Select JRC4558D IC chips?

[Bill Moore]

A lot of interest a while back on the SGF, for the new OPA2134PA op amp chips in the Peavey Nashville 112. I had a "blackface" Bandit I was working on at the time with 4560 chips. Bought a set, and installed them, and they are quieter, there is no hiss at idle. I'm afraid my ears can't detect the subtle nuances that others may, but the amp does sound less "harsh".
I think jrfrond has it right, we are in a new age!

[J M Fahey]

Agree fully with above posts, Op Amps *have* changed, for the better ... but what still irks me is that these guys make a big fuss about "selecting" between the *same* kind chips, which, by the way, are still being made by the *same* company.
You can choose between a 70's design, bipolar input, 1V/s slew rate (or rise time, as they called it way back then), etc. etc. JRC4558, and a 2008 made ... JRC4558 , same specs!!!!
If at least, as was above suggested, they had "dropped the TL072 used in current models and went back to the sweeter sounding original 4558", well, that might be a sensible thing with audible results, but that was *not* the case.
So far as I know, the technique used must still be the same: photolitography, difussion, etching. *Maybe* they added glass passivation, if they didn't use it before, but anyway, such manufacturing changes might (should) improve the yield, or batch to batch consistency, or provide for a shorter manufacturing time, but not affect *sound*.
Oh well.

[dai h.]

Agree fully with above posts, Op Amps *have* changed, for the better ... but what still irks me is that these guys make a big fuss about "selecting" between the *same* kind chips, which, by the way, are still being made by the *same* company.
You can choose between a 70's design, bipolar input, 1V/s slew rate (or rise time, as they called it way back then), etc. etc. JRC4558, and a 2008 made ... JRC4558 , same specs!!!!
If at least, as was above suggested, they had "dropped the TL072 used in current models and went back to the sweeter sounding original 4558", well, that might be a sensible thing with audible results, but that was *not* the case.
So far as I know, the technique used must still be the same: photolitography, difussion, etching. *Maybe* they added glass passivation, if they didn't use it before, but anyway, such manufacturing changes might (should) improve the yield, or batch to batch consistency, or provide for a shorter manufacturing time, but not affect *sound*.
Oh well.

what's wrong with you didn't you read that fantastic article at Legendary Tones??

da olde JRC is DA SHIZNIT!!!

on a serious note though, I thought opamp swapping could change things (induce ringing) and might need things to be changed (more compensation or whatnot) to optimize the operation in a circuit. (I guess?) you can "get away with it" sometimes, but doing some opamp swapping, I've had one die after working for a long time, and another time I lost audio (that was more obvious that something was wrong and I was able to fix that without any sophisticated equip. by adding a series R directly at the outs--it was a dual op amp).

[selectortone]

I guess you can't blame Ibanez for wanting to get in on the 'bootique' pedal scam. It must be galling to see all these other guys charging big bucks for what was their circuit.

[dai h.]

yeah I think that is part of it. Landgraffs and such can go for hundreds(of $$$--the equivalent of in yen, anyway), even used(in japan), so makes sense they want to get some of that action. I'd like one like that with the case and mechanical switching but without the HW business and just a better quality PCB than the one in the original.

[Mark Hammer]

Again, I don't think they have any intention of making money directly off the illustrated point-to-point Tube Screamer, any more than Ford or Honda intend to make money from sales of their assorted high-end racing vehicles. They all use these "marquee" products to establish brand; as in "These other folks may play with our design, but WE are the 'real thing' ".

[dai h.]

apparently production is very limited （several a month) so that may be the case (though apparently they are selling). As a "marquee" product doesn't seem too outlandish though (from vague recollections about super expensive versions of jewelry and stuff such as diamond encrusted brassieres, etc.), relatively speaking.

[Jazz P Bass]

1970 & 1980 opamps do not, in any way compare to ic's made in the 1990-2010 range.
Slew rate, rise time, ring, overshoot parameters have all gotten better.
Case in point.
I had a Tube Works TS252 come in with a bad preamp tube (which just so happened to take out the 4558 IC).
Replaced the tube, put in a new IC.
The customer hated it.
Changed this, changed that, selected a "medium" gain 12AX7 (selected).
Hated it.
Pulled the 4558 from the reverb circuit & stuck it in the preamp.
Loved it.

My Bad!
It was a Tube Works TD752 & it had TL072 IC,s in it.
At any rate the new ones did not cut it in the distortion circuit.

[David Schwab]

who knew? More capacitance leads to a brightening effect.

Wow... they actually said that too! But then look at some of Gibson's add copy on their website.

[David Schwab]

n a serious note though, I thought opamp swapping could change things (induce ringing) and might need things to be changed (more compensation or whatnot) to optimize the operation in a circuit. (I guess?) you can "get away with it" sometimes, but doing some opamp swapping, I've had one die after working for a long time, and another time I lost audio (that was more obvious that something was wrong and I was able to fix that without any sophisticated equip. by adding a series R directly at the outs--it was a dual op amp).

Some op amps ned external compensation, while others are internally compensated, and are swappable.