replacing mono volume controls with single stereo one ?

[denti alligator]

How would one go about replacing the two mono stepped attenuators with a single stereo one similar to what's on the SEX amp? What would be the disadvantages of going this route?

[Grainger49]

They wire much the same as the stereo pot on the SEX amp.  You will find that adjusting stereo volume is easy.  The only drawback is sometimes at the lowest 1/4 of a turn left and right don't track exactly.  Not that you lose a channel, just that a centered vocalist will wander a little right and left till you get to about 8:00 on the dial.

How to figure out wiring a volume pot will be added to the FAQ Thread.  Since not all pots and attenuators are lugged the same way. 

[denti alligator]

Thanks, Granger. So why the odd l/r problem at the low end? And can that be fixed somehow?

What would I need to buy? the same pot that the SEX uses?

I imagine I could move the selector switch to the left or right spot and have the stereo volume pot opposite it, for symmetry's sake, at least.

I don't even have the FP yet, just thinking about it how I'd like to use it. I'd still like to demo someone's unit (hint hint), though I imagine that unless someone in the central PA area has one that is unlikely. In which case I may just have to save up and go for it.

[Paully]

Grainger helped me wire up a volume pot and we used the vacant spot for a balance pot.  Worked well.

[denti alligator]

Grainger helped me wire up a volume pot and we used the vacant spot for a balance pot.  Worked well.

Even better!
Now I'm excited. How does it sound compared to stock?

[fullheadofnothing]

You asked about disadvantages. A couple readily spring to mind. First is the stock attenuators sound pretty great, and you'll have to spend a lot to improve on them, especially if you want to go for a potentiometer. You also lose independent control over the channels, which is really helpful for trouble shooting (for example, if your system is making a weird noise, you can track down which channel it is and where in the chain much faster and easier with dual controls, since you can kill a channel at the preamp without unplugging anything).

When I first got my FPIII, I thought I was going to hate having dual volume controls and having them as switched attenuators rather than pots. After a little time with it in my system, I realized that was just fear of the unknown. I now consider the volume setup the nicest feature of the preamp

[denti alligator]

Joshua, do you control the volume on your FP or on your SEX? Isn't it ideal (signal-to-noise) to control from the FP? But then the stepped attenuator doesn't seem so ideal for setting the volume just where you want it, since you can't make small adjustments.

[fullheadofnothing]

Lately I've been going straight into S.E.X., but that's because all my 12AU7s are a bit noisy and I was doing a lot of headphone listening. When rocking the combo, I set the S.E.X. control about a third of the way up and my normal listening level is about midway on the FP. That gives me the ability to crank it if need be or turn down for courtesy. As for not being able to adjust "finely," in my experience that's a red herring. The steps are just about right in my book, especially if you can tweak it so your standard level is in the middle (the lowest settings have a slightly bigger jump).

[Grainger49]

Thanks, Granger. So why the odd l/r problem at the low end? And can that be fixed somehow?  .  .  .    

A 100k volume pot is 100k at maximum volume setting.  The early range can be, but isn't always, not "applied" reliably.  To get rid of the problem use a larger dropping resistor before the volume pot.  This will get the volume pot above that small non-linear area before you typically use it.  If you are not using most of the volume pot you don't have a usable range.  My control goes from just below 9:00 to past 3:00 for my listening.

[Paully]

I found the stereo pot and the balance pot to be very convenient.  If there was a degradation in sound I didn't notice it.  My two cents.  I suppose the need for it was alleviated with the clickability of the stepped attenuators versus the continuous pots that were in the FPII but I like having the single control regardless and I never actually have had to engage the balance pot.  Anyway, I like it.  I can take a picture of the hook-up in the FPIII though I don't know how helpful that will be.

[Laudanum]

I still havent even padded my FPIII for the different sources.  It's still only feeding Crack.  If I ever make room, I will add one of my amps and a speaker pair and then see.  But right now, I just leave the mono controls at 12 O'clock for the CDP and Digital player and usually a click or two beyond for LP and use the Crack volume pot.   Ive tried all different combinations of FPIII attenuator positions and volume pot positions on Crack and cant hear a flippin bit of difference in SQ so, right now, that's how I use it.   Seems Im generally using between 10 O'clock and 2 O'clock on the Crack pot (pun intended  )  which makes sense.  That's about the range I used before FPIII (not including turntable) and middle position of FPIII attenuators is supposed to be about unity.   Obviously there are a few ways to use the FPIII attenuators beyond what may be considered the concensus "best" way.  As long as my ears dont hear a difference, I just keep using the Crack pot (there I go again  and goosing the FPIII attenuators a click or two for most LP's.  It's also easily the most convienent for me because Crack is within easy reach from the lazy chair.