kale-salad
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- Jul 18, 2021
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Hello all. Will do my best to explain and ask since this may be completely 100% normal for the 50/50 power amp. This one is from 1991, the original "Fifty/Fifty" with the F-F serial and 4x 6L6 and 3x 12AX7.
First off, it sounds KILLER. Love the sound.
When power and standby are on and the amp is live, there is a noise while it is idle. A hum/buzz/like a very low version of when you touch the end of your TS guitar cable.
I am only using input A and output A into an 8OHM cabinet. Because of that, Channel B volume is all the way at 0 same as Presence for B.
When I remove my preamp from the INPUT A, the idle hum/sound actually gets a tiny bit louder. This is not a deafening horrible sound, but since my cabinet is very close to me, it is audible over my keyboard typing and certainly a distraction. When the amp is put into standby, it is of course totally silent.
I have tried swapping the power tubes around, no difference. I removed all 3 12AX7 tubes and when it is powered fully with all of those 12AX7 removed it is completely silent (was expecting that). I added the first 12AX7 back, powered on, completely silent. When I added the SECOND 12AX7 tube, that is when the noise comes back. I swapped the tubes in every way possible, the noise is still there so I don't think it is a 12AX7 tube doing it?
Flipping the ground switch makes no difference. Hi or Lo power makes no difference. The Channel A volume is very low, it is by no means cranked. I even removed the power tubes from Channel B and also makes no difference. I have tried evrything i cn think of and have isloated the sound totally to the power amp itself. No preamp or effects or anything in the chain while trying to isolate - just the Channel A 8 ohm out into a 1x12 8ohm cabinet and a preamp connected to Input A (and also not connected to Input A).
TL
R version - Is the Fifty/Fifty from 1991 known to be a bit noisy when "idle"? My Mark 5 25 head is TOTALLY quiet and makes zero hum or buzz.
Thanks.
First off, it sounds KILLER. Love the sound.
When power and standby are on and the amp is live, there is a noise while it is idle. A hum/buzz/like a very low version of when you touch the end of your TS guitar cable.
I am only using input A and output A into an 8OHM cabinet. Because of that, Channel B volume is all the way at 0 same as Presence for B.
When I remove my preamp from the INPUT A, the idle hum/sound actually gets a tiny bit louder. This is not a deafening horrible sound, but since my cabinet is very close to me, it is audible over my keyboard typing and certainly a distraction. When the amp is put into standby, it is of course totally silent.
I have tried swapping the power tubes around, no difference. I removed all 3 12AX7 tubes and when it is powered fully with all of those 12AX7 removed it is completely silent (was expecting that). I added the first 12AX7 back, powered on, completely silent. When I added the SECOND 12AX7 tube, that is when the noise comes back. I swapped the tubes in every way possible, the noise is still there so I don't think it is a 12AX7 tube doing it?
Flipping the ground switch makes no difference. Hi or Lo power makes no difference. The Channel A volume is very low, it is by no means cranked. I even removed the power tubes from Channel B and also makes no difference. I have tried evrything i cn think of and have isloated the sound totally to the power amp itself. No preamp or effects or anything in the chain while trying to isolate - just the Channel A 8 ohm out into a 1x12 8ohm cabinet and a preamp connected to Input A (and also not connected to Input A).
TL
R version - Is the Fifty/Fifty from 1991 known to be a bit noisy when "idle"? My Mark 5 25 head is TOTALLY quiet and makes zero hum or buzz.Thanks.
