kOhm ratings on Volume Pots

[Infinitely Baffled]

I think this is probably a foolishly simple question, but ...
does the resistance rating of a volume pot (ie. a 10k vs a 100k vs a 500k etc) affect how loud the music comes out for a given input signal, volume pot position and power amplifier? I realize that the resistance rating of the pot is important for matching it to the electrical characteristics of different types of system, but I'm finding that after replacing the broken 100k volume pot in my passive pre with a 50k type everything sounds a bit "hot" and I'm having to listen with the volume knob lower down the scale than I'm used to. Sounds reasonable to you folks?
IB

[farflungstar]

I'm sure Arkless will explain it...

Adey

In perpetual pursuit.

[tubehunter]

Normally no

Have you fitted the same type e.g. Logarithmic or Linear

[Infinitely Baffled]

Normally no

Have you fitted the same type e.g. Logarithmic or Linear

It's one of these:
http://www.ebay.co.uk/itm/1318686239...%3AMEBIDX%3AIT
I assume it's log, since it is designed for an audio pre-amp application. But I notice that in fact the listing does not specify explicitly. In use I would say it becomes very loud very quickly - say, the first six clicks of the 21 positions get me up to the loudest I could endure in my living room. Above that, successive clicks don't seem to increase the volume very noticeably, but that's maybe just that my ears are in meltdown by then!
IB

[tubehunter]

The ALPS 50KAX2 has an audio taper where as the 50KX2 doesn't.

It's easy to check which type you have by using a multi-meter and measuring the resistance sweep.

here's a poor diagram



The Quad 34 uses three pots of which two are linear (tilt, bass)

[Infinitely Baffled]

Thanks, Duncan, for taking the time to do this - very helpful. From your explanation I am betting that I have bought a linear type. I will check the resistance values later today. Serves me right - should be more careful!
Cheers
IB

[Reffc]

The value of a pot won't per-se, affect how loud your music plays. It will affect the useful range of volume sweep you have to play with. Depending on source output impedance and power amp input impedance, it can also affect frequency response if badly matched.

Basically, most audio pots tend to be log pots, which allow a useful sweep of volume range for finer control. Where un-buffered passives are concerned, you have to be careful with pot value because having a source with a high output impedance may mean that it cannot drive the load (Pot) without affecting the frequency response, usually where the pot value is too low. If the pot value is too high for a passive, then you have a similar issue with driving the power amp, since usually an optimum value is 10 times or greater when looking at source output impedance to amp input impedance (a rule of thumb which doesn't always reflect what a circuit is capable of driving, but a useful rile nonetheless). This is an over simplification of how the impedance figures are actually calculated just to make the point.

It is also dependant upon the input sensitivity of your amp compared with the gain from your source/preamp. If you have a 2Vrms output from your source, and say a 1v input sensitivity on your power amp, and you use a linear pot, it will sound "hot" because you're achieving full output from the power amp much sooner on the volume dial than you would have been with the log pot. You can use attenuators (Andrew at Rothwell makes very good attenuators) to reduce the gain from your source if this is the case. Most digital sources don't actually need any gain so most active amps these days need only buffer the signal for the purposes of getting a good low output impedance to drive the power amp, but some still use gain, especially valve pres with no negative feedback.

[Arkless Electronics]

Precisely what I warned about in our email exchange Gary....

[Infinitely Baffled]

Precisely what I warned about in our email exchange Gary....

I know (he said sheepishly). Unfortunately I thought I was buying log
Nobody's fault but mine, but it would have helped if the Ebay seller had included the word "linear" in the description, or perhaps described it as a tone control pot.
Shame really, as it sounds rather nice, it's just that there's not much effective control of the output level.
I'm a bit wary of going the Alps Blue route as the product description on the Hi-Fi Collective website only guarantees a channel match of <3 dB - that's twice the voltage isn't it? Doesn't sound great for a channel match! Also, I have heard they can sound a bit shrill. The TKDs are getting to be a bit costly for a passive pre that is really just a "spares box" item. Can't get hold of Sfernice any more, as far as I can see. Maybe I'll just stick with the linear one and put up with limited control.
Thanks to all for the help, and also for ReFFC's interesting mini tutorial.
IB.

[Arkless Electronics]

I know (he said sheepishly). Unfortunately I thought I was buying log
Nobody's fault but mine, but it would have helped if the Ebay seller had included the word "linear" in the description, or perhaps described it as a tone control pot.
Shame really, as it sounds rather nice, it's just that there's not much effective control of the output level.
I'm a bit wary of going the Alps Blue route as the product description on the Hi-Fi Collective website only guarantees a channel match of <3 dB - that's twice the voltage isn't it? Doesn't sound great for a channel match! Also, I have heard they can sound a bit shrill. The TKDs are getting to be a bit costly for a passive pre that is really just a "spares box" item. Can't get hold of Sfernice any more, as far as I can see. Maybe I'll just stick with the linear one and put up with limited control.
Thanks to all for the help, and also for ReFFC's interesting mini tutorial.
IB.

Alps Blue has been my "go to" vol pot for 20 years or so... very good. Channel matching is excellent, and is in fact their raison d'etre...