API312 with OEPS

I made PCB which the same like original APi312 preamp,and I use OEPs A2623E on input and output!

I use zobel network for OEPs ,I found that zobel for OEPs is 800pF and 22k!

But I have 12dB peak on 12kHz ,and dont know what to do!

My friend told me to put LOAD RESISTOR and I tried but nothing!!!!I used 150K for LOAD

So guys who have some advice is welcome!!!!

The A262A3E is an input transformer. It will distort badly as an output transformer. First remove the A262A3E from the output and measure the response again.

Cheers

Ian

Yes A2623E is input and output trannie!

Thanks Ian!

Ill try!

iprovlek said:

Yes A2623E is input and output trannie!

Thanks Ian!

Ill try!

Click to expand...

I cannot find this transformer number. Can you please provide a link.

Cheers

Ian

It's probably a typo

is it the A262A3E?

http://www.newark.com/oep-oxford-electrical-products/a262a3e/transformer-audio-1-1-6-45-6-45/dp/24M0686

Electrical characteristics:
Winding ratio: 1+1:6.45+6.45
Impedance:
Primary 150W parallel connected
600W C.T. series connected
Secondary: 6.25kW parallel
25kW C.T. series connected

http://www.farnell.com/datasheets/1872254.pdf

Whoops said:

It's probably a typo

is it the A262A3E?

Click to expand...

That's what I thought but the OP keeps using A2623E. I searched OEP's web site and and got a message "This datasheet is available only on request".  I emailed them for the datasheet. Not arrived yet.

Cheers

ian

I think that is problem in output trannie!

For output I use A262A3E but reverse , output from opamp goes on PRIMARY of A262A3E and I get great sound but with
12db on 12Khz!

If is output reverse so from opamp to SECOUNDARY to PRIMARY sound is DISTORT!!!

And datasheet from OEP transformers is wrong , so because that Forthmonkey have problems in first version of his API preamps!

And I thinks that output trannie must be with lower RATIO 1:1 or so!

Whoops info about A262A3E is good...

And thanks guys on eefort!!!

Today Ill tray Ian what you told me connect output witout output trannie!!!

LIke I said in my first reply, the A262A3E is an input transformer. It's power rating is just 1mW so it is bound to distort at the output.

Cheers

Ian

Whoops said:

It's probably a typo

is it the A262A3E?

http://www.newark.com/oep-oxford-electrical-products/a262a3e/transformer-audio-1-1-6-45-6-45/dp/24M0686

Electrical characteristics:
Winding ratio: 1+1:6.45+6.45
Impedance:
Primary 150W parallel connected
600W C.T. series connected
Secondary: 6.25kW parallel
25kW C.T. series connected

http://www.farnell.com/datasheets/1872254.pdf

Click to expand...

 

That would be hell of an input/output transformer to saturate. ;D

All W should be Ohm.

sahib said:

Whoops said:

It's probably a typo

is it the A262A3E?

http://www.newark.com/oep-oxford-electrical-products/a262a3e/transformer-audio-1-1-6-45-6-45/dp/24M0686

Electrical characteristics:
Winding ratio: 1+1:6.45+6.45
Impedance:
Primary 150W parallel connected
600W C.T. series connected
Secondary: 6.25kW parallel
25kW C.T. series connected

http://www.farnell.com/datasheets/1872254.pdf

Click to expand...

 

That would be hell of an input/output transformer to saturate. ;D

All W should be Ohm.

Click to expand...

I'm sorry Sahib, not having English as a first language, could you explain it better?

thanks

Obviously a typing error but you represented the impedances in W which stands for Watt.

sahib said:

Obviously a typing error but you represented the impedances in W which stands for Watt.

Click to expand...

I've copied the specs from canford or farnell

sahib said:

That would be hell of an input/output transformer to saturate. ;D

All W should be Ohm.

Click to expand...

When you want that big iron sound, you gotta go for the big iron!

Whoops said:

sahib said:

Obviously a typing error but you represented the impedances in W which stands for Watt.

Click to expand...

I've copied the specs from canford or farnell

Click to expand...

Both of which do not say in W.

Regards,

C

sahib said:

Whoops said:

sahib said:

Obviously a typing error but you represented the impedances in W which stands for Watt.

Click to expand...

I've copied the specs from canford or farnell

Click to expand...

I see now what happened
I copied the text from the technical data sheet pdf, it seems when you do that the "Ohms" character gets replaced with "W"

Both of which do not say in W.

Regards,

C

Click to expand...

I see now what happened
I copied the text from the technical data sheet pdf, it seems when you do that the "Ohms" character gets replaced with "W"

thanks for pointing that out Sahib

so it should be:

Electrical characteristics:
Winding ratio: 1+1:6.45+6.45
Impedance:
Primary 150ohm parallel connected
600ohm C.T. series connected
Secondary: 6.25kohm parallel
25kohm C.T. series connected
DC resistance (+/- 15%):
Primaries total: 20.6 ohm
Secondaries total: 1143 ohm
Inductance, measured at 1kHz, 0.27V:
Primaries 125mH min. per winding
Secondaries: 5.2H min. per winding

I solve problem with this api 312 preamp with oeps!

I bought A262A7E for output and everything is now great!

And preamp sound great!!!!


So definitely A262A3E isnt good for output in this circuit!


So guys thanks a lot!!!!

You should check the distortion at low frequencies into a 600 ohm load. Although this transformer is rated at 100mW at 300Hz (+20dBm) it is only rated at 1mW at 30Hz (0dBm). So you may get some bass distortion.

Cheers

Ian