potentiometer pass aleph 1.7

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
I having a little problem deciphering the request, but here goes:

There a three places you can put variable resistance in an
Aleph P to alter the gain

1) You can place a dual potentiometer on the inputs as a
voltage divider. (dual pot required for 1 channel balanced)

A good value for this is 10K to 25K

2) You can place a single potentiometer between the Source
pins of the Mosfets, where a good value is about 1 Kohm.

3) You can place a dual potentiometer as a resistive load at
the outputs (again 1 dual for each channel) to load the
current-source output, and here a good value is about 1 Kohm.

And of course any of these pots can be replaced by rotary
switches and resistors (use make-before-break contacts) or
relays and resistors.

And yes, small heat sinks are a good idea.
So if I were to use the gain control between the source pins of the 610 Mosfets like the original Aleph p 1.7 then just what exactly would be the lowest resistor wattage needed?

I am planning on putting 20 100 ohm resistors in series for 20 gain settings with relays and a multi-position make before break switch to control them in place of the original potentiometer. I can see that there is not a significent dc difference however I am not sure about what the AC is at here.

I was looking at 1/10 watt dales, will these be enough to handle the power at this location?
:D Ive got it!
How about I just use one of the original volume controls of the aleph P 1.7 for the 2k gain control! I would just have to take off the first two 8k and 4k resistors and replace them - on the other end - with 30.9 ohms and 15.48 ohms!
I think that this would work. :smash:
Then the only problem would be in making them make-before-break to avoid noise pops. I think that would be the ultimate though, 256 steps of precise gain adjustment. :eek: