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C Audio SR707 MK1
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shaun1264 View Drop Down
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Points: 325 		Post Options Post Options   Thanks (0) Thanks(0)   Quote shaun1264 Quote  Post ReplyReply Direct Link To This Post Topic: C Audio SR707 MK1
    Posted: 26 December 2023 at 8:48pm
Does anyone have the specs or a pdf/scan of the original C Audio SR707?  is it the same as the MK2?  Thanks.
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simonp1100 View Drop Down
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Points: 1150 		Post Options Post Options   Thanks (0) Thanks(0)   Quote simonp1100 Quote  Post ReplyReply Direct Link To This Post Posted: 27 December 2023 at 11:39am
The SR707 Mark 1 & Mark 2 are the same spec. The difference is cosmetic only.

Front & rear panels mostly, all internals are the same (maybe an update on the soft / start PCB).

Wink
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shaun1264 View Drop Down
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Points: 325 		Post Options Post Options   Thanks (0) Thanks(0)   Quote shaun1264 Quote  Post ReplyReply Direct Link To This Post Posted: 27 December 2023 at 12:54pm
Thanks Simon.  

The SR707 I have just barley makes output wattage into a 8ohm load (around 470 watts into 8 ohms, mains supply at 240v and not sagging)  allowing the THD to reach 0.5% instead of the spec 0.1% THD.   Overall distortion when backed off is very low.  0.0035%

 Not sure what the acceptable DC offset is but im measuring around 18mV on both channels.

Also there seems to be a resistor put across both high and low side on the gates?  No idea why or if these was a factory spec.  
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simonp1100 View Drop Down
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Points: 1150 		Post Options Post Options   Thanks (0) Thanks(0)   Quote simonp1100 Quote  Post ReplyReply Direct Link To This Post Posted: 27 December 2023 at 2:59pm
Hi,
The resistor looks like an add on, and is used to lower the bias between positive & negative gate drivers (value on the circuit is 1K). 

Bias is set to 150mA.

The specs for a 707 in 8 ohms is rated at 488 Watts (both channels driven), so it sounds like yours is in spec.

Tongue





Edited by simonp1100 - 27 December 2023 at 4:06pm
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shaun1264 View Drop Down
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Points: 325 		Post Options Post Options   Thanks (0) Thanks(0)   Quote shaun1264 Quote  Post ReplyReply Direct Link To This Post Posted: 28 December 2023 at 4:00pm
Thanks again.  Just seen the schematic and that explains it.  

Just need change the fans as one of making a knocking sound and the other is a bit noisy even after oiled up 
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