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Any ideas to solve turn-off transients with my M3?

post #1 of 23
11/18/09 at 6:15pm
Thread Starter 
So I recently completed my M3 build. I have the e12 muting circuit and that nicely solved the minor turn-on transients, however it does not seem to solve the turn-off transients.

I am using the e24 power switch circuit with a SPST relay (Omron G8P-1A2T-F-DC12), I suppose I could replace that DPST relay and use the other pole to switch the e12 power. Only one I could find that seem suitable was T92S7D22-12 Tyco Electronics / P&B General Purpose / Industrial Relays

Wondering if it would be better to just add another smaller SPST relay for the e12 circuit. Course would have to make sure the coil current does not exceed that of the e24.

Anyone have ideas beyond adding a relay that could solve the turn-off transients? Or should I just ignore the small turn-off noise?
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post #2 of 23
11/18/09 at 6:29pm
What opamps are you using? The OPA6x7 and AD8610s should exhibit very little turn on/off transients.

I would suggest changing to a double-pole relay for your ε24, and use the second pole to cut power to the ε12 immediately upon power-off. You'll find a lot more DPDT relay choices than DPST.
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post #3 of 23
11/18/09 at 6:34pm
Thread Starter 
Quote:
Originally Posted by amb View Post
What opamps are you using? The OPA6x7 and AD8610s should exhibit very little turn on/off transients.

I would suggest changing to a double-pole relay for your ε24, and use the second pole to cut power to the ε12 immediately upon power-off. You'll find a lot more DPDT relay choices than DPST.
Using OPA627AP

I will check DPDT ones.
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post #4 of 23
11/18/09 at 6:38pm
Thread Starter 
Opps typo OPA627AP

It is not a loud transient, but is a little short bit of a crackle.
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post #5 of 23
11/18/09 at 6:53pm
What's your DC offset?
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post #6 of 23
11/18/09 at 7:25pm
Thread Starter 
0.7 mV
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post #7 of 23
11/18/09 at 7:32pm
Between IG-OG?
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post #8 of 23
11/18/09 at 7:36pm
Thread Starter 
Quote:
Originally Posted by FallenAngel View Post
Between IG-OG?
That was for ol-og
I forget my il-og measurement but it was less than 1mV
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post #9 of 23
11/18/09 at 8:04pm
Then there really shouldn't be much of a turn off transient (I have an M3 on my desk for the next couple of days and haven't noticed almost any).
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post #10 of 23
11/18/09 at 10:47pm
Thread Starter 
Quote:
Originally Posted by m1abrams View Post
That was for ol-og
I forget my il-og measurement but it was less than 1mV
Just measured my ol-ig DC offset and it was 0.2mV

So I think my DC offset numbers are good. Wonder why i get the turn-on and off noise? Note I do get the turn-on just the e12 mutes it.

After so more experimenting I noticed that the turn-off noise only happens when I have the bass boost turned on with it off no noise. I never measured the DC offset with the bass boost on.

Bass boost off: il-ol 0.2mV ol-or 0.7mV
Bass boost on: il-ol 0.2mV ol-or 4.1mV
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post #11 of 23
11/18/09 at 11:28pm
It sounds like the rail caps, etc. are holding the e12 from turning off fast enough when you power down, so I think that amb is correct in his recommendation (usually is ).
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post #12 of 23
11/18/09 at 11:32pm
Thread Starter 
Quote:
Originally Posted by Pars View Post
It sounds like the rail caps, etc. are holding the e12 from turning off fast enough when you power down, so I think that amb is correct in his recommendation (usually is ).

Which is probably it. Forgot to mention I noticed the M3 board LED stays light for sometime after power off. In fact even after 10mins it still has a tiny bit of glow!
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post #13 of 23
11/19/09 at 1:55am
When bass boost is enabled, the low frequency gain of the amp is increased (all the way down to 0Hz -- DC), therefore if there is a small amount of turn on/off transient, it would be amplified more.
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post #14 of 23
11/19/09 at 1:02pm
Thread Starter 
Thinking of using this relay.
Digi-Key - PB329-ND (Manufacturer - K10P-11DT5-12)

It is pretty close in physical size to the one I am currently using:
G8P-1A2T-F-DC12 Omron Electronics General Purpose / Industrial Relays

This will make switching it out in the case easier since I would not require as much re-work.

It has less contact current capability but it is still WAY more than I the Sigma11 should be using, heck the IEC is fused at 1A so I would hope 15A contact rating would be high enough for the relay.

Any reason I should not use this relay that I am missing?

Thanks for the assistance.
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post #15 of 23
11/19/09 at 3:08pm
How loud is the thump at normal volumes if you leave your headphones on? Unless it is painfully loud, I don't see a reason to worry about it at all.
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