JFET alternatives for Boss PH-1 Phaser. Can I use any matched quad?

[neiltheseal]

Hello

As the heading says, I was planning on building a Boss PH-1 and wanted to know if they type of JFET was essential.

Aion FX says to use 2SK30A but note that 2n5457 is the same. So could I simply use matched 2n5457s here or even J201s?

Thanks in advance.

 

[szukalski]

2SK30A-GR Is what I used in SMD.

 

[neiltheseal]

Thanks. I was going to buy SMD jfets and try my hand at matching them myself. I have a whole lot of J201 and 2n5457s. Ideally I would use these rather than buy a batch of 2SK30A-GR in order to get enough that are matched.

 

[Paradox916]

You can get matched pairs quads from Aion, a lot of people have asked the same question about the j201s but I haven’t heard or seen anyone that it worked for. The specs aren’t the same I believe

 

[jimilee]

I used j201s in another phaser, but you have to change some values, they have more gain and are harder to calibrate.

 

[neiltheseal]

I used j201s in another phaser, but you have to change some values, they have more gain and are harder to calibrate.

What phaser did you use the j201s in?

 

[jimilee]

It’s an older one called the phazex

 

[Cybercow]

From what I can make of matched JFETS for phasers that use them, most any matched set should would work. Mind you, that besides matching the JFETs, the Vgs(Off) parameter of different JFETs can vary by as much as ~7V, the value of the resistors strapped across the Drain & Source of the phasing JFETS may need to be addressed/modified. I've noted that while the Boss PH-1 has 100K resistors strapped across the Drain & Source for use with 2SK30A devices, while the similarly designed MXR Phase 90 has 22K resistors strapped across the Drain & Source for use with 2N5952 devices.

 

[neiltheseal]

Down anyone know how many smd jfets I should buy to get enough to matched 4 some?

I am buying 20 of 2sk208 and 2n4547 each from mouser but am concerned I might need more.

Does anyone know?

 

[Paradox916]

if all you are after is a matched quad the matched quad of 2sk208 are $8 and you are already over that buying 20 and not sure if that’s enough.

 

[neiltheseal]

if all you are after is a matched quad the matched quad of 2sk208 are $8 and you are already over that buying 20 and not sure if that’s enough.

Not really. I'm in Australia. So for 2 matched quads plus shipping its about $55AUD. Plus it's something I'd like to try my hand at. And I can put those other jfets to use.

I'll add more jfets to the order in that case. Thanks.Might do an order of 50.

 

[Paradox916]

Not really. I'm in Australia. So for 2 matched quads plus shipping it’s about $55AUD.

damn that’s more than I would have thought … ok that’s valid,

 

[jimilee]

Smds are a little more consistent, in my experience. Get about ten or 15, whatever make sense for shipping purposes.

 

[neiltheseal]

Smds are a little more consistent, in my experience. Get about ten or 15, whatever make sense for shipping purposes.

Thanks for this!

 

[neiltheseal]

Did

2SK30A-GR Is what I used in SMD.

Did you match them or just use whatever?

 

[szukalski]

Did

Did you match them or just use whatever?

I started measuring them to match. After the 6th or 7th one in a row which was in range, I just assumed (ha) that the batch I got would be good enough to go blind with. It's an easy test, just a DMM and a few parts.

 

[neiltheseal]

I started measuring them to match. After the 6th or 7th one in a row which was in range, I just assumed (ha) that the batch I got would be good enough to go blind with. It's an easy test, just a DMM and a few parts.

Thanks. This makes me feel better. I tested about 15 2n5457s and they all measured pretty much the same. I assumed I was doing something wrong. Maybe not.

 

[Locrian99]

I bought some 5457’s from stompboxparts, thru hole awhile back and out of ten i got 2 sets of matched quads. Dont know if i just got stupid lucky or if they are still selling from the same
Batch.

 

[neiltheseal]

Thanks. This makes me feel better. I tested about 15 2n5457s and they all measured pretty much the same. I assumed I was doing something wrong. Maybe not.

I ended up using these jfets. Either I matched correctly or them being from the same batch were close enough. I now have a rad phaser.