Surface mount JFET's ?

[popov56]

After a batch of expensive JFETs proved almost useless, looking the business but turning out to be a load of crap I wonder if anyone has tried using surface mount ones?

Given that I bought some dodgy ones and that this situation can only get worse as the supply becomes scarcer I'm tempted by the MMBF5457 ones from Mouser;

http://uk.mouser.com/ProductDetail/Fairchild-Semiconductor/MMBF5457/?qs=sGAEpiMZZMvplms98TlKYyI%252bsdYAyN1N0Humk89lJi4%3d

........ as the unit price if you buy 100 is very tempting.

Any ideas ?

Popov

[Luke51411]

I've done mmbf5457 on adapter boards I found shared on OSHpark https://oshpark.com/shared_projects/txwvqJL1
They seem to be more consistent than their through hole counterpart, I was able to get quite a few sets of 4 with matched vgsoff for phasers. Out of all 100 I ordered I think maybe 10 didn't fall within range to at least be a match of 2. Soldering isn't too bad once you get the hang of it, it is time consuming especially with having to add the legs.

[Travis]

My experience is pretty much the same as Luke. I got a bunch of the SMD J201s and adapter boards and they sound great. Haven't had any that haven't worked properly so far but they are time consuming to use

Sometimes paying $0.50 each for through-hole JFETs from a reliable source is more attractive to me than fussing with the adapter boards. They work great though

[IvIark]

Yes the SOT23 are definitely the future, and without doubt the better choice now for phasers based on their close matching, even for people with a stash of through hole JFETs.

Through hole resistors and caps will be available for a long time yet, and I expect it will only be a matter of time before someone in China makes a blank TO92 case with legs that you can clip or slide any SOT23 transistor into.

[Frank_NH]

I've seen this topic come up at the DIYStompboxes forum.  For me, personally, I think I can find enough through-hole components (including JFETs) to last me for as long as I need.

For J201s, there may still be enough supply left for any builds I may contemplate.  Recently, I found a source for J202s, which are a drop-in replacements for 2n5457s.  The ones I received were very consistent in terms of Vp and Idss.  

I have a process now which allows me to determine what Vp/Idss are required for a JFET to bias for a common source amplifier configuration (which you see in a lot of overdrives, distortions, and amp sims).  So no JFET need be considered "bad" - potentially, I might use an outlier for buffering, but unless it's really fried, I can use it.

If I were going to be manufacturing a lot of pedals, THEN I'd be worried about supply.  Maybe we can pool our resources and buy a JFET manufacturing plant in China...

[IvIark]

Yes I saw that thread and it made me have a quick check of my stash
I found I had 794 x 2N3904's and so for my own personal use with the odd pedal built for someone else but no real commercial interest at all, I will definitely be fine for the rest of my life.

But I think you have to look a bit further than that.  Unless some manufacturers have stocked up massively it means that there is only a short life left for commercial through hole effects.  Even those who have stocked up massively won't have enough to go on forever and will have to start looking at changing at some point in the not too distant future.

One concern is that when all the manufacturers move on to surface mount we will see a lot less tracing of new pedals.  I've already seen it often where people are loathe to de-solder surface mount parts to check values because of the extra difficulty in rebuilding.  Also it is a perfect opportunity for builders who are moving on to machine made SMD boards to add features to make them more awkward to trace.  It will be a lot more simple to hide the circuit with hidden tracks and layers than it currently is with a lot of builders using simple single layer through hole boards.

On top of that because of the extra space you get to cram things in, a lot of builders may elaborate on the circuits, going for something more complex because they suddenly aren't concerned about real estate any more.  If that ends up with a lot of new great sounding effects then it will be excellent, but we could end up with circuits unsuitable for DIY through hole builds.

The one saving grace for me though is that it is a couple of the well known transistor manufacturers who seem to be doing this whereas there is no mention of common transistors being at the end of their life from others.  You can still buy 500 x 2N3904's from eBay for less than £3 + postage and long may it continue.  One thing the Chinese manufacturers have always been good at is recognising a market and satisfying it, and I reckon if one or two niche audio markets still wants through hole components, then someone will be there to supply them.   Plus of course we can still buy 30 year old Russian germanium transistors by the thousand, and there is a whole new range of silicon bipolar transistors and JFETs to go at there in the future

[jalmonsalmon]

I think you can use these pin headers instead of wires to save alot of time if you have a lot of smd's to convert instead of using wires or leads for the pins...
http://www.taydaelectronics.com/connectors-sockets/pin-headers/40-pin-2-54-mm-single-row-pin-header-strip.html