Opa2604 substitute.

D

dlazzarini

Well-known member
Hey guys I’m sourcing parts for the Wonder Drive. I’m finding that the opa2604ap is obsolete. I can find plenty of them on eBay but I’m very leery about ordering IC’s from China. I don’t want to get bit with a phony. What would be the next best thing?
 
Dual Op Amp Equivalents:

AD712 - Slew = 16V/µs
CA3240 - Slew = 9V/µs;
LF353 - Slew = 13V/µs
LM358 - Slew = 0.3V/µs (@ unity)
LM1458 - Slew = 0.5V/µs
LM2903 - Diff. Comparator
LM4558 - Slew = 1.7V/µs
LT1490 - Slew = 0.06V/µs
uPC4570 - Slew = 7V/µs
LM4560 - Slew = 5.5V/µs
LM4580 - Slew = 5V/µs
LM833 - Slew = 7V/µs
LMV652 - Slew = 3V/µs ~ 0.12 mA;
NE5532 - Slew = 9V/µs
OPA1642 - Slew = 20V/µs
OPA2107 - Slew > 9V/µs
OPA2134 - Slew = 20V/µs
OPA2604 - Slew = 25V/µs
OP275 - Slew = 22V/µs
RC4559 - Slew = 2V/µs
TL022 - Slew = 0.5V/µs ~ 0.13 mA
TL062 - Slew = 13V/µs
TL072 - Slew = 13V/µs
TL082 - Slew = 13V/µs
TLE2072A - Slew = 35V/µs
 
Other design considerations are noise and input bias current.
Slew rate is not too much of a big deal considering that the max slew-rate of an 8Vp-p 10KHz sinewave is 0.25V/us.
 
Thanks for the quick replies guys. This pedal is pretty much a staple in front of many 5150’s so I want to keep it as close to original as I possibly can. I’m not against spending a little more on the right op amp. What would you guys consider the closest?
 
The thing that makes the difference between opamps in pedals like the Wonder Drive is how they recover from saturation. That is not in the spec sheet, so your best bet is to install a socket, try what you have and settle on what sounds good. Don't be too surprised if they all sound about the same. The OPA2604 is advertised as "low distortion" which is a bit ironic in this situation.

This store claims to have some. I have no idea if they are legit.
 
Chuck D. Bones said:
The thing that makes the difference between opamps in pedals like the Wonder Drive is how they recover from saturation. That is not in the spec sheet, so your best bet is to install a socket, try what you have and settle on what sounds good. Don't be too surprised if they all sound about the same. The OPA2604 is advertised as "low distortion" which is a bit ironic in this situation.

This store claims to have some. I have no idea if they are legit.
Click to expand...
I was just looking over the website you linked. Read up about them. They seem pretty legit. Have you ever ordered anything from them Chuck?
 
Sorry to revive an old thread but I'm having similar issues, obviously can't find any 2604s, I have some OP275s and I'm happy to try them. Every 2604 on eBay is from china, which seems pretty suspect, I'm tempted to grab some from that site chuck linked, they seem cheap enough to gamble on. No idea how I would test them though to see if they are what they say they are. How do I test an op-amp?
 
Grazza said:
Sorry to revive an old thread but I'm having similar issues, obviously can't find any 2604s, I have some OP275s and I'm happy to try them. Every 2604 on eBay is from china, which seems pretty suspect, I'm tempted to grab some from that site chuck linked, they seem cheap enough to gamble on. No idea how I would test them though to see if they are what they say they are. How do I test an op-amp?
Click to expand...
Just use whatever dual jfet you have on hand. 275 should work fine. I think a R2R like a 2272 would even work as I don't think there's any opamp clipping, looking at the schem for 15 seconds.
 
Grazza said:
Every 2604 on eBay is from china, which seems pretty suspect
Click to expand...
Why would you even consider buying premium opamps on eBay?

jwin615 said:
I don't think there's any opamp clipping, looking at the schem for 15 seconds.
Click to expand...
I looked at it for 20 sec and IC1.1 can be driven to saturation if DIRT is turned up high enough. So can IC1.2. The OPA2604 datasheet does not tell us what happens if the inputs are driven close to the rails. Some of the OPA JFET input opamps go haywire when driven to the positive rail. IC1.1 is capable of driving IC1.2's + input very close to the positive rail. As jwin615 states, a R2R opamp like the TLC2272 would behave much better in that situation.

The Wonder Drive is basically a TS with the clipping diodes removed. If you're setting DIRT below the clipping threshold, then it's a clean boost. Nothing special. The input and output buffers are superfluous. No, there won't be a Boneyard mod for this.

Grazza said:
No idea how I would test them though to see if they are what they say they are. How do I test an op-amp?
Click to expand...
To do it right you need an oscilloscope, a sign gen and an understanding of the datasheet specs. There is no cook-book approach. Basically, what you want to do is verify if the parts you bought satisfy the particular specs that make the OPA2604 worth the money that a legit seller like Mouser charges.
 
To be honest, eBay was the absolute last resort, as soon as I saw they were all from China, I got pretty disheartened. Don't have a scope yet, still building pedals and learning, though it may be a purchase this year. Might try some 2272s, just bought some 2262s for a project, without looking at data sheet assuming they aren't compatible.
This pedal is intended as a high gain boost anyway, doubtful the gain will be up over halfway, might be wasting my time fussing over op-amps. Is this similar to spending a heap of money on NOS diodes for a klon and never turning the gain up?
 
Pop in what duals you have and audition them
If it sounds good, it is good.
If it oscillates, motorboats or sounds like someone replaced a catalytic converter with a barn cat, try something else.
It's likely the reason that opamp was first chosen is on the top of the datasheet. "Low Noise"
There's more mojo to abusing shitty opamps than "good" opamps.
2262 is rail to rail cmos input. Very different than a jfet but who knows, you may like it. Or it may sound like diesel cat farts. But you won't hurt it at 9v.
 
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