• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

6922/ECC82 Preamp

An ECC82 is not a 6922, in fact nothing like it.
A 6922 is an ECC88 or as the Americans call them E88CC, an ECC88 has no centre tap in the heaters as they are wired in parallel. That means pin 9 is a screen and the heater voltage is 6.3v only.
It was designed as a VHF cascode amplifier, which is why there is a screen between the two anodes.
An ECC82 or 12AU7 is for low frequency, audio amplification with series heaters between pins 4&5 with pin 9 as a centre tap.
The schematic shown uses a 403 Ohm cathode bias resistor. Now someone is surely having a laugh because no valve is made that precise to require such a value.

I would say it was calculated but never made.
 

Kdent

Member
2020-02-10 3:42 pm
Florida
An ECC82 is not a 6922, in fact nothing like it.
A 6922 is an ECC88 or as the Americans call them E88CC, an ECC88 has no centre tap in the heaters as they are wired in parallel. That means pin 9 is a screen and the heater voltage is 6.3v only.
It was designed as a VHF cascode amplifier, which is why there is a screen between the two anodes.
An ECC82 or 12AU7 is for low frequency, audio amplification with series heaters between pins 4&5 with pin 9 as a centre tap.
The schematic shown uses a 403 Ohm cathode bias resistor. Now someone is surely having a laugh because no valve is made that precise to require such a value.

I would say it was calculated but never made.


Is that schematic still possible to replicate, or better off finding a new design?
 
From what I heard tubes need either 12 or 6 volts to the heater as well as the additional 200-300v to operate. Maybe I'm wrong, or can the schematic just run on a single 200-300v supply?

There are two heaters, one per triode.
You can connect them in series or parallel.
If in series apply 12.6VAC across them.
If in Parallel apply 6.3VAC across them.

Look up the data sheet for 12AU7 and you see how to connect the heaters.
 
schematics is there, what else do you need?
heater, 6.3 volts on pins 4 and 5
 

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Look at the Broskie Aikido line stages at Tubecad.com. A decent sounding one can be made to run on as little as 80 volts B+ up to 300 volts B+. The Aikidos require two tubes per channel, four dual triodes for a stereo preamp. To my mind a 12AX7 is not the best tube for a line stage. Personally I like the ones based around 6922s, ECC88s or whatever you want to call them.

Good luck.

Aikido Line-Stage Amplifiers
 
schematics is there, what else do you need?
heater, 6.3 volts on pins 4 and 5
This schematics is valid for ECC88 / E88CC / 6922


ECC82 is different as the middle point is tied to pin 9, 4 and 5 to the filaments.
Connecting filaments in series need 12.6V between 4 and 5, connecting
them in parallell is between 9 and (4 and 5 interconnected )
ECC83 and ECC81 is also connected this way.
 
An ECC82 is not a 6922, in fact nothing like it.
A 6922 is an ECC88 or as the Americans call them E88CC, an ECC88 has no centre tap in the heaters as they are wired in parallel. That means pin 9 is a screen and the heater voltage is 6.3v only.

No, a 6922 is an E88CC ; the American designation for ECC88 is 6DJ8 as the bloke makes clear in his article.
 
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Francois G

Member
Paid Member
2004-06-16 8:36 pm
Illinois
Dear Kdent,

I applaud you for your interest in tube audio and your desire to build something. I would like to caution that you may not have the necessary background to tackle a preamp schematic and build it on your own. Perhaps the place to start would be a complete kit with step-by-step instructions. The questions you ask indicate that you would benefit from some learning before trying to “play with high voltages”. In the sticky section of this forum there is a tutorial which would help and also a thread on working safely with high voltages.
Start with the tutorial: On Line Tube Learning for newbies....

Good luck with your tube learning, and come back here if you have questions.
 
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