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Old 23rd September 2008, 07:21 AM   #11
Mooly is online now Mooly  United Kingdom
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Hello Ted,
Does your preamp make any noises on switch off as well.
It's a very basic circuit is this. How about adding a diode to the IC supply and cap to suit, such that the supply to the 555 collapses immediately on switch off.
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Old 23rd September 2008, 07:25 AM   #12
Mooly is online now Mooly  United Kingdom
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Doesn't quite read what I mean I mean have the supply to the 555 via diode from the AC of the tranny, maybe using CMOS timer and simple R+C+ zener.
Delays should be foolproof in that it cannot be confused by a mains interupt etc. You want it to mute instantly and go through it's full "start sequence" everytime
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Old 23rd September 2008, 08:32 AM   #13
Nuuk is offline Nuuk  United Kingdom
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Quote:
Originally posted by Ted205
i read it that the relay shorts the buffer output to ground for a short period while the power is applied to it. I was planning to switch the power amp section on after the buffer has settled.
That's right, so no nasty offsets go through your amp, hence no nasty noise.

You could switch both the power rails but just supposing one contact of the relay sticks and you turn off just one rail?
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Old 23rd September 2008, 09:46 AM   #14
Ted205 is offline Ted205  United Kingdom
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That would be the same thing as a fuse blowing only on one rail.

I am coming round to putting it at the buffer output as it makes life easier, and whether it makes and audible difference ...........

i like the idea mooly as on power down the transformer will be the quickest to degrate, before the caps degrate and make a small pop on the speakers the relay will have latched (maybe?) and block any signal.
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Old 23rd September 2008, 11:01 AM   #15
Nuuk is offline Nuuk  United Kingdom
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I find that circuit acts fast enough to stop turn-off clicks anyway!
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Old 24th September 2008, 01:38 PM   #16
AndrewT is online now AndrewT  Scotland
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fit the mute to the pre-amp output. Use a relay to ground as Nuuk and the others have already told you.
Arrange for delayed on and instant off.

If you want you can also add a mute the the power amp input, again with delayed on and instant off.

Finally, you can fit another relay to the speaker output of the power amp. This is the only one that has signal through the contacts while operating.
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Old 24th September 2008, 05:44 PM   #17
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As a matter of interest would this circuit suit the Uno active pre from DD?

http://myweb.tiscali.co.uk/nuukspot/...clonepre2.html

I see it's been tested with the buffer circuits but there's no mention of the Uno. I thought it better to ask than to have to stamp the flames out.

John
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