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SE 6CB5A amp with 6N7 driver

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#61
Exactly, the 6829 makes the sound (much tougher bass response, explosive mids compared to the optimized ECC99), but nevertheless there are some people that are crazy about this 5 star tube as driver.

"These sound fantastic, similar to the TFK 5965. Huge, I mean HUGE soundstage, great bass, vivid vocals and detailed yet laid back highs...."

Replacing the 6829 in my 6CB5A pp-tube amp I had still problems with respect to range beyond 10kHz. Maybe its a matter of personal taste..
My experience with the 6829: Modifying the load-resistance (33 up to 82kOhms) means a change of sound.
I'll give the 6CB5A another chance by trying SE...
 
#62
Hi!

Maybe some people are crazy about this tube because of the way it distorts. Just look at the data sheet. This tube was designed for switching applications as in computers. This just has to do on/off. Linearity was not a concern at all. Especially when you use it to drive a triode wired 6CB5a which requires a substantial swing of up to 150V peak to peak, the 6829 will produce substantial distortion. No chance to evaluate the sound of another component or tube in such a set up. And that is why your experience with the 6CB5a differs from that of many other people who tried it.

Best regards

Thomas
 
#64
Vinylsavor said:
Hi!

Maybe some people are crazy about this tube because of the way it distorts. Just look at the data sheet. This tube was designed for switching applications as in computers. This just has to do on/off. Linearity was not a concern at all. Especially when you use it to drive a triode wired 6CB5a which requires a substantial swing of up to 150V peak to peak, the 6829 will produce substantial distortion. No chance to evaluate the sound of another component or tube in such a set up. And that is why your experience with the 6CB5a differs from that of many other people who tried it.

Best regards

Thomas
Click to expand...

Thomas, how does the 6N7 as a differential amp? I have some nice RCA valves and I am thinking to give them a go driving them from an input phase splitting transformer (probably a Sowter, model 1125 or 9100).
 
#66
Vinylsavor said:
Hi 45,

I never tried that. But why not? Bear in mind that each section has a plate resistance of about 20k. If that is fine in your application I would try it.

Best regards

Thomas
Click to expand...

Yes, that will be fine. It would be the input stage of a 3 stages power amp. If the sections are well matched in DC I might also try direct coupling to the driver.
The driver will be transformer coupled.
Thanks.
 
#68
A question for Thomas or anyone else with experience:

Would the 6CB5A amp on your VinylSavor blog work with a volume pot at the input. I like the design and your documentation, but would like to keep the build to one box. I don't really have a preamp right now. Just a Pass B1 buffer. I would prefer not to use it, though.

I was thinking of the original IT version as a stereo integrated amp. Would this work?

Thanks!

John-
 
#69
Hi John,

the transformer coupled version needs about 1.5V RMS at the input for full power out.
If you use regular 2V sources, it would work with a pot at the input, but you will not be able to get full power with recordings which have a lower level.

The amp was designed for usage with a line stage, hence it is not too sensitive at the input.

Best regards

Thomas
 
#71
Hi John,

yes in the integrated version I added the line stage which I use in my Octal Line preamp. This way I have a little reserve in gain.

If the sound will suffer without a line stage depends on your sources. If they have good output stages, can drive the interconnects to the amp properly, there will be no problem. Usually it should work.

I generally prefer separate preamps since I am using transformer volume controls which sound best when driven from their own low impedance buffer stage. Fitting that into the power amp would eat up too much space. In my integrated amp I compromised and used a resistive volume pot.

Best regards

Thomas
 
#72
Hi Thomas,

Thanks, again, for your generosity in answering my questions.

Have you tried paralleling the 6BC5As? What sort of changes would this require? I'm guessing that one tube would give roughly 6-7 watts before clipping? I am using a triode straped EL34 (6-ish watts) now and I have ALMOST enough power-- that is enough power for most recordings I have.

Of course, I'd rather have better than more, if I had to choose.

Best,
John
 
#73
Hi John,

I thought about paralleling 6CB5as but never got around to actually do it. I did build a Push Pull 6CB5a amp once. For my taste the 6N7 driver tube would have to high plate resistance for driving two tubes in parallel. So if going PSE, I'd prefer a different driver.

Parallel tubes would require an output transformer with half the primary impedance and which is capable for twice the DC current.

Best regards

Thomas
 
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