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/131868623994?_trksid=p2057872.m2749.l2649&ssPageName=STRK%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

http://i514.photobucket.com/albums/t350/halx00/volume%20pots_zpspgaequx8.jpg (http://s514.photobucket.com/user/halx00/media/volume%20pots_zpspgaequx8.jpg.html)

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

http://i514.photobucket.com/albums/t350/halx00/quad%2034%20inside_zpszhwdr4gp.jpg (http://s514.photobucket.com/user/halx00/media/quad%2034%20inside_zpszhwdr4gp.jpg.html)

http://i514.photobucket.com/albums/t350/halx00/quad%2034%20pots_zpsimyhgmjk.jpg (http://s514.photobucket.com/user/halx00/media/quad%2034%20pots_zpsimyhgmjk.jpg.html)

[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 :doh:
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 :doh:
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...

[Arkless Electronics]

A cheap partial get round would be log faking resistors..... check it out here http://sound.whsites.net/project01.htm

[Barry]

I was going to suggest that, but couldn't find the link. Well done. :)

[Infinitely Baffled]

A cheap partial get round would be log faking resistors..... check it out here http://sound.whsites.net/project01.htm

Hmm ... that's quite tempting. It appeals to the "Mr Fixit" side of my nature. My only reservation is that in the write up it says that this workaround is good provided the gain structure of the pre-amp is suitable. I'm interpreting this as meaning that if you have too much gain, you will be running with your volume knob down at the bottom end of its travel where the behaviour of the pot is still more or less linear. By the time you get up to the recommended 10 o'clock to 2 o'clock position when it starts to simulate log behaviour, it's already too loud. I can see that being the outcome. Of course, I could then solder in a few resistors to attenuate the incoming signals before they reach the pot. But by this stage I might as well buy an Alps Blue and have done with it ... ! But thanks for the suggestion anyway, Jez.
IB

[Firebottle]

For the sake of two resistors I'd say try it. Have you got suitable resistors?

I can pop a couple of 6K8 resistors in the post if you haven't.

:)

[Arkless Electronics]

For the sake of two resistors I'd say try it. Have you got suitable resistors?

I can pop a couple of 6K8 resistors in the post if you haven't.

:)

Ah! Just beat me to it! I was going to suggest much lower... 2k2 say.

[Infinitely Baffled]

For the sake of two resistors I'd say try it. Have you got suitable resistors?

I can pop a couple of 6K8 resistors in the post if you haven't.

:)

You're a diamond geezer, Alan! Many thanks. I'll PM you my address.
Cheers
Gary

[Infinitely Baffled]

Ah! Just beat me to it! I was going to suggest much lower... 2k2 say.

The Hi-Fi Community working like a well-oiled machine! Thanks for that, Jez. I took up Alan on his offer, and I'll report back on the forum with what I find. Do you suggest I dip them in anything in particular before installation?;) Cheers. Gary.

[Arkless Electronics]

The Hi-Fi Community working like a well-oiled machine! Thanks for that, Jez. I took up Alan on his offer, and I'll report back on the forum with what I find. Do you suggest I dip them in anything in particular before installation?;) Cheers. Gary.

I'll be selling audio grade carrot juice for only £300 a litre shortly... free magic beans with order for first 10 customers :D

[Yomanze]

If your source can handle it, check out some innovative work in this area: https://www.audialonline.com/topics/model-a-volume-control/

Sent from my SM-G920F using Tapatalk

[montesquieu]

I'll be selling audio grade carrot juice for only £300 a litre shortly... free magic beans with order for first 10 customers :D

Does it come with a free fuse?

[Marco]

No, it comes with a free feel.... He's kinky that way ;)

Marco.

[Infinitely Baffled]

If your source can handle it, check out some innovative work in this area: https://www.audialonline.com/topics/model-a-volume-control/

Sent from my SM-G920F using Tapatalk

Interesting, Neil. I have read elsewhere about the growing popularity of shunt-type volume control arrangements. Being a bit of an untutored dabbler, however, I need very simple solutions. Plus for this particular passive pre, which is something that gets hauled out and pressed into service only occasionally as a temporary solution, I am not willing to throw a lot of money at it. Thanks for pointing this out, though. Cheers. IB.

[RothwellAudio]

I'll be selling audio grade carrot juice for only £300 a litre shortly... free magic beans with order for first 10 customers :D

Sorry Jez, that isn't audiophile at all - price per litre? You need to sell your carrot juice at £300 for a 10mL bottle. The stuff is precious and isn't meant to sloshed around all over the place, it needs to be carefully applied one drop at a time with the supplied cotton bud - which is a cryogenically treated cotton bud, of course.
Then again, carrot juice can never compete with C37
http://www.ennemoser.com/c37theory.html

BTW, if you can make any sense of C37 please explain it to me :scratch:

[Arkless Electronics]

Sorry Jez, that isn't audiophile at all - price per litre? You need to sell your carrot juice at £300 for a 10mL bottle. The stuff is precious and isn't meant to sloshed around all over the place, it needs to be carefully applied one drop at a time with the supplied cotton bud - which is a cryogenically treated cotton bud, of course.
Then again, carrot juice can never compete with C37
http://www.ennemoser.com/c37theory.html

BTW, if you can make any sense of C37 please explain it to me :scratch:

Ah right! I'll put up the price and include a fuse that has passed through the digestive tract of a Civet cat... as one is getting far less for ones money I'll obviously put the price up further to make it even more effective.

I had a quick glimpse at C37..... Having seen the light I'll be using these principles from now on... how stupid I've been to believe in all that Ohm's Law mumbo jumbo for all these years...

[Infinitely Baffled]

I took up Alan on his offer, and I'll report back on the forum with what I find.

Well, blow me down. This log faking business really works!
Alan's resistors arrived in this morning's post. They were absolutely minuscule, which was good because that made them far easier to install in the limited space available in my little box - you could very nearly fit them in between the pins on the pot. When I tried it out, I found the volume level still rose a little more steeply than you might be used to for the first few millimeters of rotation. But then it all became quite comfortable and the rate of adjustment became quite gradual at typical listening levels (ie. "robust", without being downright loud). As an illustration, a good solid listening level for records and radio is now achieved with the volume control knob at 10 clicks (out of 21), CD might be a click or two lower depending on the production of that particular disc. Brilliant! I'm up and running without having to buy yet another volume pot. Many thanks to all contributors, and esp to Alan for donating the resistors. Imagine how good a fix this would have been if the resistors had been bigger, though!
Cheers.
IB

[Firebottle]

Those aren't minuscule, they are standard 0.4W metal film I'll have you know ;)

You should see the size of surface mount resistors fitted in modern kit, well actually you would find it difficult to see them :eek:

http://www.resistorguide.com/resistor-sizes-and-packages/

[Infinitely Baffled]

Those aren't minuscule, they are standard 0.4W metal film I'll have you know ;)

http://www.resistorguide.com/resistor-sizes-and-packages/

Was only acting silly, Alan. They sound damn' fine, whatever they are. Cheers. Gary.