API 312 Thread!

[mikefatom]

The gar's output transistors (the large rectangular ones) should get warm indeed.
What are the voltage readings at the DOA sockets?

Don't worry about your english! It is just fine. 

Cheers,

Mike

 

[ilfungo]

The gar's output transistors (the large rectangular ones) should get warm indeed.
What are the voltage readings at the DOA sockets?

Don't worry about your english! It is just fine. 

Cheers,

Mike

The gar's output transistors (the large rectangular ones) should get warm indeed.
BD139 or BD140?
however, they are both cool

What are the voltage readings at the DOA sockets?

+ 15.90 / - 15.98

 

[mikefatom]

BD139 or BD140?:  Both should get warm

+ 15.90 / - 15.98 at the sockets: Yup, that looks good. That tells us that there is something funky going on with the gar2520s.

Double check everything on the gar's and if you don't find anything, post some hi-res pictures of the DOA and we can try to help.

Good luck,

Mike

 

[ilfungo]

Hello Mike

 

[ilfungo]

GAR2520 1

 

[ilfungo]

Gar2520 2

 

[ilfungo]

GAR2520 3

 

[ilfungo]

GAR 2520 4

 

[ilfungo]

Hello Mike
This is a sample starting from 0 to max level
THAKS for your help!!!






http://www.megaupload.com/?d=JMAK4A2S

 

[mikefatom]

Well, I can't find anything wrong with the gar2520 from the pictures you posted.  There is either nothing wrong with them or I am missing something.  I will look them again later though.

I suggest that you post links to those pictures in the gar2520 build/help thread and hopefully Gary will be able to help further.

Also, one thing that I could not confirm from looking at the pictures is if the BD139 and BD140 are not swapped.

Good luck and keep us updated!

Cheers

Mike

 

[scottlangendyk]

Hey guys,

I'm wondering if there's a good way to measure the amount of usable gain I'm getting from my 312 clones.

I find that when I record bass through a DI (Radial JDI - passive), I have to crank the gain on the 312 right up to even get a useable signal from the live level output.

Any ideas?

Thanks,
Scott

 

[ilfungo]

My APIs are alive! ;D ;D ;D
Thanks MIKE , JSTEIGER and all the forum for your help :-*
it was a stupid problem
I had not connected in parallel  the AE2622
primary...
I thought it was already done on the PCB
THANKS!!!

 

[ilfungo]

last step
I read that I use a Zobel capacitor 220pF
Ceramic?
or I have a capacitor 240 pf mica ....
What do you recommend?
thanks

 

[mikefatom]

last step
I read that I use a Zobel capacitor 220pF
Ceramic?
or I have a capacitor 240 pf mica ....
What do you recommend?
thanks

That's great news! Congrats!

I am still intrigued though: Are the gar2520s getting warm now?  How are the noise and signal levels?

Re Zobel Cap:  I've been using ceramics and film caps succesfully (when using the EA2622 that is).  I'm sure that a 240pF mica would be fine as well.

Have fun with the pres!

Cheers,

Mike

 

[ilfungo]

Thanks Mike
everything seems to work well
in half an hour I go to my studio and try them .....
let you know ....
thanks

 

[scottlangendyk]

Hey guys,

I'm wondering if there's a good way to measure the amount of usable gain I'm getting from my 312 clones.

I find that when I record bass through a DI (Radial JDI - passive), I have to crank the gain on the 312 right up to even get a useable signal from the live level output.

Any ideas?

Thanks,
Scott

Bump

 

[mikefatom]

Hey guys,

I'm wondering if there's a good way to measure the amount of usable gain I'm getting from my 312 clones.

I find that when I record bass through a DI (Radial JDI - passive), I have to crank the gain on the 312 right up to even get a useable signal from the live level output.

Any ideas?

Thanks,
Scott

Bump

What do you mean by usable?

The JDI will attenuate (step down TX) as well as change the impedance of your signal.  Depending on the type of pickups on your bass (passive or active) and their driving capabilities (output impedance), you will find that the signal out of the JDI is very low (in the case of a passive, high impedance pickup) or fairly hot (in the case of an active pickup with booster/preamp circuit).

It's hard to tell without knowing more.

You can easily get 70dB of gain out of a 312 pre if you use the correct components.

Cheers,

Mike

 

[scottlangendyk]

Hey guys,

I'm wondering if there's a good way to measure the amount of usable gain I'm getting from my 312 clones.

I find that when I record bass through a DI (Radial JDI - passive), I have to crank the gain on the 312 right up to even get a useable signal from the live level output.

Any ideas?

Thanks,
Scott

Bump

What do you mean by usable?

The JDI will attenuate (step down TX) as well as change the impedance of your signal.  Depending on the type of pickups on your bass (passive or active) and their driving capabilities (output impedance), you will find that the signal out of the JDI is very low (in the case of a passive, high impedance pickup) or fairly hot (in the case of an active pickup with booster/preamp circuit).

It's hard to tell without knowing more.

You can easily get 70dB of gain out of a 312 pre if you use the correct components.

Cheers,

Mike

Not sure what I meant by usable either haha.

My 312's appear to be working great, but having no first hand experience with any others I want to measure the amount of gain I'm getting out of them, to verify that my pre's are operating as they should.

As far as the bass level goes, I'm relatively certain the bass I'm using has a particularly weak output. I'd still like to know how much gain I'm getting out of the 312's though.

 

[ilfungo]

today I tried the API 312 in my studio ....
They sound so wonderful!!
I want to say thanks to all the forums and the people who helped me
in particular
Thanks Mike for your patience .....

 

[mikefatom]

[...]

Not sure what I meant by usable either haha.

My 312's appear to be working great, but having no first hand experience with any others I want to measure the amount of gain I'm getting out of them, to verify that my pre's are operating as they should.

As far as the bass level goes, I'm relatively certain the bass I'm using has a particularly weak output. I'd still like to know how much gain I'm getting out of the 312's though.

There is a fairly easy way to calculate the gain that should be available on the pre.

What input TX do you use? Does it have dual primaries?  If yes, are they parallel or series connected?
What 312 board/circuit are you using? What values are you using for the gain setting resistors (in the feedback network)?
What output TX are you using? What ratio is it connected for?


To measure the actual gain you're getting, you could:

Measure the output voltage for a given input voltage (use something like a 5mV peak-to-peak sine wave) and plug the results in this formula:

Gain in dB = 20*log[V(out)/V(in)]

Cheers,

Mike