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Old 09-21-2020, 09:45 PM   #1
NewbieB
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Default Convert AV Receiver to Pre-amp

Hello, I would like to convert my powered Denon AVR-E300 to a pre-amp (line level source) by eliminating the power amplifiers.

Reason: I use active speakers that are already amplified. I don't want to run an amplified signal into my active speakers.



I know. But the cost of buying an AVR with pre-outs is wildly expensive and I wouldn't use any of the features other than 5.1Ch decoding.

My audio/video signal source is an Amazon Fire Cube with HDMI out. I need to get that digital signal out to my speakers. With passive speakers it's a piece of cake. Active speakers, not so much. Trying to find an audio signal path from the Amazon Cube to 5.1 active speakers has been rough. I wish I could buy just a unit to extract the audio from the Amazon cube and then convert it to separate line level analogue sources via RCA, 3.5mm, or even screw terminals. Actually, I think screw terminals would be my first choice.

I opened up the AVR and saw a connection from the signal processing portion to the amplification portion. Can I take those pins and use them as pre-amp sources? Just bypass the connection to the amplification board.
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Old 09-22-2020, 02:42 AM   #2
petehall347
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Default Re: Convert AV Receiver to Pre-amp

looks like you could do that but will need to look where the coupling capacitors are .if on main amp board then you need to add them .if before main amp you are fine .
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Old 09-22-2020, 10:55 AM   #3
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Default Re: Convert AV Receiver to Pre-amp

Do these images show where the capacitor is located on the boards, or should I look for a wiring diagram?
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Old 09-22-2020, 11:38 AM   #4
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Default Re: Convert AV Receiver to Pre-amp

Quote:
Originally Posted by NewbieB View Post
Hello, I would like to convert my powered Denon AVR-E300 to a pre-amp (line level source) by eliminating the power amplifiers.

Reason: I use active speakers that are already amplified. I don't want to run an amplified signal into my active speakers.

...

I opened up the AVR and saw a connection from the signal processing portion to the amplification portion. Can I take those pins and use them as pre-amp sources? Just bypass the connection to the amplification board.
Why don't you just put a pad on the output (or, better yet, on the INPUT to the active speakers!)? That leaves the receiver intact...
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Old 09-22-2020, 12:15 PM   #5
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Default Re: Convert AV Receiver to Pre-amp

i need to see the schematic .
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Old 09-22-2020, 12:29 PM   #6
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Default Re: Convert AV Receiver to Pre-amp

Here's the audio part schematic. Not sure if this is what's needed so I'll look for other schematics that look relevant.
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Old 09-22-2020, 12:31 PM   #7
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Default Re: Convert AV Receiver to Pre-amp

Here's the DAC schematic.
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Old 09-22-2020, 12:34 PM   #8
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Default Re: Convert AV Receiver to Pre-amp

Here's the Main Board (amplifier) schematic.
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Old 09-22-2020, 12:35 PM   #9
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Default Re: Convert AV Receiver to Pre-amp

There are other schematics for the SMPS, HDMI, MCU, etc but I don't know if those are relevant or helpful.
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Old 09-22-2020, 12:39 PM   #10
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Default Re: Convert AV Receiver to Pre-amp

Oh, and I discovered information that might be helpful. The service manual for the Denon AVR-E300 is the same as the X1000 and X1010. The X1000 and X1010 expose pre-outs on the back. That makes me wonder if the white sockets on the amplifier (main) board are pre-outs but aren't connected on my lower priced E300 model. Maybe I could just use the plugs.
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Old 09-22-2020, 01:23 PM   #11
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Default Re: Convert AV Receiver to Pre-amp

coupling caps are there on main amp board on all 5 channels .
you could use pre outs if you wish ..you would be better doing this .

Last edited by petehall347; 09-22-2020 at 01:25 PM..
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Old 09-22-2020, 01:36 PM   #12
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Default Re: Convert AV Receiver to Pre-amp

Great. Thanks for the help. I'd prefer to use the white pre-outs sockets on the main amplifier board. I didn't know that's what they were when I first started looking at the boards.
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Old 09-22-2020, 01:45 PM   #13
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Default Re: Convert AV Receiver to Pre-amp

i meant the ones on the rear panel .i dont see any on amp board
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Old 09-22-2020, 01:49 PM   #14
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Default Re: Convert AV Receiver to Pre-amp

those white connectors are for test points when adjusting the main amp channels .DO NOT connect anything to those .
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Old 09-22-2020, 02:18 PM   #15
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Default Re: Convert AV Receiver to Pre-amp

There aren't any pre-outs on the rear panel of the Denon AVR-E300. The Denon AVR-X1000 that uses the same amplifier board is the model with the pre-outs on the back.
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Old 09-22-2020, 03:18 PM   #16
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Default Re: Convert AV Receiver to Pre-amp

Ok, now I need to figure out how to add coupling capacitors to the 12 pin connector from the digital board.

It looks like the capacitors are 100v/10uf and 63v/100uf. Also, 50V/220uf and 100V/10uf.

I have no idea which ones I'd use to create pre-outs. Have to keep digging to see what I can find.
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Old 09-22-2020, 03:21 PM   #17
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Default Re: Convert AV Receiver to Pre-amp

i see . so the pic is wrong then ?
thinking about coupling capacitors some more you wont need them if the amp you are plugging into already has them .. most do so i guess you could pull the plug off amp board then use front left front right wires and agnd .
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Old 09-22-2020, 05:10 PM   #18
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Default Re: Convert AV Receiver to Pre-amp

Yes, the active speakers contain amplifiers. Those amplifiers have capacitors. Specifically, 35V 330uf capacitors.

If I can use the socket on the digital board to extract a line level signal -- totally bypassing the amplifier board -- then send that directly to my active speakers then we're back to having an easy solution again.
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Old 09-22-2020, 06:09 PM   #19
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Default Re: Convert AV Receiver to Pre-amp

coupling capacitors are small ones . 2.2uf approx are used mostly ..
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Old 09-22-2020, 06:29 PM   #20
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Default Re: Convert AV Receiver to Pre-amp

In that case it looks like it might be these four 50V 2.2uf capacitors on the amplifier.
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