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Improving a delay audio relay circuit

Hi. Please take a look at this design:
http://tuukan.fliput.net/nonoise_en.html

It is a circuit used to eliminate some audio popping due to crappy amp
design in 90s pinball machines.

I am looking for those of you that know how to improve on this (either
eliminating 1 or more relays and using logic chip or other). Keep in
mind only that the power source is about 18vac to start.

Thanks for any valuable input you might have.
 
R

Ross Herbert

Jan 1, 1970
0
Hi. Please take a look at this design:
http://tuukan.fliput.net/nonoise_en.html

It is a circuit used to eliminate some audio popping due to crappy amp
design in 90s pinball machines.

I am looking for those of you that know how to improve on this (either
eliminating 1 or more relays and using logic chip or other). Keep in
mind only that the power source is about 18vac to start.

Thanks for any valuable input you might have.


It is a pretty basic circuit, but it works...

In more refined circuit designs K1 can be eliminated so that only one
relay is used. The circuit must be arranged such that the relay
operates on delay but releases instantaneously.

In all delayed-on or anti-pop circuits I have encountered, even in
high quality professional audio systems, the good old
electro-mechanical relay is still preferred as the speaker isolation
device. There is as yet no solid state device that I know of which
will duplicate the function as well as a relay.
 
J

John Woodgate

Jan 1, 1970
0
dated said:
Hi. Please take a look at this design:
http://tuukan.fliput.net/nonoise_en.html

It is a circuit used to eliminate some audio popping due to crappy amp
design in 90s pinball machines.

I am looking for those of you that know how to improve on this (either
eliminating 1 or more relays and using logic chip or other). Keep in
mind only that the power source is about 18vac to start.

Thanks for any valuable input you might have.
If asked to do that job today, I would still use relays. It IS possible
to do it solid-state, but it's not all that easy to switch
loudspeaker-level currents with negligible voltage drop, no noise and
low distortion. Metallic contacts do it easily.

A better solid-state solution would be to fix the power supply design
'feature' that causes the problem.
 
J

Jim Thompson

Jan 1, 1970
0
If asked to do that job today, I would still use relays. It IS possible
to do it solid-state, but it's not all that easy to switch
loudspeaker-level currents with negligible voltage drop, no noise and
low distortion. Metallic contacts do it easily.

Relays have always been my preference.
A better solid-state solution would be to fix the power supply design
'feature' that causes the problem.

With a single supply, there's no solid-state solution. Slow slewing
invites other issues with the local feed back loops.

Dual supplies are hard to power up perfectly balanced.

...Jim Thompson
 
J

John Woodgate

Jan 1, 1970
0
In message <[email protected]>, dated Thu, 24
Aug 2006 said:
Dual supplies are hard to power up perfectly balanced.

Not too bad for sufficiently relaxed values of 'balanced'. Phono
equalizers (remember them?) are notorious for creating thumps, because
of the high gain at low frequencies. In a rash of optimism, I designed
and prototyped a precision EQ (frequency response correct to less than 1
dB), and fed it from an AC wall-wart. In the box were +ve and -ve
half-wave rectifiers with big (1000 uF) filter caps compared with the
value indicated by the current drain followed by bootstrapped 78/79LO5
regulators. No thump. OK, the filter caps came from the same batch,
but....
 
J

Jim Thompson

Jan 1, 1970
0
In message <[email protected]>, dated Thu, 24


Not too bad for sufficiently relaxed values of 'balanced'. Phono
equalizers (remember them?) are notorious for creating thumps, because
of the high gain at low frequencies. In a rash of optimism, I designed
and prototyped a precision EQ (frequency response correct to less than 1
dB), and fed it from an AC wall-wart. In the box were +ve and -ve
half-wave rectifiers with big (1000 uF) filter caps compared with the
value indicated by the current drain followed by bootstrapped 78/79LO5
regulators. No thump. OK, the filter caps came from the same batch,
but....

The last time I hand-built a power amplifier (admittedly some 30 years
ago) I used a grotesque mechanically-delayed mercury-wetted-contact
relay that connected a resistor load on power-up and then switched to
the speaker two seconds later ;-)

...Jim Thompson
 
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