0.25W (1/4W) will do fine. There's very little current to deal with, it's pre-amp level.
Updating my Azur 640A v1, here are the starting pictures. I am replacing most electrolytics Non-polar with Nichicon Muse ES (the emerald green) and other MUSE.
The 8 main power caps are getting upgraded to 3,300 uF each from 2,200 uF. Build quality is not as bad as I thought, soldering is OK, but the rest of the unit seems pretty good. I am not sure about the quality of the Acon capacitors as I am not familiar with them.
Thought about replacing the op amps with OPA2134, but I am thinking of leaving them alone since I like the sound of the TI NE5532 & 34 op amps (bass especially) that are in it.
This is a really fine sounding integrated.
Some pics:
The 8 main power caps are getting upgraded to 3,300 uF each from 2,200 uF. Build quality is not as bad as I thought, soldering is OK, but the rest of the unit seems pretty good. I am not sure about the quality of the Acon capacitors as I am not familiar with them.
Thought about replacing the op amps with OPA2134, but I am thinking of leaving them alone since I like the sound of the TI NE5532 & 34 op amps (bass especially) that are in it.
This is a really fine sounding integrated.
Some pics:
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They still haven't learned that that heatsink design is useless... 65W into 8 ohms with that? I don't think so. They used those on the A500 and i've seen plenty of them blown up due to overheating. It doesn't help that those SAP devices are fragile.
Good luck if you ever blow them - the whole SAP range is now obsolete.
Good luck if you ever blow them - the whole SAP range is now obsolete.
What I'd do if I was upgrading it, would be to get a suitably sized REAL aluminium extrusion heatsink, and some good, thick L-angle. Bolt the L-angle to the extrusion with heatsink paste in between, and mount the SAP's to it.
Better still if you can avoid the L-angle altogether, though the pins on the SAP's would probably not be long enough unless you installed new ones, or lengthened the old ones slightly with some solid core wire.
Better still if you can avoid the L-angle altogether, though the pins on the SAP's would probably not be long enough unless you installed new ones, or lengthened the old ones slightly with some solid core wire.
V2 of this amp has a bigger toroidal and a better heat sink. They both sound good, to my ears the V1 sounding just a tad brighter that V2. Out of the box, these amps sound really nice and that is why I am not modding. It is my understanding that Cambrige tested the OPA2134 op amp and found the NE5532 better performing. So I am not implanting those even though I have them.
As far as sound, I will not know until the new caps have burned in, but if I get what I had plus 1/2 a percent more, I will be happy.
The amp case is well put together and takes some skill to take apart.
As far as sound, I will not know until the new caps have burned in, but if I get what I had plus 1/2 a percent more, I will be happy.
The amp case is well put together and takes some skill to take apart.
The NE5532 used in the Cambridge are TI units. I too thought that the TI Burr-Browne OPA2134 would be an upgrade, but digging comments all over the place seems to lead me to believe that there is some merit to using the TI NE5532 (transparency, bass response, listenability). You probably gain some detail and top end air with the OPA2134.
If the unit were easier to take apart, I would sock it the chips and roll them, but those star screws are not easy to take out.
Mouser has the OPA2134 at $2.67, and the NE5532 at $1.00.
Have you done any A / B comparisons?
Here are some pictures of the completed recap. I used Nichicon FW, Nichicon MUSE ES, plus a few others.
The verdict on improvement is out until the 200 hour burn-in period is completed--at least I did not blow up anything.
The main power cap reserve was increased from 17,600 uF to 26,400 uF, should have enough power for dynamics. Took the opportunity to clean the boards.
Had a really nice solid aluminum heat sink to add, but could not fit it in the case.
The verdict on improvement is out until the 200 hour burn-in period is completed--at least I did not blow up anything.
The main power cap reserve was increased from 17,600 uF to 26,400 uF, should have enough power for dynamics. Took the opportunity to clean the boards.
Had a really nice solid aluminum heat sink to add, but could not fit it in the case.
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OK, I installed it. I ordered it plus a socket so I can roll the op amps. My next one is the AD8599 (SD mount) on an adapter, I think will be the top dog.
Here is a pic of the OPA2134 in the socket. Sounds quite nice, a bit more forward than the NE5532, I think I like it better.
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The AD8599 op amp arrived today. I immediately installed it. I did perform before and after evaluations. The AD8599 is a few levels above the OPA2134 to my ears. I do not have the audiophile lingo to describe it, but the Azur was not the same afterwards, it was much improved. The bass becomes less bloated and more impacting, the mids come forward in a very nice way, and the highs clean up ever so nicely. Take my word, this op amp is worth a try. Is not that the OPA2134 is that much lesser, you would be very happy with it until you hear the AD8599. It is a great op amp.
As you can see, it only comes in surface mount and you need to install it in an adapter. If I were not using the 8 pin DIP socket, it would probably not clear the square capacitor next to it.
As you can see, it only comes in surface mount and you need to install it in an adapter. If I were not using the 8 pin DIP socket, it would probably not clear the square capacitor next to it.
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Poor Man's Cooling Improvements for the 640A V1
This amp has a sub par part sheet metal heat sink and heat can be an issue if driving the amp hard. Here's a couple of cheap tricks to help its cooling.
1. Raise the unit by adding some feet.
2. Route the wires to the side of the heat sink rather than above it. See before and after photo.
This amp has a sub par part sheet metal heat sink and heat can be an issue if driving the amp hard. Here's a couple of cheap tricks to help its cooling.
1. Raise the unit by adding some feet.
2. Route the wires to the side of the heat sink rather than above it. See before and after photo.
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Thanks for pointing that out skidude, I will go back in and install the OPA2134 there and in place of the two tone control NE5532 op amps. So far so good.
I placed the OPA2134 in the audio path under the copper shield at the beginning of the preamp. Also proceeded to replace the 2.2 nF bypass capacitors at the entry into the power amp from the preamp with 1 uF stacked film cap (these bypass the 10 uF non-polars). I also installed an OPA2134 in the pre-out circuit to replace the NE5532 there.
It was a total failure. The sound became restrained and very sibilant, reminded me of Dolby C on a tape. I could not stand it.
Had to revert back to the NE5532 into the entry of the preamp and then the AD8599 at the output of the preamp. The other two NE5532 work the tone control and are fine and can be bypassed but do not affect the sound negatively. Also, since it is a lot of work to do this, the 2.2 nF went back in just in case that had anything to do with it.
A learning experience. Sometimes it is better to stop when you are ahead. Hopes this helps someone.
It was a total failure. The sound became restrained and very sibilant, reminded me of Dolby C on a tape. I could not stand it.
Had to revert back to the NE5532 into the entry of the preamp and then the AD8599 at the output of the preamp. The other two NE5532 work the tone control and are fine and can be bypassed but do not affect the sound negatively. Also, since it is a lot of work to do this, the 2.2 nF went back in just in case that had anything to do with it.
A learning experience. Sometimes it is better to stop when you are ahead. Hopes this helps someone.
Sorry to hear it didn't go well. The op amp you used is unity gain stable so should have been ok as a buffer stage. The NE5532 is bipolar transistor compared with the OPA2134 which is FET input. My guess is the op amp was oscillating (unstable). The circuit must be quite sensitive as CA used a copper shield can.
Hello dear friends,
Talking about 640A (V2) modding , I've replaced the soundwell 20K pot with an ALPS RK168 10K log (without 10k series resistors) .
When I turn the volume pot to the minimum position in the speakers If I listen closely , I hear a weak signal of music.
Is that a normal thing ?
This can be a result of not using series resistors 10K in order to obtain the same value as the old pot (20k) ?
Or some pots just have the minimul position phisically not equal with 'mute' function (?)
Any sugestion will be appreciated
By the way , I am wishing you a happy new year
Talking about 640A (V2) modding , I've replaced the soundwell 20K pot with an ALPS RK168 10K log (without 10k series resistors) .
When I turn the volume pot to the minimum position in the speakers If I listen closely , I hear a weak signal of music.
Is that a normal thing ?
This can be a result of not using series resistors 10K in order to obtain the same value as the old pot (20k) ?
Or some pots just have the minimul position phisically not equal with 'mute' function (?)
Any sugestion will be appreciated
By the way , I am wishing you a happy new year