Eckmiller W86 - refurb and makeup amplifier options

[thomasdf]

Hello everyone

I have three Eckmiller W86 EQs that I plan to put to use in a near future. I have found the schematics, shared here : https://groupdiy.com/threads/eckmiller.48860/post-617349
but unfortunately there are no values. In the middle of the unit is a large double 8uF / 350V electrolytics that has been removed from one unit, and bypassed in the other two. I each units they've been replaced / bypassed with two 6.8uF tantalum caps? I wonder why and wish to revert it to the original design.

I need a 34dB makeup amp after them (or before, from what I read it can bring a nice color). The thing is they are passive, balanced and need to be fed and drive symetrical signals. I am wondering what path I could follow.
Back then it was designed to be used with a V72 but that's out of my budget and I would like the amp to fit in a 1U rack unit.
I have 2520 makeup boards that would need both an input and output transformer
I thought of giving the Neve BA283 a try, too.

What about a symetrical line amp ? Germanium maybe ?

Any experience with such duties ? I think I want to go towards a full range, colorful solution so I think I should avoid bal / unbal with ICs. but maybe there is a clever line amp or design I do not know about.

Feel free to chime in

Thanks

Thomas

 

[Michael Tibes]

Some time ago I bought a bunch of late 'opampized' V72 replacement cards of german ebay in order to use them as makeup amps for these eqs - but haven't found the time to try them yet. There are quite some versions around, the 'latest' ones with opamps might go for relatively cheap if you get lucky. V272 / 372 will be more expensive. Other than that any micamp should do, the THAT chips might be a good option?

I wonder if these eqs need a certain load to function as intended?

 

[Michael Tibes]

In the middle of the unit is a large double 8uF / 350V electrolytic

Are you sure it's an electrolytic? That would be weird because of the tolerances... I'd have to open one of mine to check.

 

[beatnik]

UTM has the whole iron set for the V72 for less than 150€ which is very well priced.

Maybe a Pultec EQP-1A makeup stage ? The Sowter opt without mu metal can fits inside a 1U chassis

For solid state you could search Neumann cards like PV46, V472 and similar, they tend to go for about 200-300 euro for a dual channel card with input and output transformers

 

[thomasdf]

Thanks all for your ideas. The central cap looks like polarized dual electrolytic to me... but I may be mistaking. Two leads coming out of them, and the body of the cap is grounded. I can tear one of them appart for confirmation if needed.

Re. the load, I'd have to do some testing and see, but they hate unbal signal for sure, sounds like crap... so a Pultec makeup may be appropriate with the proper iron.

I always thought the V72 was a complicated design, but maybe I'm wrong... I'd have to make 2 channels of it fit inside a 1RU case... that may be a bit tricky, especially in terms of cooling, power supply etc.
I can't find any decent priced transistorized v72 yet, but I have an old TAB summing amp module that I am sure can be turned into a 34dB stereo makeup amp.. but I never got it to work. Nice Haufe / Pikatron iron, though.

I'll sleep on it Thanks !

 

[thomasdf]

I have decided to use Neve BA283 makeup amps, as it is a flavor I am not very familiar with. PCBs are on their way. I’ll use a pair of 1:1 Cinemag transformers from my stash, and the output transformer has yet to be determined (Carnhill / UTM)

Among the three units I have, two have close serial numbers yet the construction is a bit different. Components are not in the same spot. But same denomination and value.
The third one is more recent and you can see the varnish on the components has aged (yellowed) differently.

I will also replace the dual 8uF capacitors, they have been bypassed with 6.8uF tants. I wonder why as the circuit is still a bit mysterious to me.

Here are gut shots

 

[thomasdf]

Here’s a close up of one of the orig 8+8uF 350V hydra werk capacitor

They are C13 and C14 in the circuit

 

[rock soderstrom]

In the middle of the unit is a large double 8uF / 350V electrolytics that has been removed from one unit, and bypassed in the other two. I each units they've been replaced / bypassed with two 6.8uF tantalum caps? I wonder why and wish to revert it to the original design.

I guess the old hydra elyt caps gone RIP and somebody wanted to change the lower center frequency to a more (musical) useable range??

Here is a link to a nice original "Prospekt" of the Eckmiller W86.

Here an recent Hydra capacitors advertising movie clip with well known actors.



Edit: The first person to fill in the schematic with the actual component values is sure to get an incredible number of karma points and a guest appearance in the next Avangers movie...

 

[thomasdf]

Thanks ! That prospekt is amazing. Nothing less. I mean : how beautiful is the drawing, presentation, font...?? Work of art. And the console, brrr, it's 100% dream material.

I can start by stating that I know the value for C13 and C14 Your schematics have the parts number, that's already a big step ! I'll try to fill them

Cheers

 

[rock soderstrom]

Thanks ! That prospekt is amazing. Nothing less. I mean : how beautiful is the drawing, presentation, font...?? Work of art. And the console, brrr, it's 100% dream material.

Did you see the rest of their vintage prospekts and info material? Wow, wow and wow! I will do a dedicated thread for it in The Lab. Amazing find.

https://www.echoschall.de/en/library/about-the-library/general.html

I can start by stating that I know the value for C13 and C14 Your schematics have the parts number, that's already a big step ! I'll try to fill them

That would be really great!

 

[thomasdf]

So much gearporn haha !!

Re the components, here is what I have so far. This is a simple visual inspection, to go further I need to take one of them appart and / or do some measuring
This is the component's name and the value :

1 : 500R
4 : 0,015uF
5 : 0,01uF
7 : 4000pF
13 : 8uF Electrolytic 350V
14 : 8uF Electrolytic 350V
15 : 42R
17 : 42R
18 : 500R
22 : 0,015uF 500V
23 : 0,001uF 250V
24 : 5000pF
25 : 3000pF

The circuit is completely balanced and drawn in symmetry so I suppose all components have their mirror on the other side, which should help figuring out some values.

I'll update as I discover more things...

The W86A is inductor based and supposed to sound absolutely amazing. This one, the W86 is RC, and quite simple except the switching system. The build quality is out of this world and the caps look like Hydra / Siemens / high quality paperfilm but I think it could be built from the ground up with great results. I see no fairy dust or esoteric components here...

 

[C.B. - Boudio]

I'm thinking... could it work if only the half was made? It looks really interesting to me, to build myself - simple and no too exotic components.
And the switching seems just one switch at a time (per side), no? For +3 high, only that corresponding switch etc... After all, one side of the switches is more or less common per segment. If this makes sense in any way...
Switches are drawn flat, right? What are connections 3-4 and 5-6 for?

 

[thomasdf]

If you are referring to the 8 pins connector :
1 input hot
2 input cold
3 unused
4 unused
5 ground
6 unused
7 output hot
8 output cold

From what I understand of the EQ design, one side could work on an unbalanced signal, with the correct impedance.

I still need to figure out the values of the block paper capacitors if you want to clone it !

 

[telewulf]

Gosh, am I lucky to have stumbled onto this thread! Great infos (thank you thomasdf!) and @ Rock: What a wonderful leaflet!!!

When I started work at NDR in Hamburg there was still one small studio equiped with Siemens V72, TAB V76, Maihak W87 and Eckmiller EQs. When it went out of comission I was lucky enough to be able to buy the console and it´s serving me to this very day - longer than it has served German Radio by now and without one day of failiure.
(I could not blame you if you accused me for boasting, so: Sorry in advance!)

 

[telewulf]

May I draw your attention to page 8 of the lovely leaflet? They give specific information about the source and load impedances and they are tremendously importand if you want your Eckmillers to work properly!
Since they are completely passive, they interact heavily with the source by that they are driven and with the load that they themselves drive.

@ thomasdf:
And for that reason it is of the utmost importance, that you use the W86 in an environment where they are driven by a source impedance of ca 20 Ohms or less (a V72 does precisely that) AND where the load is ca 2 kOhms (V72 again) but not more than the stated 4 kOhms. The trouble with buffer amps with an input transformer might be, that it might lean too much towards being an inductive load, which will alter the frequency curves of your W86. You´d be much more on the save side if you used an op-amp-buffer with a high input impedance and strapped 4,7 kOhms across the input.

All these old German modules were built to interact with one another and the passive Eckmiller-EQs even more so!

Let me explain with a drawing from the 1973 edition of the "Handbuch der Tonstudiotechnik". This drawing shows a signal chain where every amp is a V72.
As a mic amp it is the perfect load (2 kOhms) for a KM54 (200 Ohms) and it is the perfect source (20 Ohms) to drive a Maihak W66 (200 Ohms).
The W66 is passive so its input and output impedance is the same (200 Ohms) and up to eight channels can be summed by the second V72. (Not more than eight!)
The summing V72 (20 Ohms) drives the main fader (200 Ohms) which drives the third V72 (2 kOhms).
So when you are dealing with these old modules you must allways consider the impedances.

 

[C.B. - Boudio]

Gosh, am I lucky to have stumbled onto this thread! Great infos (thank you thomasdf!) and @ Rock: What a wonderful leaflet!!!

When I started work at NDR in Hamburg there was still one small studio equiped with Siemens V72, TAB V76, Maihak W87 and Eckmiller EQs. When it went out of comission I was lucky enough to be able to buy the console and it´s serving me to this very day - longer than it has served German Radio by now and without one day of failiure.
(I could not blame you if you accused me for boasting, so: Sorry in advance!)

Looks so amazing!! Aren't you selling anything by chance?

 

[telewulf]

Looks so amazing!! Aren't you selling anything by chance?

I´d rather not ... although ... when I popp my cloggs I want to be sure that the old stuff will be in good hands

But if you would like to spend a weekend in a studio, where precisely these old horses are still used for broadcasting - No problem - Join the "Eifler Radiotage"!
https://www.eifeler-radiotage.de/fotos-oktober-2023

I myself did a night shift in 2022 and it was really worth to lose one nights sleep.

 

[C.B. - Boudio]

But if you would like to spend a weekend in a studio, where precisely these old horses are still used for broadcasting - No problem - Join the "Eifler Radiotage"!
https://www.eifeler-radiotage.de/fotos-oktober-2023

I myself did a night shift in 2022 and it was really worth to lose one nights sleep.

I think I'll try to convince my family... Seems so great! And it's not too far from the Belgian border, too.

 

[telewulf]

Any experience with such duties ?

Oh yes ... learning by burning

I always loved my old Eckmiller (HV55, HV53 and W86a) for their obvious craftmanship and was curious about how TS10 (extreeem high cut) and HS10 (extreeem low cut) might sound. I had seen the frequency plots and wondered: Can it be true that a horizontal line can go straight into a 24 dB/okt drop without any resonances before or after???
So I bought on unit of each because I knew even then that they were built to be used only in conjunction with one another. They as well are completely passive but since they do only cut, they do not require a 34 dB boost. So I racked them and fed them into a Maihak W66. The resonances were so clearly audible, I did not even have to make any measurements. I was so disapointed and sold them emidiately.

Well, today I know, my mistake was: I did not account for the mismatch in the impedances between the HS10 and the W66! ... learning by burning.
And I was even stupid enough to make that mistake even though I had read the Eckmiller related pages in the 1974 edition of Johannes Webers´ "Tonstudio Technik"! So for everybody elses benefit I attach these pages, which show not the precise schematic but rather an principal overview of the Eckmiller circuits. Might be helpful if one wants to understand the principal.

best wishes from Bremen,
Wulf

 

[telewulf]

Looks so amazing!!

Thanx ... I rather think this one is:
https://funkstunde.com/category/technik/