No more 60 Hz hum in a PL2000 preamp.

[George S.]

When I went from new quality Alps pot to cheap stepped attenuator (cheapest I could find) in my headphone amp, it was like going from an old busted Walkman to a center seat in symphony hall.

It is crazy how drastic the difference is.

Jim, good to know. Going to do some reading this week and find out why. Think it has to do with impedance and frequency.

 

[J!m]

Replacing a shitty resistor (pot) in the signal path with a good one I think.

 

[George S.]

Also going to read about those Penney and Giles pots used in the Aragon 24K pre and what makes them good.

 

[e30m3mon]

George - how do you switch power to the 2000-II ? The original power switch was on the back of the volume pot. Power strip or some external means to turn the preamp on/off?

 

[Hexis22]

Also going to read about those Penney and Giles pots used in the Aragon 24K pre and what makes them good.

Interesting discussion and data for P&G pot (Model No. D460355/C) upgrades on a Krell KRS-2 pre:

https://pinkfishmedia.net/forum/threads/krell-krs-2.158527/

 

[George S.]

George - how do you switch power to the 2000-II ? The original power switch was on the back of the volume pot. Power strip or some external means to turn the preamp on/off?

Building contractor grade power strip. Normally all power switches are left "on". Haven't used the power switch on the preamp in years, so it isn't missed. Additionally, the extra power outlets built into the preamp aren't wired. All aimed at reducing 60 Hz noise.

 

[George S.]

Interesting discussion and data for P&G pot (Model No. D460355/C) upgrades on a Krell KRS-2 pre:

https://pinkfishmedia.net/forum/threads/krell-krs-2.158527/

View attachment 75962

Thanks Eric, going to study this at end of work day.

 

[J!m]

That sheet looks like the specs from Krell to P&G for the pots they ordered.

But it gives some insight into what they requested.

The attenuators are generally better than those specs. .1% or better resistors on both tracks so track matching and attenuation are both better.

 

[George S.]

Ordered some 100K mono Dale ladder pots to sub for the original 50K stereo pots. The early PL 2000 S1 preamps used a single 100K pot. Should gain needed distance from the transformer and it'll be interesting for results.

 

[George S.]

Interesting discussion and data for P&G pot (Model No. D460355/C) upgrades on a Krell KRS-2 pre:

https://pinkfishmedia.net/forum/threads/krell-krs-2.158527/

View attachment 75962

Eric, such a interesting thread you linked to. I'm going to have to reread it several times to get the most out of it. Amazing how far down the food chain these old PL preamps are, but that's OK with me. Interesting how they had the issue with the P&G volume pot after such a long wait. Then the further wait, and then the Krell chief design engineer of the piece comments. And the photos are very interesting. Wow, very cool, a very interesting read, thanks for sharing!

 

[George S.]

Interesting take on the P&G from the thread.
"Model No. D460355/C Notice how the max differential between left and right tracks is specified at a maximum of 0.5dB, that -as it turns out- was the critical figure! The D19992 was a max deviation of 2.5dB.
The best potentiometer out there, that is unless you go to rotary fixed resistors....and some other exotica that may well out live my grandchildren!"