Eisen 312 clone & ap2623-1 output transformer.

[bigwillz24]

Hi I have a Eisen API type clone that I'm having a small issue with. There is not nearly enough gain in this thing. I have to crank the pre up all the way to get a decent signal with a condenser mic not usable with a dynamic.

I have a 2520 opamp, a Jensen JE 110K-hpc input transformer, and a AP2623-1 output transformer. I was reading here that you can wire the output transformer as 1:2. I'm wondering if that will help me. And if it will exactly how do I wire it?

Thanks

 

[Sender]

[quote author="bigwillz24"]Hi I have a Eisen API type clone that I'm having a small issue with. There is not nearly enough gain in this thing. I have to crank the pre up all the way to get a decent signal with a condenser mic not usable with a dynamic.

I have a 2520 opamp, a Jensen JE 110K-hpc input transformer, and a AP2623-1 output transformer. I was reading here that you can wire the output transformer as 1:2. I'm wondering if that will help me. And if it will exactly how do I wire it?

Thanks[/quote]

I'm not too farmiliar with the AP2623, but one would assume it's the same as the AP2503 minus one secondary winding. So try this....

Orange - Lo
Blue - Hi
Yellow & Green - Tie together to GRND

You're standard center-tapped orientation. Look at the this API 312 and see how it's wired. Exact same scenario.

Now I don't have an exact 'pin out' of the transformer so I can't be 100% sure, but most likely this will work.

 

[Samuel Groner]

It will not help you much--6 dB more is not a big deal. You've got something else wrong, check the wiring of the gain pot or the value of the feedback resistor (I'm not familiar with the preamp though).

BTW, blengs to the The Lab.

Samuel

 

[bigwillz24]

[quote author="Samuel Groner"]It will not help you much--6 dB more is not a big deal. You've got something else wrong, check the wiring of the gain pot or the value of the feedback resistor (I'm not familiar with the preamp though).

BTW, blengs to the The Lab.

Samuel[/quote]

sorry maybe a mod will move it for me.

 

[CJ]

what is value for R 12?

 

[cactus]

I've built quite a few of these things and it sounds like there's a cold solder point somewhere.
No joke, EVERY TIME I had low output it was due to poor solder joint on output tranny.

Resolder.

If I crank the volume on mine (75101APC -> 25*20 -> Crimson Audio) I can hit red talking into a 57.

 

[EisenAudio]

Or maybe the input transformer is backwards? I've made that mistake with the older Jensens when there is no pin 1 marking.