Orange Squeezer parts substitutions

[black mariah]

Since I'm impatient and it'll be a couple of days before my breadboard arrives I must ask this...

Squeezer with TL071 and J201's... will it work or not? If so, will it sound good? I have those, but not the 2N5457's and JRC4558. Better to ask than to waste parts.

[the_ms]

I tried a TL071 and a LF356. With one of those, the Squeezer did not work correctly because of the high bandwidth of the OPAs. The circuit produced non audible high frequency oscillations, which prevented the circuit from proper function. In this desperation, I tried an old 741 and it worked. I can't say anything about the influence of the choice of the OPA on the sound. I am content with my result.

[oldrocker]

I used a TL082 dual opamp and MPF102's in mine.  I'm not sure what changes you need to make to use a single opamp like a 741.  You may socket the FET's so you can try different ones and the same with the opamp.  I would think 201's will work but I don't know what the results would be.  Pin layouts for the single and dual opamps are different so keep that in mind.  Since you're really only using half of the dual opamp anyway check the datasheets for correct pinouts.

[black mariah]

*GRUMBLE*

I meant TL072. In fact, I typed 1 again just then. Stupid numbers. Why can't we just name them like people?

Q1: Kevin
Q2: Kevin
Q3: Edgar
IC: Henry

Way less confusing.

[markm]

"Dickie Diode"!
Sounds like a surf-guitar legend from the early '60s!! 

[black mariah]

"Dickie Diode"!
Sounds like a surf-guitar legend from the early '60s!! 

Wasn't he married to a tranny named Joan?

[the_ms]

I used a TL082 dual opamp and MPF102's in mine.  I'm not sure what changes you need to make to use a single opamp like a 741.  You may socket the FET's so you can try different ones and the same with the opamp.  I would think 201's will work but I don't know what the results would be.  Pin layouts for the single and dual opamps are different so keep that in mind.  Since you're really only using half of the dual opamp anyway check the datasheets for correct pinouts.

I should say that I usually use stripboards instead of PCBs. So, it isn't a problem to choose an IC with another layout, as long as I do the choice before I start soldering

[mac]

Right now I have a 741 and BF245A in the breadboard and it sounds ok.

BTW, I put pots and trimmers everywhere. Making R11 (GGG schem) a 50k pot and varying C7 or R12 is a nice mod.

mac

[Mark Hammer]

I can't think of a single reason why a TL071 would NOT work in there.

As for the J201, keep in mind that you're using the FET as a voltage-controlled resistor, forming one half of a voltage-divider in tandem with the 82k input resistor.  The amount of compression produced will depend on how much attenuation of the signal occurs by this automatic volume-pot, and that in turn will depend on what the actual max and min resistance of the FET is.  The J201 may "work", ultimately, but you may need to change the value of the 82k resistor to make the pair work in a desirable manner.

If the J201's resistance range is fairly low then you may want to reduce the 82k resistor to 68k, 47k or maybe even 39k to get a reasonable range of automatic adjustment.  Conversely, if the resistance range of the J201 ends up being fairly high, then you might not get audible compression unless the 82k resistor gets pumped up to 100k, 120k, or maybe even 180k or 220k.

The basic rule of thumb to keep in mind is that if the FET resistance range is equal to or much lower than the input resistor value, it will take very large changes in FET resistance to produce noticeable attenuation changes.  A FET/resistor combination that produces only 5% reduction in level in response to transients will not prove to be a very pleasing compressor.

Again, I'm not saying the J201 will NOT be a drop-in replacement.  I'm just trying to provide a strategy for adapting the circuit in case it proves not to be a precise replacement for a 2N5457.  My sense is that the original input resistor value was chosen specifically to match the parameters of the FET.

[mac]

Mark, thanks for the info. I tired with bf245A, but I'm going to try 2sk246 which are more similar to the 2n5457, at least in the datasheet.
Going to put a 250K pot instead of the 82K to see what happens.
Btw, I played with the 2.4K, pretty much like the 10k pot to set the proper bias of the fets.

mac

[the_ms]

I can't think of a single reason why a TL071 would NOT work in there.

Am I really the only one who built an Orange Squeezer that oscillates somewhere in the high frequency range using a TL071? 

At that time, I found a hint in the deep jungle of the web (I can't remember where it was and I didn't find it anymore), that the high bandwith of the TL071 increases the high frequency gain so that the gain and phase conditions are fullfilled for an oscillator.

I could solve the problem using a slower 741 instead of the TL071. The oscillation did not appear and the circuit worked as it should.

[black mariah]

Thanks for the info, Mark. When I perf this thing I'll throw a trimpot on there in place of the 82k resistor. I have an LM741 laying around here and I always socket IC's so I'll try both that and the TL071.

Fun.

[Mark Hammer]

I can't think of a single reason why a TL071 would NOT work in there.

Am I really the only one who built an Orange Squeezer that oscillates somewhere in the high frequency range using a TL071? 

At that time, I found a hint in the deep jungle of the web (I can't remember where it was and I didn't find it anymore), that the high bandwith of the TL071 increases the high frequency gain so that the gain and phase conditions are fullfilled for an oscillator.

I could solve the problem using a slower 741 instead of the TL071. The oscillation did not appear and the circuit worked as it should.

Or, just stick a cap in the feedback loop of the op-amp to keep it stable at high frequencies.  47pf in tandem with 220k gives you a rolloff starting around 15.4khz, which is high enough to keep all the sparkle but low enough to make the chip behave.

[LoudGreg]

I can't think of a single reason why a TL071 would NOT work in there.

Am I really the only one who built an Orange Squeezer that oscillates somewhere in the high frequency range using a TL071? 

At that time, I found a hint in the deep jungle of the web (I can't remember where it was and I didn't find it anymore), that the high bandwith of the TL071 increases the high frequency gain so that the gain and phase conditions are fullfilled for an oscillator.

I could solve the problem using a slower 741 instead of the TL071. The oscillation did not appear and the circuit worked as it should.

I (very stupidly) used the wrong power supply for my GGG Orange Squeezer and I now have this Oscillation (High B Note) problem. 

JD was fantastic and sent me a new IC and transistors. I socketed the IC and Transistors and the pedel works Great but only when the a 9V battery is used. When I hook up my adaptor (the correct one) I get the Oscillation sound again. I did put a filter on the power supply but I still get this Oscillation only when the adaptor is used.

Any ideas as to what could be causing this.  It's killing me that this is my first build, and it worked beyond my hopes. Great compressor and a fantastics overdrive/Booster. But now I screwed it up somehow. I'd really like to get it back to where it was. 

[Northwave]

Might be to late, but here goes. (I'm actually looking into this tread because I want to build this comp and don't have any 2N5457 at hand)
The TL07/6/8 series can be prone to ocilation at times. If driving highly capasitive loads, a series resistor in the output might help.
But this is unlikely to be your problem the_ms, or at least not all of it. Since oscillation is in the audible range, feedback cap is not a good idea.

I would try the following things:
- Decouple your supply with a ceramic capasitor (as close to the OP as possible)
- Put in a small seriesresistor in the powersupply-lead (some x0 ohms should suffice)
- Lower the values of your bias voltage divider, and use a single 100k resistor to supply bias from the midpoint
(midpoint should be decoupled by a parallel 10-100uF cap)

Hope this might be helpful!


EDIT: Mark Hammer. Is there anyway to tell which FET's might be considered more (or less) ideal substitutions by the datasheets?

[markm]

I have heard and read of people using MPF102's successfully in the O/S but in general I think the 2N5457 is better.
Just an opinion. 

[R.G.]

The OS will respond best to JFETs like the 2N5485, 2N5952, 2SK30, 2SK118, and other JFETs with Vgsoff of about 2-5V.

MPS102s have only a maximum spec of 0 to 8V Vgsoff. Some perfectly good ones will not work in the circuit.

J201 is on the other end. It's a very low Idss JFET with Vgsoff of only 0-0.5V. That leaves hardly any signal room.

[oldrocker]

Thanks R.G.  I just replaced the MPF102's with a couple 5952's and it sounds good.  Nice compression now.

[LoudGreg]

Might be to late, but here goes. (I'm actually looking into this tread because I want to build this comp and don't have any 2N5457 at hand)
The TL07/6/8 series can be prone to ocilation at times. If driving highly capasitive loads, a series resistor in the output might help.
But this is unlikely to be your problem the_ms, or at least not all of it. Since oscillation is in the audible range, feedback cap is not a good idea.

I would try the following things:
- Decouple your supply with a ceramic capasitor (as close to the OP as possible)
- Put in a small seriesresistor in the powersupply-lead (some x0 ohms should suffice)
- Lower the values of your bias voltage divider, and use a single 100k resistor to supply bias from the midpoint
(midpoint should be decoupled by a parallel 10-100uF cap)

Hope this might be helpful!

Thanks, I was just going over this again.

? Can you put this more into -color by numbers- lanuage  I'm not too sure what you mean by"Decouple the power supply". 

[Northwave]

Sorry, my english isn't the best. (BTW - today is my countrys constitutional day! Norway )

Following is a schematics of your OPAMP stage, with additions/modifications that you might need to ensure proper stability.
Not all things may be needed, so do one step and try the box again. Try these things in the following order:
(none of these values are critical, and can be something else in the same magnitude)
1 - Add the small ceramic decoupling cap C1. Preferably soldered right to each of your supply pins, or close to the OP on the board
2 - Add the series resistor R1, and electrolyte decoupling cap C2. This can be located where your powersupplyleads connects to the board, for instance
3 - (probably, and hopefully not needed)
Replace the original bias divider (390k/470k resistors) with R2, R3, C2 and R4 (sry typo on pic says R3..)

EDIT - needed to find a decent picturehosting-site