London Power ad

[-]
Search the Forum








(Advanced Search)

Pots! What brands are good?
#1
What brands of pots do you guys use?  I lots of builder seem to favor the old style CTS pots but I've been using Alpha with no complaints for years.  There a lot of good prices on pots on AliExpress but I'm not sure of the quality. Does anyone have any experience with those brands? Thanks guys!
Reply
#2
Hi makinrose

For the most part, most brands of pot are pretty reasonable and the cost=quality notion is itself not entirely reliable. This means you can get a 25-cent pot that works well for decades and a very expensive one that fails or becomes noisy. Sometimes it is just a bad sample.

When I started building amps, I used whatever pots were available to me from local suppliers, or from broadline vendors as I found out about them. A lot of custom stuff and mods were done using "no name" pots. When I started building amps as company products, I standardised on PEC pots because they were needed for the Power Scale circuits I was using at the time. These are 28mm with smooth shafts as standard - no options for knurled shafts, just for shaft length when buying quantities.

PEC went a bit nuts with their pricing, so I designed them out and switched to 16mm pots everywhere. My local suppliers carried Alpha-Taiwan pots but the shaft lengths would vary with the pot value and taper. Needless to say, you want pots with uniform mechanical characteristics so you can use one style and type of knob. I found a Chinese supplier that I still use today and I can get the shaft length I prefer with knurled shafts that match the knobs I use.

When choosing pots, you have to keep in mind what knob you want to use. For example, when modifying Marshalls, you can buy Marshall knobs that have a set screw and fit 1/4" smooth round shafts, and knobs that are push-on to fit a T18 knurled shaft. This allows you to mix pots that are physically different. I'm seeing more styles of knobs that come in both set-screw and push-on forms, which greatly alleviates some of the problems amp builders and modifiers have finding such things.

For the hifi stuff I build, I use 1k linear and log pots from Bourns that are 9mm. I get these from Mouser.
Reply
#3
(02-25-2019, 05:38 PM)K O\Connor Wrote: Hi makinrose

For the most part, most brands of pot are pretty reasonable and the cost=quality notion is itself not entirely reliable. This means you can get a 25-cent pot that works well for decades and a very expensive one that fails or becomes noisy. Sometimes it is just a bad sample.

When I started building amps, I used whatever pots were available to me from local suppliers, or from broadline vendors as I found out about them. A lot of custom stuff and mods were done using "no name" pots. When I started building amps as company products, I standardised on PEC pots because they were needed for the Power Scale circuits I was using at the time. These are 28mm with smooth shafts as standard - no options for knurled shafts, just for shaft length when buying quantities.

PEC went a bit nuts with their pricing, so I designed them out and switched to 16mm pots everywhere. My local suppliers carried Alpha-Taiwan pots but the shaft lengths would vary with the pot value and taper. Needless to say, you want pots with uniform mechanical characteristics so you can use one style and type of knob. I found a Chinese supplier that I still use today and I can get the shaft length I prefer with knurled shafts that match the knobs I use.

When choosing pots, you have to keep in mind what knob you want to use. For example, when modifying Marshalls, you can buy Marshall knobs that have a set screw and fit 1/4" smooth round shafts, and knobs that are push-on to fit a T18 knurled shaft. This allows you to mix pots that are physically different. I'm seeing more styles of knobs that come in both set-screw and push-on forms, which greatly alleviates some of the problems amp builders and modifiers have finding such things.

For the hifi stuff I build, I use 1k linear and log pots from Bourns that are 9mm. I get these from Mouser.

That's very helpful.  I'm largely building and repairing vintage-type amps for customers so I'm often using set screw style pots and the smooth shafts with 3/8" bushings. My experience has been positive with the 16mm pots but customers often balk at "mini-pots". I'm going try out few different brands and find what I like.
Reply
#4
Hi makinrose

As TUTs say, magazine reviewers and most players lack the technical knowledge to state categorically that any specific component is "bad" let alone that an entire class of component is "bad". In your relationship with your customers, YOU are the technically knowledgeable party so it is YOU that decides if a pot is good enough for you to install. You end up either hand-holding your clients, or just do the job and do not discuss parts other than that parts you use are what you know to be good.

Some techs let the customer dictate component choice and let the chips fall where they may. This is particularly sad when $$$ parts like transformers are in question. Of course, if a customer like that comes along you are not obliged to accept their work.

Speculators on the internet are simply that: speculators, which in this case means "guesser", "gossiper", "parrot" - take your pick.
Reply
#5
(02-25-2019, 08:00 PM)K O\Connor Wrote: Hi makinrose

As TUTs say, magazine reviewers and most players lack the technical knowledge to state categorically that any specific component is "bad" let alone that an entire class of component is "bad". In your relationship with your customers, YOU are the technically knowledgeable party so it is YOU that decides if a pot is good enough for you to install. You end up either hand-holding your clients, or just do the job and do not discuss parts other than that parts you use are what you know to be good.

Some techs let the customer dictate component choice and let the chips fall where they may. This is particularly sad when $$$ parts like transformers are in question. Of course, if a customer like that comes along you are not obliged to accept their work.

Speculators on the internet are simply that: speculators, which in this case means "guesser", "gossiper", "parrot" - take your pick.

I totally agree.  It's been challenge for me.    After I read the TUT series a several years ago I realized how many little things I could do better with my builds and started to employ those changes over time.  The switch over to Galactic Grounding, better filtering,  better layouts, and more use of radial caps have all improved the sound and performance of my builds enormously but have also forced me to answer lots of questions from customers. I've stopped posting pictures of the inside of my amps. In fact  I've gotten to point where I don't allow customers to pick out parts at all but I still get lots of questions.  The question I get a lot is: "Is it exactly like the original amp?".   I don't mean to complain but it's wearying process contending with "internet experts" and the advertising people buy into.  

I'm definitely going to try out few different brands of pots and see what I think is good.  Thank you Kevin.  As you know good information is hard to find and I appreciate your advice.
Reply
#6
I like to use alpha pots with 8mm bushings. I like to use anti-rotation tabs, and the ones on the 8mm-bushing pots are more substantial (yet possibly a bit thinner). And the body of those pots seem to make better contact with the chassis.

I also like the feel of the alpha pots on amps. They have a nice feel (and audible swoosh, if you listen closely).
Reply
#7
Hi Guys

Jmcd: In other words, you are using 24mm pots. 16mm pots have about a 7mm bushing.

An "audible whoosh" is just from the noise in the circuit... you hope...

For either size, but likely more usual on the smaller pots, the bushing is cast aluminium along with the bushing and front face of the pot.i always use the anti-rotation tab, which requires drilling a small hole beside the hole for the bushing. The mechanical drawing for the pot you wish to use will give correct dimensions, or just measure the pots once you have them in hand.

Have fun
Reply
#8
(02-27-2019, 12:41 PM)K O\Connor Wrote: Hi Guys

Jmcd: In other words, you are using 24mm pots. 16mm pots have about a 7mm bushing.

An "audible whoosh" is just from the noise in the circuit... you hope...

For either size, but likely more usual on the smaller pots, the bushing is cast aluminium along with the bushing and front face of the pot.i always use the anti-rotation tab, which requires drilling a small hole beside the hole for the bushing. The mechanical drawing for the pot you wish to use will give correct dimensions, or just measure the pots once you have them in hand.

Have fun

Yes, 24mm pots. But with the smaller-diameter bushing.

The audible swoosh is mechanical and doesn't come through the speaker. It's due to the stiffness of the wiper, I guess. I like it on my amps but not on my guitars Smile
Reply


Forum Jump:

[-]
Come in where it's warm!
A warm welcome to those interested in tube and hi-fi audio! Fans of Kevin O'Connor's The Ultimate Tone (TUT) book series form a part of our population. Kevin O'Connor is the creator of the popular Power Scaling methodology for amplifiers.
Please remember these three principles: respect, sharing, community.
Not familiar with The Ultimate Tone book series? See discussion topics, or click here to visit London Power/Power Press Publishing.

[-]
Forum Hosted by London Power
London Power logo