TRL Dude or Joule 150 MKII for Major Pre Upgrade

Ok, did one additional measurement per the instruction Jognsonwu above.
I measured the ohms reading from the RCA center to each of the eight 6sn7 socket pin numbers.

I did this to check the input grid stop resistor.This grid dropper resistor is used to form a low-pass filter to get rid of RFI/EMI. For more reference, please see the following link:
 
http://www.aikenamps.com/InputRes.htm

Pin one should measure 1000 ohms, not 100 according to two individuals that are helping me. Love input from Atmasphere or Al or others who may know something on the this subject.
 
Here are the measurements,
 
Pin 
 
1.   100 ohm
2.    3.9 mohm
3.    1.45 mohm
4.   .527 mohm
5.    3.9 mohm
6.    1.45 mohm
7.   .527 mohm
8.   .527 mohm
 
Checked and recheck.......before I call Aesthetix I could use some confirmation. I am not the most tech savy and must say I have a hard time thinking they would miss such an "obvious" thing? My amp is not under warranty and wonder if this is something that should be made right, or simply just one way to build an amp?

I greatly appreciate the help I have received from all and this is the last request I will make for help before calling Aesthetix again.

I agree completely. 100 ohms sounds way too low. And as the link you provided indicates, too low a value for the grid stopper resistor of the input stage could very conceivably result in rfi problems.

According to some quick calculations, 1K strikes me as a reasonable value. I believe that a value up to around 4K or 5K would not adversely affect anything, the overall bandwidth of the amp in particular.

Kudos to Johnsonwu.

Best regards,
-- Al

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