I need Help Please noob/boob.

ppcblaster · 28th April 2007, 05:59 PM

First amp, I am Building a Stereo BrianGT chipamp.

All I have is a 500K dual Audio pot for the volume control.

How will using a 500K pot, instead of, say a 100K or 50K

pot affect the amp?

Thank You

ianpengelly · 28th April 2007, 08:59 PM

You will have to turn it further to get the required volume.

Whether there is anything more than this I'll leave to someone more knowledgable to comment, but I can't imagine it is really a problem.

jaycee · 29th April 2007, 12:00 AM

It will work but you might find two things:

1) some source components won't be happy driving this sort of load. It may increase distortion

2) you will find that you will get noise introduced into the signal, particularly when the control is turned up midway. This is called Johnson noise.

Get yourself a good quality 22-47K dual logarithmic pot. It doesn't have to be some fancy "Audio Grade" part... if you really want to push the boat out, look for one with conductive plastic tracks.

ppcblaster · 29th April 2007, 12:35 PM

Quote:

Originally posted by jaycee
It will work but you might find two things:

1) some source components won't be happy driving this sort of load. It may increase distortion

2) you will find that you will get noise introduced into the signal, particularly when the control is turned up midway. This is called Johnson noise.

Get yourself a good quality 22-47K dual logarithmic pot. It doesn't have to be some fancy "Audio Grade" part... if you really want to push the boat out, look for one with conductive plastic tracks.

Would you please post some examples? I have searched for days.

Thank you

ianpengelly · 29th April 2007, 06:05 PM

I use an Alps Blue and that works like a charm, more expensive than your stanard Radio Shack component, but not as pricey as the really exotic stuff (re: Audio Note)

Minion · 30th April 2007, 05:08 PM

I use standard 10k Log or Lin Pots in my Gainclones and I don"t have any Problems at all....you could probably even use a 5k in a Pinch.... I would try to stay lower than 50k or so because of the Increased Impedance seen at the Input....

Cheers

ianpengelly · 1st May 2007, 07:49 AM

I think I have a 150k pot after looking inside my Cambridge Audio amp and seeing that it was of a similar value, so far I have had no issues with this pot, but then I have nothing to compare it to.

d to the g · 1st May 2007, 05:04 PM

I use the 50K log from Mike Percy Audio. It's not the cheapest part(~$20), but it came highly recommended. It's been great so far, but as I haven't tried other solutions I can't compare it to anything.

Stuey · 4th May 2007, 11:59 AM

PPC, you'll see in Brian's instructions that there's a 25K pot at the input on the circuit diagram. My reading of late on this forum seems to indicate this is the most appropriate for a plain non-inverting setup without buffer.

Taiwan Alpha (or just 'Alpha') make very good low cost pots - they make both a standard looking metal bodied one (which is what I used) and also a small green plastic bodied one which has had very good reports. When buying mine, I took a multimeter to the store and tested for equal resistance between channels at various points between the 9 o'clock to 3 o'clock positions.

Cheers

Stuey

ppcblaster · 4th May 2007, 09:00 PM

Thank You All

28th April 2007, 05:59 PM	#1
ppcblaster diyAudio Member Join Date: Jul 2006	I need Help Please noob/boob. First amp, I am Building a Stereo BrianGT chipamp. All I have is a 500K dual Audio pot for the volume control. How will using a 500K pot, instead of, say a 100K or 50K pot affect the amp? Thank You

4th May 2007, 09:00 PM	#10
ppcblaster diyAudio Member Join Date: Jul 2006	Thank You All Thank You All

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28th April 2007, 08:59 PM	#2
ianpengelly diyAudio Member Join Date: Oct 2006	You will have to turn it further to get the required volume. Whether there is anything more than this I'll leave to someone more knowledgable to comment, but I can't imagine it is really a problem.

29th April 2007, 12:00 AM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	It will work but you might find two things: 1) some source components won't be happy driving this sort of load. It may increase distortion 2) you will find that you will get noise introduced into the signal, particularly when the control is turned up midway. This is called Johnson noise. Get yourself a good quality 22-47K dual logarithmic pot. It doesn't have to be some fancy "Audio Grade" part... if you really want to push the boat out, look for one with conductive plastic tracks.

29th April 2007, 06:05 PM	#5
ianpengelly diyAudio Member Join Date: Oct 2006	I use an Alps Blue and that works like a charm, more expensive than your stanard Radio Shack component, but not as pricey as the really exotic stuff (re: Audio Note)

30th April 2007, 05:08 PM	#6
Minion diyAudio Member Join Date: May 2006	I use standard 10k Log or Lin Pots in my Gainclones and I don"t have any Problems at all....you could probably even use a 5k in a Pinch.... I would try to stay lower than 50k or so because of the Increased Impedance seen at the Input.... Cheers

1st May 2007, 07:49 AM	#7
ianpengelly diyAudio Member Join Date: Oct 2006	I think I have a 150k pot after looking inside my Cambridge Audio amp and seeing that it was of a similar value, so far I have had no issues with this pot, but then I have nothing to compare it to.

1st May 2007, 05:04 PM	#8
d to the g diyAudio Member Join Date: Aug 2006 Location: minimalopolis	I use the 50K log from Mike Percy Audio. It's not the cheapest part(~$20), but it came highly recommended. It's been great so far, but as I haven't tried other solutions I can't compare it to anything.

4th May 2007, 11:59 AM	#9
Stuey diyAudio Member Join Date: Mar 2006 Location: Perth, Western Australia	PPC, you'll see in Brian's instructions that there's a 25K pot at the input on the circuit diagram. My reading of late on this forum seems to indicate this is the most appropriate for a plain non-inverting setup without buffer. Taiwan Alpha (or just 'Alpha') make very good low cost pots - they make both a standard looking metal bodied one (which is what I used) and also a small green plastic bodied one which has had very good reports. When buying mine, I took a multimeter to the store and tested for equal resistance between channels at various points between the 9 o'clock to 3 o'clock positions. Cheers Stuey

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