Ordered Crack today -- and restricting volume to protect headphones

[Grainger49]

galyons, that's disappointing 
Thanks JamieMcC, that's the solution I will use  if no one will post a better solution. Where I can buy it for the Crack? What's the name for this knob (diameter) so I can find a German dealer here.

The volume pot acts as a voltage divider.  The incoming voltage, let's call it 2V, is across the whole volume pot resistance be it 10k, 50k or 100k.  The wiper changes the ratio of voltage dividing.

What Paul Birkeland suggests is a series resistor for each channel which limits the voltage fed to the volume control.  So if you have 2V coming in you can cut that to 1V maximum on the volume control, or 1.5V maximum, or 3/4V maximum, you get the picture.

[free]

Ah, ok, hm I might try that out. So I would just add two (one per channel) 50k or so resistors and that would work? If it works with such low voltages then this must really work Most resistors are for that kind of low voltage 

[JamieMcC]

Is this the same procedure as adding the resistors in line with the RCA as per in the Crack sticky section but using a much higher value? If so it is very easy to do.

[Grainger49]

Yes, it is a logarithmic function.  A 100k in series will cut the volume by 3dB. 

I would suggest listening to the lowest recorded music you have and determining the highest volume level you want to listen to.

Then turn the Crack off and measure the resistance from the input to the wiper and from the wiper to ground on one of the channels.  This gives you the ratio of resistance that you need.

Post this back and we can suggest a proper value for the series resistor.

Yes, it is the same thing as in the sticky.

[free]

Thanks I'll do that. Can take some time until I receive the Crack, ordered just today.

[JamieMcC]

Yes, it is a logarithmic function.  A 100k in series will cut the volume by 3dB. 

I would suggest listening to the lowest recorded music you have and determining the highest volume level you want to listen to.

Then turn the Crack off and measure the resistance from the input to the wiper and from the wiper to ground on one of the channels.  This gives you the ratio of resistance that you need.

Post this back and we can suggest a proper value for the series resistor.

Yes, it is the same thing as in the sticky.

AH HA super this is much clearer to me now and I now know how to measure for wiper resistance. Which I didn't prior to your post thank you.

[JamieMcC]

OK this should help a picture example of resistors added inline with the RCA left and right channel inputs this should make it much clearer as you have not yet built your Crack. Sorry about the poor pic it was rather warm and I only my old camera to hand which doesn't focus to well.

(https://www.head-fi.org/image/id/5497829/width/900/height/900/flags/LL)

[Paul Birkeland]

Ah, ok, hm I might try that out. So I would just add two (one per channel) 50k or so resistors and that would work? If it works with such low voltages then this must really work Most resistors are for that kind of low voltage 

No, no, no.  As I keep saying, you can't protect your headphones without having some idea of how much limiting you need to do.  50K resistors will knock you down 3.5dB, but we have no way of knowing if that's enough, or too much!

The bolt idea is a good one.  You can always loosen the knob on the volume control to adjust its mounting position and fine tune the setting.

[free]

Thanks JamieMcC for the picture, this helps.

Caucasian Blackplate, I would of course have tested if this ohmage would be enough (there will be one DAC to which the Crack will be connected, not any other so that can be sorted out, but the bolt solution wouldn't help on this source problem either)
Bolt idea is not bad either.

[Doc B.]

I don't get the sense that the HD600 ever gets so loud that it could be damaged by a Crack. It's the low impedance cans that can blast really loud with the Crack. But to do what you want you are looking for a 300 ohm variable L Pad at the output to waste output power. You will have to make one, they aren't readily available. Or you could just put a big resistor in series with the headphone jack T and R pins, like a 600 ohm 5 watt.

I'm not saying it will sound good, but it will save you from having to ask people to be careful with your gear. I would instead be inclined simply to not let people use your gear whom you can't count on to be careful with it.

[free]

I'm not going to build my own 300 ohm variable L Pad, but I'd be happy with a simple resistor solution. Interesting that you suggest to put the resistor at output. I read that a resistor can lower the sound quality, is this true for Crack? (oh indeed you're saying this too? "I'm not saying it will sound good") Otherwise I'd chose the bolt solution.

"I would instead be inclined simply to not let people use your gear whom you can't count on to be careful with it."
This is out of the question since the people can be my family members They/or visitors are (already) careful with gear but you know one can forget(at certain age)/not know not to use headphones as speakers

[free]

So, Doc, if the resistors will lower the sound quality (you don't need to reply if this is true) I'd go with the bolt solution.

[Doc B.]

The answer is that it might lower the sound quality, or it might not. You would have to try it. The stop for the volume control could work for one source. At least until you find a recording that has such a low level that the stop won't let you turn the volume up enough for that song. It's diificult to know what the ideal position would be without quite a bit of trial and error.

[free]

Thanks. Yes know is not perfect but fortunately it'll only be the HD600.