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Mark2727 22nd February 2013 12:24 AM

Power up - loud snap
Hi Everyone,

I just completed Jerry's Electronics Class D Amp. It makes a loud snap upon turn on. Ouch!!

What to do about that? :confused:

Here's the link. Be sure to check out the build manual link near the bottom right for details on the schematic.

DIY Electronics KAA03021 Kit

Thanks for any ideas to help me solve this problem.

adason 22nd February 2013 01:08 AM

use delay

nigelwright7557 23rd February 2013 09:35 PM

I had a similar problem with irs2092 based amps only it was on power down I got a huge thump or a siren type noise. I fixed it with a small PIC micro monitoring the psu and holding the 2092 in reset if the psu was too low.

You could try an RC on the shutdown pin to hold the chip off until power supply settles.

vacuphile 23rd February 2013 10:41 PM

Otherwise, how do you like the sound?

tauro0221 23rd February 2013 10:46 PM

What happen with the mute? Are they are using the mute circuit?

Mark2727 24th February 2013 12:02 PM


I'm not understanding what you did. Could you give me a sketch and do you mean by "PIC", a printed integrated circuit?

Vacuphile I think the sound is ridiculously good for under $25, and really worth more money. I find everthing to be balanced and with no listener fatigue. Everything sound fast and detailed but not harsh. Two issues are this turn-on snap and also a small (and I mean really small) bit of background hum. I may up the value of the 470uF power supply capacitors to 1,000 uF if I get the go-ahead from someone more knowledgeable than I. Wouldn't you know it? I don't have any in the parts bin! This may only be an issue because I run La Scalas and they are really efficient. Bottom line: This was really easy to assemble, sounds great, and is a bargain.

tauro I don't know for sure, but I guess they are not. I'm no expert for sure, but I can see the circuit is pretty basic (and no doubt that's why it sounds so good). Sad part is I'm not getting much help from Jerry - he just says he's working on a solution. So, I'm just NOT turning the thing on and off at all really -- let 'er rip with my Pass B1 buffered preamp. Both amp and preamp use little electricity, so what the heck.

I have a delay device, but I couldn't get a measurement on it when I hooked it up, and the more I think of it, it probably would not work in this application anyway. Those are for tube filaments, then delay the main B+ power. So, you'd still get a big power "in" with this Jerry's Amp, only 40 seconds later. Right?


Mark2727 24th February 2013 12:10 PM

PS: It was suggested to me to put a capacitor across the power on/off switch. This of course, did nothing!

Additionally, I can tell you fellows that I'm awaiting a better power supply than what I've temporarily rigged. I ordered one of those sort of open cage looking affairs with the jacks to screw in your wiring. 24VDC, 2 amps. That was supposed to be here yesterday. Oh well. For the meantime I'm using a DC power pack type unit that is rated on the label at 12VDC, but I measured it at 18,4VDC. So, I'm waiting for the newer power supply to see if possibly the tiny bit of hum is being caused by the out of spec. salvaged one. Could be, but with my luck I doubt it.


adason 24th February 2013 12:31 PM

Velleman, Inc.

Mark2727 24th February 2013 12:43 PM

The Velleman kit appears to require a separate power supply.

Looks complicated.

No English on the build manual.

There's got be another way. I have been told that something like a CL-90 won't work. Current rush limiter.

Other digital amps I have don't have this issue and are very small physically. I'm wondering what they do? Must be something built into the chip.

Mark2727 24th February 2013 03:05 PM

I don't really understand...
I don't really understand how this works, but what about it:

2 Channel Stereo Speaker Protection Board LED Assembled | eBay

1) How does it wire up?
2) Could I run this off the same 24VDC power supply I'll be using for the Jerry's Amp?

The price is right, and it's already assembled.


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