Substituting 2n5485 JFET?

[Shannon]

Hey guys. I'm building (well, more to the point - planning to build :p) the tonepad MXR Noise Gate. I just received the PCB from them today and I'm putting together a list of parts from Farnell. The only part I can't find though is the 2n5485 JFET. Does anyone know of a suitable substitute for it?

Here's Farnell's JEFT catalogue if anyone wants to look through whats available: http://au.farnell.com/jsp/search2/browse.jsp?N=500001+1000875

I've looked at the 2n5485 datasheet, but I'm not exactly sure what I'm looking for with transistors.

Any help'd be great. Thanks.

[Horace]

RS Components Australia have them, but unfortunately I think you have a minimum order of 25 of them at 50 cents each.

[d95err]

I would really recommend using a website dedicated to DIY instead. I've had great results with, for example: www.smallbearelec.com, www.musikding.de, www.banzaieffects.com.

They are all a lot cheaper than Farnell, and they will have everything you need in stock.

[Horace]

and a MPF106 might be a close enough substitute

[Shannon]

I would really recommend using a website dedicated to DIY instead. I've had great results with, for example: www.smallbearelec.com, www.musikding.de, www.banzaieffects.com.

They are all a lot cheaper than Farnell, and they will have everything you need in stock.

The only problem is I live in Australia and don't want to wait forever to receive simple parts like transistors.

RS Components Australia have them, but unfortunately I think you have a minimum order of 25 of them at 50 cents each.

Yeah, which runs out being $12.50 and I only need 1.

[Horace]

MPF106's should be available at any Jaycars or Dick Smiths

[Horace]

http://www.jaycar.com.au/productResults.asp?FORM=KEYWORD

[Horace]

sorry..... http://www.jaycar.com.au/productResults.asp?whichpage=3&pagesize=10&keywords=&CATID=33&SUBCATID=447&form=CAT&SPECIAL=&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=

[Shannon]

I might go down to DSE and see if I can find a few. Although last time I went there half of their capacitors and resistors were in the wrong tray and I ended up with a handful of parts I didn't need...

[zjokka]

did you try plugging in any jfet you do have available?

Yeah, which runs out being $12.50 and I only need 1.

you never just need 1, it might just be a bad one. I was sceptical about overseas shipping too, so I wasn't thinking paying 0.70 EUR ($0.90 or so) per jfet. Lately I've seen the light and ordered a bag of 100 jfets for $5.95. shipping transistors costs almost nothing, it's like the weight of a letter. For the cost of a letter you cannot drive to an electronics store or three to look for that one component

Just get the best price on the net and order a handful. Buying just what you need at the moment will be more expensive in the end. Some good jfets always come in handy.

succes!

[R.G.]

You're looking for a JFET with Vgsoff of 0.5 to 4.0V.

Suitable devices are 2N5485, 2N5292, 2SK30, 2SK118, 2SK117.

I think.

[stobiepole]

If memory serves me correctly...I picked up some MPSA16's at Jaycar and they were labelled 2n5485...so they sell them interchangeably. Give one a go and you'll surely be fine.

Chris

[Shannon]

Hmm, I've found a site called Futurlec that stocks a better range of transistors and FETs. Well, they have the 2n5484 and 2n5486, but I'm assuming they're not much different to the 5485 considering all 3 are on the same datasheet...

They also have bulk packs of transistors and resistors and so on. And they have an Australian store to dispatch from.

[stobiepole]

Oops, I meant MPF106...2n5485 are sold at Jaycar as MPF106. That's what you need.

Futurlec stuff actually comes from Thailand. I've currently got an order with them that was supposed to be here three weeks ago - they're cheap but not terribly efficient.

Chris

[zjokka]

You're looking for a JFET with Vgsoff of 0.5 to 4.0V.
Suitable devices are 2N5485, 2N5292, 2SK30, 2SK118, 2SK117.
I think.

Is that a determining factor for a JFET in general or for a noise gate in particular?
When I started out stompboxing, I was very focussed on part numbers. After some more reading, I decided to discard that and just focus on the type (npn pnp/ mosfet jfet), and it sonic characteristics.

But here, in a noise gate, the fet has a switching function, no?
Not much sound characteristic of any component will come through in a noise gate.

zj

[R.G.]

For a switch, you want two things: low Rdson and a Vgsoff that you can comfortably feed to the device being switched.

The JFETs I mentioned are good for effects use for variable resistors and sound switches because they have acceptably low Rdson and a Vgsoff of 5V or lower. This is important because to switch a JFET off you have to move its gate below (for an N-channel) Vgsoff relative to the source. We do this for normal negative ground circuits by biasing the source up to half of the 9V supply and pulling the gate to ground. So these part numbers are good starting points for JFETs in a 9V environment. There are other devices with even smaller Vgson that may have higher gain that may be better for amplifiers.

It's fine to ignore type numbers in many circumstances; I'm always preaching at people to largely ignore part numbers for germanium devices and NPN small signal transistors.  However, this advice is based on two different facts: (1) germanium varies so much that you have to test anyway and (2) NPN small signal devices almost always just need to have enough gain, which almost all modern devices do.

JFETs have big variations, too, but they do have guaranteed min and max values on the datasheet. And it happens that in this case, knowing what the maximum value of Vgsoff  may be is important. Some JFETs may have Vgsoff of 10V or more, meaning you can NEVER turn them fully off if you only have 9V to back bias the gate. So the maximum and minimum values of Vgsoff matter.

In a noise gate, not only the switching characteristic matters, but also the range of values through which Rdson varies by Vgs. This matters because you want the turn on/off to be soft, not abrupt, as this is less noticeable in the sound. So the sonic characteristics do matter.

The devil is always in the details. You not only have to know what matters, you have to know what matters in which situations.

[jfrabat]

Hi, guys.  Sorry for reviving a very old thread!  I am having the same problem.  I am also building a MXR Noise Gate from a Tonepad board, and cannot find the 2N5485.  Keep in mind that I live in Costa Rica, so ordering a single transistor from the US will be $$$!  (Not to mention it will probably get here by February if I am lucky!)  I have in stock the following JFETs:

2N5457
NTE457
NTE451

Will any of these work?  That's about all I can find locally...

[highwater]

The NTE451 is the closest match of those. VGS(off) range is specified the same as the 2n5485, and the IDSS range has the same minimum and a higher maximum (which will be either good or irrelevant).

The other two will probably work, but might have issues if the specific transistors are at the upper end of the VGS(off) range.

And, of course, make sure the pinout matches.

[jfrabat]

The NTE451 is the closest match of those. VGS(off) range is specified the same as the 2n5485, and the IDSS range has the same minimum and a higher maximum (which will be either good or irrelevant).

And, of course, make sure the pinout matches.

I think I will go with that one, as even the pinout matches...

[alfafalfa]

I saw a different schem that used quite different transistors.

https://ibb.co/hMLhnw

Couldn't it be a 5458  spelled wrong??