A better volume control solution
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gavinbirss

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Hello,

I know that many diyers out there are scratching thier heads for better volume control circuits that using a good volume pot.

Some of there solutions are
* dsp chips
* DAC 's with volume control
* digital pots : DS1802, CS3310, PGA2310 ....

I was looking at using a VCA (Voltage Controlled Amplifier) and in particular the SSM2164 and SSM2018T as a substitute to using the above solutions.

Due to some constraints of my own I would appreciate other diyers taking this project further that what I can.

Gavin
 
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Doh

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The problem I've had with the digital pot solution is that they all seem to require either an input capacitor, a buffer chip, or both. Neither seems like a good idea for pairing with an all-discrete capacitor-free design like the KG amp.

Recently, I've been thinking of creating a relay-based volume control in ladder attenuator style so that i can have both the convenience of remote control operation and have a nice volume control.

I would appreciate hearing what others have to say on this subject as well.

-Doh
 
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Budgie

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Seems like I remeber a well respected passive preamp being pretty much what you just described, Doh. The Placette, I think it is called.
(edit)Found it-http://www.placetteaudio.com/
 
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mlloyd1

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The DS1808 feeding a discrete JFET buffer (or the KG preamp) may be a good solution. It is just an attenuator and control logic - no internal op amps like the CS3310, PGA2310, etc. devices.

However, I've been unable to get samples of this part out of Maxim. I wonder if it actually exists yet or is vaporware.
 
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Tomo

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Hello,

Why not passive volume control with old fashioned pots?

Digital attenuator requires independent power supply. And, I don't feel like adding a whole another electrical system.

Looking for good tracking in log-pots is very hard. This is a part of the reason why people like stepping attenuator. Also, having a signal going thru the resistive plastic layer doesn't do good the sound.

Try using linear pots in shunt type attenuator. This way you can get logarithmics and signals will go thru least amount of plastic resistive layer.

I got myself a pair of really high quality resistors (10 USD a pair!) and a Nobel pot to build my current passive preamp. It sounds extremely transparent and it costed me less than the value of a rotary switch.

Please note that # of resistors that signals go thru matters very similarly. It does sound no good, if it has to go thru multiple resistors. That is why series type stepped attenuators are not as good as ladder type or shunt type (***)

Tomo

P.S. I have 5 rotary switches. I was planing on building a passive preamp with them, but after this I have a feeling I will never use them. Yes, it is that good.

(***) Shunt type attenuator has varying input impedance. So the source sees different load when volume is changed. So you must use proper precautions when you design yourself one for maximum performance.
 
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gavinbirss

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Hello,

I feel it necessay to to enphasize that using the SSM2018T and other from Analog (VCA's) is said to be better that digtal solutions and the signal does not go through the pot that is used in conjuction with the VCA.

Tracking is said to be within 0.1db.

I was hoping that you guys were already prototyping with these chips.

Who is brave out there ?


Gavin
 
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