Yamaha's kind of ERCO: Zero Distortion Rule "ZDR" (M50, M70, A520) - diyAudio
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Old 12th September 2010, 10:40 AM   #1
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Default Yamaha's kind of ERCO: Zero Distortion Rule "ZDR" (M50, M70, A520)

Yamaha's kind of ERCO: Zero Distortion Rule "ZDR" (M50, M70, A520)

How works the circuit from the attachement (power amp section of the IA "A-520") ?
What is the aim of the diode network between in- and output of the output butter stage?
Where I can find hints of the winding parameter and the appropriate core material behaviour for a ZDR transformer

I have find only this threads in this case:
yamaha ns m-50
Bob Cordell Interview: Error Correction (post #3424)
Yamaha M-70 vs. M-80 - AudioKarma.org Home Audio Stereo Discussion Forums
Attached Images
File Type: jpg Yamaha A520 left.jpg (101.6 KB, 252 views)
File Type: jpg yamaha_a520 silver.JPG (10.9 KB, 234 views)
File Type: jpg Yamaha A520 Power Supply.jpg (167.3 KB, 241 views)
Attached Files
File Type: pdf C_...A-Yamaha A520.ckt.pdf (38.0 KB, 121 views)

Last edited by tiefbassuebertr; 12th September 2010 at 10:43 AM.
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Old 12th September 2010, 11:08 AM   #2
wahab is offline wahab  Algeria
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The diode network will limit the current to 3A, but only
on the negative going of the signal.....

Are you sure that C163 is not connected to Tr111 collector ?..

"Zero THD" like will mostly arise from tremendous NFB ratio,
since the design is a 3 stages voltage amplification..
So much gain available that they managed to insert the
tone controls in the NFB loop...
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Old 12th September 2010, 01:43 PM   #3
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Quote:
Originally Posted by wahab View Post
The diode network will limit the current to 3A, but only
on the negative going of the signal.....

Are you sure that C163 is not connected to Tr111 collector ?..
Yes (see attachement). The complete Service Manual you will get about "hifi engine"
Thanks for the advice regarded the diode network
Attached Files
File Type: pdf yamaha_a-520-PA_service.PDF.pdf (107.6 KB, 95 views)
File Type: pdf yamaha_a-520-PAII service.PDF.pdf (70.0 KB, 74 views)
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Old 28th October 2010, 07:44 AM   #4
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Which other brands uses this kind of error correction?
And where I can find hints of the winding parameter and the appropriate core material behaviour for ZDR transformers?
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