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i2k92 27th March 2005 08:30 PM

Modding Azur 640A
 
Guyz,

I've just opened the hood of my Cambridge Audio Azur 640A and find out that it only has 4400 uF per power supply rail (consist of 2 x 2200 uF/50v in parallel, means for all channel it has 8 pieces of 2200 uF). From what I've read, it is not at all sufficient for 640A's 65 watt power. No wonder if the bass is a bit weak. If I remember correctly the "rule of thumb", my 640a need at least around 6500 uF.

Question :

What will be the best way to upgrade this : for each rail :replace with 2 x 3300 uF / 4700 uF, or 1 x 6700 uF, or even jump to 10000 uF.

What will be the sonic difference if I arrange 2 caps in parallel than using 1 big cap with approximately same total value ?

Is it good to use BC components (type 037/056/057/154/114), caps for this upgrade ? This is the only brand I can get easily in France for almost all range of capacity & voltage with reasonable price. I lived in Indonesia before, and it was easier and CHEAPER to buy audio grade caps.....(and everything else off course, nothing is cheap around here)

Does somebody knows if Farnell France receiving oder in small quantity for poor people like us ? I just found some interesting Panasonic and Rifa on their catalog.

I'm new to this DIY audio stuff, so help me please....

Gasho 27th March 2005 08:58 PM

I just have that amp on modification. When I take a good look on topology of whole amp , I realize that there is much to be modified. PS of output stage is quite miniature. That is not dual mono design , so all caps(4per rail) are in paralel so you have about 8800uF per rail , for both channels. The mayor problem is poor quality of these caps (and all others on PCB) so I will replace them with Panasonis 3300uF ultra low ESR , high current type. Next I will replace all diodes i PS with Schottky types. Than i will clear the signal path , and i will use higher quality OP-s for gain stage and tone controls , bypass all poor coupling caps and input buffer stage. Orginal OP-s are NE5532 in all positions. Decoupling caps are some poor bipolar electrolitics. It is the miracle that this amp have a little listenable sound. :eek:

breez 27th March 2005 09:11 PM

Quote:

Originally posted by Gasho
It is the miracle that this amp have a little listenable sound. :eek:
In the world of overkill components @ diyaudio, people might expect too much influence from components. Maybe the implementation matters even more compared to components?

Gasho 27th March 2005 09:16 PM

No way! A poor component can do no good for signal:dead:

Jan Dupont 28th March 2005 05:39 AM

Gasho:
You are right.... A poor component can do no good for the signal!
However..... How big improvement are guaranteed using million $ caps and opamps in a bad circuit (not saying that the circuit in the Cambridge is bad, - just a standard Taiwanese circuit):D


i2k92:
Cambridge (like other similar brands) does have a big lack in the quality of components used, however you will come a long way by increasing the PSU to 2x10.000uF and by shortening (if possible) or replace the DC-blocking caps in the signal path with bigger ones.....
I have notised that in many amps like Cambridge there are used caps in the nF range as bypass caps.... Replace these with 1-4.2 uF film caps (Evox, Rifa or Wima etc.) and you wont believe your ears ;)

My old modified QUAD 34 preamp had a frq. range 10-25.000 Hz or so before the mod.... Now it is dead flat from 2-300.000 Hz just by shortening/replacing caps in the signal path etc. ;)

i2k92 28th March 2005 07:33 AM

Quote:

Originally posted by Gasho
That is not dual mono design , so all caps(4per rail) are in paralel so you have about 8800uF per rail , for both channels. Orginal OP-s are NE5532 in all positions. Decoupling caps are some poor bipolar electrolitics.

Thanks for the correction and mod ideas.

I looking forward to replace the caps with 1 x 12000 uF per rail, as I'm not sure if I will have enough space for 8 x 3300 uF. I'm thinking about Panasonic GBA or BC component 154. What type of Panasonic you will use ?

About the opamps, are you sure the it uses 5535 on the gain stage ? I think it uses 5534.

And what do you think about the potentiometers ? I think they're bit nasty. I'm going to replace the vol and balance control. I will leave the tone control alone, I never use them anyway.

Sorry for asking too much....:clown:

Gasho 28th March 2005 08:29 AM

Quote:

Originally posted by i2k92



Thanks for the correction and mod ideas.

I looking forward to replace the caps with 1 x 12000 uF per rail, as I'm not sure if I will have enough space for 8 x 3300 uF. I'm thinking about Panasonic GBA or BC component 154. What type of Panasonic you will use ?

About the opamps, are you sure the it uses 5535 on the gain stage ? I think it uses 5534.

And what do you think about the potentiometers ? I think they're bit nasty. I'm going to replace the vol and balance control. I will leave the tone control alone, I never use them anyway.

Sorry for asking too much....:clown:


I Was talking about NE 5532 which is double OP , and I am pretty shure that all OP-s are the same:cool:

Panasonic FC series.

I think it is too much problems around changes of pots. There is a space problem and holes on PCB are done for only this pot.
If you want to change this one with better like Alps "Blue velvet" motorised , you probably need to drill or cut something:dead:

i2k92 28th March 2005 11:46 AM

2 Attachment(s)
Quote:

Originally posted by ACD
Cambridge (like other similar brands) does have a big lack in the quality of components used, however you will come a long way by increasing the PSU to 2x10.000uF and by shortening (if possible) or replace the DC-blocking caps in the signal path with bigger ones.....
I have notised that in many amps like Cambridge there are used caps in the nF range as bypass caps.... Replace these with 1-4.2 uF film caps (Evox, Rifa or Wima etc.) and you wont believe your ears ;)
[/B]
Thanks,

Can you confirm this statement that I got over the net today :

The capacitors in the power supply has its own inductance. An engineer might decide to build a power supply with a single 50,000 micro farad capacitor. However, it is more likely that using five 10,000 micro farad capacitors will have less inductance and give faster current response.

How about replace the DC blocking caps with Audyn 2.2 uF MKP Plus Metallized Foil ? I think that the price is reasonable enough.

BTW, I attached the 640A schema in case somebody interested to it and perhaps will give me some more input.

thanks...

Jan Dupont 28th March 2005 02:38 PM

i2k92:
About capacitors in the PSU there are both inductance and resistance to worry about ;)
I would personally prefer the solution with 5x10.000uF and with a small film cap in parallel with each of the beer cans ;)

The schematic shows that you only got DC blocking caps in the input to the power section...

Otherwise the schematic shows the use of the good Sanken output devices with build-in diode.... I'm surpriced :confused:

i2k92 8th April 2005 07:57 PM

Thanks again Jan...
Do you think I will get some improvement if I replace those NE5534 to let say AD825 or OPA627 ??


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