• 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.

I really would like your help on my 300B project

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dhaen

dhaen

Ex-Moderator
Joined 2002
keystrobe.co.uk/
Ralph,

Do you have a test CD or Audio Generator?
If not, I suggest you could download a software generator, and use your computer soundcard, or burn an audio CDR, tpo use in your CD player.

Unless anyone has any better suggestions, I intend to ask you to use your DVM on an AC range, to measure the signal voltage through the system.
__________________________________

10R may be due to the fact that my preamp uses output transformers.
Click to expand...
Mmm. I was beginning to wonder.



Just another thing to check, this is the interstage I use:
Click to expand...
That looks fine. Even the 62K 5%;)
 
dhaen

dhaen

Ex-Moderator
Joined 2002
keystrobe.co.uk/
Ah, good.
Even though it says 400Hz max, that'll be for the stated accuracy. It'll probably go much higher.
Anyway, use 400Hz for now.
Please play the 400Hz track and measure the AC volts output from 1 channel of the CD player, then from the preamp at full volume, and nothing connected.
Next: Connect the amp, and measure between the grid and ground. It should be the same.
 
Ralph

Ralph

Member
Joined 2002
Had to go to -20dB because I only have 400hz @ 0dB.

400 hz -20dB 1,02V from preamp (vol max open).
400 hz -20db 0,17V from cdplayer
50hz -20db 0,18V from cdplayer
10Khz -20db 0,00 from player on DMM

connecting the pre to the power gives 1,01V - 1,03V between grid and earth ...

Maybe we should give it a rest for a day ...
 
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