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Old 19th January 2006, 02:43 PM   #1
adason is offline adason  United States
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Default three tap loudness pot

Hi friends,

I need your help in finding the schematics for 1 mohm three tap loudness pot. Yes I searched. Here and elswhere. There are some threads about loudness in general, but not the schematics or detailed article how to calculate the parts.

This is an old but probably very high quality pot. Its big, the biggest I have seen, taken out from an old console. It says its 0dB. Must be precise. It's 1 megaohm, three taps. I would like to buit a versatile volume regulator with it. Probably fully passive at first, and later with high and low fr. outputs for biamplification purposes, the outputs will be buffered. I would like to have all the taps working, with option to turn them on/off, which should give me many fr. responses, thus eliminating the need for active preamp.

Any help is appreciated.
Thanks,
ed
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Old 19th January 2006, 06:02 PM   #2
sreten is online now sreten  United Kingdom
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Hi,

you've no chance of building a versatile passive preamp with a 1 Meg pot.
It simply will not be able to drive cable capacitance at high frequencies.

/sreten.
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Old 19th January 2006, 07:16 PM   #3
adason is offline adason  United States
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hi sreten,

than it has to be buffered
but 1 mohm pot is what it must be built around
still just the pot and the buffer should sound a lot cleaner than whole preamp shebang
don't you think?
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Old 20th January 2006, 09:19 AM   #4
sreten is online now sreten  United Kingdom
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Hi,

if you buffer it I presume it will work but will have relatively
poor noise performance due to the high impedances.

Arguably a 10K pot passive preamp will be a lot better.

/sreten.
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Old 21st January 2006, 07:13 PM   #5
adason is offline adason  United States
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nobody? anybody? please I need the schematics for parts in three tap loudness pot 1 mohm
there must be many tube amps using this



ps: sreten, I completely agree with you, but as I explained, this is what I have and would like to use
i still believe that 1mohm pot as a passive part (even if I will end up buffering it) will have lot less noise than whole preamp with few op's
active parts have lot more noise, thats what I want to avoid
by using loudness with many taps, i can possibly find the combination, which will satisfy, so i do not have to use bass/treble control
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Old 25th January 2006, 06:21 PM   #6
sreten is online now sreten  United Kingdom
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Hmmm.......

Its very easy to implement a completely passive preamp with tone settings.

I can't see the point of the 1meg multi terminal pot.

/sreten.
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Old 25th January 2006, 06:37 PM   #7
lineup is offline lineup  Sweden
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I would never use anything but
10k - 47k potentiometers for audio inputs.

A good value is 22 kOhm or 25 kOhm log pot.
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Old 25th January 2006, 07:00 PM   #8
adason is offline adason  United States
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you guys are right
i should abandon that idea
but it is a volume pot from an old console
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Old 26th January 2006, 08:53 AM   #9
sreten is online now sreten  United Kingdom
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I meg makes sense when dealing with the output from
ceramic cartridges and valve stages with no output buffer.

In a console you can keep the leads from the valve stage
very short and thus keep treble loss to manageable levels.

All that High Z circuitry is one reason valve consoles
were never famous for having low noise floors.

/sreten.
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