• 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.

New vacuum-tube preamp-project!

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi guys!
I make some preparations for the development of tube preamps with 6922 or 6n23p, ECC88, 6JD8 and etc,.;)
First, go to the schematics (see Figure1 and Figure2).
Which schematic is better in your opinion, so let's move on ...:rolleyes::(
Thank you for your cooperation, going on, ..


  • P1110418.JPG
    486.4 KB · Views: 383
The second drawing has a mistake. The diode is useless and in fact rectifies signal causing distortion.

Also a resistor from arm of pote to ground is useless too.

Finally, I would wire them in DC and plate of first triode bootstrapped from cathode to augment gain and lower distortion. The Valve Wizard, last schematic.
Mr. Osvaldo already-known theoretical things first.
Diode is not too much!?
Question: why does she serve?
Please be specific with the answer of the question, ....
thank you!
Here are the boxes that I prepare for this High-End tube/valve preamplifier!


  • P1110315.jpg
    263.9 KB · Views: 339
Last edited:
Diode SS and diode grid cathode are in parallel and have no DC return. A small AC voltage positive going will be rectified charging coupling cap negative to the side of grid. So in few cycles second tube (Cathode follower) will go cutoff as negative voltage always increases and can't decrease., and first, severe audio distortion will be heard, and then completely no sound until the cap discharges in its own self leakage.(You must turn off power to let the cap discharge). The circuit is completely useless.

Salu2 de Argentina.
You don't have a preamp. You have a drawing. Build a preamp, take some measurements, decide from actual data what you want to improve, then it's worth asking questions.
I designed this schematics, therefore, I ask your opinion is everything wrong with the schemtic and seek assistance schematics is better.
I need to do some changes to the schematics or to all of them right, you understand ...?:rolleyes::confused:
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.