I'll have a think more tomorrow... but it points to a design issue somewhere. The amp should be silent with the inputs shorted. Just its mains lead and speakers connected ?
Is the buzz "harsh" as if there are harmonics present. 50 hz mains "hum" is a very pure and deep tone. If it's harsh then its usually caused by ripple from the PSU entering the signal chain.
Is the amp all original ? No work done on the PCB's ?
If so my guess at the moment is that the grounding isn't correct and that the signal grounds have a ripple component passing through them.
If you imagine a short piece of wire or print that say links the the reservoir caps together then there is a small but measurable ripple voltage across that wire end to end due to the wire having a small resistance. If a signal ground is taken as one end and say a feed back return at the other then by shorting the inputs the amp can actually amplify that tiny ripple voltage and you hear it as a buzz.
Not a very clear explanation but you get the idea hopefully...
The fact that when you use the lower sensitivity inputs the buzz is less also confirms it's amplifying some internal "noise" on it's own ground paths.
Is the buzz "harsh" as if there are harmonics present. 50 hz mains "hum" is a very pure and deep tone. If it's harsh then its usually caused by ripple from the PSU entering the signal chain.
Is the amp all original ? No work done on the PCB's ?
If so my guess at the moment is that the grounding isn't correct and that the signal grounds have a ripple component passing through them.
If you imagine a short piece of wire or print that say links the the reservoir caps together then there is a small but measurable ripple voltage across that wire end to end due to the wire having a small resistance. If a signal ground is taken as one end and say a feed back return at the other then by shorting the inputs the amp can actually amplify that tiny ripple voltage and you hear it as a buzz.
Not a very clear explanation but you get the idea hopefully...
The fact that when you use the lower sensitivity inputs the buzz is less also confirms it's amplifying some internal "noise" on it's own ground paths.
Hi Mooly, yes just the mains lead and one bi-wired speaker connected, as far as I know it’s totally standard but to be quite honest I have looked at the soldering through the inspection hatch and although I’m no expert it looks shocking , I’ve only been soldering for the last few months but mine look a lot better.
BTW I have an arcam 200 AV box that I blew up , I was hoping to salvage parts from it to repair this amp. I have a Sony AV unit that I like for watching films etc so its not a loss to salvage it, do think the ground stages will be compatible?
BTW I have an arcam 200 AV box that I blew up , I was hoping to salvage parts from it to repair this amp. I have a Sony AV unit that I like for watching films etc so its not a loss to salvage it, do think the ground stages will be compatible?
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U said the amp was lying on loft for eight years...
First, let us know whether it was working properly the day it was stored.
With this, it will be clear if ageing of some parts is responsible.
First, let us know whether it was working properly the day it was stored.
With this, it will be clear if ageing of some parts is responsible.
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Hi , it was stored in the loft becaus eof the problem it has now
I'll strip the box tonight and put up some picture of the rear soldering.
I do have some pictures of the board and parts already..
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
I dont intend to hijack the OPs original concern, let me know if I should post this on another thread.
My MyRef 1.3 gives a buzz at two positions in the stepped attenuator only on one channel - the volume of music from the left speaker is subdued as it buzz'es. Bad resistors? Or a bad solder joint?
Thanks
-G0bble
My MyRef 1.3 gives a buzz at two positions in the stepped attenuator only on one channel - the volume of music from the left speaker is subdued as it buzz'es. Bad resistors? Or a bad solder joint?
Thanks
-G0bble
measure the resistance of the attenuator at the two suspicious positions.
It could just be dirt or corrosion holding the wipers off the contacts.
It could just be dirt or corrosion holding the wipers off the contacts.
Anyway I've decided to buy an interim AMP because I'm missing my music.. with my Arcam Blown my Qed buzzing I need to relax with sound / good tunes tonight , my local audio store has an CA 650a for £280 so i'll use that untill I can can fix and upgrade one or all of the amps.. then either sell it or attampt a LAMPIZING lol 🙂
So let the thread continue and my DIY virgin skills increase.. oh and fix the amp would be nice lol
So let the thread continue and my DIY virgin skills increase.. oh and fix the amp would be nice lol
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