[Felipe]

Hi guys,

I really am in a need of some pointers here, as i am not being capable of eliminating my LF55 noise.
I have built the AKSA100 in the past with no problems in this area, but i am in a different house with different AC mains now.

I built the LF55 with identicaly box construction and materials ( wooden box / no mains earth entry ).
With no input wire connected to the module, i get an annoying High Frequency noise mixed with some lower hum. Is the LF55 more susceptible to RFI than the AKSA100?
I dont know if this is a Mains Power problem...or rather the LF itself.

I installed some caps in across the mains...some 10uF+0,47uF+0,01uF : No luck - same noise.
I read this would reduce the RFI....seems it didnt work for me, or the RFI is not coming through the mains.

I could connect a capacitor between Mains Earth and LF earth....it helped in the GK1...i cannot connect MAins earth to anything else...i have all wooden box...nothing is metal...

any thoughts?
Thnks for the help!
Filipe

[AKSA]

Hi Felipe,

I'm back home from South Australia - just arrived tonight - I'm sorry to hear you are having these problems.

First:  disconnect the input at the pcb signal pins.  Does it still hum?  If yes, the problem is either the speaker leads, or the power supply, if no, the problem is induction in the signal input leads.

I will contact you by PM to take this further!

Cheers,

Hugh

[Felipe]

Hi Hugh,

Glad you are back...
The inputs leads are not connected. It still hums.

The output leads are just like the ones in the AKSA100....12AWG solid copper from Anti-Cable wire.

Filipe

[AKSA]

Hi Felipe,

Ah, we've hooked up immediately!

You mentioned in your email that when you turned off the mains, without the trafos the hum went away, and that clearly it's coming through the supply somehow.

The usual way to fix this is to wire in a power line conditioner, but since this problem appears to be unique there may be something more to it......

Is it still present if you short the signal hot to signal cold at the pcb?

The other possibility could be hum induction through the trafos, or indeed power wiring profiles on the AC side.

The LF normally has even lower noise than the AKSA, so while I try to keep an open mind I don't believe it's the modules.

Hope this helps, keep pluggin' away, we will get there!

Happy New Year!

Cheers,

Hugh

[Felipe]

Hi Hugh,

Sorry for the mixup and wrong info : I read in fact 10 ohms between input signal ground and star earth.
So no anomalies here....

If i shunt the input signal wires...connect hot to ground, the noise is still there and maybe a litle bit stronger. Nothing colossal but more apparent. Specially the High freqs that are quite annoying.

The power line conditioning you suggest is to filter my AC mains right? I think maybe i should look for the transformers first ? Apart from the Transformers ( wich are Avel Lindberg ) there is nothing different from the AKSA100. The Aksa100 uses 2 custom built transformers here in Portugal. The LF55 uses Avel Lindberg from UK. I thought they would be OK because i believe many have used them...

Any thoughts on what to check next ? I could take the trannies out of the box and put them 2 metres away....
Filipe

[AKSA]

Felipe,

Try connecting mains earth to star earth.

The LF is no more susceptible to RFI than the AKSA with the 160KHz input filter fitted.  Without it, it's a very broadband amp and will amplify up to RF - as you would expect from a wideband amp of course.

If this doesn't work, could you please send to me a complete set of photos so that I can study the wiring in depth?  This is a problem unique to your setup, and while it might reflect mains it might simply be an earth loop or some other wiring issue.

Cheers,

Hugh

[Felipe]

Hello all,

I am back to post some findings after close examination and carefully experimenting in various situations.
I have come to conclude that the ONE main problem i have at home resides in AC power. I believe i have dirty AC mains and everything, and i mean everything suffers from it. Let me give you examples :

- Transformers inside powerboard 220/12v, that feed my halogen lamps in the ceiling --> buzz/hum
- Radio Alarm clock in the bedroom never buzzed in the old house. Now sometimes it wont let me sleep!!
- Transformers in AKSA, Gk-1 and Squeezebox PS --> all of them hum
- My brand new TV LCD Philips 9731 - buzzes like a stupid bee
- and the list goes on...

So what i need is a new AC mains. Now, as i can't get that, i need to find a way to eliminate/minimize the noise in this one. Stereo+TV is the main bug. The others i can get around the problem. But audio/video system is very picky about filtering. Do you believe power conditioning is only way to go ? That can be expensive....

Ideas are welcome...Tx,
Filipe

[Seano]

It may be that the mains earth from the house powerboard is not the best.  This is not something that is a safe DIY fix.  It would be best to engage a sparky that is experienced in commercial fitout and data cable routing to have a squiz.  They may have some suggestions for a mains board overhaul.

[Felipe]

It may be that the mains earth from the house powerboard is not the best.  This is not something that is a safe DIY fix.  It would be best to engage a sparky that is experienced in commercial fitout and data cable routing to have a squiz.  They may have some suggestions for a mains board overhaul.

unlikely. most of home appliances i mentioned do not use GROUND :

- TV
- AKSA's
- Alarm clock
- Transformers for halogen lamps

All these are Ground free and still buzz....i had an idea of buying an UPS today and see if these small appliances like the TV or the Alarm clock stop buzzing when connected to the UPS.
I cannot connect my stereo to the UPS but it could indicate the mains are really dirty.

Question : Does a balanced power conditioner work/degrade/kill with the AKSA family ?
I believe Felicia is a small Squeezebox oriented Power Conditioner, can a bigger size be built to use with the AKSAs and Gk1 ? Or will this probably make the dynamics go away ?

Filipe

[AKSA]

Felipe,

It's clear to me that your appliances all hum because of DC on the line, though why the circuit I sent does not banish this DC residual is not clear to me.....

There may also be a lot of distortion on the mains waveform - this is due to saturation of the distribution transformers, and it produces harmonics of the mains frequency which can be problematic to eliminate.

I will think on this further, but it's looking as though EI transformers might be better, as they are much more difficult to saturate with DC on the line than toroidals.

Cheers,

Hugh

[rabbitz]

You can also get this problem with using several powerboards from the same power point. I've seen a buzz cured in the last week at a friend's house by using 1 powerboard instead of several.