Hello,
This week is about the
Mixer. I call it a .27 since its functionality and complexity is to be found inbetween a REDD.17 and the REDD.37/51.
I started out with collecting inforomation and pictures on the internet. That was about 2 years ago. I came to understand that the REDD.17 was from Germany and the REDD.37 was already a Britisch desk.
Not that I needed any, but the fact that the EMI-engineer (Peter Burkowitz) who designed the REDD.17 had been doing that in my very hometown (Köln, Germany) was a quite a morale booster. I hopped on my bike and found that the studio part of the complex still existed and was also being used as such. Great. There were even some traces of former EMI activity:
I found out there was an extensive
2011 interview with
Burkowitz about his carreer, called
'Lebensbilanz: 80 Jahre Klangaufzeichnung', © 2012 by Polzer Media Group GmbH (interviews by F. Engel, G. Kuper, F. Bell und J. Polzer), ISBN: 978-3-934535-30-5. For sale as pdf. Language: German.
On page 88, the chapter about EMI/Electrola Köln starts. He explains that, in 1953, in order to have modern equipment, a studio or record company had to build it themselves. Since a lot of recording of classic music was done on location, he deviced a portable 3-unit set, that
'could be carried by a few strong young men and put together to form a desk.' He mentions receiving a Gebrauchsmuster for it, which indeed and to my surprise, can be found online:
Hm, not quite a REDD.17, I hear you think. 'The folks from London' asked him if he could redo his trick utilising the new-and-very-small V72-series amps. He did, and the result was the REDD.17, all of them built by ENB Schimon in Berlin. ENB Schimon was the only company in Germany who ever used Siemens Elevator push buttons for the talk-back circuits. Another example of that habit can be found at Funkstunde.com:
It is funny to see those push-buttons reappear on the TG12345 desks
On page 98, Burkowitz can be seen behind his own creation at Toerag, in 2008:
Page 100 held a surprise for me: the REDD.37 was also thought through, planned and engineered here in Köln, by Burkowitz.
Wow!
Some more searching 'redd.37 manual' on the internet suddenly revealed an actual manual. 2.8 kg of drawing. For Sale! Not cheap, but I didn't hesitate for a second. This changed my project quite a bit. Before this purchase I was trying to establish a very
GOOD-LOOKING 3-unit REDD-inspired desk (with Tuchels, Paintons, etc), with some self-designed electronics of no importance
under the bonnet. Suddenly, I had it all. All electrical info required to build it 1 on 1. No dimensional info, that must be said, but soon someone would save me.
Upon studying the plans, I noticed that the two bottom units were very 'under-used': double-width VU-drivers, some spare amps, lots of room for never-materialised extensions, etc. I also noticed that all those typical German parts, although to be found right here in Germany, were
not cheap at all: a Tuchel 3-pole chassis socket: 5 euro, a Tuchel 30-pole plug: 6 euro, a Tuchel 12-pole plug: 5 euro, rotary switches: 7 to 20 euro, Siemens 'U-Link' sockets: 6 euro each, cable plugs for them: 17 euro, etc, etc, not to mention V72 amps, signal transfomers, Painton faders or tone control coils.
If I were to pull this off, I would have to reduce. Without losing the character and ending up right in the middle of a .37 (which I find too crowded) and a .17 (which sports a refreshingly empty surface).
Here's what I reduced. I ditched the pre-fader/post-fader knobs, I ditched the 4B and 5B Mic inputs and the associated controls, ditched the entire circuit to derive a Mono mix (knobs on the front of the Centre Section), I combined some non-audio V-7x stuff like VU-meters in single-width dual channel units (16-pole Tuchels instead of 12-pole), I simplified the Echo channels a bit, and I went..
from 48 V-7x amp SLOTS to 28,
from approx. 30 V-72 Amps to 24,
from 5 basic units to 3,
from 14 Paintons to 12,
from 82 Tuchel sockets to 33,
from 142 Rotary controls to 72,
from 144 'U-Links' to 68.
The following shows a bit of my resulting design. I also reduced the overall width a bit since the .37 just feld too wide.
All well, but I was still looking at the build-time and -cost of all those self-built V72-clones,
BEFORE any sensible testing could take place. Not good. My solution is to go 'temporarily OpAmperized': I will start all V72 Amps as fixed gain Opamp units, and upgrade one or two every birthday
:
And then, roughly last spring,
I remembered I had a
record cutter to drive, so I acquinted myself with
mastering controls. I discovered that EMI had done the same. Elliptic EQ, monofy the Bass content not to let needle jump. That stuff. The drawings show that on the 'studio 1' REDD.37, the famous Shuffler circuit was
REPLACED by a Vertical Bass Cut circuit on 14th of March 1962 (the addition to the part list was made by
Len Page himself). Both being knobless circuits, such a change can go largely unnoticed, but in the photo below you can see that someone used
black nail polish and
Dymoed '
VBC'. Probably Len Page again:
So there I was, august 2021, looking at a 3-item part list for a 200 ohm VBC, but without schematic. At this point in time, I started to
teach myself how to calculate bridged T-pad attenuators. Some of the available .37-control info served as 'correct answer' for my efforts. With this skill, I could do a VBC. Not that mine uses the parts Len Page typed, but hey, on paper, it works. And I could give it controls: 1) how much of it (in 2 or 3 dB steps) and with what slope, 6dB or 12 dB. I also threw an extra 'Spreader' at the Mastering section, coming to a desk-total of 75 rotary controls. Since I absolutly loved that single ridiculosly big rotary knob smack in the middle of the .17 desk, but couldn't have it on a 4-output mixer, I decided to make the new Spreader my '
big rotary control in the middle'.
More to follow for sure.
kindest regards,
Mart
