Apologies for the late reply, 11 years, but I use that method in my amplifier. I still have a deliberate delay, otherwise momentary clipping (vinyl record tick at high volume) will immediately switch off the relay.
My amplifier does this:
Very short clipping: LED turns from green to yellow for about a second
Output signal all wrong for 100 ms or so, or regular clipping during a few seconds: relay off, LED turns red
@Mooly , that "all wrong for 100 ms or so" should be "all wrong for about 20 ms", see https://worldradiohistory.com/UK/Wireless-World/90s/Electronics-World-1996-02-S-OCR.pdf pages 140...143, particularly page 143.
To be honest, I haven't a clue if I chose a suitable relay back then. Besides, nowadays I would design the circuit such that there is a reverse voltage across the relay coil when it gets turned off, so the magnetic field falls of faster.
To be honest, I haven't a clue if I chose a suitable relay back then. Besides, nowadays I would design the circuit such that there is a reverse voltage across the relay coil when it gets turned off, so the magnetic field falls of faster.
In LM3886 based my Ref Rev a and it’s various version have a relay connecting the ground and not the speaker +
Thanks Marcel
And I'm still using that same amplifier with its FET relay replacements.
Indeed. Most of us were probably using unsuitable parts that hadn't a chance of reliably interrupting a high DC current into a large inductance.
Good to see this thread still pops up every now and then . I abandoned relays shortly after putting up the original post here after seeing a post from Michael Bean. I think a lot of people have done the same. Modern Trench mosfets offer very low Rds(on) at low single digit on 100-120 V parts that most relays cannot compete with. But the great thing is they can switch fault level currents ad infinitum which EMR’s cannot do without damage. The trick with mosfets is to switch them fast so the power dissipation during switching is minimized. The distortion is negligible as well - I’d say they are as near a perfect solution as is possible. The example below switches the speaker ground return - I prefer now to switch the spkr hot but anyway it gives some numbers and a few sims. This is basically what I used on the nx- Amp PSU and protection board.
https://hifisonix.com/wordpress/wp-content/uploads/2012/08/Speaker-Relay-V1.03.pdf
(Note: in the example above, if you accidentity short the speaker return to the chassis, the SSR is bypassed so that’s why I prefer not to use this approach anymore)
. I abandoned relays shortly after putting up the original post here after seeing a post from Michael Bean. I think a lot of people have done the same. Modern Trench mosfets offer very low Rds(on) at low single digit on 100-120 V parts that most relays cannot compete with. But the great thing is they can switch fault level currents ad infinitum which EMR’s cannot do without damage. The trick with mosfets is to switch them fast so the power dissipation during switching is minimized. The distortion is negligible as well - I’d say they are as near a perfect solution as is possible. The example below switches the speaker ground return - I prefer now to switch the spkr hot but anyway it gives some numbers and a few sims. This is basically what I used on the nx- Amp PSU and protection board.https://hifisonix.com/wordpress/wp-content/uploads/2012/08/Speaker-Relay-V1.03.pdf
(Note: in the example above, if you accidentity short the speaker return to the chassis, the SSR is bypassed so that’s why I prefer not to use this approach anymore)
A question for PMA, re your circuit posted in post #288 :
https://www.diyaudio.com/community/threads/output-relays.191449/post-2835407
Am I right in saying that the relay output needs to be loaded to Gnd with a low impedance load (i.e. not 10k or so) for it to function properly ?
Also the power supply needs to be a bit higher than the maximum signal amplitude.
So an auxiliary supply of +/-15V would not work if the amp is powered by say +/-50V rails.
Correct ?
Any ideas how to implement a star-up mute ?
Thanks,
Patrick
https://www.diyaudio.com/community/threads/output-relays.191449/post-2835407
Am I right in saying that the relay output needs to be loaded to Gnd with a low impedance load (i.e. not 10k or so) for it to function properly ?
Also the power supply needs to be a bit higher than the maximum signal amplitude.
So an auxiliary supply of +/-15V would not work if the amp is powered by say +/-50V rails.
Correct ?
Any ideas how to implement a star-up mute ?
Thanks,
Patrick