Good sounding 6V6 PP UL driver circuit?

[SHiFTY]

Hi all, I am rebuilding a 6V6 PP UL amp that currently uses an ECC83 per channel as a phase splitter. I don't like the way it sounds without negative feedback- it is quite distorted, and I think it is the driver circuit. I don't mind using feedback, but it would be great to get the distortion very low before this is applied!

Has anyone got a decent driver circuit for me to try? I would prefer to use 9-pin tubes so I can re-use the sockets.

At the moment I have B+ of 375V, the 6V6s have a shared cathode resistor of 470 per side, and the trannys are 8K-8ohm PP UL. Unfortunately, no schematic

Is it worth investing in some interstage transformers? They seem like a very simple solution to the phase splitter problem!

Any suggestions very welcome!

[316a]

Same pinout : E80CC , E180CC/7062 , 5965 , 13D3 , 12BH7 are all ideal , ECC99 may also be suitable . Load resistors and biasing will need to change . 13D3 may be the best if you can find some as they'll be cheap , 7N7 has run some distortion tests on these and they have low high order distortion : important for diff pairs . E80CC rather expensive but similar , 12BH7 lower mu but hard to find at times , E180CC turn up cheap at times , 5965 dirt cheap . ECC99 would have plenty of clout and are current production . I have seen that these are a very low distortion valve but can not vouch for production quality . If you repin : E182CC/7119/5687 , 6463 , 6350 , 6CG7 , 6N1P etc will fit the bill or if you just want to be lazy 5751

316a

[Joel]

Shifty,

An UL circuit shouldn't need feedback to sound decent, IMO. So, I think you can avoid it. Why not just a simple half of a 6SL7 driving half of a 6SN7 as a cathodyne? This is pretty "traditional", and I'm sure you can find a dozen schematics. Try 22k ohms as the Rk and Rl.

Didn't Acro do an UL 6V6 amp? I know they had a 6L6 number that showed good figures with the feedback loop disconnected.

[PassFan]

I have a 6BQ5 amp that uses a 6EU7 as a driver set up as a phase inverter and not a splitter. I like it better, and I've been told that it emphasises odd harmonics more so than even. Maybe this explains it. It specs out pretty close to a 6SL7 yet fits in a 9 pin socket. You can see how I used it here http://www.members.tripod.com/~gabevee/maggie.html
There is lots of info on what you want at this site. good luck

[Joel]

PF,

A 6EU7 is actually a "low noise", 6V version of a 12AX7. It's not even remotely like a 6SL7.

[PassFan]

Originally posted by Joel
PF,

A 6EU7 is actually a "low noise", 6V version of a 12AX7. It's not even remotely like a 6SL7.

Well okay, thanks. I meant that they are similar in that they are high mu twin triodes and share a lot of the same values. I wouldn't expect them to sound exactly the same but looking at the data sheets it looks like the 6EU7 is a little hotter than the 6SL7, at least a little more plate dissipitation and amplification factor anyway. It fits his 9 pin criteria.

[SHiFTY]

How about this one? I grabbed this off the web somewhere, it uses ECC83, but it looks like a pretty straightforward circuit??

[fdegrove]

Hi,

And here's the PSU diagram for the amp above:

Cheers,

[dstockwell]

Hello all, I got a few questions on this above circuit. I am very new to tubes, have built a couple minor sand projects, and that was many years ago. I can follow a schematic thats laid out like this. I am not sure if the iron I have selected is going to do the job. Have yet to find an 8H 200ma choke, or a 9K output transformer, so I went with 10H and 8K. Thanks for any input.

[Johan Potgieter]

Originally posted by SHiFTY
Hi all, I am rebuilding a 6V6 PP UL amp that currently uses an ECC83 per channel as a phase splitter. I don't like the way it sounds without negative feedback- it is quite distorted, and I think it is the driver circuit. I don't mind using feedback, but it would be great to get the distortion very low before this is applied!

Shifty,
Firstly, a great idea to get the distortion low before feedback - a basic principle, but so often overlooked.

But I understand from your description that you have only one ECC83 per channel apart from the 6V6s. If you want to rebuild, this means that ideally you want a one tube driver? If so I presume the ECC83 was one triode feeding a split load 2nd triode. This is seldom a good idea for an ECC83 (or any very high-mu triode). Then you are somewhat limited, and I can only see an ECC81 (12AT7) as an alternative - same circuit, different values.

If you can use 2 tubes per amplifier, as some of the suggested circuits suggest, there are many possibilities. Again I would not fancy the ECC83 type triode for an input stage because of possible Miller-effect influence. My personal favourite here would be a pentode to long-tail pair triode, e.g. EF86, ECC81, with NFB, but as said, there are other alternatives.

Regards