Digitally-controlled stepped attenuator?

Spasticteapot · 12th March 2006, 07:01 PM

Hello, all!
I'm currently working on getting parts for a gainclone, and wanted to try getting a stepped attenuator for use for volume control, possibly in a preamp.
However, instead of using the standard-issue rotary switches, I'd like to try using a set of resistors and relays controlled by a microprocessor. (I'm also learning how to program these.) Using a remote, one could control which resistors were connected; by using a bunch of relays with SPST connections, they could be moved in and out of the circut. (When the relay's on, it would bypass the resistor).
Would this work? Also, could I use a set of relays for an input selector circut? I've got some PIC microcontroller gear, and it looks like might be easy (and fun!) to make a fancy-pants remote control system for a pittance. (10$ for the microcontroller, a few $ worth of transistors, and some relays harvested from old modems is all I'd need!)
Also, this might work rather nicely in conjunction with a built-in computer. I've got a small industrial computer board which would fit inside half of an old CD player enclosure quite nicely; with a gainclone on the other side and a DVD drive, I'd have a nifty little HTPC!

VEC7OR · 12th March 2006, 07:19 PM

To get your mind started:
http://www.mhennessy.f9.co.uk/preamp...e_research.htm
Constant impedance relay-resistor logarithmic attenuator
http://jos.vaneijndhoven.net/switchr/design.html

I'm also doing a similar project, you might wanna look here too My (semi-)reference preamplifier

myhrrhleine · 12th March 2006, 07:53 PM

You might consider a digital pot.
Many IC manufacturers make them.
As for relays, why not use a IC switch?
4016 and 4066 (I think) are the part numbers.
An article by Doug Self showed them to be rather low distortion when used in a shunt configuration.

Spasticteapot · 13th March 2006, 04:36 PM

Quote:

Originally posted by myhrrhleine
You might consider a digital pot.
Many IC manufacturers make them.
As for relays, why not use a IC switch?
4016 and 4066 (I think) are the part numbers.
An article by Doug Self showed them to be rather low distortion when used in a shunt configuration.

Interesting. I'd like to try two digital pots; can you point me to a simple circut? I'd like to do most of the stuff digtitally; that way, I can use a microcontroller and remote control on the cheap.
The chip switches also sound like an interesting idea.

myhrrhleine · 18th March 2006, 11:07 PM

Quote:

Originally posted by Spasticteapot

Interesting. I'd like to try two digital pots; can you point me to a simple circut? I'd like to do most of the stuff digtitally; that way, I can use a microcontroller and remote control on the cheap.
The chip switches also sound like an interesting idea.

http://www.analog.com/UploadedFiles/...58AD5290_0.pdf

DcibeL · 18th March 2006, 11:34 PM

There are several IC's like the PGA2311 which are basically a stepped attenuator in a chip. Easily controlled by a microcontroller.

12th March 2006, 07:01 PM	#1
Spasticteapot diyAudio Member Join Date: Jan 2006 Location: Wisconsin....what did you expect?	Digitally-controlled stepped attenuator? Hello, all! I'm currently working on getting parts for a gainclone, and wanted to try getting a stepped attenuator for use for volume control, possibly in a preamp. However, instead of using the standard-issue rotary switches, I'd like to try using a set of resistors and relays controlled by a microprocessor. (I'm also learning how to program these.) Using a remote, one could control which resistors were connected; by using a bunch of relays with SPST connections, they could be moved in and out of the circut. (When the relay's on, it would bypass the resistor). Would this work? Also, could I use a set of relays for an input selector circut? I've got some PIC microcontroller gear, and it looks like might be easy (and fun!) to make a fancy-pants remote control system for a pittance. (10$ for the microcontroller, a few $ worth of transistors, and some relays harvested from old modems is all I'd need!) Also, this might work rather nicely in conjunction with a built-in computer. I've got a small industrial computer board which would fit inside half of an old CD player enclosure quite nicely; with a gainclone on the other side and a DVD drive, I'd have a nifty little HTPC!

12th March 2006, 07:19 PM	#2
VEC7OR diyAudio Member Join Date: Jul 2003 Location: Vilnius	To get your mind started: http://www.mhennessy.f9.co.uk/preamp...e_research.htm Constant impedance relay-resistor logarithmic attenuator http://jos.vaneijndhoven.net/switchr/design.html I'm also doing a similar project, you might wanna look here too My (semi-)reference preamplifier __________________ Profanity took a very interesting form in Russia where there exists a language of sorts, most of its words based on four basic profane roots - nouns p...is, wh.0.e, c..t and verb f..k. It is possible to sensibly communicate using just these four basic roots.

18th March 2006, 11:34 PM	#6
DcibeL diyAudio Member Join Date: May 2003 Location: Saskatchewan	There are several IC's like the PGA2311 which are basically a stepped attenuator in a chip. Easily controlled by a microcontroller. __________________ The power of Science compels you!

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12th March 2006, 07:53 PM	#3
myhrrhleine diyAudio Member Join Date: Jan 2006 Location: Avalon Island	You might consider a digital pot. Many IC manufacturers make them. As for relays, why not use a IC switch? 4016 and 4066 (I think) are the part numbers. An article by Doug Self showed them to be rather low distortion when used in a shunt configuration.

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