PRR-176 Vari-Mu REV 2 - *Group Buy 7/13!*

[Holger]

No secrets here, I used transparent foil for overhead projectors.

 

[Edward]

Do I ground the PSU pcb from pin 4, which is the CT? Is that the only connection to ground needed from the pcbs?

 

[ilfungo]

with vu meter I can not get a correct reading of the compression
this might work?
Thanks


http://www.ebay.it/itm/PM-2-1MA-MOVING-COIL-METER-1MA-/130753131630?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item1e717e746e

 

[earl]

@ Edward : Abe says ground from one of the smoothing caps down the line from ct.
EDIT: Thinking that was the rev 1 version where i read that. 

 

[Dr_J]

Hi Ifungo,

yes 1mA meter would do the job.
But what's the problem with your VU meters? They have to work too, have they!?
Maybe you just need to make a new scale for them!?
Check out my post in the REV 1 thread.

ROCK-ON!

 

[ilfungo]

Thanks Dr_J
I don't know how to make a new scale for VU Meter....
Can you help me with some info?
Thanks!!!

 

[abechap024]

Do I ground the PSU pcb from pin 4, which is the CT? Is that the only connection to ground needed from the pcbs?

What do you mean exactly? You don't need to add anything. The only connection you will need to "ground" (connecting the audio ground to chassis ground) will be at one of the input XLRs (you have all the pin 1s of all your xlrs connected directly to chassis at the xr right? ) and you only connect any of the XLR pin 1s at ONE and only one xlr to the respective pin 1 on the pcb.
Hope that helps


Abe

 

[Edward]

Do I ground the PSU pcb from pin 4, which is the CT? Is that the only connection to ground needed from the pcbs?

What do you mean exactly? You don't need to add anything. The only connection you will need to "ground" (connecting the audio ground to chassis ground) will be at one of the input XLRs (you have all the pin 1s of all your xlrs connected directly to chassis at the xr right? ) and you only connect any of the XLR pin 1s at ONE and only one xlr to the respective pin 1 on the pcb.
Hope that helps


Abe

I was reading the rev 1 thread and somebody was writing about that... From now on I will try to stick to the plan and stop trying to figure out stuff by my own as it usually turns out horribly wrong. Thanks again.

 

[earl]

Hey Abe 1 channel of sonic bliss complete... squishy aggression.  Sounds of glory.  Thanks for making this truly unique project available.  Using lundahl's and 2520's.

 

[abechap024]

Do I ground the PSU pcb from pin 4, which is the CT? Is that the only connection to ground needed from the pcbs?

What do you mean exactly? You don't need to add anything. The only connection you will need to "ground" (connecting the audio ground to chassis ground) will be at one of the input XLRs (you have all the pin 1s of all your xlrs connected directly to chassis at the xr right? ) and you only connect any of the XLR pin 1s at ONE and only one xlr to the respective pin 1 on the pcb.
Hope that helps


Abe

I was reading the rev 1 thread and somebody was writing about that... From now on I will try to stick to the plan and stop trying to figure out stuff by my own as it usually turns out horribly wrong. Thanks again.

Hi Edward,
Sorry I know its pretty confusing!

 

[abechap024]

Hey Abe 1 channel of sonic bliss complete... squishy aggression.  Sounds of glory.  Thanks for making this truly unique project available.  Using lundahl's and 2520's.

Thanks for the kind words Much thanks goes to PRR though, hes the mastermind behind the original idea. I must agree, these units do sound nice!

 

[sedit1]

Hi!

I'm having a problem with my power transformer(s) 230v

I have 2x25vac and 2x15vac toroids.

I've connected one 24vac secondary to 15vac secondaries witch are connected in series and I get 260vac am I doing something completely wrong here?

Thanks!

 

[abechap024]

Hi!

I'm having a problem with my power transformer(s) 230v

I have 2x25vac and 2x15vac toroids.

I've connected one 24vac secondary to 15vac secondaries witch are connected in series and I get 260vac am I doing something completely wrong here?

Thanks!

Do you have the 15V transformer the one that is connected to the mains? Also maybe measure each transformer to be sure of the voltage they are putting out.

 

[sedit1]

Hi!

I'm having a problem with my power transformer(s) 230v

I have 2x25vac and 2x15vac toroids.

I've connected one 24vac secondary to 15vac secondaries witch are connected in series and I get 260vac am I doing something completely wrong here?

Thanks!

Do you have the 15V transformer the one that is connected to the mains? Also maybe measure each transformer to be sure of the voltage they are putting out.

Thanks Abe,

The 2x24v is connected to mains. Transformers measure 2x24->28vac 2x15->18vac. I've connected them like in the g9 picture http://i73.photobucket.com/albums/i222/skylargray/G9/G9Toroidconnections.jpg

I think that might be the problem? Because I was just testing this with tx's what I have at home already but they are just single primary straight to 230v. So I think I need the 15vac to be dual primary and also connect the "new secondary" in series?

 

[abechap024]

Well if you have the 24V connected to mains, and then connect that to the 15V transformer your going to get more that 230V on the output. Which for the G9 is fine, but this project you only want 120V or so.

When you apply 15V to the secondary side of the 15V transformer  you will get the spec'ed 230V on the primaries. What happens when you increase the voltage on the secondaries? The voltage will raise faster on the primaries. So if you apply 24Vs to the 15v transformer its no big surprise you are getting more than 230v right?

(I know the whole "secondary" and "primary" is a little confusing because we are flipping the transformer around and essentially using the primary and the secondary etc etc, don't get confused its all the same to the power transformer!)

So then applying the same logic to the 24V transformer. When you apply roughly 24V on the secondarys of the transformer you get roughly 230V on the output, right? Since we want a little more than half that voltage, we'll apply a little more than half that on the secondaries. Wait, you still have that 15V transformer right? That will be perfect.

Make sense?

230::15::24::150ish

BE SAFE!

 

[sedit1]

Well if you have the 24V connected to mains, and then connect that to the 15V transformer your going to get more that 230V on the output. Which for the G9 is fine, but this project you only want 120V or so.

When you apply 15V to the secondary side of the 15V transformer  you will get the spec'ed 230V on the primaries. What happens when you increase the voltage on the secondaries? The voltage will raise faster on the primaries. So if you apply 24Vs to the 15v transformer its no big surprise you are getting more than 230v right?

(I know the whole "secondary" and "primary" is a little confusing because we are flipping the transformer around and essentially using the primary and the secondary etc etc, don't get confused its all the same to the power transformer!)

So then applying the same logic to the 24V transformer. When you apply roughly 24V on the secondarys of the transformer you get roughly 230V on the output, right? Since we want a little more than half that voltage, we'll apply a little more than half that on the secondaries. Wait, you still have that 15V transformer right? That will be perfect.

Make sense?

230::15::24::150ish

BE SAFE!

Thanks Abe this makes perfect sense!

This was just testing the technique. My main Idea was that I would order 1x18v and 1x12v dual primary toroids -> 230::18vac::12vac secondaries in series::172.5vac (new secondary in series)
Then I would still have the other 18v winding for my 18vac input.

Does this make any sence or would it be just easiest to buy 230->115vac toroid and also use 2x18vac for 18v?

Thanks!

 

[abechap024]

Does this make any sence or would it be just easiest to buy 230->115vac toroid and also use 2x18vac for 18v?

Thanks!

You could use both ways. Though getting a separate (or a transformer with the correct taps) for 115V would be best.

 

[ethervalve]

Hi all,
Just got mine together and turned it on, psu voltages are ok but I need to do a bit of troubleshooting.
I'm a little confused by one thing in the schematic (incidentally, is the Rev1 schematic still OK to follow for Rev2 boards?):
when using the IC input option (which I'm doing), do I just jumper the OPT_1 and OPT_2 pads? Or do any of the transformer pads require bridging?
Thanks in advance

 

[abechap024]

Hi all,
Just got mine together and turned it on, psu voltages are ok but I need to do a bit of troubleshooting.
I'm a little confused by one thing in the schematic (incidentally, is the Rev1 schematic still OK to follow for Rev2 boards?):
when using the IC input option (which I'm doing), do I just jumper the OPT_1 and OPT_2 pads? Or do any of the transformer pads require bridging?
Thanks in advance

You still need the interstage transformer, or the 2 interstage transformers per channel. 4 total for the board. then you bridge both "in-ops" if your using the chip input as apposed to a t-pad attenuator. And yes rev 1 schematic is still good.

 

[ethervalve]

ha, I'm a buffoon. Thanks Abe. The one channel I have enough transformers for sounds great! (Seems to make cymbals sound a little nicer than are in reality; also really get's that 'September Gurls' comp'd guitar sound nicely).

edit:
I love this thing enough that I'm mulling the idea of building a second one next year. Have any of the earlier builders noticed if the threshold calibration remains stable over time? I ask this because I'm thinking it would be cool to have a 2 or 3-way switch with different calibrated threshold settings. In my case I'd be using it 75% of the time as a console insert (nominal -10dBu) and the remaining quarter of the time connected to +4dBu 2-track outs.
Also, have any of you who used the hairball/nissei meters tried replacing the scale? I'm OK with it as is, but it would be interesting to know if scale modding worked out for anyone.