API 312 Thread!

[bubba_b]

I need some help in selecting trafos for my 312 project. I haven't started yet, but am sourcing parts. There's so many different options I'm finding for the input trafo that I don't know where to begin. It's not like I can go to a shop that has a rack full of handmade gear with all the different options and listen to them and say, "yeah, I like that one best". So I'd like y'all's opinion. If it helps, I'll be using this pre primarily for rock guitars and some vocals, but mostly electric guitars (kinda why I chose the API for this).

So....any suggestions on which trafo sounds best for this type of application? Beefy, not too shrill or sharp, smooth mids is what I'm lookin' for.

Oh, and if there's any other parts/procedures I could know about to help obtain that kind of sound, I welcome those suggestions, too.

 

[asm]

bubba,

i went with the cinemag input trans cause i didnt want to bother with an overseas order with Sowter, and Prodigy Pro store didnt stock that sowter model number.
i think jensen makes one, but i ordered 8 ch worth and thats just WAY to much money when buying jensens.

cinemag was quick and not to bad price wise, i think they were about 40$, the guy hand winds all the stuff, usualy starts when you call him and order. can come off as a di*k at first but he's really a nice guy and tries to help you out once you talk to him a bit.

i cant comment on the sound yet as i still have to build the opamps, but the cinemags were pretty close to the original input trans windings i believe and those arent shrill or high. so i think your safe.

where are you planning on getting output trans since its hard to get profile4840's now?

goodluck.
t

 

[louder]

alo bubba
i used cinemag 75101 apc input,and sowter clone for output.
sound wise,i like my 312`s as much to say the least,as my3124+.
also used melcor for opamp.
best regards
pedro

 

[drpat]

:grin:

 

[drpat]

...

 

[dasbin]

Cinemag makes a good output transformer too. SCA uses it in their kits now instead of the Profile. Apparently the Cinemag one is a little more expensive but better-built than the Profile. The model number is CMOQ-2S, $25.82 ea. I've got two on the way along with CMMI-8PCA's. Using them in Fabio's boards, though I'm not sure how to wire up the CMMI-8 as it obviously won't plug straight in - PCB wasn't designed for it.

 

[drpat]

...

 

[bubba_b]

Thanks, guys. BTW, where do I get Cinemags from in the good ole US of A?

 

[JustinS]

At the risk of sounding patronising :grin: Google??

All right... They're actually an American company:

www.cinemag.biz

Justin.

 

[Bauman]

Hey,

Can you hot glue it (upside down) and then connect the leads??? I believe that you can order it with leads.

There's a 3-4mm hole next to input transformer so any transformer with leads can be mounted using a metal L shape there...

I did the boards for only one Cinemag model, the CM75101APC. After that I have managed to get some other models and found then all amazing! CMMI-10B is very interesting also...
After all the test I have decided to update the board to rev4 next month, to fit any Cinemag input transformer. For instance, the CMMI-2C can be used with Forssell 992 opamps instead of JT-16-B, the CMMI-5C can be used with JLM99V or with Tamas GainBloak or even Melcor, so on. But for rev3 you have to get the ones with leads...

cheers!
Fabio

 

[dasbin]

I didn't specifically order the ones with leads but I figured I should just be able to solder some leads on myself without much difficulty... am I wrong? They haven't arrived in the mail yet.

What I'm looking for is info on which pins go to which holes on the PCB. In other words, I already figured I would be wiring the leads to the PCB holes, I just wanted to know which ones. And also if an RC network is necessary. Thanks again.
Cinemag's datasheet shows the trafo in a few "example setups" with an RC network on each but I'm not sure if this is needed in Fabio's setup.

 

[Bauman]

CMMI-8 on R312 boards, if using leads:

(1)brown goes to white
(4)red goes to blue
(5)orange goes to pink
(8)yellow to AGND
(6)black goes to brown
(7)white goes to empty hole next brown.

the one with PCB pins is just like CM75101APC... it´s also in the CMMI-8
datasheet.

4 5
3 6
2 7
.1 8
bottom view

For RC/CC value you need to check the datasheet:
http://www.cinemag.biz/mic_input/CMMI-8B3.pdf

If the datasheet shows no RC/CC don´t use any. For instance, CMMI-10B
just need a RL=150k, no RC/CC...

hope this helps!
Fabio

 

[dasbin]

Sweet, that helped a ton, thanks Fabio.

Looks like RL=100K, RC=15K, CC=100pF

And PCB version should just plug straight in! Great!

 

[Bauman]

the one with PCB pins is just like CM75101APC...

by what I meant, they have the same pinout BUT not the same pin spacing... :?


cheers!
Fabio[/quote]

 

[bubba_b]

I've got the v3 BOM and schemo for the 312 and the v1 BOM & schemo for the power supply. There's several resistors on the PS list that are listed as ???'s. Anybody know what these values are supposed to be or have an updated BOM? They're listed as: R1, R2, R10, R11.

 

[louder]

alo bubba
look at earlier pages,where it is discussed.
best regards
pedro

 

[bubba_b]

I'm having trouble sourcing the BC414 on the Melcor and the 2520BC opamps. Looked at Mouser and Digikey, but neither one had it, unless I just don't know how to look (search for BC414 came up 0 on both sites). Is there a suitable replacement or option?

 

[Bauman]

Stick with BC550C and BC560C. They are easy to find anywhere and will sound the same.

:guinness:
Fabio

 

[bubba_b]

Well that's easy. Thanks Fabio. BTW, got my boards and they're halfway stuffed!

 

[daArry]

Hey,

My 312 project is finally coming to fruit at last! I etched up n drilled a pcb in the back yard as it was such nice day today...here's a cpl shots - still need a few odds n ends but gettin there:

Layout n features inspired by Fabios efforts :thumb: - also added option for LL1636 on input (as well as the others) and made use of a bunch of relays i had to hand already...

Hope to complete this in the next cpl weeks!

:guinness: