SYMEF amplifier

[zxgravediggerxz]

Originally Posted by drowranger

Oooooh.....yes! I have made torture test using 2x 6.5 inches of speaker with a total impedance of 6ohms.mind you again, that the impedance that makes the amplifier put into stress and not the size....:...........
when I said 40v that is D.C. rail supply.

Originally Posted by nakamoomin

I think that's the same equation I used on the previous page..
So that looks correct to me.

I was under the impression that the Voltage numbers (eg. 30-0-30) are given @ the specified rating (eg. 300VA), and that sometimes idle voltage can be a little higher (to account for resistance in the coil) Vunloaded = Vloaded + I*Rc....................

Originally Posted by OnAudio

@ Digger

This is much better Antek - AN-5230. I know someone using +/- 60VDC with 8 ohm load however I like a large safety margin. +/- 40VDC to +/- 50VDC keeps you safe and helps the amplifier drip honey all the way.

Thanks guys!!!

Originally Posted by Tekko

you wind it yourself out of magnet wire.

How about this?
Power Inductors Ind 1uH 3A Radial Leads

or

Power Inductors RFI COIL 1uH 4A

[OnAudio]

Too small , not air core. It will saturate easily. This amp is capable of supplying 20A during a transient easy.

[OnAudio]

Magnet Wire
Magnet Wire, Plain Enamel (PE), Solderable, Class 130, 1 lb spool, 16 AWG CONWIRE-16MAG-1.0LB - All Spectrum Electronics
Amazon.com: Magnet Wire, Enameled Copper Wire, 1lb Spool, 16 AWG, 0.0524" Diameter, 120' Length (Pack of 1): Industrial & Scientific

There are many cheap sources

If pressed disassemble this

http://www.parts-express.com/wizards...TOKEN=90127471

Do for 1uh.(18 turns,16awg-thickness in 1/2" diameter)

[meanman1964]

Is there a schematic that matches the component layout,to avoid errors.The part numbering of the scheme isn't the same as the board.

[c12mech]

Thanks guys.

Next up is to figure out a heatsink size. Does everything on that edge of the board need to attach to the sink and do they all need to be isolated?

This will be my first solid state build. I have done tubes in the past, so this heatsink stuff is all new to me.

[Nico Ras]

Originally Posted by OnAudio

Too small , not air core. It will saturate easily. This amp is capable of supplying 20A during a transient easy.

20 amp....3200 watt into 8 ohms An air-core inductor cannot saturate, else you will be magnetising air.

[nakamoomin]

Originally Posted by OnAudio

Too small , not air core. It will saturate easily. This amp is capable of supplying 20A during a transient easy.

This is given that the speaker has a Z of 4 ohms. And that the PSU is supplying +/-40 V (80V p-p).

U=I*R => I = U/R
Imax = 80V / 4 ohm = 20 A.

Which in turn means:
Pmax = 80 V * 20 A = 1600 W (!!!!!)


At 8 ohm load:
Imax = 80 V / 8 ohm = 10 A
Pmax = 80 V * 10 A = 800 W (!!)

@zxgravediggerxz
So listen to the experts: Use Air-core

[Nico Ras]

According to Mr. Ohm's law P=I^2 x R; therefore P = 20^2 x 8 = 3200 watt, or into 4 Ohms P=1600 watt.

These numbers seems a little Chinese (or Greek as they say) to me. I stand to be corrected, but to store 3200J a 1 Farad Cap is required (since the caps are in series for each 40V rail 200 x 10 000uF caps would do the trick at a cost of around US$1800 at Mouser.)

[nakamoomin]

Originally Posted by Nico Ras

According to Mr. Ohm's law P=I^2 x R; therefore P = 20^2 x 8 = 3200 watt, or into 4 Ohms P=1600 watt.

These numbers seems a little Chinese (or Greek as they say) to me. I stand to be corrected, but to store 3200J a 1 Farad Cap is required (since the caps are in series for each 40V rail 200 x 10 000uF caps would do the trick at a cost of around US$1800 at Mouser.)

Your calculations are correct, but with this amp using +/- 40 VDC you will only be able to draw 10 A if you use 8 ohm speakers: 80V (p-p) / 8 ohm = 10 A

But with a +/- 60 V PSU (as suggested in this thread) you can theoretically pull 15 A with an 8 ohm load. That means 15^2*8 = 1800 W (!!!).

To get 3200W out of an 8 ohm load you would need to use +/- 80V PSU.

These numbers are what's called PMPO rating (Peak Momentary Power Output) and describe the maximum instantaneous power possible. A lot of "Chinese" manufacturers use this number to inflate their performance instead of using RMS (Root Means Square) rating which says something about continuous power.

[sonidos]

Can other output transistors be used? I bought some OnSemi BJTs in TO-264 packages that are close in specs. I can't remember PN and I'm at work right now.

Re. the comment about air core inductors, I believe OnAudio was misunderstood and he meant to say the ones suggested at Mouser are not air core and will saturate. He is actually recommending air core type.