Replacing the standard pot with a stepped attenuator?

[loz_the_guru]

Hi all,

I've had my crack up and running for a month or so now, and fancy swapping the standard for a laddered attenuator. Can anyone tell me how complicated the process is, and also if I need a 10k or 50k version? There's quite a few on ebay:

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=ladder+attenuator&_sacat=0

Any real differences between them?

Thanks!

[Tom-s]

The recommended attenuator for Crack is a 100k stereo log ladder type stepped attenuator.
I've used the Valab stepped type with good results.

[loz_the_guru]

The recommended attenuator for Crack is a 100k stereo log ladder type stepped attenuator.
I've used the Valab stepped type with good results.

Thanks. Out of curiosity, what does the resistance level do? I usually have my crack under a quarter turned at the moment, as with my HD700s its otherwise just too loud!

[Paul Birkeland]

The impedance of the attenuator has nothing to do with levels.  A 50K attenuator and a 100K attenuator with both pass the same amount of signal into the amp when turned all the way up (assuming you don't have a source with very high output impedance, which is a very reasonable assumption these days). 

The Crack circuit works pretty nicely with a high impedance level control like the 100K pot we provide, and 100K is a very easy load for sources to drive, so that is what we use. You could use a 50K control and you likely wouldn't notice any difference.

-PB

[Tom-s]

Thanks. Out of curiosity, what does the resistance level do? I usually have my crack under a quarter turned at the moment, as with my HD700s its otherwise just too loud!

As Caucasian blackp.. wait PB said (did someone decide for a name change?? ) the impedance doesn't change the sound level.
But FAQ #3 (look it up) does. Thing is. This is meant to go with a 100K log. Tell us what impedance you went with and then the resistances for FAQ#3 can be calculated based on that.
This change makes that you get more useful range of your attenuator with your HD700's.

Edit: Link https://bottlehead.com/smf/index.php?topic=4295.0

[Jamier]

PB, where is Caucasian Blackplate and what have you done with him?

Jamie

[Paul Birkeland]

PB, where is Caucasian Blackplate and what have you done with him?

IDK, I think perhaps old Doc B is trying to make it easier to herd the Pauls.

[loz_the_guru]

As Caucasian blackp.. wait PB said (did someone decide for a name change?? ) the impedance doesn't change the sound level.
But FAQ #3 (look it up) does. Thing is. This is meant to go with a 100K log. Tell us what impedance you went with and then the resistances for FAQ#3 can be calculated based on that.
This change makes that you get more useful range of your attenuator with your HD700's.

Edit: Link https://bottlehead.com/smf/index.php?topic=4295.0

This is fantastic, thanks! I'd always assumed there was little I could do but this will make my life much easier.

I've gone for the 50k attenuator as I can't seem to find a 100k one readily available anywhere (unless someone can point me in the right direction?).

One question on the volume resistor mod - I plan on eventually upgrading to some HD800sm with have a much higher impedance (300 vs 120). Presumably if I do this it's simply a case of reversing the resistor mod?

Thanks all!

[Tom-s]

Yes. It's reversible if needed.

[Paul Birkeland]

Headphone impedance will not on its own require the removal or installation of the resistor mod to the attenuator.