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RC3404 or MC3404 equivalents?

Jbanks

Active member
Working on a Boss OD clone and it’s asking for a MC3404 or I can also use RC3404. For the life of me I can’t find either of these online. I keep getting MC3403 and variants. Does that work? I can’t even find data sheets for the MC3404 but they’re both 14 pin chips, so I’m guessing they’re pretty close?

am I right? Lol

any advice on alternates or sources for MC3404/RC3404 would be greatly appreciated. I need just ONE! :)

thanks
 

Chas Grant

New member
The RC3403 was the original quad op amp used in the OD 1. It's been out of production for a long time. You may find one on E-Bay, but a lot of the ones you see are fakes, and a real one goes for a high price. Any 14 pin quad op amp will work as long as the pin out is the same. The MC3403 is a good choice, and the TL074 isn't bad either. But if you want to get as close to original as you can, try the NJM3403AD, it is the only one that is ground sensing like to RC3403. As this is this one of my favorite circuits, I've built quite a few and have experimented with it quite a bit. The best sounding ones I've built used the NJM3403AD, carbon film resistors and the green Mylar capacitors. Also alot of prints and clones show the feedback potentiometer as a A1M, the original used a B1M. Either one sounds good but there is a difference in the feedback response and a small tone change between the two. Experiment with them and use the one you like best. If the PCB has the clipping option on it, LEDS sound real good as the second option or Ge diodes work well also. Look for a high fwd voltage Ge diode though, this has a very noticeable effect on overall output of the circuit. Youll notice a large drop off in volume with Ge diodes, bit the warmth of them shines through.
 

Jbanks

Active member
Thanks so much Chas for that explanation. I just picked up a TL074 last night for another project. I’ll try that as well as the NJM3403AD. Thanks for the diode advice as well. Very good to know. My first OD-1 build!
 

Jbanks

Active member
The RC3403 was the original quad op amp used in the OD 1. It's been out of production for a long time. You may find one on E-Bay, but a lot of the ones you see are fakes, and a real one goes for a high price. Any 14 pin quad op amp will work as long as the pin out is the same. The MC3403 is a good choice, and the TL074 isn't bad either. But if you want to get as close to original as you can, try the NJM3403AD, it is the only one that is ground sensing like to RC3403. As this is this one of my favorite circuits, I've built quite a few and have experimented with it quite a bit. The best sounding ones I've built used the NJM3403AD, carbon film resistors and the green Mylar capacitors. Also alot of prints and clones show the feedback potentiometer as a A1M, the original used a B1M. Either one sounds good but there is a difference in the feedback response and a small tone change between the two. Experiment with them and use the one you like best. If the PCB has the clipping option on it, LEDS sound real good as the second option or Ge diodes work well also. Look for a high fwd voltage Ge diode though, this has a very noticeable effect on overall output of the circuit. Youll notice a large drop off in volume with Ge diodes, bit the warmth of them shines through.
Will 1N4148 diodes work fine? any specific Ge diodes you recommend?
 

Chas Grant

New member
You are welcome. The 1N4148 diodes are the modern equivalent of the diodes used in the original OD1 circuit, the work and sound great, 1N914's are great also. Use these as the first option for an original sound. Small Bear Electronics has a Hi FWD Volt germanium diode that works well, it has a forward bias voltage between .6V and .9V, which is close to the 1N4148 fwd voltage. This minimizes the lower signal from the pedal and adds a nice fat sound to it. Using the asymmetrical configuration here as well sounds nice. If the PCB doesn't have a clipping switch option then go with the 1N4148's to be as close to the original sound as possible.

Like I said, this is one of my favorite pedals. I've built 6 or 7 of them this year alone. I've been trying to get as close to the original sound as I can and also trying different clipping options to see how it responds. No matter which clipping options are installed, it sounds good! This is a tank of a circuit. I
 
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