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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 3rd Aug 2021, 10:04 am   #1
pedro_couvreur
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Join Date: May 2020
Location: Oeiras, Portugal
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Default QUAD 303 protection diodes

I am repairing a Quad 303 and visited some sites and posts about it.
It came to my attention that some 'improved' driver boards use 3 diodes instead of just one for MR104 and MR105, to protect the driver transistors.
Does anyone knows the reason for this change ?

Best regards, Pedro Oliveira
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Old 3rd Aug 2021, 12:11 pm   #2
Trevor
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Default Re: QUAD 303 protection diodes

this will enable the amplifier to drive lower impedance loads
The 303 standard circuit peaks into an 8 ohm but current limits into 4 ohm
you have to be careful though as the output transistors can overheat or overcurrent
Trev
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