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Topic: S/PDIF to Analog Box with Volume Control (Read 5323 times) previous topic - next topic
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S/PDIF to Analog Box with Volume Control

I have a pair of powered speakers (Behringer B2030A, XLR input) but they are a pain in the ass to use because
1) they don't have digital input
2) they don't have volume control

I currently have a stereo pot wired between the XLR-RCA adapters, but it's pretty bad because it's linear, at low volumes the left/right volumes become unequal, and turning the knob introduces "scratchy" glitches in the sound. Also, the analog outputs of my computers are pretty bad (e.g. scrolling a web page induces a buzzing sound!?).

The best solution would be an external box that has an s/pdif input (preferably optical), stereo analog outputs (preferably XLR), and a logarithmic volume control knob. Can anyone suggest a such product that costs less than 100€? For more than that I could just buy a new pair of speakers with digital input, volume control and headphone output (such as Behringer MS20). The only ones I've been able to find are obscenely expensive. I don't want an USB sound card because I'd like a "computer-independent" solution.

In the case that such a product is a pipe dream, build-it-yourself solutions are welcome. I've been looking at schematics based on CS8416 + someDAC. Any DAC chips with volume control that don't require a microcontroller to use? Or would I need a separate "digi-pot" for volume control?

S/PDIF to Analog Box with Volume Control

Reply #1 –
Quote
The best solution would be an external box that has an s/pdif input (preferably optical), stereo analog outputs (preferably XLR), and a logarithmic volume control knob.
An external DAC, and possibly a monitor controller (for volume control) would be well beyond your budget.  (These are typically studio or audiophile items.)

An external USB soundcard would be the most economical solution.  Having it external to your computer should make it immune to interference & noise from your computer.  (You won't get balanced XLR outputs.)

You could use a home theatre receiver, but typically the "tape" outputs won't be affected by the receiver's volume control.  You should be able to find one near 100€.  Amazon offers one for $100 USD, and several below $150 USD.



Quote
I currently have a stereo pot wired between the XLR-RCA adapters, but it's pretty bad because it's linear, at low volumes the left/right volumes become unequal, and turning the knob introduces "scratchy" glitches in the sound.
  I've had similar problems, and I've thought about using an LM1036, which is an analog-voltage-controlled volume/tone circuit.  It's cheap, much simpler to wire-up than a digital circuit, you can use a standard "mono" pot, and a capacitor to filter-out any "scratchy-pot" noise.

S/PDIF to Analog Box with Volume Control

Reply #2 –
Why not get a new pot from an electronics store. Spend the other €99 on music (CDs/downloads/going out for live music).

S/PDIF to Analog Box with Volume Control

Reply #3 –
Quote
I've had similar problems, and I've thought about using an LM1036, which is an analog-voltage-controlled volume/tone circuit. It's cheap, much simpler to wire-up than a digital circuit, you can use a standard "mono" pot, and a capacitor to filter-out any "scratchy-pot" noise.

Sounds like a plan. If I manage to build something I'll post about it. Maybe afterwards I'll add that S-PDIF DAC part too. Thanks for the replies.

S/PDIF to Analog Box with Volume Control

Reply #4 –
Beresford 7510

£109 + VAT/Sales Tax

http://www.beresford.me/main/main.html

4 x S/PDIF in (two electrical two optical)

Fixed analogue out

VOLUME CONTROL

Variable Analogue out

A more expensive model 7520 is about to be launched with USB input and better analogue circuits that will drive high quality headphones.

The cheaper one will do all you ask, and do it superbly.
Brian
 

S/PDIF to Analog Box with Volume Control

Reply #5 –
Thank you so much for that suggestion! It's almost perfect - even a headphone output. Too bad the outputs aren't balanced (although I guess they could be easily retrofitted using a pair of resistors and XLR sockets). I'm a little concerned about ground loops, how the DAC works with the "pro-level" inputs of my speakers, and how the volume control behaves (I mostly need the quiet end which is why a logarithmic volume control is important). If anyone has comments about the mentioned issues I'd love to hear them.