Hello all. I'm looking for schematics of a good sounding SE amp (maybe one of some classic ones) with the following parameters: up to 5W +-, anode voltage up to 300 V. No special preferences in tubes. I have experience in building tube and solid-state amps. Any advice is welcome. Thank you in afvance
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If you are in Moscow, why not use Russian tubes? I have been using 4P1L as output tubes now for many years in PSE. Needs an output transformer between 3K and 5K. For the input tube I would recommend the 2P29L. Just 2 stage should work into single unit full range speakers. Here's a draft schematic I just put together, hopefully no obvious errors. This uses filament bias for both stages. The voltage regs are Rod Coleman designs from Lyrima - you need 4. This is pretty much the amp I use myself, and I would use it in preference to 300b designs which I used previously.
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This is a very well known design by an experienced engineer. It's 8w with EL34 tubes as final stage, a bit over your target, but it's build many times with success and has an extensive description by the designer
Lundahl Transformers • Easy to build SE amplifier
Lundahl Transformers • Easy to build SE amplifier
All the 4P1L I've used - and I have over 150 - have been excellent Svetlana production, which measure and sound fine. The 2P29L are good too. But if you want a Western flavour, I'm sure you'll get plenty of suggestions. The 4P1L was originally a German military design.
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"Lacewood" employs UL mode O/P tubes, but lacks loop NFB. The chances of inadequate damping factor are, unfortunately, substantial. A possibility is tweaking the 6SN7 section voltage amplifiers by CCS, instead of resistively, loading. The increase in gain would support loop NFB of some kind.
The current production 6V6 to use is New Sensor's "reissue" TungSol manufactured at Saratov, Russia.
The current production 6V6 to use is New Sensor's "reissue" TungSol manufactured at Saratov, Russia.
300B is good sound but are expensive and time life is short, some cheap models last about 700 hours only.
Currently i did not use 6п6с as well as 4P1L.
One more 4P1L SE looks interesting, except fo 2.5 W of output. I haven't seen transistor current sources in tube amps
By the way what kind of output transformer is used in this project? 300B is of no interest to me. Please give me some more examples of good SE schematics (with no . I'd like to study deeply all of them and to pick the one for me.
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2.5W output is in class A2 for a single 4P1L, on 5K load. 2 in parallel on 2.5K load produce 5W in class A2.
In common Russian designs they are used in class A1, 1.8W only from a tube.
Speaking of transistors, it is common on this forum, unlike audioportal where religious beliefs rule.
In this particular amp it is not just a CCS, it is a gyrator, it is explained in the thread.
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Hmmm...
I've be using russian EH-300B gold grid tubes for 6-7 years, at least 700 hours per year.
Just checked and there are a number of schematics out there of SE amps based on the 6V6. When you pick a design I think it is important to pick one that has been built and reviewed by at least a number of people. The reason being that anyone can post a schematic online, but not everyone is a good designer. There are designs (not necessarily based around the 6V6 though) floating around that are not particularly good sounding or even contain serious design flaws.
An alternative you might want to consider is the 2A3. Not quite the 5 watt you are looking for, but relatively straightforward to build and there are plenty of well established designs around.
Regards, Tom
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