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4.8 ohm headphone pot? Need some help here
Old 20th July 2005
  #1
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4.8 ohm headphone pot? Need some help here

I have a stereo headphone pot w/ 2 gangs of three tabs,
I measured w/ a multimeter on the outside tabs of both gangs and I'm getting
a measurement of 4.8 ohms.

I want to order a new pot, but I'm not seeing anything in digikey or mouser
w/ less than 1K ohms?

Does this measurement sound off?

If it's just gonna be a few bucks, with some help I might be able to make an educated guess and order one. Unless the values for stereo headphone pots are just all over the place.
Can anybody tell me what a good guess might be?

It's a pot for two stereo mix headphone outs on a Yamaha PM1000 mixing board.

For wattage too? Would a 1/2 watt be good?
Old 20th July 2005
  #2


One of the tabs you are measuring may be the wiper.

You didn't mention if this was used as a passive attenuator or as a trim on the input to the headphone amp.

Either way, 4.8 ohms end-to-end sounds funny...

The only thing where that reading might make sense is on L-Pads from input to output.

You should measure both resistances with the wiper in 3 or 4 positions.



-tINY

Old 21st July 2005
  #3
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vince @ speck's Avatar
 

Quote:
Originally Posted by Jonk
I have a stereo headphone pot w/ 2 gangs of three tabs,
I measured w/ a multimeter on the outside tabs of both gangs and I'm getting
a measurement of 4.8 ohms.

I want to order a new pot, but I'm not seeing anything in digikey or mouser
w/ less than 1K ohms?

Does this measurement sound off?

If it's just gonna be a few bucks, with some help I might be able to make an educated guess and order one. Unless the values for stereo headphone pots are just all over the place.
Can anybody tell me what a good guess might be?

It's a pot for two stereo mix headphone outs on a Yamaha PM1000 mixing board.

For wattage too? Would a 1/2 watt be good?

It seems that a pot to adjust the headphones on a mixer like the PM1000 would be a common dual audio taper pot in the range of 5K - 20K. That is, a pot ahead of a amplifier circuit. I can't imagine a low-Z pot that would "directly" feed headphones. Maybe I'm wrong, but I've never seen anything like that on a mixer.

You might need to remove the pot from the mixer to make an accurate measurement.

I don't mean to sound like a teacher, but maybe you should take a measurement on a "control" value (no pun) just to make sure your meter is working. Something like a 10K resistor.
Old 21st July 2005
  #4
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Well,

I opened the sucker up and cleaned out some of the crap so it's working better. I can put up w/ it a bit longer now.

the wiper is indeed at the center tab.

My meter (Fluke 8010M, I believe. It's not in front of me right now) has been very accurate for voltage readings, though this is one of the few things I've measured the ohms on. But yeah, I'll try a resistor I know the value of.

I'm measuring the pot while it's still in the headphone module but the module is removed. Are you saying I should de-solder the connections to the pot too to get an accurate reading?
Old 21st July 2005
  #5
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brianroth's Avatar
 

Measuring resistance with a component in-circuit is dicey, at best.

Bri
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