transformers for passive eq

[mich]

Hi,
Im planning on building the gyraf pultec but without the output stage,
so i can plug it into different mic preamps that i have.
(like newyork dave's passive eq) :thumb:

been wondering about the txformers i should use.

im guessing a 600/600 for the input,and somthing like 10K/600 for the out?

is the output inpedance (before the output stage) about 10K?

thanks

 

[NewYorkDave]

600:600 for the input if your source can drive a very low load impedance. Otherwise, use 10K:600 and accept the additional 12dB of loss. Use 10K:600 for the output. In either case, the loss of the circuit will be substantial; I believe the nominal loss of the filter section itself is around 20dB.

 

[mich]

Thanks Dave,

in case i'll use an 4k/600 that i have (military trafo),whats the load resistor i should use for flat response?

-im going from eq out into green pre for example.

i'll soon post some pics of the front panel made with transperancy film printed with an inkjet printer-its first time im using it - its easy and cheap and results are good.

 

[mich]

The Pics:

 

[radiance]

Very nice! What about a pic from them gutz?

 

[CJ]

Stock Pultec is

600:600 input (HS-56/66/66V)
20K:80K output (HS-29)

Good luck on the 29.

You should figure out which make-up amps you will be usuing mostly, solid mis-state or vaccum voodoo.

Three years ago, pics of a front panel would have gotten you a page of ooooh's and ahhhh's.
But due to an ever increasing number of insanely good projects, this rooom is a little tougher to work.

 

[mich]

Very nice! What about a pic from them gutz?

not much guts to this thing.....just the gyraf pcb (thanks again jakob :thumb: ) toko inductors ,and XLR in and out,and the awaiting transformers...

i have an OEP 1604 (600/600) that i thought of using for the input (its very small :roll: ),will see how that goes.if not i'll try to use a huge Freed transformer (420/600) from evilbay....

the nice thing about this project is the box...I tried minimizing costs to almost nothing-using spare parts that i have, so i scabaged some Aiwa HiFi preamp,and went to the metal factory and had them cut me a 19" aluminium panel from leftovers....talk about cheapo diy......financial situation not so good.......cost me about 4$ for 2 panels .......

 

[kvintus]

[quote author="CJ"]
Three years ago, pics of a front panel would have gotten you a page of ooooh's and ahhhh's.
[/quote]


You can get an ooooh from me. That's a really nice panel! Good job!

/Anders

 

[gyraf]

Why not simply run the output un- or pseudo-balanced? After all, you won't be running long cables from this box to the preamp..

 

[mich]

Why not simply run the output un- or pseudo-balanced? After all, you won't be running long cables from this box to the preamp..

thats a posibility i'll definitly check.thanks.

one more thing i forgot to mention is that if anyone engaged in this project wants to have the graphics file just ask-its in psd or tif format,be happy to share.