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mr mojo 13th October 2005 11:31 AM

About to start a new project: PP 6CK4s...
Well folks the bug has struck again and I'm thinking about starting a new project using PP 6CK4s. I've searched, but didn't find more than just a few mentions of these tubes-anybody got any info?

I've got all the operating points and voltages, a schematic and an article about the amp, but what I'm wondering is if anybody has an opinion about using a pair of them in PP.

PP triodes, good for 15wpc and capable of 35watt transient peaks according to the article. They seem to go for peanuts, and would make for a cheap introduction to PP triodes. Plus since they're an octal socket, I can use the extra ceramic octal sockets I've got lying around.

No need for massive iron makes for a project that's easy on the wallet and the back-after my last project that really appeals to me in a very deep way! HA!

Thanks for any opinions,
mr mojo

Miles Prower 13th October 2005 07:19 PM

I'd go for it. The characteristics of the 6CK4 look good so far as linearity is concerned (since this tube is intended for use as a vertical deflection power amp, it had better be as linear as possible). So far as PP triodes are concerned, there is quite a bit of opinion that this particular topology can have excellent sonics, even with no global NFB (or with just a few db's of NFB).

Since the 6CK4 has a rather high g(m), it's probably best to avoid fixed bias. In the case of PP triodes, what I would do is configure the PP final as a differential amp with a CCS in the tail. This would go a long way towards avoiding any sort of plate current run away even better than using a cathode resistor for bias. It would also help correct for any imbalance between 6CK4's that might be present from the get-go, and which will surely develope as the tubes age.

For a future project, I was considering PP 6V6's operating as triodes (also a common vertical deflection application).

For more information, you might want to try Frank's Tube Data

kevinkr 13th October 2005 07:29 PM

I can recommend the 6CK4 in both pp and se, have done both. Linearity is quite good, and in pp you can get about 10Wrms output from a pair. 6 - 8K primary impedance works well with these. They work just fine using fixed bias, all the ones I have run across have pretty good uniformity. Very stable.

Take a look at my website, there is a very ancient project there using these tubes.


andyjevans 14th October 2005 10:01 AM

Yes - I also made a couple of PP amps using 6CK4. Very detailed, and a stimulating 'immediate' kind of sound. I did find them a trifle strident in the second of the amps and replaced them with 6AH4 which sounded smoother and had really good tonality on strings and voices - anybody tried that? I currently listen to the 6AH4s in this amp - really like the sound. HT is 380v, cathode bias using 100uf polypropylene caps, O-netics 6.6K OPTs. Input stage is diff SRPP using 7193. It's a stereo amp so the input stage has 16 top caps! Very freaky looking. Sound is about the cleanest most pleasant I've achieved, so my other projects come and go and this remains my day to day amp. When you get something right it just seems to stay in the system. Maybe 2a3s would be better in the outputs, but I really like the 6AH4. Less power of course, and the input stage isn't too sensitive, but it works in my system and smallish room (14.5ft by 11.5ft) which isn't too demanding. Andy

Sheldon 30th October 2005 01:24 AM

I did this one. Sounds very nice to me.

Sheldon 30th October 2005 02:00 AM


I meant this one:

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