CTS pots New vs Vintage

[RockinRocket]

Guys Ive searched google with no luck. Whats the difference between the old ones ken used vs the new production? Is it just the taper? Or something more invasive like the element ect? Thanks

[David Root]

Could be materials in the element....30 years is a long time. Also I'm not sure if the mid to late '80s CTS would be 30% taper.

If you want to spend a few $$ without trolling Ebay for NOS CTS, try Mojotone for 30% taper new CTS, (they had some special ordered) and buy some regular (10-15% I think) taper as well, and compare them. These are the good ones with solid brass shafts not the nasty plastic ones.

Ken also like pre-Hecho en Mexico AB Type J RV4 pots too. The only Trainwreck I have built so far (Express) used those including some very old ('50s-'60s) 1M Type J that were all 30% taper. They sound great.

[RockinRocket]

I was thinking of going Mojo for their CTS. I have a AB Type J 25k. Dosnt say RV4. Mine is a 10%.. 3k at half and 29k total. Ken used a linier pot in the schematics. Not really sure what I was looking for through all the AB pots and item codes. You wouldn't know the item # for a 25k liner AB pot im looking for with the correct shaft length?

So Ken used 30% pots? I vagley recall folks were looking for 10% pots and I remember PECs were at 10%.
Thanks for the help

[RockinRocket]

I did some digging because I swore I remembered 10% taper pots. Turned out Glen mentioned his Vol pots on his amps were less than 10%.

http://ampgarage.com/forum/viewtopic.ph ... highlight=

I'll mention one something I've noticed with my original Ken built Express amps.

The pots Ken used were fairly cheap basic parts, however he was quite good at selecting pot models that had very smooth tapers even in a fairly high gain circuit. For example my '85 Express is barely playing when it's up to about 2, is still clean on about 4, then 5 to 6 gets moderately gainy, but there is still a big change in gain going from 6 to full up. Heck even 3/4 to full up is a noticeable change. This is with a stock Express circuit that is no different than what most clones use today, and with all typical gain 12AX7s in V1, V2 & V3. I did some investigating on the volume pots on my '89 and '85 Express and noticed yes they are obviously "analog taper" but tend to be quite exaggerated in the smooth slope, especially the volume pot in my '85 Express. For example that volume pot measured out quite a bit passed 1 meg overall, but when 1/2 way up the measured value was only at 80k being not even 10% of the full on value. I've measured other "analog" taper pots made these days and just about all of them ramp up more quickly. It seems "analog" tapers pots are not all created equal, not even close.

Ok, all that to say if you build a clone and the volume control seems like a light switch you might try swapping out the volume pot for something else. You might even try some old NOS parts as slower rising tapers seemed to be more common with older production pots a couple decades back at least. Note how 50s Gibson guitars have quite slow smooth taper pots, it seems like it was more the norm back then. Anyway having a very slow rise of the amp pots makes the controls much easier to dial in, even with the stock Express circuit. Oh, also having a slow rising taper on the treble control will also make a big difference. I know this sounds like something you could just compensate for by not turning up the knobs so far, however with slower rising taper pots it spreads out the sweet spots making variations in sound much easier to find.

GK"

[brewdude]

For some reason I was under the impression that 30% taper was considered by many to be more desireable? It always seemed to that a slow taper would be easier to control.

[andresound]

Gentleman,.... just purchase your spares from Rj. My express pots are PERFECT and behave smoothly throughout their "sweep". Also measured them before install and they are close to 10% taper!!

And what a great dude to deal with

[David Root]

I'll have to check my old AB 1M pots. I thought they were all 30% taper.

[jjman]

30% seems way to close to liner to work in a volume application to me. The graphs I've seen all show ~10% for non linear and non-reverse types.

[RJ Guitars]

... Ok, all that to say if you build a clone and the volume control seems like a light switch you might try swapping out the volume pot for something else. You might even try some old NOS parts as slower rising tapers seemed to be more common with older production pots a couple decades back at least. Note how 50s Gibson guitars have quite slow smooth taper pots, it seems like it was more the norm back then. Anyway having a very slow rise of the amp pots makes the controls much easier to dial in, even with the stock Express circuit. Oh, also having a slow rising taper on the treble control will also make a big difference. I know this sounds like something you could just compensate for by not turning up the knobs so far, however with slower rising taper pots it spreads out the sweet spots making variations in sound much easier to find.

GK"

IMHO - this was well put and worth repeating...

[pdf64]

A ~30% taper works well in lower gain amps, eg classic BF Fender, for volume and treble controls.
Where the system that has a greater range of control may benefit from the greater resolution provided by lower % tapers.

[Mark]

10% for volume, 30% for treble, 10% for bass and mid controls.
Presence can be 30% or linear. Typically this works best for me.