I've got a McIntosh MA230 integrated amp. This amp has a tube power amp with a solid state pre-amp. I'm experiencing a buzz/hum through the speakers (Heresy 1) that increases as the volume is turned up. This happens when no audio sources are connected and when they are. When I turn off the speakers using the speaker switch on the amp and turn up the volume up all the way, there is a very slight, almost inaudible hum that I feel is consistent with the amp totally cranked. This is a 100 year old home so the wiring is anybody's guess, but I ran about 75 feet of quality extension cord into the basement an plugged the amp into an outlet connected directly into our electrical box which was upgraded maybe 25 years ago to breakers and current code amperage. I imagine this outlet is the "cleanest" in the house. The amp being from around 63/4 has a two prong plug and isn't designed for a 3 prong. Any ideas?
The volume control is between the preamp and power amp so if buzz increases with volume I would suspect something in the preamp. Have you ever had any restoration work done to the amp? If not I would start in the power supply and suspect an electrolytic capacitor failing.
If you here noise/hum with the speakers disconnected, that a whole other thing and probably mechanical hum from the power transformer, not unusual.
But it has nothing to do with the hum/noise from the speakers, so don't get mislead.
If you short the input connector, is the hum still there?
Jan
But it has nothing to do with the hum/noise from the speakers, so don't get mislead.
If you short the input connector, is the hum still there?
Jan
Where is the Volume control . . .
In the preamp?
In-between the preamp and power amp?
In the power amp? . . . (probably not).
You said you change the volume control rotation and the hum level changed.
and . . .
But changing the rotation of a volume control, normally does not affect the mechanical vibration of power transformers and chokes (when no signal/music is applied) . . . (listed in Post # 3).
I have never had to deal with 2 wire power mains.
All my power amplifiers have 3 wire Hot, Neutral, Ground power cords and wall power outlets.
All of my signal sources . . . turntable, phono preamp, tuner, and CD player have 2 wire plugs.
My 2 wire power cords are keyed (one spade is wider than the other).
Your power mains, wall outlets, and power cords . . .
Try reversing the power plugs in the wall outlets, one at a time (if they use equal spade width 2 wire power plugs).
With 3 devices, a signal source, a preamp, and a power amp, there are at least 6 combinations (9?) of plug orientations; so lots to try.
Build a matrix and write it down, my brain is toast right now, you do the work.
In the preamp?
In-between the preamp and power amp?
In the power amp? . . . (probably not).
You said you change the volume control rotation and the hum level changed.
and . . .
But changing the rotation of a volume control, normally does not affect the mechanical vibration of power transformers and chokes (when no signal/music is applied) . . . (listed in Post # 3).
I have never had to deal with 2 wire power mains.
All my power amplifiers have 3 wire Hot, Neutral, Ground power cords and wall power outlets.
All of my signal sources . . . turntable, phono preamp, tuner, and CD player have 2 wire plugs.
My 2 wire power cords are keyed (one spade is wider than the other).
Your power mains, wall outlets, and power cords . . .
Try reversing the power plugs in the wall outlets, one at a time (if they use equal spade width 2 wire power plugs).
With 3 devices, a signal source, a preamp, and a power amp, there are at least 6 combinations (9?) of plug orientations; so lots to try.
Build a matrix and write it down, my brain is toast right now, you do the work.
I am getting too old.
I should have seen:
'Integrated' amp
'Volume between preamp and power amp' (just like 99.9% of integrated amplifiers).
Sometimes for a preamp tube that has an un-bypassed cathode . . . if the filament insulation becomes resistive, it will transfer hum from th AC filament to the cathode.
Input ground loops are often a source of hum.
I should have seen:
'Integrated' amp
'Volume between preamp and power amp' (just like 99.9% of integrated amplifiers).
Sometimes for a preamp tube that has an un-bypassed cathode . . . if the filament insulation becomes resistive, it will transfer hum from th AC filament to the cathode.
Input ground loops are often a source of hum.
Important information to tell the doctor:
This is a new pain that I never felt before, or this has been bothering me forever.
Nothing has changed in the system, or I've added something new.
I have disconnected all wires from the device except mains power and speakers (which are just ordinary, floating, passive speakers). Or I haven't, but will immediately and report back.
All good fortune,
Chris
This is a new pain that I never felt before, or this has been bothering me forever.
Nothing has changed in the system, or I've added something new.
I have disconnected all wires from the device except mains power and speakers (which are just ordinary, floating, passive speakers). Or I haven't, but will immediately and report back.
All good fortune,
Chris