Using 50mw pots for line level?

[electric_diaries]

Hi all!

I made a simple 4 channel mixer a while ago and the pots need replacing. Space is tight in there so I was hoping to use some ALPS rk09 style pots but I am wondering if the are underrated for the job.

The pots are a stereo attenuator (currently 20k duel log) at the input which then feed through a 10k resistor into a virtual ground mix amp. I have done some Ohms law calculations which tell me that they are good for much more than then +4dB level I plan to feed through them, but I was wondering if anybody here has suggestions or experience in this type of thing?

Would switching to 50k be a better idea?

HERE are the pots I am talking about.

THANKS!

 

[Harpo]

Level will not be higher than supply voltage in respect to reference voltage.
Maybe 15Vdc^2/20000ohm giving 0.01125W, so your 0.05W rated part looks ample. Even more so for audio level being Vac.

 

[PRR]

"Line level" is traditionally 1 milliWatt.

Today we often work "line level" *Voltage* in much higher impedances, like 1.23V (+4dBu) in 20K.  It's inside the box, not out on a telephone pole; we don't have to fight-off interference from streetcars and arc-lamps. 1.23V in 20K is 0.075mW.

To be honest, we should allow for a peak-factor, and the fact that someday someone may hold it at MAX level long enough to read THD or something. Say 10V RMS, in 20K, is 5mW. With +/-18V rails you won't get even 12V RMS, 7mW.

I think your 50mW parts are ample.

 

[ruffrecords]

"Line level" is traditionally 1 milliWatt.

My rule of thumb for pots. 1 milliwatt into 10K is 10V rms which is +22dBu

Cheers

Ian

 

[electric_diaries]

Thankyou the internet!

 

[PRR]

> My rule of thumb for pots. 1 milliwatt into 10K is 10V rms

10^2/10,000 = 100/10,000 is 1/100W or 10 milliWatt on my abacus.

Has one of us dropped a zero?

 

[ruffrecords]

> My rule of thumb for pots. 1 milliwatt into 10K is 10V rms

10^2/10,000 = 100/10,000 is 1/100W or 10 milliWatt on my abacus.

Has one of us dropped a zero?

Oops, I knew the rule was more memorable than that. It should be:

10mW in to 10K is 10V rms

Apologies.

Cheers

Ian