Adding pre out/main in to an old amplituner.

[yossarian]

Hi

I am looking into adding room correction and hopefully sub integration to my existing system. In the present, I am running DENON DRA1000 amplifier, with an active sub wired to the speaker terminals using the high input. I would like to try out running MiniDSP 2x4HD. Since the amp does not have pre out / main in, it seems that putting MiniDSP into the tape loop is the way to go. But since the tape loop is before the volume control, this would require leaving the sub on the high input and using the sub's lowpass filter for the sub integration. And running mains full range. So room correction is doable, but not sub integration.

I know that the proper answer here is "get some better amplifier instead of this thing you have". But, just for shits and giggles, is it possible to cut into a signal path in the device I have to add pre out / main in to it?

I have the service manual with schematics (https://drive.google.com/file/d/1DbEIkySLfM2NZoH4G4x-wxwpkkIAwrjV/view?usp=sharing), and medium soldering skills.

 

[JeffS7444]

Basically you'd want to create a set of Pre-Out / Main-in jacks by tapping in right at the input of the power amplifier. That way, muting, tone controls, balance, etc would all continue to work. But if it were my receiver, I don't think I'd do this. Instead, if that subwoofer has speaker-level inputs and satellite speaker outputs, I'd simply use those, and use MiniDSP solely for the purpose of room correction. Although MiniDSP HD2x4 has 4 output jacks, you can simply configure it to pass full-bandwidth signal: You aren't required to use it as an active crossover.

 

[DVDdoug]

You can probably unsolder the "output" connections to the volume control pot and make your "inserts" there.

 

[NTK]

Looks like the connector CN8A between the display board and the main board is where you may want to breakout the signals. Pins 1-4 of the connector receive the signals from the main board, and pins 5-8 return the signals to the main board after the volume/balance adjustments.

You should be able to insert the miniDSP between connector CN8A pins 5-8 of the display board and connector CB8A pins 5-8 of the main board. You will retain proper volume controls of your Denon.

From my quick read of the schematic, pin 5 should be R+, pins 6 & 7 should be signal ground, and pin 8 should be L+.

 

[DanielT]

A friend of mine and I fixed a sub out on a vintage amplifier this weekend.Signal from the pre amp section of the amplifier. With others word a pre out.

Maybe not the nicest job but it works. We thought about putting it on the blank thread. But uh.. we made it easy for us.

It works anyway. Maybe a bit long thread to the grunding point..

Project sub output

An old amplifier Luxor 7082 A. I connected a high to low level converter on the speaker outputs, to be able to connect an active subwoofer. Connected in parallel, together with the cables to the speakers. The converter: My friend said: why not take the signal directly from the pre amp section...

audiosciencereview.com

 

[yossarian]

Signal from the pre amp section of the amplifier. With others word a pre out.

I am somewhat ashamed to admit that I can not figure out where exactly does the preamp section end in my case. Is the "taking signal out of the volume pot" a good approach, or should it be somewhere further down the signal path...

 

[DanielT]

I am somewhat ashamed to admit that I can not figure out where exactly does the preamp section end in my case. Is the "taking signal out of the volume pot" a good approach, or should it be somewhere further down the signal path...

You should not be ashamed.

In my case, I got help from my friend. I do not know much about electronics. Ask here and you will probably get help.
NTK in this thread has a solution.

Tips if you feel insecure. If the one you are going to fix it on is worth a little $. Buy the cheapest amplifier you can find at a flea market. Check that there is a schedule for it online. Then you practice on that amplifier so you get a little feeling for it all.

I added a little to my thread Project sub output how my friend explained it to me. How you can then do with your remains to be seen. Fun project anyway!