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Old 20th July 2018, 06:36 PM   #1321
MEPER is offline MEPER  Denmark
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Quote:
Originally Posted by oreo382 View Post
If you have a dc supply you can push a known current thru and measure the voltage across the coil.

Very good idea! will do that. I have a DC supply with current limiter and A-meter built in. So I can set the current to e.g. 2.5 or 3.0 A and then measure the voltage…….or just read it at the V-meter but probably good make a control measurement with a quality DMM.
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Old 21st July 2018, 02:00 AM   #1322
dewdrop is offline dewdrop  Singapore
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The Jensen caps are 6800 uf / 63 VDC. Have four as I will use two pr. channel in parallel. I picked them up direct at the Jensen factory close to Copenhagen. I was served by the 3. generation of Jensen. They are two 3. generation Jensen brothers which own the factory now. These 6800 uF are not listed at the web. They are not cheap…...approx. 120 USD each incl. 25% Danish tax. I like to use the local suppliers. The chokes were also picked up at the factory.
I can't wait to hear feedback on your monster creation. Good luck!
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Old 21st July 2018, 06:42 AM   #1323
MEPER is offline MEPER  Denmark
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It will take some time. I also have plans for the Korg preamp and BA3 front end and a couple of 2 x 24 VDC supplies. So I guess some months in the future......but will post how it goes…….when there are some progress…….
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Old 21st July 2018, 07:24 AM   #1324
MEPER is offline MEPER  Denmark
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If the MoFo was designed with a conventional source resistor and the rail voltage was raised to e.g. 40 VDC how would such an amp perform compared to the current version? …..I know it will be less efficient and burn a lot of power in the source resistor. Does the choke give some "sound qualities" which a conventional design does not...e.g. more "ear friendly" distorsion pattern? ….what about damping factor will that be the same? …..the load has to be seen as parallel to the impedance in the mosfet?
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Old Yesterday, 05:58 AM   #1325
PRR is offline PRR  United States
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Choke-loaded can give efficiency to 50% in theory. In the form proposed here, over 40% before distortion is audible.

Resistor-loaded is at-BEST 8.5% efficient, and probably under 6% in real life at audible distortion.

Upshot is that you must build 6 times bigger, ENORMOUS dissipation and quite a lump of power.

True, compared to 80 pound iron, the resistor does look an incredible bargain.

See the FAOW plan for resistor-coupled. Scale it from 1+W to 16W, basically 10X power, 10X heatsink, around 3X voltage and current. 57V 6A. I'd have to refine those numbers because the two topologies differ, but 57V 6A and 300W heatsinking does give one pause.
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Old Yesterday, 06:17 AM   #1326
MEPER is offline MEPER  Denmark
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Ok.....so to make it with resistor load is more a theoretical than practical project. The FAOW has very high distortion relative to the bias current which is quite high. I understand how the resistor loaded version works with about half rail voltage at the source of the mosfet and then an absolut need for an output cap. The MoFo was for me so special that it was a "must build" to see for my self how it works. I still does not have the full understanding that you have almost 0V DC at source of the mosfet where you take the output from and only have single rail but the choke gives you the "negative part" of the rail voltage to get double swing.
Do you know if the MoFo clips symmetrical or the negative half clips first?
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