Potentiometer with strange value

[micromegas]

Hi folks,

I'm about to buy some parts for building a pair of Firefly ODs I bought from Nick, the guy from NOC3.
Looking at the schematic it says the tone pot is 25kL. I've tried to contact him with no exit.

As the other pots are marked with and 'A' I presume 'L' stands for linear, am I correct?

I don't know if I'm right posting the schem here but you sure can find it at FSB.


Thanks in advance.

[selfdestroyer]

Everything I can find says L is for Log. Lots of older Fender amps make ref to that. Hope that helps.


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[Scruffie]

Let's see the schematic, shouldn't be too hard to take an educated guess as to what taper it should be.

[micromegas]

here it is:

[micromegas]

I've seen another desing from Nick (the Pure Drive) and he uses 'A' and 'B' designations but also 'L' for the treble pot

[RobA]

It looks like a modified Big Muff T.C. so I'd guess it's supposed to be a linear pot. Unless the small value for the pot really causes the two sides to interact more and that in turn calls for a log. I'll look at the frequency response and see what it looks like.

Edit: I put the values in the Duncan Amps Tone Stack Calculator and assumed a 50k linear pot. The 50k matches the value of the pot plus the two extra resistors (R10, R9). From looking at the pot action there on the frequency response, I really think the intention is a linear pot.

[micromegas]

It looks like a modified Big Muff T.C. so I'd guess it's supposed to be a linear pot. Unless the small value for the pot really causes the two sides to interact more and that in turn calls for a log. I'll look at the frequency response and see what it looks like.

In his description of the AMZ Presence Control, Jack Orman refers to the linear pot of the BM as 100kL, so maybe you're right.

As I have 2 PCBs I think I'm going to try both pots and compare

[micromegas]

thank you guys 

[RobA]

Just to make sure you see it. I edited my post above with the results of looking at the frequency response as you were looking at my original reply. I'd guess even more now that it is supposed to be a linear pot.

[micromegas]

Just to make sure you see it. I edited my post above with the results of looking at the frequency response as you were looking at my original reply. I'd guess even more now that it is supposed to be a linear pot.

Thanks Rob!

[Scruffie]

Went out for a bit but Rob hit the same conclusion I would have come to