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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

HK Citation V rebuild - any advice?

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M Gregg

M Gregg

Disabled Account
Joined 2010
Found these,

so a couple of 6cg7...possibly make a driver board..

Its a possible maybe..:)..

Any thoughts on driving four 6L6 or such would be interesting..

Regards
M. Gregg
 

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nuvistordave

Member
Joined 2009
How well this driver would work if this circuit was built as is but with PPP..
4 tubes per channel?
Or with UL option..
Paralleled 6L6...THAT is a 6550!!! Actually I already have a 4A filament xfmr for the changeover on my Cit 5 to 6550s. The high-S 6BN11 (about 60-70% higher transconductance than the older 6CG7) is easily able to drive the 50K grid return resistors required for 6550s. As far as UL is concerned check out my 'strategy 100' amp on fleabay. It has the MESA opt's, running 6550s and the 6BN11 front end. There are scope pix
 
TUBESMAN

TUBESMAN

Member
Joined 2004
At the end of the article the author says he wishes he had a dual video pentode, well a 6BN11 sounds close to me. I think the dual pentode diff driver in this thread is what he may have been thinking about. I will give it a try. I'm buying test equipment to round out my lab. BTW, off topic, Tony I could/should have hooked up with you, I was in Muntinlupa City for two weeks, I just got back this Saturday. I will be back in 9 months, I hope.:D
 
TonyTecson

TonyTecson

Member
Joined 2003
yest, there are lots of tee-vee tubes out there that needs some serious considerations...right now i have a 12AV5 and a 6HF5 pp amps in the works using the 6BH11 tube....

hitachi_nut was at my house the other day, he's from Canada on a visit here, there's another guy from Mandaluyong and he has signified intentions to drop by my house sometime soon...
 
TUBESMAN

TUBESMAN

Member
Joined 2004
Well it is the first time I've seen a person use a pentode diff stage. The link I posted mentioned reasons why someone should do it but I guess most tube amp people would rather stick with what they've seen a 1000 times than something new. I hope in the next few weeks I can breadboard this and test it.
 
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nuvistordave

Member
Joined 2009
3 advantages of running a pentode drive stage:
1) Large voltage swing (tube manual sez use pentodes where a large swing is required)
2) High Gain; allows fewer stages to be used; avoiding instability.
3) High plate resistance allows effective local feedback from output stage

When you run a long tail splitter the 2nd harmonics are suppressed, and...
the pentode characteristics of the drive stage complement the output stage
 
TUBESMAN

TUBESMAN

Member
Joined 2004
I like the wide bandwidth of the pentode driver. I am also a fan of fewer stages permitting less phase shift in the feedback loop. Dollar each is nice too. related question, as far as equivalent input noise and distortion at abt 40V rms, would an EF86 or some other pentode be a better choice? Forget about the cost and extra bottle.
 
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