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Thoughts on DSP multiamp/attenuator setup?
Thoughts on DSP multiamp/attenuator setup?
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Old 9th January 2018, 05:31 PM   #11
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by Pano View Post
Digital volume control is super clean.
Particularly if it is done by adjusting the DAC voltage reference, a pity it isn't standard practice. Otherwise it will depend on available bit depth
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Old 9th January 2018, 06:34 PM   #12
Juhazi is offline Juhazi  Finland
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Sorry, but I don't understand the fear of loosing S/N or dynamics or sound quality with level adjustment, with dsp systems. First, you must have at least 24-bit or processor, rest is easy.

I have almost four years experience with minidsp 4x10HD and one year with 2x4HD. Both get analog signal from preamp, and in most challenging setup I have 3 DA/AD conversions and digital/analog level adjustments chained. Never heard any hiss or lowered dynamics! I suppose that to get in trouble, you must try really hard to do many things wrong!

Gain should be such that when source is giving maximal voltage, dsp/xo almost gets overloaded and power amp starts to distort. I don't have quite this but close. Hiss or hum can be heard at full spl setting without signal, but it is induced in analog interconnects. Spl with signal at 2 meters is then something like 110dB from a single loudspeaker, and still if I turn it down to 30-40dB sound is still very clean.

I have also tested minidsp 4x10HD with digital input from a CD-player, but it sounded just the same. My sources are laptop, CD, FM-radio, TV and BD. The "preamp" is 2002 model Yamaha RX-V830RDS and all signals go through it's DA and digital volume control, analog to minidsp. It works also as power amp for center and rear channels of 5.0 listening. Works like a train's toilet! And was voted to give best sound in a national diy event!
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Last edited by Juhazi; 9th January 2018 at 06:36 PM.
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Old 9th January 2018, 06:58 PM   #13
scottjoplin is offline scottjoplin  Wales
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It depends. In my case, CD S/PDIF > DCX2496 > POT > AMP is the better option
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Old 9th January 2018, 09:21 PM   #14
Pano is offline Pano  United States
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Thoughts on DSP multiamp/attenuator setup?
Quote:
Originally Posted by scottjoplin View Post
Otherwise it will depend on available bit depth
Well yes, as said above. And 24 bits is plenty. Even the real world S/N performance of most DAC circuits equivalent to 20 bits is plenty.
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Old 9th January 2018, 09:59 PM   #15
mark100 is offline mark100  United States
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Quote:
Originally Posted by Pano View Post
Well yes, as said above. And 24 bits is plenty. Even the real world S/N performance of most DAC circuits equivalent to20 bits is plenty.
Yeah, DACs don't seem to be a problem with gain staging anymore.

I get hiss with multiple AD/DA conversions in the signal chain...so I'm led to speculate that AD conversions aren't in the same league as DACs yet..but that's pure speculation......

I just try to keep everything digital till the last DA conversion.
Right now my "A signal" rig is jriver, to a x-32, to a midas DL-155 I/O box, to 4x opendrc's, back to the DL-155..all digital.
Then the DL-155 performs 8 channel DAC duty.
And I keep amp gain as low as works...

This gives me about a 30dB working range..with low hiss and room to crank...on a system about 103dB 1 watt..

Last edited by mark100; 9th January 2018 at 10:03 PM.
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Old 9th January 2018, 10:17 PM   #16
Pano is offline Pano  United States
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Thoughts on DSP multiamp/attenuator setup?
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Originally Posted by mark100 View Post
And I keep amp gain as low as works...
Yep.
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Old 9th January 2018, 10:18 PM   #17
seanp2k is offline seanp2k  United States
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I agree that digital volume control is the way to go, avoiding additional A->D / D->A conversions as much as is practical for your routing. https://www.rme-audio.de/download/adi2pro_e.pdf Page 89 has a good technical explanation of how to do digital volume control “right” without losing fidelity.
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Old 9th January 2018, 10:20 PM   #18
scottjoplin is offline scottjoplin  Wales
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Mark, what you really mean is that you attenuate last of all so all the nasties are lessened. Someone recently was thinking of taking that a stage further and attenuating after the amplifier!
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Old 9th January 2018, 10:26 PM   #19
Pano is offline Pano  United States
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Thoughts on DSP multiamp/attenuator setup?
What nasties? Read the page in the PDF linked above. Spot the Spinal Tap reference.
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Old 9th January 2018, 10:29 PM   #20
scottjoplin is offline scottjoplin  Wales
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I'm talking about the analogue attenuation before the amp not casting aspersions on your digital prowess
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