[BUILD] 1176LN Rev D DIY

The extra PS board should be the same for all revisions.

http://www.geocities.com/m_natsume/psu.html

Schematic download link in the upper left.

Mike

Aha!
thanks

Can I ask where you guys are connecting the 12v Sifam lamp to?  The G1176's had connections on the board, but I don't see one on the Rev D's.  I've read of a few different ways, like tapping off the toroid AC, but I'm not totally sure what is the best/cleanest/quietest way.

Thanks so much!
Sig

EDIT - Ok, so I've used the Toroid like most others have, and simply put a 180ohm resistor on the positive leg, and I get 12.1vAC, and it appears to work well and looks nice and bright.

Thanks!
Sig

Ummm...ignore that.  That was really bad what I did.  The light got REALLY hot after a minute, and then my meter jumped and peaked.  Can anyone please tell me the proper way to hook up the Sifam 12v lamp on these?

Thank you,
Sig

I remember Jakob saying using the transformer secondaries was the cleanest way of doing it.

For my unit I used the VU pads on the rev J board.  If I recall that voltage was about 30v (close to the transformer secondary, except DC I think).  I used two 2W resistors on each VU pin leads...I think they were like 180 and 150ohm.  You want to get closer to 11v so the lamp will last longer.  This is all from memory as I am at work right now.

You didn't use a 1/4 watt resistors did you?  They would get fried.

EDIT:  Oh I just see now that you said the REV D.  Doesn't have VU connections.  Sorry...probably best to ignore me

Mike

Well, I did use the transformer secondaries (right at the point where the signal enters the black Rev D board) but, I do believe this would be an AC signal, not DC, correct?

I was using 1/4 watt resistors, don't have any 2 watt that would work at all right now.  It's not that the resistor fried, but the lamp itself was getting hot so I disconnected it fast before it could cause any damage.  I don't understand though, if I'm reading 12.1v, it should be fine, no?  Or is the current too high?  Or should I not be using an AC signal?  Very confused...

Have a look here:
http://www.groupdiy.com/index.php?topic=14805.0

That would be AC but as the thread indicates, the lamp doesn't care.

My guess would be that you're killing the resistor (though it may not be visible) and it is acting like a wire...loosing its resistance.  I could be wrong though.

You should definitely get a bigger resistor on there.

Mike

Here is Jakob's original post:

http://www.groupdiy.com/index.php?topic=275.0

Ok, I'll check this out...

So, in doing the calibration, I used the 2 videos from Mnats - totally RAWK!  Piece of cake, and it's never been easier.  These Rev D's sound much better than the G1176's, no hum problems, loooooads of level.

However, the 3rd video is not up yet, so I used the doc that I found from Nimbleswitch for Adjusting Gain Reduction.  I found that after setting level, I couldn't get the meter to show -10dB of GR, it was always still under.  I swapped the 2k trimpot with a 5k and it worked great.  I'm assuming that this is ok?  I then had to readjust meter zero and null for the initial 0v settings. 

Thanks again!
Sig

Ok, so I don't have any 120 ohm 2W resistors - all I had were 1.1k 2W, so I put 4 of them in parallel which gave me about 280 ohms, close to where it should be.  The voltage at the meter light is 8.1v, making it a little dim, but it actually looks pretty cool that way.  But DAMN, those suckers get HOT!!  Is this gonna be ok to run like this?  I mean, it's hotter than the heat sink...

Thanks,
Sig

Mine get pretty hot.

You have to remember that the resistor is taking the excess energy and releasing it as heat, so if you're dropping 30v down to 8v...that's a fair bit of heat.

Keep in mind I only *think* I know what I am talking about.

Mike

Ya, I pretty much don't even think I know what I'm talking about most of the time.    I'll leave it for now and watch it, see what happens, fry some eggs if I get hungry.

So, it feels to me like I have a lot of level in and out of this thing.  I think I'll wait til Mnats has that last video up before I close these guys up and put them away.  The calibration went so well with his videos, then with that document for the last step I felt like I was wrecking it again...

Thanks for the help,
Sig

Excellent work!

I need to build a rev D myself...it's ironic that I haven't yet when I'm surrounded by boxes of attenuators, transformers and parts. 

Mike

Hey Sig,

What I've done in my 1176 VU's light, was put an extra small transformer (220 to 12V) with 2VA (that costs around €3), a couple of diodes to rectify and a 1000uF cap. I know, I know... maybe that is a little bit only to light up the VU, but I'm always a little bit affraid of wiring the lamp directly to the secondary of the toroidal... the lamp is small, but 12V with 1.3W gives you around of 0,11A of consuption... is not too much, but, with some resistors like you did or some Zenner Diodes the things got really hot, hehehehehe... I really like to separate the things althrough you have one incovennience... the light's flickering made by the Toroidal's AC voltage (if you have wired directly to the trafo's secondary)  :-\ in the "studio's darkness" you need a steady light, one that will not flicker at all! makes a lot of difference when you pass hours looking at those things

Hey Mike, talking about the transformers! I ordered you a EA5002 Output Trafo a few minutes ago  ;D

Cheers

Eddie ;D

Ya...overkill dude haha.  I think with those resistors I've put in, things are great so I'll just leave it at that.

However, I have now done the calibration and everything is perfect, no hums, no crap - the Mallory T-pads are a bit scratchy, but they sound vintage that way haha.

The only problem I have is that there is toooooo much level coming in.  The input is rarely over 9 o'clock with tracks coming from Pro Tools, and I usually put a trim plugin before the insert to turn it down so it's not hitting the 1176 so hard.  What can I do here to fix this?  I am using the Mallory T-pad with Cinemag ins and outs.  What might be causing this?

Otherwise, very nice units, and sooo different from my G1176's - all are good though.  I plan on doing a pair of the Rev A's and single Purple MC76, should be a nice set when they're all done.

Thanks!
Sig

Hey all,

I Have a question  :-\
I matched the FETs as descibed, all ok, but when I tried to select the 2N3707 with the HFE > 250... man, I bought 20 of them, NONE has HFE > 250, can you believe that? the maximum I get was 237  damnnn! I stuff 2 of them for the ones that need to be matched, with HFE=220 both, stuff the one with HFE=237, and I would like to know if I can stuff 2N5088 for the rest of it, because I read that they are used in the MC76, and could be used in this project version, and sure they has the HFE over 250, like 475 or more.
I need to know if I can use that, or if I dig to use those, may I need to take off the 2N3707 already stuffed?
Well... thanks a lot!

Cheers,

Eddie  ???

Helloo... could anyone help with that above?

Mako are you there??

Cheers,

Eddie  ;D

Not to step on your toes Eddie, but I'm also wondering if anyone has come across the too much level problem with the Mallory T-pad and cinemag ins and outs.

Thanks!
Sig

SaMpLeGoD said:

Helloo... could anyone help with that above?

Mako are you there??

Click to expand...

I don't get it - do you want permission to do what I suggest on my Rev D page?

Rev D Page]Q7 through Q10 must be selected for an hFE of 250 or above. Additional transistor footprints have also been provided to allow for the substitution of alternate devices for Q7-Q10 in the Gain Reduction Control Amplifier such as the 2N5088 used in the Purple Audio MC76.[/quote] [quote author=SaMpLeGoD said:

may I need to take off the 2N3707 already stuffed?

Click to expand...

You will have a hard time putting in the alternate transistors if you don't.

Siegfried Meier said:

Not to step on your toes Eddie, but I'm also wondering if anyone has come across the too much level problem with the Mallory T-pad and cinemag ins and outs.

Click to expand...

What is the ratio of the Cinemag?

Hello mako,

My PCB has no alternative footprints for that transistors, only for the 2N3037... sorry for asking that, I'll swap Q5 to Q13 with 2N5088.

Thanks

Eddie  :-\