• 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.

Universal tube preamp PCB, ECC99/6N6P/ECC88/ECC85/6922/6DJ8 etc. MU follower or SRPP

With BC547C not work . BC 183C it works. But I ordered a relay.


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Because that the time delay circuit quit simple is. Has every change of value and components influence on the time or function.
By adjusting R/C value you can change start-up delay and with another transistor(gain) you can drive relais with a higher coil current. Try to get about 20 seconds delay, in thar time the tubes are hot enough and output voltage is stable.
With a difference of just a view resistors build and listen to both and tell us which you like most.

Mu-follower has much better psrr then SRPP. Mu-follower can drive lower impedance with same distortion then SRPP.
And there is a difference in harmonics signature. Therefore you must listen which you like best or maybe you dont hear any difference.

Ad simple LCLC filter in DC output to smps and you dont hear any artifacts.
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I did not used the ecc88 but as good starting/working point i would set Ia on 9mA. R4, R7, R14, R17 = 220 and R5, R15 = 10k/3Watt. B+ = 290V for the mu-followwer topology.

And as SRPP R4, R7, R14, R17 also 220 with B+ = 220V, Ia = 10mA.
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(Partially genuine Googgle translate, from France :) )
Hello everyone, hello Koifarm (fantastic project). I land late on this thread, and I'm a bit of a noob. I'm thinking of assembling this preamp in not too long - I'm currently on the NuTube B1 from Nelson Pass. ... And since I have Russian tubes to use (6N6P or 6H6P ? memory)... Some newbie's questions :):
  • The PCB with the 2 tubes is stereo, and not mono? It does not take 2 pcb and 4 tubes for stereo ?
  • Does anyone have a PCB to dispatch? I am very interested! (otherwise I order, JLPCB I think, maybe in one month)
... and probably a few more questions afterwards :D


Joined 2002
It is stereo as you can see in the first post and I have a (red) stereo board for you. Please send me a PM.

BTW you likely won't experience nasties with linear PSUs as these only need to filter 50Hz mainly and don't create HF/RF by themselves. Choosing SMPS in audio simply is gambling.
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