All things Green Pre

[peterc]

The original 8 channel I built was running @ +- 17.5 v, but I have changed this back to 15v as 2 of the 5532's went up in smoke......

The extra 3v only increses the headroom by a dB or so anyway.

Peter

 

[Flatpicker]

[quote author="peterc"]2 of the 5532's went up in smoke......[/quote] :shock:
What mfg were they? I've been running my TIs at +/-22V with no problems.

But yeah, if you only gain a dB, wouldn't be worth it.

 

[peterc]

What mfg were they?

They were Exar's. Replaced them with Signetics.

Peter

 

[jollyted]

.

Just a quick FYI...

I have 8 Green Pre's available for sale in the Black Market...

http://www.groupdiy.com/index.php?topic=14381&sid=3daf715bfc3f8935dc74665247d82b23

.

 

[enthalpystudios]

Hey folks....

I'm having some voltage oddities with my green pre's (4 of them).

Basically, on pin 14 of the LM339, where I should be getting -7.5 volts (according the the voltages doc from Peter), I'm getting about 15 volts on every pre.

On pin 6 of the LM339, I'm getting .7, 10.5, 9.4, and 7.65 respective to each channel of green pre.

On pin 4, I'm getting .3, 1.2, 1.06, and .3 volts DC (all of these are VDC)

On pre '4' all leds are lit up. Pre's 1-3 are getting no leds at all, although 2 of those don't have the first green led hooked up (ran out of red's).


Aside from all those lm339 troubles, green pre #1 is getting 2.5 vdc on pin7 of IC1, and pin 1 and pin 2 of IC2.

The metering isn't too important to me atm, I really want to try and record some stuff this weekend and have no other pres (!)

I guess I'm just hoping to get this problem in the 5532 section figured out first and foremost.


Also, I had a problem earlier where I had shorted the 0v test jumper to the 48v switch and had blown the 48v reg. I replaced all reg's (to be sure they'd be ok, and to install heatsinks on them for good measure), so the phantom section has a fresh lm317, and I'm still getting around 70 vdc on the phantom rail. Perhaps there is a resistor fried or something I could check on the psu?

Sorry for having so many voltage questions with odd numbers everywhere!

Thanks ahead,

Billy

 

[enthalpystudios]

almost forgot, all of those voltages are without IC's

thanks,

Billy

 

[enthalpystudios]

Also, what is the best way to ground things in this box?

I've got the input xlr's pin 1 coming to the pcb, but where should I send the output pin 1's? Also, should I be grounding the 0v dc out of the psu, or the 0v coming from the power transformer?

If I wanted to add a ground lift switch for flexibility, where should I put it?


Also, as per my previous problems, I just realized that my power transformer (amveco, digi-key TE62053-ND) is a 15VA 2x15v, so that's only 500ma per secondary, right? Probably not enough current, and probably the source of some of my above problems???

billy

 

[HappyTom]

[quote author="enthalpystudios"]


Also, I had a problem earlier where I had shorted the 0v test jumper to the 48v switch and had blown the 48v reg. I replaced all reg's (to be sure they'd be ok, and to install heatsinks on them for good measure), so the phantom section has a fresh lm317, and I'm still getting around 70 vdc on the phantom rail. Perhaps there is a resistor fried or something I could check on the psu?

Billy[/quote]

Might be a reversed diode?

HT

 

[enthalpystudios]

Yeah, I'll check it over.

When I ordered my power trannie, I ordered a blue pcb mount encabsulated style at 30VA, 2x15. I got the pcb style (like a newb) because Peter used one in his dual pre.... at the time I didn't want to get the wrong parts (although the pcb mount couldnt be more wrong, for me anyway).

Anyway, this green PSU was the first PCB I ever soldered, and my skills have gotten a lot better since I did that. Also, the size of my soldering tip and solder have gone down ;] I really kind of botched that PSU, so I think I'd rather etch another, with added tracks for the pcb mount transformer right on one board. Hopefully I can redo this PSU better... I really don't want to slack on this, because the one channel that I have gotten to operate clean and clear sounded really nice. Don't want these to one day be that first diy project that I botched and dont use on anything.

But thanks for helping me out with this, I've really learned a ton of stuff.

One question, though... which resistors on the PSU are setting the voltage for the reg's? I'm trying to figure out how thats working.

And the diodes for upping the voltage, do they simply run in series with the + voltage rail, and just up the voltage of their own nature?

Billy

 

[HappyTom]

One question, though... which resistors on the PSU are setting the voltage for the reg's? I'm trying to figure out how thats working.

The easiest way is to look in the related datasheet and compare with the circuit. I got no documents here so i can't pinpoint the resistor.

HT

 

[peterc]

If you got my PSU PCB, the 220R /2k2+220R combo gives 15v exactly (well, in theory).

Formula is 1.25 x (1 + (2k2 + 220R)/220R) = 15v!

For phantom the combo is 220R/8k2

Peter

 

[enthalpystudios]

cool, thanks for that! I've seen that formula on the datasheets, neat to see it on the psu.

all my diodes face the same way, by the way.... the diodes are jumping the voltage on the phantom side, there are three and then a jumper. I'm getting around 55 volts or so at the end of the second, and ~73 after the third. Not sure why, but like I said, I think I'm going to etch another psu, to give myself a shot at etching, and to integrate this pcb mount transformer that has a more appropriate current rating.

I'll see how things go once I've done that. Now just to decide which etching method I want to try out.

Thanks for the info

Billy

 

[OddHarmonic]

Back again I come to this project. After a bit of a hiatus working on other projects, I'm trying to tweak my 2nd Green channel so that I have four working. I keep having the same problem pop up with Q2. When I was getting very low amplification and heavy distortion, I traced the issue to around Q2, then I noticed low DC on the emittor. I saw earlier in the thread that ~.7 VDC was normal, and I was seeing that on Q1. Q2 however, had something more in the range of .05-.1 VDC. I swapped Q2 out for a new part, and the pre seemed to be working agian.

However, I put the card back in the case to run some real tests, and once again, the low-amplification/distortion problem had returned. I snuck in a probe to check the emmitor on Q2 again, and the voltage had dropped once again. What might be frying this part? Everything around it looks good, solder joints look solid, I'm not seeing anything obvious with burnt parts. My PS is working great, and my voltages seem good on the ICs. The diodes check out in circuit, but I have not yet pulled them to check them out-of-circuit.

Any ideas?

thanks,
Andrew

 

[OddHarmonic]

A few more details to add now that I'm at home at my bench. The output on pin 2 (U1) is way off from Peter's document. Instead of ~3 V, I've got 13.55 V. Also, the next stage in the chain is showing bad voltages as well.

On IC2, I'm seeing:

Pin1:-6.85 VDC
Pin2:-5.382 VDC
Pin3:-5.382 VDC

I'm gonna swap some parts for now, but I could use a pointer if anyone recgonizes anything from these problems.

thanks,
Andrew

 

[enthalpystudios]

quick question, maybe you know peter, as I think you have commented on the meters in question....

futurlec sells those little cheap vu meters... If I wanted to try hooking them up to the green pre instead of the leds, just to be a jerk and to have some bouncers on the frontpanel, is there a good place to hook one up? And can the led meter driving chip drive a vu as well?

I'm sure those meters aren't accurate, and I use my DAW input meters (and my ears) anyway..... this would just be for fun. I ordered some on a futurlec order just cuz they're cheap, so I thought I could try and use them.

billy

 

[fucanay]

I was at a friends studio this past weekend and we shot out the Green vs. a Wunder vs. a original 1073. We did this though a Neve console (8032 I think), straight to a Studer 827 Gold edition 2" 24 track. We monitored through Custom Chris Pelonis Monitors and amps.

We only did acoustic guitar, but it was enough to get an idea of what we were hearing. The results were that the Wunders are amazing. All three of us like that the best. But what was surprising is that we all liked the Green better than the original 1073. While the green had considerably less bottom, the 1073's bottom was so murky that it wasn't really an advantage anymore.

I don't think we ever bounced the clips to digital, but I'll say, I am VERY happy with the Green Pres. They hold their own with the best stuff out there. Except those Wunders. Wow.

Matt

 

[HappyTom]

Wunders?

HT

 

[fucanay]

[quote author="HappyTom"]Wunders?

HT[/quote]

http://www.wunderaudio.com/PEQ1product.html

Awesome.

 

[dissonantstring]

happy tom...look here.
http://www.wunderaudio.com/PEQ1product.html
a $400 green pre only bested by a $2.3K wunder audio pre? :green:

 

[Jonkan]

thats quite impressive, now ill get more motivated to get my greens up and running without the quirks im having right now.

/J