best topo for 25W class A into 1 ohm resistive load?

[AndrewT]

Hi,
with a load that low, how well would a transformer work?

 

[jacco vermeulen]

Sanken 2SA1215Y and 2SC2921Y have become my favorite outputs.

And the best bang for the buck.

Any chance of posting the final schematic ?

 

[Wavebourn]

Today I have to solder 36 wires, because 2SC5200 / 2SA1943 are usable up to 3 amperes only. 🙁

2SA1215 look similar...

 

[mlloyd1]

linesource:

thanks for sharing.

re. #1 - this is dissappointing. for grins, some time ago, i disconnected the servo in my borbely servo 50 amp (similar schematic with mosfet outputs) and thought it sounded better. without servo, i got about 70mV offset though - more than i want, but not too bad. i always thought the diff amp current sink/source control was a clever way around that.

re. #2 - i like this one too. the kinda recent thread about the blowtorch and some extended listening i did to some Ayre products lately got me messing around with ideas for the next power amp: jfet with bipolar folded cascode, bipolar outputs, balanced all the way through. and no global feedback, of course.

re. #4 - nice tidbit. i still have parts in my NOS stash of lateral power mosfets and Motorola bipolars. i don't think my wife will let me buy any new ones. but, what she doesn't know won't hurt her (or me) ...

re. #5 - hmmm. somebody else told me this not long ago. interesting.

thanks again and keep checking in ...

mlloyd1

I built a point-to-point breadboard and learned the following:
...

 

[LineSource]

Hi,
with a load that low, how well would a transformer work?

I am using a 0.15 ohm to 4 ohm transformer now, but a vector impedance bridge shows phase shifts which I wanted to experiment removing with a specialized DIY Class A amp... I use a +/- 5V LC filtered power supply. The output uses 8 pairs of 150 watt Sankens.

 

[LineSource]

Almost finished the PCB layout:
1) Both active and passive ISO 226 loudness contour circuits. ISO 226 is a room adjusted modern version of the anechoic Fletcher-Munson work.
2) 3-way LR8 crossover at 80Hz and 3,200Hz using Pass discrete JFET opamps
3) 0.15 Ohm Midrange ribbon direct drive 32-watt Class-A amp using dual differential topo.
4) 1.0 Ohm Tweeter ribbon direct drive 16-watt Class-A amp using super-sym JFET-Bipolar folded cascode topo which provides 2x the 4.4V midrange power supply voltage. This allows sharing one 35 AMP CLC filtered +/- 4.4V power supply.
5) The Bass amp is a 200 watt Class-D module driving 2 ohm load from four Lambda TD15S.
6) Planning to put all into one chassis at the speaker.

I’ll post an update if it doesn’t smoke and measures well.

 

[tiefbassuebertr]

check out this thread:
http://www.diyaudio.com/forums/soli...s-paralleled-place-one-output-transistor.html