Quick question: (I have searched and found mostly old comments but:)
For GGG Orange Squeezer calls for a couple of 2N5457 JFET's.  I do have some
2N5458, and a few J112, are these worth trying or should I just order some 5457's ?
Thanks

2N5457 and 2N5458 specs are more close than each individual type JFET spread..

Meaning, don't even bother for particular JFET type..
(although, Rob Strand & Mark Hammer are more apposite persons due to their involvement in particular effect improvement..)

Yeah, I would just go with the 2N5458 that you have on hand, and it should be okay.

The adjustment of the trimpot can be tricky even with a perfect spec jfet, and it may take a few tweaks before it compresses correctly. I cannot remember what voltage I used when I made a clone of it or I would post that for you.

Best regards, Jack

Quote from: amz-fx on January 27, 2022, 02:55:05 PM
I made a clone of it

(my bad for not mentioning you, Jack..)

I've traced (one of) the original PCB(s) of a '70s Armstrong OS (from photos, sadly not from having one to hand), and it was visually evident that the JFETs were either SGD or DGS pinouts. I've never encountered a 5457 with that pinout, so it's possible and/or likely that at least some of the original circuits used a different, non-5457, JFET. I got mine to work just fine on breadboard with both BF244As and BF244Bs, and those overlap similarly with 5457s and 5458s, so I'm guessing your 5458s will do nicely. I think I even got a pair of J113s to function during one experiment, but I seem to recall it was much harder to tweak the trimpot, much as Jack describes. As ever with JFETs, plug 'n' play — and pray. 

You can use 2N5458 for Q1. Other things also operate, but the effects may change slightly. "gm" parameter seem to play a large.(not "IDSS" or "Vgs")
Q2 can select many stocks. It doesn't have to be 2N5457, 5458.
Set the trimmer so that TP is the same as Vgs of Q1.
Dan Armstrong seems to have swapped the D<->S of Q1, but I haven't checked that directly.

Add edit:
If Vgs is too large, it may not be possible to limit a very large signal input. (Vgs>3.0V?)

Quote from: m4268588 on January 27, 2022, 10:12:11 PM
Dan Armstrong seems to have swapped the D<->S of Q1, but I haven't checked that directly.

In theory, it  doesn't mind 'cause Drain and Source are fully interchangeable..

I have used 2N5458 in My Orange Squeezer and works just perfect, Even better than 2N5457.

To set the bias I used the same than GGG doc (D1 2.6V D2 4.0V) the sweet point.

I tried some ICs and the LF353p worked the best for me, no distortion and great sound definition.

Advice: Use sockets for Jfets and IC.

Saludos.

Wow, being new at these op amp circuits, I see a big difference in these two schematics in the op amp section,  both are the same 4558.
Comments... ie pins 3,6 ect  guess I am confused , thanks for help in siferin

GGG




RGK

Quote from: Phend on January 28, 2022, 06:29:42 PMWow, being new at these op amp circuits, I see a big difference in these two schematics in the op amp section,  both are the same 4558. Comments... ie pins 3,6 ect 

Looks same to me. The 4558 is a *dual* opamp. Like a 2-pack of beer. The circuit only needs one opamp, but some years the 4558 was cheaper than contemporary single opamps. If you only need one beer you can drink either one. One designer picked the 321 opamp. The other picked the 567 opamp, and notated that the 321 opamp should be tied-up out of trouble.

Thanks Paul,  well put, described in a way I can understand,  will take a close look at the pin connections 

but don't be grounding the (+) input like it shows, take it to some V/2-ish reference.

Looking at the pinout for 4558, I will use pins 1 2 3 4 8, and 5 6 7 will not be used ie no connection.
Only 4 will go to ground. In other words, use RGK circuit as shown.  Thanks m4268588 and Mr. Keen.
Please correct me if this is wrong.
..
I see GGG (which is using the other half) made other connections , ie all pins are used.

all pins must be used on a dual opamp, unless you want to invoke strange things happening. it's just that you can't tie (most) opamp inputs to ground without upsetting them, invoking the strange things, undocumented behaviour. so, tie the input instead to some voltage, like V/2. this is allowed.

QuoteLooks same to me. The 4558 is a *dual* opamp. Like a 2-pack of beer.

I see GGG used the Right Half (B) and RGK used the Left Half (A)
For instance, when using the Right Half as shown in the GGG circuit, do pins 1 2 3 need to be connected as shown.?

It's more wise to replace GND with Vbias / Vref/ V_CC/2..

Of course, GND stands for bipolar supply..

Quotebut don't be grounding the (+) input like it shows, take it to some V/2-ish reference.

Like duck_arse says

Dan Armstrong seems to leave 5, 6, 7 pins and left. But, It's not good.
Please "improve" them unless you are building a replica.

Correct:

^ thanks, you meant RGK I believe, but will do, getting clearer, building on a bb so easy to experiment.

why not use a single opamp like TL071 or LF351? or a 741, and I don't know the JRC single number. 5532? the extra pins problem goes away, then.