Adding a third input to a differential input stage?

[maudio]

Originally posted by janneman



Seems you are looking for something like this:

Jan Didden

Looks interesting, but ad1830 seems to be obsolete? Can't even find a datasheet. Maybe there are any more recent chips like this?

For the differential amp BB's INA134 could be interesting.

[maudio]

Oops.

AD8130 is a lot easier to find the the 1830

[powerbecker]

Originally posted by maudio
Oops.

AD8130 is a lot easier to find the the 1830

I worked with both Ad830 - AD8130.
Problems arised with the relationship :
max. Inputvoltage / Distorsion / Noise!
Regards
Heinz!

[powerbecker]

maudio:
"The happy result after closing the loop is a flat response to >60 khz using a 1:150 transformer, which normally would be impossible at such high stepup. I have a perfect 1khz square over the esl. It should be possbile to raise stepup even further allowing for more output voltage "

Do You have some more specs from Your transformer
like Inputvoltage, Primary inductance, coupling inductance,
C-Load, Secundary-R....? In short : enough to create a model!

"I can have full output swing up till 2 khz which should be enough"

Hmm...from a more "technical" view not very impressive

Regards
Heinz!

[maudio]

Do You have some more specs from Your transformer
like Inputvoltage, Primary inductance, coupling inductance,
C-Load, Secundary-R....? In short : enough to create a model!

This is the model I came up with after extensive measurements on my (diy) trannie. Lprim is around 11mH, Rprim is zero (or very close), Lleak is around 7 uH, stepup around 1:145, Rsec ~ 340 ohm. It's a large c-core with two coilformers. Input voltage: It should handle around 40 Vpp @ 100Hz before hitting saturation.

In series with the primary I have a 2.5 mH coil and a 5.6 ohm resistor.

"I can have full output swing up till 2 khz which should be enough"

Hmm...from a more "technical" view not very impressive

Agree on that, my guess is that peak levels in music will start dropping above a khz or 2. Hopefully at 6db/oct
But now I am running the thing with music I see it sometimes clips on sharp 's'-sounds in female voices. Then again, my amp still runs of my bench power supply which is a bit underrated for the job. So maybe not al is lost yet

[powerbecker]

"In series with the primary I have a 2.5 mH coil..."

Good and bad!

Thank You for the model, when I find the time I like to play with it!
Regards
Heinz!