Feedback on layout for point-to-point Nelson Pass Buffered Pre (and trouble shooting)

[joneci]

I’m at a loss. As before, when I remove the 1M resistor from the RCA input I am
able to read AC voltage from the input to the output.

 

[joneci]

Hooked it up to an amp and without the 1M resistor it passes sound. What is the function of that resistor? And to be clear 1M means 1 mega ohm, correct?

 

[Ben Mah]

If so, then it may have been incorrectly installed, or something was shorting it out. I see that you have bare stranded copper wire for the ground connection. Make sure that is not touching the positive part of the RCA jack.

Yes, IM is 1Mega, or 1,000,000. I believe they are there to prevent thumps or noise when switching inputs.

 

[analog_sa]

It looks like Q201 is wired incorrectly. Rotate it 180 degrees. Looking at the flat side of the JFET, the pins are D G S left to right.

Yes, but does it make a difference with K170?

 

[Ben Mah]

2SK170 and LSK170 have the same pinouts.

 

[joneci]

I guess the question is... what are the resistors across the input (RCA pin to ground) for? Thumping makes sense.

That said, I just removed the 1M resistors on both channel inputs and everything is working. Not quite as it should - obviously it's not exactly as designed - but it sounds good.

I have a shorting rotary switch installed so that might alleviate the thumping in the absence of the resistors.

 

[Ben Mah]

Yes, it will work without the 1M resistors. However they should not be a problem if the resistor value is correct and if installed between RCA + and ground.

I have 1M resistors installed at the input RCAs of a preamp (not a B1) and they do not cause any problems.

Now that you know that the B1 is working, have you tried re-installing the resistor. Try it with clip leads if you do not want to solder it in place.

 

[Ylab]

Maybe your resistors are not 1M ?

 

[joneci]

Will check again in the morning!