C414, C451/C452 spare parts transformers.

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Bo Hansen

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Muffy, and you others who have thought about the size of C414 transformers.

The transformer Ü35 used in C414E1, EB, C451E, EB and C452 with a ratio slightly less than 1,4:1 and Ü54 which is only found in C414EB-P48 with a ratio of 6:1, have a smaller size of U-lamination and also a smoother bobbin than T14 style that many mention in this context.

Ü35 and Ü54 have a lamination/core package that is only 5 mm. thick and a bobbin that is 10 mm. thick "around the belly" and 15 mm. wide, and these are the absolute maximum dimensions to fit in these microphones.
The length of the laminate/core is 25 mm. and width is 10 mm. but these measurements can be a few millimeters larger without problems.

Since I will not build or clone these microphones, I only repair and renovate these, maybe 20 or so a year in a mixture of the ones I mention above, I have to find or have someone make replacement transformers that both fit physically and also in output level and sound character.

Some of you have probably been inside one of the older C414s and seen how enormously crowded it is, especially at the bottom where the transformer is mounted.
It has even made a cut-out in the bottom of the frame to make room for the transformer bobbin.
The outer casing is the narrowest at the bottom where the transformer is mounted on the inside, it is even so that the original bobbin rubs against the inside of the outer casing, so a transformer/bobbin that is a few millimeters larger will not fit.

Regarding Peluso's version of C414, they have a completely different housing with more space on the inside where a much larger transformer can fit, for example T14 or similar.
They can also of course choose a transformer with a higher ratio, for example 12:1, if they have copied C414EB-P48, but it will result in much lower output level compared to the original..
If it is C414E1 or EB they have copied and has a transformer with a ratio of 12:1 instead of 1,4:1, yes, as you can calculate yourself, of course it will be extremely low output compared to the original.
(maybe they mean 2:1, not 12:1)

So I guess there's some misunderstanding, otherwise I would be very surprised.

--Bo
 
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muffy1975

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thanks Bo, thanks for the information.

6:1 it is for the p48. It is the p48 that I'm building 'into' the case of my non working C414 bXLS.

If i can fit a BV8 style tx in there I'm good to go right? if it's 6:1 with a centre tap on the output side of the TX?
 

Bo Hansen

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thanks Bo, thanks for the information.

6:1 it is for the p48. It is the p48 that I'm building 'into' the case of my non working C414 bXLS.

If i can fit a BV8 style tx in there I'm good to go right? if it's 6:1 with a centre tap on the output side of the TX?
Muffy,

Sure, any other 6:1 microphone output transformer (or microphone input transformer used backwards) with CT center tap on the "200 ohms" side is ok to use, and works in the P48 circuit.
(if the size fits in your case)
The transformer should have a step-down around -16 dB terminated
with 2 kohms.

--Bo
 
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Moby

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U54 TX : -

I asked Peluso which TX they use in their own 414 and he told be they use the T14. Can that be right? the T14 is 12:1.

I am trying to find a U54 TX. Bo mentions above that the U54 should be 6:1. Does that mean, if space was no issue, the Bv8 style TX would work in this circuit? I believe this is 6:1.
Bv.08 is 6,5:1 , thats fine, but transformer is way, way bigger than T14/1 ot U54. If it fits your build, fine, but it can't be used in the vintage mic.
 

Bo Hansen

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MicScharf,

Sure, there are a few microphone output transformers that are newly manufactured today that could replace AKG Ü35 and Ü54 with approximately similar impedance and ratio, but unfortunately they do not physically fit the size in these C414EB, C414EB-P48, C451EB/452 that I talked about earlier here.

In addition, these transformers must also have a CT tap on the secondary for the Phantom powering.

I have been working on this project all this summer together with some colleagues and transformer manufacturers, so with a little luck we will come up with exact suitable replacement types for Ü35 and Ü54.

--Bo
 
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doqmemory

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Not needing a transformer for a C414eb but needing a pattern selector switch as one of mine is missing both the bearing that allows the switch to "stop" at each pattern but also the tip of the switch has broken off requiring a pen to change the position. Any source for replacements?
I ordered my replacement last year directly from Harman, p/n 2148Z00180 (about $21).
 

audiophreak

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frans

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You could ask someone at Austrian Audio, they are mostly former AKG people and should be in the know about details.
Then Michael Amon (freelance mic tech) Reparatur | Mikrofonservice.at | Österreich comes to mind.
The german specialists of Haufe Transformers work wonders. HAUFE GmbH & Co. KG
The award for the smallest mic transformers goes to Beyerdynamic - for the headset ribbon mic you may have seen in the movie "Alien", it's as big as a pill.
If you need help contacting anyone in Germany, helping with the language i'll be happy to help, Bo. I really like the Bo D.I. and have a few of them :) I was in Gothenburg a few weeks ago - i should have come round and bought you a drink.
 

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