Because I need a master volume control for all my digital sources, as none of them offer volume control by themselves.
The master volume in the miniDSP can't be accessed without hooking it up to the computer, and using the software, which is pretty inconvenient...
Does miniDSP accept 20 or 24bit input from its digital ins? If not then putting the volume control prior to a 16bit wide pipe is going to lose you significant dynamic range.
I was thinking that a very easy way to do the switching is to use a series of optical splitters, but in reverse. Still doesn't sort out the volumec control issue - could that be handled by programming an Arduino? I don't know what kind of interface the miniDSP accepts so just clutching at straws here...
I was thinking that a very easy way to do the switching is to use a series of optical splitters, but in reverse. Still doesn't sort out the volumec control issue - could that be handled by programming an Arduino? I don't know what kind of interface the miniDSP accepts so just clutching at straws here...
I think the miniDSP can do the job without the computer attached. I have an old miniDSP kit from the first generation and on this one it works with a simple 10k linear potentiometer and the function enabled in the software. Maybe you can ask the question in the miniDSP forum but I'm pretty sure master volume feature is described in the user manual.
Does miniDSP accept 20 or 24bit input from its digital ins? If not then putting the volume control prior to a 16bit wide pipe is going to lose you significant dynamic range.
I was thinking that a very easy way to do the switching is to use a series of optical splitters, but in reverse. Still doesn't sort out the volumec control issue - could that be handled by programming an Arduino? I don't know what kind of interface the miniDSP accepts so just clutching at straws here...
I'm not sure. The board itself is based on a 28bit resolution.
Using an Airport Express, I achieve very good sound quality tho, with volume being done from the airplay source (macbook pro in this case).
I've tried the potentiometer solution, and I'm afraid to say it's rubbish for my application (High-efficiency speakers). The minimum potentiometer volume is way to loud, and adjusting the master volume in the miniDSP to compensate, severely limits the maximum potentiometer volume.
Haven't built it yet but...
It is tricky dealing with gain-management here. You want to keep all your bits. Sensitive amps and speakers are a curse because they play all the noise and dirt on the floor.
My solution is to run digital elements full-blast and have a 4-channel ganged volume control after a Behringer DCX2496 and just before my analog amps. No hit to S/N that way.
BTW, another good move is to input to a DCX using SPDIF/coax - keeps things digital and skips over early DCX stages.
Ben
It is tricky dealing with gain-management here. You want to keep all your bits. Sensitive amps and speakers are a curse because they play all the noise and dirt on the floor.
My solution is to run digital elements full-blast and have a 4-channel ganged volume control after a Behringer DCX2496 and just before my analog amps. No hit to S/N that way.
BTW, another good move is to input to a DCX using SPDIF/coax - keeps things digital and skips over early DCX stages.
Ben
Umm, volume control pots degrade SnR through addition of their Johnson noise. The impedance where the pot's noise contribution equals that of the DAC and its buffer varies with implementation details but in better designs is usually a few k. Probably about 10k for the DCX2496, meaning around a 3dB SnR penalty for following with a typical 10k pot---more if the pot is a higher value. Depending on how the pot is employed other degradations may also apply.
As to the OP's question the optimal solution is to reduce power amplifier gain. A fixed voltage divider (lpad) can also work fairly well if carefully implemented within the power amp. As a turnkey solution a good number of audio interfaces offer standalone mix capability.
As to the OP's question the optimal solution is to reduce power amplifier gain. A fixed voltage divider (lpad) can also work fairly well if carefully implemented within the power amp. As a turnkey solution a good number of audio interfaces offer standalone mix capability.
It is always good to see that kind of analysis although I have no skill to confirm or disconfirm it. My initial gut feeling is the noise from a pot is not comparable to the degradation of running a DCX with just one LED blinking... on peaks.
And as for "reduce power amp. gain", that involves either more pots, fussing dangerously with feedback loops, or other steps which might be a lot more pain in the ear than a familiar pot after the DCX.
Ben
Wikipedia's page on Johnson noise is a good introduction if you're interested there. Depends on the level meter implementation but a one LED indication is usually -20 to -40 dBFS. Substantially more than 3 dB, yes, but the thing is implementing the same attenuation with a 10k pot rather than digitally would result in a 23 to 43 dB SnR reduction rather than 20 to 40 dB. See the gain structure article here on DIY Audio for more.
Amplifier design process doesn't vary much as a function of the gain selected; Tim Green's series on op amp stability is a good starting point. Ease of modding does vary from implementation to implementation. The Modulus and Parallel-86 are among the more customizable ones and offer excellent performance so no great sacrifice is necessary. At the lower powers favoured for HE speakers supporting lower voltage gains gets even easier.
Amplifier design process doesn't vary much as a function of the gain selected; Tim Green's series on op amp stability is a good starting point. Ease of modding does vary from implementation to implementation. The Modulus and Parallel-86 are among the more customizable ones and offer excellent performance so no great sacrifice is necessary. At the lower powers favoured for HE speakers supporting lower voltage gains gets even easier.
Then your earlier in-depth analysis, however perceptive and accurate as to Johnson noise, is actually wrong-headed as far as running the sorts of music system we're talking about.
However, I do see the wisdom of your remarks about amps. It seems to be correct, I suppose, as you inform us, that anybody who wishes to throw their present amp in the garbage, can design and build a better one. I welcome that news as I am sure others do as well.
Ben
However, I do see the wisdom of your remarks about amps. It seems to be correct, I suppose, as you inform us, that anybody who wishes to throw their present amp in the garbage, can design and build a better one. I welcome that news as I am sure others do as well.
Ben
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