| Optical |
What chip for ~+/-65VDC ??
I have a bunch of fairly high current audio transformers that i want to put to good use :)
...but i havent seen a chip that goes above ~+/-40V (3886)
the OPA chips are even lower i think..
what else is there? |
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| AudioFreak |
| Have a look at 4732 / 4780 / 4781. |
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| carlosfm |
| quote: | Originally posted by AudioFreak
Have a look at 4732 / 4780 / 4781. |
:eek:
Nooooo!:bawling:
These are no good, max. voltage 84v (or +/- 42v).
:angel: |
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| iCebReakEr409 |
I think STK Chips go higher STK4048 for example.
Too expensive though :) I don't even know if they produced any more. |
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| AudioFreak |
| quote: | Originally posted by carlosfm
:eek:
Nooooo!:bawling:
These are no good, max. voltage 84v (or +/- 42v).
:angel: |
Sorry about that, the National website says +- 84V so it's a bit misleading. |
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| UrSv |
| If transformers are identical you can use two in series and get a good +/- 32.5 VDC? |
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| V/IR |
| Regulate the voltage down, you'd be amazed at the improvement it makes. |
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| djk |
"take a look at the LM12cl here"
So what? ±40V, what do you think 80V max means? |
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| Mark A. Gulbrandsen |
I think the STK series has a chip thats at that plus and minus voltage rating. I recently picked up some STK4042XI power chips for 2 bucks each. Has anyone here ever used these power chips?
I do know that several self powered biamped speakers use this chip.
Mark |
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| djk |
http://www.diyvideo.com/forums/atta...p?postid=182299
One opamp driving a single pair of BUZ900D/905D will give 250W.
Magnatec also makes single packages with both N and P devices, one device makes a 250W amp.
One pair of the XL4S will make a 500W amp.
These are lateral MOS so a simple resistor sets the bias, and in the Transnova the case is grounded. |
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| Optical |
Thanks for the responces guys, yeah i think the transformers were originally powering STK441's (?) from memory..
but ive never seen them for sale anywhere local unfortunatly
djk, can you elaborate on your post?? |
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| Optical |
Oh, and how would putting the transformers in series halve the voltage? im not sure i follow, im guessing theres a little trick to it which ive missed..
Also, how would i regulate 65V down to 40V at high current? I dont know much about regulators which could do this.. |
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| djk |
"djk, can you elaborate on your post??"
Magnatec makes lateral MOS in complementary pairs up to 250V.
They are available with one P and one N per package or just P and just N in one package.
Dissipation ranges from 125W~500W per package, current from 8A~32A.
Since they are lateral MOS the source is hooked to the case of the package.
In the schematic shown the sources are grounded, no insulator required. More importantly, no high voltage front end required.
To drive 500W into 8R all that is needed is about ±3V out of the opamp to drive the gates. The gain of the XLS4 (the biggest ones) is about 4A per volt, so 3V gate will give about 12A source current. 12A peak = 8.4A RMS, (8.4A squared)*8R = 576W.
Hook a 1K resistor between the gates of the FETs for bias, hook the output of the opamp to either gate. Run the opamp off whatever voltage is best for it, ±15V~±24V. Run a resistor from each gate to the respective opamp supply rails, this sets the idle current in the output stage. You can use a pot and then select the closest value fixed resistor.
This scheme is, of course, the basis of the TransNova amplifiers Jim Strickland designed for Acoustat and Hafler.
It may be adapted for BJT, but would require more parts. |
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| UrSv |
Primaries in series?
If you have for instance 120 VAC primaries and say one 48 VAC secondary then taking two such transformers connected to 120 VAC will effectively have half the mains voltage, i.e. 60 VAC, across each primary and consequently each secondary will be half the original which in this case is 24 VAC. In case there are two secondaries on each transformer I would connect those in parallell if they are dual and not centertap transformers. |
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| Optical |
oh right primaries in series :rolleyes:
they are CT transformers, but should be ok in parallel |
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| Praise! |
If you want good quality and don't mind putting output
transistors then have a look at Burr Brown OPA445.
Alternatively, you can cascode the opamp and get
the output transistors to sense the supply current.
This way you can have any voltage you want.
Quality is low though.
James Yung
Praise! Audio |
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