Supergreen Thread

[rankot]

Anyone tried to make a Supergreen with a dual op-amp on output, instead of two single?

 

[rankot]

Anyone tried to make a Supergreen with a dual op-amp on output, instead of two single?

Anybody? Actually, why using two single opamps there? Is there some electronic reason (separation, for example), or just noise performance (since NE5534 has slightly better noise figure than NE5532)? Why not using some modern dual opamps, like LM4562 or OPA1678?

 

[Whoops]

Anybody? Actually, why using two single opamps there? Is there some electronic reason (separation, for example), or just noise performance (since NE5534 has slightly better noise figure than NE5532)? Why not using some modern dual opamps, like LM4562 or OPA1678?

Hi Rankot,
understand that this was a really old project in this forum, one of the first Mic preamp projects around here. It was before the Neve, SSL and API Mic preamp projects, and before also the 500 series projects.
If you check the dates in this thread you will see that the last bulk of conversations was in 2007, that was 17 years ago, so it will be hard to get developments or even replies on a project that no one is doing for 17 years.
When I joined this forum in 2008 this project was already dead, the Green Mic Pre (more popular than the Supergreen) was phasing out and people were doing the SSL 9K preamp. Neve 1290 diy mic pre came right after.
You can do for sure any project you want, and if you want to do this you should do it but don't expect much support,
to get better support in the threads you would have to do a newer mic preamp project with active threads.

As for your questions,
Probably at the time people were doing the project with the components that were easily available,
maybe that was the reason for the 2 single OpAmps. Since then many ICs and Opamps were released, with better specs and sizes.
NE5534 and NE5532 were cheap and easy to get.
I would guess if this project was developed nowadays that it would use different components, maybe it would even be SMD.

You can use whatever you feel is appropriate or better by modern standards, follow you guts and have fun

 

[rankot]

You can use whatever you feel is appropriate or better by modern standards, follow you guts and have fun

Yes I know, but I wanted to build this one, just for fun and to learn something new. It is not expensive, no ultra expensive transformers or other parts. However, thanks for replying! All the best in 2025!

I also made a model for it in ltspice, but it is not showing expected performance - gain is always around unity. Have no idea why, checked it three times in past two days...

 

[Flatpicker]

I think I see a couple mistakes on your LTSpice schematic per the original one: 1) R16 should be connected to V+, not V-; 2) C26 should be in parallel to R24 and not connected to R10. However, I corrected both of these but still could not get the simulation to work. Ferrite beads are also missing, but shouldn't be needed for the sim. (FWIW you don't need to include phantom power and protection zeners for a simulation of just the preamp operation.) If I weren't so dang busy I would dig in to see why, but maybe someone else here will dive in.

This is similar to the double balanced preamp that Cohen wrote about (and folks like Millennia are still making their version and selling them for mega dollars). It's definitely an interesting concept to learn about and experiment with. I bought a couple Supergreen boards back in the day but never built them.

Regarding the diff output amp, I can't see that it would matter whether separate or dual op amps are used (maybe they used separate due to crosstalk?)

 

[ricardo]

I haven't looked at your LTspice file in detail but note the mistakes Flatpicker mentioned. There may be more.

But I think your main problem is these mike preamps need a Gain Setting resistor, between the feedback points A & B to have gain.

 

[rankot]

I think I see a couple mistakes on your LTSpice schematic per the original one: 1) R16 should be connected to V+, not V-; 2) C26 should be in parallel to R24 and not connected to R10. However, I corrected both of these but still could not get the simulation to work. Ferrite beads are also missing, but shouldn't be needed for the sim. (FWIW you don't need to include phantom power and protection zeners for a simulation of just the preamp operation.) If I weren't so dang busy I would dig in to see why, but maybe someone else here will dive in.

This is similar to the double balanced preamp that Cohen wrote about (and folks like Millennia are still making their version and selling them for mega dollars). It's definitely an interesting concept to learn about and experiment with. I bought a couple Supergreen boards back in the day but never built them.

Regarding the diff output amp, I can't see that it would matter whether separate or dual op amps are used (maybe they used separate due to crosstalk?)

Thanks for spotting! Yes, I also presumed that they used separate op amps to prevent crosstalk.

 

[rankot]

I haven't looked at your LTspice file in detail but note the mistakes Flatpicker mentioned. There may be more.

But I think your main problem is these mike preamps need a Gain Setting resistor, between the feedback points A & B to have gain.

Exactly, that's why I have one labeled Rgain.

 

[Flatpicker]

Finally got time to take another look and found a couple more errors:

1) Both of the diff AC inputs phase was set to 0 (one of them needs to be 180)

2) There is an error on the original schematic - the DC blocking capacitors are in parallel with the gain resistor instead of being in series with it (however, the board appears to be laid out correctly, hence the reason no one ever caught this).

Besides that I cleaned it up a bit and removed all the things I mentioned earlier that it doesn't need. Appears to be working fine now.

 

[Matt Syson]

As far as I remember the 'Green Pre' was a rip off (copy) of the mic preamp stage used by AMEK.
The giveaway that it was a rip off is because it included the faults that AMEK later corrected.
The ferrite beads help reduce or eliminate RF demodulation.
Repeating previous persons errors is a sure give away that you have not worked on it yourself.