Konnichiwa,
protos said:
The reviews on the WAVAC were very good
Yet few if any where made under conditions where the Speakers where not drastically compromised (meaning the usual High End dreck). Gizmo raved about all Wavac Amp's, but he was a very enthusiastic gentleman anyway.
Don't get me wrong, the Wavac and Metropolis 833 Amp's both sound perfectly fine, but they lack what makes certain amplifiers more than "fine". If you must have 100...150W and if you must have the "buzzword" SE DHT - then the Wavac or Metropolis (or suitable DIY) are your choice, but I feel that given the total effort a revision of the whole system may give better results for less investment.
protos said:
but anyway what about using the 6c33 or 845.
I have not heard many 6S33 Amp's and non in SE, but it seems an interesting Valve, especially as the low anodeload should make getting really good transformers made quite easy. It is not DHT and not as linear as the 300B but can offer a bit more power and may be easier to get work well enough.
I think the attached circuit would be a good starting point. You may have to get the Output Transformer from somewhere else, Iso/Tango may not have any.
I'd also try the 6072A instead of ECC83 with 2K cathode resistors and 5687 instead of 12BH7 and loose the loop feedback. Try a 1k resistor in the cathode (before the RC combo) to lower the gain of the second stage. This then is close to the famed "Ongaku" and I know this driver to sound well. Use a Nippon Chemi Con VX series cap in the cathode of the second stage and a Silver Mica coupling Cap. Using a 0.047uF Cap (readily available) and a 510k Gridresistor for the follower (270K on schema) and you will be fine.
Use generic Nichicon VX series Cap's for the various PSU decoupling Cap's and better quality "Computer Grade" Cap's for the rest of the supply, you want "Big Can" types, though I have good stuff about Panasonic TSHA Cap's, so maybe worthwhile trying these in the main PSU.
I'd avoid the 845 because of the very high voltages, which pushes cost up and because of their somewhat slow and opaque sound (from all the 845 Amp's I have heard). Better use the 211 but becareful, 211's can sound quite steely. If using the 211 build a "Pseudo Ongaku", e-mail me directly for some comments on this kind of thing.
protos said:
Or is the 300b a one way street to get the best sound without resorting to huge horns.
In my view, using current production output valves and medium sensitivity speakers - yes. The 300B gives enough power for most speakers with a genuine 93db/W/m+ sensitivity Speakers. Using 2A3 or 45 requires you to push up the sensitivity and thus size. There are other good sounding valves with similar or more power output (like someof the old Klangfim stuff) but not much in easy current production and thus a dicey proposition and again, cost spirals.
For starters I'd recommend building a 6S33 SE Amp as noted above, maybe Parafeed, meaning you can use fairly easy to get Anode Load chokes (I think 10H/200mA PSU Choke from Hammond - 193J would work for a starting point) and a 115V+115V : 12V+12V 100VA Torroidal Transformer as output and a decent 47uF/600V MKP Cap (bypassed) as Parafeed capacitor, that is quite cost effective.
Sayonara
