Why should someone build volume pot?
Mar 9, 2007 at 3:35 PM Thread Starter Post #1 of 9

polumenta

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Hello,
I'm new to making heaphone amps and I wonder what use of volume pot when you can control your volume by your soundcard or iPod?

If there is no any good reason, can you please tell me what should I do to make PIMETA without volume pot? Should I change some resistor values, or just bypass volume control, and that's all?

cheers
 
Mar 9, 2007 at 3:38 PM Post #2 of 9

stewtheking

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True you can control levels from your soundcard or iPod, but then you are entirely restricted to these devices, if you buy a CD player, then you will be stuck with it at u nan changeable volume. Far better to just stick in a pot (they aren't entirely bank-breakingly expensive) and then you have far more flexibility.
 
Mar 9, 2007 at 8:09 PM Post #3 of 9

AndrewFischer

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The short answer is you don't have to. DIY means you can build your amp the way you want it.

You do need to get the gain right. If you are using the amp with more than one device you may need to have switch selected gain to allow for full volume from all your sources.
 
Mar 9, 2007 at 9:01 PM Post #4 of 9

roadbuster

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Quote:

Originally Posted by polumenta /img/forum/go_quote.gif
Hello,
I'm new to making heaphone amps and I wonder what use of volume pot when you can control your volume by your soundcard or iPod?



It's just a handy volume control so you don't HAVE to adjust the soundcard/iPod.

Quote:

If there is no any good reason, can you please tell me what should I do to make PIMETA without volume pot? Should I change some resistor values, or just bypass volume control, and that's all?


Looking at this schematic:

http://tangentsoft.net/audio/pimeta/misc/schematic1.pdf

Replace the VOL potentiometer (first page, left side) with a single resistor between the signal input (IL/IR) and C1. The resistor should be somewhere in the range of 5 to 25Kohm, depending on how loud you want the output of the amplifier to be. Tinker with a few values and see what you like.
 
Mar 9, 2007 at 10:28 PM Post #5 of 9

Garbz

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The computer sound card (the ipod one too??) works in the digital domain. The downside is when you turn the sound down in digital for every 6dB reduction (halving of the volume) you sacrafice one bit. So if you listen to you music down at 1/8th of full volume (not uncomming considering the high output of these devices) you really only get 12bit music.

For a fun test take the volume in foobar or some other media player down very quiet, and turn your amp up really loud. The result (asside from being noisy) will most likely sound anemic, undetailed, and all around poor.
 
Mar 11, 2007 at 3:30 AM Post #6 of 9

seanohue

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Also, when you control the volume through the pot on the amp, it takes the some off the load of source i.e. if you play the ipod at 75% volume instead of 90%, the ipod wont use as much battery power to sustain the louder volume.
 
Mar 11, 2007 at 4:49 AM Post #7 of 9

DaKi][er

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Quote:

Originally Posted by seanohue /img/forum/go_quote.gif
Also, when you control the volume through the pot on the amp, it takes the some off the load of source i.e. if you play the ipod at 75% volume instead of 90%, the ipod wont use as much battery power to sustain the louder volume.


That is going to be so insignificant it isn't funny, the temperature of it is going to have more effect that that
 
Mar 11, 2007 at 2:06 PM Post #8 of 9

mono

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We use volume pots on Pimeta because it would be considered a higher magnitude of overkill to use a stepped attenuator for that.
very_evil_smiley.gif


People like control, it's just not as pleasing to spend the time and money on a device with only one button to press (on/off), plus you might have a better POT in your Pimeta (if you choose to) than on your source, so setting the source high and leaving it alone instead of wearing it out will allow higher SNR to get to the headamp, and a better POT to (theoretically) degrade sound less and provide a more linear (log) audible volume increase. Of course this is overgeneralized, it depends on the source and pot too.

If you think you don't need a POT, don't use one. You can always add it later.
 
Mar 12, 2007 at 7:42 AM Post #9 of 9

lordvader

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As far as digital volume goes, what level should you be using such that the bits aren't modified (essentially turning your sound card into a line level out).

I recall somewhere that you should leave it at 75%, does that mean bits are added (or modified) at 100%, or is it just that at 100% you're really running the card at its limits ?
 

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