Simple xformer question
« on: August 16, 2018, 09:41:01 AM »
Hi, I’ve lurked around here awhile but never asked anything. Usually I can find my own answers thanks to everyone’s prior posts. However... I’ve not worked with plug in type input and output transformers before and would prefer to not destroy these.

I was gifted a Berlant Concertone single channel tape preamp and since it’s useless alone was planning to use it as a mic pre as is common. I have an Altec 15095a and a Dukane 3A55, both typically input xformers as I understand. I also have a Freed output xformer as pictured with Berlant schematic below.

I have spent a great deal of time trying to understand exactly what should be connected to what and every time I am sure I get it, I read something else that confuses me.

My question: can I use the Dukane as input and Altec as output, and if so, how would I connect the Altec? If not, should I use the Freed pictured below?

Thank you so much for enlightening me.
Ryan


Re: Simple xformer question
« Reply #1 on: August 16, 2018, 09:42:05 AM »
Here also is the Altec diagram

Re: Simple xformer question
« Reply #2 on: August 16, 2018, 09:44:29 AM »
AAAAAND the Dukane diagram

Re: Simple xformer question
« Reply #3 on: August 16, 2018, 07:33:02 PM »
My question: can I use the Dukane as input and Altec as output, and if so, how would I connect the Altec?
Dukane 3A55:  suitable input transformer.
Altec 15095:  suitable output transformer fed from cathode follower (V104).
strap it 15k : 600.
you probably should replace the 11 pin sockets with octals  and there are  tie points to deal with.
Freed:  appears to have a gapped primary,  looks like voice grade.

L´Andratté

Re: Simple xformer question
« Reply #4 on: August 17, 2018, 03:51:30 AM »
Freed:  appears to have a gapped primary,  looks like voice grade.

Meaning limited bandwith?
"Why not get an assistant to work the faders? Real vintage! And maybe cheaper... ;)"

abbey road d enfer

Re: Simple xformer question
« Reply #5 on: August 17, 2018, 06:20:00 AM »
Meaning limited bandwith?
Yes, telephone range, no highs, no lows.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

5v333

Re: Simple xformer question
« Reply #6 on: August 17, 2018, 07:04:34 AM »

Re: Simple xformer question
« Reply #7 on: August 17, 2018, 09:50:51 PM »
Ok I found the attached file that made me realize how wrong my output transformer wiring thoughts were.  So, given the attached Berlant output xformer diagram, and the diagram on the Altec 15095a I posted above, I should make the following connections?  Any corrections welcome..
Berlant pin 1=Altec pin2
Berlant 2= Altec 8
Berlant 3= Altec 7
Berlant 4= Altec 1
Berlant 5 = ALtec 3-4 strapped
Berlant 6= Altec 6
Berlant 7= Altec 5

Re: Simple xformer question
« Reply #8 on: August 19, 2018, 01:07:46 PM »
For anyone else that may need the info in the future, the pin changes I noted above work with the exception of the Altec pins 3-4 being connected to anything else. They’re just strapped together with no other connections. Pin 5 can be a tie point for what was previously tied to pin 7.

I’m sure if I’m missing something here someone can correct it.

Belant Concertone
« Reply #9 on: August 19, 2018, 09:21:02 PM »
If you do not want to modify the Belant by installing octal sockets,
a couple of ideas.
1.  output is present at the 1/4" output connector J104 .
fabricate a small box/enclosure, 1/4" connector, octal socket for the 15095, and an XLR.
you can make it fancy by adding polarity and 150/600 output impedance switches.
2.  if you are planing on using the Berlant with hot mics/loud sources,
an input transformer with less step-up is advantageous.
note the 1:5 ratio  eleven pin transformer, apparently from a Berlant.
 they are rare but can be found.


Re: Simple xformer question
« Reply #10 on: August 19, 2018, 11:31:14 PM »
Thanks for the replies gridcurrent, I appreciate it. I have been watching ebay on and off for about a year and haven’t seen any 11 pin input transformers; I had hoped to find the mic and the bridging one you show above.

I finally gave up and have had to figure it out... the output being octal just meant a re-wire, but I do believe I’ll wind up replacing the input with an octal as well given the scarcity of 11 pin transformers, coupled with my desire to make this functional and interesting to record with as cheaply as possible.



 

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