Replacing pot with digital volume control

[puterfixer]

Hi everyone,

I have a set of satellite speakers and subwoofer made by Cambridge SoundWorks. The subwoofer has an amplifier built-in, and connects with a cable to any stereo headphone jack or RCA line out jacks (through an adapter). The cable has a simple inline potentiometer to adjust volume, like an attenuator.

I would like to replace that potentiometer with an unit with digital control of the volume, Mute and Power on/off setting, which should be operated via an infrared remote control. The idea is to connect the speaker set through this unit to any audio source (like VCR, or satellite receiver, which don't have built-in volume control) and be able to adjust the volume from anywhere in the room. If possible, it would be great for the unit to retain volume level while powered off.

If anyone could help me build such an equipment, I'd really appreciate it. I'm not an electronic graduate, so take it easy with me... any information will help: web pages, schematics, suggestions for circuits, anything. I live in Eastern Europe, can mail order most circuits and equivalents from a nearby components distributor. Thank you kindly for your time,

Best regards,
Mr. Titel

[FrankDIY]

Hello,

I am sorry but I don't know any kit who peform your task, but one thing: if you install digital component in your amplifier (like digital potentiometer), you need a separate power supplie to be sure that you don't introduce noise in your signal path and amplifier power supplie.

[Geoff]

Analogue Devices have several ics that will provide what you want. If I remember rightly, there are a couple of Application Notes on their site that will give you guidance.
Dallas Semiconductors also make some digital potentiometer ics.

[Alex M]

I'm using the Dallas Semiconductors DS1802 in my preamp
(see http://www.soton.ac.uk/~apm3/diyaudio/Preamp.html),
though I'm afraid I can't comment on its sound as I'm
still working on the control circuitry and haven't
connected the preamp to my system yet.

Dallas have a datasheet for DS1802 at
http://www.dalsemi.com/datasheets/pdfs/1802.pdf .

By the way, you don't need a separate power supply for this
chip, since it doesn't have a high frequency clock. I used
a low-power LM317 regulator to get a +5V line for the
DS1802 from the +15V preamp supply. What I did do, though,
was to use optoisolators to separate the ground lines of
the audio circuits from the digital circuits.

Alex

[jbateman]

This guy used to sell a neat kit that would decode the IR burst from any remote control, then gives you seven output pins for controlling a device. You could easily use his circuit to operate a motor driven potentiometer. I have.
I think he now just sells the PIC controller with instructions for the rest of the circuit. Go to weedtech.com and look for the "infrared receiver kit" under the "hobbyist " section

http://www.weedtech.com/index1.html[/url]

[puterfixer]

Great ideas, everyone, thanks for your replies!

I was using the wrong keywords in web search engines, so as soon as I entered <b>+digital +potentiometer +volume +control</b> in <a href="http://www.google.com" target="_blank">Google.com</a> the useful links started to pop on screen. There were a number of IC manufacturers with good chips for digital volume control, some with up/down buttons and others with 3-line serial input which is great for interfacing with an infrared receiver and decoder.

For those interested in similar applications, check out these manufacturers' web sites:<ul>
<li><a href="http://www.dalsemi.com" target="_blank">Dallas Semiconductors</a> - check series <b>DS18xx</b> and <b>DS16xx</b>
<li><a href="http://www.analog.com" target="_blank">Analog Devices</a> - check series <b>AD52xx</b> and <b>AD84xx</b>
<li><a href="http://www.crystal.com" target="_blank">Crystal<a> - <b>CS3310</b> appears in a number of articles online.
</ul>

Now, all I got to do is see if my local components distributor carries these chips or compatibles, and see where to go from there. I still need to find an IR decoder chip, one of the pages posted above has a kit with an IR decoder with learn function, which is pretty cool - if I could find out what that IC is. Again, thanks everyone for your time, much appreciated!

[Edited by puterfixer on 04-24-2001 at 12:09 PM]

[mlloyd1]

There is also the Analog Devices AD7110, AD7111, AD7112, AD7112A, AD7115 and AD7118. These were made for audio use, although I'm not sure which of these are still in production.

There was a slick idea in one of the Analog Devices Application guides for a precision attenuator (0 to 80 dB range) with 0.1dB steps. Make a great volume control....

Michael

[jbateman]

" I still need to find an IR decoder chip, one of the pages posted above has a kit with an IR decoder with learn function, which is pretty cool - if I could find out what that IC is."

jbateman replies...
The part that weedtech still sells is actually a PIC microcontroller, with his own code burned in it. Poke around his site and you can find part number PIC-RCR, microcontroller w/ documentation...$16. Unless you're really talented I don't think you can do this part yourself.

Good luck!

[jaaasgoed]

Hi,

Conrad sells ab pcb with the circuit you need. It comes with all the parts you need except for the resistor chip, but they also sell it separately, so you can order the entire thing from them. It is a mono kit so you have to order two for stereo use. It uses two buttens for up/down but it says in the catalog that you can use Ir as well.

You can find there site at http://www.conrad.com

Roel

[knuckles_mctug]

If you want a simple IR receiver use an IR reciver with built in decoder (demodulator) you can then use any type of PIC or similar and a remote control you presently own to control the digi-pot.
I've already used one so let me know if you need a few pointers. In many ways its better than just buying an IR module because you can configure the amount of buttons you need.
Hope this helps.
Knuckles