Looking forward to having a 'Class A' party with my new A-1000 integrated Yamaha and my M-45 Power Amp.

Too bad the A-1000 does not have a preamp out. But we can remedy that without drilling holes or doing anything that is not 100% reversible.

Here are the two amps, waiting to be mated.
Also, a picture of the two disparate pairs of speakers I want to run simultaneously. Those Yamaha speakers are so-so HT style, but with the added definition provided by those 4ohm Alesis close field monitors, I can no longer listen to each speaker individually. Maybe someday I'll get something better, but these two really complement each other.

Since I WANT to use the amp section of the A-1000, the hookup I'm going to show is a parallel hookup, where the preamp output is split between the A-1000's power section and the external jack.

One could easily make formal 'Pre-out' and 'Power Amp In' by totally hijacking both Tape 2 jacks.

On my A-1000 (different from the schematic) the wires to the power amp come from the volume pot PC board. This is very easily accessed by removing the volume knob and taking the nut off the volume pot shaft. Then the assembly lifts out. I carefully soldered my new leads to the bottom of the PC board, leaving the existing leads intact. This forms the 'Y' circuit, splitting the preamp signal.

Instead of taking a drill to the back panel, I decided to hijack the 'TAPE 2 OUTPUT" jack and use it for my new "PRE-OUT" jack.

In this case the existing leads to the "TAPE 2 OUTPUT" jack need to be removed. The three leads are on what looks like a mini-Molex type connector, but it is soldered in place. After removing the little 3-prong connector, I re-used the holes in the PC board for my leads.

The end of connector that I removed was covered with some heat-shrink tubing and cable-tied out of the way. It can easily be soldered back in place if reversal of the mod. is needed.

I wanted some non-permanent indicator on the back of the amp, to remind me I did the mod. Knowing in 2 years I'm going to be scratching my head wondering why my Tape 2 out is not working correctly.

I used a common label maker with black tape to make new lettering for the Tape 2 output jack. This is just a stick-on label that can be easily removed.

Here is the final wiring from the inside.

The mod. was pretty simple to perform. It took much longer to figure out how to do it with out messing things up than it did to do the actual work.

How does it work? It works great!

When I first plugged it in I was kicking myself for connecting the ground on both ends of my jumper wire because I thought I had a ground loop hum. Then I realized that my TT had been grounded to a different preamp. So, grounding the TT to the A-1000 fixed that. Since I DID connect the ground on both ends of my jumper, I just need to ensure the external amp only gets its ground through the RCA interconnect cable, and the TT is grounded to only one amp.

In terms of setting the volume between the two sets of speakers. It is easier to do if you have two integrated amps. With one power amp, the split signal will be unequal if the input impedance of the A-1000's internal amp and the external power amp are different. In my case they seem about the same. This is not a problem unique to this mod. This is the case anytime you split a Pre-out signal to two power amps.

The M-45 does have trimmers for each channel so, if I want one set of speakers to be quieter, I need to connect them to the M-45 and turn down the trimmers as needed. On initial listening, the two power amps seem nicely balanced with the M-45 trimmers maxed on 10.

Good job. Informative.

I've got a non working 1000 that I'm trying to repair.
I wonder if the next time you are in there taking pics if you could snap a shot of how each driver pair is mounted?
It would be helpful to me.

Don't go out of your way to do it though!

Thanks

Good job. Informative.

I've got a non working 1000 that I'm trying to repair.
I wonder if the next time you are in there taking pics if you could snap a shot of how each driver pair is mounted?
It would be helpful to me.

Don't go out of your way to do it though!

Thanks

Can you tell from this picture (its a blow up of one of the others). Glad to help if I can. I was actually looking for a project amp, so I had to turn this amp into one :)

Thanks for the effort. I think I saw that pic on another of your posts.
I think I can make out one transistor just to the right of the 3 outputs.
I believe it's green in color mounted to the heat sink.
One driver is black case, one is green. Don't remember the numbers offhand.

Thanks for the effort. I think I saw that pic on another of your posts.
I think I can make out one transistor just to the right of the 3 outputs.
I believe it's green in color mounted to the heat sink.
One driver is black case, one is green. Don't remember the numbers offhand.

Ok now I see, its around the corner. I'll see if I have any other pictures that show it better.

This guy?

This guy?

Appreciate it.
That's the puppy. I think the green to-220 is also mounted on the innermost position on the heat sink on the other side.
Do you remember?

After living with this for a while and looking at the pictures and schematic I think I might be able to make it even better.

The 'extra' dual volume pot on the board in the picture is NOT in the schematic. The volume to the preamp is already controlled by the first dual pot on this board. Why the extra control? I am not sure, but I was thinking if I bypassed this extra pot with my PRE-OUT wire, I would have a hotter signal to my external amp. This would let me control the balance of the two amps with the input trimmers on the external amp. Right now the input trimmers on the external amp are all the way up and it could be maybe a little louder.

So, to test this I would just swap my 3 little wires over to the circled location (thats the input feed to that last dual volume pot on the board)

(I'll get some more pictures while I am in there)

I am starting to understand this amp more. Now I think I see that by placing two sets of volume pots in series they are fine-tuning the 'taper' of the control. So, if I were to draw my PRE-OUT signal from before that last dual pot the internal amp and the external amp will have different 'tapers' to the function of the volume knob. Not what I want.

It seems to be a pretty sophisticated amp.
A little beyond my learning so far. Mine hasn't ever worked in my possession. Lied to by the seller.
I've got lots of time so sooner or later I'll figure it out.
Thanks for the photos.

You should start a thread with pictures and tell what you have found so far. My favorite threads are those dealing with non-working amps that get analyzed and re-build.

Couple pages back. Hope the link works.
I tried to upload hyper link but came up invalid.
Another member was helping me but I think I wore him out.
LOL

Couple pages back. Hope the link works.
I tried to upload hyper link but came up invalid.
Another member was helping me but I think I wore him out.
LOL
Link (http://www.audiokarma.org/forums/showthread.php?t=193991) fixed.

Link

(http://www.audiokarma.org/forums/showthread.php?t=193991) fixed.

Thanks Mark