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Old 1st December 2004, 07:38 PM   #1
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Default Converting a DACT series pot to a shunt pot

Hi all,

Recently replaced the ALPS blue pot in my passive pre with a 100k DACT and that was a spectacular upgrade-clear, clean, open, detailed.
This is a series pot, i.e. the audio sigal has to pass through all the resistors (up to the point set by the pot). I have been told that shunt pots are better, but DACT does not make one.

Anyone with an idea of how to mod the series pot to a pseudo-shunt?
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Old 1st December 2004, 08:09 PM   #2
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If your DACT is a 2 deck type, which it probably is, you won't be able to do a ladder attenuator, except for just one channel.

You would need another 2-deck DACT or a 4-deck type.


Carlos
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Old 1st December 2004, 11:18 PM   #3
moamps is offline moamps  Croatia
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Default Re: Converting a DACT series pot to a shunt pot

Quote:
Originally posted by Dr.H
.... 100k DACT....This is a series pot.. ...... idea of how to mod the series pot to a pseudo-shunt?
This is possible, but I don't recommend it. (removing SMD resistors, soldering another.. a very tricky and costly business)

Regards,
Milan
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Old 1st December 2004, 11:22 PM   #4
moamps is offline moamps  Croatia
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Quote:
Originally posted by carlmart
... ladder attenuator...

As I understand, we're discussing the pseudo-shunt attenuator.

Regards,
Milan
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Old 2nd December 2004, 12:17 AM   #5
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It's very easy: just place a fixed 10k series resistor and use your DACT as switchable shunting element, from fixed resistor to ground.

I did that with my Sonic Fronteers attenuator and it worked fine. You will loose some gain, but it shouldn't be a problem.

This type of attenuator is not necessarily better than series switcher or a good pot, btw.
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Old 2nd December 2004, 01:34 AM   #6
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Quote:
Originally posted by moamps


As I understand, we're discussing the pseudo-shunt attenuator.


Sorry, my mistake.
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Old 2nd December 2004, 06:27 AM   #7
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Thanks everyone, will try and post results.

One other question: A couple of years ago, Stereophile posted a DIY plan for a buffered pre-amp (Aunt Corey's premap). The detail is still available at the stereophile website.

Has anyone tried this?
Does the use of a buffer improve the performance of the passive pre?
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Old 2nd December 2004, 01:11 PM   #8
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It will depend on your system and the setup, but chance are it will. But it has to be implemented very well, otherwise it will bring too much coloration.

I myself prefer an active preamp, over the passive pot.
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Old 2nd December 2004, 01:51 PM   #9
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Active preamp vs pot vs switchable output transformer. Are you changed your opinion, Peter ? Not long time ago, I think that you was prefer trafo.
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Old 2nd December 2004, 01:55 PM   #10
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Quote:
Originally posted by Peter Daniel
I myself prefer an active preamp, over the passive pot.
And I prefer TVC over active preamp on classical and jazz material

But this also is not set in stone. On some days my preferences are quite different.

But most of the time I'm using modified ML380S preamp in my secondary system and S&B102 in my main system.

In my workshop I have PEC pot mounted directly on amps input. I enjoy all 3 systems.
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