Phase 90 reverse log pot

[darrylportelli]

so Ive almost finished my phase 90 but need a rev log pot. I cant find it where I live. would a normal log pot or a linear do the job?
Thanks

[jacobyjd]

They'll work--all of the adjustment may feel like it's in a small portion of the pot travel though.

You could also try adding a resistor with a value equal to the pot value across the outside legs of a linear pot that is twice the value of the pot you need. This will give you a reverse log...sort of.

[darrylportelli]

I'm gonna go with normal log thn mate 10x for the info but I didnt understand exactly what u ment the "twice" piece...... what ive understood is that if with a linear pot you solder a resistance the same value of the pot to the outside legs you got rev log right???

[darrylportelli]

oh now I understand( I have to learn to read thoroughly!!!) so If I need a 500K rev log pot I can use a 1M linear pot with a 1M resistor soldered between the outside legs right??
Thanks

[jacobyjd]

That's absolutely correct Sorry for the lack of clarity.

[darrylportelli]

no worries mate, just another question which is totally unrelated to the rev log pot......the circuit at tonepad uses those matched jfets 2n5952,could I use j201's instead of them since a while back me and my friend ordered bout 50 of em and we havent used much of em so I have plenty to match
Thanks

[jacobyjd]

If you can find 4 matching ones in that pile of 50, good luck--however, most of what I've read about the circuit involves people saying that j201s are one of the worst choices to use, since they seem to vary the most.

I remember reading some posts in the Tonepad build reports where people listed the jFets they used with good results--that might be a good place to look to find an alternative

[frequencycentral]

I had trouble finding 2n5952's for my Phase 180 build. I did a search and found a post where R.G. recommended 2n5485's as a suitable sub, so I ordered 30 and managed to get 3 matched sets - just lucky I guess. They work well too.

[darrylportelli]

Thanks Josh Ill take a look right now......Thanks rick if I dont find where to buy 2n5952's I ll give the ones you listed a try.I asked about the j201's since I had some laying round but Ill save em for another build (we ordered them cos geofex's stompbox circuits are full of j201's and where we live we couldnt find any)

[bumblebee]

They'll work--all of the adjustment may feel like it's in a small portion of the pot travel though.

Yep, its all messed up. I had to replace the pot in mine and i tried linear, audio etc and they all felt wrong. Its only recently I realized I need reverse log.

[Mark Hammer]

You can use a normal 500k log.  Just wire it up opposite.  Stock, the reverse-log pot is wired up so that wiper-to-outside-lug resistance gets smaller as you go clockwise, making the speed faster.  If you take the wire going to the normal outside lug and simply connect it to the opposite side on a standard log pot, you'll have the same proportional resistance change as a reverse-log, except going in the other direction.  That is, turning clockwise increases pot resistance and slows the LFO down.  I did this on my P90 and it works like a charm.