My issue is different than that discussed on the oscillating tubes (as i understand it). I appreciate your input.
Equipment: 2 Manley Snapper power amps; just serviced
Connected: dedicated circuit for amps
Even with nothing else connected to the power circuit in the room, interconnects removed and every other breaker in the house tripped, I have a rhythmic hum on the speakers (low frequency) which coincides with changes in brightness of the EL34 tubes (blue fluorescence changes). Also bias changes in rhythm with the noise.
There are no ground loop issues (no noise except for this noise and the noise remains with nothing else connected, no interconnects). Also, problem happens on each amp even when only one of them is powered up and connected.
I also swapped tubes, outlets, connected to a remote circuit on the house (100 foot extension cord). I changed the breaker to a CAFCI breaker and checked all ground connections and ground rod.
I'm left to think I have an issue with incoming power (which FYI ranges from 125.1 to 125.4 volts).
I have tried HumX and also iFi Ground defenders with no improvement. I have ordered a Decware Zen Line Conditioner (long lead time) and a couple of VanAlstine Humdingers.
FYI, the amps don't have a mechanical noise (that I can tell).
HELP!
Equipment: 2 Manley Snapper power amps; just serviced
Connected: dedicated circuit for amps
Even with nothing else connected to the power circuit in the room, interconnects removed and every other breaker in the house tripped, I have a rhythmic hum on the speakers (low frequency) which coincides with changes in brightness of the EL34 tubes (blue fluorescence changes). Also bias changes in rhythm with the noise.
There are no ground loop issues (no noise except for this noise and the noise remains with nothing else connected, no interconnects). Also, problem happens on each amp even when only one of them is powered up and connected.
I also swapped tubes, outlets, connected to a remote circuit on the house (100 foot extension cord). I changed the breaker to a CAFCI breaker and checked all ground connections and ground rod.
I'm left to think I have an issue with incoming power (which FYI ranges from 125.1 to 125.4 volts).
I have tried HumX and also iFi Ground defenders with no improvement. I have ordered a Decware Zen Line Conditioner (long lead time) and a couple of VanAlstine Humdingers.
FYI, the amps don't have a mechanical noise (that I can tell).
HELP!
Oscillation or unstable circuitry. Not an AC line problem.
Why were they serviced? Was there a problem before that?
What does the service tech say about this? It's on him.
Was the servicing to restore it to factory spec, or a "mod" someone came up with?
If you have, or can get, a correct schematic, post it here.
Why were they serviced? Was there a problem before that?
What does the service tech say about this? It's on him.
Was the servicing to restore it to factory spec, or a "mod" someone came up with?
If you have, or can get, a correct schematic, post it here.
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Clearly the amplifier is oscillating. Perhaps a motorboating kind of oscillating. It would be intersting to know:
1.- Was the amp(s) being performing properly any time ago or it is so from the first time?
2.- The amp under question is DIY or marketed with a brand (and eventually a warranty)?.
3.- Can you post the circuit diagram or the model and brand?
4.- Is the amp properly loaded (Impedance, cables not too long, etc.).
1.- Was the amp(s) being performing properly any time ago or it is so from the first time?
2.- The amp under question is DIY or marketed with a brand (and eventually a warranty)?.
3.- Can you post the circuit diagram or the model and brand?
4.- Is the amp properly loaded (Impedance, cables not too long, etc.).
Contact their service dept. and tell them they screwed up and please fix them properly this time. 😉
jeff
I sent them over for removal of an inline fuse installed by the prior owner and ful check up. I asked to be brought to proper factory spec (remove inline fuse and replace factory fuse holders).
Both amps tested on spec; 2 tubes were replaced. I have full confidence on Manley.
Anyhow, if it were a faulty repair I would find it odd that both amps would be bad.
Noise is not motorboating (at least not in the usual sense, " prrr pup pup pup prrr" as my old AR amp used to do).
Schematics are copyright protected. There are some on the web but they are of modified Snappers: http://www.hbaudio.eu/Manley-Labs-snapper-reformed.html
Speaker cables are AQ Rocket 1.5 feet long spades; power cords are AQ also.
Both amps tested on spec; 2 tubes were replaced. I have full confidence on Manley.
Anyhow, if it were a faulty repair I would find it odd that both amps would be bad.
Noise is not motorboating (at least not in the usual sense, " prrr pup pup pup prrr" as my old AR amp used to do).
Schematics are copyright protected. There are some on the web but they are of modified Snappers: http://www.hbaudio.eu/Manley-Labs-snapper-reformed.html
Speaker cables are AQ Rocket 1.5 feet long spades; power cords are AQ also.
Likely that both amps would be unstable if they were both wrongly serviced/modified in the same way.
Contact the service person soon, before they have plausible deniability. Confidence is earned, not given.
If you still think the AC line is at fault, take them to another location miles away and see for yourself.
That old Acoustic Research amp had much trouble as well.
Contact the service person soon, before they have plausible deniability. Confidence is earned, not given.
If you still think the AC line is at fault, take them to another location miles away and see for yourself.
That old Acoustic Research amp had much trouble as well.
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Impossible. This should have shown up during any such test. All it does is call that assertion into question.
Haven't you ever had problems with getting your car repaired properly?
Maybe the regular guy is out, and the "other" guy has to do the repair.
Or it's Monday and he's hung over. Or it's Friday and he's in a rush to go somewhere.
These things do happen.
Maybe the regular guy is out, and the "other" guy has to do the repair.
Or it's Monday and he's hung over. Or it's Friday and he's in a rush to go somewhere.
These things do happen.
It may be rhytmical noise but the tube lighting variations are a dead giveaway.
Since both amps show the same effect and purpotedly not at the dealers's (but you never know as mentioned), did you try with another set of speakers?
I have a rhythmic hum on the speakers (low frequency) which coincides with changes in brightness of the EL34 tubes (blue fluorescence changes). Also bias changes in rhythm with the noise.
Jan
A low frequency oscillation that causes power surges.
The amp has problems, could be some changes in caps values or other "improvements". Restore to factory
configuration !
A thought: what are you driving these with? A DC coupled preamp?
Have you checked with a different preamp?
Jan
Have you checked with a different preamp?
Jan
It could be the mains periodic fluctuations. That happens in my house, along with a strange buzzing noise. It causes the operating point of my valve amp to fluctuate a little. Because of this I like tiring to design in stabilised supplies in to my amps! I live in a small village (city for US readers) on the end of a long wire a long way from a substation, this power is shared with my neighbours and a sewage pumping station, which I suspect is the cause of most of the problems.
Again, that should be easily measured. But you really think that is causes changes in brightness of the tubes?
Is your house lighting also varying brightness in sync with it??
Jan
Is your house lighting also varying brightness in sync with it??
Jan
The amps went back to the manufacturer not the dealer and were tested and the fuse holder modification (by a prior owner) corrected.
The problem sometimes starts upon powering up and sometimes it takes some time. Sometimes one amp would do it and not the other one.
I have not tested them with my other speakers; I will. My speakers are low impedance (Infinity IRS Beta and the tubes are on the mid/high towers).
I have big Threshold 12e on the bass towers which are connected to the same circuit but there is no noise on those (but those are solid state and have such huge transformers that its not the same).
I find the voltage at home to be higher than usual (lowest I have seen is 123 and as high as 125.7) per my DMM and also a Furman I have on the computer rack (BTW, different room and different circuit. I also have ground lifters on the incoming internet line and there is no internet connection to the amps. A separate system streams on wifi).
Peter, I agree with you and thus why I sent them back to the factory. To my ears, those amps are perfect as they come from the factory. No need to mess with them. Odd to say that on a diy forum.
All caps measured OK. I gave them a blank check to replace anything needed to bring them to full factory spec. They tested and said no changes were needed except a couple of tubes.
Speaking of tubes, I have swapped tubes between amps (no change) and also replaced the EL34 with new ones, no change.
In my case the power transformer is between mine and my neighbors house and I think feeds 5 houses (I'll go on an expedition to find out). Fairly large homes here with lots of HVAC equipment. I have requested a site test by the utility.
For your info, I have a whole house surge suppressor right next to the main panel. Ground lines are a very think gauge (1/3 of an inch or more). All gas, water and electrical is tied to a deep ground rod.
Jan, I run them with a Lexicon MC-1 for volume control but the noise is present with the interconnects disconnected at the amp's input.