The Steel Guitar Forum

Is an opa2134 the same as an opa2134PA

What´s an opa?

Oh,I see.Thanks.But what is it for and what does it do ? Thank you again.

That chip, like many others like it, has two operational amplifiers. Peavey uses them in the EQ stages of the preamp. If you look them up on Wikipedia (or your preferred knowledge base), the op amp is kinda clever.

I believe the "PA" at the end of the op-amp designation is how Texas Instruments refers to the dual in-line package (DIP) format, as opposed to their surface mount format, "UA".

If you are looking to get an OPA2134 IC to drop into a DIP socket to replace another op-amp with the same pinout, you want the OPA2134PA IC.

Could anyone describe in what ways a 2134 sounds better than a 2604?

2604's were a huge upgrade tonally compared to the 744's (???, can't recall for sure) that are in almost everything....I've never heard a 2134, but they must be phenomenal chips to sound better than a 2604.

I do not have both devices to listen to, but the specification differences (per TI datasheets) show that the 2134 has 12db less harmonic distortion and 3db less noise, though the 2604 slews faster and farther, 25 volts per microsecond up to 23 volts (2134=20 & 17). If anyone has specific double-blind sound testing comparisons, I'd love to see (hear) it!

I've tried both the 2604 and the 2134. The 2604, in a Nashville 112, turned it "sterile" and more on the treble side. The 2134's are a keeper and just clean up the sound in the Nashville 112. In a Nashville 1000, it substantially improves it and takes away the mid honk of the "digital" power amp section and sort of makes it sound like a Nashville 112 that has a conventional analog power amp section. Both the Nashville 1000 and Nashville 112 use the identical preamp section and preamp board.

From what I read, the 2604 is basically a general purpose op-amp, where the 2134 is more for audio applications (although it too can be considered a general purpose op amp). Many "audiophile" headphone amps use 2134's.

Peavey does not use these Op Amps in stock amps. The 2604 in used in some "mod kits" such as for the Nashville 400.

I did a test recently on a Nashville 112 I had in for repair. Just replacing the first (input preamp) chip with a 2134 made a big difference.

I have 2134's in my Nashville 112.

I put 2134's in my Nashville 400 per Ken Fox's recommendation. I had previously had him mod my amp, which not only included the opamp's being changed out (maybe to 2604 - but not sure), but some resistors, capacitors and maybe a diode or two. I noticed the same things Jack did. My amp was already a great sounding amp, but the new chips made it a little warmer sounding (to my ears).

Vewy Intewesting….now has anyone tried some opamps that should REALLY give the OPA2134 a run for its money---such as an OPA627B or an ADA4627-1B? These both have better specs, but do they SOUND better?

Well, Steven, it looks like it's up to you to pick up a few of these super op-amps and do some testing. I'd say most of us are very happy with the 2134's. But maybe you can convince us otherwise.

Ken Fox has done all the initial testing with the op-amps. I don't know if Ken has looked at those two that were listed.

I am playing around with a 84 Nashville 400 with the 2134 chips in it. If I replaced the 1502-4 speaker with a 1501-4 what change could I expect ? I'm sure some of you guys have tried that.
No other mod to the amp. Just the chips.

Bill. I have an 84 NV400 with a 1502-4 in it. I also had one with a 1501-4 in it. The 1502 is a bass speaker and is much warmer and less harsh in the high end than the 1501, in my opinion, but can get piercing highs if you want them. When I first got my NV400 in 84, I had a JBL K130 that I tried in it, and put the 1502 back in very quickly.

The older (original) model Nashville 400's were designed ("voiced" as Mike Brown says) for the 1502 speaker. The change to the 1501 speaker was the issue and the reason for the Lemay and later Peavey mod kits for the Nashville 400 and ultimately the production change to incorporate the "mod" into production. The 1501 speaker has a different frequency response curve and the tone control circuitry in the later Nashville 400's had to be modified to recover the proper "Voicing".

Thus if you put a 1501 speaker in an older Nashville 400 it will have all highs and lose most of the lows.

As the older Session 500 also came with the 1502, I would suspect the same thing would happen to that if the 1502 was replaced with a 1501.

Thanks, Jack, for outlining the fundamental differences between early and later NV400's. I have a couple of both and, while knowing that there were differences, I didn't know specifically what those were. Now I do.

Thanks again.

Took the 1502 out and the foam in the magnet had melted between the coil and magnet slot. Cleaned her all up and the old amp sounds pretty good and I'm not a Peavey fan.
I have owned 4 Nashville's in the past. Some moded but the older , chrome corner, amps sound best. I changed the chips in this one but if it were mine I would do nothing else.
Thanks for the reply's on the speaker change.

A recent "blind" test was done on one of the audio forums to compare the sound of various opamps. The author posted sound clips of material run through a circuit that attenuated and amplified the signal several times in order to accentuate the differences, and then asked the members to post which one they thought sounded the best, naming them only by color. A good attempt at being fair, at least. Not totally scientific by any means, and a fairly small sample lot. At the end of a month or so, he revealed the opamps and the voting results:
the LM4562 was the clear winner, with the OPA2134 second. The worst were the 741 and the 4558; the TL072 was in the middle. Now this is listening to mixed music, NOT steel guitars. But interesting food for thought.

LM4562's are pretty astounding opamps. Definitely in a class above the OPA2134 when it comes to real high end pro audio use. I use them in a few of my critical, audiophile/mastering gear circuits. They have an amazingly clear, clean, 3-dimensional, and highly-detailed resolution to them. But I've never tried them for steel guitar amplification, so it's nice to hear that they perform well there too. Sometimes "better" isn't best for guitar tones, but in this case it appears that these may well be.

One warning though. Some of these high end, high-speed audio opamps require special circuit stabilization so they don't oscillate at radio frequency. You can't hear the oscillation, but they can get VERY hot and make the amp sound terrible or possibly not even work correctly. The dummy's method of seeing if an opamp is stable is to put your finger on it after a 10 seconds and then if it's not hot, then check again in 2 minutes. If it's really warm or too hot to touch, you know it's oscillating. Just be careful when "rolling" opamps in a circuit not designed around a particular opamp. The OPA2134 tends to be stable in most any audio circuit you'll try. It's the higher end ones that can be finicky.

Brad

I replaced the ics in my Bandit with the OPA2134, and really liked the difference. I have also used them in several pedals with great results.

Just wanted to let everyone know my website is open again for chip sales. Been down for a while due to the divorce and my being gone for a while.

Thanks again for all that have used my kits!

I did the entire peavey tone mod on a nv 400 which included 6 of the 2604 chips. It cleaned everything up but I ABSOLUTELY could not tame the treble. After reading this thread I got the BB opa2134pa chips and the difference is night and day. This amp now has great tone. My vote is for the 2134 chips. JM