What abuot the digital Volume Control

[machinow]

Hi, All. I know you do not prefer digital Volume control in the DACs /mostly sigma-deltas/, but it is technological and has high characteristics. Have anyone tried it ??
And HAVE ANYONE TRIED to change the Iref current of a sigma-delta with current-output to achieve volume contol?? Just what is in the SONY TA-E9000ES???
I do appreciate any help here!

Bye

[A 8]

Digital volume control decrease wordlegth and increase distorsion....

[maczrool]

Originally posted by A 8
Digital volume control decrease wordlegth and increase distorsion....

Yes, but with less distortion than the analog equivalent, does it not?

Stu

[stokessd]

Originally posted by maczrool



Yes, but with less distortion than the analog equivalent, does it not?

I'd be shocked if it was lower distortion, particularly at low volume levels. You are rapidly losing bits.

Sheldon

[till]

OK, if you decrease volume in the digital section words are getting shorter and so information / quality is lost. But what´s about volume controll ind the I/V stage or by setting the reference ? If you divide 5V by 16 bit word or 3 V is no difference in information, but in volume level .

[stokessd]

Originally posted by till
OK, if you decrease volume in the digital section words are getting shorter and so information / quality is lost. But what´s about volume controll ind the I/V stage or by setting the reference ? If you divide 5V by 16 bit word or 3 V is no difference in information, but in volume level .

I don't see how that would be an advantage over a standard volume control in terms of signal degredation.

sheldon

[till]

We can´t know the advantage or disadvantage until tried out. DIY.

Is a standart pot is used we have the signal (AC) through resistor and so all the noise of the pot in the signal. To put a cap across the pot isn´t possible. If we controll ref. we have DC through the device that controlls and are enabled to smoth noise with a cap. ? Just an idea.

[machinow]

Here Is my opinion:
1. The true digital control:
If we have some 115dB of dynamic range of the DAC, and the 24 bits means 24*6+1.7dB=145.7dB DR we have about 30dB to waste. This is just speaking technical. In practice, Levels under -10...-20 dB of the full power /this means with 100W amp some 1..10W peak, you know this / ARE NOT adequate for "quality listening" In my construction I would simply do a -10..-20 dB relay switch after the DAC /i.e. after the I/V conv. and LPF/. This "combined control" will give good rezults at least in the -30...0dB settings for the volume, which is more than enough.

2. The analog-digital control:
I do not know how SONY does this exactly, but I expect some combination between Digital control+Control of the Iref + output gain control. This is well sounding unit, at least people say so, so it is worth trying. I would only miss the BJT switches
HAVE ANYONE TRIED THIS???

Hey, this thread is because I'm actually sick of using the noisy 100kohms pots /motorised/ and the chain of opamps and cables. With some electromagnetic field around this becomes quite noisier than the DAC /in my case, AD1852/OPA2134 chipset/
I just have to do some uController programming.
10-x

[till]

what about http://www.diyaudio.com/forums/showt...521#post124521

I have the PGA´s and Pic MCs, but not
skilled enough for for the assembler coding right now.

[machinow]

Till,
Generally I prefer AVRs, I know them better, yet not enough to program! I saw you want some other projects to do? Volume control etc. This is a nice thing, but it's expensive /that array of relays/ and enormous!! Therefore I prefer DAC controlling. And for analogue sources an ADC front-end
I also want to build some digital pre-amp of mine, but this micro stops me. I'm a kind of analog and mixed-signal Audio Engeneer, not a programmer Do you have any projects in your head??
In Bulgaria many parts are difficult to get, BTW
Bye