BPA-200 w/ six chips working w/ pics!

[Mattyo5]

rail voltage is 27+-. The sinks get warm but not hot. The amp does distort at higher volume levels. I'm running them into 8 ohm speakers, and it doesn't seem like they are putting out the 150-200 wpc that I was expecting. Too small of a bridge? Too small a PS? The gain is high though

-Matthew K. Olson

[janneman]

Originally posted by Mattyo5
[snip]and it doesn't seem like they are putting out the 150-200 wpc that I was expecting.[snip]-Matthew K. Olson

How do you know?

Jan Didden

[UrSv]

With 27 V rails and an ideal amplifier bridging perfectly you should get some 180 W. With a nornal amp with some losses and less than ideal bridging I'd say that <100 W is more likely the expected power.

[Mattyo5]

How do I know, well, i had anthony holton's symmetrical 400's running at 70v rails....approx 200 wpc. No matter how high I cranked it...no distortion...my ears gave out before the amps. This amp, no where near that level. Maybe 100 wpc is more like it... but good point, i have no objective test right yet.

-Matthew K. Olson

[li_gangyi]

might be ur PSU being unable to supply enough curent

[Mattyo5]

Well, i hope thats not it, but I have a sneaky suspision that it is the limiting factor. The reason I hope its not a big factor is that i wanted to keep these chassis small...and putting a big fat toroidal in there would be way cool, but difficult and way to packed as far as spacing goes.

-Matthew K. Olson

[MWP]

For 180W, your mains transformer should be >300VA.

The ICs will also clip the output if they get too hot.
Dont test the heatsinks to see how hot they are... test the amp ICs.
If you burn your finger on them, then they are probably too hot.

A bridged LM3886 amp i made a while back (42V rails), started clipping at 40W RMS output power.
As soon as i removed the mica insulating washers the LM3886s could then keep cool and i got the full 220W RMS out.

[Mattyo5]

Well, those trannys are supposedly 200va each in parallel. I'll have to use an IR gun to see the temp of the chips. One of the reasons I used 3 chips in parallel is for spreading of the heat better than 2 chips, but they are plastic package. ... More testing needed

-Matthew K. Olson

[MWP]

One of the reasons I used 3 chips in parallel is for spreading of the heat better than 2 chips, but they are plastic package. ... More testing needed [/B]

Oh... well thats probably it then.
The TF packages are no good at higher power levels.

[janneman]

Originally posted by Mattyo5
How do I know, well, i had anthony holton's symmetrical 400's running at 70v rails....approx 200 wpc. No matter how high I cranked it...no distortion...my ears gave out before the amps. This amp, no where near that level. Maybe 100 wpc is more like it... but good point, i have no objective test right yet.

-Matthew K. Olson

Yes, the difference between 100W and 200W is just 3dB, which is considered barely detectable by the average listener (not to imply that you are avarage).
So, before you start replacing parts and transformers and whatnot, it would pay to measure the undistorted output voltage with a load resistor on a scope & multimeter, to have at least some idea of what's up.


Jan Didden