Supergreen v1.6 - four channels of preamp

[thousandyards]

New user with my first post....thanks for having me! Total DIY newbie here, but hoping to get started with it all.

I was given a four channel DIY preamp unit. Popping the top off revealed the Supergreen v1.6 PCB with a JLM power supply. Joe is in my city so I know his gear is solid, which made me think these pres might just be a decent bit of kit.

I've showed these photos to a couple of people who tell me they look well put together (also the impression I got). I've got a few questions though, in case anyone has any experience with them and is feeling generous enough with their time to have a crack at answering. I know Olafmatt is no longer around but I've worked out these are his PCBs. I know it needs a service so I won't be plugging it in before I've had a tech look at it.

• Apparently based on the AMEK 9098 - true or false?
• Switches are Phantom, input impedance and polarity - any way of telling which is which based on these photos?
• Heard there can be noise issues from the channel closest the power supply - thoughts? Is the power supply close enough on these to be an issue?
• The ventilation slots you can see in the bottom of the case are the same for the lid - is this enough? Would less be a problem? I won't be stacking anything directly on top of it in a rack.

Pics:






Hope this isn't too presumptuous to chase this many answers on my first post.

Thanks everyone.

 

[Whoops]

Hello thousandyards,
Welcome to the forum

Apparently based on the AMEK 9098 - true or false?

Do a search in these forum, there's a lot of threads on the Green Preamp, that information is there for sure

Switches are Phantom, input impedance and polarity - any way of telling which is which based on these photos?

Should be Phantom, PAD (attenuation) and Polarity. I can't understand which is which by the photos, but you can know easilly in some seconds by trying it out.
Did you turned the unit on and used it?

Heard there can be noise issues from the channel closest the power supply - thoughts? Is the power supply close enough on these to be an issue?

Depends, do you have any noise problems or it sound good and clean enough?

The ventilation slots you can see in the bottom of the case are the same for the lid - is this enough? Would less be a problem? I won't be stacking anything directly on top of it in a rack.

No problems with that, the only source of heat are the Voltage regulators, that seem to be screwed to the case, so they use the whole case as a big heatsink.
You don't even need any ventilation holes at all

Best regards

 

[thousandyards]

Hello thousandyards,
Welcome to the forum



Do a search in these forum, there's a lot of threads on the Green Preamp, that information is there for sure



Should be Phantom, PAD (attenuation) and Polarity. I can't understand which is which by the photos, but you can know easilly in some seconds by trying it out.
Did you turned the unit on and used it?



Depends, do you have any noise problems or it sound good and clean enough?



No problems with that, the only source of heat are the Voltage regulators, that seem to be screwed to the case, so they use the whole case as a big heatsink.
You don't even need any ventilation holes at all

Best regards

Hey Whoops - thanks so much!

Great call on the heat sinks. Helps make the case decision A LOT easier!

I haven’t turned it on yet....there’s a resistor I can see needs replacing and it sat in storage for a while before coming to me. The top cover is rusted etc so I know it needs some work. I want a tech to check it over before I go firing it up and things catch fire

I did a search on Supergreen and there wasn’t a heap on the v1.6. I’ll get this serviced and I guess we’ll see how it goes!

 

[craig]

https://groupdiy.com/threads/supergreen.56370/

 

[craig]

https://groupdiy.com/threads/supergreen.56370/

From memory your switches are controlling the on board relays. Polarity, Z and 48v. Rear panel is GND lift.

 

[thousandyards]

From memory your switches are controlling the on board relays. Polarity, Z and 48v. Rear panel is GND lift.

Ahh I wondered about the rear panel too - thank you!!

 

[thousandyards]

https://groupdiy.com/threads/supergreen.56370/

Judging by some of the comments it sounds like the PCBs might have been different to the schematics or the actual wiring was meant to be different.....do you know if the diagrams are definitive and mistake free?

 

[craig]

There was issues with the orientation of some semi's, diodes perhaps but it's been so long since I built mine I can't be sure if the boards were silkscreened incorrectly or the schems were wrong. I worked it out however and I'm sure someone here will know the definitive answer.

 

[Whoops]

I haven’t turned it on yet....there’s a resistor I can see needs replacing and it sat in storage for a while before coming to me.

Just replace that resistor and try it out and test it.
It seems very well made, probably everything works properly even if it sat down for a while.

No need to be worries about problems we don't have. try it out have fun.
If there's any work to be done after then you will have clear picture of what the problem might be.

For the looks of it , it looks mint

 

[thousandyards]

Just replace that resistor and try it out and test it.
It seems very well made, probably everything works properly even if it sat down for a while.

No need to be worries about problems we don't have. try it out have fun.
If there's any work to be done after then you will have clear picture of what the problem might be.

For the looks of it , it looks mint

My n00bness cannot be understated here! I'm getting a good local tech to give it a once over so it's good to go. Will probably end up selling and upgrading my interface, to be honest! I've got an ISA One that just needs a new XLR wired in....might try my hand at some JLM builds after that to get my skills up

BTW - Whoops, do you know if the v1.6 Supergreen varied much from the v1.5 or v1.4? Apologies - I know these are some old designs. Just want to give my tech everything I can

 

[Matt Syson]

Interesting to see that the 1.6 version includes the modification I included for production of the origins in 1995 (or thereabouts. Should have 'patented' that bit I think! I even have a handful of the 'upgrade board' that was applied to desks that used the initial versions.
Matt S

 

[thousandyards]

Not sure if a 6 month later follow up is of interest to anyone here but I dropped this unit into one of the best techs in town (Hux Electronics here in Brisbane) and he went through it pretty thoroughly. Here were his notes - some on the specific condition of this unit, and some on the design overall.....

"Checked out unit, noted a lot of problems. Noted that the power supply rails were set way too high, adjusted. Noted that the 0 volt line from the regulator board was too light in duty, when Ichecked closely I found that the 0 volt terminal block was loose and corroded, replaced the terminal block, upgraded all main 0 volt wiring, fitted new "soft earth", re-terminated all other terminal blocks. Noted that the XLR's connectors were tied to "hard earth" and the electronics were tied to "soft earth", re-wired the XLR connectors to be on "soft earth". Noted lots of corrosion on the channel 3 board, removed the SW3 relay and other components, cleaned the board and replaced the components. Tested, noted noise when phantom power was switched on, removed the SW1 relay and cleaned up the relay and the board to remove unknown contamination, re-fit parts, all OK. Found that the regulator board was overheating, removed and improved the heatsink system. Made up test cables, set the two CMRR trim pots on each channel for best CMRR with the gain switch at 12.30pm. Noted that the rotary gain switches were intermittent, treated with a combination of Electrolube EML and Caig Labs DeOxit Gold (see notes). Noted that the mains transformer radiates into the channels a little, changed the orientation of the transformer to minimise hum pickup (see notes). Replaced the knobs. Sound tested, soak tested, all seems OK."