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Old 21st June 2012, 05:04 AM   #571
lhquam is offline lhquam  United States
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Quote:
Originally Posted by buzzforb View Post
Very nice. How do the measured numbers compare to simulated ones?
Overall there is decent agreement between the simulation and the actual circuit, but I am not sure I have enough experience with this circuit to answer the question definitively. I have some doubts about the accuracy of the MOSFET and MUR diode models. There are some issues with the LTSpice results I haven't figured out. Perhaps there are LTSpice convergence parameters that need tweaks.

One thing that both the simulation and the actual circuit show is that reasonably high bias (> 1A) is needed to get THD below .005%. Both show that the Turbo diodes greatly reduce THD at high power levels versus the non-Turbo at the same bias.

I have not yet done any listening tests of the version with diodes. I have been listening for more than a month to a nearly identical balanced F5 pair without the diodes. It sounds very good.
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Old 28th June 2012, 04:10 AM   #572
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Originally Posted by lhquam View Post
One thing that both the simulation and the actual circuit show is that reasonably high bias (> 1A) is needed to get THD below .005%. Both show that the Turbo diodes greatly reduce THD at high power levels versus the non-Turbo at the same bias.
Since we are squeezed to limit bias and source resistance, has anyone considered 4 diodes in series-parallel? That way the people with enough heat sink can push the bias up higher and still keep the diodes from conducting at idle. There would be about 0.6 volts more drop at high power (depending on temp and current), but still have more power and less distortion than no diodes at high power. My main drawback to that is the extra cost of double the diodes and heat sinks.
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Old 12th July 2012, 11:14 AM   #573
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Has anyone tried these boards from Jim’s Audio? Personally I’d rather buy from the store here than ebay (the guy must be making some money out of this all be it a small amount), but these seem to be the only turbo boards available.

Mosfet pure class A amplifier thick PCB turbo V2 stereo !! | eBay
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Old 12th July 2012, 02:15 PM   #574
Nikitas is offline Nikitas  Greece
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Guys, silly question follows:
Is the f5 a constant current source amp (like what is described in Pass'es article "current source amplifiers and sensitive/full range drivers)?
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Old 12th July 2012, 02:22 PM   #575
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No, a current source amp is volt in and current out.
F5 is a voltage amp, volt in and volt out.
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Old 12th July 2012, 02:29 PM   #576
Nikitas is offline Nikitas  Greece
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Thanks jacco.

Any examples of ccs amps that are available in this forum?
BA1 for example, is it a ccs?
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Last edited by Nikitas; 12th July 2012 at 02:30 PM. Reason: clarifying
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Old 12th July 2012, 02:48 PM   #577
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No, the BA1 front end is voltage in and voltage out, output stage is push-pull.

For a current source amp, the output stage can not be symmetrical (top & bottom look the same)
F1 and F2 are current source amps, constant current source on top, bottom is transconductance stage (volt in, current out).
Current difference between top and bottom goes to the loudspeaker, so volt in and current out.
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Old 12th July 2012, 03:00 PM   #578
Nikitas is offline Nikitas  Greece
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dank u!
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Old 12th July 2012, 03:12 PM   #579
nrg2009 is offline nrg2009  United States
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very helpful, thanks Jacco.
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Old 12th July 2012, 03:13 PM   #580
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Parakalo, calispera.
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