[matt_garman]

After several weeks of using the SDS-470, I'm all but convinced it's a keeper.  I have an SMPS800R on order from Connex; I'm excited to see what this does for power consumption/efficiency.

My only concern now is that I sometimes hear a "pop" or maybe short burst of static when I turn the unit on.  I think it only comes out of one speaker, and it seems like it doesn't always happen.  It's not very loud, but loud enough to be heard.  I've temporarily moved back to my old amp, because I don't want to harm my speakers.  Any thoughts on what might cause this?

Also: I mentioned before there is a very faint amount of hiss coming out of the tweeters.  Originally I thought changing the input pots fixed this, but I was wrong: the hiss exists regardless of how the pots are set.  It's very faint, and really can only be heard when I have my ear a couple inches away from the tweeter.  Playing music at any level completely buries it.  Not a deal-breaker, but mildly annoying.  My old amp is completely silent.

[krikor]

Here are a couple pics I promised:

Which size Par-Metal case are you using? Is that the 5" or 4" tall version... 12"x16"?  I'm thinking of ordering a couple.

[Nick77]

Matt my amp is dead quiet and havent heard any feedback about hiss before. Maybe those rca input wires need shielding from the ps.

On another note these amps respond VERY well to after market power cords.

[ptempel]

Nice case there matt_garman.  I just pulled the trigger on the CDA-254L kit.  Got $11.25 off on it by using the ACircle promo code.  So shipping is free.  Ordered the connectors from Parts Express and am waiting to hear back from Par-Metal on their black anodized version of the 20 series desktop case.  Will see how it goes when all is delivered.  Have been waffling on building this amp so finally got off my gleuteus maximus and am going to do it.    It will be going up against an Adcom GFA-545ii amp so I expect it to lay down some smack on it.  Will see.

[mboxler]

Matt...

I have the same hiss/pop issue.  A couple of things I noticed.  The hiss was the same even when the rca cables were disconnected from the amp.  Also, the hiss would "almost" disappear when the pot was half way, but would reappear when the pot was turned all the way down.  I'm driving very sensitive Klipschorns.  When I hook up my Klipsch RF-83's (about 5dB less sensitive), the hiss is much less.  How sensitive are your speakers?  I wonder if the issue is only with very efficient speakers.

Mike 

[mboxler]

ptempel...

I also replaced my Adcom GFA-545ii amp with a CDA-224.  Even my wife noticed the difference...much more detail.  Now I'm considering replacing my Adcom preamp with ?????  Good luck!

Mike

[justinm]

I here the hiss in my tweeters also, older pair of B&Ws, not real efficient. Also heard the hiss with my Adcom 545ii when I was using it, about the same level. I am pleased with the SDS254 and SDS470 Im using now for the mains and subs. The only problem I have is the bass is so well controlled now that I lost quite a bit of extension at the bottom end. I plan on using passive radiators with the subs instead of their sealed box loading to get some lower bass. The bass went deeper with a pair of Dayton SA240 plate amps but was a lot slower with much less control of the cone I think. When I used the Adcom with the subs it was the first time I ever saw the distortion warning led's come on and it wasnt very loud.

[ptempel]

I also replaced my Adcom GFA-545ii amp with a CDA-224.  Even my wife noticed the difference...much more detail.  Now I'm considering replacing my Adcom preamp with ?????  Good luck!

Good going Mike.  I'm also going to use the Adcom GFP-555ii with it for a while.  From what I've read so far, I'd like to replace it with the Mezmerize DCB1 buffer.  Saw the boards available here:

http://www.diyaudio.com/store/usa/boards/p-mezb1-1v10.html

wushuliu has an AC thread on it here:

http://www.audiocircle.com/index.php?topic=85001.0

and the diyaudio build thread is here:

http://www.diyaudio.com/forums/pass-labs/176723-mezmerize-dcb1-building-thread.html

Hope that helps,
Philippe

[matt_garman]

Which size Par-Metal case are you using? Is that the 5" or 4" tall version... 12"x16"?  I'm thinking of ordering a couple.

It's the 4" tall version.  12x16x4.  Par-Metal part number 20-16124.

[matt_garman]

Matt my amp is dead quiet and havent heard any feedback about hiss before. Maybe those rca input wires need shielding from the ps.

I'm actually using XLR inputs.  At least the wire from the XLRs to the board is shielded.  I bought "25' 22 AWG Shielded Silver Kapton Teflon Wire 3 Twisted" from John's Wire Shop on ebay.

[matt_garman]

I have the same hiss/pop issue.  A couple of things I noticed.  The hiss was the same even when the rca cables were disconnected from the amp.  Also, the hiss would "almost" disappear when the pot was half way, but would reappear when the pot was turned all the way down.  I'm driving very sensitive Klipschorns.  When I hook up my Klipsch RF-83's (about 5dB less sensitive), the hiss is much less.  How sensitive are your speakers?  I wonder if the issue is only with very efficient speakers.

I'm using Salk Songtowers, which according to the specs aren't particularly efficient: 88 dB at 4 ohms.  Definitely less efficient than Klipschorns.

[roymail]

I'm using Salk Songtowers, which according to the specs aren't particularly efficient: 88 dB at 4 ohms.  Definitely less efficient than Klipschorns.

Matt, you have some Klipschorns?

[krikor]

It's the 4" tall version.  12x16x4.  Par-Metal part number 20-16124.

Thanks... Got a pair on the way for my monos.

[matt_garman]

Matt, you have some Klipschorns?

Nope.  But my understanding is that Klipschorns are famous for their high efficiency.

[mboxler]

I'm using Salk Songtowers, which according to the specs aren't particularly efficient: 88 dB at 4 ohms.  Definitely less efficient than Klipschorns.

Matt...

I noticed that Salk Songtowers can be ordered with Bi-wire capable binding posts.  Are you bi-wiring?  The reason I ask, is that the pop is "much" louder when I bi-wire (or in my case, passively bi-amp).  Running a single wire creates no pop at all.

Mike

[Æ]

the pop is "much" louder when I bi-wire (or in my case, passively bi-amp).  Running a single wire creates no pop at all.

I find that very interesting. Apparently the amp doesn't like the complex load of additional cabling, bi-wiring. I wonder if the amp would benefit from the addition of a Boucherot Cell.

[Æ]

My only concern now is that I sometimes hear a "pop" or maybe short burst of static when I turn the unit on.

In circumstances such as this, you might consider using some sort of active loudspeaker protection.
Circuitry that switches in the loudspeakers a few seconds after the amp comes on, allowing the amp to stabilize before sending power to the loudspeakers.

An inexpensive Velleman kit comes to my mind, there are others too.

http://www.vellemanusa.com/products/view/?id=350552

[ptempel]

I received the CDA-254 and and large PS modules last Friday.  They came pretty quick.  Still waiting for the Antec torroid transformer and a call from Par-Metal on the black anodized case.

[matt_garman]

I noticed that Salk Songtowers can be ordered with Bi-wire capable binding posts.  Are you bi-wiring?  The reason I ask, is that the pop is "much" louder when I bi-wire (or in my case, passively bi-amp).  Running a single wire creates no pop at all.

Nope, my are not bi-wire capable.  So, running single wire only.

[matt_garman]

In circumstances such as this, you might consider using some sort of active loudspeaker protection.
Circuitry that switches in the loudspeakers a few seconds after the amp comes on, allowing the amp to stabilize before sending power to the loudspeakers.

An inexpensive Velleman kit comes to my mind, there are others too.

http://www.vellemanusa.com/products/view/?id=350552

Is this kind of circuit typical in non-DIY amps?  I ask, because I've never had this popping issue before.  If it's a standard kind of thing, then I might consider it (e.g., any off-the-shelf amp I might buy---such as my QSC---likely has something similar).  But if it's not typical for an amp to have something like this, then it feels like a band-aid to me; I'd rather solve the real problem than throw more circuitry at the issue.

I also noticed that when I turn my SDS-470 off, one of the speakers makes a "farting" noise for about a second.  It's like a "rippling static" sound.  Fairly quiet, but similarly unsettling to the power-on pop/static.