Mach 1 OPA2134 Alternatives?

[FancyEspresso]

I'm starting to order parts for a Mach 1 Overdrive (greer lightspeed). Is there a good substitute for the OPA2134? It seems hard to find and expensive... I'm guessing any dual op amp would work, but will this mess with the core sound of the overdrive?

 

[Bobbyd67]

Tayda used to have them for "cheap" around 3,5$. Dunno if they are gonna restock :/. My guess is ifyou stick a tl072 in it you won't see the difference

 

[phi1]

The light speed does have a higher clipping threshold than many overdrive pedals. One direction has 3 diodes in series. So, it may be more sensitive to op amp selection than other circuits since it’s operating closer to the power rails to create clipping. (I haven’t built this one myself, just speculating).

it will certainly work with a tl072 or similar, and the difference may be subtle. Definitely socket it either way so it’s easy to experiment with later if you want. (I prefer socketing all my op amps anyway). Just be sure to use the ones that look like this since they’re more reliable than the other types.

 

[FancyEspresso]

That's what I think I'll do... just socket the tl072 until i have to get something else from mouser so I'm not paying $8 shipping for a $4 part ?
Thank yall for the help

 

[Chuck D. Bones]

I agree, it's unlikely that you'll hear the difference using a TL072. If there is a difference to be heard, it will be at low DRIVE levels where the signal passes thru clean.

 

[AngelArm777]

I have a Greer Southland and it has a TL072 inside. The Southland is built on the Lightspeed platform, so it should work okay.

 

[steelplayer]

I just got a few from Mouser -- $4.80 a pop. Not cheap by any means, but not as bad some others. Tayda still hasn't restocked.

https://www.mouser.com/ProductDetail/Texas-Instruments/OPA2134PA?qs=7nS3%252BbEUL6uyT34OzaiM4g%3D%3D

 

[P51994]

hi there.
could there be some subtleties with the OPA2134 ? I've built several of these pedals for friends. One sounds warmer than the other. All components except the OPA2134 have been measured and are identical...

 

[Chuck D. Bones]

The OPA2134 is designed to be transparent. They should all sound the same.
There are a lot of counterfeit OPA2134s for sale. If you have a breadboard, you could measure the power supply current. That's a fairly reliable indicator as to whether the part is legit or not. You could also post a hi-res photo.

One of these is fugazi. Care to guess which one?

 

[P51994]

Thanks for your answers. The first one is fugazi I guess ! So mine are like the second picture. So the two pedals I built sounds good but one better ... So do I need to sort my OPA2134 to get the best ? like old germanium transistors ?

 

[xconverge]

I also just experienced an issue with one from tayda, not sure where you sourced yours from. The issue with mine wasn't a warmness it was straight up noise and distortion/overloading/clipping/different behavior when it should not have been due to different specs on whatever chip it actually was

L

Thread 'checking for fake OPA2134?'

Sep 16, 2020

I think ChuckDBones posted awhile back that he had spotted some fake OPA2134 by measuring current - is this the geneal method to check for fakes?

• lcipher3
• Replies: 10
• Forum: General Questions

 

[Chuck D. Bones]

The first one is fugazi I guess !

Correct. The surface is rough from the original part number being removed, the leads are scratched from mishandling, the logo is wrong and the LDC does not follow the TI LDC format. The power supply current was low. It was probably a TL0x2.

So do I need to sort my OPA2134 to get the best ?

Absolutely not. If they don't all sound the same, then one or more of them is bogus. Is your board socketed? How many spare OPA2134s do you have? You could try subbing other OPA2134s. If all of them sound the same, then it's your board. Or try alternate opamps and see if you find something you like better.

Did you measure the resistance & taper of your TONE pot? The tolerance on them is pretty loose, so that might be the culprit. Easy to measure in-circuit because C8 blocks DC. Should be within ±20% of 10K when TONE is dimed. Should be 15% of that reading at noon.

One more thing...
Most of the signals return to Vref, not ground. That puts C101 in the audio signal path. Depending on C101's ESR, capacitance & dielectric absorption, you could get tonal differences.

/rant mode on/

It vexes me why someone would design an audiophile-grade opamp into a dirt pedal.

I do not agree with the design philosophy of returning signals to Vref when they could be returned to ground. Ground will always be cleaner than Vref. Everything that connects to Vref has a cap in series except R3, so it's not a matter blocking DC. It would be simple enough to put a cap in series with R3 and return it to ground.

I imagine Greer had their reasons for doing it this way. It's not clear to me what they were.

/rant mode off/

 

[Chuck D. Bones]

I also just experienced an issue with one from tayda, not sure where you sourced yours from. The issue with mine wasn't a warmness it was straight up noise and distortion/overloading/clipping/different behavior when it should not have been due to different specs on whatever chip it actually was

L

Thread 'checking for fake OPA2134?'

Sep 16, 2020

I think ChuckDBones posted awhile back that he had spotted some fake OPA2134 by measuring current - is this the geneal method to check for fakes?

• lcipher3
• Replies: 10
• Forum: General Questions

Power supply current is one easy method for spotting fakes IF the real deal has a power supply current that is significantly different from the parts used to make fakes. It's valid for the OPAxxxx series in general and the LM308 in particular. When you measure opamp current consumption, measure only the current flowing into the opamp's power pin, not the current flowing in the two 10K resistors.

 

[xconverge]

Yea mine was in a General Tso compressor so it was very noticable/important for me to get right due to it's role. Totally agree with @Chuck D. Bones on it's use in this application!