50K or 100K pot? - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 8th November 2003, 12:32 PM   #1
2Bak is offline 2Bak  Denmark
diyAudio Member
 
Join Date: Apr 2002
Default 50K or 100K pot?

Since I'm really happy with the sound of my gainclone, I'm going to build another one.
My first gainclone was a four-channel power amp version using the attached circuit, except for a fixed 100K resistor to ground at input.
For the new one, which will have a volume control, I wonder if can I use a 50K linear pot instead of a 100K pot? What are the drawbacks?

Thanks /Jan
Attached Images
File Type: jpg invertedlm3875_small.jpg (17.7 KB, 658 views)
  Reply With Quote
Old 8th November 2003, 12:44 PM   #2
diyAudio Member
 
li_gangyi's Avatar
 
Join Date: Jun 2003
Location: Woodlands Circle
try not to use a linear pot...unless you really have to or you are just experimenting...I guess 50K will work too...
__________________
Kids in the back seat cause accidents...Accidents in the back seat cause kids...
  Reply With Quote
Old 8th November 2003, 12:50 PM   #3
diyAudio Member
 
Join Date: Sep 2003
Location: Illinois
What really is the difference with using linear tapers? For all of my amps, I always use a 25K 10% tolerance linear made by Allen Bradley (at least thats what the box says, I didn't buy them, I was given them).

Do the audio ones made a large difference?
  Reply With Quote
Old 8th November 2003, 12:51 PM   #4
2Bak is offline 2Bak  Denmark
diyAudio Member
 
Join Date: Apr 2002
Default Re: 50K or 100K pot?

Quote:
Originally posted by li_gangyi
try not to use a linear pot...unless you really have to or you are just experimenting...I guess 50K will work too...
OK, then I have a 100K log. pot I could use.
Does "linear taper" on the circuit not refer to a linear pot...?
  Reply With Quote
Old 8th November 2003, 01:13 PM   #5
diyAudio Member
 
Join Date: Sep 2003
Location: Illinois
Taper/Pot, same thing
  Reply With Quote
Old 8th November 2003, 01:23 PM   #6
diyAudio Member
 
li_gangyi's Avatar
 
Join Date: Jun 2003
Location: Woodlands Circle
hmmm...wonder why they would want you to use a linear one though...
__________________
Kids in the back seat cause accidents...Accidents in the back seat cause kids...
  Reply With Quote
Old 8th November 2003, 04:51 PM   #7
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
Default Pots

I am again and again wondering that people use pots with high resistance in semiconductor circuity. It is relict of " tube age ", where gain stages had great output impedance, which must had only little " load ". Today, when typical output impedance of any semiconductor machine is 100 Ohm or lower, is it nonsens. In this case optimal resistance of pot should be approximately 1 kOhm, but it is very hard to made ( in logaritmical version ). So use 10 Kohm pot - you get lower noise and much more independet frequency charakteristic in every positions of pot.
  Reply With Quote
Old 8th November 2003, 05:27 PM   #8
Pedja is offline Pedja  Serbia
diyAudio Member
 
Join Date: Jun 2002
Location: Belgrade
Default Don’t wonder!

Quote:
Originally posted by Upupa Epops
I am again and again wondering that people use pots with high resistance in semiconductor circuity. It is relict of " tube age ", where gain stages had great output impedance, which must had only little " load ". Today, when typical output impedance of any semiconductor machine is 100 Ohm or lower, is it nonsens.
The reason of usage 100k is here more related to the goal of obtaining logarithmic curve with linear potentiometer since its wiper is always loaded with 10k resistor. This is the relict of the theory that the linear pot sounds better than logarithmic. (The theory has technical merits but I must say that my listening experience did not confirm this theory.) However, with logarithmic pot (and wiper loaded with 10k), the resulting curve might appear “overcompensated”.

But, more important: the circuit’s output impedance is not necessarily related to the circuit’s driving ability. Only a minor part of the transistor circuits around wouldn’t mind if you load them (even) with 10k.

Quote:
Originally posted by 2Bak
For the new one, which will have a volume control, I wonder if can I use a 50K linear pot instead of a 100K pot? What are the drawbacks?
With 220k in the feedback I'd rather use 50k than 100k pot.

Pedja
  Reply With Quote
Old 8th November 2003, 05:54 PM   #9
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
It is also my experience that 50k pot works better than 100k. And log taper works more realistic in IGC than a linear (by that I mean more uniform control range). It all depends on a split, but most common Japanese pots are usually 10/40 and not 10/90.

I'm using old production Nobel pots, 31 detented positions, mono. I match them before installing and it is not that hard to actually match them to 0.2dB or better accuracy. They also sound pretty good, very claean and not romantic.
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 8th November 2003, 06:01 PM   #10
diyAudio Member
 
Join Date: Aug 2003
Location: Prague,Czech Republic
Pedja, I certainly know that this concrete circuit will have approximate logaritmic curve, but I say, that his impedance is too high, what is wrong in " noise look ". My note was general, not concrete to this circuit.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
=>$100k Amplifiers !!! Bonsai Solid State 19 29th November 2008 03:39 PM
100K pot in a preamp? G Tubes / Valves 5 15th May 2008 02:41 PM
Noble 100K pot. mattjk Swap Meet 0 21st January 2008 02:50 AM
EL-34 and 100k pot podboy Tubes / Valves 1 26th June 2007 11:49 PM
50K vs 100K POT ss1 Parts 7 22nd July 2004 12:57 PM


New To Site? Need Help?

All times are GMT. The time now is 11:15 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2