[BUILD] 1176 Rev A - Back to the beginning...

Actually I will look into the pops when I get free with my limited knowledge. But will be another week until I am free.

Doesn't effect me actually cause I rarely use that effect...

John

Stagefright13 said:

Guess what? the REV A is ruling the show! Thanks MNATS! It's sounds great.

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i'm soooo glad to hear that!
I'm still stuck with mine.
I built a pair, each in their own case using rotary switches and the on-board power supply. Each suffers from the same set of problems. They pass audio and seem to be doing some limiting.
The 30 volt rail measures ok for both them, but the negative rail measures -8.7volts; is that close enough?
I can't calibrate either of them. When following step one of mnats video, i cannot get the output higher than about -3db (i'm using a sifam al29wf meter, but i also checked with an external meter).
i used this 'http://www.geocities.com/m_natsume/1176_slam_mode_rotary.html' for my ratio board, could that (done incorrectly) be a source of problems? Should i just buy the lorlin switch for the ratio board and forget about slam mode (in truth, i'm not much of a 'slam' fan)?
i switched some of the transistors to no avail: i started with 3707s where high hfe wasn't needed plus 2N5088s elsewhere. i tried switching the 2N5088s to 3708s (didn't do much), then i swapped out the 3707s so that Q3, Q5, Q7-10, Q12 and Q13 were all using 3708s.
I did not match q1 and q11. coming from the same batch, could they be so grossly mismatched that they'd prevent proper calibration?
I also noticed most people with photos of completed revDs/revAs were using an electrolytic cap for c17 (1uf), i used a wima film cap. could that be a problem?
i'd really appreciate any advice on what to try next. thanks.

The Rev A doesn't have an "on board" power supply. Maybe you have a different compressor. The original revision designations are not the same as some of the DIY ones. But some are.

Hi. My list of problems was a bit of jumble. Sorry about that.

What I meant to say is that I built a pair of compressors with mnats' blue revA 1176 boards, each in a separate 2U chassis. I used the power supplies built onto the main boards as opposed the separate supply he furnished.

[quote author=mnats]A power supply is built into each main board. Use the separate power supply to power two or more main boards from the same supply.[/quote]

I used Avel Lindberg Y236206 25+25V @ 50VA power transformers.
In both of the units, the DC voltages measure +30v and -8.6v.

Each of the 2 that I built presents with the exact same problems:
I can't get the VU meter past -3db for step one in the calibration video. I did try just leaving it there and adjusting the q bias for a 1db drop, which worked. But the 'calibrating the meter circuit' step didn't work at all.

Oh I see what ya mean I was thinking like the GSSL with the power transformer on the pc board. Dummy me.

-8.7 seems low to me. Did you check all the resistors in the power supply section?

I think I had to fiddle with the trimmers at first to get mine to even measure anything on the meter. Even after goofing with the trimmers it still won't go above -3 DB? You should be able to trim it up WAY above zero. I would check the resistors on the meter board for starters. And would look into the low negative supply. Maybe you have your meter light hooked up to that side and it is sucking down the voltage? I personally used 30/30 50VA torroids on all 3 of my Mnats compressors. Cause they were cheap enough. But most people I believe use the ones you have. And don't have a problem. If ya do try the lorin and have any trouble and mess up the switch boards let me know. I have 3 sets of rotary switch boards that I didn't use. I can send you a new set. Or even if you want to make a lorin switch board and just swap the whole assembly out.

Mine was confusing a bit when I first fired it up and I had no gain reduction measuring at all. But after messing with all the trimmers a bit I got it 100%. I had to go back and forth between the zero adjust and R44 I believe several time to get my meter to rise. And then adjusted the bias trimmer 'till it maxed out. then did the 1 DB drop...

Hopefully someone can be of more help.

John

Hey Ethervalve, I have a similar issue. I've built both a G1176 and a RevA will great success. Both work and sound great, the revA is pretty special. Anyway, I'm trying to build a second G1176 and I'm experiencing the same issue with the meter. I can't get the gain reduction meter to reset over -3. I have changed all the Fets with no luck. My voltages are perfect a +30 and -10V DC. It's just like my first G1176 with a rotary slam mode. Is your unit compressing? Does the ratio switch work? I'll keep plugin' away on my end.

Siegfried Meier said:

0dbfs said:

I've got a complete BOM that I will post once I go back through and check a couple items.
I have seen it mentioned that electro's should be rated close to operating voltage instead of over-rated. Does this matter? Ie; using a 100V electro in a position that will not exceed 35V (better to use an electro rated closer to 35 + a couple)?

Thx,
Jonathan

[EDIT]
Here is a BOM I put together to help myself understand all of the components:

http://diy.dbfsforge.com/mnats_d1176/mnats_1176_revA_BOM_DUAL_jonathan-burtner.xls

I referred both to the schematics, the boards, and various other threads.

Please be sure to check that these components are adequate for your particular needs before ordering.

Shoot me an email or PM if you find there is anything worth changing and I will update the list with a new version.

Cheers,
jonathan

Click to expand...

Anyone ordered from this yet, and have noticed any issues?

Thanks!
Sig

Click to expand...

Hey Sig,

I have ordered and am stuffing now...

I have found that the mouser link for R42 (should be 182k precision) is really for 182R.. Oops!

The correct mouser link is:
https://www.mouser.com/Search/ProductDetail.aspx?R=RC55LF-D-182K-B-Bvirtualkey66200000virtualkey66-RC55LF-D-182K

They are on backorder now and expected in 3/5/09...

I'll update the BOM when I get a chance and add any other required changes to it.

Cheers,
j

Cool 0dbfs your keeping up on the BOM! My rev A has been on since last week recording. Very reliable. And very stable except the 1 DB meter climb like the originals. Haven't noticed any extra noise at all from the rev D version. But have used it on 57's against the grill for guitar and a snare drum top.

Takes a long time to test something out. So far so good. Think this CD will be the first using the rev A. Correct me if someone else made an album using it.

John

I used push buttons and calibrated fine. I used push boards from Mike at hairballaudio. And the REV A is different resistorwise from the regular rev D.

How is the RevA different? I also used the Hairball boards and switches. I love my RevA except the "all buttons in mode," which we talked about earlier. Maybe I'm using the wrong resistor values on my ratio board? Would you be willing to share the values you're using? Thanks.

"All Buttons In" mode should sound distorted by nature. 

You can check the resistor values by looking at the schematic here:
http://www.geocities.com/m_natsume/1176_revision_a

Or I can send you the updated pdf I have for my boards.  Just send me an email if you want that.

The 10M parallel resistor does not appear on the original schematic.  I believe it was added to later revisions to stop "popping" when selecting ratio values.  If you think it is causing "ABI" to sound off you can always replace it with a jumper (making it like the original).  But ABI should sound off...and the meter should peg right (if you are not familiar with it).

Mike

Mike at Hairball audio included great docs with the switch boards. He has 2 different pics. One for rev A and Rev D. The problem is there are pops on plosives. Such as when the compressor clamps down a quick signal. Not a distortion problem. The original documentation actually states if you get pops to reduce the attack or release control. In nuke mode who knows!??

I may try that tomorrow jumping the 10 meg and see what happens.

John

Hey Mike, thanks for the response. I am very familiar with the nuke or Brit mode on the 1176. We have two blue stripes and LNs at work. What I'm experiencing is just like Stagefright13 explains, plovsives. I'll try the jumper tomorrow and post.

Did ya try it yet Orangerec? I'm afraid to make any changes while I am still tracking. I am almost up to lead vocals and wanna put the rev A in the choices...

John

Sorry for the delay. I had an unexpected session pop up. Anyway, I removed the 10M resistor off the ratio board and it didn't fix the nuke plosive problem. It actually made the 20:1 ratio unusable, exhibiting the same problem as the nuke mode, with the plosive problem. I double checked all my resistor values and all are correct. This is not that big an issue. I don't want to discourage anyone from building the RevA. It sounds fantastic! I'm just a perfectionist. 

Have you tried refering to the urei 1176 schem for resistor values on the ratio switches? They appear to be slightly different to mnats version. eg. mnats R63 - the 1.2k is a 2.7k in the urei.  mnats R58 - 180 is not there in the urei.  And of course the 10M which is well documented.

Not sure if this will solve any (or cause) problems.

I remember there were a few different rev A schematics floating around and they did differ.

I *think* I remember Mako recently posting that his version is based of the rev AB which did have a number of resistor changes to improve noise.

Mike

Check it out here:
http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/UREI-1176LNmanual.pdf

The second schematic labeled "A" which I believe is actually the AB has the same resistor values as the MNats A.

Mike

Looking at the schematics I believe mnats resembles the 1st unmarked urei schem. rather than the schem labled "A".  Just on initial inspection. eg. the 8.2k rather than 4.7k at the top going to the T2 black.
Also around Q2 and Q5.

If the ratio boards are based around the rev labled "A" then there are still a couple of differences with mnats.  Not sure if they're could be causing the plosives though.