TRL Dude or Joule 150 MKII for Major Pre Upgrade

Jognsonwu, thanks for your insight. I am not sure how to wire such a resistor as my amp has a circuit board for each input tube/channel. Hard, if not impossible , for me to wire in a 1k resistor. Wish the amp was point to point wired!

It may be possible for me to simply solder an additional 1k resistor from the RCA to pin one and not undo anything else. Is this what you are suggesting?

Correction the grid stop resistor should measure over 1000 ohms and often is a very high value.

No, don't solder a resistor between the RCA and pin 1 of the tube socket. That would put the 1K in parallel with the 100 ohms, resulting in an overall resistance of about 91 ohms.

Hopefully you can unsolder the wire that is presently connected to the RCA jack, and put the resistor in series (i.e., connected between that wire and the RCA jack). That would result in an overall resistance of 1100 ohms.

It might be a surer bet, though, to use a resistor having a higher value, such as the 3K or 4K values I mentioned. The main constraint on how high a value should be used is, I believe, that if it gets too high the bandwidth of the low pass filter formed by that resistance and the input capacitance seen looking into the grid of the tube, based on the Miller Effect, will reduce the overall bandwidth of the amplifier (which is spec'd at 150 kHz). Calculating from the 6SN7 data in my tube manual, I believe that 4K would still be low enough to not have a significant effect on that bandwidth.

Best regards,
-- Al

All depends on how long that curcuit trace is from the RCA hot pin to pin1.
If its less than 3 inches then a 1k grid stop in series ie
UNSOLDER RCA hot and put 1k inline.
SOLDER Socket-hot-->1k-->wire to grid@6sn7.
But if its any longer then you will need help from Aesthetix.

The 1000 ohm value on pin 1 (grid) represents the grid stop resistance at the input. That is not the problem.