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CAMBRIDGE AUDIO AZUR 540R V2 tuning / modification
CAMBRIDGE AUDIO AZUR 540R V2 tuning / modification
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Old 10th December 2009, 02:38 PM   #1
sviru is offline sviru  Poland
diyAudio Member
Join Date: Oct 2004
Question CAMBRIDGE AUDIO AZUR 540R V2 tuning / modification

I have Just bought CA AZUR 540R V2. Very well sounding AV amp.
It sounds good - Like in most reviews. Plenty of power, bas, thick sound.
But – there is some loss of detail and space. Especially compared to my moded Musical Fidelity A2 (but I must admit that it sounds superb).
I have a schematic for 540R and it is quite clear why there is a loss of detail (especially on analog stereo input).

It seems that every analog input – except 6.1 CH DIRECT (which goes straight to VOLUME CONTROL) –
is going Through DSP > D/A>OPAMP>VOLUME CONTROL > AMP.
From the schematic I have found that signal from D/A is entering very weak opamps JRC2068.

I want to replace them with AD8620 /AD8066 which are detailed and fast. I would probably go with the 8620 since it is more stable.

Next thing is there are four! 10uF capacitors in the signal path. Which is a LOT. The worst part is that those caps are really cheap stuff. Samaxon I thing. Piece of crap. I want to replace them with BlackGate to increase detail, top end etc.

I would like to remove 2 of 4 of these capacitors from signal path. I did this to my previous DENON AVR 3801 with superb results (more clarity, refined sound, great space and detail). But it was a little different design.

1. I would like to remove and short caps after opamp especially (I guess I have to measure DC at the output of the opamp and check is it safe > my question is how much DC is “safe” at the output of the opa to remove the caps C6 / C5?

2. Caps C7/C8 I would like to short but at the pdf of the volume chip there are required – so I would replace these with BlackGate.

3. C17/C18 – caps after volume control… signal goes from C17/C18 directly to amp through caps C1/C18 – a litte too much I think. Which cap is safer to remove? C17/C18 or C1/C18 – how much DC is allowed on the output of the volume control to do this? Is a value of 10mV safe to remove C17/C18?

Thank you very much for reply. I have done it at the past and it is WORTH IT. I like this amp but I now It can be better.

The main thing is to remove at least 2 caps from the signal path – after this it will sing!
Thanks for your help and advice!
Attached Images
File Type: jpg CAAZUR540R2.jpg (352.0 KB, 660 views)

Last edited by sviru; 10th December 2009 at 02:41 PM.
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Old 16th June 2010, 11:30 AM   #2
clear and blue is offline clear and blue
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Join Date: Jun 2010
Hi Sviru,

I am expecting my 540r v2 to arrive any day now and was interested enough by your post to register here. I have little experience with electronics but maybe a reply is better than none at all.

Are you only considering making the changes for the front left and right channels (stereo) or did you only show these for simplicity?

Regarding the safety of removing caps from shock point of view, as long as you are down below 5V say, you should be fine. If in doubt, carry on draining them. 10mV certainly should be fine. Don't take me on this but I believe you are only likely to see capacitors holding a charge of hundreds of volts in a tube amp?? Best to measure first anyway.

Would experimenting with lower values of capacitors not be a good idea before removing them completely? A change of brand is likely to help but surely bigger differences will be made in changing the cap's value.

The opamp. . . is the function of this to stabilise the voltage of the analogue signal to line level, like a recovery stage?

I believe the main problem with high DC on the volume control is that it can make scratchy sounds as the volume knob is turned.

I would be interested to hear more from you on how the changes have worked for the amp.
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Old 5th January 2011, 12:11 PM   #3
joeyjojo9658 is offline joeyjojo9658
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Join Date: Jan 2011
Hi both,

I found this thread from a google search. I am also a 540R v2 owner wishing to get some information on mods.

Have either of you guys had any luck with this?

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Old 8th July 2011, 11:38 PM   #4
lynx1981 is offline lynx1981
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Join Date: Sep 2010

i am also wondering what the results are ?
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Old 22nd August 2011, 01:32 PM   #5
olly01 is offline olly01
diyAudio Member
Join Date: Aug 2011
Hi all,

I came across this thread while looking for full schematics of the 540R v2 - in the hope that I could use it to understand and fix the cause of a problem I have with bass management (no cut-off on either FR/FL or SW, whatever the settings, and full pass-through of the fronts into the SW out).
The circuit diagram that sviru posted contains a partial view of the DSP board, which I believe to be the one I want. Would anyone know where I could find the full thing?

Oh, and by the way, I'd be very interested in the result of the caps' changes It would be silly not to try and improve the amp's sound while it's spread out and the iron's hot...
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Old 12th June 2015, 04:05 PM   #6
AlanFortune is offline AlanFortune
diyAudio Member
Join Date: May 2014
You'll find a service manual at Cambridge Audio Azur 540R Manual - AM/FM Audio Video Receiver - HiFi Engine You'll need to register (free).
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Old 14th August 2015, 10:25 AM   #7
Learnincurve is offline Learnincurve  Norway
diyAudio Member
Join Date: Aug 2004
Location: Stavanger
Sorry to revive an old thread, but I am interested in buying one of these and making improvements. As the thread founder isn't around, I was wondering if anyone can comment on his proposed mods and suggest where I should be careful or use a different approach.

I downloaded the schematics from the above link.

Much appreciated!
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Old 15th August 2015, 08:58 AM   #8
Bonsai is offline Bonsai  Europe
Account disabled at member's request
Join Date: Jul 2003
Location: Europe
Just leave your amplifier alone. Removing caps and changing opamps will not make it 'sing'. I think those are products engineered largely by Douglas Self, if not directly, then certainly with his guidelines applied. They are about as good as you can get.
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Old 17th August 2015, 09:09 AM   #9
Learnincurve is offline Learnincurve  Norway
diyAudio Member
Join Date: Aug 2004
Location: Stavanger
Looking a little closer at sviru's schematics the caps do look a little strange. If we take the FR channel as an example, C6/C7 seem to form a back to back pair, with a trimpot in between. I also fail to see any new, DC injection danger before the power amp input at C18 (power amp). I am far from expert, but surely this is overkill. replacement of all of these with a single MKP looks as if it would do the same job from a coupling perspective.
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