All things Green Pre

[clister01]

Hey guys,

Working on a 2 channel green pre and I'm running into some weird problems.

As far as voltages go everything seems to check out perfectly. The PSU reads just as it should all over and the three NE5532 on each channel all seem to be working just right. Yay!

Problem is that no audio passes. Nothing seems to be going in or out. I've checked for shorts and can't find anything.

I've built two channels of this beast before and I noticed that when I turned the thing on the LEDs would flash briefly (kind of the "I'm alive" sign). But this time nothing happens when I turn on my switch (I know the switch is working).

At first I thought maybe I'd wired something funky or there was a short somewhere but it seems to be the exact same problem on both channels. Anybody got any ideas? I already skimmed through all 30 pages of this thread

-Cameron

 

[peterc]

Cameron

Try working backwards!

Inject a signal into the last 5532, see if there is anything on the output. It is purely an output balancing stage. If that is OK, move to to the IC before that, inject, measure.

Peter

 

[maxheadroom]

hi guys,

first of all i would say hello (this is my first post)
in some of the rainy summerdays in vienna, i finished my first diy project, a quad green pre. so, i would thank the people who helped me, specially pete for the design. here are some pics: http://gasman.lima-city.de/

greetings from vienna

 

[3nity]

nice job! awesome front panel! cheers!

 

[peterc]

Good build man. Nice front panel.

Peter

 

[maxheadroom]

thank you pete, thats your design :grin:

i compared it with our sountracs topaz projekt 8 desk, and the green sounds really great!! in my opinion the green is "opener"

 

[3nity]

i don't know if this sound weird but in one channel i used .1uf ceramics caps and in the other i used panasonics films caps....ouch what a difference!

Films sounds so bright compared to the other channel who's dark colour.
hope this helps some new builders!

cheers.

 

[grebdnul]

So.. Another one decided to build two of those nice green pre's..
I'm not very experienced but have built a couple of things before.

Does anyone have PCB's for sale?
I need 2 greenpre's and 1 PSU PCB.

I found partlists for the pre but can't fint the right one for the PSU.
Does anyone have a link for that one?

Seems like a really nice project and not too hard.. Can't wait..

Thanks for your help

Philip, Sweden

 

[sunyata]

Hi,
Thank you so much for allowing this info to be spread freely. I find it informative and extensive enough for me.
I just recently finished building a Green Pre Mk1. One channel so far. There will soon be one more. PCB already etched. (I will post pics when I have a "good looking" box to show. Some of you diy:ers sure do make nice builds!!)
It sounds very nice and clear. At the moment there are two OPA2132 instead of the 5532's in it. Does anybody have any comments about different opamps? I found it difficult to tell the difference after comparing in Cubase.
What is the the output level? -10dB or +4dB? I haven't built any LED meter yet. At the moment I run it through a DBX MC6 compressor running at -10dB, then into a ALESIS AI3 ADAT interface (switchable between -10 and +4)
I'd like to build a simple, good sounding compressor to match my Green Pre. I mainly record acoustic guitar and vocals. Any comments on the "What compressor" or the "Weak Joe compressor" or maybe even the "Gyraf 1176". Is it advisable to put a compressor in the same box as the Green pre?


Best regards and thanks again.

Sunyata - Göteborg, Sweden

 

[kato]

[quote author="sunyata"]
It sounds very nice and clear. At the moment there are two OPA2132 instead of the 5532's in it. Does anybody have any comments about different opamps? I found it difficult to tell the difference after comparing in Cubase.
[/quote]

You shouldn't be able to hear a difference between the OPA2132 and the 5532.

Post pictures even if your box doesn't look good! We all like to see what you work on!

 

[grebdnul]

Hi,
I started soldering all the pcb's today and of course ran into some problems.. For the diode-bridge in the PSU, I couldn't find one with the same specs as the one in the BOM. So I bought one here in Sweden..

KBPC108 Bridge 800V 3A.

Will that work? I'm not very good at electronics, but I'm hoping that this one will do. It's only for the ac->dc-transforming, right?

I will upload images as soon as the thing starts to look as some kind of audio equipment. Later on I also plan to contribute with some recordings and comparsions to my current E-MU 1820m preamps, for those who are interested.

/Philip
Stockholm, Sweden.

 

[peterc]

That bridge will be fine. Make sure it fits the boards.....

Peter

 

[grebdnul]

thanks.. it fitted just fine.

 

[RJS]

Hey Guys,

I'm working on a 2 channel Green Pre. I finished all of the wiring and started doing to the calibrations.

I was able to do the first 2, CMRR and DC Offset, however when I started setting the LED levels I noticed some problems. Although I can pass a clean signal through both channels, both green LEDs on both channels stay on regardless of input signal, the yellow fluctuates with an incoming signal (like it should) and red stays unlit no matter how high the input. The LEDs are in correctly and they do work as I tested them individually. Also on one channel, when I switch the HPF where the lever/bat is up (HPF engaged?) I can't pass a signal and if I turn the output pot to about halfway or greater while the switch is in this position, I get howling feedback which I guess is oscillation. I checked to see if the switch was bad and it works as it should. I also checked my soldering connections and they seem okay.

Other than these issues, the signal through it is clean, the phantom power works on both channels and there is no buzz, noise or hum.

Any ideas?


Thanks,
Robert

 

[grebdnul]

Hello again.
I have a question about the zener diodes..
I've got 5W instead of 1/2w. Ordered wrong ones from farnell.. Still 20V though. Will these work or should i replace them with 1/2w?

/Philip, Sweden.

 

[sunyata]

[quote author="kato"][quote author="sunyata"]
It sounds very nice and clear. At the moment there are two OPA2132 instead of the 5532's in it. Does anybody have any comments about different opamps? I found it difficult to tell the difference after comparing in Cubase.
[/quote]

You shouldn't be able to hear a difference between the OPA2132 and the 5532.

Post pictures even if your box doesn't look good! We all like to see what you work on![/quote]


Hi,
I have two OPA2132's in channel 1 and two 5532's in channel 2. They both sound very good, however there is a difference in gain between the channels (approx 2 steps = 12dB?). Can this be due to the different ops, or due to un-matched resistors in the Lorlin-switches? I have only used metalfilm resistors throughout the entire project.

Here are some pics of my Green Pre. Maybe it will look OK with a new front? I used an old scrap-box I had and screwed on an old piece of alu on the front. I also had an old Transformer (30VA) among my junk.

Here is a short sound-clip recorded with two mics in stereo:

http://goto.glocalnet.net/lars_wallgren/mp3/green%20inspiration%20clip.mp3


Thanks again

/Sunyata

 

[maxheadroom]

5W will work

 

[kato]

[quote author="grebdnul"]Hello again.
I have a question about the zener diodes..
I've got 5W instead of 1/2w. Ordered wrong ones from farnell.. Still 20V though. Will these work or should i replace them with 1/2w?

/Philip, Sweden.[/quote]

the voltage value is what's important.
higher wattage will work just great - in fact higher is better than lower - although the leads may be too fat to fit through the holes. (if so, you can drill larger.)

 

[grebdnul]

[quote author="kato"][quote author="grebdnul"]Hello again.
I have a question about the zener diodes..
I've got 5W instead of 1/2w. Ordered wrong ones from farnell.. Still 20V though. Will these work or should i replace them with 1/2w?

/Philip, Sweden.[/quote]

the voltage value is what's important.
higher wattage will work just great - in fact higher is better than lower - although the leads may be too fat to fit through the holes. (if so, you can drill larger.)[/quote]

Thanks. Yeah, the leds are a little to fat, so I'll just drill those holes bigger.
I'm curious about the zeners. I know that they can pass current "backwards" if fed over a threshold voltage (20v in this case, I suppose). But what functioindo they have in the Green Pre?

Thanks for the help.

/Philip, Sweden.

 

[RJS]

I got the HPF sorted out. I followed the connection and found a solder pad that was lifted and not making a connection to the trace on the board.

Now if I can just figure out why those LEDs aren't working properly........what's weird is when I put a really hot signal in, they actually go off, it's like they are working in reverse...... :?