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

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mnats

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Having trouble with this build? Read the 1176 FAQ.

In July of 2007 Ed and I started to converse about the 1108 preamp. I remember that it was a favorite of soundguy Dave. Ed pointed out that the 1108 preamp circuit was also used in the earliest version of the 1176 compressor.

I'd never noticed before that there was an 1176 with a totally different pre and line amp - one that had an FET as the first active element of each stage. Apparently there were very few made and are coveted by some big name mixers. Looking back I think Ed had hoped that I would make a PCB to build an 1108, but when I finally figured out there was a whole new (well, old really) 1176 then I had to make one.

In April of '08 I began working on the board in earnest and had it pretty much done in May. But Ed thought it would be nice to add some pads to make it easy to mount alternative coupling capacitors in the audio path. He said that the wound construction caps give a slightly different sound to the ones made with a stacked construction. Due to other commitments I didn't get back around to it until September.

Here's the finished board - in blue as in bluestripe - with Sprague Orange Drop capacitors:

click image to enlarge

Amazingly, it all worked first try (I did not prototype with a home etched board as I usually do). To me, it sounds more aggressive than the Rev D. I was worried that the pre-LN designs would be significantly noisier than the later models. In fact, this one measured only 3.4dB noiser than the 1176 Low Noise Rev D.

I'm totally happy with it and am looking forward to putting it in a nice case. Big thanks to Ed.

~The PDF file including BOM, schematic and self-etch files for the original version.
~My Rev A page (still in progress).
~BOM for V1.2 boards (earlier version).
~Documentation including overlay and schematic for V1.2.5 (currently supplied boards).
~I really suggest you make your own decisions about which components you use. Choosing components is more than half the fun. But if you can't be $&#*ed, Lab member spica has a post for you. I have not verified these components so the risk is yours. Note that this is not for the current V1.2.5 board but for V1.0-1.2.

Boards available here
 

BladeSG

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That looks superb, and I bet it sounds as pretty as it looks. :thumb:

Lets see if I get tempted..... Mmm that blue PCB is almost enough!

:guinness: :guinness:
 

Greg

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Nice work mnats!

I have used the Blue Stripe with the LN mod added. Great compressor. Would love to DIY one.
 

living sounds

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When you say more aggressive, do you mean this to be more in the Chandler line of things, kind of more coloured? Or is it an aggressiveness more of the VCA kind? Anyway, great job, obviously! It looks like this one has fewer parts than the later revisions, is this the case?
 

bernbrue

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Wow, that´s a great effort on a legendary compressor. It seems to be a quite easy built, hope there are not too much difficult to get parts in there. Would shurely buy a bunch of boards. The other day I visited your homepage, really interesting and profound information from a real expert.
Thx a lot
regards
Bernd
 

Vas

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Great news!!!!!!!! :guinness: :guinness: :guinness: :guinness: for all the great projects!!!
1176 is one of my favorites and you made possible own all the flavours/revisions!

thanks once more :thumb: :thumb: :thumb: :thumb: :thumb:
 

mnats

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My understanding is that the LN mod was applied to the bipolar versions, some of which also had a blue stripe.

The comment about "more aggressive" was with the compression switched off. I don't normally like to attempt to describe sound with words so I'm not going to try anymore. As for the parts count, you can take a look at the schematic yourself...the truth is out there.
...really interesting and profound information from a real expert.
:oops: Not really an expert except maybe in my actual profession of digital camera repair...BTW I got all the parts from Mouser except for the transformers.
 

Echo North

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These links are floating around, but here they are again for the people who haven't seen them:

http://www.uaudio.com/webzine/2003/august/text/content4.html
http://mixonline.com/mag/audio_revision_history/

Both examine the 1176 revision history in two different formats. You can see that the rev C (1st blackface) had LN circuitry mod added. This was before the circuitry was redesigned to incorporate the LN circuitry (rev D and on), but after the pre and line amp stages had been changed (REV B).

As Mako stated, it would be possible to see a rev B blue stripe with a retro fit LN mod...but that would be a different 1176 then the rev A with the fet signal pre-amp stage.

Mike
Who thinks if Mako isn't an expert...he must be pretty damn close! :)
 

mitsos

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Is this using the same in/out trafos as the Rev D?
 

Echo North

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I think the originals used "prototype" versions of the 600ohm UTC input (w/ T-pad attenuator) and the 5002A output.

So they were basically the same. The auction Mako mentioned includes Ed Anderson's in and out transformers and a state electronics attenuator.

Mike
 

martthie_08

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great work :guinness: it would be fantastic if you'd make boards available for this one, I'd love to build one and see what it sounds like.
 

Greg

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I just checked and I want to correct what I said earlier... I used a Rev B Blue Stripe with the LN mod. As others have stated, this is different than the Rev A mnats has here. So I have not heard the Rev A... sorry for the confusion.

But I would still like to DIY this one ! :guinness:
 

clintrubber

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[quote author="mnats"]In July of 2007 Ed and I started to converse about the 1108 preamp. I remember that it was a favorite of soundguy Dave. Ed pointed out that the 1108 preamp circuit was also used in the earliest version of the 1176 compressor.[/quote]
Just wondering to what happenend w.r.t. the 1108, would that be an interesting circuit on its own as well, or while at it then better go further and make it a 1176 ?

Regards,

Peter
 

mnats

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[quote author="clintrubber"]Just wondering to what happenend w.r.t. the 1108...[/quote]
If you take a look at the schematic you'll see it's all there (with minor modifications, some switching and the obvious mic pre bits missing) in the line amplifier of the 1176. Like I wrote earlier, there are footprints for the difference parts on my Rev A board so it should be fairly straightforward to make an 1108 out of the back half of my board.

Ed had an idea to bypass the first gain reduction FET and use the signal preamp stage (which is essentially the same as the line amp) as the front end of the pre. That way the 1176 output pot could be used to control the output without resorting to an external attenuator. There's lots of room for experimentation that I haven't had a chance to try yet.

If there's enough interest I have the idea to amputate the sidechain and metering circuit from the board so it is a preamp only.

Hopefully the auction will work well :wink: . Once I have a chance I will post the auction on Ebay. The various bits and pieces were scattered far and wide but most of it will ship from Hairball now - the boards are still with me and will ship from Australia.

All the proceeds from the auction will be donated to this forum; Hairball has kindly offered to cover shipping charges and has kicked in a set of knobs. I'll likewise cover shipping charges. Ed has donated the transformers and I have donated the remainder though Hairball has provided the other parts at cost.
 

clintrubber

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[quote author="mnats"][quote author="clintrubber"]Just wondering to what happenend w.r.t. the 1108...[/quote]
If you take a look at the schematic you'll see it's all there (with minor modifications, some switching and the obvious mic pre bits missing) in the line amplifier of the 1176. Like I wrote earlier, there are footprints for the difference parts on my Rev A board so it should be fairly straightforward to make an 1108 out of the back half of my board.[/quote]
Thanks for the info :thumb:

Googled for 1108-schematics but didn't find, despite I thought to have seen these... but I'll have a look at the relevant 1176.


If there's enough interest I have the idea to amputate the sidechain and metering circuit from the board so it is a preamp only.
Sounds interesting. Dunno where the 'magic' of all this is, in the amplification or when you go for the added 1176-functionality.
In other words: how interesting is the 1108 on its own ?

Thanks/regards,

Peter
 

mnats

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Really? I got this page at the top of the list from a Google search:

http://www.waltzingbear.com/Schematics/Urei.html

Maybe I'll have some time on the weekend to plug a mic transformer into the front end...
 
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