Get started and post some pics soon!
Take you time though. One thing I have learnt is not to rush and make sure you iron is hot and the tip is clean! Be careful of the CA PCB when de-soldering, the pads lift very easily. Dont apply pressure with the iron, just touch the component with a wet tip, enough to transfer heat.
Good luck!
Take you time though. One thing I have learnt is not to rush and make sure you iron is hot and the tip is clean! Be careful of the CA PCB when de-soldering, the pads lift very easily. Dont apply pressure with the iron, just touch the component with a wet tip, enough to transfer heat.
Good luck!
Naked caps!!!!
Just about using naked caps:
Be careful that the 2 caps don't touch, this should be fine as the spacing leaves about 1.5mm between them but just incase, be careful. Also when fitting the MUR860 you will have to be sure the heatsink dosent touch the cap body as they are quite close. Check everything thoroughly around those caps before firing up the amp.
Mike
Just about using naked caps:
Be careful that the 2 caps don't touch, this should be fine as the spacing leaves about 1.5mm between them but just incase, be careful. Also when fitting the MUR860 you will have to be sure the heatsink dosent touch the cap body as they are quite close. Check everything thoroughly around those caps before firing up the amp.
Mike
Hi Stream,
In your post showing the capacitors you have removed, I have some concerns. C58, and C72 (plus the other channel) are there to prevent oscillation. They do not pass audio and are required to remain in circuit. Leaving them out may cause your amplifier to oscillate, leading to it's destruction.
That is one reason I become nervous when people who don't understand how an amplifier works start removing or changing things.
Hi Mike,
Hi Andrew,
-Chris
In your post showing the capacitors you have removed, I have some concerns. C58, and C72 (plus the other channel) are there to prevent oscillation. They do not pass audio and are required to remain in circuit. Leaving them out may cause your amplifier to oscillate, leading to it's destruction.
That is one reason I become nervous when people who don't understand how an amplifier works start removing or changing things.
Hi Mike,
I've never seen markings under the label, ever. Now you know.
Hi Andrew,
That riveting looks to be quite common to me. I wouldn't be too concerned as to who the exact manufacturer is, and the supplier may have changed through the production.
-Chris
Hi Mike,
Post # 539 is the one I'm concerned about. If you see a 10 pF capacitor, it is very unlikely meant to pass audio signals. Whatever you do in cases like this, make sure that some form of 10 pF capacitor (or whatever the original value was) remains in these locations at least to start.
So, watch for small value capacitors, normally less than 0.001 uF, and make sure you don't remove them. In fact, when replacing output transistors to a different number, you may need to figure out a new value for these. Even when replacing "STK" type thick film power amp modules, you may have to change these values. That's even with the same part numbers!
-Chris
Post # 539 is the one I'm concerned about. If you see a 10 pF capacitor, it is very unlikely meant to pass audio signals. Whatever you do in cases like this, make sure that some form of 10 pF capacitor (or whatever the original value was) remains in these locations at least to start.
So, watch for small value capacitors, normally less than 0.001 uF, and make sure you don't remove them. In fact, when replacing output transistors to a different number, you may need to figure out a new value for these. Even when replacing "STK" type thick film power amp modules, you may have to change these values. That's even with the same part numbers!
-Chris
Hi Stream,
To change the capacitor values, there is some math to do and data sheets to read. That is your starting point because board layout will change things. To make sure everything is okay, you need to use a signal generator and an oscilloscope - minimum! A THD measurement would be a very good idea also. Often, trouble will be supersonic and oscillation can occur almost as high as 1 MHz. In fact, I've seen oscillation at several MHz.
-Chris
What are the original values? You have 10 pF marked on the diagrams. I would make sure the same values remain in those positions.
To change the capacitor values, there is some math to do and data sheets to read. That is your starting point because board layout will change things. To make sure everything is okay, you need to use a signal generator and an oscilloscope - minimum! A THD measurement would be a very good idea also. Often, trouble will be supersonic and oscillation can occur almost as high as 1 MHz. In fact, I've seen oscillation at several MHz.
-Chris
Anatech,
I Have CA Azure 340A. NOT SE version.
So my amp HASN'T that capacitors! But SE (Mike has got SE) version has it. I think SE version is upgraded ( factory tweak ) version of 340, and SE has front-panel Input as a bonus
Thats why i want to try adding these little caps, but i didn't know how to calculate optimal nominal. Datasheet says it's optional.
BTW, if amp has oscillation on 1Mhz, how it affects on 20-20kHz range?
I Have CA Azure 340A. NOT SE version.
So my amp HASN'T that capacitors! But SE (Mike has got SE) version has it. I think SE version is upgraded ( factory tweak
) version of 340, and SE has front-panel Input as a bonus Thats why i want to try adding these little caps, but i didn't know how to calculate optimal nominal. Datasheet says it's optional.
BTW, if amp has oscillation on 1Mhz, how it affects on 20-20kHz range?
Hi Stream,
-Chris
Scary!
My approach would be to feed your amp from a generator and sweep it up while monitoring with an oscilloscope. There is no such thing as being too safe with these things.
The HF oscillation tends to mess with the bias and heat up the output stage. It can often be heard as a 50 Hz (in your area) hum or buzz. It can also cause increased distortion (not always) that can not be explained.
-Chris
Hi Peeps,
My 2 cents worth:
CA wouldn't put into production an oscillating amp, for sure. They have competent design engineers I think, look at the awards and reviews the Azur products get.
In a much earlier post from Stream we saw a close up of the LM3886 showing 2 small Ceramics, one bypassing the NFB resistor and another from the + rail to - just before the chip. These were not shown in the 340A schematics we were looking at so there was probably a revision and the service manual wasnt updated. We see the same thing on the opamp (Input buffer), again the photos of Streams 340A Show these caps yet they are missing from the 340A Manual.
It was only when we started looking at the 340A SE Schematics that we noticed this.
So basically Stream,
You dont have to worry about it, you amp has those caps already.
Mike.
My 2 cents worth:
CA wouldn't put into production an oscillating amp, for sure. They have competent design engineers I think, look at the awards and reviews the Azur products get.
In a much earlier post from Stream we saw a close up of the LM3886 showing 2 small Ceramics, one bypassing the NFB resistor and another from the + rail to - just before the chip. These were not shown in the 340A schematics we were looking at so there was probably a revision and the service manual wasnt updated. We see the same thing on the opamp (Input buffer), again the photos of Streams 340A Show these caps yet they are missing from the 340A Manual.
It was only when we started looking at the 340A SE Schematics that we noticed this.
So basically Stream,
You dont have to worry about it, you amp has those caps already.
Mike.
Stream said:Anatech,
I Have CA Azure 340A. NOT SE version.
So my amp HASN'T that capacitors! But SE (Mike has got SE) version has it. I think SE version is upgraded ( factory tweak
Thats why i want to try adding these little caps, but i didn't know how to calculate optimal nominal. Datasheet says it's optional.
BTW, if amp has oscillation on 1Mhz, how it affects on 20-20kHz range?
Hey man
There are some discrepancies in the schematics. We found similar things in the 640C thread. Dont worry about it, just check the amp iteslf.
The differences are:
340A 6800uf PSU caps - 340A SE 10'000uf.
SE has additional buffer for iPod plus relay to switch it in when the the front panel input is used. Thats it, these are the only differences between our amps.
(Also there are a couple of Ceramics by the binding posts, they go from speaker - to power supply GND. They are not shown in the 340A schematics but your amp has them, I checked the pics).
Mike
Hi Mike,
Look, I'm not attacking this product or saying anyone made a bad choice here. What I am saying is that this is a budget amplifier. It's design had more to do with sticking features in an attractive box for minimum cost. There are many brands like that. It's very likely that this is a stock circuit design that is sold to companies like CA. The only thing that this company did was pick the features and cosmetics, and market it. That is the reality of mass consumer items. Once you become comfortable with that idea, your upgrade choices become easier and so does your expectation of the final upgraded performance.
This is certainly not the worst product made either, that is not what I am saying. It is solidly "mid-fi" if you will. Better than many, but not the best and not built with a great amount of research into the circuit design.
So, you are determined that this is really a well designed product sold at a bargain price for the good of mankind? Then tell me. Why do any ceramic capacitors exist in this box? How about the carbon film resistors and cheap volume control?
Mike, please do not place your faith in advertising. Don't draw conclusions that have no basis in fact from assumptions you may make. Do always rely on good engineering practices and decide on the safe side where that may be an issue.
-Chris
That is simply not always true, especially when chip type amps are involved. Personal past experience has borne this out many times.
Sorry, but awards are bought. They have nothing at all to do with competent engineering or safe products. This is a fact of life that is not a popular idea with the audio "in crowd". I have been stuck doing warranty for more than one brand that had serious design problems. A couple even caused speakers to burst into flames all by themselves.
Look, I'm not attacking this product or saying anyone made a bad choice here. What I am saying is that this is a budget amplifier. It's design had more to do with sticking features in an attractive box for minimum cost. There are many brands like that. It's very likely that this is a stock circuit design that is sold to companies like CA. The only thing that this company did was pick the features and cosmetics, and market it. That is the reality of mass consumer items. Once you become comfortable with that idea, your upgrade choices become easier and so does your expectation of the final upgraded performance.
This is certainly not the worst product made either, that is not what I am saying. It is solidly "mid-fi" if you will. Better than many, but not the best and not built with a great amount of research into the circuit design.
So, you are determined that this is really a well designed product sold at a bargain price for the good of mankind? Then tell me. Why do any ceramic capacitors exist in this box? How about the carbon film resistors and cheap volume control?
Mike, please do not place your faith in advertising. Don't draw conclusions that have no basis in fact from assumptions you may make. Do always rely on good engineering practices and decide on the safe side where that may be an issue.
-Chris
Hello, Anatech.
I agree with you. It's not perfect amp (for 300$), and I told already - it's just good...
So, I see you have much info about components, used in 340, then can You tell your opinion about tweaking this amp?
Maybe You can give some advices?
What about ceramic caps? If they are bad?
I agree with you. It's not perfect amp (for 300$), and I told already - it's just good...
So, I see you have much info about components, used in 340, then can You tell your opinion about tweaking this amp?
Maybe You can give some advices?
What about ceramic caps? If they are bad?
Hello Chris.
This a slightly generalized statement. Can you give a detailed write up of you "personal past experience" please?
Again somewhat generalized. Would you be so kind as to provide details?
I can certainly see how that could be the case.
I didn't say that. Didn't you mention that a high end brand you once serviced had ceramic caps?
I don't, that's why I no longer buy Hi-Fi mags.
No one is disillusioned as to the superlative ability of the CA 340A either. Nor are we even slightly inclined toward making each other wrong or invalidating others viewpoints. Please?
Rgds,
Mike.
This a slightly generalized statement. Can you give a detailed write up of you "personal past experience" please?
Again somewhat generalized. Would you be so kind as to provide details?
I can certainly see how that could be the case.
I didn't say that. Didn't you mention that a high end brand you once serviced had ceramic caps?
I don't, that's why I no longer buy Hi-Fi mags.
No one is disillusioned as to the superlative ability of the CA 340A either. Nor are we even slightly inclined toward making each other wrong or invalidating others viewpoints. Please?
Rgds,
Mike.
Hi Stream,
My view is that improving most amplifiers should be no problem. Just make sure that the replacement parts physically fit to begin with. That is really important! The ratings should be the same as the original part, or a little higher in voltage for capacitors. In other words, make sure the item you worked on is at least as reliable as it was before you started working on it.
There is a tendency for people to lose sight of the end goal or performance level. You can improve the sound of many things, but not all changes will actually improve the sound quality. If there is a limiting factor that can not be changed or improved, it would make little sense to attempt to improve other things beyond that level.
There are things done due to beliefs or claims of great results that can not be supported for a number of reasons. Therefore, I try to ignore these things unless performing those changes may affect the reliability of the item, or cost a great deal of money for no return. Beyond that, people should experiment. They sure as heck will not listen to good advice to the contrary of what they believe at that time. Why fight in these cases?
Above all, use your good common sense. Relating to compensation capacitors, or RF bypass caps. If the data sheet from the manufacturer of the part indicates those parts are needed, they should be installed. The manufacturer / designer of an electronic part knows a great deal more about it than most end-use companies. Listen to them carefully. BTW, application notes are the best way to learn more. The people who put these together are highly paid professionals who know what they are doing. They are very expensive teachers who make these lessons freely available. That is a great resource for the rest of us smart enough to figure this out.
-Chris
My view is that improving most amplifiers should be no problem. Just make sure that the replacement parts physically fit to begin with. That is really important! The ratings should be the same as the original part, or a little higher in voltage for capacitors. In other words, make sure the item you worked on is at least as reliable as it was before you started working on it.
There is a tendency for people to lose sight of the end goal or performance level. You can improve the sound of many things, but not all changes will actually improve the sound quality. If there is a limiting factor that can not be changed or improved, it would make little sense to attempt to improve other things beyond that level.
There are things done due to beliefs or claims of great results that can not be supported for a number of reasons. Therefore, I try to ignore these things unless performing those changes may affect the reliability of the item, or cost a great deal of money for no return. Beyond that, people should experiment. They sure as heck will not listen to good advice to the contrary of what they believe at that time. Why fight in these cases?
Above all, use your good common sense. Relating to compensation capacitors, or RF bypass caps. If the data sheet from the manufacturer of the part indicates those parts are needed, they should be installed. The manufacturer / designer of an electronic part knows a great deal more about it than most end-use companies. Listen to them carefully. BTW, application notes are the best way to learn more. The people who put these together are highly paid professionals who know what they are doing. They are very expensive teachers who make these lessons freely available. That is a great resource for the rest of us smart enough to figure this out.
-Chris
Hi Mike,
One example I can give you. Adcom designs pretty good products and they use good parts. Some of their earlier GFA series amplifiers had issues with the driver transistors. One they tried didn't have high enough voltage breakdown. Clipping with no load (to cause voltage sag) could cause them to fail. The other drivers did have high enough voltage ratings, but not current rating. Low impedance loads caused these to fail. They couldn't win until "better" drivers came out.
Another company I will not name had a power transformer that put out too high a voltage for the circuit - at the nominal AC voltage rating. Our mains run a bit higher, but within tolerance. The supply voltages were well above the maximum rating for the power supply caps. We had to keep our mouth shut.
Yet another shipped amplifiers were the bias current was too high across all their models that year. High enough to melt the plastic feet. Of course, we had to keep this a secret. I didn't this time, but saved them a lot of damage. I was cut off service for a few months.
I could go on and on for hours. I won't. This is a case where you are very suspicious and I need to prove myself. I can't for every one who pops up and demands proof.
Yes, many brands do, but they are careful where these are put and what type they are. That is good engineering. The caps I saw in the diagrams did not satisfy those two comments above. They do serve a purpose and it is possible that changing these to more expensive types would not improve sound quality due to other factors. I can't second guess the designer unless I am prepared to study this amp in detail. I will not as this takes hours and it would have no benefit for me to do so.
-Chris
Yes, for a reason. The company who was responsible for the fires really does not want me to make this public. To do so would close the door for further support for me.
One example I can give you. Adcom designs pretty good products and they use good parts. Some of their earlier GFA series amplifiers had issues with the driver transistors. One they tried didn't have high enough voltage breakdown. Clipping with no load (to cause voltage sag) could cause them to fail. The other drivers did have high enough voltage ratings, but not current rating. Low impedance loads caused these to fail. They couldn't win until "better" drivers came out.
Another company I will not name had a power transformer that put out too high a voltage for the circuit - at the nominal AC voltage rating. Our mains run a bit higher, but within tolerance. The supply voltages were well above the maximum rating for the power supply caps. We had to keep our mouth shut.
Yet another shipped amplifiers were the bias current was too high across all their models that year. High enough to melt the plastic feet. Of course, we had to keep this a secret. I didn't this time, but saved them a lot of damage. I was cut off service for a few months.
I could go on and on for hours. I won't. This is a case where you are very suspicious and I need to prove myself. I can't for every one who pops up and demands proof.
Not every award is purchased, but many are in effect. No way am I about to point fingers. This is how we excite consumers to buy this and that. It is a system for the audio industry. There are enough real winners to make it hard to pin down to exact instances and easy to defend. Just make a study of the awards given out. Comments and "test reports" are right in the same situation. Laughable some times, but not in a way that can be proved absolutely.
I know. I was making a point.
Yes, many brands do, but they are careful where these are put and what type they are. That is good engineering. The caps I saw in the diagrams did not satisfy those two comments above. They do serve a purpose and it is possible that changing these to more expensive types would not improve sound quality due to other factors. I can't second guess the designer unless I am prepared to study this amp in detail. I will not as this takes hours and it would have no benefit for me to do so.
-Chris
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