Bent Audio NOH question

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ARN

Bent Audio NOH question
« on: 20 Nov 2010, 12:06 pm »
Hi, i am new on this forum, and from Norway.

I have got a question about my NOH.
It is a copper version, and I am using the ballanced in and outputs.
When I turn the volumecontrol there is a cracking soung from my left speaker.
This also happens when I turn the 6db button.

Anyone understand what could be the reason to this?

I opened up my NOH and looked inside it.
Is it ok if the wires from the transformers to the attenuatur has no insulation, and is in physical contact with eachother. I think this looks strange.

Thanks for answers
Arild

Sonny

Re: Bent Audio NOH question
« Reply #1 on: 13 Jan 2011, 11:41 pm »
Arild,
The wires are fine, the copper wires used are insulated with a thin layer of polyurethane or something.  It won't short unless some of that has been burned or scrapped off.  I have a NOH too and the thing I would recommend is check to see if there are any shorts on the L channel selector switch....but it is normal to have a "click/pop" or something when changing inputs.
Tuan

denjo

Re: Bent Audio NOH question
« Reply #2 on: 14 Jan 2011, 12:25 am »
Arild,
The wires are fine, the copper wires used are insulated with a thin layer of polyurethane or something.  It won't short unless some of that has been burned or scrapped off.  I have a NOH too and the thing I would recommend is check to see if there are any shorts on the L channel selector switch....but it is normal to have a "click/pop" or something when changing inputs.
Tuan

Tuan, I was interested in your comment about the "clicks" and "pops" being normal! I have a TAP silver and the clicks and pops are driving me crazy! Sometimes it can be very loud and alraming, especially when the volume is high! I emailed John and he wanted me to check for dc leakage or something but I don't quite know how to check this out.

Arild, have you tried playing with the Ground toggle between "H" and "F"?

Sonny

Re: Bent Audio NOH question
« Reply #3 on: 14 Jan 2011, 12:32 am »
Denjo,

When I had the TAP-X, it did happen to me too, but only intermittently.  It was not too loud, but you are right, it is DC offset.  With the NOH, I still get that now and then, very minor, so I turn the volume down when I switch inputs.

T

John Chapman

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Re: Bent Audio NOH question
« Reply #4 on: 14 Jan 2011, 10:34 pm »
Hello!

Just spotted this one - a lot of stuff is answered above - such as the common question about the 'bare wires' - as above they are insulated and they just look bare. You are not the first to ask about that!

It sounds like the volume switch needs cleaning - since it is with the volume changes you get the noise and since it is only on one side. Just as a test swap the input cables from your source and make sure the nose stays on the left side. Pop the lid and spray some contact cleaner in there and give the volume knob a good spin back and forth.

Also as mentioned any DC offset at the source outputs can result in some noises when changing volume  - this is more pronounced with the super fast switching pickering relay based units (TAP and TAP-X) than it was with the slow switching manual based units like the NOH and the bent kit before it.  The faster that transition is the more of a tendency to click. Two things cause it - first the switching of any dc creates a quick jump in level that manifests itself as a click. Second the Transformers or Autoformers are an inductive load and quick removal of that dc offset creates a voltage spike (= click).  To check for DC turn the source on with the music paused and measure across the out jacks with a dc meter. 1 mV or 2mV is not uncommon but much more is not good.

If you get clicks when changing sources the same thing can cause it but it can be even more pronounced in the units that switch both hot and ground (the NOH typically was wired this way). It is great to isolate the sources entirely from each other but a side affect of breaking and connecting grounds (with their relative offsets) can be a click.  If it is extreme (Denjo - e-mail me again so we can sort that out!) it indicates severe offsets between sources and that is not good. Connecting up all the grounds inside will clean a lot of that up but at the loss of that isolation between sources.  Connecting the chassis ground from each source to a common point may also clean up those source to source offsets. Just turning down the volume a bit when switching sources is likely not a bad plan if you have any clicks. 

As a test try selecting between 2 unconnected inputs (even better if you short them out by connecting hot and ground at the input jacks for the test) - that should be quiet since they have no dc offset or signal present when switching.

Bottom line is there are a few different causes of the clicks and some (like a dirty switch) can be fixed up. Others like DC offsets or source to source ground offsets need to be dealt with 'at the source' so to speak.

Thansk!

John