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Could You Hack an AVR into a High-SINAD Preamp?

Open Mind Audio

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For the electronically inclined here (which I am not), I'm curious: Would it be possible to take a decent AVR and hack it in a way to create a multichannel preamp that would meet the high-SINAD expectations many of us have for critical audio listening? In other words, could you open up the box, make useful modifications to reduce noise, maybe disable the amps, retain a pure direct preamp section going to external amps, and also a digital pre-pro section that allows for EQ, with a goal of reaching outstanding SINAD?

I know this would void the warranty (duh). I know it may not be possible.

Just wondering, given there are few options for good AVRs/multi-channel pre-pros.

The goal is to have a single multichannel preamp that is good enough for critical audio listening in stereo and multichannel, and that also does double duty as a HT processor, for atmos, room EQ, etc. Since the market does not seem to be creating such a beast, could a good tech modify the right AVR to achieve this goal?
 

Doodski

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could you open up the box, make useful modifications to reduce noise
Not likely.
disable the amps
Yes, that should doable. It may be tricky with the protection and thermal protection circuitry but should be doable.
retain a pure direct preamp section going to external amps
Should be doable.
a digital pre-pro section that allows for EQ
Too much work and adding the software for this will be a dead end. So that's a no on this request.
 

MaxwellsEq

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No.

There are some projects that make you wonder if it would be fun to try or interesting. But this would be pointless and deeply unsatisfying.
 
OP
Open Mind Audio

Open Mind Audio

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Not likely.

Yes, that should doable. It may be tricky with the protection and thermal protection circuitry but should be doable.

Should be doable.

Too much work and adding the software for this will be a dead end. So that's a no on this request.
I didn’t phrase that part right. Just meant you would use whatever DSP type of situation was already in the AVR - not that you would add something to it.
 

Doodski

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I didn’t phrase that part right. Just meant you would use whatever DSP type of situation was already in the AVR - not that you would add something to it.
If the AVR has EQ/PEQ and other capabilities then those should carry forward into the working version of the MOD'd AVR.
 

Doodski

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I want to add that we have not even approached the topic of expense for doing this stuff. It would be very expensive because of the time consuming nature of the MODs and the nature of doing it to one single AVR.
 

NTK

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Weeb Labs has a thread on how to extract the digital outputs from AVR's. It isn't simple but theoretically you can use whatever high performance DACs you want to convert the digital output into analog or feed the digital output straight into powered monitors that accept digital inputs.
 

Chrispy

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Even dedicated pre-pros don't measure all that differently from some avrs....if they can't do it without amps what would be the advantage to taking the amps out of the picture on an avr?
 

Doodski

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Even dedicated pre-pros don't measure all that differently from some avrs....if they can't do it without amps what would be the advantage to taking the amps out of the picture on an avr?
The shared power supply in the AVR will benefit from getting the amp circuitry out of the picture and from guzzling all the power from the power supply. Theoretically it should be a improvement but in reality that remains to be seen in effect.
 

Chrispy

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The shared power supply in the AVR will benefit from getting the amp circuitry out of the picture and from guzzling all the power from the power supply. Theoretically it should be a improvement but in reality that remains to be seen in effect.
Theoretically....but practically? What would the audible benefit be of a higher SINAD, too? :)
 

Doodski

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Theoretically....but practically?
It depends on the specific AVR in question. Some have better voltage and current regulation in the power supplies than others that may have cheapO design because they scrimped on parts. The tighter the regulation the better in all examples that I can think of for a AVR.
What would the audible benefit be of a higher SINAD, too? :)
There should be less background noise, less hiss, less variation in the power regulation(s) that would cause the analogue and digital ICs to operate with less than optimal voltages. Additionally there will be less digital chatter (Noise induced onto the signals via the voltage supplies being changed via digital circuitry instantaneous current draw on the voltage regulators.) in the background of the audio. Using small value inductors at the power regulators or at the power input to digital ICs will reduce that issue too.
 

Chrispy

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It depends on the specific AVR in question. Some have better voltage and current regulation in the power supplies than others that may have cheapO design because they scrimped on parts. The tighter the regulation the better in all examples that I can think of for a AVR.

There should be less background noise, less hiss, less variation in the power regulation(s) that would cause the analogue and digital ICs to operate with less than optimal voltages. Additionally there will be less digital chatter (Noise induced onto the signals via the voltage supplies being changed via digital circuitry instantaneous current draw on the voltage regulators.) in the background of the audio. Using small value inductors at the power regulators or at the power input to digital ICs will reduce that issue too.
I've yet to hear any hiss/background noise from any of my avrs....altho at higher levels perhaps but is it particularly audible? Any testing done on such? Or just theoretical?
 

Doodski

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I've yet to hear any hiss/background noise from any of my avrs....altho at higher levels perhaps but is it particularly audible? Any testing done on such? Or just theoretical?
I don't know the reality (Versus theoretically.) of the new AVRs because I have not owned one, retailed product or serviced product for a fairly long while in what is electronics life times. The new transistors have improved, the ICs have improved and the circuitry designs have been honed to a sharp edge colloquially speaking and developed for decades now so the SN has improved and so it should not be rocket science designing and making the AVR for a major player like Denon. The extent of testing in recent years has been a simple turn up the volume and see how noisy it is. I don't have lab/test gear anymore.
 
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