Which N Or P Power MOSFETs ?

Audio schematics are always such fun. The DC bias of the output fets is hilarious.

--

John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 

  Claude Bernard

These days, are they really making full range (20 Hz .. 20 kHz) speaker elements that can handle 1 kW power levels ?

If not, what is the point of making kW class full range amplifiers ? If you have to divide the audio spectrum to multiple speaker elements a passive crossover becomes awkward at such power levels. Better use active crossover so each amplifier can be optimized for required frequency range (and power levels).

up for discussion. the other day I found a fatal error in it and I fixed t hat. it was ot that it owuld blow up, it is that it owuld not do what I wan t it to do.

t the f*ck ahead but when I see someone with a fifty grand turntable I thin k "You know, they might just have money".

ge, they will spend that.

dy talked to lawyers about this, just because I could. Anyway, there is no discussion on topography, or complimentaries. All the output devices will b e the same polarity.

the best reliability. Now I remember PNP silicon transistors going before t he NPNs. The opposite was true of germanium to some extent, and fact they m ade few of them probably because of that.

n use P channel I can use a + supply. Well if it is really just as reliable . If N channel is more reliable I have to go wit a negative source which I can do, but to me it is like thinking upside down.

k to that company with over $300 each, and who knows on the power transform er. But Digikey won't know. They just sell the stuff. (not the transformers though)

ier:

I can almost understand most of the bipolar stuff. I mostly assume that if I build something similar, I'll replace everything but the drive with opamps.

We don't know what the load is.... maybe he's built his own speakers too. George H . (who wonders if he's even built a prototype.)

To pass for the audio guys at this power level, a pair of 3-500Z's is needed, or maybe a pair of 813's with a pair of 866A's in the power supply ...

--

-TV

Yes also because all the graphs and safe operating area curves for modern switching MOSFETs are of little use when they're used in a linear application.

When I was at school I had a look in the plant room at a sports stadium. It was more interesting than the games. They had rows of 813s driving the 100V line PA system. They were also favoured by the local pirate radio station - driven by rotary converters powered by large lead-acid batteries as there was no mains on hill-tops.

John

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** Been doing it for several decades. Cabs with two high power 15 inch drivers and a large format horn cater for 1kW amps fine.

The 15s will be 8 ohms type and the horn driver 16 ohms, with a 18dB /oct x-over and passive EQ. It may also use incandescent lamps for overloaded protection in series with the feed.

** Be silly to make them narrow range . ** It actually very straight foward.

..... Phil

some bit brain f*****ad wrote: =============================

** FFS post *only* on topics you know something about.

That will narrow the field right down to SFA.

..... Phil

The amplifier classes up to at least H are a pretty useful framework, I think.

We commonly use classes A, B, C, D, and H.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Potentially pretty nice, but super hard to read--a digital Panteltje tribute no doubt. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Electricity works better as electrons than it does as holes, so you'll likely see better performance per dollar from M-cnannel parts.

I'm farly sure someone has alteady said that.

There's people here who do want to discuss electronics, and perhaps immagine that they could offer pointers to improve the design.

--
  Jasen.

Then the problem becomes the output transformer.

--

John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 

  Claude Bernard

Really, Phil, you are unreasonably harsh on people merely because they are foul and stupid. Not everyone can be born sweet and smart like us.

--

John Larkin         Highland Technology, Inc 

Science teaches us to doubt. 

  Claude Bernard

=================================== Phil Allison

** Sweetness in an un-affordable luxury on usenet.

.... Phil

I hadn't realised that John Larkin though that he was as sweet as Phil Allison, or as smart.

The real problem here is self-delusion, and I'm not sure that I've got mine under control either.

--
Bill Sloman, Sydney

The SOA curve in most switching device datasheets tells you e.g. that you can push 20 amps at DC with the MOSFET saturated and the case at 25 degrees. Amazing stuff. I try to run all linear power amps pushing 20 amps with the case at 25 degrees personally

I said _speaker_ _elements_, I was not referring to speaker boxes.

That is three elements and some sort of crossover.

With varying audio levels and hence variable voice coil temperature and hence resistance, this will interact with the passive crossover reactive components, which will alter e.g. crossover frequencies.

The bass amplifier needs to drive high power (especially in a "small" enclosure) for a long time at a time and sometimes quite reactive loads around the speaker resonance. Often the efficiency is an issue.

Much less power is needed to drive mid/high elements, so efficiency is not so critical, due to higher efficiency of the element and much reduced content in the audio signal. More important parameters are frequency response, low distortion and low noise. No need to handle high power bass tones.

The nice thing about active speaker boxes is that you do not need long speaker wires. Perhaps this is the reason why audiophools do not like active speakers, since they no longer can argue with each others which exotic speaker cable is the best :-).

Or to avoid confusion I mean the linear region in which Rds on is defined. Anyway point is the data sheets for switching devices don't usually give you the continuous operation curves.