Suggestions on a preamplifier project with a "A/V processor loop" option

Spyhunter · 6th November 2001, 09:23 PM

Hi!

Does anyone have suggestions for good-sounding DIY preamplifiers which have an option to route the signal from main channels through an external multichannel processor ("processor loop") and then back to the preamplifier? How about a 5.1 preamplifier with no surround sound processing?

All suggestions are welcome.

It wold be nice if the program source selection was implemented with some digital logic circuitry (microcontroller). One could even have nice-looking buttons and leds on the front panel (don't get me wrong, I don't want my possibly high-end grade pre-amp look like a lo-fi christmas tree mini-stereo) - although these leds and buttons don't necessary require digital circuitry inside.

Some other nice features would be digital inputs (requires an internal DAC, of course) and a power supply that works with a 220 V/50 Hz mains voltage.

Dave · 6th November 2001, 09:54 PM

I'd suggest building a good two channel pre-amp with a unity gain input or setting for the AV input.

Spyhunter · 7th November 2001, 10:04 AM

Can you point to any projects that are possibly available online?

What do you mean by unity gain input? Are you saying that the preamp output for the main channels should be the sum of the selected normal two-channel input and possible front channel input from 5.1 (or whatever) input connectors - without any selection switch needed?

Nisbeth · 7th November 2001, 09:28 PM

Spyhunter:

I actually thought about this very idea some time ago, because I fell for Harman/Kardon's Signature 1.0 preamp, which sadly is a little out of my pricerange (check it out, it's cool!!). The project mainly stranded because I'd need a 6 way (or 8-way) volumecontrol for the processo-loop to function as intended and that was hard to come by. If you're interested in seeing what i did find out, let me know and I'll look for it this weekend when I have more time and then mail it to you or post it here.

regards
/Uffe

Dave · 8th November 2001, 01:49 AM

A unity gain input simply means the pre-amp does not add gain to the signal connected to that input, it also by passes the pre-amps volume control. It would be connected to your surround processor.

Spyhunter · 8th November 2001, 09:25 AM

Oh yes, of course. The amplification is equal to one, hence unity gain. I wasn't aware of the english term, thank you for the clarification.

Spyhunter · 8th November 2001, 09:31 AM

So, I guess it would be easiest and most convenient to just build an ordinary two-channel preamp, and add a separate unity-gain input for an external surround decoder. Then either the "normal" preamp stereo inputs or the front channel input from the multichannel inputs can be directed to the pre-out main front channel outputs.

The volume setting would be done from the preamplifier when listening to two channel material, and from the external decoder when listening to multichannel amplifier.

Does this make sense?

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6th November 2001, 09:23 PM	#1
Spyhunter diyAudio Member Join Date: Nov 2001 Location: Finland	Hi! Does anyone have suggestions for good-sounding DIY preamplifiers which have an option to route the signal from main channels through an external multichannel processor ("processor loop") and then back to the preamplifier? How about a 5.1 preamplifier with no surround sound processing? All suggestions are welcome. It wold be nice if the program source selection was implemented with some digital logic circuitry (microcontroller). One could even have nice-looking buttons and leds on the front panel (don't get me wrong, I don't want my possibly high-end grade pre-amp look like a lo-fi christmas tree mini-stereo) - although these leds and buttons don't necessary require digital circuitry inside. Some other nice features would be digital inputs (requires an internal DAC, of course) and a power supply that works with a 220 V/50 Hz mains voltage.

6th November 2001, 09:54 PM	#2
Dave diyAudio Member Join Date: Oct 2001 Location: New Zealand	I'd suggest building a good two channel pre-amp with a unity gain input or setting for the AV input.

7th November 2001, 10:04 AM	#3
Spyhunter diyAudio Member Join Date: Nov 2001 Location: Finland	Can you point to any projects that are possibly available online? What do you mean by unity gain input? Are you saying that the preamp output for the main channels should be the sum of the selected normal two-channel input and possible front channel input from 5.1 (or whatever) input connectors - without any selection switch needed?

7th November 2001, 09:28 PM	#4
Nisbeth diyAudio Member Join Date: Jan 2001 Location: Denmark	Spyhunter: I actually thought about this very idea some time ago, because I fell for Harman/Kardon's Signature 1.0 preamp, which sadly is a little out of my pricerange (check it out, it's cool!!). The project mainly stranded because I'd need a 6 way (or 8-way) volumecontrol for the processo-loop to function as intended and that was hard to come by. If you're interested in seeing what i did find out, let me know and I'll look for it this weekend when I have more time and then mail it to you or post it here. regards /Uffe

8th November 2001, 01:49 AM	#5
Dave diyAudio Member Join Date: Oct 2001 Location: New Zealand	A unity gain input simply means the pre-amp does not add gain to the signal connected to that input, it also by passes the pre-amps volume control. It would be connected to your surround processor.

8th November 2001, 09:25 AM	#6
Spyhunter diyAudio Member Join Date: Nov 2001 Location: Finland	Oh yes, of course. The amplification is equal to one, hence unity gain. I wasn't aware of the english term, thank you for the clarification.

8th November 2001, 09:31 AM	#7
Spyhunter diyAudio Member Join Date: Nov 2001 Location: Finland	So, I guess it would be easiest and most convenient to just build an ordinary two-channel preamp, and add a separate unity-gain input for an external surround decoder. Then either the "normal" preamp stereo inputs or the front channel input from the multichannel inputs can be directed to the pre-out main front channel outputs. The volume setting would be done from the preamplifier when listening to two channel material, and from the external decoder when listening to multichannel amplifier. Does this make sense?

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