Modding Azur 640A

"High fidelity means the possibility to listen to the playback of people’s applause and not to confuse them with rain’s noise falling over a zinc roof ..... Nor to confuse the noise of dissolving waves when touches the beach sand, thinking you have eggs frying in hot oil there"

Funny and true. Fortunately my system meets these requirements! (It didnt when it was standard though. LOL!)

I have the 340A service manual with schematics and B.O.M. if your interested?
 
Uhh what, the 640A is basically a Gainclone!! I guess Cambridge are cheaping out, even though most of their previous amps were SAP15 based. I don't know how they can charge what they charge considering!

Cambridge Audio's quality has gone very much downhill. I recently serviced a Cambridge Audio A5 amplifier - the internal construction was abysmal. The PCB's had all been hand soldered, there was flux and solder spatters everywhere. Cheap capacitors were used throughout and the potentiometer were very very cheap and nasty.

The fault turned out to be a poor PCB that had led to the right channel input signal being shorted to ground. Despite thoroughly cleaning the PCB I was left with no choice but to cut the track that was shorted to ground and replace it with a wire.

Destroyer X, you are most likely thinking of the "Class XD" based amplifier - the Azur 840A. The idea is basically to shift the crossover point away from 0V. Personally, I don't see what difference this would make at all.
 
My amp looks nothing like you described. All solder joints are neat and clean. Only criticism would be the use of very cheap caps but hey, this is a 200 quid amp. Your right about its simmilarities to the GC. In my opinion this is no bad thing. Ive read of DIY GC's sounding totally amazing.....
 
Thank you Jaycee..... i am in contact with Rabbitz..he has one

and he was evaluating it... soon i will have a result.

Mikesnowdown.... make me calm down.... i just cannot wait to see the schematic... send it to me, please.

Yes..of course... can be another Marketing thing... having nothing very special into the circuit...also may not sound special...but i have to listen to be sure.

thank you folks,

regards,

Carlos
 
Don't get too excited Carlos as mikesnowdon's is the 340A SE (chip based) and not the 840A (Class XD) that you are trying to find details on.

The 840A V2 I tried was faulty and I sent it back to the distributor so I will never know what it was supposed to be like.
 
Yes..... thank you Mikesnowdown... was a surprise to see LM3866 inside

Ahahahaha.... i have conclude those days that to 35 watts output, nothing can be better idea than to use those chips... clapps does not sounds as rain over the zinc roof when using those amplifiers.

I am happy i have not made wrong conclusion about.

Yes.... i could not know the "system" used to avoid crossover distortion.... one day i will know.

thank you folks.

regards,

Carlos
 
My post picture is just for rest and relax for yuo're all problem with CA 340A/640A. Actually I'am already sold many unit about cambridge audio ( 340,540,640 ) so far so good! and think to mod power supply ( Capacitor section ) unit is good way! ;)
 

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Yes Mikesnowdown... soon i will receive more samples of this chip

also some nice operational amplifiers...and for sure i will build one to stay.

A friend called Sean is shipping some nice and fast Operational Amplifiers and Dudainc is shipping breadboard and LM3866... I have never had problems to obtain those parts.... when we have good friends, in special if they leave outside Brasil, to have those parts are not a big problem... we have only to let them know we need those things and fast they ship for me...i am lucky and not proud..not problems to accept gifts.

I said 30 to 35 watts because into this range of power it distorts almost nothing... very good sound when you accept low power.

For sure it can go to 55 watts...or 50... or 45...or 40...but distortion and audio quality goes down.

I had some of them, and i have perceived that... this is not observing data sheet...was something i found listening... 30 watts is perfect for this chip.

I have some units tested (chips) into Youtube... video samples of my "barbecue of chips" when i have destroyed many (destroyer X)

Thank you once again Mike... was kind from you.... a lot pleasant for me my new friend.

Carlos
 
This may be of interest:

I had Greg B, designer of the famous SKA audio modules take a look at the CA 340 circuit. I was asking about intalling one of his LDR volume control and 'SK Pre' preamp modules in the 340. I had an issue about the gain being too high. Heres something he advised....

The easy solution here is not to reduce the gain in the buffer stage, but to reduce it in the power amplifier. This is easily done by changing R53, R55 ( 270K) for 24K.
This has the added advantage of reducing noise as higher signal levels are maintained through the volume / tone controls and into the main amp. Also there is 6dB extra feedback around the power amp chips for lower loop distortion and a 6dB PSRR improvement on their weaker -Vs supply. Phase margin is worse by only 7o, insignificant.
 
mikesnowdon said:


Really? So what op-amp is the best then?
Some examples:
AD797 - the best I've heard, very clean and neutral, maybe a bit too soft, only comes as single amp so you need two on an adapter, needs some attention to sound at it's best, not a drop in replacement
AD8599 - clean and warm and almost neutral, slightly recessed mids and laid back
LM4562=LME49620 - bright and clean, also slightly recessed mid
AD8066 - fast with bright treble and and a kick *** bass, slightly grainy and harsh, lively and fun
AD8620 - very neutral but grainy and harsh
OPA2107 - very warm and sweet but a bit grainy and lacks details
AD825 - forward mid, detailed, clean, involving, only single - requires two on an adapter

OPA637 or OPA627, and LT1364, are often claimed to be amongst the best, but I haven't heard them.