Stupid PAS-2 Pot Questions

neddyboy · 6th June 2007, 04:10 PM

I'm slowly rebuilding a Dynaco PAS-2, and one of the parts I'd like to replace is the volume pot. I ordered the appropriate Alps dual gang pot, but when I went to install it I noticed that the original pot has extra tabs on the back with film caps soldered to them. The Alps pot only has the standard three tabs. Will the Alps pot work? Can I ignore the extra tab? I'm having a hard time figuring out what the purpose of the extra tabs is!

And while we're on the subject of pots, can anyone recommend a good high quality replacement for the PAS-2 balance control pot? I can't find a 750k dual pot. Can I substitute a 500k pot? Will it change the sound?

Thanks,
neddyboy

Brian Beck · 6th June 2007, 04:49 PM

That's not stupid question. The extra tab works in conjunction with the "Loudness" switch to add a bass increase at low volume settings. Most of us in this forum would suggest removing the loudness function anyway. You can delete the two caps and two fixed resistors involved in that function too. So, you can go ahead and put your Alps in.

On the next point, others here will disagree, but I rarely need a balance control. I would just leave it out and wire the inputs directly to your new Alps pot. If you do use a balance pot, you will need one that offers zero (or very low) resistance across half its control range, so that at the "12:00" position there is no added resistance from either section. If you find a 500K unit that does that, it will probably work.

neddyboy · 6th June 2007, 05:00 PM

Thanks Brian. Hey, I'm a native Floridian living in California. Where are you in FL? I grew up in Winter Park and also lived on Captiva Island for a few years.

Brian Beck · 6th June 2007, 05:08 PM

A little town called Indialantic, on the Atlantic coast near Melbourne.

Captiva is/was very nice. I heard it got smacked pretty hard by a hurricane.

Eli Duttman · 7th June 2007, 12:00 AM

Neddyboy,

You are going to have problems sourcing a 500 K balance control. 250 K is as high as I see.

However, you can make your own control from a shorting switch and metal film resistors. You'll need a 2 deck 11 position shorting part. 5 positions either side of center should prove adequate.

ethermion · 7th June 2007, 12:26 AM

The Radio Shack log pot, which is supposedly manufactured by Alps, has the loudness tab. Only a few rubles, and not a bad pot.

6th June 2007, 04:10 PM	#1
neddyboy diyAudio Member Join Date: Sep 2006	Stupid PAS-2 Pot Questions I'm slowly rebuilding a Dynaco PAS-2, and one of the parts I'd like to replace is the volume pot. I ordered the appropriate Alps dual gang pot, but when I went to install it I noticed that the original pot has extra tabs on the back with film caps soldered to them. The Alps pot only has the standard three tabs. Will the Alps pot work? Can I ignore the extra tab? I'm having a hard time figuring out what the purpose of the extra tabs is! And while we're on the subject of pots, can anyone recommend a good high quality replacement for the PAS-2 balance control pot? I can't find a 750k dual pot. Can I substitute a 500k pot? Will it change the sound? Thanks, neddyboy

6th June 2007, 04:49 PM	#2
Brian Beck diyAudio Member Join Date: Dec 2004 Location: South Florida, USA	That's not stupid question. The extra tab works in conjunction with the "Loudness" switch to add a bass increase at low volume settings. Most of us in this forum would suggest removing the loudness function anyway. You can delete the two caps and two fixed resistors involved in that function too. So, you can go ahead and put your Alps in. On the next point, others here will disagree, but I rarely need a balance control. I would just leave it out and wire the inputs directly to your new Alps pot. If you do use a balance pot, you will need one that offers zero (or very low) resistance across half its control range, so that at the "12:00" position there is no added resistance from either section. If you find a 500K unit that does that, it will probably work. __________________ Brian

6th June 2007, 05:00 PM	#3
neddyboy diyAudio Member Join Date: Sep 2006	Excellent Thanks Brian. Hey, I'm a native Floridian living in California. Where are you in FL? I grew up in Winter Park and also lived on Captiva Island for a few years.

6th June 2007, 05:08 PM	#4
Brian Beck diyAudio Member Join Date: Dec 2004 Location: South Florida, USA	A little town called Indialantic, on the Atlantic coast near Melbourne. Captiva is/was very nice. I heard it got smacked pretty hard by a hurricane. __________________ Brian

7th June 2007, 12:00 AM	#5
Eli Duttman diyAudio Member Join Date: Apr 2004 Location: Plainsboro, NJ	Neddyboy, You are going to have problems sourcing a 500 K balance control. 250 K is as high as I see. However, you can make your own control from a shorting switch and metal film resistors. You'll need a 2 deck 11 position shorting part. 5 positions either side of center should prove adequate. __________________ Eli D.

7th June 2007, 12:26 AM	#6
ethermion diyAudio Member Join Date: Apr 2005 Location: ffx station, va	The Radio Shack log pot, which is supposedly manufactured by Alps, has the loudness tab. Only a few rubles, and not a bad pot. __________________ -e

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