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  #1  
Old 07-01-2011, 11:56 AM
vbf vbf is offline
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OP-AMP question

I'm familiar enough with dirt pedals to know that some have socketed op-amps. What are the most common op-amps for dirt and are they available at radio shack, etc? Are they like Eproms that need to be programmed or are they ready to go stock? Thanks!
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Old 07-01-2011, 12:02 PM
this1smyne this1smyne is offline
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they are ready to go stock. just make sure you compare the pinouts. i know there are some 'sets' on ebay and smallbear and stuff that you get a whole variety of op amps to swap in and out. a few have different pin readouts, but anything in the TS camp you can swap the chip. differences are subtle, but sometimes in different rigs you find a gem of an op amp. i think its mostly stacking/amp dependent, a lot of the 'comparison' videos i've heard (even the good quality ones) are little to no audible difference.... if you can't hear it listening to it than you're not likely to notice a difference on a stage setting.
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  #3  
Old 07-01-2011, 12:05 PM
jonathansuhr jonathansuhr is online now
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It also depends on the pedal. Some pedals utilize single opamps (DOD 250 and such) and some use dual opamps (Tubescreamers and such). They won't be interchangeable between types.

That said, I really like Burr Brown chips for either type. Definitely OPA2134 for Tubescreamer type pedals.
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Old 07-01-2011, 12:47 PM
cj_wattage cj_wattage is offline
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Quote:
Originally Posted by vbf View Post
What are the most common op-amps for dirt and are they available at radio shack, etc?
You can get a limited selection of both single and dual op amps at Radio Shack.

Most common seem to be 4558, TL072/82, NE5532, and the OP series that Suhr mentioned. Singles are usually LM741 or TL081/71/61 for the Dist+ and Hotcake type circuits, and LM301 or OP077 for Rats.
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Old 07-01-2011, 05:23 PM
vbf vbf is offline
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You guys are the best..thanks!!!!
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Old 07-01-2011, 05:39 PM
Aran Aran is offline
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Quote:
Originally Posted by jonathansuhr View Post
It also depends on the pedal. Some pedals utilize single opamps (DOD 250 and such) and some use dual opamps (Tubescreamers and such). They won't be interchangeable between types.

That said, I really like Burr Brown chips for either type. Definitely OPA2134 for Tubescreamer type pedals.
Magic installed in a Boiling Point. I will never touch the 4558 again.
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Old 07-01-2011, 07:14 PM
Ramblin390 Ramblin390 is offline
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Old 07-01-2011, 07:53 PM
WailinGuy WailinGuy is offline
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I've done a lot of experimenting swapping dual op amps (pin compatible with JRC4558) in various OD pedals. In my experience, some circuits are more sensitive to op amp changes than others. Some pedals really can be made to sound quite different by swapping the op amp.

I'm also a big fan of the Burr-Brown op amps. Besides OPA2134, another good one to try is OPA2604. That's what I have in my Barber LTD SR (stock chip is JRC4558), and I think it gives it an even more clear and dynamic crunch/overdrive.

Another good op amp to try in OD pedals, which is inexpensive, is the LM1458 (and very similar Texas Instruments MC1458). I almost always prefer it to the JRC4558 - it seems to give a more natural tone; the JRC4558 sounds nasal and mid-humpy in comparison. (I've come to the conclusion that there's nothing really special about the JRC4558; much better quality dual op amps have been developed since 1980.)
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  #9  
Old 07-02-2011, 06:26 AM
vbf vbf is offline
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Great info guys, thanks! So do I count the number of pins and the chip's orientation in the socket and simply remove and replace?
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Old 07-02-2011, 06:50 AM
chervokas chervokas is offline
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When it comes to op amp swapping I think it's all a matter of the designer's original intent. I've done a lot of swapping in both guitar pedals and hifi electronics--say CD players. Often, in the latter case, the initial choice to use one opamp vs another was made to keep down production costs and an aftermarket switch to another chip offers a clear improvement.

However, my experience with guitar effects pedals is that designers typically have designed around a particular chip, and a chip switch -- whose effects may be larger or smaller depending on the nature of the design -- just takes me away from the sound of the pedal that I liked in the first place. I have found this to be so particularly in the case of going from a JRC4558 to a more high fidelity kind of chip. I'm not looking for hifi out of my distortion, that seems like a contradiction.

By all means experiment. It's fun and interesting and a learning experience and it's nice when builders, like Barber, socket the op amps on their boards. But in the end I've come around to picking pedals I like the sound of and leaving well enough alone, especially in these days of boutique builders using quality parts. But sometimes an archaic op amp -- like the 741 in the old DOD 250 is just the part you need for the pedal's characteristic raunchy sound.

Certainly there are pedals that benefit from modifiction (I have a Butler Tube Works era OD and I had to swap from a 12ax7 to a 12au7 and rehouse the transformer -- moving it from inside the enclosure to a wall wart enclosure to eliminate hum that make the pedal unusable -- now I love that OD). Some older or budget pedals could probably be improved with cap upgrades. But for myself, I've set aside op amp swapping in favor of swaping out devices entirely for ones whose sound I prefer.
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Old 07-02-2011, 09:39 AM
WailinGuy WailinGuy is offline
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Quote:
However, my experience with guitar effects pedals is that designers typically have designed around a particular chip, and a chip switch -- whose effects may be larger or smaller depending on the nature of the design -- just takes me away from the sound of the pedal that I liked in the first place. I have found this to be so particularly in the case of going from a JRC4558 to a more high fidelity kind of chip. I'm not looking for hifi out of my distortion, that seems like a contradiction.
Again, it depends upon the pedal - some just seem to sound best with the stock chip - but, in some cases, switching to a higher quality, "more high fidelity" op amp in an OD pedal doesn't necessarily make the distortion sound more hi-fi. Sometimes it can make the distortion sound more natural, or refined, or give harmonics that are closer (but never exactly, of course) to what a preamp tube might generate. This was the case with my Barber LTD SR. It sounded nice with the stock RC4558, but the distortion character seemed slightly rough, with some congestion in the low midrange I couldn't dial out. Swapping it for an LM1458 improved things quite a bit, and then going to a Burr-Brown OPA2604 made even more difference. The overall tone is now even more true to the original guitar signal, and the added harmonics are very pleasing and sound very "connected" to the fundamentals, like with a good tube amp.

So, for anyone who is so inclined, I would encourage you to experiment. Most dual op amps are very inexpensive, so it doesn't cost much. I do recommend using a chip puller tool (Radio Shack might still sell them), which can really help in removing chips straight up off of their sockets, without bending the pins. Much easier than using fingers, pliers or a small screwdriver.
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Old 07-02-2011, 10:35 AM
50MkII 50MkII is offline
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Might be a side note and not meant to sidetrack, but one also needs to account for the voltage you are running the chip(s) at in a given circuit so as to not fry the pedal. I am wondering if there is any source that would help us determine what not to put in a particular circuit. I know I was advised by Nick at NC03 to not use a particular chip in his Pure Drive big box version. Time to take notes...again.
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Old 07-02-2011, 10:59 AM
oldhousescott oldhousescott is offline
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As johnathansuhr and CJ both pointed out, there are single and dual opamps that both come in the same package -- in our case 8 pin DIP, 4 pins on a side -- but are NOT interchangeable. Make sure you sub like for like, single for single, and dual for dual (although most of what we encounter are duals). Also make sure when you go to order that you don't get surface mount instead of DIP. Some use the same part number except for the last few alpha-numeric characters to designate package type.
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Old 07-02-2011, 11:11 AM
mmolteratx mmolteratx is offline
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I prefer Analog Devices stuff to Burr Brown. AD712 is awesome, as is the OP275 as far as dual op amps go. For single op amps, I like the AD797 and the Intersil CA3130.
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Old 07-02-2011, 12:37 PM
chervokas chervokas is offline
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Quote:
Originally Posted by WailinGuy View Post
Again, it depends upon the pedal - some just seem to sound best with the stock chip - but, in some cases, switching to a higher quality, "more high fidelity" op amp in an OD pedal doesn't necessarily make the distortion sound more hi-fi. Sometimes it can make the distortion sound more natural, or refined, or give harmonics that are closer (but never exactly, of course) to what a preamp tube might generate. This was the case with my Barber LTD SR. It sounded nice with the stock RC4558, but the distortion character seemed slightly rough, with some congestion in the low midrange I couldn't dial out. Swapping it for an LM1458 improved things quite a bit, and then going to a Burr-Brown OPA2604 made even more difference. The overall tone is now even more true to the original guitar signal, and the added harmonics are very pleasing and sound very "connected" to the fundamentals, like with a good tube amp.

So, for anyone who is so inclined, I would encourage you to experiment. Most dual op amps are very inexpensive, so it doesn't cost much. I do recommend using a chip puller tool (Radio Shack might still sell them), which can really help in removing chips straight up off of their sockets, without bending the pins. Much easier than using fingers, pliers or a small screwdriver.
Yeah, it besides being subjective it's also depends on the rest of the circuit. I have Barber Direct Drive Low Gain version, which I love, but which I didn't very much like the OPA2604 in that drive (I tried it because I just happened to have a couple sitting around).
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