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DC coupled long tailed pairs

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Hi,

is there anybody who used DC coupled longtailed pairs to drive PP output?
I want to use E88CC+ECC99 to drive two pairs of 6550s, triode connected. My problem is the DC coupling. This configuration will be stable for long time? Large offset in the first stage results distortion, and unbalanced bias in the second stage.
Any schematic would be great too.

Thanks!
sajti
 
stigaard123 said:
Maybe these schematics can help you.

http://www.wdehaan.demon.nl/el84dc.html



That EL84 circuit....the front end directly coupled to El84's looks if it is running in starvation mode......omo.. I'm against these circuits as they drift with time. I find thd rather high for hifi.....who would agree ? UL with feedback would prune that down quite nicely. The designs look eaSY to build.

richj
 
6L6's at 600V........:bawling: 5881's would sweat also in UL...no screen resistors ?..rest circuit looks similiar to my trumpet amp except using 807's in true tetrode..but 75W...these can take 600V with a breeze. Only personal choice as sound is far sharper and one hears more wind harmonics with these beautiful RF tubes.

richj
 
Re: dc coupled

reinhard said:
Think Sajti means a dc coupled driver stage.

ARC is doing so in their CA 50, two diffamps (6922) working on current sources. Not a good idea, tube matching is critical and with aging the driver is running out of symmetry, more distortion.

Reinhard

Yes. I think to use DC coupled driver stage. And yes, ARC use it. Somewhere with servo (in VT150), somewhere without servo (VT100). I will put the schematic I planned, to see it!

sajti
 
Here is what I planned. I didn't calculated the resistors. The 1st valve is E88CC, the second is ECC99

sajti
 

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