Bought a bunch of OPA2134s from Mouser and they were fake. After sending photos, Mouser agreed and sent me a refund (very nice of them). Watch out for fake ICs folks, real Burr Browns's are easy to spot - should be a notch at the top end, and the pin 1 indentation should be directly over pin 1. The fakes have no notch at the top end and the pin 1 indentation is between pin 1 and pin 2.
Built a couple of dumbloids. They sound quite interesting, but, to be honest, I wouldnt let the op amp do the whole clipping. I've tested lots and lots of diferent clipping arrangments. Symmetrical standard silicons just make it a fat tube screamer. Mosfet + schotky ("ala" zen drive) sounds awesome, but again, it looses some of its character. So I tested different LED config and colours. I ended up using asymmetrical yellow and green LEDs. The higher forward voltage lets you hear the op amp clipping, but also adds a nice touch of their own clipping and compression, leading to a very open and yet smooth sound.
Edit: if using no diodes, i found that lm1458 chip clipped in a nicer way. A tad less harsh in the decay. But using the yellow/green led, I used the original. It has a nice and clearer top end, but the harshness is shaved of by the leds
Love dumble overdrive! any recommendations for substitutes for the BC548Bs?
ReplyDeleteThe transistors acts as input and output buffers so as long as you use medium to high gain NPN Si transistors you're all good. Just mind the pinout.
DeleteJordan did you build it successfully?
DeleteVerified. Great sounding drive, bags of gain!
ReplyDeleteTotally missed your post. Thank you. I'll tag it when I can.
DeleteBought a bunch of OPA2134s from Mouser and they were fake. After sending photos, Mouser agreed and sent me a refund (very nice of them). Watch out for fake ICs folks, real Burr Browns's are easy to spot - should be a notch at the top end, and the pin 1 indentation should be directly over pin 1. The fakes have no notch at the top end and the pin 1 indentation is between pin 1 and pin 2.
ReplyDeleteBasically, the fakes are the same spec as a TL082 which cost peanuts compared to a genuine OPA2134
DeleteWow, fakes slipped through the net into Mousers inventory...:-/
DeleteGlad you at least got a refund...
Built a couple of dumbloids. They sound quite interesting, but, to be honest, I wouldnt let the op amp do the whole clipping. I've tested lots and lots of diferent clipping arrangments. Symmetrical standard silicons just make it a fat tube screamer. Mosfet + schotky ("ala" zen drive) sounds awesome, but again, it looses some of its character. So I tested different LED config and colours. I ended up using asymmetrical yellow and green LEDs. The higher forward voltage lets you hear the op amp clipping, but also adds a nice touch of their own clipping and compression, leading to a very open and yet smooth sound.
ReplyDeleteEdit: if using no diodes, i found that lm1458 chip clipped in a nicer way. A tad less harsh in the decay. But using the yellow/green led, I used the original. It has a nice and clearer top end, but the harshness is shaved of by the leds
ReplyDelete