[Goobley]

Ok, I'm a picky person - not so much when it comes to audio quality, but when it comes to various background noises.
 
I recently finished building my CK2III and have been very impressed with it, however I have a few background noise issues.  I'm going to enumerate them in order of importance so that we can try and look for the solutions.
 
This testing has been done with my srh440 because it's very good at picking up noise that shouldn't be there
 
1) A high pitch whistle occurs when the pot gets over about 30% of its turn. This whistle is about 3kHz and highly irritating. When the pot gets to about 90% the whistle disappears and is just replaced by the background static one would expect at such a high volume. The whistle reduces in volume if I touch the case and goes away properly if I hold it (i.e. a good grip with at least two fingers)
 
2) Interference when my hand gets near the pot, it's an alps blue velvet 50k, it's grounded from one of the rear screws to the star ground, I measure 0.8R impedance to ground from the front of the spindle, so I believe that it's appropriately earthed. What gives? 
 
3) A tinsy winsy bit of toroidal interference, only really noticeable when the pot is at its minimum. I'm not worried by this but I'm thing of shielding the toroid with steel plate (0.8mm) - and then obviously holding it down with a plastic bolt to avoid a shorted turn. Do you think it's make a difference? The noise is abpout the same volume as music (from a 2V p-p source) with the pot at minimum, yeah that quiet, that's why I'm not really worried about this one.
 
Pictures of the build are here: http://imageshack.us/g/1/9858730/ sorry about the poor quality.
I've tried rotating the toroid and it makes very little difference, unless obviously the rca jacks are in plane with the wires coming out of the toroid. The red tape is gone now, I thought the wires were picking up noise from the output BJTs but I don't really think that's possible. I have been discussing some of these issues on amb's forum but thought that I would also open the discussion here as this is much more general diy than amp specific. That topic is here http://www.amb.org/forum/output-transistor-heatsinking-t2031.html .
 
I'm thinking of trying a ground breaker from the star ground, I doubt it would achieve anything though as my main source isn't grounded.
 
Like always, any help and advice you can offer is very welcome, I can't however move the toroid to a different box, but I can encapsulate it in steel within this one.
 
Cheers,
Chris

 

[fubar3]

Your image page is dark and linked to "party poker". For DIY here it is best to select an amp which many other people have done successfully like "O2", "PIMETA", "CMOY" ..
 
Anything with a torroid sounds expensive and perhaps has more components then are needed for good quality and a satisfactory result.

 

[Goobley]

Sorry about the image page, I only uploaded them there as I couldn't see how to do it directly when I was on the amb forums. Anyway I plugged it into my kitchen area last night and then left it to warm up for a few minutes and it was as clean as the proverbial whistle. Sounds more like the earth in my room is dodgy rather than the amp build. I'll get it looked at.

Cheers

 

[nikongod]

The problems sound more like generic amp problems, and not ckkiii problems.
 
Is the face of the pot grounded? It looks like you have a plastic front panel - this is a common mistake. Try connecting a SHORT bit of wire from the headphone jack ground to the face of the pot - or the knob. If the hum goes away make this permanent.
 
Can you move the transformer WAY over to the (left?) away from the RCA jacks? This may require moving the safety ground and sliding the PCB forwards in the case. 
 
You can buy little rubber boots to cover the back of IEC inlets. Much cleaner looking and safer than tape.
 
Quote:

For DIY here it is best to select an amp which many other people have done successfully like "O2", "PIMETA", "CMOY" ..

 
 
Many people have built Ckkiii. More power to him for building something slightly out of the norm. 
 
I would say the O2 and Pimeta are about the worst DIY amps to build - although they usually work right and sound like they measure well you seldom learn anything for building them. 
 
Cmoy is a sucky amp (it really is) but there is ample room for learning when building one. 
 
Quote:

Anything with a torroid sounds expensive and perhaps has more components then are needed for good quality and a satisfactory result.

 
This is just silly. 
Toroidal transformers are so popular because they are less expensive than EI transformers. 
 
On a certain level I do agree (most headphone amps are far more complicated than necessary), but overall I'm sitting here saying dafuq? for your reasoning & justification of that. 

 

[Goobley]

Thanks Nikon, they are indeed generic problems, I do have proper shielded crimp connectors on the iec now. I just hadn't put them on before the photo. The pot is grounded from te screw on the back to star ground. (0.5R from front face to ground)

I'm fairly sure now that the problems come from the ground in my room as in multiple other power points in different place it has been silent. Obviously sorting that out is a job for a qualified electrician, but does anyone have any ideas as to why the ground would vary so much throughout a building?

Cheers

 

[fubar3]

Quote:

that out is a job for a qualified electrician, but does anyone have any ideas as to why the ground would vary so much throughout a building?
Cheers

Aluminum wire perhaps?  Each power socket has screws to pin down the wiring. Of course, they must be tight. The ground wires of every socket is fed back to a common point on the circuit breaker panel, as far as I know.
 
All of the entertainment equipment I have has 2-wire plugs or wall-warts. Only the computers have 3-wire plugs. 
 
If you are feeding the 120vac into your DIY, there is some risk of shock. Also, certification to safety standards might be an issue.

 

[fubar3]

 
>>On a certain level I do agree (most headphone amps are far more complicated than necessary), but overall I'm sitting here saying dafuq? for your reasoning & justification of that.
 
A person is more likely to get help if he asks about something well-known.