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Old 10th April 2007, 10:28 PM   #1
Chispa is offline Chispa  United States
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Default multi-channel volume control

I want to build a preamp that controls eight channels. I need a way to control the volume with one knob in a way that will affect every channel. I dont want to try to find an eight way potentiometer, there should be another way. Is there a way to do this and maintain fidelity?
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Old 10th April 2007, 10:36 PM   #2
Chartal is offline Chartal  Canada
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You can have a look at these two web site, they both make a pre-amp project with PGA2310 volume control and PIC for 7.1 channels.

http://www.electro-dan.co.uk
http://www.mhennessy.f9.co.uk
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Old 11th April 2007, 11:41 AM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
search for the (at least three) threads that discuss digital control of attenuator chips.

The relay attenuators can also be extended to multichannel. Again at least two threads.
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Old 12th April 2007, 12:21 PM   #4
SamL is offline SamL  New Zealand
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Have a look at Jos's design. Not the cheapest but hight quality with the goodness of remote control.

http://jos.vaneijndhoven.net/switchr/design.html
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Old 16th April 2007, 04:03 AM   #5
Chispa is offline Chispa  United States
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I am a third year electrical engineering student with NO experience with anything audiophile. I looked online and became convinced that I could get into audiophile sound by building the stuff myself. I am on a tight budget, but have a lot of time, and a lab that can etch circuitboards.

Looking at the more successful posts on this site, Ive reallized that I need to be specific about what I want, and make a list of things I need help with. So I will try and do this properly. Even if it doesnt get alot of responses, I will keep this as a log of my ideas and success or failure in their implementation.
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Old 16th April 2007, 07:18 AM   #6
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Perhaps with a dc volume control...

I have found many IC with dc volume control but I don't know
if there is also an pre-amplifer IC

Yes, preamplifier with dc volume and tone control
LM 1036 (National)

http://www.national.com/pf/LM/LM1036.html


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Old 16th April 2007, 07:21 AM   #7
Chispa is offline Chispa  United States
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I want to build a reciever that will output 2.1 sound for a CD player, a turntable, and two other stereo inputs. I want it to be able to take in 8.1 sound from a dvd player, and a hometheater PC. I want to be able to switch from one source to another, enabling or disabling the extra six channels as required.

I need to be able to control all the channels with a single volume control, preferably a rotary control, but button control if it is a lot cheaper/easier to do. A remote would be nice, but it may be a luxury I cannot afford on this project.

I have built a pair of 60W amplifiers using Rod Elliott's P3A design shown on http://sound.westhost.com/. I plan on building 3 more pairs for the satellites, as well as a pair of his P68 amplifiers for the subwoofer channel. I will put the individual channel volume controls on the amplifiers to avoid complication in the reciever.

My budget for the reciever is about US $100 I can go a little more, would prefer to keep it less. I would like to keep the sound quality as high as possible within the budget constraint.
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Old 16th April 2007, 07:21 AM   #8
Chispa is offline Chispa  United States
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I am pretty green when it comes to reading these forums. As AndrewT pointed out, the information is all out there. I just need to learn the language better. A digitally controlled attenuator is exactly what I need, but I didnt know what one was until he pointed that out.

As much as Im learning in University, the classes are still teaching the basics, about broad subjects while this is very specific to high fidelity sound. My idea of volume control was a varable negative feedback circuit involving an opamp. From what Ive read, this is not the best way to keep good fidelity. I need your help to do this project with any amount of success.

I need help with the volume control. I dont know how the digital potetiometers work and I dont know how to implement the attenuation in a circuit in a way that wont affect the sound. From what I understand the volume knob should be an encoder that sends a signal to a programable processor. The processor decodes the signal and sends another signal to the potentiometer.
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Old 16th April 2007, 07:31 AM   #9
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look the LM1036 http://www.national.com/ds.cgi/LM/LM1036.pdf

This ic have a low distortion (0.06% typical for an input level of 0.3 Vrms)
With dc controls You can regulate all amplifiers with only a Tension = with a single potentiometer.
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Old 16th April 2007, 08:10 AM   #10
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Also look for variable Gain Amplifier (VCO) with DC control.
http://www.analog.com/en/subCat/0,28...0%255F,00.html
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