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The Amazing Fet Circlotron by Mike Rothacher
The Amazing Fet Circlotron by Mike Rothacher
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Old 7th November 2008, 10:05 PM   #91
stoolpigeon is online now stoolpigeon  Australia
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Hi Mike,

I would appreciate that.

I have some efficient speakers so low power is fine. I am also used to an original Zen which I think has much higher distortion anyway.

thanks, sp
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Old 8th November 2008, 10:51 PM   #92
Michael Rothacher is offline Michael Rothacher  United States
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The Amazing Fet Circlotron by Mike Rothacher
sp:

With 12V rails I saw .03% THD at one Watt hitting 1% at around seven Watts. That's keeping the 1.2A bias and no circuit changes.
I leave it for you to decide if that's okay.
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Old 9th November 2008, 01:12 AM   #93
stoolpigeon is online now stoolpigeon  Australia
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Thanks Mike!

I will proceed.

sp
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Old 27th April 2009, 10:15 AM   #94
gaborbela is offline gaborbela  Canada
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Hello
It is possible to use 2SK1529 power mosfet instead IRFP240.
EUVL U are familiar with these Toshiba mosfet would you please let me know .
If I have to change some resistor values please let me know .
Thank you very much .
Greets .
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Old 27th April 2009, 02:42 PM   #95
bear is offline bear
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The Amazing Fet Circlotron by Mike Rothacher
Thought I might mention that if the original photo posted is not fan cooled, then the heatsink is apparently rotated 90 degrees from its proper position for natural convection operation...

Also, the bottom of a heatsink used for natural convection needs to have an unimpeded source of air - usually a volume equal or greater than the open area of the heatsink (on the bottom) in order to not create a resistance that reduces the convection...
and an equally free route out the top.

For most class AB amps it doesn't matter usually because the heat load is usually lower and if highish usually transitory. Class A is constant heat (of course).

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Old 27th April 2009, 03:26 PM   #96
el`Ol is offline el`Ol  Germany
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May I post a simplified schematic of the patented Thorens circlotron amp, which is the official reference of a German hifi magazine (more or less confirmed by 6moons)?
Attached Images
File Type: jpg circlotron.jpg (42.3 KB, 1110 views)
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Old 27th April 2009, 06:59 PM   #97
Nelson Pass is offline Nelson Pass  United States
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The Amazing Fet Circlotron by Mike Rothacher
You will want to ask Mike.

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Old 27th April 2009, 08:15 PM   #98
EUVL is offline EUVL  Europe
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You can use 2SK1529Y but you might find that the trimpot to bias the Vgs of the MOSFET has to be lower in value. Perhaps you trim it first and then consider replacing it with a fixed resistor afterwards. 2SK1529 has about 1.5V less Vgs than IRF at the same current.

As to the Thorens schematics, you'll find out more about his "invention" than this HiFi magazine schematics. He did not invent the circlotron circuit he used, just the bias stabilisation, which is essentially a common-mode servo plus a differential servo.

Amazing what people can patent these days, including method to identify certain genes of a pig !!!


Patrick
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Old 28th April 2009, 08:31 AM   #99
Samuel Jayaraj is offline Samuel Jayaraj  India
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Patrick (EUVL) perhaps, you are the only one other than Nelson who can comment about the sound of the Circlotron vs F5 at the time, having built both; would you like to go ahead.

Thanks.
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Old 28th April 2009, 01:04 PM   #100
Michael Rothacher is offline Michael Rothacher  United States
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The Amazing Fet Circlotron by Mike Rothacher
I've listened to the F5 very briefly, but not side-by-side with the Circlotron. I suspect they're very similar. One day I'll build an F5 and make a real comparison, but alas, I haven't been able to do much hobby-wise lately.
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