Adding Preamp Outputs to an Integrated Amp with No Outputs??

Lovegasoline

I've been running a mid-1980's vintage Yamaha Integrated Amp, model A-700.
My sources are a Meridian 508.20 CDP and a Music Hall MMF.7 Turntable (with Eroica Cartridge). Speakers are LSi9s.

After a long upgrade waiting period, I just purchased a McCormack DNA-125 Amp and I want to put it into my system. Until I can afford a preamp upgrade, which may be a long wait (I've had my eye on an Audible Illusions M3A), I intended to use the preamp and phono-pre section of the Yamaha Integrated amp. That is to say I wanted to BYPASS the amplifier section of the A-700 and just use the Preamp and Phono Pre sections of the Yamaha.

Unfortunately, I now see now that there is no way to connect the McCormack to the Yamaha. See this thread for details:

http://www.polkaudio.com/forums/showthread.php?t=74536


Is it feasible to hack the Yamaha and convert it to include a preamp outputs (including the phono stage as I use a TT)?
Just how involved would it be to convert the electronics on the Yamaha to include an output jack? 3 years back I had asked a member of another forum for a schematic of the A-700 but he never forwarded it: I'm sure I could locate one if I searched harder. The Yamaha only cost me around $85 so it is essentially free audio. But still, it is the only functional amp/preamp I have now, so I do not want to totally butcher it. I have some basic electronics skills, a basic home electronics workshop, but I am no expert. In other words, I could do all the soldering/assembling/mechanical work, but I wouldn't be able to design the circuit. What would a modification like this involve?


Here's what the back of the Yamaha A-700 has by way of single ended jacks:

---

PHONO: L/R

---

INPUTS:
-TUNER, L/R
-DAD, L/R
-AUX, L/R

---

TAPE 1
-TAPE PB, L/R
-REC OUT, L/R

---

TAPE 2
-TAPE PB, L/R
-REC OUT, L/R

---

Thanks a bunch for any ideas.

hoosier21

you could buy on of these
http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=302-307

or use that 65.00, towards a preamp that you need

zingo

It seems like you could tap into the inputs and just run their signal out with a separate set of wires and jacks. Its seems pretty straight forward, but I'm sure someone will shoot a hole in my simple plan.

Lovegasoline

hoosier21,
Thanks for the link. I wonder how well that would work, reviews seem mixed. I probably would rather put the $65 towards a preamp.

zingo,
I am thinking along these lines.

Anyone care to elaborate how to do this with some opinions about how involved it would likely be?

zingo

If actually the idea works; open the top on the amp and find the incoming signal wires. Strip off a bit of the insulation on the wires and solder onto it with the new wires. Connect those pairs to your new outputs and you should have a signal. Note that these outputs will be always on, and a switch could be installed if you wanted the ability to toggle them off.

ben62670

zingo wrote: »

If actually the idea works; open the top on the amp and find the incoming signal wires. Strip off a bit of the insulation on the wires and solder onto it with the new wires. Connect those pairs to your new outputs and you should have a signal. Note that these outputs will be always on, and a switch could be installed if you wanted the ability to toggle them off.

Not a good idea.
You can easily build a passive volume control to use with the tape monitor outs. A linear taper 50k pot, and 4 RCA jacks, and you are good to go. The bad news is you have to turn the volume manually. No remote.
Ben

zingo

zingo wrote: »

but i'm sure someone will shoot a hole in my simple plan.