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Very good, floobydust. They are exactly my thoughts about the “period tubes” as well. In addition to that I think that factor that call “Holly Ignorance” did take place with some vintage tubes. They might not have too high demands for the quality of the tubes 60 years back but they have not yet developed bad technological habits back them. It is very similar to making speakers drivers – in past they did not have high demands to quality but they did not have back then the nowadays idiotic ideas how sound might be taken out of loudspeaker by barbaric methods.

Saying that I have to note that that idea of contemporary production by sensible and knowledgeable people of some vintage tubes do look attractive and the Chechslovakians are a good illustration. The concern that I have is that they might replicate and I am sure improve the contraction. However, I do not think that the today tubes makers might do anything with materials. It is highly possible that all materials sources by all manufactures from the same “generic” suppliers – considering the quality of today tubes production no one would cook metals and coatings specifically for tubes. Well, how different would it be from many other fields?

floobydust wrote:

I don't really know anything about the YO185 but would like to see some info if available.

http://www.romythecat.com/GetPost.aspx?PostID=9344

http://www.romythecat.com/GetPost.aspx?PostID=9407

floobydust wrote:

The 10Y was obsolete long ago and the preferred replacement was the 801. While they are similar they are not identical. There are two significant factors that differentiate these from the 45/2A3 variants: 1- They use a thoriated filament/cathode which requires 7.5V. 2- They require a fairly high load impedance (around 7K) and higher plate voltage (around 600V). The down side is also two-fold, higher impedance OPTs are more difficult to make and keep an extended high-frequency response. The filament/cathode design will require a DC supply to keep the hum out. You won't gain any additional output power over the 2A3... about 4-watts max. It will cost more to implement and it's doubtful if you'll get any (audible) improvement over a 2A3.

Hm…  I do not know. I have some sources that I respect who in fact very much encouraged me to go for those thoriated tungsten cathode tubes with very high impedance in plate just because strictly considerations. I less care about the high-frequency response as in my care it will be DSET for 1kHz and up (3200Hz electrically) and therefore the transformer shell not care any inductance. If I go for LF cut off let say 400Hz then it will be possible to use reasonably-minimum amount of widening and HF would not be a big deal. The only thing that holds me is that many of 10Y/VT-25 out there are dead or “wrong version”. I did explore the subject. With 2A3/45 it is more attractive as there are so much more options…….

floobydust wrote:

Finally, I'm not sure where your preceived need of four transformers comes from. I have 45 and 2A3 designs which are flat out to 45KHz at full power with low distortion and the only transformer in the signal path is the OPT.

When I said four transformers I meant that I can see 4 type of the tubes. The 2A3 with 700-80R on plate, YO186 with 1200R on plate, the 45 with 1800R on plate and 10Y with 5K on plate. Hey are requires different transformers.  I do not like taps. I like to have transformer with remapable sections. The 2A3, 45 and YO186 still might be possible to care with one transformer; the 10Y would need a very different beast. Also, I have a filing this time to try something different. I might go with DHT for a slower core OPT but to load anodes more idle – I have a feeling that it might bring me where I would like to be. I am thinking about 4.5K-5K for 2A3 – I mean a lot of impedance, as much as my S2 will be able to handle. I even will to give up a bit speed of my code for trying it…. In my single-stage IDHT amp I have no gain to afore this luxury.

floobydust wrote:

What is/was your thoughts on circuitry?

I invasion absolutely nothing fancy. It might be the very same Milq’s driver stage:

http://www.romythecat.com/PDF/Melquiades_SET.pdf

with only differences that as the output tube will be cathode-based DHT. I still debate if to couple it with good quality cap of transformer of 1H inductance. Bothe ways have attractive sides. Anyhow, I begin to sound like Lynn Olson with his inexhaustible BS-talk about his bogus loudspeaker project…

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