and just use a 6SN7 driver. RC coupling is fine. Many people like carbon comp resistors for the plate load, and paper/oil capacitors for the coupling cap here. PIOs take some time to break in. You might later try substituting an inductor for the load resistor. Of course you want to use a good 6SN7, not a new-production Russian or Chinese model.

I do have a very good driver (my 6E5P if I wish to go two stages). I did when in past from 2 stage Milq to one stage Milq I did like the new level of “laconic clarity”. I would like do not lose it.  Also, it is HF only DSET that need juts 1W? What do I ever need two stages? Well, I might need but juts do not know about it, will see. At list the idea of transformer and DHT is worth to try before to go for 2 stages a, coupling, DC stability, sound of the driver and all the rest. I also not really not willing to modify the 6-ch Milq as whatever it does now is fine. So, to do some work on it I really need to have evidence that DH will be advantageous for my MF driver.

nl wrote:

A nice 6SN7-45 amp, RC coupled with carbon comp/PIO, and a decent powersupply that doesn't sound drecky (which probably means NO cheap high-value industrial grade electrolytics, or at the very least a film cap that is isolated from the electrolytics with a resistor or choke), and whatever tricky bias schemes turn you on, would be a good intro into the sound of DHTs.

I do not know. I hardly ever see heard not drecky low power DH amps. All of them sounded very dead to me those idiotic full-range amps and the idiotic music that they looks like constantly play.  I have seen a few DH with stupidly made high-sensitively systems with horns- but it you read my site then you know my attitude toward sound of stupidly made horns. So,  I do not know which ingredient was wrong in the DHT that have seen before – I think most like it was the awareness of the amp builders but it another subject.

nl wrote:

Pay attention to the quality of the filament supply. The Tent Labs boards seem to get some acclaim, but I shy away from IC regulators in this position. You can try an IC current source filtered with a cap and choke such as Hammond 159ZC, which is 60mH and 2A, 0.7R.

Interning as you are today a second person who insists in DC filament supply. It is pretty me everyone strongly  in past suggested me to use AC on filaments. Can you elaborate on it?

nl wrote:

Then, I would use it on your S2 driver in the 600-12000 range, and turn off your other S2. I would also turn off the "injection channel." That would give you a better idea of how it sounds.

Come on, of course when try to evaluate how my MF sound in with different amps then I turn off my "Injection Channel”, how with it? To use the S2 driver in the 600-12000 range is another subject, I would like do not go there at this thread. BTW, the 6E5P with the "Injection Channel” might be very much make the DHT triode journey not necessary. I do not have a position about it at this point. Well, you are local from east cost, right? So, feel free to bring your single DSET and to see how injected Macondo work against DHTed Macondo. I wish I spent more time (or had more time) to evaluate THIS aspect when I had my 300B. I am planning to do this try again.

nl wrote:

Lastly, put in a line-level filter at the input instead of using a speaker-level crossover. The same circuit as is used with your 6E5Ps would be fine.

I a not intending to use speaker-level crossover. I am not going to put a resistor in primary of input transformer, using the transformer shunting inductance as a second order high-pass. Probably I would need to add some coils in parallel with primary….

nl wrote:

Given that you are using a solid-state preamp with presumably lots of driving power, you might consider a 1:4 stepup and use of either an EML 20B tube or the AVVT AV8 tube. That might get you enough gain. I think Rankin used the 20B in his Mercury amps. The 20B would take a rather special output transformer, as it has an Rp of 3200. I think Rankin used a parafeed output here. A typical 5K:8 OPT could also work, on the 16 ohm drivers, as the reduced inductance is not so much a problem since it would be used above 600hz. The AV8 is somewhat more forgiving, with an Rp of 1500. The new TJ PX25 has a gain of 8 and an Rp of 1500, another possible choice here.

Thanks, I will look at those tubes and will consider them. I am not convinced but I might use this input transformer:

http://www.lundahl.se/pdfs/datash/1544a.pdf

… that can go up to to 1:6…

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