Is some Pot better than others?

[ALL212]

I think it's in the Crack area that I read we can use 50k ohm to 250k ohm volume controls.  What would be the advantages/disadvantages between those extremes?  What would I hear differently if I put a 250k in over a 50k?

Sorry about the title...  :

Thanks!

 

[Doc B]

Why not buy a few different inexpensive pots and try it yourself?

 

[ALL212]

Might I theorize and just see where I end up?

Both start with infinite resistance but the 250k has "further" to go before it gets to 0?  The 50k will be louder quicker on the dial?

 

[ALL212]

I don't mind showing my shortage of knowledge. 

Why have different values?  Does this help match the impedance of the next stage - power amp?

 

[Grainger49]

It has to be a high enough resistance that the source won't clip.  By that remember, the lower the resistance the more current it "draws".  If it draws more current than the source is capable of the source clips, that is runs out of voltage before it delivers all the current the load/pot draws.  I=V/R explains that.  A 10k Ohms is usually enough. 

Tubed equipment always have higher.  The output of the pot feeds the grid. 

I'm sure Dan, PJ or PB can fill in why tubes need higher resistances.

 

[ALL212]

OK...I give.  ???

Who's got the best book on beginner electronics?  Something to do with dummies would work really good for me!

I kinda get it but don't go crazy trying to explain.  I've stretched the limits of my high school electronics course from 40 years ago and that's probably as far as it's ever going to go!  ;D

 

[Paul Birkeland]

Sorry, I had to throw that in... I couldn't help myself.

Anyway, back to what you're asking, it's important to figure out what "better" means for you.  There are pots like the PEC pot that sound great, but have pretty bad channel balance at low levels.  Any stepped attenuator with fixed resistors will have incredible balance between channels, but not all resistors end up sounding as good as the trusty carbon pot.

Pot impedance is application specific.  Some devices prefer the lower impedance for stability reasons (a lot of solid state electronics, and the Mainline for that matter), tubes in particular need a low enough resistance that electrons draining from the first grid don't form a bias voltage (unless you actually want that), but shouldn't be so low that your sources will have trouble driving it.  If you are looking to build a passive preamp, then the impedance of the pot will help determine how well you might be able to drive a length of cable, and that would be an application that would call for a lower impedance pot.  In the stock BeePre and Smash, the balance and volume control pots interact, and their values end up being important for proper functionality. 

In our gear, a 50K or 100K volume pot replacement is a fine choice.  It's quite unlikely that you'll hear much (if any) difference between a 50K and 100K pot from the same product line.
-PB

 

[cspirou]

Anyway, back to what you're asking, it's important to figure out what "better" means for you.  There are pots like the PEC pot that sound great, but have pretty bad channel balance at low levels.  Any stepped attenuator with fixed resistors will have incredible balance between channels, but not all resistors end up sounding as good as the trusty carbon pot.

What makes a pot 'sound great'? Do poor ones have uneven frequency response? Most of what I read says the main difference is channel imbalance. Does adding channel balance control make a cheaper pot sound as good as a more expensive pot?

 

[cspirou]

OK...I give.  ???

Who's got the best book on beginner electronics?  Something to do with dummies would work really good for me!

http://www.amazon.com/Make-Electronics-Discovery-Charles-Platt/dp/0596153740

 

[Paul Joppa]

What makes a pot 'sound great'? Do poor ones have uneven frequency response? Most of what I read says the main difference is channel imbalance. Does adding channel balance control make a cheaper pot sound as good as a more expensive pot?

Channel balance is easily measured, so it gets trotted out a lot. Nobody really knows why some potentiometers seem to sound better than others - there are no accepted measures, so you can't make a technical argument. Perhaps it's a mass hallucination, perhaps it's something we have not yet discovered; perhaps we'll never know.

 

[ALL212]

Just another thought.  I've ran through about a dozen integrated amps and receivers from the 1970's into the early '80's.  Sansui and Yamaha were (and still are) my favorites from that era.  Many of those amps (40 to 50 years old) have pots that look just like the BH stock pots.  Pretty much every one of those amps needed to have the volume pot cleaned with a spray cleaner.  I didn't have to replace any of them but I had many that a channel would drop out at a certain position or a channel or both channels would get distortion (scratchy sounding). 

I'm in my mid 50's.  In 40 years I'm not gonna care if that BH thing I built has a scratchy spot on the volume - I should, by rights, be dead and gone by then.  If not dead my hearing will probably be so degraded I'll be on hearing aids so it won't matter.  But there are fairly economical sealed pots that are a step up mechanically that should last longer with fewer issues.

I like the concept of the ladder pots.  Just move down the resistance chain of single resistors (per channel).  Sweet and simple. 

Only amp I kept from those early amps was the Sansui AU9500 and I have the matching tuner.  Damn thing looks like it could control a nuke facility with all the buttons and switches on it!

 

[4krow]

For one reason or another, I have replaced pots, stepped attenuators, and the like. Keeps me scratching my head as to why or what I will prefer in one instance and not the other. Trouble is, that now days, you can't always be sure what your getting, at least from Ebay. Lately, I tried a TDK pot to change out a stepped atenn., and whaddya know, I like the TDK MUCH better. But to put it in perspective, the stepped atten was from Ebay, and loaded with Dale resistors (or so it read). I was having strange little volume and balance problems until I switched it out. Now, that may more like a comparison between a faulty product and a decent one, but I will also say that for whatever reason, the sound is just cleaner with the new pot. Perhaps if quality can be addressed first, there is less reason for other concerns.

 

[Grainger49]

I haven't ever changed my stock pots.  Shocking as the signal passes through it.  I use the volume pots almost wide open and control the volume with a Creek OBH-10 (remote volume control). 

Odd, I have an Alps Black Beauty waiting in the aisles.  And have a blue Alps balance control.  Those should be fitted into my preamp.  Again, after all the signal is passing through the stock Alpha pots. 

But those old Alpha pots don't scream out for replacement.  So I should see if it makes a difference.

 

[amioutaline?]

I've trotted out the following on several Forums since I did a test 12 years ago with Diyhifisupply Ella. The Ella run in Triode with a few mods like a choke in the power supply, Kiwame resistors a few places and Cree Schottky diodes. Test done over several days.

Alps Blue has treble harshness, Alps Black images better without the treble harshness but still a treble up-tilt.

TKD makes better imaging and a smooth frequency response with good but not great  inner detail (things like hearing Bassoons double French Horns or Rythm behind lead guitar)

Goldpoint attenuator with Dales well balanced, excellent imaging but kinda hi-fi-ish un-musical. And those Clicks!

PEC pot much like the TKD but even less inner detail and as CP wrote, channel imbalance.

Painting the transfomer covers red made everything sound better.

I stayed with the TKD and used another one to greatly improve an ARC LS-1 along with 86ng all those white bypass Caps.

Current fave is the VALAB (Ebay) 23 Step attenuator but soldering to the SMDs is not for the weak. Or unlucky. Buy 2, they're cheap. The Foreplay 2.1 sounds great with it.