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Old 9th December 2009, 09:09 AM   #1
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Default Looking Schematic converting Volume pot to Digital Vol for tube amp.

I wonder if anyone build a converter to convert analog Tube Preamp to Digital Volume ?

is there a schematic ?

what's the difference in term of the sound quality if I use Digital Vol ?




regards
cal
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Old 9th December 2009, 09:26 AM   #2
Arnulf is offline Arnulf  Europe
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What is this "digital volume" - a stepped attenuator (manual or MCU controlled) ? Cut the wires, remove old potentiometer, insert new attenuator, apply power (if you've got one of the MCU controlled gadgets), done !

Make sure you get one with similar/same nominal resistance.

Quality ? depends on the quality of components used but I can't see fixed resistors performing any worse than worn out carbon track of a regular potentiometer ...


BTW, i've been planning to make me an IR controlled stereo stepped attenuator module with input channel select for a while now. The idea was to use reed relays instead iof regular relays in order to avoid loud clicking noise and to prolong its lifespan. Would there be any interest in such a project ?
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Old 9th December 2009, 10:06 AM   #3
Gordy is offline Gordy  United Kingdom
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Quote:
Originally Posted by calico88 View Post
I wonder if anyone build a converter to convert analog Tube Preamp to Digital Volume ?

is there a schematic ?

what's the difference in term of the sound quality if I use Digital Vol ?

regards
cal
Cal, as a very general statement; there is no performance advantage over a high quality manual control such as a stepped attenuator. However digital does give accurate channel balance and the possibility of remote control.

Have a read here for a selection of digital volume control ideas:
Hi-Fi Preamp - Analogue Research

My suggestion is to consider a high quality potentiometer from a company such as TDK. However if you have a lot of money go for an attenuator such as the 41 step example from:
Acoustic-Dimension, high-end audio and components for tube audio

If you want remote control of a potentiometer there is a project here:
Infrared Remote Control for Audio

Or a complete kit here:
Dantimax - Remote control audio kits

Or a relay switched system here:
Audio Volume Relay Attenuator with IR Control

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Old 9th December 2009, 12:52 PM   #4
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Gordy,
thank you for the link, I will study those specially the digital Vol Idea.

What I'm gonna do is to convert a analog vol to digital, since there is no degradation on the SQ and even better balance I think it's a good one.

this is the sample that I want to do with digital Vol.
Emmeline, The Shadow, a portable amp with digital volume control. - Ray Samuels Audio

the problem is (my project), I need little/tiny space, smaller than a stereo potentiometer or at least about the same size.

I wonder if there is a chip, SMD, for this with schematic of how to turn the analog to digital using this small chip like 8 pins chip ?

I'm not an expert of electronic, I just built base on the schematic.
I'm looking for DIY project who's already done this.


Cal
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Old 9th December 2009, 02:24 PM   #5
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There are many volume control ICs. Most people use the Maxim parts because some of them can be used without a processor, though the TI and Cirrus parts are better in my opinion.

Maxim - Parametric Search - Product Table

Volume Controls - Amplifiers and Linear - TI.com

Volume Control - Analog Volume Control, Digital Volume Control

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Old 9th December 2009, 04:05 PM   #6
Magz is offline Magz  United States
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I believe these IC volume units work by attenuating the input signal using resistors and then amplifying it back up to the selected level using opamps. Some of them even provide gain above the level of the input signal. Although they sport low THD figures, some die-hard tubeys might balk at putting opamps in the signal path.
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Old 9th December 2009, 06:52 PM   #7
piero7 is offline piero7  Italy
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Quote:
Originally Posted by Gordy View Post
Cal, as a very general statement; there is no performance advantage over a high quality manual control such as a stepped attenuator. However digital does give accurate channel balance and the possibility of remote control.

Have a read here for a selection of digital volume control ideas:
Hi-Fi Preamp - Analogue Research

My suggestion is to consider a high quality potentiometer from a company such as TDK. However if you have a lot of money go for an attenuator such as the 41 step example from:
Acoustic-Dimension, high-end audio and components for tube audio

If you want remote control of a potentiometer there is a project here:
Infrared Remote Control for Audio

Or a complete kit here:
Dantimax - Remote control audio kits

Or a relay switched system here:
Audio Volume Relay Attenuator with IR Control

forget the dantimax one, there are some problems with its volume controller
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