• 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.

6V6 line preamp

diyAudio Chief Moderator
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Extra temp protection with dual fan pcb with microcontoller here in Greece the summer its too HOT
This micro controller uc consumes very little energy with this programming because it goes to sleep after 60 seconds of inactivity. It wakes up after two minutes and controls the temperature. If needed (42degrees up limit) will activate the fans and adjust their speed according to the measured temperature. It goes back to sleep when the measured temperature stays below the threshold I have set 38 degrees down limit for as long as it takes. (60 seconds)
I'm currently using a single fan for the DAC that I have 4X4 cm with a starting voltage of 4.68V very sillent having a margin of up to 10.50V but I do not think it will ever overcome 7V in the summer. Before i have 52 degrees on heatsink
now 42-43 steady.

Nikos, that's quite sophisticated. Congrats.
 
Hi Salas,
I've always been an admirer of your work here, and I'd like to build the buffer version of this preamp to go into a Juma inspired 2sk2013/2SJ313 F5 that I built last year.

I'd like this preamp/buffer to do double duty as a balanced to unbalanced converter, so was thinking of putting this transformer at the input prior to the tube stage: EDCOR - TPC Series

I was thinking of going with the 10K:15K version, so as to get a tiny boost in gain, and I figured the 10K input would be a safe bet for a wide variety of sources. Do you see any issues, downsides?
 
diyAudio Chief Moderator
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There is very high input impedance in the buffer that will reflect to the primary if without any resistor from input (before cap) to ground. Maybe it can pick noises easier. But you can also define the input impedance of the buffer with just a resistor in the pot's place.
 
50Hz hum. Vhat can I do?
SSHV is not plug in.
 

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Slowly getting started

I'm gathering the parts to get this project started. I got this awesome Radiodyne chassis to build it into (attached). It even has a spring suspension platform for the tubes. Perfect! I'm going to build both the follower and gain version into the same chassis, because I have the room, and it's not that much more work to do both at the same time.

A few questions though:
For the follower version:
  1. What does FT-3 mean on the input cap?
  2. What wattage resistors for 180R, 470R, and for the 5K is that 20W?

For the gain version:
  1. I’m going to source everything from Mouser or Digikey. What easy to find resistor types do you recommend in place of the 5W and 2W Kiwame?
 

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