[Æ]

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.

Well of course always better to pin down the source of the problem than band-aid it.

Farting noise? In electronics it is called "motorboating."
http://en.wikipedia.org/wiki/Motorboating_(electronics)

I'd say that switch on delay/muting circuits are fairly common. I guess it depends on the manufacturer. You'll see relays (you can hear them click on too) in a lot of higher powered receivers, Japanese named brands. Active protection circuitry, in case you try and use low impedance loudspeakers or have a short at the output.

[mboxler]

I have almost eliminated my popping issue, and I wanted to share my theory, just in case it's both correct and relevant.  First the boring history.  I've been trying to tri-amp, then bi-amp my modified Klipshorns.  The modification involved better (and much more efficient) midrange and tweeters, making the bass horn sound "smaller".  I came up with the idea of passively bi-amping my 'horns, which means running two amps (SDS-224's) into the bi-wire connections of my crossovers.  This would allow me to increase the gain on the bass horn to match the "too efficient" top-end.  The bass amp now runs thru a 2.3 mH inductor that connects to the 6 ohm woofer (1st order Butterworth 415Hz low-pass filter).   The second amp connects to a 48 uF capacitor (1st order Butterworth 415Hz hi-pass filter), then to the remaining crossover components and 8 ohm drivers.  With this configuration, I would hear a loud pop when the amps were turned on.  I just installed an active crossover, which eliminates these filters.  Now the pop has been reduced to a small click!  I'm no expert, but could the 48 uF capacitor have held enough of a charge to create a large discharge once the hi-pass amp was turned back on (causing the loud pop)?  The hiss is still there, but as before, only when I put my ear a few inches from the top-end.  Don't know why, but my popping issue is history.

Mike

[Æ]

I have almost eliminated my popping issue, and I wanted to share my theory, just in case it's both correct and relevant.  First the boring history.  I've been trying to tri-amp, then bi-amp my modified Klipshorns.  The modification involved better (and much more efficient) midrange and tweeters, making the bass horn sound "smaller".  I came up with the idea of passively bi-amping my 'horns, which means running two amps (SDS-224's) into the bi-wire connections of my crossovers.  This would allow me to increase the gain on the bass horn to match the "too efficient" top-end.  The bass amp now runs thru a 2.3 mH inductor that connects to the 6 ohm woofer (1st order Butterworth 415Hz low-pass filter).   The second amp connects to a 48 uF capacitor (1st order Butterworth 415Hz hi-pass filter), then to the remaining crossover components and 8 ohm drivers.  With this configuration, I would hear a loud pop when the amps were turned on.  I just installed an active crossover, which eliminates these filters.  Now the pop has been reduced to a small click!  I'm no expert, but could the 48 uF capacitor have held enough of a charge to create a large discharge once the hi-pass amp was turned back on (causing the loud pop)?  The hiss is still there, but as before, only when I put my ear a few inches from the top-end.  Don't know why, but my popping issue is history.

Mike

Did you check your amplifier output to see if there was any DC there?

Holding a charge? A crossover capacitor doesn't work that way, it's not for smoothing DC, it is frequency selective, blocks some frequencies, while passing others. We're talking about AC.

Wonder if the capacitor is problematic, leaky. Is the 48uF cap an electrolytic?

[mboxler]

Did you check your amplifier output to see if there was any DC there?

Holding a charge? A crossover capacitor doesn't work that way, it's not for smoothing DC, it is frequency selective, blocks some frequencies, while passing others. We're talking about AC.

Wonder if the capacitor is problematic, leaky. Is the 48uF cap an electrolytic?

No, didn't check for DC.  The caps are Solen FastCaps (Metallized Polypropylene???).   Holding a charge was probably a poor choice of words (I'm new at this stuff).  I can tell you this, I later went back to a single amp, single wire setup so I could "clean up my mess", and the first time I powered on the amp, I got the loud pop again!  Every time after that, no pops.  It's as if the inductor has to be in the mix when I power off, or I get the pop when I power on.  Since I won't be passively bi-amping, this will not be an issue.  I just wondered if this had anything to do with others having "popping" issues.

Thanks for taking interest in this.  I probably should have done more research before posting this idea.

Mike

[Æ]

No, didn't check for DC.
Mike

You really need to check out the amp first. DC at the output is easy to check for, if you have a semi decent digital multimeter.

[corndog71]

Have you tried that amp with any other speakers?

[justinm]

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.

Matt my 470 seems to be making the same sound when I shut it off thru the left chanel sub woofer. It sounds strange like some kind of static discharging in the left sub voice coil? I never noticed this with the SDS254 or my Daton 240 plate amps. Im not getting the turn on pop though, hope this amp lasts because I love the control it has over the drivers.

[djklmnop]

New to DIY.  I need advice!

Im probably going to end up picking up the CDA-254L.  Do you guys have recommendation to which chassis?  Tom has advised 12x12x4, but having never purchased a chassis before, can you guys give me some info?

* Do the Chassis comes with punched holes?
   - for binding posts?
   - for IEC Jack
   - Power Switch
   - LEDs?

[krikor]

The 12x12x4 Par-Metal chassis will work, but I went with the 16x12 to give myself a little more room in laying out the components and keep the power supply farther from the amp board.  Also allows for other possible upgrades in the future (power supply, volume control, etc.).  Chassis doesn't come punched for anything unless you special order it as such (costs extra). 

I've found them pretty easy to drill though I haven't gotten to the back panel yet.  Just finished laying out the base plate for my mono SDS-450 amps. Did them mirrored since they'll be positioned side-by-side or behind the speakers. This actually made it easier to lay out and drill the second amp... just clamped them bottom to bottom and drilled through the first (only two of the power supply screws had to be relocated since that board is not symmetrical).








I also drilled out the footer holes a little larger to accommodate some 1/4" shaft spikes I had on hand... I was only going to use three but found the amp too tippy with the big xfmr off to one side, so there's an extra hole at the front middle.

[hulkss]

The second amp connects to a 48 uF capacitor (1st order Butterworth 415Hz hi-pass filter), then to the remaining crossover components and 8 ohm drivers.  With this configuration, I would hear a loud pop when the amps were turned on.  I just installed an active crossover, which eliminates these filters.  Now the pop has been reduced to a small click!

Same experience here, I bypassed my compression driver protection caps and the turn on pop is almost gone.

[hulkss]

Matt my 470 seems to be making the same sound (farts) when I shut it off thru the left chanel sub woofer. It sounds strange like some kind of static discharging in the left sub voice coil?

Same problem here with a bridged sds-470.

Listen here: http://dl.dropbox.com/u/45539942/AmpShutDownNoise.mp3

You first hear the power switch snap off and then my subwoofer.

[djklmnop]

The 12x12x4 Par-Metal chassis will work, but I went with the 16x12 to give myself a little more room in laying out the components and keep the power supply farther from the amp board.  Also allows for other possible upgrades in the future (power supply, volume control, etc.).  Chassis doesn't come punched for anything unless you special order it as such (costs extra). 

I've found them pretty easy to drill though I haven't gotten to the back panel yet.  Just finished laying out the base plate for my mono SDS-450 amps. Did them mirrored since they'll be positioned side-by-side or behind the speakers. This actually made it easier to lay out and drill the second amp... just clamped them bottom to bottom and drilled through the first (only two of the power supply screws had to be relocated since that board is not symmetrical).








I also drilled out the footer holes a little larger to accommodate some 1/4" shaft spikes I had on hand... I was only going to use three but found the amp too tippy with the big xfmr off to one side, so there's an extra hole at the front middle.

Thanks!  I went ahead and ordered one a few days ago.

I am confused about the transformer.  So you have your Red and Black wires, but then there's also a purple wire.  Going to the power supply, you have the blue and green wires.  But what about the second set that is orange and brown?  According to other people's setup, they just tape over it.

Do I need to loop any of the orange / brown wires in closing them?

[mboxler]

Thanks!  I went ahead and ordered one a few days ago.

I am confused about the transformer.  So you have your Red and Black wires, but then there's also a purple wire.  Going to the power supply, you have the blue and green wires.  But what about the second set that is orange and brown?  According to other people's setup, they just tape over it.

Do I need to loop any of the orange / brown wires in closing them?

This is an e-mail I received from Tom a while back...

You might have received one of the transformers an extra shield, and this is the purple wire. If you're using a 3 prong power cord or IEC, connect the purple wire to the green (ground) wire. Your transformer might also have some brown and orange wires... just tape those off so each wire cannot touch anything and put them aside. They are not used in this kit.

Hope this helps.

Mike

[ptempel]

The 12x12x4 Par-Metal chassis will work, but I went with the 16x12 to give myself a little more room in laying out the components and keep the power supply farther from the amp board.  Also allows for other possible upgrades in the future (power supply, volume control, etc.).  Chassis doesn't come punched for anything unless you special order it as such (costs extra). 

I've found them pretty easy to drill though I haven't gotten to the back panel yet.  Just finished laying out the base plate for my mono SDS-450 amps. Did them mirrored since they'll be positioned side-by-side or behind the speakers. This actually made it easier to lay out and drill the second amp... just clamped them bottom to bottom and drilled through the first (only two of the power supply screws had to be relocated since that board is not symmetrical).

I second this and also went with the 12x16x4 Par-Metal black anodized case.  Just got almost all the wiring done last night.  Only thing left is the IEC ground wire to the chassis.  If you're careful with placement, you should be able to get up to two amp boards in this chassis.  You can place the torroid and power supply board near the front panel.  Then place each amp board close to the sides with the power and speaker connectors facing inward and the inputs close to the side of the case.  Then going from the edge to the middle of the back panel you can wire the RCA inputs, speaker binding posts and then the IEC connector in the middle.  The other side will mirror this setup (but in reverse).  I only have one amp board, but left plenty of space for a second one for possible future expansion (dual mono or 4-channel bi-amping, anyone?  ).  The PS board already has all the connections I need for the second board.

[ptempel]

Almost ready.  While ohming out the speaker and RCA connections, I found that the RCA positive posts have a connection to ground.    The Dayton RCA jacks have plastic washers but the one with the sleeve doesn't have much of a sleeve.  Its more like a bump.  I might have some teflon plumber's tape to wrap around the threads so they don't touch the case.  Will try that.

[srb]

I don't know that I would rely on a few wraps of teflon tape.  If you have a good sized Ace Hardware with hardware bins, you might be able to find some nylon shoulder washers with sufficient barrel length.
 
Steve

[ptempel]

I don't know that I would rely on a few wraps of teflon tape.  If you have a good sized Ace Hardware with hardware bins, you might be able to find some nylon shoulder washers with sufficient barrel length.

Sounds like a better idea.  Thanks Steve.  I also don't like the way the DVM is behaving.  So will hit up Rat Shack to replace the fuses (20A 250V and 500mA 250V fast acting) while I'm at it.

Philippe

[ptempel]

Its working!    The torroid is not heating up so looks like I have the center tap done correctly.  Initial impression is that it sounds a bit more detailed than the Adcom GFA-545ii.  Will put some more hours on it before I sub the Adcom back in.  Only minor complaint is a barely perceptible hiss from the tweeters when nothing is playing like others have mentioned.  One thing I did notice after replacing the DVM fuses and re-checking the connectors.  The black speaker binding posts have a path to the chassis.  It appears to be via the amp board and through the mounting posts.  Is this normal for the amp board?  The RCA connectors are ok after rechecking them as well.

[hulkss]

Matt my 470 seems to be making the same sound when I shut it off thru the left chanel sub woofer. It sounds strange like some kind of static discharging in the left sub voice coil? I never noticed this with the SDS254 or my Daton 240 plate amps. Im not getting the turn on pop though, hope this amp lasts because I love the control it has over the drivers.

You guys ever resolve the SDS-470 turn-off noise problem?
My amp at shutdown: http://dl.dropbox.com/u/45539942/AmpShutDownNoise.mp3

[justinm]

You guys ever resolve the SDS-470 turn-off noise problem?

Mine is still making the sound on shut off and a small pop when turned on. I hope it doesnt cause any damage to the amp, but the level of the sound is so low I just ignore it now.