pvision

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #20 on: May 04, 2018, 06:51:20 AM »
The switches are the same between 76 & 78 in the sense of what they do (with the caveat that the bottom right hand switch is a peak / average switch on the 78) and the fact that the buttons don't latch simultaneously - pressing one released any latched button. This is what I mean by non-latching

The 78 was built as a dual channel / stereo limiter rather than a dedicated stereo limiter. The distinction is a bit moot as the attack & release controls are common so I imagine the A/B / stereo switch only affects some parts of the sidechain linking

I assumed the 78 would have different switches as it has two channels. However, I had a quick a look at the differences between the sidechains of the 76 and 78. The 76 has two-pole switches for ratio, and switches signal & sidechain. The schematic suggests the 78 uses a different setup with the same switches as the 76 but switching L & R. The schematic I have doesn't show the RH channel so I can't be sure. A photo of the inside of a 78 should give the answer

Looks like UREI did some clever work adapting the 1176 into the 1178

Nick Froome


PRR

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #21 on: May 04, 2018, 12:45:21 PM »
> seems like a legit store to me

You can find the address in Google Maps Streetview. Not a "store" but a large house in the Belgian woods a few minutes away from the Dutch border. Very large garage.

This makes sense. When a chip is new sales may be good. (And maybe not.) Distributors order a whole box. 5 or 10 years later the box is part-empty and sales have fallen-off to nearly none. A busy distributor can't keep heaps of slow/no-sellers in inventory. He'd rather sell them for pennies to buy newer chips that will sell fast. But there is a long-tail of demand. B-52s and paper-mills and other strange machines keep running long after their guts are "obsolete" and sometimes need replacement parts. And a part that sold for $2 in 1985, for $0.50 in 2001, in 2018 you may be able to jack-up to $12 for a customer who NEEDS just THAT part to keep a $1M (even $1K) machine running. It's not a big business, and customers can be anywhere, so it could be run from a house.

Is a very nice house.

Zebra_PD

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #22 on: May 05, 2018, 10:21:56 AM »
assumed the 78 would have different switches as it has two channels. However, I had a quick a look at the differences between the sidechains of the 76 and 78. The 76 has two-pole switches for ratio, and switches signal & sidechain. The schematic suggests the 78 uses a different setup with the same switches as the 76 but switching L & R. The schematic I have doesn't show the RH channel so I can't be sure. A photo of the inside of a 78 should give the answer

Looks like UREI did some clever work adapting the 1176 into the 1178

Nick Froome

Here is some pics of the inside of an 1178 :)

https://www.proaudioeurope.com/info/wp-content/uploads/2016/08/Urei-1178-Inside.png

https://www.proaudioeurope.com/info/wp-content/uploads/2016/08/Urei-1178-Inside-2.png
Kind regards,
//Pierre
___________________________________________________
Semiprofessionell producer but newbie DIYer.
----------------------------------------------------------
www.zebrastudios.se

pvision

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #23 on: May 05, 2018, 04:23:46 PM »
From the photo it's clear that the 1178 has a wider chassis than the 1176 which is why the 1178 front panel doesn't line up with the bolt holes on other Urei chassis

Looks like the switches are the same on 76 & 78 models

Just in front of the output transformer for channel B you'll see a nicely-symetrical layout of an IC, two trimpots and two electrolytics. I think those are the dual FET, the Q bias controls and the audio caps feeding into the FET

Nick Froome

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #24 on: May 05, 2018, 06:22:18 PM »
Perfect! I'll prob make an order within the next month or so. Just need to plan the rest of my BOM to see if there is anything else I might need to order from the same site that I cant find on Mouser or similar. Send me an email to pierre(a)zebrastudios.se and we can take it from there :)

Well seems like a legit store to me, feels more safe then ordering from China/Hong Kong. Send me an email at the same mail as above if u would like to order some too.

Also curious about your 1176 stereo version build. Is it based on the 1178 or a custom design of your own based on one of the 1176 REVs?

Well it looks like the picture on their website is the same as the one on the ebay listing so I'm guessing they selling the same thing, in which case it would be cheaper to get them straight from china. This is a long obsolete part so most of them around will be fakes I think so I might just go with some well matched fets.

I'm basically just sticking two rev d 1176s in a case for my stereo version. I made my own boards but their essentially the same as the original.

Zebra_PD

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #25 on: May 07, 2018, 08:00:39 AM »
Well it looks like the picture on their website is the same as the one on the ebay listing so I'm guessing they selling the same thing, in which case it would be cheaper to get them straight from china. This is a long obsolete part so most of them around will be fakes I think so I might just go with some well matched fets.

I'm basically just sticking two rev d 1176s in a case for my stereo version. I made my own boards but their essentially the same as the original.

Well that is an valid point but I´ll think I will send him an email and ask if they are original national semiconducters or chinese made copies...

But I have perhaps tracked down som NOS stereo JFETs in the state. If so I let you guys know if will be able to get a hold of more then the two I need. Will prob be a little higher cost but hopefully overly expensive.

Cool! Are building it using original transformers or modern replacements? Have you design your own stereo link?
Kind regards,
//Pierre
___________________________________________________
Semiprofessionell producer but newbie DIYer.
----------------------------------------------------------
www.zebrastudios.se

Zebra_PD

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #26 on: May 07, 2018, 08:10:30 AM »
An update on my progress.

Im perhaps half way in designing the custom PCB for this build. I have put the different layers of the board of Gustavs old design in different layers in Illustrator. Next step will be to incorporate the original UREI output transformers and power transformers and perhaps some other of the 353 components in the design.

Also replace the holder parts for the rotary pots to use switch buttons instead.

Then scale the hole design up from A4 to A3 to get a more vintage look of the PCB that takes up more of the inside of the UREI case. Might also modify the design to be only one copper layer instead of two for a more "original" look.

Will post some sketches soon.

Still undecided if I should incorporate the Jim Williams mod in the design or not though. 
Kind regards,
//Pierre
___________________________________________________
Semiprofessionell producer but newbie DIYer.
----------------------------------------------------------
www.zebrastudios.se

pvision

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #27 on: May 07, 2018, 05:03:51 PM »
What mod does Jim Williams recommend for the 1178?

Nick Froome

Zebra_PD

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #28 on: May 08, 2018, 05:32:56 AM »
What mod does Jim Williams recommend for the 1178?

Nick Froome

replace:
IC 1   National LM6172 / LM4562
bypass pin 1/2   22 pf
C3   22 pf
C6   Panasonic FM 47 uf 25 v
bypass C6   Wima MKP-2 .1 uf 250 v
C7   Panasonic FM 47 uf
bypass C7   wima .1 uf
C9   Panasonic FM 220 uf
bypass C9   wima .1 uf
bypass R6   47 pf
C10   Panasonic FM 470 uf 25v
bypass C10   wima .1 uf
C21   Panasonic FM 100 uf/50v
bypass C21   wima .1 uf
C22   Panasonic FM 220 uf
bypass C22   wima .1 uf
C23   10 pf
IC 2   Linear Tech LT1358 or a National LM4562
C25 and C27   2 Panasonic FC/FM 470 uf 25 VOLT
C60 and C61   2 Panasonic FC/FM 3300 or 4700 uf 25 VOLT
C62 and C63   Panasonic FM 1000 uf 25 v

Kind regards,
//Pierre
___________________________________________________
Semiprofessionell producer but newbie DIYer.
----------------------------------------------------------
www.zebrastudios.se

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #29 on: May 12, 2018, 08:33:52 PM »
Well that is an valid point but I´ll think I will send him an email and ask if they are original national semiconducters or chinese made copies...

But I have perhaps tracked down som NOS stereo JFETs in the state. If so I let you guys know if will be able to get a hold of more then the two I need. Will prob be a little higher cost but hopefully overly expensive.

Cool! Are building it using original transformers or modern replacements? Have you design your own stereo link?

There is a company called Interfet who have remade a bunch of obsolete dual JFETs which are available at mouser so I may get mine from them. Looking at datasheets the INF411 should be a good sub for a dual 2n5457, don't know if it will work as a sub for NPD5566 though should be pretty similar. They actually make a NPD5566 too but it has a long lead time.
On my unit I'm using Luhndal 1540 for input and the Ed Anderson copy of the original output, basically the same as the Hairball version. I was using BF547 for the fets but they were messing with the gain reduction so I thought I'd just go all out and get some matched units.


Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #30 on: May 13, 2018, 02:08:23 AM »
I have a few 5566 I could sell, but Id have to check what they are going for now first.

[email protected]

Gustav

pvision

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #31 on: May 13, 2018, 07:34:15 PM »
At first glance the Jim Williams mods look like the kind of thing you'd be  tempted to do anyway - increase the size of the audio coupling caps and bypass them

Nick Froome

Zebra_PD

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #32 on: May 16, 2018, 03:44:12 AM »
I have a few 5566 I could sell, but Id have to check what they are going for now first.

[email protected]

Gustav

Perfect. I'll send u an email Gustav! :)
Kind regards,
//Pierre
___________________________________________________
Semiprofessionell producer but newbie DIYer.
----------------------------------------------------------
www.zebrastudios.se

Zebra_PD

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #33 on: May 16, 2018, 03:46:55 AM »
At first glance the Jim Williams mods look like the kind of thing you'd be  tempted to do anyway - increase the size of the audio coupling caps and bypass them

Nick Froome

Ah ok, sorry for the newbie question but the reason for that is what exactly? To get less noice and/or to alter the sound of the compressor? :)
Kind regards,
//Pierre
___________________________________________________
Semiprofessionell producer but newbie DIYer.
----------------------------------------------------------
www.zebrastudios.se

scott2000

Re: Building a 1178 lookalike/dual 1176 replica out of a UREI 535 EQ
« Reply #34 on: May 16, 2018, 06:41:24 PM »
Ah ok, sorry for the newbie question but the reason for that is what exactly? To get less noice and/or to alter the sound of the compressor? :)

If nothing else, because he said so...... ;D

Here's what I found regarding JW mods to the 1178
"Give me a 25-stack of 9V batts, I'll monitor my truck's spark or fuel injection on the magic eye." PRR


 

Related Topics

  Subject / Started by Replies Last post
11 Replies
2758 Views
Last post February 17, 2005, 01:18:32 PM
by Coldsnow
9 Replies
2642 Views
Last post October 20, 2005, 10:58:27 AM
by nrgrecording
20 Replies
13092 Views
Last post August 08, 2009, 03:55:17 PM
by SNG
12 Replies
6273 Views
Last post August 05, 2009, 12:44:00 PM
by PRR