Adding a pre-out to receiver

[Dave Bullet]

Hello,

I'd like to add a pre-out to my 2 channel receiver. It is a Denon DRA-335R (40w/ch) (about 10 years old). I do not have a schematic.

I want to do this so I can run a low level output to a subwoofer (the plate amp in the sub does not have high level inputs). I cannot afford to replace the receiver with an H/T one.

Any advice appreciated.

Thanks,
Dave.

[Dave Bullet]

I forgot to add..... the next model up in the same series (DRA-435R) cam with a built in pre-out - so I'm hoping adding one to the 335R won't be too difficult.

Thanks,
Dave.

[sam9]

If you can find a schematic that would help. Or if discrete components are used it may be possible to backtrack from the speaker-outs to whwre the power amp input is. That's where you would wire in a takeoff to the preouts.

Could be super simple or it could be nearly impossible. Actually, the older the unit, I suspect the easier the mod. (Less integration.)

[Bill Fitzpatrick]

First thing I would try is to take the output right off of the volume control. Just tack solder some audio cable and try it out. If all is well you can make it more permanent.

[EchoWars]

Originally posted by Bill Fitzpatrick
First thing I would try is to take the output right off of the volume control. Just tack solder some audio cable and try it out. If all is well you can make it more permanent.

Most volume controls are pre-amplification stage...in other words, before any gain or buffering stage. Output would be pretty miserable (very low and no tone control).

If you really want pre-outs, you will have to get a schematic. I have added pre-outs to various integrated amps and a few recievers. Sometimes easy, sometimes a pain. Not a project for the squeamish or something to try on an expensive piece of equipment.

If all you need is a low-level input to the sub, you can get a pre-made voltage divider to do this for you. I believe many are designed for car audio, but should work fine and would avoid hacking the amp.

[Dave Bullet]

Thanks for the replies / advice.

I didn't think there was an easy way necessarily - just in case it was one of those 101 things - "look for this sort of circuit - then add that this to it" etc...

Thanks. I think you are right - I could risk the amplifier - all for a low level output to the sub. I'll go the voltage divider route so I can use the speaker level outputs.

Thanks,
Dave.

[halojoy]

Denon Service Manuals
This site sells Denon Service Manuals.
A service manual has schematics. But User manuals has not.

Maybe the Denon DRA-355A is very smilar to someone of those listed. models.
DRA-300 1
DRA-325R 1
DRA-350 1
DRA-350 1
DRA-355 1
DRA-400 1

halo - has had to examine and draw some schematics
all by himself - of old amplifiers he has got

[sangram]

I typically cut the track from the wiper of the volume control, add a small emitter-follower and route it back in (I do this all the time in mini-compos where owners want to add graphic equalisers) after the cut. The emitter-follower ensures sufficient buffering and little reduction in sound quality.

If you only want the out, just taking the same point into a nice little buffer will ensure little load on the source/volume control and a nicely buffered output...

[SkinnyBoy]

I dunno.. I think it would be easy... there would be seperate amp and pre amp boards.. yeah? probably with only a few wires connecting the two... just look for 2 shielded wires bridging the two boards.. Thats what all the older amps I have looke at are like... perhaps mine were even older... yeah, they were... VERY OLD.. lol.. ohh well..

[Tazzy]

Mmmm is it that easy? I've got a Denon PMA 1080r and I'm building 2 Hybrid ZenV4's... Turning the Denon in a temporary pre-amp would be very nice