Hello! I have an old yamaha A-1020 integrated with both channels shot but I would still like to use it as a pre amp ,is it possible to bypass the amp section ? it has accessory jacks in the back which are not pre outs can they be converted to use as pre out some how?
It probably doesn't actually have a pre section, but more like a volume control and source selector. This was standard practice around the time this came out.
The accessory jack goes right in front of the volume control. If you move it to after (and cut the signal to the power amp area), you can use this as a passive pre/source selector.
The accessory jack goes right in front of the volume control. If you move it to after (and cut the signal to the power amp area), you can use this as a passive pre/source selector.
Not sure how to do that would it be possible to show me this link has a schematic of the amp thanks Yamaha A-1020 | Owners/Service Manuals, Schematics, Free Download, Reviews | HiFi Engine
You can not use preamp section without modyfication cause preamp section (bas treble etc) is going threw NFB loop.
In my opinion it would be highly recommended to fix this amp. I got this amp 10 yeares ago and it was really stunning amp for the money.
In my opinion it would be highly recommended to fix this amp. I got this amp 10 yeares ago and it was really stunning amp for the money.
I know it has to be modified but don,t know how to do it if someone can explain or show it would great thanks moe
As I mentioned, you'll only ever be able to use the volume control and source selector. Everything else is part of the power amp.
Just trace the wire that goes to the accessory jumper, and move it to the end of the volume control potentiometer (replace it with the wire that's currently there).
But: As borys said, this is an excellent amp and you're highly unlikely to hear any sort of improvement in case you switch to a different power amp. I would just use it as is and be happy with it. You pretty much cannot do better.
Just trace the wire that goes to the accessory jumper, and move it to the end of the volume control potentiometer (replace it with the wire that's currently there).
But: As borys said, this is an excellent amp and you're highly unlikely to hear any sort of improvement in case you switch to a different power amp. I would just use it as is and be happy with it. You pretty much cannot do better.
Yes I will eventually repair it but i have a yamaha m-40 power amp so just want to use the preamp section of the a-1020 for now thanks
So if I understand correctly it will be only for volume control i will not be able to adjust the filters ,tone and balance .
You will be able to use volume, high filter, balance, loudness, mono/stereo switch and of course the RIAA stage.
just opened it up off the volume potentiometer there is two leads one going to the main and one coming from the main and on the accessory jacks [send & receive] there's is two leads also one going to the main and the other coming from the main so i just switch them is that what you mean?
That isn't the schematic diagram you have posted, its a wiring/assembly diagram but the descriptors don't equate to what you think. The main in/out connections refer to tone control connections within the power amplifier and are not to do with signal in or out. If you can't follow this on the actual schematic (pages 7-10 of the service manual) you are in too deep to for your schematic reading skills which would show you how this all works in its very strange way. This is a complex amplifier and the wiring between boards is even more complex and obviously confusing.
If you want to avoid complexity and simply extract the output from the volume controls, take leads directly from the centre leg of each volume control pot. Use shielded wire and ground the shield to signal ground (at the lowest setting end terminal of the volume pot.). You could make use of currently unused sockets on the rear panel to connect these leads to your amplifier, removing the present soldered connections and taping them up safely, should you wish to refit them.
For safety, I would fit a 1uF film cap in the signal line to the socket, and also a 100k 0.25W resistor across signal to ground connections. Those sockets should also be relabelled "pre-out" in case someone forgets or simply doesn't know what's going on there in the future.
As others have said already, this is not a regular amplifier and the tone controls are wired into the power amplifier, making a confusing mess of connections into and out of the amp. The names of connections have been applied with confusing similarity to other terms which means you can't fit them willy-nilly to whatever you think seems ok, without the consequence of further accidents and real problems when it comes to repairs. Cut your losses now and either repair the amp properly or just tap into the volume control as suggested here.
If you want to avoid complexity and simply extract the output from the volume controls, take leads directly from the centre leg of each volume control pot. Use shielded wire and ground the shield to signal ground (at the lowest setting end terminal of the volume pot.). You could make use of currently unused sockets on the rear panel to connect these leads to your amplifier, removing the present soldered connections and taping them up safely, should you wish to refit them.
For safety, I would fit a 1uF film cap in the signal line to the socket, and also a 100k 0.25W resistor across signal to ground connections. Those sockets should also be relabelled "pre-out" in case someone forgets or simply doesn't know what's going on there in the future.
As others have said already, this is not a regular amplifier and the tone controls are wired into the power amplifier, making a confusing mess of connections into and out of the amp. The names of connections have been applied with confusing similarity to other terms which means you can't fit them willy-nilly to whatever you think seems ok, without the consequence of further accidents and real problems when it comes to repairs. Cut your losses now and either repair the amp properly or just tap into the volume control as suggested here.
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