6CG7 replacing E88CC in SE KT88 Amp.

[mastodon]

Start a new thread, include all relevant information and formulate a clear question. This here thread is about substituting a 6CG7 for an E88CC in a specific amp. I'm sure people are willing to help you out (I'll chip in where I can).

 

[Zekk]

The 6CG7 is just a noval version of the 6SN7. Seems to me it will work fine, tho u will have a little less gain.

SemperFi ... you're absolutely right!

No venture no gain.. right!
So, I replaced the E88CC with a Westinghouse 6CG7 black plate, expecting a huge humming but it was dead silence.
Spinned a Sarah Brightman disc for sound and was rewarded with the most gorgeous sonic that've ever comes out of my SE KT88 amp.
And when I play Karajan's version of "Introduction", it was phenomenon!
The music just drown me like the onslaugh of an approaching tsunami.

Direct plugged in with no re-soldering!
Same parameter as E88CC, 173vdc on plate, 2x orange LED = 4.3v.

OK! Any suggestions for the best operating parameter ... thanks!

BTW, I'm puzzled why no one mentions using 6CG7 for those heap loads of SE KT88 builts, found in various forums?

Guys ... I'm elated!

 

[rock4016]

That op point is fine for the 6CG7. I calculated about 7 mA. It's probably not used as often because it doesn't have enough gain to drive most KT88 output stages. I built a KT88 SE amp a few years ago and used a 6SN7 beta follower to get the full gain of the tube and in some cases it really needs gain from a preamp to get the most out of it.

 

[Miniwatt]

I was comparing both tubes' data sheets, but I can't seem to find the ecc88 plate resistance?
Philips datasheets are the easiest to find, I presume 'R eq' doesn't stand for plate resistance?

-edit- JJ's E88CC/ECC88 is 2.8 K..
Never mind!

 

[DF96]

Req is equivalent noise resistance.

Ra = mu / gm - these are given on the data sheet

 

[Miniwatt]

Req is equivalent noise resistance.

Ra = mu / gm - these are given on the data sheet

Thanks, 'diy studying' has it's hurdles

 

[Zekk]

That op point is fine for the 6CG7. I calculated about 7 mA. It's probably not used as often because it doesn't have enough gain to drive most KT88 output stages. I built a KT88 SE amp a few years ago and used a 6SN7 beta follower to get the full gain of the tube and in some cases it really needs gain from a preamp to get the most out of it.

Ya .. there's a reduction in gain but have no adverse effect to my set-up. Gamut CD-1 output is 4v, into Eico HF85 preamp.
To my ears, the one most important improvement is the elimination of that high pitch metallic tone in female vocal, found in some of the re-mastered disc.

Perhaps, I should now jack-up the dissipation!

Thanks to All for the responses.