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Stepped Attenuator or Volume Potentiometer

post #1 of 21
Thread Starter 
Hi,

I am planning on my next headphone amp that will double up as a preamp - the build costs will probably reach around $300 w/o chassis. So question is should I used stepped attenuators or a normal Alps Pot for the volume gain control.

I know that sometimes 23 steps is not enough resolution to control - esp since I listen at low volume, but I do want good quality sound too!

Options are:
1) Ebay Stepped Attenuator - Stepped Attenuator potentiometer ladder volume control - eBay (item 130186078671 end time Jan-03-08 23:37:47 PST) - about $30 (including shipping)

2) DIY attenuator kit from Australia using Vishay-Dale 1% resistors - DIY Fidelity
about $45 w/o shipping

3) Goldpt Attenuator Mini V (standard stereo) - Compare Attenuator Types - $149 w/o shipping

4) Just use a Alps Pot

5) Other Pots

6) Others means - e.g. Twisted Pear's Joshua Tree, Digital control etc

Opinions Please

thanks

her shann
post #2 of 21
Oh boy, another poll

TKD potentiometer (~$62) best bang for the buck without going stupid expensive (Alps RK50, P&G pot, DACT stepped attenuator, etc.)

I haven't used one, but would worry that 23 steps isn't enough without careful curve configuration. Alot of people have used them though.
post #3 of 21
Thread Starter 
Saw this thread in DIYAudio - Peter Daniels likes the PEC pots, currently available at Digikey - approx $30 for the stereo pot. Good sound but apparently channel matching may be a problem.

diyAudio Forums - So I did try all those different potentiometers

Hmmmm..., more choices.


her shann
post #4 of 21
Quote:
Originally Posted by hershann View Post
Saw this thread in DIYAudio - Peter Daniels likes the PEC pots, currently available at Digikey - approx $30 for the stereo pot. Good sound but apparently channel matching may be a problem.

diyAudio Forums - So I did try all those different potentiometers

Hmmmm..., more choices.


her shann
Yeah, I know PD likes those. Some people I've read view them as being colored, as in very tubey-sounding colored. They are a carbon pot, so that makes sense.
post #5 of 21
Quote:
Originally Posted by hershann View Post
Saw this thread in DIYAudio - Peter Daniels likes the PEC pots, currently available at Digikey - approx $30 for the stereo pot. Good sound but apparently channel matching may be a problem.

diyAudio Forums - So I did try all those different potentiometers

Hmmmm..., more choices.


her shann

I have PEC pot paid around $60 about a year ago. Well it sound not bad but the build quality I would expect a lot better for the money I paid.
Sorry no more PEC pots for me. Next pot will be TDK!

my 2c.
post #6 of 21
I have built three amps (headphone amps) so far using three different volume pots (Noble, Alps, TKD). I cannot really compare them because they sit in three different amplifiers, but to my ears the Noble (which probably is an older, detented one I got on eeh-bay years ago) is up on par with the TKD.
The TKD for sure has the highest quality overall including built quality and turns ever so smooth........!
post #7 of 21
I tend to use 10k Nobel pots, but that is just because I happened on a bunch for about 10% of the normal price. Otherwise, I probably would say Alps RK27, or TKD if you want something a bit nicer, though I havnt used one ever. Maybe Rk40, if you can find one. I have a few I got on close out for about $10, and the measured channel matching is definitely superior to the Rk27. I used a 23 step dact in the balanced M³ I built, and didnt care for it at all. Sound was fine, no complaints there, but I couldnt get the right volume level ever. If you were going for a bit higher budget, I would say digital controlled attenuator, but at $300, I tend to give a decent pot the nod. Call me crazy, but I would take one of my Nobels over a dact SA (well, take the SA, sell it, and buy oodles of Nobels).

My Nobel pots are 10k continuous rotation. Like the black ones PCX sells for $25.
post #8 of 21
both use the attenuator for big changes and the pot for small adjustment therfore avoiding the need for uber channel matching on the pot (which is very expensive!). As for the steped attenuator build your own and as you like low volumes adjust the scale acordingly.
post #9 of 21
Thread Starter 
Yes I could plan to adjust the stepped attenuator's scale - but sometimes it's quite difficult to know how the overall amp's gain and source impedance affects the final volume.

Maybe I'll just get one of the TKDs or Alps RK40?

her shann
post #10 of 21
I love my singlepower stepped attenuator. I voted for the goldpoint option as it was the closest.
post #11 of 21
another interesting aproach is the use of matched LED/LDR combos controlled by a single control voltage,hence just one pot
Thread discussing this so called Lightspeed Attenuator

Just wanted to mention it,
it's NOWHERE near a cheap solution as its quite difficult in the end to control the impendance , and you amp needs to have an input impendance around 100K

i wouldn't want to rely on 23 steps
post #12 of 21
Quote:
Originally Posted by cetoole View Post
I tend to use 10k Nobel pots, but that is just because I happened on a bunch for about 10% of the normal price. Otherwise, I probably would say Alps RK27, or TKD if you want something a bit nicer, though I havnt used one ever. Maybe Rk40, if you can find one. I have a few I got on close out for about $10, and the measured channel matching is definitely superior to the Rk27. I used a 23 step dact in the balanced M³ I built, and didnt care for it at all. Sound was fine, no complaints there, but I couldnt get the right volume level ever. If you were going for a bit higher budget, I would say digital controlled attenuator, but at $300, I tend to give a decent pot the nod. Call me crazy, but I would take one of my Nobels over a dact SA (well, take the SA, sell it, and buy oodles of Nobels).

My Nobel pots are 10k continuous rotation. Like the black ones PCX sells for $25.
Funny, I don't have any trouble getting the level I want with a 23 step dact in a balanced M3...
post #13 of 21
post #14 of 21
Quote:
Originally Posted by grawk View Post
Funny, I don't have any trouble getting the level I want with a 23 step dact in a balanced M3...
Good, very glad to hear that .
post #15 of 21
I can't imagine having trouble getting the volume setting you want with 23 steps. If you're concerned about that, then put an inexpensive pot in the circuit, measure the resistance at the volume you like, then build the attenuator. You can always design for closer steps around the levels you like. I use 12-position rotary switches to build the VoltSecond S5 and don't have any trouble getting an acceptable volume setting. When I'm lazy, or not sure if I'll keep the amp, I use an Alps.
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