Clicking Noise in Analog Multiplexers
Clicking Noise in Analog Multiplexers
(OP)
Hi guys/gals,
I'm making a signal router for musicians. I'm using analog multiplexers (MAX307/MAX308) instead of relays. I'm getting clicking noises when I switch between different routing schemes. Does anyone have any suggestions as to how I could reduce these.
Thanks,
Steve
I'm making a signal router for musicians. I'm using analog multiplexers (MAX307/MAX308) instead of relays. I'm getting clicking noises when I switch between different routing schemes. Does anyone have any suggestions as to how I could reduce these.
Thanks,
Steve





RE: Clicking Noise in Analog Multiplexers
If this router has amplification, one way is to turn down the output amplification just before switching and then turning it back up after. This can happen very quickly!
RE: Clicking Noise in Analog Multiplexers
1) Slow down the control signal speed (RC filter) to minimize capacitive feed through spikes.
2)Most audio relays/switches are form D (make before break). See if a slight overlap (1- 10 ms?) for signal on/off helps.
RE: Clicking Noise in Analog Multiplexers
RE: Clicking Noise in Analog Multiplexers
Yes, now I am going to be putting op amp buffers before and after each of the switches. That should clean things up a bit.
S.
RE: Clicking Noise in Analog Multiplexers
I don't think that slowing up the switch signal will work on this device. It looks to be driven by logic gates which will switch when the threshold voltage is reached. You might try using a single fet for each switch and ramping the control signal as stated above. If using a low res on fet you can put the fet across the buffer amp such that turning it on reduces the gain of that circuit to very close to zero. gain = Rfet/Rin
-elf
RE: Clicking Noise in Analog Multiplexers
2sb18; I can not see how op amp buffers will help in the least...
RE: Clicking Noise in Analog Multiplexers
THD = Rflat(ON) / Rload
Since an op amp buffer would increase the Rload, wouldn't this reduce THD?
I am going to take itsmoked other advice about decreasing gain to zero while making the transition and then bringing it back up. Right now the signal chain is:
Input buffer -> Multiplexer -> Buffer -> Attenuator -> Output buffer
Are there too many buffers?
Thanks for all your help guys,
Steve.
RE: Clicking Noise in Analog Multiplexers
If you are now saying that you want you actually want is to switch muxes whilst these are carrying signals, then with basic muxes you will still risk getting clicks and thumps due to sudden connection/disconnection part way through the signal waveforms.
To avoid this situation you require programmable attenuators (either digital or analog)to avoid sudden "chopping" of the signal waveform. A relatively fast envelope shape over a few tens of milliseconds should produce a clean signal changeover (off to on, or on to off) without audible "artefacts".
NOTE: You may be able to dispense with the separate muxes by summing the individual attenuator outputs together into a single amplifier input.
RE: Clicking Noise in Analog Multiplexers
Could the click problem simply be that in audio applications Form D switch contacts (make before break) are used to avoid the "click" or "pop" and for solid state switching the control circuits must electronically provide the overlap.
RE: Clicking Noise in Analog Multiplexers