Inserting Pico Comp in Green Pre circuit +Switch Question?

[fucanay]

I want to combine my 2 channel Green Pres with a couple of Pico Compressors. The Pico Comp is unbalanced in and out so I thought I might be able to balance the output with the Green Pre.

I can't seem to locate the schematic for the V14 Green Pre, seems like the only ones around are older. So I thought I'd ask if anyone knows if it's possible to insert the unbalance Pico Compressor into the Green Pre before the Green Pre goes to the balancing part of the circuit.

On another Green Pre subject, and maybe PeterC will comment, I would like to eliminate either the gain or output trim pot for front panel space savings. Would I just need to find a resistor value high enough to supply enough gain to replace the stepped lorlin? and then only use the output trim for adjustments while tracking? Has anyone else done this to eliminate a knob from the front panel?

Thanks in advance,

Matt

 

[fucanay]

I thought people would be more interested in this since there are so many Green Pres and soon to be Pico comps out there. Maybe not? Is this a shameless bump?

Matt

 

[Mbira]

I was going to point you to the new schematic, but why not just use the old one if you want to eliminate the trim control?

 

[peterc]

Fucanay

I'd take out the output trim control, that was put in for a client & stayed. Leave in the stepped gain control.

This is where you could also put in a Pico, nice idea.

Peter

 

[fucanay]

[quote author="peterc"]Fucanay

I'd take out the output trim control, that was put in for a client & stayed. Leave in the stepped gain control.

This is where you could also put in a Pico, nice idea.

Peter[/quote]

Thanks Peter. The reason I wanted to dump the stepped control was that the Lorlin switches are kind of crappy. Maybe there is a better Brand of switch I can buy. Teh regular Lorlin switches seem fine for power on/off and bypass and things like that, but for something that gets used as much as the gain adjustment, I don't like those switches at all.

As far as inserting the Pico, I'm not sure I understand about inserting it there. The stepped gain switch is essentially acting as a resistor correct? If that is the case then where would the ground come from to hook up to the pico? Or would I just run a wire from the center of the switch to the input of the Pico and leave the ground pad disconnected? And then from the output of the pico to the other side of the 2 pin plug on the Green Pre.

Yes, these are kind of dummy questions. I'm real good at soldering, but some of this theoretical stuff gets over my head pretty quickly.

Matt

 

[peterc]

The stepped gain is a resistor, but effectively in a pad configuration.

There was a recent thread here in which Jakob championed the Lorlin switches for their quality. They do feel a bit cheapo but I like them for the price.

Have a look at the cct:
http://www.mendelt.nl/greenpre_V14/_Green_trim_HPF%20CCT.gif

The output of the preamp/HPF section is on S2, the input to the balancing stage is from the pot wiper into R45.

So S2 goes to the input of the Pico, the output of the Pico goes to R45, & connect the Pico Gnd to the Green Gnd.

Peter

 

[fucanay]

Ok, I think I get it.

So it would look something like this once the output trim was removed, right?

Also, I only have 2 Green Pres in the box. It shouldn't be a big deal to power the 2 Picos off the same PSU (your design) should it? Maybe just add some heatsinks to the regulators?

Thanks a lot for the help Peter.

Matt

 

[peterc]

Looks good, Fucany.

Send me a Pico PCb & I'll tell ya! :wink:

Peter

 

[fucanay]

[quote author="peterc"]Looks good, Fucany.

Send me a Pico PCb & I'll tell ya! :wink:

Peter[/quote]

I knew I should have bought 5 of them.

As for the Lorlin I was talking about earlier, maybe I just got a bad one. It gets in a position where it cuts out the sound all together sometimes and I have to wiggle it to get it to work. And it does feel cheap. And I know people like them, but is there another brand that hooks up the same way that feels/is a bit more durable?

These Green Pres were my first project so everything is a bit sloppy inside the box, so I'm going to redo most of the wiring while adding these Picos into it. And a new front panel while I'm at it.

Matt

 

[fucanay]

[quote author="RogerFoote"]Matt
You will have to run the pico's 0V gnd over to the green as well. It is marked Gnd (Between the V+ and V- pads).

Oh, also, the Lorlins are way better build than ITT rotaries. I tried them and the solder pins would come loose while trying to insert them into a PCB. The Lorlins are "staked" where the pin enters the switch body, eliminating that problem. Digikey was unhappy about me returning $100 worth of them. Their tech said "I see no problem with these" which pissed me off pretty good. Well, there is no problem as long as you don't need them to work correctly![/quote]

So the 0V need to go to which place on the Green? To same place as the +15/GND/-15 is on the Green board? I haven't opened the Green Pre case yet, so i don't remember how everything is wired. I'm going to pick it up from a friends house tonight and get it opened up.

And oh well, I guess I'm stuck with the Lorlins. I'll see if I have any extras, but I may need to order some before I can finish that channel up.

This is going to be a pretty cool box if I can get everything going.

Thanks again guys.

Matt

 

[peterc]

The best place for the Gnd connection would be at your star ground point in the case.... Should help avoid loops.

I've also used the Alpha switches with success, they feel a bit smoother than the Lorlins & I know that NYDave has liked them as well.

Peter

 

[AnalogPackrat]

And if you can live with only 11 positions, CTS makes a nice shorting switch. Digikey sells them for under $8 a pop. I used them in my 312ish project. They are quite stiff and well-made. You can see them in my photos if you're curious (check the new gallery meta).

Digikey part number CT2122-ND

A P

 

[fucanay]

Thanks Roger

They are flying wires, so your higher quality brand suggestions are appreciated.

For the sake of this threads completion in regards to questions asked and answered, I'm going to link to the 'Wiring the Lorlin for Green Pres' thread in the Green Pre Meta.

I'll look into finding a greyhill or electroswitch rotary switch that will work.

Once again, thanks guys. Hopefully in the next week I'll get some of this stuff done. I've had a family emergency that's prevented me from doing anything other than posting here for the last couple days, but everything is getting better so I should be able to wire this up soon.

Matt

 

[fucanay]

Just when I thought I was out of questions, I have one more.

I just found a grayhill on digikey that looks ok, but I'm unsure about the amp rating requirements on this switch. The one I found is 200mA, but it's less than $11, so it may be worth it if it will work.

EDIT: BAD PART NUMBER REMOVED

Can someone tell me what the amp rating needs to be for the switch?

Also, a thanks to AnalogPackrat. I found another CTS on digikey that looks like the same thing, but with 12 positions. EDIT: BAD PART NUMBER REMOVED

I think I'm pretty determined to get better switches in this thing. The Lorlins work great for the GSSL and the G1176, but I'm not liking them at all on the Green Pre. I must be crazy too, cause I hated soldering those resistors to that switch.

Thanks

Matt

 

[AnalogPackrat]

The 11 pos CTS is shorting, the 12 pos is not. All the grayhills that DK stock are non-shorting. I think you can special order the shorting types with long lead time. I'm not familiar with either the Green or Pico, so you'll need to find out whether you need shorting switches or not.

Also, note that the CTS switches with solder lugs just barely fit in a 1U ParMetal chassis--you have to bend the solder lugs back (they flare out radially) to get it to fit. No big deal--just a heads up.

A P

 

[fucanay]

Bah, yeah, I just figured the whole shorting thing out while reading another thread. The Green does need a shorting switch. None of these seem to be shorting except the CT2122. And the big reason I kept looking for another one was because of the way it flares out. I think it's going to be a pretty tight fit on the front panel as it is and the grayhill seemed so much smaller.

Gotta think on this a while, no point getting a different switch if I can't fit it all in the case.

Matt

 

[peterc]

I would think you can use a non-shorting switch, with an open cct the volume goes down in this design. So you will get a jump in volume when changing the switch position, but at least it is down & not up to full volume.

Peter

 

[fucanay]

Thanks Peter,

It's good to know I could use one, but the behavior you describe sounds pretty annoying. Like a drop out between positions, right? Which is probably why you specified a shorting switch in the first place. I guess the Lorlin really is THE choice for this application, without spending a ton of money on hard to find switches.

I guess I need to order some new ones that aren't defective. Bah.

Matt

 

[fucanay]

Maybe I should just try it then. If it ends up being annoying, it will be what it is, but with better switches. Looks like I should get a digikey order together.

Thanks again guys.

Matt