Schlumberger p 17172 transformer and new SB4000 compressor?

[ik01]

Hello guys.
I am building SB4000 compressor (latest generation of GSSL clone...).
Well, recently i bough few really old modules from vintage audio console (Schlumberger) and i also got some spare parts (2 audio transformers from preamp modules..). My plan is to incorporate trannys in SB 4000...

Few years someone posted measurement results here on prodigy pro site, so I will c/p it and post a photo of trannys.

Any information or suggestion would be more then wellcome. I am not so much in electronic part of the story, but feel free to post any data od tip. Friend of mine that helps me with this project is experienced electronic engineer..


Schlumberger p 17172 transformer measures:

primary:  48.59H@1kHz &  113.6h@120Hz  dcr~530ohm      216pF@1kHz  13.78nF@120Hz
secondary:2.897H@1kHz & 8.332H@120Hz  dcr ~40ohm      3.49nF@1kHz      192nF@120Hz
when used 1:4  20Hz - 22Khz (sound card limit, RMAA) -2.5dB@17Hz +1.5db@22kHz
when used 4:1  20Hz - 22Khz (sound card limit, RMAA) ~flat



Thanx in advance

Ivan

 

[sheadstedford]

Hello mate ive just built an sb4000 but i am modifying it to incorporate a tube srpp drive stage in input. im intreaged to know how this transformer intergration would work and the reasoning behind your idea. im making mine for a university project where i have to research various modifications for mix bus compressors so any information you have will be very helpfull as credible references to new ideas in evolving the mixbus compressor!!

 

[ik01]

Hello Sheadstedford.

Well, my electronic knowlwdge is in best case humble . Anyway, transformers on output stage are here to balance signal. Difference is off course in sound wich means different transformers can differently sound on output ( character). Since I did not payed for my trannys, this experiment will cost me 0$, and I will put a simple switch on back side to have transformer or transformerless output stage. I really dont have idea should i expect softer or punchier character, but what I do know, those difference can be from subtile to very audible (depends on transformer, device etc...)..
So whatever result will be, i can switch it off and on...

Transformers that I posted before are very old (1968-1969) input transformers from microphone preamp of vintage Schlumberger console. Friend of mine that will actualy finish, test and mod my SB4000 unit, told me those are really high end and impossible to find, but useless in SB4000 output stage, so i find two others (picture below) wich are from some really expensive peace of old audio equipment from TV station ( a gentleman that let me have those is retired last 25 years, and he does not remember from wich device are those...).

Sorry if i did not helped, but as I told, I am not skillfull audio electronic guy. I know some very basic, but even soldering will be done by a professional. I am just an electronic music producer, with some passion for experiment

Best regards

Ivan

 

[sheadstedford]

Thank you for the reply!
I am also an electronic music producer that is experimenting. This transformer switch idea sounds brilliant!
Even if the character is harsh or suble it will have its use somewhere especially in electronic music.
And beig switchable is awsome.
However i dont know what transfkrmers are suitable fir the job. I will resrarch and post watever i find out.
Best of luck!
Shea

 

[ik01]

As far as i know, typicall output transformer is 600 Ohm, 1:1 ratio. I dont know any  other technical specifications that are needed. Switch will be built in on back side. i dont want to drill beautiful front panel of SB4000 . 2 years ago i had GSSL. amazing compressor for drums, synth stabs and whole mix. Good old GSSL I had have no sidechain, and all fancy extras SB4000 has, and still sounded great!

Yeah man, good luck to you aswell.

Best regards
Ivan

 

[sheadstedford]

Im putting a tube drive into the input of my sb4000 this week. 6n2p-ev srpp to be exact.
Cant wait to see wat its like, a switchable tranny on output seems like the cherry on top of an already iced caked!

 

[ik01]

will you have tube front end only, or switchable input? (or possible 2 physical inputs)

 

[sheadstedford]

Tube only input is the plan, switching is too difficult for a novice like me, id like to be able to switch it tho, just dont know how

 

[ik01]

well, maybe with two separete physical inputs without switch. I am not shure could it work good. did you recieved all your parts from Canada? I am still waiting them to be send (some delay with meter...)

 

[sheadstedford]

Yea i ordered aaaaages ago tho, still waiting for the meter tho. Should be about a week hopefully.
Im trying to get info on the switching possibility of the input to only have the need for 1x stereo input