Hi. I have a DAC that, when it locks on a SPdif signal, produces a huge pop on the outputs. It does have a LED to show that it has locked on a signal. I was thinking that there must be a way to use a delay to operate a small signal relay on the outputs , but I really have no experience at doing this. I imagine a RC time constant can be used to make a 2 second delay. Can anyone help with this project?
Thanks!
Thanks!
You need to be more clear. Do you mean the lock LED illuminates then 2-seconds later there is a pop? Do you mean there is a pop at the exact same time when the LED illuminates and you need to silence the pop for 2-seconds? What voltage to ground is on the LED when it illuminates? What voltage to ground is on the LED when it is off? What is the dac type? Do you have a high resolution pic of it? Do you have a voltmeter? An oscilloscope? What would you want the relay to do, short the analog outputs to ground? Open the analog outputs? What kind of output stage does the dac have? Etc.
First post the schematic. The DAC may already have an output muting relay circuit, so there could be a bad part, or bad design.
If the latter, it might be possible to add circuitry to mute the lock noise.
If the latter, it might be possible to add circuitry to mute the lock noise.
thanks For allowing me to clarify. This is a Theta Pro prime II. No output relay. The pop happens when it locks onto a SPdif signal, and sometimes it just silently locks on, and other times, comes on with a blast. There is a front panel LED which shows when there is a “lock”. The pop happens at the same time the switch is engaged (I am using the RCA/Toslink switch to interrupt the SPdif signal on the RCA). But, when it puts out a burst of noise, it is impressively loud! So, I was thinking, if I add a relay to the outputs and use the “Lock”signal that lights the LED, what kind of simple circuit do I need to switch on the outputs and use relay after a delay of a second or two, so the noise burst has passed before the relay is engaged. I hope this makes sense.
The relay would have to be switched twice. Once to engage it and then later to disengage it. Also, it takes a relay time to close and time to open. The times can be some milliseconds before the relay state is changed. So how is it determined to switch the relay on, and how is it determined to switch the relay off? How much time before the pop does the relay have change states?
Also, how would the LED lock signal be used. As a voltage across the LED? Using a light sensor?
Also, how would the LED lock signal be used. As a voltage across the LED? Using a light sensor?
I was thinking of using some DPDT Aromat relays, using N.O. And apply 12V (or 6V) to engage the outputs. I want to engage the relay a second or two after the signal locks, which is when the LED lights. Is there a way to use the triggering of the LED, thru a delay to apply 12V to the relays?
You could use a simple LDR glued to the SPDIF Lock LED and
use a circuit like this one to trigger a relay -
https://www.circuitstune.com/2012/06/dark-detectorsensor-circuit-using-ldr.html
Instead of the LED , use a relay and you should be good.
There are other "automatic night light" or light sensor circuits using an LDR and a 555 and those
should work too. The advantage is - you don't tamper anything inside the DAC.
https://elonics.org/light-sensor-circuit-using-ldr-555-timer-adjustable/
use a circuit like this one to trigger a relay -
https://www.circuitstune.com/2012/06/dark-detectorsensor-circuit-using-ldr.html
Instead of the LED , use a relay and you should be good.
There are other "automatic night light" or light sensor circuits using an LDR and a 555 and those
should work too. The advantage is - you don't tamper anything inside the DAC.
https://elonics.org/light-sensor-circuit-using-ldr-555-timer-adjustable/
Theta Pro prime II does not have a muting relay. You could combine it with power on/off muting with one and the same relay shorting outputs to GND. Check if there are current limiting/stop resistors in the outputs, they usually are there.
Or you stop using the RCA/Toslink switch to interrupt the SPDIF signal on the RCA.
Or you stop using the RCA/Toslink switch to interrupt the SPDIF signal on the RCA.
Do you mean you want the relay to go when on when the LED goes on then go off 2 seconds later? You have to be specific about the timing and what happens at what exact time.
We still don't know when the pop occurs relative to the LED on/off timing. We don't know if you mean you want the relay to activate before you push the SPDIF switch button? Then turn off 2 seconds after the LOCK LED lights up?
We don't know if it takes the relay 50ms to operate once power is applied to its coil, if that is going to be too long after the LED lights up and or after you push the SPDIF switch button. Or does the pop happen 25ms after you push the button or the LED lights up?
You still have to be more clear about exactly what triggers each change of state of the relay, not just one delay. There has to be at least one other event besides a delay the gets the relay ready to perform a delay. And you have to give the relay enough time to change states.
Otherwise you might need to use a muting transistor instead of a relay because a transistor switch can act much faster.
We still don't know when the pop occurs relative to the LED on/off timing. We don't know if you mean you want the relay to activate before you push the SPDIF switch button? Then turn off 2 seconds after the LOCK LED lights up?
We don't know if it takes the relay 50ms to operate once power is applied to its coil, if that is going to be too long after the LED lights up and or after you push the SPDIF switch button. Or does the pop happen 25ms after you push the button or the LED lights up?
You still have to be more clear about exactly what triggers each change of state of the relay, not just one delay. There has to be at least one other event besides a delay the gets the relay ready to perform a delay. And you have to give the relay enough time to change states.
Otherwise you might need to use a muting transistor instead of a relay because a transistor switch can act much faster.
I would like the relay to engage about 2 seconds or so after the led “lock” light turns on. That would easily allow enough time to have the burst drop out. The noise burst is loud, but brief. So, if i somehow tie the led “on’ voltage (around 2.7V) thru a time delay and engage the relay, that should work.
So, the burst starts maybe 1 second after the LED lights up, and ends no more than 2 seconds after the LED lights up? Is that correct? Or maybe the burst starts 0.5 seconds after the LED lights up? Or the burst starts at the exact instant the LED lights up? Or it varies when the burst starts and ends but latest it ends is at 2 seconds after LED lights up. And soonest it starts is .025 seconds after the LED lights up? Or what?
IOW, in case its still not clear, we need a time window to mute. A time window has a start time and end end time. So far you keep repeating the ending time (which is 2 seconds after the LED lights up). We still are not clear on how much time we have to act to start the time window. Do we start the mute window before you push the button, after you push the button before before the LED lights up, exactly when the LED lights up, or when?
IOW, in case its still not clear, we need a time window to mute. A time window has a start time and end end time. So far you keep repeating the ending time (which is 2 seconds after the LED lights up). We still are not clear on how much time we have to act to start the time window. Do we start the mute window before you push the button, after you push the button before before the LED lights up, exactly when the LED lights up, or when?
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The burst, when it happens seems to be very close in time to the LED lighting up. Quick, high output noise burst, and then the expected signal. I am thinking 2 seconds just as a precautionary delay. One second would probably do.
Close to when the LED lights up. Does it ever happen exactly when the LED lights up, a fraction of a second before the LED lights up, or only a fair fraction of a second after the LED lights up. This is crucial. If we don't mute soon enough then some of the burst may still come through. Also, it we mute too long then some of the music may be cut off (although that would be a different annoyance).
So, we need to have a pretty close idea of the very earliest to burst ever starts to occur. If it can happen at the very same instant the LED lights up, then we may be too late. Maybe in that case we should start the mute when you push the SPDIF button, and end the mute 1.5 seconds after the LED comes on?
Its like if we don't do it right then we may end up with a crappy design. So we need to be pretty sure about what we need to do.
Otherwise, maybe you can get lucky and trial and error will work the first time?
So, we need to have a pretty close idea of the very earliest to burst ever starts to occur. If it can happen at the very same instant the LED lights up, then we may be too late. Maybe in that case we should start the mute when you push the SPDIF button, and end the mute 1.5 seconds after the LED comes on?
Its like if we don't do it right then we may end up with a crappy design. So we need to be pretty sure about what we need to do.
Otherwise, maybe you can get lucky and trial and error will work the first time?
This might be the owner's manual. Or it might not, I am not sure.
It appears that there is a three position toggle switch on the front panel, which lets you tell the box which of the three input signals to select, apply digital signal processing to, and then present on the output. It is likely that the toggle switch provides control signals (Enable_A , Enable_B , Enable_C ???) that operate an electronic selector switch of some kind. Perhaps relays, perhaps analog multiplexers, or most probably, a digital multiplexer.
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It appears that there is a three position toggle switch on the front panel, which lets you tell the box which of the three input signals to select, apply digital signal processing to, and then present on the output. It is likely that the toggle switch provides control signals (Enable_A , Enable_B , Enable_C ???) that operate an electronic selector switch of some kind. Perhaps relays, perhaps analog multiplexers, or most probably, a digital multiplexer.
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