All things Green Pre

[pacemaker]

Hi Peter,
i've fired up my green pre ,built with ptownkid kits
I've  tested the voltage without any IC's, without gain switch and without signal
everything is correct except on pin 7 of IC1 and pins 1&2 of IC2,
all these are 4v, i've understood that the 3 are linked to the emitter of the first BC550,
i've desoldered the BC550, HFE seems ok ( 400) and i've tested continuity with my DMM,
Emitter to base is 0,7, collector to base is 0.7,
so i am thinking that the BC550 is ok ( maybe i'm wrong ...)
I've double checked the resitances,they all seems ok,
if anybody has a lead on how to locate the problem,
it would be really helpfull,
Best regard
pacemaker

 

[djn111]

Hi,

I think and I am not super familiar with the green amp, you can only test power supply voltage without ic's, if they are correct it is 90% safe to plug in the IC's and test the whole thing.

And maybe some fault tracing after that, or signal tracing for that matter.

DJN

 

[peterc]

Francois

Plug in the ICs & try it. The voltages can vary quite a bit with ICs plugged in.

Peter

 

[pacemaker]

ok, so 4v at the ouptut of IC1 is not a big deal ?
I have a lot of 5532,
so maybe i will try to put the IC's even if i risk to fry some....
i just have bought some BC550C at my local shop,
so i will also try to change them,
thanks for the advice,
regards,
Francois

 

[pacemaker]

and i forgot to tell
i am using a +16/-16v PSU i had for my Access 312,
this one is tested and run smoothly.
so the problem might not come from the PSU.
regards
Francois

 

[pacemaker]

Hi Guys ,
with Peter's advices, i have plugged all the IC's,
verified the voltages, set the CMRR, DC detector offset,
LED meter calibration,
and i've plugged my first microphone on it ,
It works like a charm !!!
So thanks a lot for you help,
specially peter for your help and boards,
and support to this forum etc,etc....
and thanks to ptownkid for his kits,
I hadn't time to test it with instruments,
but with my voice it seems very clean and detailed,
amazing project recommended to anybody
in the need of good and cheap to build preamps
best regards,
Francois

 

[Ptownkid]

Glad to hear you got it working!!! These pres are incredibly clear when they are working right. Rock on!

 

[KasperNyhus]

Hi

Im about to build a bunch of green pre's and Im wondering if I can squeeze 8 of peter's V14 PCB's + the 2 PSU's into a standard 2HE rack case? Has anybody tried that (maybe some pics )
I would like some ideas on how to make the front layout as well...

thanks guys and thanks peterc  

 

[pacemaker]

Hi !
i made a mouser BOM for this project,
normally everything is ok,
but you can verify if you want to be 100% sure,
mouser project code : e39bdd111b

regards,
Francois

 

[Basso Ostinato]

Hi everybody,
I'm trying to gather all the info to built a 4ch unit.

Hi !
i made a mouser BOM for this project,
normally everything is ok,
but you can verify if you want to be 100% sure,
mouser project code : e39bdd111b

Thanks Francois, I was comparing the mouser BOM with the _Green V14 bom.xls (the only one that I have found) and at first sight it seems to be different. What version of Green pre BOM is it?

And to everybody,
can anybody point me to the latest (or should I say, the best working?) BOM, schematics, PBC draws,  and anything raletad with the green? (some links in the META aren't working).
And also, what are you recommendations for the PSU, built one? or to buy a kit (jlm, fivefish)? As I said, I would power a 4ch unit, in a 110ACV region. 

Ptownkid, are you still offering the kits? I couldn't find it at you site.

Thank you!

 

[peterc]

http://www.mendelt.nl/greenpre_V14/

 

[Phrazemaster]

Hello gang,

After a 3-year (!) hiatus I am actually building a 4-channel Green! I already have the boards and a lot of parts, and lots of little parts on the way. So, I know I'll have some questions. Here's the first (for now).

I want to use an illuminated push button for the phantom power. I know this is probably blatantly obvious (newbie warning), but using a switch rated for 1A@30VDC won't work, right? It says 5A @ 125VAC, however.

I wanted to use this:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=UB226KKW016F-1JB-ND

But again, I think it won't work...thx in advance for thoughts.

 

[Phrazemaster]

Ah, or would this be better:

http://export.farnell.com/multicomp/d16-las1-1ab/switch-spdt-latching-18x18mm/dp/1736742

(and a lot cheaper!).

I'm assuming the switch has to be at least 48vdc as this is for the phantom pwr...thx any thoughts.

Mike

 

[Phrazemaster]

I think I can hear my own echo in here...anybody still making any green pres?

I have another question, which I have not found in searching. I am adding a lighted switch for phantom power (see posts above), but I'm not sure how to wire them. The lamp circuit is independent of the rest of the circuit, which means by applying power it will always be on. I only want the lamp to light when the button is engaged (ie there is phantom power).

Of course, I can connect the lamp circuit to the phantom power circuit, and using a 48v lamp it will light only when pushed; easy, right? But...that means the lamp is part of the phantom power circuit. Wouldn't there be some kind of problem with that? Would it affect the audio, is this a bad idea; is there another way of doing this using a relay/transistor/opamp that would be better?

Or should I try to find a DPST switch that would simply engage two separate circuits when the button is pushed and then use that second circuit for the lamp? Not sure I can find a DPST switch as I'm describing; the one I found before was really hard to find and it is ON-ON latching configuration.

Experts?

Thanks any thoughts.

Thanks gang.

Mike

 

[Phrazemaster]

OK I'm going with the concept of keeping the circuits separate, and I can find a DPDT version of the switch I am looking for, for a pretty good price. If I want to extend this for the HPF, it's easy since again there are two throws in the switch and I can use the second circuit for the lamp. Where it gets a bit tricky is for the Phase switch, since this already requires a DPDT switch and the switch I want to use only goes up to DPDT. In other words, I don't have another separate circuit to use for the lamp.

Any thoughts how to handle this? I really don't want to tap into the Phase wiring to use for the lamp...Or would this not be a problem? It's tough being a newbie.

Thanks,

Mike

 

[peterc]

Mike

I'd use the second switch.

It is pretty normal practice to use half a DPDT as a SPDT or SPST.

The phase is tough to adapt to get an indicator attached. That is one of the reasons I used toggles on this design. You could replace the switch with a DPDT relay & use a lamp for the indicator.

Peter

 

[Phrazemaster]

Thank-you Peter, I appreciate the insight.

I have spent hours pouring over datasheets...it's quite humbling, and sometimes frustrating...yet in the end I know it's all a learning experience.

Of course, I could just use the recommended parts, but what's the fun/customization in that?

Thank-you, i'll keep you and the gang posted on progress.

 

[Phrazemaster]

Hi Peter et al,

After many hours of "paying dues" as a newbie, studying all over everywhere, I'm wondering if anyone has an opinion if this board would work well for the Phantom, HPF and Phase switches? It will let me use an LED for each, but not have the LED be part of the circuit (important to the audio I believe?)

http://www.muzique.com/schem/bypass.htm

Does this look like it would be hard to adapt for the Green, would it draw too much current, etc? Obviously I would not be using the 9v battery, but would need to pull the power from the psu (would this be a problem for a bunch of these little boards?)...

Thanks any thoughts

Mike

 

[Phrazemaster]

Or would I be better off making some kind of relay driver myself? I'm up for it, but wow what a learning curve this all is! I'm looking into IC based designs, and scratching my head saying "all I want to do is see a little LIGHT!" But then again it's that last 20% that takes 80% of the effort, right?

And in anyone's opinion is it a bad idea to use a relay for these switches? Sound/quality degradation issues? The only reason is, I want to use a lighted switch and they don't come 3pdt for less than $70 EACH!!! So...this is DIY...lol.

 

[peterc]

Mike

The board would work for HPF, not sure about Phantom (48v might be too much for the relay) but would not work for the Phase switching - it is not setup for it.