How to reduce attenuation of a 25k pot?

pburke · 28th March 2005, 05:31 PM

Hi,

I have a couple nice 25K Noble pots and would like to use them for a headphone amp/DAC output (DDDAC1543 with 16 DAC chips). The problem is that the attenuation of those pots is far too aggressive for what I need. No matter how I wire them, it's almost an on/off situation. I think a 2k attenuator would be more appropriate for what I need.

Can I just add a resistor in parallel with the attenuator to reduce it's range, or would that mess up the pots logarhythmic curve?

Peter

homer09 · 28th March 2005, 06:01 PM

i dont see how a different value pot will attenuate less or more.

sounds to me like you wired your pot wrong. A properly wired pot functions as a voltage divider. What determines attenuation is ratio between the two parts of the resistor (separated by the wiper). So if you have a 2k pot or a 1Meg pot, the attenuation will be the same!

check that you have not wired your pot backwards as an anti-log pot. This would mean that instead of voltage input slowly increasing in a logarithmic fashion, it would go the other way, increase very fast than slowly producing an almost on/off behaviour when used as a volume control.

Bill Fitzpatrick · 28th March 2005, 06:10 PM

It sounds to me like you have the phones attached to the pot wiper. If that's the case you are going to need a headphone amplifer circuit after the pot.

pburke · 28th March 2005, 06:32 PM

actually, the pot was wired correctly and the wiper was going to ground. However, I had it before the coupling caps and not after, which messed with the DAC's vref... d'uh!

trying it behind the caps now.

Peter

28th March 2005, 05:31 PM	#1
pburke diyAudio Member Join Date: Nov 2003 Location: Madison Wisconsin	How to reduce attenuation of a 25k pot? Hi, I have a couple nice 25K Noble pots and would like to use them for a headphone amp/DAC output (DDDAC1543 with 16 DAC chips). The problem is that the attenuation of those pots is far too aggressive for what I need. No matter how I wire them, it's almost an on/off situation. I think a 2k attenuator would be more appropriate for what I need. Can I just add a resistor in parallel with the attenuator to reduce it's range, or would that mess up the pots logarhythmic curve? Peter

28th March 2005, 06:01 PM	#2
homer09 diyAudio Member Join Date: Jan 2004 Location: Montreal	i dont see how a different value pot will attenuate less or more. sounds to me like you wired your pot wrong. A properly wired pot functions as a voltage divider. What determines attenuation is ratio between the two parts of the resistor (separated by the wiper). So if you have a 2k pot or a 1Meg pot, the attenuation will be the same! check that you have not wired your pot backwards as an anti-log pot. This would mean that instead of voltage input slowly increasing in a logarithmic fashion, it would go the other way, increase very fast than slowly producing an almost on/off behaviour when used as a volume control. __________________ Most people wouldn't know good music if it came up and bit them in the ***. - Frank Zappa

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
attenuation using I/V	ailouros6	Digital Source	14	15th October 2008 06:20 PM
XLR to RCA with attenuation pad.	KOL69	Everything Else	1	24th April 2008 11:10 PM
hum attenuation	AndrewT	Power Supplies	3	2nd July 2006 09:12 PM
10 dB attenuation box	june	Parts	2	20th July 2004 04:07 AM
Attenuation	Nappylady	Multi-Way	3	18th February 2003 12:07 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	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

28th March 2005, 06:10 PM	#3
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	It sounds to me like you have the phones attached to the pot wiper. If that's the case you are going to need a headphone amplifer circuit after the pot.

28th March 2005, 06:32 PM	#4
pburke diyAudio Member Join Date: Nov 2003 Location: Madison Wisconsin	actually, the pot was wired correctly and the wiper was going to ground. However, I had it before the coupling caps and not after, which messed with the DAC's vref... d'uh! trying it behind the caps now. Peter

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)