What Toroid in Mackie M1400

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K-amps

K-amps

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#1
I just picked up a Toroid for a Mackie M1400. Does anyone know what VA rating it is?

Mackie says it is a 250wpc RMS into 8 ohmpower amp, but it has a +/- 90vdc tap... With that you could design a 350 watter... Does the Mackie use MOSFET's? Why such low OP rating?

It does have dual supplies i.e. 65-60-0-60-65vac so either it is MOSFET with the higher supply feeding the inputs/Drivers and the lower feeding the OP stage... or a Class-H BJT design... which is it?


regardless, whats the VA of it's Toroid, anyone know?

K-thanks!
 
#2
#5
Yup... I am growing too old...

By the way, do you guys think the 65vac tap on the Toroid, is high current enough to be used with an OP stage?

i.e. is it a piggy back from the 60vac tap with the same gauge wire?
 
#8
Wildly guessing from the schematic, it's likely not the same gauge.

In the PSU section, the 90V rails are stacked on top of the 80V rails with 25V capacitors (and not smoothed with reference to ground separately). This was done because cost was an issue. If quality was the main concern, the 90V rails would have gotten 100V capacitors to ground.

If they skimp on the second most expensive part in the PSU, why not on the most expensive? We're talking "the new" Mackie, after all...

I could be wrong, though. 😉

Cheers.
 
#9
Actually then I would speculate that it IS the same gauge wire. As it's a lot easier, quicker and cheaper to wind a few extra turns onto the end of a winding than do a whole new one even with thinner wire.

To be honest with the windings as they are and assuming the worst about wire gauge, it's a useful transformer anyway - the higher voltage pre stage is a good way to gain a bit better efficiency.
 
#10
Why is it easier? Primary and secondary windings are already of different gauge, so changing wire (or rather winding rig) between windings is not an issue. But cost, weight and size are.

And I didn't intend to say the transformer is actually bad. 🙂
I just said that cost is a higher issue in this amplifier design (as it always is in the professional world!).

Cheers.
 
#11
My thoughts were same as Richie00boy. A few extra turns are cost effective (especially time and labor wise) than terminating the winding; then winding another layer of lower gauge for the extra volts.

I have seen many trafo's done this way where the extra 5v taps were the same gauge.

Now if it were a 200 or 400v tap, that I would guess would be a lower gauge because of obvious reasons. My guess is the breakeven point would be roughly 40-50% of higher voltage, use same gauge, over that, rewind with lower gauge.

Especially in a Donut where you have more winding "space" than a E+I core.

But I have been wrong before.:angel:
 
#13
Thanks for the responses, guys. 🙂


I have seen many trafo's done this way where the extra 5v taps were the same gauge.
Click to expand...

I have seen the opposite, too. Mostly in asian mass market products with tailored transformers for multiple output voltages of various current capabilities all from the same primary. Note that all of this description fits a modern Mackie product. 😀


I used to work in a transformer factory.
Click to expand...

Alrightee. 😀

Cheers.
 
#19
Not going to be worth it...

quick calculations show 8 ohm clipping (using the 90v taps) to be about 379 watts (modelling from Mackie's own numbers with the 80v tap) or lower...

The unmodded 565 can clip at 383watts 8 ohms...

Might be worthwhile for 555ii mods... for someone...
 
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