software based volume control?

[earwaxer9]

Ok, I may be stretching things a bit! - I'm looking to replace my method of volume control in my system. Currently using passive, Alps Blue Velvet with the t-amp. I want to stay passive and relatively cheap! I thought about passive LDR (optocoupler), autoformer (intact audio), and a stepped approach.

Since I'm using a computer, why cant I control the volume in software without any degradation in resolution etc? I know that my Transporter has a digital volume control but that does not appear to perform as well as my Alps pot. Any info would be much appreciated!

[SuperQ]

Ok, I may be stretching things a bit! - I'm looking to replace my method of volume control in my system. Currently using passive, Alps Blue Velvet with the t-amp. I want to stay passive and relatively cheap! I thought about passive LDR (optocoupler), autoformer (intact audio), and a stepped approach.

Since I'm using a computer, why cant I control the volume in software without any degradation in resolution etc? I know that my Transporter has a digital volume control but that does not appear to perform as well as my Alps pot. Any info would be much appreciated!

So there really isn't any problem with software volume control. This has been discussed in-depth several times in the forums.

The fact of the matter here is that the volume control is done in 24bits by software. This means that any mathematical bit errors are in the -130dB to -140dB range. Since the Transporter's analog DAC section is at best -120dB SNR, it can't even reproduce these bit errors.

But if you've got the volume turned way down to like 20%, you have lost a lot of signal and are going to be boosting a lot more of the noise floor at the amp.

What you really want is to reduce your amp's gain or apply a passive attenuation (simple resistor network) to limit the max volume of your system.

http://wiki.slimdevices.com/index.ph...ve_attenuation

[earwaxer9]

Thanks for the input SuperQ - I have been thinking about using the top end of the Transporter digital volume control. It makes sense that bits off the top of the 24bit dont make a real difference in terms of the noise floor. I also thought about running my Alps at full volume and setting the jumper in the Transporter to -30db. Then I could use the top end of the volume control to tweak the volume.

[SuperQ]

Thanks for the input SuperQ - I have been thinking about using the top end of the Transporter digital volume control. It makes sense that bits off the top of the 24bit dont make a real difference in terms of the noise floor. I also thought about running my Alps at full volume and setting the jumper in the Transporter to -30db. Then I could use the top end of the volume control to tweak the volume.

Oh, yea, I completely forgot about the jumper in the TP. (I use balanced, doesn't work for that)

With the jumper you could just plug directly into an amp and not have a pre-amp at all.

[earwaxer9]

Just finished another attempt at using the internal jumpers on the Transporter. Confirmed. - I tried the jumpers some time ago and wasnt impressed. I switched the jumpers in the Transporter to -30db and cranked the volume on my amp to max. The volume was low, even at max on the Transporter digital volume control. Kind of background low level listening. The sound was somehow not engaging. Flat, 2 dimensional. Hard to describe. Same thing that I experienced a couple of years ago when I tried it. Thats when I decided that the Alps was plenty good enough. Of course, being an incurable audiophile, I cant leave it at that! Itch, yet unscratched!

[darrenyeats]

Just finished another attempt at using the internal jumpers on the Transporter. Confirmed. - I tried the jumpers some time ago and wasnt impressed. I switched the jumpers in the Transporter to -30db and cranked the volume on my amp to max. The volume was low, even at max on the Transporter digital volume control. Kind of background low level listening. The sound was somehow not engaging. Flat, 2 dimensional. Hard to describe. Same thing that I experienced a couple of years ago when I tried it. Thats when I decided that the Alps was plenty good enough. Of course, being an incurable audiophile, I cant leave it at that! Itch, yet unscratched!

If the -30db jumpers are too quiet at 100% then they are the wrong jumpers. Loud sounds better all else being equal: for me no further explanation is required for the flat sound.

Ironically a TP at 100% with no other volume control in the signal path is the highest fidelity situation possible. Below 100% SNR is lost. But you will need the appropriate gain (jumper) to judge this properly.
Darren

[Mnyb]

atenuation should be done so that 100% volume corresponds to how loud you ever want to listen.

before i got my present speakers , I used inline atenuators before the poweramps except one of them had selectable selectivity ( wich i think all power amps should have ).

This was a much better match for my preamp/processor .

as you have a passive pot you could use it to tune in a suitable damping and then use the TP's volume .
or a combination of both .

potentiometers, they are not so linear in the low range channel tracking could be bad at that end, here a stepped solution could improve.

This where jumper + digital volume is an improvement you would always have the same volume in rigth and left channel .
with very good pots as the alps this is less obvius, better tolerances but at a price.

[earwaxer9]

thanks for the thoughts guys!