TOPIC:

Hello,

I wonder what is the best way to control the volume of a 3 way stereo system with 4 PWR-ICE 250 when using a full digital link from audio source to the PWR-ICE ? Is there a way to use the digital control volume of the Music player (i am using PureMusic on iMac) without loss of sound definition and dynamic ?
I wonder if it's possible to daisy chain the 4 PWR-ICE with an AES/EBU link as shown in my plan ?


Best regards

@ fbraems

Nice setup! Based on the fact that each amp can indeed "select" between L or R channel of the AES_EBU feed, it's indeed possible to do this configuration. no problem at all.

For the volume control, do it at the source. It will be the easiest to keep all plate amp in sync. No worries since you're all in digital domain (no ADC- conversion).

DevTeam

I am planning to build an active 4 way speaker (very similar as the config above). I would like to use digital inputs (mainly optical/spdif) and I am looking for a remote master volume control solution. Does Minidsp have a solution for this?

@ Hanski

Unfortunately we don't have a master volume solution for master volume control... the nanoDIGI could do it with say an IR remote but it's a bit redundant ... (2 DSP). www.minidsp.com/products/minidsp-in-a-box/nanodigi-2x8-b

Devteam

devteam wrote:

@ fbraems

Nice setup! Based on the fact that each amp can indeed "select" between L or R channel of the AES_EBU feed, it's indeed possible to do this configuration. no problem at all.

For the volume control, do it at the source. It will be the easiest to keep all plate amp in sync. No worries since you're all in digital domain (no ADC- conversion).

DevTeam

Is that last statement really true?

I realize it looks that way since the IcePower has a digi input, however, looking at the data sheet for the 125/250ASX2's one can see that the module only has an analog Line Level input on P102 (3.3V, max).

Therefore, the signal chain is actually:

Digital Source -> DSP Digital In -> miniDSP DAC -> DSP Analog Out to Amp -> 250ASX2 Amp Module Analog In -> Amp A/D (PCM -> PWM) -> Amp Analog Power Out to speakers.

So, it's really:
Digital -> Analog -> Digital -> Analog

Which begs the question - Why don't miniDSP and IcePower get together to engineer a truly all digital signal chain?

It would seem like all you need to do is utilize an I2S I/F between the DSP section and the Digital Amp section.

PCM Digital In -> I2S/DSP/I2S -> PWM -> Power Out. All digital!

What am I missing?

Thanks,
Ivanovich

PWM is not digital - en.wikipedia.org/wiki/Class-D_amplifier#Terminology

Here's an interesting article (although not exactly objective) - www.audioholics.com/audio-amplifier/the-...l-class-d-amplifiers

Very informative. Thanks for clearing that up for me.

Seems maintaining the digital signal format up to the input of the DSP is as far as it should stay digital, as a good Class D amp is basically analog anyway.

On the objectivity - I can handle that kind of bias (favoring his design) from an engineer, when they can back it up. His bona fides look beyond ligit!

I

Ivanovich wrote:

devteam wrote:

For the volume control, do it at the source. It will be the easiest to keep all plate amp in sync. No worries since you're all in digital domain (no ADC- conversion).

DevTeam

Is that last statement really true?

@ Ivanovich

If you read our statement, we stated "you're all in digital domain (no ADC- conversion).". I.e. we didn't imply that it would be an "all digital end to end" as I guess you're looking for. The Icepower are indeed analog in. So with this setup, the AES-EBU allows one to bypass the A to D conversion that would be required otherwise to get into the DSP.

HTH

DevTeam