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Cambridge Audio Azur 640

the thin end of the wedge

Postby kcc123 » 08 Jan 2010 22:31

I think Panasonics are quite good sounding and so are the Elna Silmic and Nichicon Muse caps.
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Postby dokblue » 14 Jan 2010 19:55

Thanks kcc123!! Can I ask what exactly you used at C60,C62, and the other side of the mm and mc sections?
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Postby kcc123 » 15 Jan 2010 07:50

They were replaced with Blackgate NX HIQ 0.1uF/50V capacitors.
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Postby kcc123 » 16 Jan 2010 17:49

Since more than a year ago I have started modifying the 640P with many boutique parts and I have been very pleased with the results, though at a very high cost and the expense of my precious time and great efforts. I have a list of components for the modifications that I have already carried out:-

5 x Rubycon 25ZL 1000 caps (C42, C43, C47, C48, C55 -1000uF/25V)
4 x 25ZL 470 (C57, C65, C83, C84 -470uF/25V)
3 x 25ZA100 (C9, C10, C94 - 100uF/25V)
2 x bi-polar Blackgate NXHiQ 6.3V/47uF (C31, C64, original -16V/47uF)
2 x 35ZL1000 (C2, C4 -1000uF/35V)
4 x 35ZLH330 (C1, C3, C5, C6 - 50V/330uF)
1 x 25ZA10 (C11 – 10uF/25V)
2 x bi-polar Blackgate NXHiQ 6.3V/0.47uF capacitors configured as 1 Super E-Cap (C95 - 50V/1uF)
7x Schottky Barrier Rectifiers 11DQ10 (D1, D2, D3, D4, D5, D6, D7, D8, D13 IN4004 diodes)
4 x Blackgate NX 6.3V/220uF (C44, C56, C49, C61 - 220uF/6.3V)
4 x Blackgate NX HIQ 0.1uF/50V (C60, C68, C30, C62 - 100nF/63V)
2 x Blackgate N 6.3V/470uF (C88, C89 - 470uF/6.3V)
2 x Blackgate NX HIQ 22uF/6.3V (C90, C91 - 470uF/6.3V)
2 x Jensen paper in oil 0.012uF/400V (C76, C77 – 10nF/63V polyester caps)
2 x Polystyrene capacitors (C75, C35 -33pF/50V ceramic)
2 x silver mica (C92, C93 47pF/50V ceramic)
4 x 0.5W Audio Note Tantalum resistors (R50, R75, R25, R11 -100ohms)
2 x 0.5W Audio Note 2K2 (R26, R51)
2 x 0.5W Audio Note 47R (R5, R21)
2 x 0.5W Audio Note 3K9 (R14, R22 - 3.92K)
2 x 0.5W Shinkoh Tantalum resistors (R10, R13 - 75K)
2 x 0.5W Shinkoh 1K8 (R7, R24 - 1.87K)
2 x 0.5W Audio Note (R76, R78 - 47K)
2 x 0.5W Shinkoh (R15, R16 - 130 R)
2 x 0.5W Shinkoh (R17, R18 – 51 K: MM loading)
2 x 0.5W Shinkoh (R68, R85 – 560 K: MM loading)
2 x 0.5W Shinkoh (R15, R16- 130 ohms MC loading)
2 x 0.5W Audio Note (R60, R77- 470 ohms: MC loading)
2 x 0.5W Audio Note (R76, R78 - 47Kohms)
2 x 0.5W Shinkoh 9.1 Ohms - R82, R49 (leave R54, R71 empty - 18 Ohms) = +6dB output
2 x 0.5W Audio Note 47 R (R62, R79 - 91 Ohms) = +6dB output
4 x 0.5W Audio Note (R58, R60, R66, R77 - 470 R)
2 x 0.5W Audio Note (R59, R67 - 1.2k)
1 x 12V toroidal transformer
2 x LM4562, 1 x OPA 2111, 2 x OPA 637, (U3, U4, U5, U6 - 4 x NE5532 op-amps)
Blackgate NX HIQ 0.1uF/50V cap soldered across the pin 4 and pin 8 of each of the four op-amps.
Removed four brown caps (C14, C15, C28, C28) and by-passed the subsonic filter selector with 2 short solid silver wires connected between the legs.

It is only a guide line for those who are interested and any preferred components can be substituted as required.
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640P PCB with parts labelled

Postby Fatmangolf » 23 Jan 2010 13:49

This photo of the 640P PCB may be helpful. It has labels describing the caps and IC's that have been discussed in this forum.

12163

Not shown here are the 0.1uF power supply filter caps from pins 4 to 8 under each op amp IC.

I agree with an earlier posting about using capacitors from the Michicon Muse ranges. You can see the green ES bipolars in the signal decoupling and black KZ (and a few Rubicons) in the power supply filtering.
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Input decoupling capacitors are needed!

Postby Fatmangolf » 23 Jan 2010 14:28

ld wrote:PatOMalley is right, those caps block dc through the cartridge. If one were to short them out, I reckon there would be a few uA of dc in the cartridge coils. Can't advocate doing this, and I don't have a MC set up at this time to try, but that doesn't seem too bad to me. That would place about the same dc power as signal power in the coils, I reckon, FWIW.


In my 640P there is a DC voltage of a few millivolts on bases of the transistors which would mean a current through the cartridge if the decoupling capacitors were removed/shorted out. I suspect the resulting current through the coils would be bad for the cartridge and could affect the response of the transistors in the input gain stage. (The 540P didn't have an input decoupling capacitor which meant about 1mV across the cartridge coils and this voltage varied depending on the cartridge's internal resistance.)

Also if you want to experiment with the resistive loading on the cartridge, e.g trying less than 47k MM or 470R MC, the decoupling capacitor will ensure this does not affect the operation of the gain stage.
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Re: Input decoupling capacitors are needed!

Postby Guest » 23 Jan 2010 18:09

Fatmangolf wrote:
ld wrote:PatOMalley is right, those caps block dc through the cartridge. If one were to short them out, I reckon there would be a few uA of dc in the cartridge coils. Can't advocate doing this, and I don't have a MC set up at this time to try, but that doesn't seem too bad to me. That would place about the same dc power as signal power in the coils, I reckon, FWIW.


In my 640P there is a DC voltage of a few millivolts on bases of the transistors which would mean a current through the cartridge if the decoupling capacitors were removed/shorted out. I suspect the resulting current through the coils would be bad for the cartridge and could affect the response of the transistors in the input gain stage. (The 540P didn't have an input decoupling capacitor which meant about 1mV across the cartridge coils and this voltage varied depending on the cartridge's internal resistance.)

Also if you want to experiment with the resistive loading on the cartridge, e.g trying less than 47k MM or 470R MC, the decoupling capacitor will ensure this does not affect the operation of the gain stage.

Yes, it would suit someone brave enough to try it, but a few uA between friends might just be fine. There is potentially an upside, of course ! Could simulate it with a resistive load equivalent to the cartridge, and measure the current (v across resistor) first ?
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Postby PhP » 24 Jan 2010 19:47

kcc123 wrote:Since more than a year ago I have started modifying the 640P with many boutique parts and I have been very pleased with the results, though at a very high cost and the expense of my precious time and great efforts. I have a list of components for the modifications that I have already carried out:-

5 x Rubycon 25ZL 1000 caps (C42, C43, C47, C48, C55 -1000uF/25V)
4 x 25ZL 470 (C57, C65, C83, C84 -470uF/25V)
3 x 25ZA100 (C9, C10, C94 - 100uF/25V)
2 x bi-polar Blackgate NXHiQ 6.3V/47uF (C31, C64, original -16V/47uF)
2 x 35ZL1000 (C2, C4 -1000uF/35V)
4 x 35ZLH330 (C1, C3, C5, C6 - 50V/330uF)
1 x 25ZA10 (C11 – 10uF/25V)
2 x bi-polar Blackgate NXHiQ 6.3V/0.47uF capacitors configured as 1 Super E-Cap (C95 - 50V/1uF)
7x Schottky Barrier Rectifiers 11DQ10 (D1, D2, D3, D4, D5, D6, D7, D8, D13 IN4004 diodes)
4 x Blackgate NX 6.3V/220uF (C44, C56, C49, C61 - 220uF/6.3V)
4 x Blackgate NX HIQ 0.1uF/50V (C60, C68, C30, C62 - 100nF/63V)
2 x Blackgate N 6.3V/470uF (C88, C89 - 470uF/6.3V)
2 x Blackgate NX HIQ 22uF/6.3V (C90, C91 - 470uF/6.3V)
2 x Jensen paper in oil 0.012uF/400V (C76, C77 – 10nF/63V polyester caps)
2 x Polystyrene capacitors (C75, C35 -33pF/50V ceramic)
2 x silver mica (C92, C93 47pF/50V ceramic)
4 x 0.5W Audio Note Tantalum resistors (R50, R75, R25, R11 -100ohms)
2 x 0.5W Audio Note 2K2 (R26, R51)
2 x 0.5W Audio Note 47R (R5, R21)
2 x 0.5W Audio Note 3K9 (R14, R22 - 3.92K)
2 x 0.5W Shinkoh Tantalum resistors (R10, R13 - 75K)
2 x 0.5W Shinkoh 1K8 (R7, R24 - 1.87K)
2 x 0.5W Audio Note (R76, R78 - 47K)
2 x 0.5W Shinkoh (R15, R16 - 130 R)
2 x 0.5W Shinkoh (R17, R18 – 51 K: MM loading)
2 x 0.5W Shinkoh (R68, R85 – 560 K: MM loading)
2 x 0.5W Shinkoh (R15, R16- 130 ohms MC loading)
2 x 0.5W Audio Note (R60, R77- 470 ohms: MC loading)
2 x 0.5W Audio Note (R76, R78 - 47Kohms)
2 x 0.5W Shinkoh 9.1 Ohms - R82, R49 (leave R54, R71 empty - 18 Ohms) = +6dB output
2 x 0.5W Audio Note 47 R (R62, R79 - 91 Ohms) = +6dB output
4 x 0.5W Audio Note (R58, R60, R66, R77 - 470 R)
2 x 0.5W Audio Note (R59, R67 - 1.2k)
1 x 12V toroidal transformer
2 x LM4562, 1 x OPA 2111, 2 x OPA 637, (U3, U4, U5, U6 - 4 x NE5532 op-amps)
Blackgate NX HIQ 0.1uF/50V cap soldered across the pin 4 and pin 8 of each of the four op-amps.
Removed four brown caps (C14, C15, C28, C28) and by-passed the subsonic filter selector with 2 short solid silver wires connected between the legs.

It is only a guide line for those who are interested and any preferred components can be substituted as required.


Thank you very much KCC123 for the list I did asked you. Certainly very appreciated from all CA 640P owners! So far I have replaced all (except one small electrolytic) in the PS with Nichicon FC,FM and For Audio, and with one small 1uf 50v Elna Silmic II caps. Did also put Elna Silmic II in place of the caps before the 4 brown polypro (?) capacitors and in C94, C9 and C10 (same value but these Elna are way bigger caps...). Did put Nichicon For Audio in the MC (C42,43) and Nichicon Muse KZ (2.5 times bigger than the Nichicon For Audio) in the MM sections (C47,48). That is it for now until I receive my Blackgate nx and some resistors. Work in progress... Advise to all: take your time to use a lime to reduce the diameter of those big Nichicon and Elna caps, worth it if you don't want to get mad...the holes are small...
Can't comment on sound now since I have to put a HOMC cartridge to compare with what I had before on my tonearm. For now a little Sumiko Oyster MM cart sound good. Need more burn in time...and will see with the HOMC and a LOMC to compare with what I do remember with stock 640P.
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Postby stumpy57 » 26 Jan 2010 23:24

hello,
I took a look to the shematics of the 640P and I saw that there are two
gain stages, one with dif cascode transitors and the other with an AOP.
If I want to increase de gain by 10db on the MM input what do you mean is the better way ?
Increase the gain of the input stage or the AOP stage or both ?
What is the advantage to increase the gain of the cascode stage ?

Thanks

Alex
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Postby dokblue » 29 Jan 2010 01:20

Thanks SO much kc123 for the List and all the Great pi`s and help. I am just starting this upgrade now that I Filayy have most of the parts and can`t wait to hear the difference!!
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Postby blue lander » 09 Feb 2010 22:30

Sorry if this has been covered before, but if I wanted to increase the gain on the MC stage to get a little more out of my Denon dl-103, which resistors would I replace and what would be a good replacement value?
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Postby kcc123 » 10 Feb 2010 00:33

You can reduce the resistor (R71) value from 18 Ohms to 12 Ohms with 3dB gain or from 18 Ohms to 9 Ohms with 6dB gain. Alternatively you can just solder one 33 Ohms or 18 Ohms resistor respectively in the unused position of R49. I use my 103R with 6 dB gain.
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Postby stumpy57 » 10 Feb 2010 07:42

Hello,

Why to only change the gain in the OP stage?
Changing the gain in the diff stage will be not better ?
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Postby audio_builder » 24 Feb 2010 06:09

OP-AMPs go bye-bye
http://i296.photobucket.com/albums/mm17 ... -OPAMP.jpg

There they are
http://i296.photobucket.com/albums/mm17 ... Bottom.jpg

Don’t they look cute?

TI-5532 out, TI-1611 in
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Postby Garven » 24 Feb 2010 16:00

I have a question regarding my 640P. Last fall when I was running an AT150MLX through it, I removed the 220pF capacitors from the MM input. I'm not very experienced or comfortable with circuit board work (my soldering iron experience has been basically doing up cables, etc.). I read the various mods done in this thread and decided to see what I could do with my 640, but I was unable to get the circuit board out of the bottom of the case, so I decided to get wreckless and simply rocked the 220pFs carefully until they snapped off their leads cleanly at the board level. This worked perfectly and the sound of the 150MLX was significantly better through the 640.

Now I'm running an Ortofon 2M Bronze through it. The 2M isn't nearly as bright as the 150. It's not dull exactly, but in testing now that I've got about 70 hours on it, I do notice a slight dip around 9-10k and slight rise in the upper highs. I'm wondering if having some capacitance back would even it out slightly. My cabling (internal TT plus interconnect) gives me about 100pF and I see Ortofon recommends 150-300 pF load capacitance.

I'm wondering if I could simply pick up some 100-200pF capacitors and either create some kind of an inline plug for each channel with the capacitor soldered between the + and - connections, or else create a short set of interconnects with the capacitors inside the phono plugs on one end. If so, what type of capacitors would be the best choice?

In checking the Cartridge/Amp Loading/Resonance calculator here I see that with my current setup of ~100pF & 630mH inductance, my optimum loading is way up around 79.4kOhm. Increasing the capacitance to 280pF by adding a 180pF capacitor would result in an optimum loading of 47.4kohm, so adding capacitance would seem to be the right path.

Alternatively, if adding capacitance is not the way to go, is there any way of increasing the loading to 79kOhm using some sort of external additions. Back with my 150MLX, I had some success with adding parallel resistance by soldering resistors into RCA plugs and inserting them into Y-plugs at the 640 inputs. Obviously here I need to increase the loading not decrease it, so I thought about resistance in series, but I doubt this would work. Would it not simply block the signal from getting through at all if I were to place 32kOhms of resistance between the positive lead coming into a phono plug and the post? Any thoughts?
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