vtm 60 audio vs. linear taper

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Nibbles
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Joined: Wed Sep 17, 2008 4:12 am

vtm 60 audio vs. linear taper

Post by Nibbles » Wed Sep 06, 2017 2:47 pm

Asking for a friend who can't log in.
So that nasty dirty ass VTM 60 I bought recently had the gain Pre and Post knobs broken off. Just a stub was left. No problem, I'll order new ones and replace. So I bought these from Ebay

http://www.ebay.com/itm/NEW-Peavey-5150 ... 2749.l2649

They came in today and I removed the old ones and put these in. First thing I noticed is that it was not as loud. Hmmmm. Both the knobs reacted more slowly compared to the old ones and to all the other VTM's I've owned in the past. So now I set the pre gain to 6 where I used to set it to 4-5 and I need to put the post gain (volume) at 5 to match what used to be 2. With the old pots 3 on the volume was loud as hell and easily overpower a heavy drummer. I never needed to go past that. With the new pots at 5 it starts to get loud and at 5 1/2 to 6 it gets glorious and there's still a ways to go. So I seem to be getting full volume but just at a different taper. I emailed the ebay shop with this....

"I just received my order for the Peavey 1 meg log/audio pots. I installed them and noticed something odd. The sweep is much different than before. Where the post gain pot on number 2 before was loud, now i have to turn it up to approximately 5 ish for the same level. It still gets loud as heck once I get up past 5, but before I couldn't even get close to 5. 3 was plenty loud to play with a loud drummer. The schematic calls for a 1M audio taper pot #71190516 and I just noticed that the number on the pots I received are 686ZA1M T (with a little \ through the Z. Did I get the correct part? Or more importantly, Did I install the wrong part? These are for a Peavey VTM 60 Pre and Post gain."

and got this reply

"It sounds like originally there was a linear taper in the amplifier. This happened a lot in production because they would either substitute a part or they would intentionally use a linear taper to make the amp feel like it was louder and more responsive. Fender did this a lot in their more recent tube amps as well.

The A1M in the part number would indicate it is a 1M audio taper potentiometer."


The pots I took out say 1 meg AUD and the number matches that on the schematic. And the pots I received say A1M, So are the old ones (including all the others i have owned) Audio taper pots that are acting like Linear taper? I'm confused. Like I said, it works great and I might even say it sounds better in some way. Honestly. I think it sounds better especially when I get it up to 5-6. So I'm not complaining and I don't want to redo them cause it's kind of a bitch with all those legs. But just curious.
Bun Splitter

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