[bagman]

Looking for thoughts on the following (also posted on alt.guitar.amps):

I have recently picked up a used (as if there's any other kind) Yamaha
T50C, the 50 watt version of the combo Soldano designed for Yamaha back
in 1990 or so. It has a low serial no., so by my reckoning, it's
probably 15-16 years old.

I find that when I dial the reverb up past 2-3, I get a sort of
harmonic/distortion buzz that really ought not to be there. This is
true in both the clean and the distortion channels, but unsurprisingly,
is more evident on the clean channel. Both channels have a separate
reverb pot, but each uses the same reverb driver. As far as I know,
and as far as the previous owner (who has owned the amp ten years)
knows, the only tubes ever to have been changed on the amp are the
output 6L6's.

My first instinct is to troubleshoot by swapping out the reverb driver
tube (a 12AX7) with a like tube, and I expect I'll do so - 12AX7's are
cheap, and access to the tube sockets is easy.

But my question (aha! he finally gets to it!) is this:

Is there any value to be gained by switching to a so-called cleaner
sounding tube? Specifically, a 12AY7 or a 12AU7? Is this actually a
BAD idea? I have read of others switching out the 12AX7 for some other
12xx7 variant where they wanted to lower the overall distortion level
with good results, but only in preamp stage applications, and never in
a reverb driver tube context.

Your thoughts are welcome.

Peace
Bagman

[Lord Valve]

bagman wrote:

Looking for thoughts on the following (also posted on alt.guitar.amps):

I have recently picked up a used (as if there's any other kind) Yamaha
T50C, the 50 watt version of the combo Soldano designed for Yamaha back
in 1990 or so. It has a low serial no., so by my reckoning, it's
probably 15-16 years old.

I find that when I dial the reverb up past 2-3, I get a sort of
harmonic/distortion buzz that really ought not to be there. This is
true in both the clean and the distortion channels, but unsurprisingly,
is more evident on the clean channel. Both channels have a separate
reverb pot, but each uses the same reverb driver. As far as I know,
and as far as the previous owner (who has owned the amp ten years)
knows, the only tubes ever to have been changed on the amp are the
output 6L6's.

My first instinct is to troubleshoot by swapping out the reverb driver
tube (a 12AX7) with a like tube, and I expect I'll do so - 12AX7's are
cheap, and access to the tube sockets is easy.

But my question (aha! he finally gets to it!) is this:

Is there any value to be gained by switching to a so-called cleaner
sounding tube? Specifically, a 12AY7 or a 12AU7? Is this actually a
BAD idea? I have read of others switching out the 12AX7 for some other
12xx7 variant where they wanted to lower the overall distortion level
with good results, but only in preamp stage applications, and never in
a reverb driver tube context.

Your thoughts are welcome.

Peace
Bagman


WTF is a "sort of harmonic/distortion buzz"?

Do you mean it hums? You said "buzz." That's different from harmonic
distortion.
"Harmonic/distortion" is unclear with that slash in the middle. What are
you
trying to say? Fine it down and I'll solve your problem for you.

Lord Valve
Expert

[bagman]

Well, my ear is not that well educated, nor is my pen, in these
matters, but I'll give it a try.

It sounds like a combination of something buzzing in the chassis, only
the sound is coming through the speaker, on the one hand, and on the
other, as though there is some harmonic distortion similar to what
you'd consider desirable with an overdriven tube amp - but only when I
turn up the reverb, and it's making the overall tone of the amp sound
fizzy. I am getting reverb, it's just got this background crud as
described above.

Maybe I'm describing two separate symptoms of two separate problems
that both occur at the same time.

Does that describe it better? I'm happy to elaborate if need be, and
thank you for responding so quickly.


Lord Valve wrote:
bagman wrote:

Looking for thoughts on the following (also posted on alt.guitar.amps):

I have recently picked up a used (as if there's any other kind) Yamaha
T50C, the 50 watt version of the combo Soldano designed for Yamaha back
in 1990 or so. It has a low serial no., so by my reckoning, it's
probably 15-16 years old.

I find that when I dial the reverb up past 2-3, I get a sort of
harmonic/distortion buzz that really ought not to be there. This is
true in both the clean and the distortion channels, but unsurprisingly,
is more evident on the clean channel. Both channels have a separate
reverb pot, but each uses the same reverb driver. As far as I know,
and as far as the previous owner (who has owned the amp ten years)
knows, the only tubes ever to have been changed on the amp are the
output 6L6's.

My first instinct is to troubleshoot by swapping out the reverb driver
tube (a 12AX7) with a like tube, and I expect I'll do so - 12AX7's are
cheap, and access to the tube sockets is easy.

But my question (aha! he finally gets to it!) is this:

Is there any value to be gained by switching to a so-called cleaner
sounding tube? Specifically, a 12AY7 or a 12AU7? Is this actually a
BAD idea? I have read of others switching out the 12AX7 for some other
12xx7 variant where they wanted to lower the overall distortion level
with good results, but only in preamp stage applications, and never in
a reverb driver tube context.

Your thoughts are welcome.

Peace
Bagman


WTF is a "sort of harmonic/distortion buzz"?

Do you mean it hums? You said "buzz." That's different from harmonic
distortion.
"Harmonic/distortion" is unclear with that slash in the middle. What are
you
trying to say? Fine it down and I'll solve your problem for you.

Lord Valve
Expert

[Phil Allison]

"bagman" wrote in message

I have recently picked up a used (as if there's any other kind) Yamaha
T50C, the 50 watt version of the combo Soldano designed for Yamaha back
in 1990 or so. It has a low serial no., so by my reckoning, it's
probably 15-16 years old.

I find that when I dial the reverb up past 2-3, I get a sort of
harmonic/distortion buzz that really ought not to be there.


** Find the reverb tank - a rectangular flat metal box with springs
inside.

Reverse the two RCA plugs in their sockets.

See what happens.





......... Phil

[Lord Valve]

If the reverb tank is not located within the chassis itself, find it
and rotate it 180 degrees in the horizontal plane. (Swap it left
end for right end.) See if this affects the hum level for the
better. Also, try swapping the leads. Examine the tank;
see if you have a disconnected spring. (Actually, do that
one first.) If you do, there is little chance that you will be
able to re-connect it, as the tinly hooks these springs
ride on usually break off when this happens. Also, make
sure that the small "corner" springs which suspend the
main spring assembly in the center of the tank have
not slipped out of their mounting holes on the tank
body.

What kind of tone are you getting when the reverb is
turned completely off? Decent? Still fizzy?

LV




bagman wrote:

Well, my ear is not that well educated, nor is my pen, in these
matters, but I'll give it a try.

It sounds like a combination of something buzzing in the chassis, only
the sound is coming through the speaker, on the one hand, and on the
other, as though there is some harmonic distortion similar to what
you'd consider desirable with an overdriven tube amp - but only when I
turn up the reverb, and it's making the overall tone of the amp sound
fizzy. I am getting reverb, it's just got this background crud as
described above.

Maybe I'm describing two separate symptoms of two separate problems
that both occur at the same time.

Does that describe it better? I'm happy to elaborate if need be, and
thank you for responding so quickly.

Lord Valve wrote:
bagman wrote:

Looking for thoughts on the following (also posted on alt.guitar.amps):

I have recently picked up a used (as if there's any other kind) Yamaha
T50C, the 50 watt version of the combo Soldano designed for Yamaha back
in 1990 or so. It has a low serial no., so by my reckoning, it's
probably 15-16 years old.

I find that when I dial the reverb up past 2-3, I get a sort of
harmonic/distortion buzz that really ought not to be there. This is
true in both the clean and the distortion channels, but unsurprisingly,
is more evident on the clean channel. Both channels have a separate
reverb pot, but each uses the same reverb driver. As far as I know,
and as far as the previous owner (who has owned the amp ten years)
knows, the only tubes ever to have been changed on the amp are the
output 6L6's.

My first instinct is to troubleshoot by swapping out the reverb driver
tube (a 12AX7) with a like tube, and I expect I'll do so - 12AX7's are
cheap, and access to the tube sockets is easy.

But my question (aha! he finally gets to it!) is this:

Is there any value to be gained by switching to a so-called cleaner
sounding tube? Specifically, a 12AY7 or a 12AU7? Is this actually a
BAD idea? I have read of others switching out the 12AX7 for some other
12xx7 variant where they wanted to lower the overall distortion level
with good results, but only in preamp stage applications, and never in
a reverb driver tube context.

Your thoughts are welcome.

Peace
Bagman


WTF is a "sort of harmonic/distortion buzz"?

Do you mean it hums? You said "buzz." That's different from harmonic
distortion.
"Harmonic/distortion" is unclear with that slash in the middle. What are
you
trying to say? Fine it down and I'll solve your problem for you.

Lord Valve
Expert

[bagman]

Thanks, Phil & LV, for your responses.

I'll try reversing the leads when I get home tonight, and see what I
get.

I believe the reverb tank is screwed to the floor of the cabinet
portion of the combo, so I can get at it without doing anything more
complex than removing the rear baffle board. If I find out I do not
have a disconnected reverb spring or corner suspension spring for the
entire assembly, and the leads are long enough, and if swapping the
leads does nothing, I'll try reversing the tank and see what happens.
I'll report my findings.

Also, in response to your other question, viz., how the amp sounds when
the reverb is turned down: It's kinda hummy, but the wiring in my
house is fifty years old - I haven't played it anywhere but at my
place, so I can't really isolate whether it's house current funk, or
the amp. My other amp (a Crate VC3112 about which I cannot say enough
good things) is also kinda hummy at home, but sounds good on the more
modern wiring at my neighborhood dive where I jam. But the Yamaha amp
otherwise generates acceptable (fizz-free) tone apart from the reverb
issue described above.

Thanks.

Ian

Lord Valve wrote:
If the reverb tank is not located within the chassis itself, find it
and rotate it 180 degrees in the horizontal plane. (Swap it left
end for right end.) See if this affects the hum level for the
better. Also, try swapping the leads. Examine the tank;
see if you have a disconnected spring. (Actually, do that
one first.) If you do, there is little chance that you will be
able to re-connect it, as the tinly hooks these springs
ride on usually break off when this happens. Also, make
sure that the small "corner" springs which suspend the
main spring assembly in the center of the tank have
not slipped out of their mounting holes on the tank
body.

What kind of tone are you getting when the reverb is
turned completely off? Decent? Still fizzy?

LV

[bagman]

I think I have resolution here.

I pulled the reverb tank out of its little vinyl bag in the floor of
the combo, and it was pretty clear someone else had done so also - and
put it back sloppily. It appears the springs were fouled by a flap of
the vinyl bag the reverb tank lives in. I laid the tank on the clean,
flat bench next to the amp and wound it up just about as loud as it
would go, and no fizz, buzz, or other sonic scuzz.

I did try reversing the leads, and wound up with no reverb signal at
all. The tank's jacks are clearly marked "input" and "output" so I'm
not surprised.

Just for fun I pulled and reseated each of the tubes, theorizing that
as long as I was about my investigation, I could look for any
discoloration or anything - found nothing, but at least I now know that
all the 12AX7A's appear to be original equipment tubes, all labeled
"Yamaha of America." Power tubes are, as the guy who sold me the amp
told me, fairly new Ruby 6L6's - not that anyone cares, right?

Anyway, thanks to both Phil and Lord Valve for the suggestions. It's
all cool now.

Peace

bagman


bagman wrote:
Thanks, Phil & LV, for your responses.

I'll try reversing the leads when I get home tonight, and see what I
get.

I believe the reverb tank is screwed to the floor of the cabinet
portion of the combo, so I can get at it without doing anything more
complex than removing the rear baffle board. If I find out I do not
have a disconnected reverb spring or corner suspension spring for the
entire assembly, and the leads are long enough, and if swapping the
leads does nothing, I'll try reversing the tank and see what happens.
I'll report my findings.

Also, in response to your other question, viz., how the amp sounds when
the reverb is turned down: It's kinda hummy, but the wiring in my
house is fifty years old - I haven't played it anywhere but at my
place, so I can't really isolate whether it's house current funk, or
the amp. My other amp (a Crate VC3112 about which I cannot say enough
good things) is also kinda hummy at home, but sounds good on the more
modern wiring at my neighborhood dive where I jam. But the Yamaha amp
otherwise generates acceptable (fizz-free) tone apart from the reverb
issue described above.

Thanks.

Ian

Lord Valve wrote:
If the reverb tank is not located within the chassis itself, find it
and rotate it 180 degrees in the horizontal plane. (Swap it left
end for right end.) See if this affects the hum level for the
better. Also, try swapping the leads. Examine the tank;
see if you have a disconnected spring. (Actually, do that
one first.) If you do, there is little chance that you will be
able to re-connect it, as the tinly hooks these springs
ride on usually break off when this happens. Also, make
sure that the small "corner" springs which suspend the
main spring assembly in the center of the tank have
not slipped out of their mounting holes on the tank
body.

What kind of tone are you getting when the reverb is
turned completely off? Decent? Still fizzy?

LV

[Phil Allison]

"bagman"


** Groper Alert !


I pulled the reverb tank out of its little vinyl bag in the floor of
the combo, and it was pretty clear someone else had done so also - and
put it back sloppily. It appears the springs were fouled by a flap of
the vinyl bag the reverb tank lives in. I laid the tank on the clean,
flat bench next to the amp and wound it up just about as loud as it
would go, and no fizz, buzz, or other sonic scuzz.


** Now put it back where it was a see what happens.

You have discovered nothing so far.



I did try reversing the leads, and wound up with no reverb signal at
all. The tank's jacks are clearly marked "input" and "output" so I'm
not surprised.


** Fools are not surprised by anything.

With the majority of reverb tanks, what you found is not the case -
since the impedances are much the same at both ends.





........ Phil

[Lord Valve]

bagman wrote:

I think I have resolution here.

I pulled the reverb tank out of its little vinyl bag in the floor of
the combo, and it was pretty clear someone else had done so also - and
put it back sloppily. It appears the springs were fouled by a flap of
the vinyl bag the reverb tank lives in. I laid the tank on the clean,
flat bench next to the amp and wound it up just about as loud as it
would go, and no fizz, buzz, or other sonic scuzz.

Put the tank back in.

See what happens to your hum level. If it goes back up,
rotate the tank horizontally. Whichever position gives you
the least hum, that's how it goes. In fact, you may want to
experiment with sliding the tank around in the bottom of
the amp - do this with the reverb turned all the way up,
but be *really* careful not to bump or jar the tank; when
you find the place in the bottom of the amp where the
hum level is lowest, screw the isolation bag down right
there. Your amp's power transformer radiates a hum
field, and the "output" side of the tank is very sensitive
to it.

Lord Valve
Expert

[bagman]

I put the tank back in and it works fine. I made sure no loose part of
the bag was tucked under the tank, and that the leads were firmly
attached before securing the bag to the cabinet. The last person to
work on this thing never pinned the isolation bag shut with the screws
again, so the tank was not even secured in the amp, really - just
sitting in the open bag (with the loose flap touching a spring or two).

The hum subsides considerably when I move the amp to another part of
the house - where the wiring is more recently installed (the last 5
years or so). I think it's also further away from the nearest power
pole mounted transformer. In the new location, the hum is no worse
than other healthy tube amps I've played through - I know these beasts
are rarely perfectly silent under the best of conditions, and this is,
to my ear, within acceptable limits.

The input lead is too short for me to rotate the tank 180 degrees in
the bottom of the amp, so that's out. Also, the tank itself is only
about 1/8" narrower than the inside of the cabinet on its long axis,
and there's only an inch or so of play front-to-back, and I've had no
difference of hum moving the thing forward or back, so sliding it
around in the cabinet is kind of a dead letter. In any case, I've had
no further fizz when reverb is turned up (the original complaint), so
I'm content to let this sleeping dog lie.

Thank you for the point about not jarring the tank while the volume is
maxed - I did that once years ago, and learned my lesson, but it never
hurts to have a safety reminder.

Thanks again to Phil and LV for your help. I'll update the group if
any further silliness ensues.

bagman


Lord Valve wrote:
bagman wrote:

I think I have resolution here.

I pulled the reverb tank out of its little vinyl bag in the floor of
the combo, and it was pretty clear someone else had done so also - and
put it back sloppily. It appears the springs were fouled by a flap of
the vinyl bag the reverb tank lives in. I laid the tank on the clean,
flat bench next to the amp and wound it up just about as loud as it
would go, and no fizz, buzz, or other sonic scuzz.

Put the tank back in.

See what happens to your hum level. If it goes back up,
rotate the tank horizontally. Whichever position gives you
the least hum, that's how it goes. In fact, you may want to
experiment with sliding the tank around in the bottom of
the amp - do this with the reverb turned all the way up,
but be *really* careful not to bump or jar the tank; when
you find the place in the bottom of the amp where the
hum level is lowest, screw the isolation bag down right
there. Your amp's power transformer radiates a hum
field, and the "output" side of the tank is very sensitive
to it.

Lord Valve
Expert