[V-Duh]

I finally had some really good quality time to listen to my ASL amp and the HD600 cans. What did I hear in the background? Some stupid radio station!

What should I do under a budget?

I don't have any RFI on my A/V system. I'm using a Monster Cable powerbar with filtering. I know I can get a similar product for my headphone setup but I'm suspicious that this is not really going to be the answer.

Suggestions would be greatly appreciated.

 

[Killercrush]

Wrap your whole system with ERS paper !

Seriously, when did that began to happen ?

 

[V-Duh]

I've only had the amp and cans for a month or so. My first real critical listening was just recently when I had the house to myself for a few days.

I would guess that the RFI was there all the while. I seem to remember I once had a TV that picked up RFI too.

 

[V-Duh]

HELP! I think I heard the Carpenters last night...

 

[HumanMedia]

In order of priority (most important first)
*Get one or two of Alan Mahers "Power Enhancers", details and reviews are at Audio Asylum. They are broad spectrum RF frequency filters which are finely tuned RC networks which also remove DC offset and around $70 each. Highly recommended.
*In conjunction with the above use Hammond 193M chokes wired to a powercord and used in parallel to your AC outlets. (see details in Audio Asylum and Audio Circles)
*Get some shielded Volex power cables (try to get the old ones with the brass male prongs or get the Iron jelly fish variant)
*Put clip on ferrites at each end of all power cords to everything BUT your audio system. Especially items like fridges etc. Avoid on all audio equipment as these have an effect on the audible range.
*Wrap ERS paper around the ends and middles of all unshielded power cables and interconnects.

I am in direct line-of-sight to a radio repeater tower and doing all of the above has sweetened my sound beyond my expectations and I have no audio break though. Forget all other commercial filters as the above will have a better positive effect without the negatives of the well known audiophile filters (and will cost less!)

 

[rsaavedra]

I understand that an incorrectly soldered joint can pick up RF, and if in the signal path, it will polute your signal.

 

[V-Duh]

Quote:

Originally Posted by HumanMedia /img/forum/go_quote.gif In order of priority (most important first) *Get one or two of Alan Mahers "Power Enhancers", details and reviews are at Audio Asylum. They are broad spectrum RF frequency filters which are finely tuned RC networks which also remove DC offset and around $70 each. Highly recommended. *In conjunction with the above use Hammond 193M chokes wired to a powercord and used in parallel to your AC outlets. (see details in Audio Asylum and Audio Circles) *Get some shielded Volex power cables (try to get the old ones with the brass male prongs or get the Iron jelly fish variant) *Put clip on ferrites at each end of all power cords to everything BUT your audio system. Especially items like fridges etc. Avoid on all audio equipment as these have an effect on the audible range. *Wrap ERS paper around the ends and middles of all unshielded power cables and interconnects. I am in direct line-of-sight to a radio repeater tower and doing all of the above has sweetened my sound beyond my expectations and I have no audio break though. Forget all other commercial filters as the above will have a better positive effect without the negatives of the well known audiophile filters (and will cost less!)

Hey! Many thanks for the info. I've got a lot of research to do now.

I've just started looking around at Alan Maher's PE and some of the other ideas. I think the learning is half, or more, of the fun.

I'm surprised more people don't have this same problem, especially in urban areas.

 

[vcoheda]

i had this problem with an old corda amp. the problem had something to do with the way the amp was set internally, not my surroundings. i suspect the amp is the culprit in your situation as well. assuming you are going to keep the amp, i suggest if you don't already have good ICs and a sturdy power strip or console with EMI/RFI filtering. that helped me.

 

[dvw]

RFI comes from the air. If your AV system does not have it, then it's most likely the equipment that has a problem.

First disconnect the audio cable and see if you still have RFI problem. This is most likely the source. I have a feeling this is not your problem.

If RFI problem persists, then it's the equipment that does not have enough shielding. I don't think you want to fix this yourself. Just contact the manufacturer and have them fix it.

My guess is the cable to the tube stage is poorly shielded or broken. The manufacturer should be able to debug and fix the problem for you.

 

[V-Duh]

I'll start by trying to figure out if the noise is coming from the power or the air. Disconnect this, try that, etc. As suggested, it may be something simple, or it may be something requiring "higher power" assistance.

Thanks for the suggestions. I'm open to any more as well. Data is good...

 

[HumanMedia]

Yep, one major source is the air, and every part of your houses power cabling acts as an antenna, as well as your interconnects and equipment chassis. Every impedance node, such as a connector, creates nodes in the wiring which resonate with RF of that wavelength of that node. It is also generated inside your house by fridges, microwave ovens, wireless LANs, mobile phones and especially digital equipment with switching power supplies suchs as cd players, dvd players, projectors etc etc. Your cheap DVD player on standby can be dumping RFI into the power which is then picked up by other equipment. Even the LEDs in your equipment displays can be radiating RFI (holding a hand held radio infront of LED displays can sometimes reveal this quite alarmingly).

If you are near a radio/tv repeater the RF saturation can be so high it will exceed the normal range that a manufacturer will anticipate and other means to control and eliminate it will unfortunately be required.

 

[tbonner1]

First I would look for Ferrite bead wraps and put them around my interconnects.
Cheap but effective and have been used for years.

http://en.wikipedia.org/wiki/Ferrite_bead

 

[dvw]

Quote:

Originally Posted by tbonner1 /img/forum/go_quote.gif First I would look for Ferrite bead wraps and put them around my interconnects. Cheap but effective and have been used for years. http://en.wikipedia.org/wiki/Ferrite_bead

I agree this is a solution if the connector is the root cause. And over 90% of the time interconnect is the main contributor to the RFI problem. The reason I suspected the ASL amp is the problem is because he has no problem with his AV system. And vacuum tube amps are usually handcrafted. So very likely there might be cold colder joint or broken shield at the preamp tube stage. And that will be difficult to fix. (It can be done, but will require a technician's help and lot's of trial and error)

The best way to determine that is take out the interconnect and see if the RFI is still there. If not, ferrite will be the easiest fix.

 

[HumanMedia]

Quote:

Originally Posted by tbonner1 /img/forum/go_quote.gif First I would look for Ferrite bead wraps and put them around my interconnects. Cheap but effective and have been used for years. http://en.wikipedia.org/wiki/Ferrite_bead

Ferrites seem to have side effects that manifest in the audible range and IME should be avoided in sound applications (great for video tho and on all other equipment in the house). Also note that ferrite needs to be placed at the exact spots on the cable to really help with specific resonances (usually at the ends but not always). RC networks (capacitors with a resistor of the same impedance as the cable in series repeated x times in parallel with capacitors of values 2 orders of magnitude apart) are far better for power applications. (Like the Power Enhnacer above) A single rc application or ERS cloth wrapping the ends and centre is better for interconnects for non-shielded interconnects.

These solutions are preferable for audio than ferrites.

 

[velogreg]

Quote:

Originally Posted by HumanMedia /img/forum/go_quote.gif Ferrites seem to have side effects that manifest in the audible range and IME should be avoided in sound applications (great for video tho and on all other equipment in the house). Also note that ferrite needs to be placed at the exact spots on the cable to really help with specific resonances (usually at the ends but not always). RC networks (capacitors with a resistor of the same impedance as the cable in series repeated x times in parallel with capacitors of values 2 orders of magnitude apart) are far better for power applications. (Like the Power Enhnacer above) A single rc application or ERS cloth wrapping the ends and centre is better for interconnects for non-shielded interconnects. These solutions are preferable for audio than ferrites.

I have read many posts mentioning that ferrites are bad for audio applications but I am having great difficulty in comprehending this concept. How can a piece of metal that surrounds but does not touch a signal or current effect that signal or current? Seems a bit like audio voodoo in reverse.