Hi there all,
I usually do valve stuff but have accumulated some nice Sanken complimentary pairs and the dead guts of a Zen V3. I want to build something which has a fighting chance of comparing with my Class A PP valve amp.
I came across this design when searching and it looks to have the virtues of elegant simplicity and Class A operation. Has anyone built it or anyone care to express an opinion on its potential performance.
Details are a bit scant, and it doesn't even suggest potential power output. I only need about 8Watts of good class A.
Shoog
I usually do valve stuff but have accumulated some nice Sanken complimentary pairs and the dead guts of a Zen V3. I want to build something which has a fighting chance of comparing with my Class A PP valve amp.
I came across this design when searching and it looks to have the virtues of elegant simplicity and Class A operation. Has anyone built it or anyone care to express an opinion on its potential performance.
Details are a bit scant, and it doesn't even suggest potential power output. I only need about 8Watts of good class A.
Shoog
Attachments
I've built and used the second half without the last pair. Prefered it modified to use a jfet
in and a Mosfet out... but it's a good buffer...
I'd suggest you try the Pass F5 if you want to beat up ur 300B PP amp... of course the specific parts you use for the F5 will change it's sonic appearance rather a lot...
Otoh, why not try something like what you have shown... not sure how the two parts shown got combined, as they seem to be from different sources...
_-_-bear
got combined, but...
in and a Mosfet out... but it's a good buffer...
I'd suggest you try the Pass F5 if you want to beat up ur 300B PP amp... of course the specific parts you use for the F5 will change it's sonic appearance rather a lot...
Otoh, why not try something like what you have shown... not sure how the two parts shown got combined, as they seem to be from different sources...
_-_-bear
got combined, but...
Have the Sankens so thought this would be a good try out.
I know the F5 is an outstanding amp, but I don't want to splash the cash when I have good components lying around.
I was contemplating replacing the front end with a Valve stage - an octal for a change.
Shoog
I know the F5 is an outstanding amp, but I don't want to splash the cash when I have good components lying around.
I was contemplating replacing the front end with a Valve stage - an octal for a change.
Shoog
Drawn as it is, the output stage won't work. Stee draws stuff like that all the time...
If you want BJT power buffer that much, you can try this (Push Pull Pure Class A "Hot Follower 99" Amplifier
designed by: Andrea Ciuffoli) - at least, it will work:
Andrea Ciuffoli - Home Page
If you want BJT power buffer that much, you can try this (Push Pull Pure Class A "Hot Follower 99" Amplifier
designed by: Andrea Ciuffoli) - at least, it will work:
Andrea Ciuffoli - Home Page
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So how about Pavels Buffer.
This is a proven design right ?
Though it would seem that a quick look at the outputs datasheet suggests they are an entirely different beast to the Sankens I have.
Shoog
This is a proven design right ?
Though it would seem that a quick look at the outputs datasheet suggests they are an entirely different beast to the Sankens I have.
Shoog
Attachments
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PMA Pavel's buffer is much better.
If you want Class A.
You can count on he has fineadjusted as much as possible.
You can trust his circuit.
For other voltages than 27V you should change R11/R12 accordingly.
You should be able to use other OP Transistors.
Some would even fit better.
THe output pair are not critical to that circuit
If you want Class A.
You can count on he has fineadjusted as much as possible.
You can trust his circuit.
For other voltages than 27V you should change R11/R12 accordingly.
You should be able to use other OP Transistors.
Some would even fit better.
THe output pair are not critical to that circuit
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Thanks for the input.
My understanding is that this circuit is capable of 35W class A. My valve experience says I need just 8W to be happy. The transformer I have is a beefy 12-0-12V AC so would be running just +/- 16V DC.
It seems this buffer requires about 15mA of drive from the front end.
The Sankens I have to hand are the 2SA1215/2SC2921.
Seems like a runner though - will study this more in about a week when I am not so busy.
Shoog
My understanding is that this circuit is capable of 35W class A. My valve experience says I need just 8W to be happy. The transformer I have is a beefy 12-0-12V AC so would be running just +/- 16V DC.
It seems this buffer requires about 15mA of drive from the front end.
The Sankens I have to hand are the 2SA1215/2SC2921.
Seems like a runner though - will study this more in about a week when I am not so busy.
Shoog
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I have spice models for 2SC2922/2SA1216. But not 2SC2921/2SA1215
As I told, I do not think there is much problem with what power transistors you use.
More important is to use 2 good drivers of the big transistors.
Here I post my take on +/-16 Volt Diamond Sziklai in Class A.
It shows very low distortion for being with No Feedback.
Input is +/-12 Volt peak, ~ 9 Watt RMS Class A
THD simulates to 0.006%
Output transistors are 2SC5200/2SA1943
As I told, I do not think there is much problem with what power transistors you use.
More important is to use 2 good drivers of the big transistors.
Here I post my take on +/-16 Volt Diamond Sziklai in Class A.
It shows very low distortion for being with No Feedback.
Input is +/-12 Volt peak, ~ 9 Watt RMS Class A
THD simulates to 0.006%
Output transistors are 2SC5200/2SA1943
Attachments
I'd probably use a current mirror or constant current source/sinks rather than the bootstraps, but it does work. I use a smaller version (with TO-220 outputs) as a headphone amp.
So I am thinking I can build the output buffer in a separate case and then build various front ends in other cases to try out lots of different flavours.
Shoog
Shoog
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Joined 2009
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Not done it yet as I got distracted with building a new version of my DC7 concept.
I am now hoping to get back to this project at some point soon. I have a nice case, a pair of high quality heatsinks and a beefy transformer.
I have some nice 6j5g which I though I could use as the voltage gain stage. The only concern I have is generating a DC offset voltage at the output due to the slow warm up of the valves. I had a bad experience with this when I built my first valve buffered gainclone and it took out my vintage Isophon drivers. I now have vintage fieldcoil speakers and the comfort of having a transformer to protect them cannot be underestimated.
Shoog
Member
Joined 2009
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