[Pars]

I may put a muting relay in the Gilmore I almost have done, but had a question regarding how to supply the power to it. I had thought about using a 7812 and just tapping into the +16V power (probably off one of the PSU caps) and using this. Any detrimental effects to doing this, or will I need to put a sep. PS in here just for this? I will probably just short the outputs to ground, on a short 555 timer circuit (2 secs) for powerup delay, relay grounding the outputs in its NC position, would need to be held open while listening, which may not be a good thing?

I have also read about latching relays, but haven't really seen any circuits that use them. In order to close the relay (short the outputs) after the amp has come up (i.e., at shutdown), I would have to also close the relay with some logic? Another concern would be power failure? Any thoughts, pointers, URLs?

I am thinking I may use this as my preamp, and since my poweramp is left on all the time, muting is a must.

Thanks,

Chris

 

[Garbz]

ahhh something i've worked with a lot.

One of my gilmore amps had a relay shorting to ground connected directly to the +16.4v psu rail through a resistor. The several microsecond delay was more then enough to prevent any and all poweron clicks. At poweroff the relay released 1 second after the amp was shut down and about 2 seconds before the poweroff thump (the dangerous one) happens.

The only problem as you said is the signal travels past a magnetic coil which is on. I was paranoid about this. Then hours of A/B testing showed absolutly no difference between using a $1 relay in this way and using the headphones connected directly to the output. and i mean NO difference, not measurable, not audible.

My new amp has a separate psu controlling the relay and that works quite well. It also doesn't short the output to gnd, even worse it physically breaks the connection. The result NO difference in sound. In this case i used a $6 sivler contact relay but still the point is the same. There was no difference between relay and no relay, and i'd rather spend the $6 to get rid of the 750mv offset i get when i turn my amp off.

 

[Pars]

Thanks Garbz. Yeah, I knew that you had messed around with this. Do you happen to have a schematic of how you did yours (2nd one)?

When you have the relay in series with the output, you don't hear any clicks or pops when the relay turns on/off?

One other route I may investigate is in going thru the OPA548 datasheet, I noticed the E/S pin, specifically that pulling this low disables the output... i.e., shutting the PSU output down. I would probably do this in combination with shorting the output.

Chris

 

[gsferrari]

Interesting stuff guys. Any schematics? Parts list?

Super