best option for pot/stepped attenuator?

[adamct]

Thanks, Jim. That is a very helpful (and complete) response. My DAC has a very strong output signal (even on the low setting), so I suspect you are right that the stepped attenuators would not be a good choice for me. I certainly don't have the patience to create a custom Goldpoint.

The means I need to decide between the PRC and the TKD. I'll think it over this weekend. I appreciate your help.

Best regards,
Adam

[Jim R.]

Adam,

I can tell you that both are very nice -- the TKD is a bit more transparent, and some of the PECs tend to be a bit scratchy at the low endof their range.  To get the best out of each though, I'd strongly recommend looking at the "getting more steps" tutorial on the goldpoint site -- this applies to non-stepped attenuators too and it will let you get far more usable (and also put the pot in the region where it sounds it's best) simply by adding 4 resistors -- 2 to each channel.

Once my Crack is rebuilt I'm going to do this after making some measurements with my source (2v standard dac output level.)  Yes, the pots sound best when they are at normal listening levels somewhere around 12:00 and worst at their extremes.

-- Jim

[earwaxxer]

Not to be a fly in the ointment on this, but IMO, the pot is of relatively minor importance once you get into the 'good' pot category. I'm sure many will disagree with that hypothesis, but if you want to absolutely sleep ok at night in regards to the pot, I would go with stepped resistor, and build it yourself.

I think the fish is better fried from a 'holistic' approach. In other words, you may be better served by addressing your cabling/wire in addition to your pot. For example, I have realized MUCH more benefit from focusing on my interconnects. Just a suggestion. I do agree with the TKD choice over the Alps. YMMV.

[porcupunctis]

Don't forget the Khozmo attenuater.  48 steps give you more than enough volume choices.
http://www.bottlehead.com/smf/index.php/topic,2336.0.html

[Jim R.]

Not to disagree with Eric, but I've tried all kinds of volume controls -- beyond pots) and I still think the best one is none at all.  In other words, it's always a compromise -- basically, pots suck, but they are a necessary fact of life (in some form or another unless you go with a very good digital control using an advanced and well-executed adithering algorithm.

This can be fantastic, but as good as they are, they also make me nervous as if for some reason your digital link loses sync, your amp will most likely blast you and your speakers at full volume white noise.  Of course thee ways around this too, but more circuitry and probably just another thing to rob the amp/system of it's absolute "purity".

We're now starting to see more direct from digital to amp systems -- amps that take a digital spdif or usb input and with everything done in the digital domain and then what one could call a "power dac" for the output.  Right now these things tend to be ultra expensive or only so-so in performance -- certainly not the claims of perfect audio that some people make about them.  And of course if you want to use an analog front end, well, you'll have to turn it into bits before you listen to it anyway, and what's the point of that? :-)

-- Jim

[earwaxxer]

Hey Jim - I totally agree. Thats the set up I'm listening to now. - No pot. All volume control is done in the digital domain in 24bit. Despite the naysayers, I have not found a significant negative, at least in terms of the Logitech Transporter that uses the AK4396. I'm happy as a clam. But, what I can say, is that I have compared the sound from some of my kit, with and without pot and have not found a huge difference. I can do this using my DAC as a preamp.

What I found, for example, was that my system sounded MUCH better going balanced vs. single ended. I was surprised. Its cool though. Whatever works, even though I have shelled out some significant cash for RCA interconnects. We audiophiles have to pick our battles carefully. Live and learn.

[2wo]

I agree with Eric about the digital volume control. As long as I am using the top end of the scale,  I  think it sounds  better than a pot...john

[Grainger49]

If you decide to do it yourself you must read this page:

http://www.siteswithstyle.com/VoltSecond/12_posistion_shunt/12_Position_Pure_Shunt.html

There is a spreadsheet you can download, select your number of steps, step size and it calculates the resistors needed.

VoltSecond is a long, long time Bottlehead.

[adamct]

Ugh. I just tried installing a TKD volume pot. Frankly, it was an enormous PITA. A really, really frustrating and fiddly experience. I followed the wiring diagram at the top of this page: http://www.partsconnexion.com/controls_pot_tkd.html

I finally get everything set up, then hook the Crack back up to test it out. I get BLARING volume out of my headphones, even though the volume is turned down all the way.  When I turned the volume knob, it appeared as though it was just changing the left/right balance, but not the volume. This is what it sounded like, without the headphones on, at least. I didn't dare to actually wear the headphones, and with the volume so high, it is hard to try and isolate one side of the headphones to test it out.

Did I make a mistake in following the diagram I linked to? Should I have just wired it up like the stock pot? I remember reading somewhere that there is a guide on how to tell how your volume pot is wired, but after much searching before I embarked on this fiasco, I couldn't find it.

I note that the diagram linked to above shows the left/right channels wired in opposing directions: I.e., the left channel is ground-out-in, whereas the right channel is in-out-ground. This is contrary to the markings on the pot itself, which showed the solder terminals on the lower deck as 2-1-C and the upper deck matched those markings, so that 2 was above 2, 1 was above 1 and C was above C.

Please tell me what I did wrong and how to fix it...I'm feeling very frustrated, as you can surely tell. Many thanks in advance!

Best regards,
Adam

[Paul Birkeland]

It is incredibly rare that a volume pot differs from the stock pot in the Crack in terms of connections.

[adamct]

OK, thanks. That's what I get for not asking first....

[adamct]

Fixed. Thanks again for the quick response!

[Paul Joppa]

The figure at the top of the referenced page says "Typical Balance Pot Wiring" - but ALL of the pots on the page are VOLUME pots, not balance pots. (A balance pot would normally be linear taper.) Perhaps you could email Parts Connexion and "call their attention" to the problem!

[rs01]

Are the majority of the potentiometers drop in replacements in terms of the cut-out on the mounting plate or is there a bit of Dremel work involved?  I'm considering adding a 100k Blue Velvet along with the Speedball that I should have in next week.

[adamct]

Don't know. I had to widen the hole a tiny (and I mean tiny) bit to fit the TKD. I picked up some sort of grinding bit at Home Depot for $3.50. Worked like a charm.