three tap loudness pot

adason · 19th January 2006, 03:43 PM

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

sreten · 19th January 2006, 07:02 PM

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.

adason · 19th January 2006, 08:16 PM

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?

sreten · 20th January 2006, 10:19 AM

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.

adason · 21st January 2006, 08:13 PM

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

sreten · 25th January 2006, 07:21 PM

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.

lineup · 25th January 2006, 07:37 PM

I would never use anything but
10k - 47k potentiometers for audio inputs.

A good value is 22 kOhm or 25 kOhm log pot.

adason · 25th January 2006, 08:00 PM

you guys are right
i should abandon that idea
but it is a volume pot from an old console

sreten · 26th January 2006, 09:53 AM

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.

19th January 2006, 03:43 PM	#1
adason diyAudio Member Join Date: Nov 2004 Location: Maryland	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

25th January 2006, 07:37 PM	#7
lineup diyAudio Member Join Date: Dec 2005 Location: the north	I would never use anything but 10k - 47k potentiometers for audio inputs. A good value is 22 kOhm or 25 kOhm log pot. __________________ lineup

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19th January 2006, 07:02 PM	#2
sreten R.I.P. Join Date: Nov 2003 Location: Brighton UK	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.

19th January 2006, 08:16 PM	#3
adason diyAudio Member Join Date: Nov 2004 Location: Maryland	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?

20th January 2006, 10:19 AM	#4
sreten R.I.P. Join Date: Nov 2003 Location: Brighton UK	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.

21st January 2006, 08:13 PM	#5
adason diyAudio Member Join Date: Nov 2004 Location: Maryland	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

25th January 2006, 07:21 PM	#6
sreten R.I.P. Join Date: Nov 2003 Location: Brighton UK	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.

25th January 2006, 08:00 PM	#8
adason diyAudio Member Join Date: Nov 2004 Location: Maryland	you guys are right i should abandon that idea but it is a volume pot from an old console

26th January 2006, 09:53 AM	#9
sreten R.I.P. Join Date: Nov 2003 Location: Brighton UK	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.