Hi,
There are plenty of those on the web but here's a few "local" ones:
http://www.diyaudio.com/forums/tubes-valves/63441-ecl82-6bm8-pp-stereo.html
Search engines are great tools, you know....
Ciao,
There are plenty of those on the web but here's a few "local" ones:
http://www.diyaudio.com/forums/tubes-valves/63441-ecl82-6bm8-pp-stereo.html
Search engines are great tools, you know....
Ciao,
There is a schematic for a well designed 10W PP amp in figure 4 at the bottom of this article. http://www.tube-town.net/info/sed-technotes/docs/appnoteNO.10.html
It is at class-A if it is biased to class-A.
The operation of a typical AB-class push-pull output stage is such, that it operates in class-A most of the power range,
but is at AB-class at maximum and near to maximum power.
For example that ECL82 output stage can supply some 10 W max. Below 8 W it is operates at class A.
The fact is that this output stage gives smaller THD when biased to AB than to "pure" class A.
The operation of a typical AB-class push-pull output stage is such, that it operates in class-A most of the power range,
but is at AB-class at maximum and near to maximum power.
For example that ECL82 output stage can supply some 10 W max. Below 8 W it is operates at class A.
The fact is that this output stage gives smaller THD when biased to AB than to "pure" class A.
ECL82 (6BM8) is a different beast to an ECL86 (6GW8). Making a ECl82 work in a Baby Huey would require some redesign.
The attached is a schematic trace of a Cosmos integrated amp which ran PP ECL82/6BM8.
I sold this amp to my apprentice about 10 years ago (for $100). That appentice is now the production manager and tells me the amp is stil going strong.
Cheers,
Ian
The attached is a schematic trace of a Cosmos integrated amp which ran PP ECL82/6BM8.
I sold this amp to my apprentice about 10 years ago (for $100). That appentice is now the production manager and tells me the amp is stil going strong.
Cheers,
Ian
My version:
8 W at class-A, 10 W at class AB.
An externally hosted image should be here but it was not working when we last tested it.
8 W at class-A, 10 W at class AB.
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It works and has performance equal to most EI' outputs but with generally better bass. Don't knock it until you've tried it.
Garter bias, as I indicated, takes care of saturation issues.
Shoog
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Well,what's the problem ? The schematic I proposed has a mains transformer as OPT (2x115V -> 2x9V)
Mona
High, or sufficient primary inductance is a condition for good bass performance. I agree.
But is this the case with power toroids ? How much is their typical primary inductance ?
Manufacturers do not specify this. Not even all output transformer specifications state primary inductance. For example Edcor.
I assume that with "clean bass" you mean low distortion at bass frequencies ?
But what means "deep bass" ? Does it have something to do with the frequency response at bass end ?
But is this the case with power toroids ? How much is their typical primary inductance ?
Manufacturers do not specify this. Not even all output transformer specifications state primary inductance. For example Edcor.
I assume that with "clean bass" you mean low distortion at bass frequencies ?
But what means "deep bass" ? Does it have something to do with the frequency response at bass end ?
Power toroidals have been measured to have over a 100 Henries of primary inductance. I have measured mine down to 10hz of clean signal.
The only issue to be aware of is that they can only be used with low impedance finals since the ratios are not high enough for anything more. Also they tend to have high interwinding capacitance, usually the extension starts to drop past 40khz and is significantly down at 50khz. this compares favourably with many EI's. They can ring out at 50-60khz and it is important to try the primaries wired in both directions since the capacitance is worse in one compared to the other. If you get it the wrong way round then the ringing can be extreme and noticeable which in turn causes saturation and impacts the bass performance.
Shoog
The only issue to be aware of is that they can only be used with low impedance finals since the ratios are not high enough for anything more. Also they tend to have high interwinding capacitance, usually the extension starts to drop past 40khz and is significantly down at 50khz. this compares favourably with many EI's. They can ring out at 50-60khz and it is important to try the primaries wired in both directions since the capacitance is worse in one compared to the other. If you get it the wrong way round then the ringing can be extreme and noticeable which in turn causes saturation and impacts the bass performance.
Shoog
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