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DIYHiFi supply Lux91 Mono Max problems

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Dear All,

I think I need some help and have been trying different ways to resolve this. I might add I never get replies from Simon at DIY HiFi supply and find that rather disgraceful given the company took my money in good faith!

Anyhow I've had my Lux91 Mono Max amps for a while, but ever since I had them I've had distortion out of one amp that is not in the other. This same amp has now also started to hum. This issue I am hoping to resolve via help with a 6moons reviewer.

I have of course swapped everything possible in my system and the same issue remains in the same amp. This is a dynamic problem. In that at lower volumes all seems well (or cannot be heard). At higher volumes and for certain music (i.e. this seems to be frequency dependent in some way) the amps start to distort. I add I am not trying to over drive them, the other amp is perfectly fine and for quite a bit higher volumes as well. So something is breaking down but I do not know how to resolve this. Especially with DIY HiFi supply refusing to answer my e-mails

To resolve this issue I have bought power conditioning, screened power supply cables etc. etc. What I think I really need is to find someone who can assess these amps dynamically, across frequency ranges, to find the problem. Can anyone please help with this or advise who might be able to help. The sound of my amps is great when they both work, but something is wrong and I'd appreciate it enormously to finally get this sorted.

Thanks all, happy New Year, Jim

Follow Ups:

RE: DIYHiFi supply Lux91 Mono Max problems - Thorsten 13:44:14 01/06/14 (3)
Jim,
Distortion, would you mind being more specific?
The hum, is it mechanical (that is from the amplifier itself) or electrical (from the speakers)?

Ciao T

Sometimes I'd like to be the water
sometimes shallow, sometimes wild.
Born high in the mountains,
even the seas would be mine.

(Translated from the song "Aus der ferne" by City)

Edits: 01/06/14
- RE: DIYHiFi supply Lux91 Mono Max problems - jim.freer 14:14:28 01/06/14 (2)
  Hi Thorsten,
  
  Thanks for replying. The hum is definitely not mechanical, it's electrical and coming through the speaker on one side.
  
  The distortion is 'I simply cannot listen to this terrible quality' as if the amp is completely breaking down, particularly for female and mid range to upper range frequencies (mainly - but it could just be more obvious!). So like as if you have fuzzified and crackled up a voice or instrument, to the extent as if you were listening to a radio and started to lose the signal. It's not subtle, it's very obvious and ruins the sound quality completely. So clearly something is failing.
  
  Although I haven't tested this aspect to death I would argue on the evidence that this does not happen at the same volume when the amp is cooler and once you have run the amp at higher volume to cause this as you reduce the volume it takes a while for the amp to work again at lower volumes (whereas if you had not turned it up it would have not distorted). So this suggests perhaps a heating up issue that leads to a circuit breakdown somewhere.
  
  Any thoughts?, Jim
  - RE: DIYHiFi supply Lux91 Mono Max problems - Thorsten 23:11:46 01/06/14 (1)
    Hi,
    
    Definitly sounds like something is out.
    
    Can you test the DC Voltages according to the manual?
    
    Ciao T
    
    Sometimes I'd like to be the water
    sometimes shallow, sometimes wild.
    Born high in the mountains,
    even the seas would be mine.
    
    (Translated from the song "Aus der ferne" by City)
    - RE: DIYHiFi supply Lux91 Mono Max problems - jim.freer 01:11:14 01/07/14 (0)
      Hi Thorsten,
      
      Yes I can do this. I am going round to Chris's house tonight to double confirm issues in another system (I have done this once before). I don't have a multi-meter here but at my other house and will go down to this next week. When Brian was still around we did a bunch of voltage checks and as I remember this did not bring up anything obvious at the time. But I shall re-check these and send on.
      
      What I think I really need is for someone to swap out the individual modular boards in the amps and then see where the point of failure is. Or do more dynamic tests with output frequencies. But I need to find a qualified and skilled electronics person who can do that for me as a service. I have not found that person and Chris's suggestion from a few months back has apparently stopped doing that work. I was an electronics engineer in an earlier life but would prefer to put these in the hands of someone who is still experienced in this area and doing things now, I stopped this for an academic career some +20 years ago!!, cheers, Jim

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