OK, so I have this amp that I dug out of a console stereo. It's made by
Hoffman. It had these weird tone controls that had knobs inside the next
knob that affected each channel individually. Anyways they were a PITA and
I wanted to bypass them. So I started to unhook them and in the process
managed to break the source selector. So I removed the selector and the tone
controls and just soldered a single set of inputs right to where that whole
mess had connected to. I played the amp for awhile and it sounded great.
Then I noticed it seemed to start sounding garbled, especially during loud
passages. I don't have a schematic but I took some photos of the tone
controls and the area around the first input tube. The signal came in the
inputs in the rear and hooked up to the source selector, out of the selector
to each tone control and then out of each tone control, joined back
together, and into the spot I soldered the single set of inputs. Did I screw
up and leave something out that needed to be there? It sounded great for
maybe around an hour, now it starts to sound funky after only 3 - 5 minutes.
To sum up the signal went in / selector / tone / first 12AX7 / volume /
second 12AX7 / stereo mono switch / EL84.

The pictures are posted here http://truevaluecomputer.com/gallery/album11 .
If you click on a thumbnail the larger picture will come up, if you want it
full sized click on the larger picture and the full size picture will come
up. The full sized pictures are vary large so be patient. There are multiple
shots of each area, some with or without flash, choose the one that's
easiest for you to see.

If I can get this figured out my next project will be to remove the funky
stereo / mono, external / internal, speaker selector, on / off switch. I
want to have a strait forward stereo amp and a simple on / off switch. After
that I think I might try to find a nicer volume pot.

Thanks in advance for any suggestions or possible solutions.

Thanks,
Bryan
Durham, Oregon

I think I fixed it. I decided to try just strapping the inputs right to the
volume control and it seem to be working fine now. I guess having the CD
player going right into that first 12AX7 without what ever loss the tone
controls represented must have been overdriving the tube so on loud passages
it'd distort. Anyone got any opinions negative or positive on what I have
done?

TIA,
Bryan
Durham, Oregon.
"Bryan McGivney" wrote in message
...
OK, so I have this amp that I dug out of a console stereo. It's made by
Hoffman. It had these weird tone controls that had knobs inside the next
knob that affected each channel individually. Anyways they were a PITA
and
I wanted to bypass them. So I started to unhook them and in the process
managed to break the source selector. So I removed the selector and the
tone
controls and just soldered a single set of inputs right to where that
whole
mess had connected to. I played the amp for awhile and it sounded great.
Then I noticed it seemed to start sounding garbled, especially during loud
passages. I don't have a schematic but I took some photos of the tone
controls and the area around the first input tube. The signal came in the
inputs in the rear and hooked up to the source selector, out of the
selector
to each tone control and then out of each tone control, joined back
together, and into the spot I soldered the single set of inputs. Did I
screw
up and leave something out that needed to be there? It sounded great for
maybe around an hour, now it starts to sound funky after only 3 - 5
minutes.
To sum up the signal went in / selector / tone / first 12AX7 / volume /
second 12AX7 / stereo mono switch / EL84.

The pictures are posted here http://truevaluecomputer.com/gallery/album11
..
If you click on a thumbnail the larger picture will come up, if you want
it
full sized click on the larger picture and the full size picture will come
up. The full sized pictures are vary large so be patient. There are
multiple
shots of each area, some with or without flash, choose the one that's
easiest for you to see.

If I can get this figured out my next project will be to remove the funky
stereo / mono, external / internal, speaker selector, on / off switch. I
want to have a strait forward stereo amp and a simple on / off switch.
After
that I think I might try to find a nicer volume pot.

Thanks in advance for any suggestions or possible solutions.

Thanks,
Bryan
Durham, Oregon

We'd really have to see a schematic. My guess was motorboating of some sort
or overdriving, but if it's not ear-splitting loud, the latter can't be.

Tim

--
"I have misplaced my pants." - Homer Simpson | Electronics,
- - - - - - - - - - - - - - - - - - - - - - -+ Metalcasting
and Games: http://webpages.charter.net/dawill/tmoranwms

"Bryan McGivney" wrote in message
...
I think I fixed it. I decided to try just strapping the inputs right to
the
volume control and it seem to be working fine now. I guess having the CD
player going right into that first 12AX7 without what ever loss the tone
controls represented must have been overdriving the tube so on loud
passages
it'd distort. Anyone got any opinions negative or positive on what I have
done?

TIA,
Bryan
Durham, Oregon.
"Bryan McGivney" wrote in message
...
OK, so I have this amp that I dug out of a console stereo. It's made by
Hoffman. It had these weird tone controls that had knobs inside the next
knob that affected each channel individually. Anyways they were a PITA
and
I wanted to bypass them. So I started to unhook them and in the process
managed to break the source selector. So I removed the selector and the
tone
controls and just soldered a single set of inputs right to where that
whole
mess had connected to. I played the amp for awhile and it sounded great.
Then I noticed it seemed to start sounding garbled, especially during
loud
passages. I don't have a schematic but I took some photos of the tone
controls and the area around the first input tube. The signal came in
the
inputs in the rear and hooked up to the source selector, out of the
selector
to each tone control and then out of each tone control, joined back
together, and into the spot I soldered the single set of inputs. Did I
screw
up and leave something out that needed to be there? It sounded great for
maybe around an hour, now it starts to sound funky after only 3 - 5
minutes.
To sum up the signal went in / selector / tone / first 12AX7 / volume /
second 12AX7 / stereo mono switch / EL84.

The pictures are posted here
http://truevaluecomputer.com/gallery/album11
.
If you click on a thumbnail the larger picture will come up, if you want
it
full sized click on the larger picture and the full size picture will
come
up. The full sized pictures are vary large so be patient. There are
multiple
shots of each area, some with or without flash, choose the one that's
easiest for you to see.

If I can get this figured out my next project will be to remove the
funky
stereo / mono, external / internal, speaker selector, on / off switch. I
want to have a strait forward stereo amp and a simple on / off switch.
After
that I think I might try to find a nicer volume pot.

Thanks in advance for any suggestions or possible solutions.

Thanks,
Bryan
Durham, Oregon

Well like I said in the original post, the inputs went into the selector
then to the tone controls and then to the first 12AX7 then to the volume
control and off to the second 12AX7. Now I removed the first 12AX7 and put
the input right on the volume control and out of there to the second 12AX7.
Before the volume was pretty sensitive, I think it was pretty much all in by
1/3rd crank, now the volume is a lot more usable in that it needs a good
2/3rds turn before it's all the way up. If you look at the pictures you can
see that the way I had it hooked up there was only one resistor and a cap in
parallel between the input from the CD player and the pin going into the
12AX7. I don't know what sort of range one of those tubes is supposed to be
able to take? The problem with a schematic is I don't have one and am not
even sure about what model of amp I have so it's pretty tuff to look for
one. Thanks for the reply.

Bryan
Durham, Oregon.
"Tim Williams" wrote in message
...
We'd really have to see a schematic. My guess was motorboating of some
sort
or overdriving, but if it's not ear-splitting loud, the latter can't be.

Tim

--
"I have misplaced my pants." - Homer Simpson | Electronics,
- - - - - - - - - - - - - - - - - - - - - - -+ Metalcasting
and Games: http://webpages.charter.net/dawill/tmoranwms

"Bryan McGivney" wrote in message
...
I think I fixed it. I decided to try just strapping the inputs right to
the
volume control and it seem to be working fine now. I guess having the CD
player going right into that first 12AX7 without what ever loss the tone
controls represented must have been overdriving the tube so on loud
passages
it'd distort. Anyone got any opinions negative or positive on what I
have
done?

TIA,
Bryan
Durham, Oregon.
"Bryan McGivney" wrote in message
...
OK, so I have this amp that I dug out of a console stereo. It's made
by
Hoffman. It had these weird tone controls that had knobs inside the
next
knob that affected each channel individually. Anyways they were a
PITA
and
I wanted to bypass them. So I started to unhook them and in the
process
managed to break the source selector. So I removed the selector and
the
tone
controls and just soldered a single set of inputs right to where that
whole
mess had connected to. I played the amp for awhile and it sounded
great.
Then I noticed it seemed to start sounding garbled, especially during
loud
passages. I don't have a schematic but I took some photos of the tone
controls and the area around the first input tube. The signal came in
the
inputs in the rear and hooked up to the source selector, out of the
selector
to each tone control and then out of each tone control, joined back
together, and into the spot I soldered the single set of inputs. Did I
screw
up and leave something out that needed to be there? It sounded great
for
maybe around an hour, now it starts to sound funky after only 3 - 5
minutes.
To sum up the signal went in / selector / tone / first 12AX7 / volume
/
second 12AX7 / stereo mono switch / EL84.

The pictures are posted here
http://truevaluecomputer.com/gallery/album11
.
If you click on a thumbnail the larger picture will come up, if you
want
it
full sized click on the larger picture and the full size picture will
come
up. The full sized pictures are vary large so be patient. There are
multiple
shots of each area, some with or without flash, choose the one that's
easiest for you to see.

If I can get this figured out my next project will be to remove the
funky
stereo / mono, external / internal, speaker selector, on / off switch.
I
want to have a strait forward stereo amp and a simple on / off switch.
After
that I think I might try to find a nicer volume pot.

Thanks in advance for any suggestions or possible solutions.

Thanks,
Bryan
Durham, Oregon

CD players kick out at least three times the input expected from
old tube amps... maybe people run CD players right to power amps
without any pre-amplification!

If you wanted to keep the stock pre-amp sections, you could add
pots (50K would work) right after the "AUX" input to bleed off
most of the signal to gnd.