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I picked up a Pas 3 today. It has the resistor going from the bass pot on each channel to the circuit board so I'm thinking that it a 3x but there are no indents on the tone controls to tell when they are centered.
Is it a 3x? If the controls don't have stops to tell when you are centered how can you tell for sure?
I've included a small picture (it came from the craigslist posting).
Thanks
Chad
Follow Ups:
There are no detents for either non-X or the X. The X has a 1UF electrolytic capacitor on one leg of the bass controls though, that's the easiest way to tell. If you don't have a manual you can down load it from this site and it will tell how to align the knobs correctly, the rotation from center is NOT symmetric.
Craig
My pre has the capacitor on the bass control so I guess it's the 3X. I downloaded the manual I saw how to align the knobs. It seems sort of hit or miss.Thanks,
Chad
Edits: 03/01/11
It's been awhile since I read the manual, the non-X is the one with NON symmetric rotation. Had to go dig up my PAS-2 manual to make sure. IIRC the X pots go open (resistance-wise) when centered. If you have an DVM you can check that for yourself. I think I used a square wave and a scope last time I did it.
Craig
I thought that maybe I could do that, but am not sure how. Would I put leads on the wires of the pots and read the ohms?
Chad
I might be thinking of something else, just pulled one of my 3Xs off the shelf and checked for open condition at center, doesn't seem to work when the pots are in circuit. Just set it up like the manual says and you'll be fine, the center is not as narrow a range as you might think.
Craig
It's good to know that it's not a narrow range. I was thinking that I would have to get my protractor and brush up on my geometry to figure out the center of the range.
Thanks for your help.
Chad
In the PAX-3x, only one pot in each channel...the treble one...goes open-wiper at the flat position. The bass pot has a dual wiper which shorts out the entire resistance element in the flat position.When in doubt, LOOK AT THE SCHEMATIC!!!
GP49
Edits: 03/01/11
Re tone controls: An ohmmeter can readily tell when the bass controls are centered - all three terminals are shorted, maybe over a 10 degree range (?) or so.
The amount of correction in the stock controls seems excessive - if you need the +/- 15 dB or so, there's something terribly wrong with the source and you probably don't want to listen to it anyway. Half this amount is more than enough, I believe, and you can get this by changing the two capacitors associated with each bass control from 7.5 nF to 15 nF, and the two treble ones from 2 & 20 nF to 1 & 10 nF respectively.
Even at that, the bass controls operate quite abruptly over a narrow range, requiring the touch of a brain surgeon to get what you want equally in both channels. I gave up, and went to switched capacitors for the bass - takes a 2-pole 12 position switch and 6 capacitors in each channel to give 6 boost positions, 5 cut positions and one genuine sure-fire 'out of circuit' position. Chose the capacitors for approx 1.5 dB increments at 50 Hz. I believe some expensive vintage preamps used a similar system, such as the Marantz 7C and some McIntosh models.
But this is a considerable hassle - how much easier to disconnect the tone controls completely, since you may rarely need them {?} - Joe Curcio's site has a paper on how to do this - pretty simple
Yes, the action of the tone controls on the PAS is too abrupt, and on the PAS-2x and -3x with their smaller amount of rotation, it is even more abrupt. Those who remember the behavior of competing equipment in the 1950s when the PAS was introduced, will remember that as being normal for that era.Later on, the purists decried tone controls of any kind. They don't want their flat response sullied. I retain the tone controls on my PAS because I am not convinced that everything in the reproduction chain always has a flat response, including the microphones in the recording hall and the ears of the mastering engineer and producer. I do not listen exclusively to "flat-response" audiophile recordings (in fact for artistic reasons I seldom listen to recordings that were MADE to be audiophile recordings), so I quite often use the tone controls. The less-sensitive tone control action, as described in the prior message, is a good choice.
GP49
Edits: 03/05/11
Well, I was half right. Looking at the schematic would be too easy.
Craig
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