Stepped Attenuator v. Potentiometer

[Balisarda]

Hi all,

Can anyone tell me how a stepped attenuator is superior to a potentiometer as a volume control? Is it only in matching signal strength across channels? Or is it also in preserving signal fidelity?

Ultimately, I'd like to know: would a given amplifier sound better with a SA than with a Po?

Thanks,
Eric.

 

[angler31337]

Quote:

Originally Posted by Balisarda /img/forum/go_quote.gif Can anyone tell me how a stepped attenuator is superior to a potentiometer as a volume control? Is it only in matching signal strength across channels? Or is it also in preserving signal fidelity?

You'll need an engineer if you want a technical answer. The best I can say is that pots creates small amounts of signal distortion as an artifact of their design. To my ears, a pot introduces a small amount of "muddiness" relative to a SA. Pots are continuous, however, and so in my mind really shouldn't be compared too directly to SA's which are by design discrete.

Quote:

Originally Posted by Balisarda /img/forum/go_quote.gif Ultimately, I'd like to know: would a given amplifier sound better with a SA than with a Po?

Well, that depends a lot on the quality of the amp. I can't imagine you would perceive any difference between a pot and SA when controlling the volume of a standard CMOY. Also remember that there are good pot and bad SA designs. (c.f. the $1k Alps pot)

-Angler

For an English page regarding the Alps pot, see http://www.headphone.com/products/he...ions/alps-pot/.

 

[nikongod]

Quote:

Originally Posted by angler31337 /img/forum/go_quote.gif Well, that depends a lot on the quality of the amp. I can't imagine you would perceive any difference between a pot and SA when controlling the volume of a standard CMOY. Also remember that there are good pot and bad SA designs. (c.f. the $1k Alps pot)

once we get into the ranges upwards of $500 for a full range pot, we should probably look at stepped attenuators with more than 24 steps. this eliminates Many of the downsides to the "steppynes" of the stepper.

as far as differences: you have the benefits of channel matching, resistor brand/type selection, and you also have the benefit of controlling the range and slope.

people who complain about only using the first 1/3 of the steps on a 24 step stepper should get a re-sloped one. where the first say 20 steps are the first 1/3 of a standard stepper, and the rest goes higher. ask for say: -60 to -20dB instead of -60 to 0dB. maybe even start at -65 or 70dB.

 

[MASantos]

General rule is that stepped atteenuators are better than potentiomenters.

They provide less degradation of the signal and better sound quality.

That said, Headroom uses a special 1000$ potentiometer in their top-of-the-line amplifiers.

 

[Konig]

Quote:

Originally Posted by MASantos /img/forum/go_quote.gif General rule is that stepped atteenuators are better than potentiomenters. They provide less degradation of the signal and better sound quality. That said, Headroom uses a special 1000$ potentiometer in their top-of-the-line amplifiers.

$1000???

i thought the $599 euro one by lessloss is expensive already

 

[edisonwu]

It doesn't cost 1000USD. The price may be for one pair in a balanced amp. I'd rather go stepped in this case as I control all 4 phase sections in ONE attenuator.

 

[nikongod]

Quote:

Originally Posted by edisonwu /img/forum/go_quote.gif It doesn't cost 1000USD. The price may be for one pair in a balanced amp. I'd rather go stepped in this case as I control all 4 phase sections in ONE attenuator.

they charge $1000 for a 4-channel pot to upgrade one of their amps.

it is one 4ch pot, not 2 2ch.

 

[edisonwu]

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif they charge $1000 for a 4-channel pot to upgrade one of their amps. it is one 4ch pot, not 2 2ch.

If I don't make mistake, the picture from headroom is a 2ch RK50.
http://www.headphone.com/products/he...ions/alps-pot/

http://www.headphone.com/images/alpsback.jpg
100K*2

If anyone has a picture of a 4-ch RK50, I would like to see and take it.

 

[Frihed89]

10 years ago, there were not many attenuators around and everyone was using pots. The attenuators were uper high quality and the pots had many different quality levels. Now, Alps is about the only mfr left that makes a super-high quality pot (and very expensive) and there are many quality/cost levels for attenuators. The best I have heard are made by SHallco and Audio Note. Gold Point is mid-price.

 

[nikongod]

Quote:

Originally Posted by edisonwu /img/forum/go_quote.gif If I don't make mistake, the picture from headroom is a 2ch RK50. http://www.headphone.com/products/he...ions/alps-pot/ http://www.headphone.com/images/alpsback.jpg 100K*2 If anyone has a picture of a 4-ch RK50, I would like to see and take it.

the last line of that, which is a photo of the 2-channel variant is this:
Quote:

Originally Posted by headroom In fact, Alps tells us we are the only people to ever buy the quad version that is the Max Balanced potentiometer upgrade.

 

[n_maher]

Quote:

Originally Posted by edisonwu /img/forum/go_quote.gif If anyone has a picture of a 4-ch RK50, I would like to see and take it.

What, like this one?

All of Headroom's current production amps use a single volume knob so in no case will you find them using 2, 2-channel steppers or pots to control the volume. You've either not a 4-channel pot or a 4-channel stepper in the current line.

And nikongod, Headroom does use a 4ch RK27 in both the Balanced Home amp and the new Balanced Desktop, I just can't find a picture of it anywhere.

 

[nikongod]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif And nikongod, Headroom does use a 4ch RK27 in both the Balanced Home amp and the new Balanced Desktop, I just can't find a picture of it anywhere.

i know.
if you want to see a 4-ch rk27 crack open a srm-717/srm-007t
do they offer balance control? that would be sweet.

 

[Balisarda]

Thanks for the information, Angler, Santos, and Frihed!

 

[Frihed89]

Yes that is the ALPS Rolls Royce pot. I don't remember the price, but it was mile-high. I saw only the technical drawings. These are nice pics.