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-   -   Replacing broken volume control with digital volume control (http://www.diyaudio.com/forums/solid-state/178905-replacing-broken-volume-control-digital-volume-control.html)

Gunawan W 11th December 2010 07:24 AM

Replacing broken volume control with digital volume control
 
Hi all,
I have multichannel solid state amplifier, but the right channel volume control (potentiometer) was broken.

I can not find the part for replacement, so I want to replace it with digital volume control.

My plan is using the left channel potentiometer as a control for new digital stereo volume control.

Please help me, I need circuit diagram for this,

thankyou in advance.

Mooly 11th December 2010 07:35 AM

Using a pot to control a digital attenuator is far from easy, I don't know how you would do it without purpose writen code to interface it to a "one off" purpose built attenuator...

You could use it to control an analogue VCA (voltage controlled amplifier) though, but surely fitting a conventional replacement pot is far far easier.
Digital control usually requires either a rotary encoder for control or up/down buttons. All the original pot can do is generate a variable resistance (or voltage) and nothing more. What happens if the good side of the pot goes faulty?

Is the original motorised ? Photos ? Make model etc ?

banana 11th December 2010 05:03 PM

I agree with Mooly, it will be difficult to use a volume pot to control digital attenuator. I have made it by feeding the pot with 5Vdc, and then encode the pot voltage by an ADC. The whole thing is quite clumsy. See link below.

http://www.diyaudio.com/forums/chip-...ontrl-vol.html

Gunawan W 12th December 2010 05:11 AM

Thank's Guys,
I searched the net, and I find more simple solution using optocoupler like this:
DIY "Lightspeed Attenuator" - Passive LDR Volume Control (audio optocouplers)

what do you think?

Mooly 12th December 2010 06:07 AM

Quote:

Originally Posted by Gunawan W (Post 2395439)
Thank's Guys,
I searched the net, and I find more simple solution using optocoupler like this:
DIY "Lightspeed Attenuator" - Passive LDR Volume Control (audio optocouplers)

what do you think?

It needs a dual pot... and yours is broken :)

h_a 12th December 2010 07:38 AM

Quote:

All the original pot can do is generate a variable resistance (or voltage) and nothing more.
No problem with that, use ADC to get the position/direction.

But, of course, I agree with Mooly, it's a not so easy task, even more so for commercial multichannel amp with little space left.

Gunawan W 12th December 2010 12:26 PM

How about this schematic? it use single pot....

diyparadise - all about volume control...

Mooly 12th December 2010 04:33 PM

Quote:

Originally Posted by Gunawan W (Post 2395708)
How about this schematic? it use single pot....

diyparadise - all about volume control...

Who are you trying to convince... ;)

How much current is going to flow via the pot wiper at the end of it's travel. I'll let you worki it out... I wouldn't count on the remaining good side of your pot staying good for very long though ;)

Gunawan W 13th December 2010 02:06 AM

Hi Mooly,
I don't know how much current...
I only knew that the right channel was broken, maybe it was because my daughter turn it at max at one time when I turn it it on... the amp is 100 watt per channel.

thank's

Mooly 13th December 2010 06:28 AM

The current is just ohms law.
A 5 volt supply
A resistor to limit current (stated as 24 to 100ohm)
The volt drop across the LED... say 2 volts.

So we 5-2 =3volts.
3 volts across 24 ohm is 0.125amp. As the pot is turned from zero resistance that current will burn the resistive track at the ends.

Why can you not just fit a normal pot... what's the problem. Must be far easier than all this.


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