Phaser transistors

[soldersqueeze]

 I'm going to build me a Smoothie and have a question regarding transistors. My regular parts supplier sells matched sets of 2N5952's, but only as sets of four. Presuming the seller has matched them OK, would I be able to just use two of the four without testing them further?
Thanks for any advice

[jimilee]

Yes, just remember the pin outs are reversed. Guitarpcb sells 2 and 4 also.

[soldersqueeze]

Excellent, thanks!
Guess I'll be building two of them, can't have transistors laying around going to waste....

[jeffaroo]

or get a pair of 2N5952's and a pair of 2N5457's and slap them on a switch and run the switch to the pcb then you would have a switch of twirly delight !

[DutchMF]

Contact Jakob Kokura (he's around here a lot), he might have a few left

Paul

[midwayfair]

Contact Jakob Kokura (he's around here a lot), he might have a few left

Paul

If Jacob doesn't have any left, I have some matched 2N5457s I can part with.

[jimilee]

or get a pair of 2N5952's and a pair of 2N5457's and slap them on a switch and run the switch to the pcb then you would have a switch of twirly delight !

That sounds like a most excellent idea.

[jeffaroo]

i like you jimmi...dont know why, ugly as hell ! but if you didnt live so damn far away id buy you a beer

[midwayfair]

or get a pair of 2N5952's and a pair of 2N5457's and slap them on a switch and run the switch to the pcb then you would have a switch of twirly delight !

Why do you think this will do anything "delightful"?

The transistors are are not part of the audio circuit. They control the bias on the op amps in the phase splitting section. Using a different set of transistors would require rebiasing after switching or else phasing is unlikely to happen. If you match different types of FETs to the same VGS such that they don't require rebiasing, they will sound the same when you switch.

Although it's possible that you could get a different depth of phasing with different devices, it's much easier to just install a depth pot.

[jkokura]

Contact Jakob Kokura (he's around here a lot), he might have a few left

Paul

If Jacob doesn't have any left, I have some matched 2N5457s I can part with.

I have lots left.

Jacob

[jimilee]

i like you jimmi...dont know why, ugly as hell ! but if you didnt live so damn far away id buy you a beer

Thanks, I'm not sure if I should be flattered or offended.

[jeffaroo]

or get a pair of 2N5952's and a pair of 2N5457's and slap them on a switch and run the switch to the pcb then you would have a switch of twirly delight !

i recomended this because he was wandering away from the stock circuit that calls for 2N5457 he was going to use 2N5952. if there was a difference he would atleast have a option to still be stock

[jkokura]

or get a pair of 2N5952's and a pair of 2N5457's and slap them on a switch and run the switch to the pcb then you would have a switch of twirly delight !

i recomended this because he was wandering away from the stock circuit that calls for 2N5457 he was going to use 2N5952. if there was a difference he would atleast have a option to still be stock

From the Smoothie documentation:

The Phase 45 originally used 2N5952 JFETS. The Smoothie lists 2N5457 for Q1 and Q2 because they are more widely available and work just as well as the 2N5952. You may use either, but keep in mind that the pinout for the 2N5952 is opposite the 2N5457. This means you will need to rotate the transistors 180° on the PCB if you use 2N5952.

The 2N5952 is still widely available, and as far as matched pairs, is sold by several individuals on the various DIY forums as well as some of the PCB shops. Matched pairs and quads are easy to come by, but you can spend a bit more money and get a bunch for you to match yourself. Matching them is pretty easy, either with a PCB project that's available here on the forum that I designed, or simply using a breadboard.

I'll reiterate what Jon pointed out - the type of JFet you use doesn't matter. What matters is that they're matched. The better they're matched, the more symmetrical the phase sound will be. MXR is famous for not really matching their jFets closely, so that's why some Phasers are reported to sound better than others. Some say they shouldn't be matched exactly.

When I match, I try to match with a tolerance of .005 mV. I often get a match of .001 or .002 between four transistors. I don't know that anyone else matches to that level tolerance. I think Barry at GPCB matches to .01.

jacob

Jacob