api312 input transformer question

[Jonkan]

Im a newbie that could need and would really appreciate some advice.

im thinking of building two channels of Baumans api312 clone, but have a question i was hoping you could help me with.

Ill be using an original api transformer (clone i think) for the output, and have the option of either using an OEP262A3E or an original api input transformer (again, clone i think, but im not shure).

Im leaning towards the oep one, since i dont have much money and the oep is alot cheaper (and im poor). But i dont want to build something that sounds inferior to the original.
I dont really care if it sounds exactly like the original, as long as it sounds damn good! :wink: So being true to the original for other reasons than it sounding "better" than the oep solution is of no concern.


So Im wondering... will the oep sound worse than the original input transformer or maybe just different but still in a good way? Do you think or is it more a question of preference and flavour?
Or would i be better of shelling out the cash for the "real deal" ?


anyone that has built this with the oep? what do u think?

/Jonas

 

[MikoKensington]

Fabio is the one to ask I'm pretty sure he did his prototyping with the OEP.

 

[NewYorkDave]

[quote author="Jonkan"]Ill be using an original api transformer (clone i think) for the output, and have the option of either using an OEP262A3E or an original api input transformer (again, clone i think, but im not shure).
[/quote]

If it's an original, how can it be a clone?

The two terms seem mutually exclusive, at least to me

 

[Jonkan]

fabio: any thoughts on the subject?

new york dave: good question, maybe its an original clone :wink:
We have a small group in sweden that just started out and are building this preamp as our second project. Were buying the parts together. And I wont be ordering the parts myself. I just got offered to buy an original transformer or an oep one.
I can ask the guy whos buying the parts to clear things up for me (he also hangs here, so maybe he can answer this himself). Maybe i just misunderstood, and the transformers are the original ones... Also, english is not my native language, so its easy for me to write stuff that can be misunderstood, please bear with me. :wink:

 

[Bauman]

Sure!
My studio partner and I just loved the OEP with Melcor. Of course, when you change to Cinemag or Jensen, you get shocked. Very different bottom end, depth and other subjective stuff. But keep in mind we are 2 dirty rock guys. The OEP prints some character for sure and I have no doubt that after trying some nice transformers I got from Tamas, I'll have at least 2 channels with OEP back. The Jensen ones have all that detail you will love on some things and
you can have it with Cinemag for half the price.

To sum up: go for it, you will get a very decent micpre.

cheers!
Fabio

 

[mesmer]

The cinemag is $38. How much is the oep? Does it have a nickle core?
Peter

 

[Jonkan]

great, thanks for the advice!

Im a rock guy myself, so some colour is nice

Do u think that building 2 channels melcor/oep will be versatile enough to be used on many channels in a mix (since i dont have any other "good" preamps at the moment i will probably use the api clone for most of my overdubs after recording basic tracks using a soundcraft 400b mixer). Or will there be too much colour, in a more "effecty" kinda way that you would only use on some tracks that needed some more grit?

I really need something thats a bit versatile, but not too clean sounding.


/Jonas

 

[Category 5]

Just thought I'd chime in too. I haven't tried all the other transformers that Fabio has tried, but I'll have to agree that the Cinemag is fantastic. The one listed in most of the threads is the dual (right?) impedence one, but I have the 150ohm impedence one is my modules and they sound just like real 312s. I am using the real output transformer and real 2520s too, so I don;t know how much the input tranny has to do with the sound, but I'm sure it's at least a moderate factor.

The model I am using is the CMMI-8PCA.

Enjoy your new preamps! I don't imagine it will be easy to find a source they don't sound excellent on!

Shane

 

[soundguy]

api used two different transformers that sound very different on the 312's through the years, so going for an "original" sounding 312 is somewhat of a moot aspiration IMO. Pick the transformer that sounds good to you and fits your budget, as this is apparently what API did in the 70's... I like the 2622 best, others prefer the reichenbach and currently api prefers a jensen, so its all in the ear of the beholder. I think the amps sound way different with a 1:10 than a 1:7 or a 1:4. I would be much more focused on figuiring out how that is going to impact you more than what company to go with. Higher turns is going to give you a sparklier sounding amp, lower turns you'll be able to wrench more distortion out of the opamp.

you said wrench.

dave

 

[NewYorkDave]

Actually, that should be the other way around--but that's probably what you meant.

Lower turns, better high frequency response.

Higher turns, hotter signal at the input of the opamp.

 

[soundguy]

no, in at least the case of the api circuit, with the higher turns, you are getting more input to the opamp, so you wind up using less gain from the circuit and the sound is a lot cleaner sounding and the api has a nice sparkly high end in that case. With the lower turns, there is less level present at the front end of the amp, so you can turn the gain higher and get more distortion out of the opamp which IMO is where the 2520 shines, but everyone likes something different so...

dave

 

[NewYorkDave]

That makes sense, too. Lower gain: more negative feedback, lower distortion and flatter frequency response. Higher gain: the inverse of the above :wink:

 

[rafafredd]

So, it sounds like a big part of the "color" of the API preamps comes from the opamp itself.

Nice to know it.

But,

Keep in mind that usually, a higher turns ratio at the input, lowers the noise level.

 

[CJ]

I think the API/Melcor stuff has a sweat spot. At certain gain settings and transformer ratios you will get the tone you want. The gain control on the API stuff is kind of crude in that it does not change the frequency response of the op-amp like you have in a tone compensated gain scheme ala Telefunken V76 or G-9 or UA 610.
At low gain settings, the API might get a little muddy and lack detail. So having the right mic to match up with the opamp is also important. At high gain settings the preamp might sound a little harsh, and your noise will go up, so you need a mic that will put out a decent level for what you are recording.
In other words, a SM-57 might not get you the best results with a low level vocal signal, but might be good when micing a rock guitar. A condenser mic will give you plenty of gain for vocals, but you would have to turn the gain down quite a bit if you put it next to your Marshall cab, which would not be using the API circuit to it's fullest.

Either way, I am still splitting hairs here because it is hard to make that thing sound bad. Wait and see!
cj.

 

[Kev]

[quote author="NewYorkDave"]... If it's an original, how can it be a clone?[/quote]

Sometimes it can be tricky to find just the right word.

hyperthetically there is Bob.
He works for a transformer making company. He may even own it. Pablo asks him to make some trafos but his design is not as good as it could be. So Bob says I'll make something for you. Bob makes these things all day long and knows what is what . Pablo has his company, BQJ, as top priority and wants it good and wants it kept a secret.

Bob says .. :thumb:

Tom says to his old friend Bob, " I have a project but I need a trafo. "
"No problem I'll give you one of my favourite cores with my favourite turn."

:green:


What is original ?
Is a Neumann Mic from the wrong side of the Wall still a Neumann ?
Which side of the Wall was the wrong side ?

 

[robomatique]

The cinemag transformer, is that the CM-75101A ?

http://www.cinemag.biz/mic_input/mic_input.html

Maybe that is better and/or cheaper than the sowter "api312 input transformer"?

Sowter seems to be quite expensive...

Anybody has experience of both?

Robert

 

[Guest]

on the cinemag - check Fabios site (I think it's fabios)

http://www.thediypill.phx.com.br/diy_api312.htm

 

[Bauman]

Nice stuff about input trannie + opamp combinations!!

Yep, Cinemag CM75101APC is my main choice for 312. You can get more info here (none at their site):
http://www.thediypill.phx.com.br/forumfiles/cm75101_data.pdf

I´m doing 8 channels right now, 4 of them with CM75101. I´ll also test Cinemag CMMI-5C, CMMI-10B and a JT13k7 then will post some comments.


cheers!
Fabio

 

[robomatique]

[quote author="Bauman"]Nice stuff about input trannie + opamp combinations!!

Yep, Cinemag CM75101APC is my main choice for 312. You can get more info here (none at their site):
http://www.thediypill.phx.com.br/forumfiles/cm75101_data.pdf

I´m doing 8 channels right now, 4 of them with CM75101. I´ll also test Cinemag CMMI-5C, CMMI-10B and a JT13k7 then will post some comments.
[/quote]

Sounds nice, anybody know the price?

Robert

 

[fum]

Based on the 312 trackside, and the footprint of the CM-75101a, it appears that the PC mount pinout doesn't work with the api board. I see six holes on the pcb, 8 pins on the traffo, based on the artwork, you'd probably want to go with the leaded version of this over the pc mount, if you're working with original artwork.

Guess I should clarify, I'm lookin at the api 312-3 artwork


ju