All things Green Pre

[enthalpystudios]

well, i'm a douche bag newbie.

psu is fine. hooked it back up. checked voltages on the psu terminals. a-ok. hooked up my "molex power snake," and check voltage on each molex pin that goes to the 4 pre's. a-ok. Hooked er up, passing audio 100%.

I took out all the leds, as i'm not using them and didn't end up putting holes in my frontpanel. I have a feeling that short was the issue, it looks like that trace ran right to the tl074 10R/10uF section.

I'll replace the 10r's and 10uF caps tomorrow, and put tl074's back in. I have these little futurlec vu's, i'm going to read up on the tl074/lm339 datasheets.

One thing, real quick, if I may, does someone know off hand A) if rectification (half or full wave) takes place in the metering section, and B) if so, what rectifies it?

Basically I'm wondering if I can leave out the lm339 and solder my VU leads to two holes in the LM339's IC socket, and I'm wondering if that signal is rectified already by the tl074 or something like that. These vu's definitely have no diodes.

thanks again,

billy

 

[jollyted]

.
Someone on the Lab asked me by email if I still had any of the finished Green Pre PCB's left for sale. But I can not find the email... I'm thinking I deleted it by mistake.

So if you happen to read this, I do have some at left...
http://www.groupdiy.com/index.php?topic=15360&sid=b0c42ab32c7f74003cfb402ee7777ff9

In the Black Market.

Or contact me (Joe Gianini) at GRS as Ted Jolly has had a serious accident and i will be handling all of the orders and shipments

[email protected]

Thanks,

Joe G.
GRS
.

 

[JayDee]

Peter,

I have some small trouble using my brauner mic on the green pre. It seems, the brauner has too much input for the green. The range of the gain is in the 1/3 rd of the 12 steps and I sometime have a little ditortion in the highs (like a female "s").

I think it´s a problem with the input impedance ?

How can I adjust the input stage or how can I solve this problem ?

With non electric it works very well...

Cheers
Jürgen

 

[peterc]

Try & whip up a quick pad, there is a thread that is going on at the moment about this.

I've never heard of any problem like this. I've even used it as a line level preamp without any probs.

Peter

 

[cannikin]

Hey Peter,

I'm testing the PSU (your design) and I'm getting some strange readings.

+24.8Vdc
-15.5Vdc
49.9Vdc

Any thoughts on what to check? All Components values are Correct and polarity is right according to your layout.

Could it be the LM317?

 

[Ptownkid]

Most likely, check the output leg of that one.

 

[cannikin]

[quote author="Ptownkid"]Most likely, check the output leg of that one.[/quote]

Yup the output is giving me 22V....

Going to replace it.. be right back

 

[cannikin]

Nope wasn't it.... Still the same Voltages

 

[peterc]

David

Check the orientation of the Output to Input diode (1N4007) of the pos reg. Try lifting one leg & check that the output voltage is correct. If it is, then swap the orientation of the diode.

What is the date on the PCB? Id it marked before 6/5/2005, then that diode faces the opposite way to all the others. Is the PCB date is after 6/5/05, then all the diodes face the same way.

Peter

 

[cannikin]

AHHH :shock: peter! :shock:

Its Version 3 dated 22-4-5

Man I was going crazy last night....

I built both PSUs that I have and they both were doing the same , swapped out Transformers

CHased my tail a few tail a few time too :shock: :?

 

[cannikin]

Yup confirmed it was that Diode..... That fixed that...

+15V
-15V

But the Phantom....

84Vdc ?? :?

 

[matta]

Hey David,

Just want to confirm, for the +48V rail how many diodes are in series on the +48V? What is the DC voltage before the +48V regulator? Check it after last IN4007 before the +48 Reg and report back.

If you are getting 84Vdc I think your have most prob blown your caps as well if the ratings were less than 100Vdc.

Any change of a pic of the PSU, I will take a look and check it over for you.
If you can't post it mail it to me at matt(at)matt-allison(dot)com

Cheers

Matt

 

[enthalpystudios]

hey guys....

well i got a scope a few days ago, and decided I better recheck the CMRR on my green's. The dmm did a horrible job, and luckily I used the scope and got chan's 1-3 calibrated to really really low cmrr, almost no waveform at 5mv/div.

Anyway, channel 4 ranges from (at the lowest 1k trim pot setting, CCW) .7 volts p-p to about 1.2 v p-p at the highest setting.

Any ideas about this one? That channel hasn't sounded awful in tracking the last few weeks, but they've all been a tad noisy since they weren't setup right.

Thanks for any ideas anyone might have. I'm probably going to try switching out that 5532 first, quick try at something.

EDIT: just checked levels and so forth, seems that channel 4 also has very little gain. I'll post back regarding a different 5532

wierd

Billy

 

[peterc]

Billy

Check the DC conditions around the bootstrap transistors - compare channels. I've had one of the BC550's go bad before.

Peter

 

[bluezplaya]

Hey gang, I just got a couple of Green's in from PTown. I have stuffed the first board but am wondering which way do I solder the 100k trimpot? The PCB clearly shows where the screw is on the other two trimpots, but not on the 100k. And the 100k is not the same shape as the other two. Is this anything to worry about?

Thanks,
Adam
:sam: :sam:

 

[DaxLiniere]

Hey Adam!
Peterc designed the 100k trimmer position pinout to suit 2 different types, so all three could be the same shape, if you wanted. Using a multiturn trimmer as in the "other type" is only necessary when you need to be able to make fine adjustments, which is not needed for the meter trim.

Anyway, back to your question; either way, you can't go wrong.

 

[bluezplaya]

Sweet! Thank you.

Adam :sam: :sam: :sam: :sam:

 

[peterc]

Either type will work & with linear variable resistors, there is no "right way round".

Peter

 

[bluezplaya]

I got my 2 Green pre's finished! Woo-hoo! I do have some minor issues that I could use some help on. Boy these things have some pretty nice gain and headroom. I ran my Beta 57 dynamic mic through it and into my Digi 001 unit (on to Pro Tools) and it sounds nice and full. However, when I hooked up my condensers (Studio Projects C-1, MXL 603) I get a weaker signal as well as some hum.

I have to crank the input to the max to get the strongest signal but I also get a lot of hiss when I do that. And there is a low hum when the output knobs are all the way down. It goes away as I turn them up. I suspect that my 48v is not connecting properly and I'm having grounding issues with the output XLR's, but this is where I need help on the topic.

Any help out there?
Adam
:sam:

 

[DaxLiniere]

Yep, sounds like phantom & grounding issues.

You should check that the PSU is delivering enough juice and doesn't sag when phantom is switched on.

I'm sure in the 25 pages of this thread there is some info on that.

Also, don't forget that grounding directly affects the phantom supply. example, if you didn't have the gnd connected to pin 1 at all, then your mics wouldn't be getting any power at all.

Might be a good idea to post a photo of the inside of your box, too.