I pasted the info here in this first post, so you don't have to search for it

Here's what will be included in this authentic re-creation of a UA 176 chassis kit:

- main chassis, bent, welded, smoothed and powder coated grey

- first front panel  - also folded edges, welded smoothed and powder coated grey

- custom made hinge manufactured following original specs, powder coated and welded to the first front panel

- second front panel to go on top of the first one: this will be the black panel with white silk-screening

- custom made stainless steel thumb screws designed for original looks

- mounting bracket for input/output jacks on the front

- mounting bracket for optional metering switch inside

- handmade, authentic re-creations of the 2 original pcbs: these will be handmade to original specs with fork turrets just like the original
- handmade PSU turret board

- handmade RATIO turret board

- handmade METERING turret board

- first BOM

- first wiring layout for the entire unit

All of this I will offer as a kit in this LIMITED run for EUR 399.00 + shipping & PP

Actually this is the price if we can reach 50 chassis, but I convinced all suppliers - if we don't hit that margin, but only 40 chassis instead, we'll still get that price :)

And I'm positive that we can reach 40pcs.
And in case we end up with only 38pcs, I will have to buy one for Mom and one for Granny - I'm sure they'd love them  ;D

I'll get in touch with all of those who posted here and want to have one or two or...

In case you're new to this thread and interested send me an email to [email protected]
If you posted here and don't get an email within the next couple of days, do the same :)

As in the past - I'll collect the funds for the group buy - and after I received your payment you'll be added to the list here.

Lead time for having these gems manufactured will be around 6-8 weeks.

AGAIN: I'll keep this group buy open until March 15th - after that deadline I'll process the orders and have the kits manufactured...

Currently it looks like as if most people want to use API 361 meters (which is the one I used for my prototype) - and forum member moltenwok posted that a friend of his has more than 30 of these available. But they also turn up on eBay fairly often and are actually cheaper than a new SIFAM meter.
But I optionally I can also do a version designed for the SIFAM R32AF meter which is still readily available...

For further discussion and details go to page 8 (and onwards)


kosi   2 [paid]
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+++++++++++++++ original post ++++++++++++++++

Hey guys,

those of you who are familiar with my chassis work know, I always work with great love for detail when approaching a project.

For those who don't know my chassis: https://groupdiy.com/index.php?topic=63423.0

Here in Germany we have a saying that says "Ganz oder gar nicht" which is pretty much the same as "Go big or go home!"
(Maybe that's the basic core of what people commonly call "German engineering"  hehe ;D)

Anyway, I actually wanted to start a UA 176 vari-mu project more than 5 years ago, but as I always found it more challenging to  find out about how original pieces of gear work, how they were built and faithfully recreating them rather than buying a pcb (if available)  and a generic enclosure to make some kind of a clone, the UA 176 was not easiest project to tackle.

But after gathering quite some experience with other chassis projects over the past years, and people keeping on bugging me to do the 175b or 176 I thought ok let's do it - properly! :)

That means faithfully recreating the original chassis work, the original pcbs, the original turret boards etc.

First step: designing & manufacturing the prototype chassis

I'll post more pics and updates in the next couple of days and then some more as the project evolves :)

If you want to share your thoughts, you're welcome to do so and if you just want to know how it all turns out,  subscribe to this thread.

If all goes well I plan to do a small run of UA176 kits that include the chassis, pcbs, turret boards and a build manual for recreating on of these gems for yourself ;)
« Last Edit: August 06, 2018, 04:17:47 PM by rainton »


Both -  the 175b and the 176 are based on pcbs as well as some P2P. Since I don't own an original one I have to get all information from pics I found on the web - here's one that shows the inside of a 175b:

One of the challenges is, that the pcbs and the footprint of the components on it have to match the cutouts on the back of the chassis 100%. And since the back panel is pretty much jam packed there's not much room for mistakes ;) :

It's funny how some tube-sockets are mounted straight to the back panel while others are soldered to the pcbs and just stick out the back of the unit through circular cutouts - one of them with a cutout large enough to accommodate a tube shield and another one with a cutout just large enough for the tube itself  ???

hell yeah - finally!!!! congratulations mate. love your work and dedication! i have all my xformers and meters ready. cant wait :) put me down for a pair please.

oh... and while its not original, id vote for a top enclosure. just to make sure no one fries himself...
« Last Edit: June 12, 2017, 08:09:26 PM by salomonander »


yes finally ;)

Well the prototype will be as close to the original as possible - also meaning there'll be no lid on this first one.
But if a small run happens I would leave things like that up for discussion.
If the majority wants a lid, then there shall be lid  ;D

There's many more details to discuss later - such as choice of transformers, VU meter etc.

For this first one I'll go with vintage UTC 0-1 on input, UTC-A19 as interstage and - since the original output transformer is unobtainable - Sowter 1285e as output transformer.

Another topic is the attenuators. The vintage units used some Daven (or sometimes Langevin) 600 Ohm T-pad stepped attenuators with 2db steps. They are usually very expensive, but I was lucky to find some for pretty cheap. I was really surprised how huge they are!!  :o

From left to right: Alpha stereo pot, vintage Allen & Bradley, NOS Mallory 600 Ohm T-Pad, vintage Daven 600/600 stepped attenuator

The Davens have a great feel to them - they feel more like a very smooth pot with very fine detents than a switch :)
« Last Edit: June 13, 2017, 05:02:48 PM by rainton »


Ok let's get serious  8)

Here's the basic prototype chassis - all powder coated with the closest match I could find to the original color:

Even though it has no lid it is the most complex chassis I've done so far - also due to the top edges of the back chassis as well as the the top and side edges of the front panel are folded inside, the seams in the corners are welded and then smoothed before powder coating - you can see it very well on this pic:

The hinge is welded to the front panel and then powder coated as well:

In these pics you can see even better what I meant by the folded edges. The front panel is actually not just a flat panel - also, you can see that very well on the first pic, the bottom of the front panel has a cutout to exactly fit the hinge  :)

Both the 176 as well as the 175b actually feature 2 front panels - the first one is made of solid steel all powder coated with the hinge welded to it, and the second is sitting on top of the first one - a very thin black panel with white silk screening...you'll see that very soon ;)


Since I couldn't find the original panel screws anymore, but still wanted the original looks, I custom designed a screw, visually modeled after the vintage ones and had them manufactured  ;D


One detail  where I deviated from the original:

to fasten the front panel to the rest of the chassis the original units had only some kind of bracket mounted inside the chassis with a clip nut put over it. ???

Not a very sleek solution - especially since there's no well-defined stop-piece for the front panel when closing it:

As you can see in the pic, the front panel is closing against the inner-edge of the rack ear which can make it difficult to feed the screw into the nut (which would explain the screw sitting in there kind of crooked on some pics I found on the web)

Anyway, I came up with the following solution:

instead of mounting a bracket inside the chassis with a clip nut on top of it, I designed the bracket as a part of the chassis with a nut punched into it. The depth of the nut also makes it serve as a standoff as well as a stop-piece for the front-panel to close against.

Works great!  ;D


Also visible in the pics of the original unit is the bracket that holds the 1/4" jacks on the left side.
Obviously these connectors allowed for patching the comp into any other piece of gear directly, while the unit also has a barrier strip type terminal on the back for wiring it up a patchbay...

The jacks are mono switching 1/4" inch - so as soon as something plugged in there, the input and/or output on the back is disconnected.
Feeding a piece of gear with a balanced signal through 2 mono jacks seems kind of weird though ;D

BTW: If any of you have access to a real 175b or 176 it would be great to hear your thoughts :)

Here's how this bracket looks in my prototype unloaded:

and loaded with 4x 1/4" jacks:



Now the original has a piece of Bakelite mounted in front, I guess that was maybe to support the front panel when closing the unit (?)
I'll probably add it later on, but since the above mentioned stop pieces work very well, it's actually not essential here ;)


I'm proud to announce that with the incredible help of pcb design artist and fellow forum member LIVINGNOTE and my newly aquired turret staking skills, it was possible to recreate the original pcbs of the 176 / 175b to an extend where they're pretty much indistinguishable from the original ones.

Now, after we did a lot of tweaking and comparing, Livingnote finally made the prototypes and I think it's truly a work of art!

Here's some pics of the almost finished pcbs (still some fork turrets missing):

and here are the final pcb prototypes with all turrets in place and the prototypes of all 3 additional custom turret-boards (PSU, ratio & metering):

Up next is stuffing the pcbs & turret boards - and of course mounting all components to the chassis  :)

amazing work mate!

it was possible to recreate the original pcbs of the 176 / 175b to an extend where they're pretty much indistinguishable from the original ones.
did you fix the traces so that C1 and C2 do not have to criss-cross each other?


Thanks salomonander :)

Yes it's quite a trip - but we're getting there!

did you fix the traces so that C1 and C2 do not have to criss-cross each other?

Nope - we didn't "fix" that.
If we had done so, we'd have needed to retrace the entire board, and we decided to stay original.
Not a big deal I think - both caps placed next to each other and on one end their (shrink-tubed) wires cross. :)

BTW the first board is stuffed and ready to go into the chassis, but I have to wire up that part of the chassis' back panel first, otherwise the access to the relevant terminals of the transformers will be blocked by the pcb...

I'm now stuffing the 2nd pcb and mounting all components to the back and front of the chassis - stay tuned...

Oh and you're more than welcome to leave a comment or share some thoughts - I just realized this thread has more than 600 views already, but only 2 people involved so far ;)


Oh and you're more than welcome to leave a comment or share some thoughts - I just realized this thread has more than 600 views already, but only 2 people involved so far ;)

haha! How about, looks f'n amazing and great work so far, to you and Livingnote :-)  You've certainly not "gone home" anytime recently (Cause you have spent so much time "Going Big"  ;D)

my la2a scratch build: https://groupdiy.com/index.php?topic=65716.0
my orig tube DI w/ EQ build: https://groupdiy.com/index.php?topic=73834.0
2020 fav artist: Kate Bush


Looking amazing mate-2 quick questions-presumably you've allowed for the sowter output transformer for the 176 and do you have a ballpark figure in mind do I can start saving caus I'd hate to miss this!

im not rainton, but yes its made for the sowter output. the original is unobtainable. i was in contact with magnetica and cinemag. cinemag took over reichenbach - who made the original. but sadly the blueprints were lost. david looked all over but no chance. so sowter it is. they are good xformers...


Any idea who built the transformer for the retro 176?

Any idea who built the transformer for the retro 176?

i dont. i thought they were made by cinemag - but david said its not the case.... so i have no clue. cheers


Thanks guys!

great to finally see some movement here :)

Looking amazing mate-2 quick questions-presumably you've allowed for the sowter output transformer for the 176 and do you have a ballpark figure in mind do I can start saving caus I'd hate to miss this!

I'm sorry but at this moment there are still so many things to consider and I'm also still waiting on quotes by suppliers for turret boards etc. that I can't put out any numbers at this time. As soon as I figured it out, I'll let you all know :)

regarding the output transformer & the retro 176.
As far as I've heard from a fellow forum member who owns a retro 176 - that thing sounds absolutely great but in his opinion not vintage at all. Rather clean sounding compared to the original 175b/176.
Unit7 - if you read this it would be great to have you chime in  ;)

Apart from that I can say the OT substitute from Sowter is massive! Bigger than the original - all mumetal covered.
But in terms of specs Sowter said they are very close to the original ones, but with better shielding.
Even the color codes of the wires are pretty much the same as specified in the 176 schematics.

Today I finished the 2nd pcb as well as mounting all components to the chassis. Here's the 2nd pcb - it's not as crowded as the first one, but it has a can cap soldered straight to it:

I'm not quite sure how to solve this in the kit version later. The actual can cap used in this spot was a Mallory PFP:

They're pretty much unobtainable nowadays - especially the value needed here. The FP ones with 2x10uf 450V are not unobtainable, but also very hard to get - and I wouldn't recommend using vintage can caps.
In the prototype I used a FP style cap, so the circuit board was prepared with slots to fit the wider terminals .
But frankly it was kind of a drag to mount, and solder it, and we'll have to figure out a way how to do it later in the kits.
I'm thinking about at least adding the footprint of 2 regular modern electrolytics so you guys can choose (?)

Anyway, here's a pic of all components (except for pcbs & tubes) mounted to the back of the chassis:

and another one:

I  already started to wire up the PSU section and the other transformers, so the pcbs can finally go into the chassis very soon...
« Last Edit: June 23, 2017, 07:27:13 PM by rainton »


Just finished the PSU section  :)

The pics I found show a small difference here between the UA175b and the UA176.
That's mostly due to R39 being located on the PSU turret board of the 175b, but in the 176 it's located on the ratio turret board mounted to the rotary switch on the front panel, where it's one of the 4 different resistors for different ratio settings (while the 175b is limited to 12:1 ratio only).
I followed the 176 component layout, since that's what I'm building:


...beautiful work...
..note to self: don't let Harman run your company..


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