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I have been sudying the idea of using a buffer for the VREF on a circuit.
The design, a bass preamp (it uses around 5 opamps) and, as it stands it uses a passive VREF with 10k resistors and a huge 220uf capacitor. This works well but that huge capacitor takes some time to charge and the first times I click the pedal's switch on and off, there are a few loud switch pops that eventually get cleared and pretty much disappear after a few presses.

My idea was to increase the resistors to 100k and lower the capacitor to 10uf and use a single opamp to buffer this vref and use it to bias the whole circuit. The idea is to make everything more stable and have an unmovable VREF since it will be feeding aorund 5 dual opamps.

Doing a bit of modern research, on the google AI, it offers me contraditory answers depending on the day I interact with it. It says I should add a 100ohm series resistor at the output to stabilise it. I can either use a TL071 or a opa1677 as an opamp for this job. Almost always it advises that the TL071 needs series resistance, so it seems to be consistent there, and then also more filtering at the output. So, I decided on using the OPA1677 because AI sometimes says it is ok to use the OPA1677 without any series resistance on the output (nor filtering capacitor) and sometimes it says it has to have it.

Any real world input on this by someone who has some experience would be very helpful!

Thank you in advance!!!!

I have made an older version of the Low Rider and compared the Octave Down vs the Octave down on my original Pearl OC-07.
They do not sound the same and it's killing me.

The Pearl has an hollowness and gritiness to the sound that the Low Rider does not have. The original Pearl has this kind of synthy quality to it while the Low Rider is cleaner and fater (it doesn't sound bad, but it doesn't sound as good).
I used an MC14013 for the Flip Flop and an LM2902 for the Driver of the Flip flop (the original uses these two).

I have tried three different diodes, one OA91 (germ), D9E(germ) and a Bat46. They all seem to offer something different to the sound (hard to say exactly what) but with none of them I get any closer to the sound of the Pearl Octaver. The Low rider sounds a bit bassier and it's deinitely cleaner (less artifacts).
Any tips on why I am not getting similar results to the original? How important is the germanium diode to the sound? Is it the diode or is it something else that I am missing?

I'm looking for a reliable 1N34A germanium diode replacement to use on the Low Rider analogue octave down project. I did some search and perhaps the BAT46 would work well on this design?

I am looking for something that is readily available.

Both the Boss OC-2 and Pearl Octaver (Low Rider) have identical single Jfet input stages followed by an opamp gain stage.

The question is, are these single jfet inputs even necessary or are they a leftover from the original bypassing mechanism? It seems like the pedal should work exactly the same if the jfet stage was left out, or am I wrong?

Input buffers. They are usually skipped when building "replicas".


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Right, that is what I thought but the Low Rider keeps this input stage.

Both the Boss OC-2 and Pearl Octaver (Low Rider) have identical single Jfet input stages followed by an opamp gain stage.

The question is, are these single jfet inputs even necessary or are they a leftover from the original bypassing mechanism? It seems like the pedal should work exactly the same if the jfet stage was left out, or am I wrong?

Gate arrow is closer to source

So S connects to VR
Though orientation probably doesn't matter.

Thank you so much!!!

I tried editing the post, but couldn't.
I have attached an actual image with the bit of the schematic that is relevant.
I understand that the Arrow indicates the Gate. How do we identify the Drain and the Source?

What exactly is the Pinout on the 2sK30 transistors. On the Lowrider schematic the pinout is not specified. I understand that the bit with the arrow is the Gate but how do I know which one is the Drain and which one is the Source?

It says that we can use 2n5457 instead but they have different pinouts, right? How do we know which one is which?
I have attached an image with the section that shows these transistors.

I found a PDF of the Low-rider (Pearl OC-7) which I built a long time ago. I no longer have the pedal but I was thinking of coming back to it.

I was looking at the schematic, and since I didn't find any use for the 2nd Octave down, I was wondering if the second Flip Flop chip (CD4013) is necessary even if we don't use the 2nd Octave down part of the schematic? Can I just omit it or is it serving some other purpose? I can see its CLK pin is connected the output pin on the other Flip Flop IC.

I have attached the schematic.

What is your point?

A very simple question regarding Vref and an extra opamp I have laying around on a circuit I'm working on.
I have an opportunity to use this spare opamp and was thinking of using it for Vref.

At the moment, for the Vref, I am using 2x 22k resistors with a 47uf filtering capacitor. My question is, if I add the opamp, can the resistors value be the same or would I need to adjust their values?

The SMD ones are called BC849.

I was also looking for this and had a look at both data sheets. They don't seem to be exactly the same.

The muff circuit biases it's transistors in such a way that the gain of each stage is independent of the transistor Hfe rating. I wouldn't expect the transistor choice to make too much difference. Anything with an Hfe of 325 or greater should work. That's most modern transistors. The 2N5089 is definitely hot enough.

It's not the hfe I'm interested in but the fact that these are lower noise.

I looked on the forum and couldn't find anything related to the BC459C, even though I'm pretty sure this has been debated to exhaustion.

I'm looking for an SMD version of the BC549C transistors. This is for a high gain fuzz (muff variant) and it's not easy to find smd versions of some trannys. The one that I can find is for the 2n5089...

I had already opened a similar post regarding the MPSA18 and I'm starting to realise that it's very hard to find some of these SMD versions of the transistors popularly used on so many fuzz units. 

Don't you need a matched PNP NPN pair for(optimal) push pull? May look at transistor arrays if that's the case.
I assumed this was for a pedal so didn't take voltage into account...

I'll add, check out the Alfa offerings

For this particular circuit, not really.