Anyone got schematics for the Cambridge Audio model P40? - Page 2 - diyAudio
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Old 13th September 2005, 11:59 AM   #11
dnsey is offline dnsey  United Kingdom
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I don't know if the P40 is similar, but my Cambridge had sliding selector switches operated by a sort of 'flat Bowden cable' arragement, which would be very difficult to source.
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Old 13th September 2005, 04:18 PM   #12
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Thank you very much!!
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Old 13th September 2005, 08:43 PM   #13
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Thaks very much Forr.
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Old 24th September 2005, 06:38 AM   #14
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How good is the Sound Quality of the P40?
What would you compare it to?
I don't know much about this amp when was it made, it looks like it comes from the early 60's
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Old 25th September 2005, 12:20 PM   #15
forr is offline forr  France
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The first Cambridge amplifiers were one of the first :
- having a very tall fascia which, then used by Mark Levinson preamps.
- using a toroidal transformer for the power supply, another manufactuer doing this was Tandberg.

~~~~~~~~ Forr

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Old 23rd February 2017, 03:53 PM   #16
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Default twelve years later...

... a thread hijack!

I've just obtained an 80's version of the P40, based on the same circuit I believe. Unfortunately the fuse ratings are not stated, either the power one or the two speaker protection ones. Someone has been inside this before, one speaker fuse fitted is 1A the other 5A! Does anyone know the correct ratings please?

Thank you in advance.
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Old 23rd February 2017, 04:02 PM   #17
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Default this is the one

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Old 24th February 2017, 06:29 AM   #18
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If it is indeed the same P40 circuit, a single 55V power supply rail will be in use and the audio output will be via a 2,500uF capacitor. This was augmented with an unusual form of current limiting in the original too - see sch. and comments on Paul Kemble's site: A Paul Kemble web page - the Cambridge Audio 'P' series amplifiers.

An output capacitor makes the need for fuse protection less critical but from the attached image ( courtesy of the same site as your pic of the later P40 model), I don't think it is the same design. Perhaps it shares some elements but this version appears to have a dual rail power supply, 2 pairs of output devices and no output cap. If it looks the same internally and the rail voltages measure more like +/- 25V, I would treat it as a different design and use 2A fast blow fuses in lieu of the 2.5 amp rail fuses said to be used in P50.
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File Type: png CambridgeP40 (1980).PNG (548.6 KB, 18 views)

Last edited by Ian Finch; 24th February 2017 at 06:32 AM.
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