Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Construction Tips Construction techniques and tips

Muting switches for no clickiness
Muting switches for no clickiness
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 11th September 2020, 04:47 PM   #1
AshtrayWasp is offline AshtrayWasp
diyAudio Member
AshtrayWasp's Avatar
Join Date: Apr 2020
Default Muting switches for no clickiness


I am designing a 32 band band-pass filter bank (eurorack standards) which consists of a tube Class A 2 stage mono preamp sent in parallel to the 32 bands and summed by two (stereo) active busses (VCA controlled). In each band there is a VCA controlling the volume that has an aux output connected to the input for feedback controlled through a pot and a switch for on/off, there is also a switch to bypass the filter connection to work as a summing stereo mixer. Another switch is found in the master controls to bypass the preamp sending the signal to the bands and instead be sent on a separate external output to let it be used as a separate pre.

I have been reading on ways of using different types of switches for less clickiness or pops when engaged, but a transistor or a relay seem to have too many drawbacks (distortion, noisy) so I though of using something like maybe a quick envelope to mute the VCAs when the switches are used but I have no idea if there might be a better way to also minimize part count.

The VCAs I'm using are the THAT2180 with a logarithmic amplifier to bend (slightly concave) the CV according to the power law (still trying to establish that one ).

I would appreciate any feedback as I'm fairly new to circuit design, thank you.
  Reply With Quote
Old 11th September 2020, 06:37 PM   #2
Enzo is offline Enzo  United States
diyAudio Member
Join Date: Sep 2004
Location: Lansing, Michigan
The main source of pops when switching in the signal path is sudden voltage shifts. If you have a cap coming from some point in the circuit, and it just goes to a switch point. That cap is uncharged. When the switch is closed to some other point, that cap has to instantly charge to whatever voltage differential existed between the two points. Even if it is just a millivolt, it still results in a pop.

What we generally do is span the switch with a high value resistance. Say 1 meg or 470k maybe. The resistor keeps the cap charged, but doesn't allow signal leakage. Of course different circuits require difering interpretations of this basic approach.
  Reply With Quote
Old 12th September 2020, 03:16 PM   #3
AshtrayWasp is offline AshtrayWasp
diyAudio Member
AshtrayWasp's Avatar
Join Date: Apr 2020
By span do you mean shunted after the cap? Ive found this circuit that I think uses what you are saying

Click the image to open in full size.

So instead of using it as a bypass, the pole is coming from the preamp output buffer for instance and the dual throws one to the aux output and another to the bands, with the cap and resistor at the output of the preamp buffer? The pole would then be going to a jack for the aux or the input buffer on each band.

Last edited by AshtrayWasp; 12th September 2020 at 03:21 PM. Reason: Missclicked post while typing
  Reply With Quote
Old 14th September 2020, 09:38 PM   #4
mickeymoose is offline mickeymoose  Canada
diyAudio Member
Join Date: Nov 2008
- Add a bleed resistor to the wire connecting the NC (bypass) contacts.
- Assure that DC is not introduced at the input and output by the attached equipment. E
  Reply With Quote
Old 19th September 2020, 11:18 AM   #5
Mark Tillotson is offline Mark Tillotson
diyAudio Member
Join Date: May 2018
Location: Cambridge UK
The only way to avoid a click when switching active signals is to cross-fade, simply removing any DC component isn't enough when the signal is present. Something like a JFET with the control signal transitioning over several milliseconds can provide a smooth transition between open and closed circuit.

Imagine a bass note - if hard-switched at the peak of the waveform you introduce a step at full amplitude, which has energy across the entire audio spectrum and will be audible as a distinct click.

Switching slowly provides a smooth waveform at the transition - far less energy sprayed across the audio spectrum.

If you switch always at a zero-crossing the click is vastly reduced, but this is complicated when switching between two signals as you have to time the switch point with the two signals being instantaneouly equal using a comparator/flip-flop circuit.

Probably the JFET way is the simplest, and there may be some chips that do the zero crossing trick specifically designed for pro audio equipment. Distortion _during_ the switching isn't a big problem, you just have to not click or clip.

In the digital domain its easy, a smooth band-limited crossfade is a few lines of code
  Reply to this post


Muting switches for no clickinessHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Top quality main switches for audio-hifi comp (Rotary and Pushbutton Power Switches) tiefbassuebertr Parts 19 25th November 2017 06:18 PM
random muting rrae Car Audio 15 14th August 2013 07:37 AM
Amp Muting richie00boy Solid State 6 21st August 2009 10:57 PM
A simple way to create dual(or more!) rotary switches out of single rotary switches stappvargen Pass Labs 14 16th April 2004 11:33 PM

New To Site? Need Help?

All times are GMT. The time now is 06:18 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
Copyright ©1999-2020 diyAudio