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6C4C E80CC PP IT coupled

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hello everybody
few weeks ago i made this lovely small DHT PP with URSS 6B4G Svetlana LogoC
6C4C, interstage LL1660 driven by E80CC , LL1540 splitter driven by E80CC SRPP
sound very nice THD all harmonics 0,1% for 8Watt
THD 1% for 10W so no bad for tube amplifier
E80CC its long life gold pins Philips special Quality very low distorsion medium mu twin triode, here Dario and Haltron made by Philips Hollande Netherland.
also 6C4C are beautyfull and very well built DHT triodes from URSS Svetlana logo C.
5C3S logoC rectyfier, oil caps and electrolithics and choke for HT power supply.
the negative bias on parallel choke 600H 10mA
NP cathode caps, transformer splitter, i now should write down schematics
 

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Those are some nice numbers. What impedance is your output transformer?

A customer of mine dropped off 3 large Gulbransen 6V6 push-pull amps, and I've convinced him that they should become a single pair of push-pull 6B4G monoblocks. I even got a nice pair of 4K push-pull output transformers.
 
The schematic in post #2 has the -57V bias shorted through the choke to ground.
Just a simple drawing error?
its just like my granfather make amplifiers,its not "short" but act like grid choke , its 600H 5Kohm 10mA choke, soud its better, lower thd and noise great stability
just like:
 

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While I admit this way has its right to existence. .. how about the opposite way? Balanced Input + PP IT to parallel SE Output stage, I'm more and more thinking of this way.
Just recently I repaired some custom-made Japanese amp, implemented this way, very liked its sound.
Interesting detail discovered: each of two output tubes had its separate OPT's primary winding, h-m. ..
 
The application of the choke in post # 2 does not match the application of the choke in posts # 3, 7, and 9.
(the order of connections of the bias rectifier, choke, and capacitor are not the same).

Also, the -57V bias into 5k DCR = 11.4mA, a little more than the 10mA choke rating.

The 47uF capacitor across the 600H choke is resonant with the choke at about 1 Hz.
At 20Hz 47uF has capacitive reactance of about 169 Ohms.
That pretty much shorts out the 5K Ohm DCR that is in series with 600H that has inductive reactance of 75.4k Ohms Ohms at 20 Hz.
At higher frequencies than 20 Hz, the capacitor is even more dominant.
 
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claudiomas,

I re-edited the post # 12.
Please re-read it with my new edits.

You have the right idea, but please compare the connections of the chokes in posts 3, 7, and 9. Then check the choke connections in post # 2.

The choke and capacitor in # 3 and #7 form a low pass filter when the ripple of the rectifier goes through the choke, then to the capacitor to ground. The junction of the choke and cap has very little ripple, which is what you connect the center tap to.

# 2 and # 9 put lots of DC current through the choke, # 3 and # 7 do not.

Connected the proper way, there is very very low current through the choke, until you increase the signal level so much that the output tube grids conduct and clip the signal.

Happy listening!
 
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you see in "post 7" attached schematics rectifier go to choke "parallel" to grd not trought "serie"
zoom attached
so its 100mA choke 130ohm , lot of current
my choke its afther rectifier and filter its here for improve 6C4C stability and performances
this avoid grid current and improve stability and sound
this its wath i tink but i've not the teoretical knowlege to prove it
thats way i usually do not post schematics, i do becose somebody ask for.
like many people think Sakuma San its ignorant nonsense amp builder
i do amplifier like artist make music and i have little teoretical knowlege.
yes matejsirk C3=10uF (R1=330 Ohm)? It is enough
for my afther many different values from no cap to 470uf i prefer 10uFNP
i'm self educated tech professional repair audio and in the past TV K7 recorders tape reels radio gear
so i go to try to change this 47uF but i've not 1Hz boat oscillations any way , right now i'm testing with 10uF 100V bipolar NP
you see i do not pretend to teach nothing i just like nice tube amps
 

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@6A3sUMMER - I was wondering about that when re-drawing Claudio’s schematic... looks like one end of the DC feed choke should not be shunted to ground like the decoupling capacitor, but instead it should go to the bias supply.
no schematics of my amp its correct
maeby 47Uf its to be lowered i go check this
RK its 390ohm//10uF NP not 330ohm
 
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