[hasekisgod]

Greetings,

  I finished (I thought) my amp last week and hooked it up in my system.  I have a one system does all set up. I listen to music with computer and combo player as sources, watch DVD's, and watch TV using the same amps (active xo tri amp set up).  When I fired up the Class D amp which I have hooked up to drive my mid range drivers sound was great but... it really degrades the picture quality on my TV!  Today I'm going to pull it out, pop it open, and install a Felix power conditioner in the case.  Hope that will help.  Any other suggestions would be appreciated.
Almost forgot.. the amp is the 250x2-500x1 kit which I see is now called CDA-254S.

Sincerely
boone

Do you have it in a wooden cabinet? Dont you have to use some type of metal to shield it? I would email tom and ask what is best. Do you have it next to your PC? if so thats why.

[boone]

hasekisgod,

Thanks for responding.  Wooden case but clad in copper sheet.  Not near my computer, so that's not it.  ????

boone

[hasekisgod]

hasekisgod,

Thanks for responding.  Wooden case but clad in copper sheet.  Not near my computer, so that's not it.  ????

boone

Did you email Tom on classdaudio site and ask him? He is very fast at reply.

[dewardh]

Wooden case but clad in copper sheet.

Does the shield fully surround the amp, and is it bonded to the power cord ground?  If it is, then there are really only three routes for switching noise to get out into the “real world": the power cord, the input leads, and the speaker leads.  The power cord is least likely, but it is directly connected to your other equipment (and sometimes noise can radiate from the grounded wire too).  Input leads are next least likely, but they too may be directly connected to other equipment.  Speaker leads are the most likely to carry noise (there is always some switching residual), but they generally don’t connect to anything (except speakers) so any noise from them has to be radiated . . . sometimes just re-routing them away from other equipment and cables can solve the problem.  The first test is simply to disconnect the speaker leads and see if the interference goes away.  If not, then try the input leads.  Once the “leak” is located there are different solutions, from bypassing to ferrite discs to shielded cable to try . . .

[J Payton]

Does anyone know if there will be a 250 watt 8 Ohm Super D (SDS-258)?

I have the CDA-258 and would want another amp similar to it.

[boone]

hasekisgod,
No, haven't talked to Tom yet.  Will intrude on his busy day when I have checked on a few more things.

dewardh,
We are thinking along the same lines.  My first thought was that the amp was somehow polluting my power so my response was to finally install a Felix in the box ( had skipped this initially because I was so anxious to get the amp up and running)  but..... found that when I disconected the speaker wires, the noise was significantly reduced.  But ( another one)... also noticed that plugging my cable box into a power strip that has some filtering/isolation capability  improved the picture somewhat.  Then I found that if I routed the cable signal thru my DVR the problem disappeared completely??????  So now I'm completely confused!  My problem with picture quality can easily be solved by routing the signal from the cable box to the TV using composite instead of coax ( seems like everyone knows this is a superior way to do it, but I didn't ), but.... I'm left with this nagging feeling that this noise from the ClassD Audio amp is having a subtle negative impact on my audio.  Guess I go ahead with the Felix in the amp case and will build a few more to isolate other components as I noticed a small amount of noise when switching other equipment on/off as well.  Have to think about how to accomplish shielding the speaker wires, that won't be so easy.  Any additional information or suggestions will be appreciated.

Thanks again
boone

[Bemopti123]

Boone, I was afraid of something like this when people were talking about this ClassD board.  Once again, I read that your case is made of wood lined with copper?  Can you give details about it?  How did you attach the copper to the wood?  How thick were the copper sheets and where did you get them?  I would also be nice if you can shoot a pic of the interior lay out for us people to see.

[boone]

Will take shots of exterior of case later today.

Thanks
boone

[DougSmith]

Why use copper to line wood cases? Aluminum would work just as well, is readily available at your local hardware store or home center and is much cheaper.

[srb]

Why use copper to line wood cases? Aluminum would work just as well, is readily available at your local hardware store or home center and is much cheaper.

A Faraday cage is built out of a conductive material, and the two best conductors are Silver and Copper.  Using Copper as a baseline (100%), silver only has 5% better conductance, so due to it's high cost, is out of the running.
 
Aluminum only has 60% the conductance of Copper, so at first glance, Copper might make a better cage.
 
But thickness also has an effect, so the first question would be:
1.  If the Aluminum thickness was increased to the point where it was the same cost as Copper, would it make a better cage?
 
The second question would be:
2.  Does the non-ferrous, non-magnetic properties of Aluminum provide a shielding advantage (or disadvantage) for some types of radiation?
 
My Audio Refinement amplifier touts it's all-Aluminum enclosure as a feature, but doesn't offer techincal explanations.
 
Marantz Reference series amplifiers tout an Aluminum top cover, a non-magnetic Aluminum case around the torroid transformer, and a double layer bottom plate with one of the layers Copper plated.
 
A lot of variables in materials, thickness and types of radiation, EMI, RFI, etc.
 
Steve

[Bemopti123]

Boone, that box is fascinating as I thought that main physical box would be wood and the inner lining would be copper but in your case, it is reverse.  That is something.  Would love to see that front face, and would still like details on copper sheeting thickness, where you got the sheet and how you decide to attach it.  For me, it seems as if you attached it physically and not by means of glue or anything.

[DougSmith]

A Faraday cage is built out of a conductive material, and the two best conductors are Silver and Copper.  Using Copper as a baseline (100%), silver only has 5% better conductance, so due to it's high cost, is out of the running.
 
Aluminum only has 60% the conductance of Copper, so at first glance, Copper might make a better cage.
 
But thickness also has an effect, so the first question would be:
1.  If the Aluminum thickness was increased to the point where it was the same cost as Copper, would it make a better cage?
 
The second question would be:
2.  Does the non-ferrous, non-magnetic properties of Aluminum provide a shielding advantage (or disadvantage) for some types of radiation?
 
My Audio Refinement amplifier touts it's all-Aluminum enclosure as a feature, but doesn't offer techincal explanations.
 
Marantz Reference series amplifiers tout an Aluminum top cover, a non-magnetic Aluminum case around the torroid transformer, and a double layer bottom plate with one of the layers Copper plated.
 
A lot of variables in materials, thickness and types of radiation, EMI, RFI, etc.
 
Steve

For general shielding purposes, I just don't think the differences will be all that significant. Most of the equipment available on the market today uses aluminum. Copper flashing is readily available, though, and would probably work OK.  I guess ferrous materials are used sometimes for transformer shielding, but I'm no expert.

[dewardh]

found that when I disconected the speaker wires, the noise was significantly reduced.  But ( another one)... also noticed that plugging my cable box into a power strip that has some filtering/isolation capability  improved the picture somewhat.  Then I found that if I routed the cable signal thru my DVR the problem disappeared completely?????? 

Cable drops are notorious for coupling noise/hum/whatever into audio systems . . . it would appear that you've found that your DVR has an isolation transformer in it  .  Running the speaker leads in the vicinity of the cable lead (especially if "bundled" for neatness) increases coupling between them.  It would be a good idea to add an isolation transformer at the wall plate (they're cheap, and may be free from your cable provider) to make sure you're not putting interference on the feed and disrupting your neighbor's service.

It sounds like you've got a handle on the problem and will get it resolved . . .

[Nick77]

Perfect timeing for my question, i am looking to mount my amp and power supply in a wood case and i picked up a 6x12 piece of 16 ga steel cause they didnt have any thick aluminum at lowes or HD. I thought i would mount it to the steel and then to the mdf. Did i just buy the wrong product?

[dewardh]

I thought i would mount it to the steel and then to the mdf.

It should work fine as a mounting plate.  The shield should surround the amp completely (bottom, top, sides) and be bonded to the power ground (not the neutral).  The shield doesn't have to be heavy gauge, or even solid . . . metal window screen, 1/4 inch hardware cloth or perforated sheet works fine, and allows for ventilation.  Leads passing in and out of the cage can be bypassed to it at the connectors.  Look at how it's done in commercial products.

In most cases none of this is necessary . . . just keep leads (especially speaker leads) short and away from other interconnects, and despite the modest noise emissions you won't have any problem.  Where there is interference, as in boone's case, just a little attention to shielding and grounding will almost always solve it.  Using a metal enclosure (and proper grounding) will avoid it altogether.

[roymail]

Question, my 2 channel system is no where near my TV/HT setup.  It's in another room down the hall.

Any chance I'll have this interference problem? 

[dewardh]

Question, my 2 channel system is no where near my TV/HT setup.  It's in another room down the hall.

Any chance I'll have this interference problem? 

There's always a slim chance of some bizare combination of circumstances . . . that's why Federal emissions standards are strict.  But the smart money will bet against it . . .

[mduckw01]

Does anyone know if there will be a 250 watt 8 Ohm Super D (SDS-258)?

I have the CDA-258 and would want another amp similar to it.

I have had this exact discussion with Tom, and there will be a 250 watts into 8 Super D series module... he's waiting on some parts to build the modules and to finish up testing.  He said he should have them in a couple of weeks.

[boone]

A couple of photos of the exterior.  Copper was salvaged from a kitchen remodel, don't know the guage, it was a 3"x8" duct that ran up through the roof.  Attached with brass screws, looking forward to the screws darkening up a little.  Thanks for all the help.  I really like this amp!






boone

[wushuliu]

A couple of photos of the exterior.  Copper was salvaged from a kitchen remodel, don't know the guage, it was a 3"x8" duct that ran up through the roof.  Attached with brass screws, looking forward to the screws darkening up a little.  Thanks for all the help.  I really like this amp!
boone

Far out. Looks like something from Doctor Who... maybe a Senso-Plasmatic Amplificator...