Question about Cambridge Audio Azur 640A Amplifier

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Using a tube pre amp with my CA Azur 640A?

Can I use a tube pre amp with my 640A? If so, how do I configure? Connect my sources (CD & Squeezebox) to the inputs of the preamp - then connect the preamp to the 640A? Does it matter which input on the 640 I use? And, am I "undoing" the sound of the tube preamp by having it run through the 640A? Many thanks...

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Re: Using a tube pre amp with my CA Azur 640A?

There are many answers to your questions but Ill have a go with the basics...
Audio connections should be matched.... its called Frequency impedance,.... to get a signal along wires or cables (or Fibre) the Impedance of the cables and wires must be matched to the device they are connected to transfer the signal along the cables without distortion...

Manufacturers provide many sockets on the input side of amplifiers and preamplifiers to allow the consumer to connect various devices of different impedance.

They label these inputs like CD, or Tuner, or PHONO etc etc,

That means if you have a CD player it must be plugged into the CD input socket then the impedance will be correct and the sound will transfer along the CD cables correctly, without distortion..same with the Phono input etc...
You will find on the sound output to the speakers terminals are also labelled 4-6ohm, or 8-10ohm, these are the impedance expected for the coil ratings of the speakers them selves and its important to get the correct speakers to the correct out put terminals...

In your case all you have to do is follow these simple rules and all will be say you have a squeeze box well there probably isnt a port labelled squeeze box so you need to experiment and try out each input port for the squeeze box to see what input gives you the correct sound output...Watch the Phono inputs as these are very sensative to input sound levels and must be treated very carefully as they have a double stage of sound amplification and as such you need to have the volume right down when connecting up the Phono inputs then increase the volume carefully after the cable connections are completed.

If you follow these rules then all will be well,,,,there is no difference if the Pre amp or Power amp is valve or transistor or FET or has IC outputs to the speaker the same impedance rules apply..just treat it as a box with input and output terminals and all the impedance will be taken care of for you...if you read the lables...

You need to connect you signal source to the Preamp inputs the out put from the Preamp connects to the power amp input then the power amp output goes to the speakers. this is a basic configuration for sound systems, there are other variations but are outside this discussion.

Cheers From YUBEUT

Posted on Nov 16, 2007

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Running four S70 Siroccos off the amp, everytime volume gets halfway the protection is cutting in with protection light flashing three times? When reducing down to two speakers amp cuts out three quarters...

You are overloading your amp. IMO 640A cannot handle heavy loads.

Better change the speaker combo and connect something that puts right load on the 640A. Else, get a meaty amp from CA.

Mar 04, 2011 | Cambridge Audio Azur 640A Amplifier

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Of course, just run an audio RCA pair out from the Pre Out to your next amp and any input. All control for volume, tone, etc will remain with the 640A.

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I have a Cambridge Azur 640A amp, every time I turn the volume up to over 12 oclock the amp shuts down. Can this be changed? I presume this is a safety mode on the amp. Can you help?

Yes, you are right. That's a protection feature to prevent burnouts. Typically it appears when your speakers are sucking up a lot of load from the amp. Please check your speaker impedance and the amps' output impedance and ensure the wiring are properly done. Some amps are soo sensitive that they may cut-off after certain level due to overload.

Jan 06, 2011 | Cambridge Audio Azur 640A Amplifier

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Hi, I have only used my CA 740C a few times and the fuse blows, I placed another fuse in and that blew as well. Haven't a clue why this might be happening can you help please? Thanks

Looks like a electrical problem. Ensure your plug's earth is properly connected to the building earth. Amps like 640A uses sensitive circuits and the fuse will definitely blow, when there are issues, spikes or returns in the power supply.

Try shifting the amp to a different wall plug with some proper ground earth, and check it. If the fuse still blows, then the power cable in the amp may have some problems.

Hope this helps :-)

Jan 04, 2011 | Cambridge Audio Azur 640A Amplifier

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My CA Azur 640A v2 just cannot get out from standby because of protection circuit. the red light blinks showing that DC was measured at terminals, no matter if speaker cables are pluged in or not. In...

Most 640As suffer from this sensitive issue. It is not a fault, but a protection mechanism that is too sensitive. In some cases, it could be due to the open ground earth issue or Left & Neutral reversed at the wall plug. Check your wall plug's connection and if they are perfect, then it could be because of a electrical issue inside the amp. In that case, get the technical support from CA to fix this.

Jan 03, 2011 | Cambridge Audio Azur 640A Amplifier

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Cambridge azur amp 640a working brill till yesterday !! now protection light !!!! turned it off numerous time etc plenty of venterlation carnt get it to work

Looks like the fuse blown.. or the classic symptom of electrical fault inside the amp. 640A uses a sensitive protection circuit often ends up in this irritating situation. Normally, there is nothing much you can do, but just check your wall plug connection for Open Ground or Left & Neutral reversed issues. If the wall plug is free of error, then you should better contact CA technical support.

Dec 08, 2010 | Cambridge Audio Azur 640A Amplifier

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Hello, I am trying to plug my Mixer into my amp but only one speaker has sound..I am using a Rane ttm57sl mixer with technics turntables & cambridge audio azur 640a amp...I've gone from the Aux out on...

Why don't you try using the main outputs (the 2 XLR connectors). With 2 cables connect these two (left - right) outputs at your amplifier's aux in. In that case take care that the "output level" of the mixer works like master volume controlfor the signal that the mixer sends to the amplifier.

In case of a problem or clarification, don't hesitate to post.

Thanks and regards
Please kindly rate this solution

Feb 04, 2010 | Cambridge Audio Azur 640A Amplifier

1 Answer

Problem with azur 640a amp

protection mode activated to protect your amp from a problem.
please disconnect all your speaker from the amp and check if it is fine start to connect your speaker one by one until you find the bad one which make the problem-change its cable first and then speaker itself.if the problem still you will have a problem in amp.

Jul 08, 2008 | Cambridge Audio Azur 640A Amplifier

1 Answer

Protection snaps into action intermittently

I don't think the pin or third prong on your power cord would be the problem, but I would make sure that all of your speaker wires and connections going to your amp are not shorting out against eachother.

I hope this helps you out.

Apr 01, 2008 | Cambridge Audio Azur 640A Amplifier

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