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

Solid State Talk all about solid state amplification.

Multiway volume control proposal
Multiway volume control proposal
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 22nd July 2010, 03:34 PM   #1
davelowe is offline davelowe
diyAudio Member
Join Date: Mar 2010
Default Multiway volume control proposal

Hi - my first post - please be gentle,

I've been lurking reading your posts about the gainclone amps and will shortly be building an active four way system with crossovers for a stereo woofer and tweeter set up.

I've searched for relevant posts about VCA volume control. The opto-coupled system was interesting too.

Attached is an image of what I hope could be an outline way of controlling the volume of any number of channels simultaneously.

There is a thread using the 2180 series VCA on a compressor unit - essentially I think I have gone for a boiled down version of that. Please read the diagram with reference to


All comments gratefully received.

Thanks for reading.

Click the image to open in full size.
  Reply With Quote
Old 22nd July 2010, 10:45 PM   #2
Bigun is offline Bigun  Canada
diyAudio Member
Bigun's Avatar
Join Date: Jan 2009
Location: Waterloo, ON or Herefordshire UK
Multiway volume control proposal
Hi Davelowe, welcome on board.

It looks an interesting option. I took a peak at the datasheet for that part and the specs look quite good indeed. They even show the harmonic distortion (FFT) instead of the nearly useless THD spec.

Some people around here are allergic to op-amps though :-)

Anyhow, if it's not a big expense against the budget you've allocated for this project you might like to build it and listen for yourself - it's advice you'll hear a lot and it's good advice.

For those allergic to op-amps you could consider using JFETs as volume control elements. They can have higher distortion but some people like their simplicity. I've no idea which approach is best. Using a FET as a Voltage Controlled Resistor
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.

Last edited by Bigun; 22nd July 2010 at 11:08 PM.
  Reply With Quote
Old 22nd November 2010, 07:49 AM   #3
SirNickity is offline SirNickity  United States
diyAudio Member
Join Date: Oct 2009
Location: Anchorage, AK
I'm hoping to revive this thread because I'm interested in doing pretty much the same thing. (I'm actually planning to build a 4.1 chip-amp for my office / computer room.)

After looking at the schematic, I'm tempted to say it's missing a buffering op-amp on the control signal. THAT's tech note seems to suggest this is almost necessary (page 9 -- "the 2180 Series VCAs are designed to be operated with zero source impedance at pins 2 and 3") but warns against how many op-amps have considerable inductance at high frequencies. In this case, we're using an op-amp as a DC amplifier, so I don't think it's an issue, but their fix seems simple (series R + C.)

Now, I'm a complete newb to circuit design. I'm just at the "try to build something I found online" stage -- but I'm trying to understand. Can someone elaborate on how to create the control voltage? I'm stuck at the "?K" part. :-)

I'm guessing Ohm's law has something to do with this.. but op-amp inputs are supposed to be ideally infinite impedance. So. I'm struggling with how to design an appropriate circuit for this. I assume it would look something like this?

Click the image to open in full size.

Hopefully I'm in the ballpark here. Here's the idea so far:

R1 - Drop the regulated 5V to something below 1V when combined with the resistance of RV1 (0 to whatever RV1 is).
R2 - To avoid shorting the VR's output to ground (maybe not necessary due to R1 ... or does this leg of the pot even need to be connected at all?)
R3 and R4 - Gain setting for the op-amp... maybe a better choice to use this to scale the voltage down rather than wasting it via R1.

Thoughts? Am I even close?
  Reply With Quote


Multiway volume control proposalHide 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
Volume control on DVD player remote. Lose resolution at low volume? Circlotron Digital Source 2 10th June 2011 07:20 PM
i need preamp schematics w/o tone control or volume control hernanstafe Parts 7 30th January 2008 03:12 AM
The remote control paratactic volume control audio-gd Solid State 33 7th June 2007 11:16 PM
remote control motorised control for volume pot/knob CharlesY Parts 0 25th July 2005 11:12 AM
volume control sss Solid State 32 5th October 2003 11:13 PM

New To Site? Need Help?

All times are GMT. The time now is 07:53 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio