alps pot for passive volume control

[soundnovice]

please suggest a good model number for alps pot to use as a simple passive volume control. i am looking for two of them each to use in monoblock amps.

 

[georgehifi]

Go one of these for each mono, choose resistance (1kohm-100kohm) depending on the input impedance of your amp, which we don't know.

ALPS Potentiometer RK27111 mono 1K 5K 10K linear o logarithmic Rotary | eBay

Cheers George

 

[soundnovice]

Thanks George.
that brings me to next question. how to find out the input impedance of the amplifier. the specs page don't specify for my amplifier.
my source is fiio x3 1st gen player which has a line out of 1.5Vrms and output impedance is given as 107Ω (which is typical i guess).

 

[georgehifi]

What is this amp? model and brand?

You can measure it with an ohmmeter (when it's not plugged in and on) so long as it's not capacitor coupled.

And "output impedance is given as 107Ω" is not right.

Cheers George

 

[soundnovice]

Norge 1000 Gold - Norge Audio
not sure if its capacitor coupled. will try to check with the manufacturer.

 

[georgehifi]

Norge 1000 Gold - Norge Audio
not sure if its capacitor coupled. will try to check with the manufacturer.

All I found
"Each amplifier features JFET inputs (for high input impedance)"

So get the 10kohm, that should do. 20kohm would be better if you can find it in a single.

Cheers George

 

[soundnovice]

oh wait....my plan is to first get rid of stock preamp and replace it with passive volume control. sorry I didn't mention earlier.

sent an email to you regarding lightspeed attenuator. pls check email

 

[tansand]

The volume knob on the front is a passive volume control, if you hit the 'tone defeat' you have the same thing..? It may well already have an alps RK27 in it..

 

[soundnovice]

the tone defeat is this actually dont cutoff the preamp stage, but massively desensitizes it. i guess by using big resistor. all in all, its not a very high end design. but the power amp itself is a good and old proven design.

 

[soundnovice]

i found an interesting link,
21 Step High Precision Step Potentiometer A10KX2

this talks about patent design. i verified that patent is indeed granted,
https://www.google.com/patents/CN201270178Y?cl=en

not sure how this is different from DACT type pots

 

[soundnovice]

as George pointed out earlier and after reading some stuff, i find that its mainly the input impedance of the power amp that should be matched with passive preamp.
i want to keep the system as simple as possible (aka very low budget!) for now. thats why hunting for a decent volume control solution.

 

[tansand]

i found an interesting link,
21 Step High Precision Step Potentiometer A10KX2

this talks about patent design. i verified that patent is indeed granted,
https://www.google.com/patents/CN201270178Y?cl=en

not sure how this is different from DACT type pots

Ha, good for them, that's a good idea! They made the gap between the contacts in an s shape to make the switch hit the next contact before it leaves the last one (make before break). This is so there aren't switching noises as you turn it. Nice job! I assume the DACTs are make before break, but the entire switches are of a different design.