Well...perhaps a couple of questions will be valuable:For me flawed means that it does not function properly
I cannot say that a nad c352 is "flawed"
I am pretty sure that with higher speced and more expensive parts could be better (transformer, caps, volume pot, etc.)
But i would not call it "flawed"
- What do you mean by "higher speced"? (power, size, current..what?)
- How did you do the test? (AB, ABX, none of them)
It is easy for me
Aa an example, if we talk about caps I take the datasheet and i read the parameters
Between to caps (for a same working voltage of course) the one with lower ESR, higher ripple current and lower impedance is the better specified. Am i wrong ?
Regards,
gino
It's not only about specifications but also its context
If you are going to design/build a SMPS, the ESR parameter is quite important, but it is almost useless for a linear power supply (transformer + rectifiers + caps). However, the ripple current gets very important in the latter case, even when its not the main thing to take into account because you need the capacitance value first in order to calculate the value of the ripple current.
It's not that easy to read an specification and assume you will get a real improvement if you change a device with another one with better specs. It is part of the "tweaking/upgrading culture".. but electronic science doesn't work that way...
I agree completely on the fact that there is much more that just read a datasheet in designing an amp
But i do not trust the parts in cheap amps. They must be second quality
I will limit to replace the ps caps with something like Epcos same size and good quality
I should also replace the smaller electrocaps with Panasonic, another brand that i think has an high quality/price ratio. I like the 105C series in particular.
I will not revolutionize the amp beacuse i am afraid is intrinsecally limited by design.
For instance they place protections to protect cheap power supply.
I cannot pretend from cheap equipment at a fraction of much more expensive units.
Thanks a lot for your valuable advice.
Regards,
gino
But i do not trust the parts in cheap amps. They must be second quality
I will limit to replace the ps caps with something like Epcos same size and good quality
I should also replace the smaller electrocaps with Panasonic, another brand that i think has an high quality/price ratio. I like the 105C series in particular.
I will not revolutionize the amp beacuse i am afraid is intrinsecally limited by design.
For instance they place protections to protect cheap power supply.
I cannot pretend from cheap equipment at a fraction of much more expensive units.
Thanks a lot for your valuable advice.
Regards,
gino
Indeed.
You could add on an auxiliary capacitor bank. There is room in there. No need to even remove the stock caps.
A bank of 4x 4700 uF per rail would do the trick. You can mount it above the input jacks. The fly in the ointment is that it could trigger power supply protection circuitry, if there is such circuitry.
Replacing caps in a shotgun matter like you propose is not as cut and dried as you think it is. There are risks-
1) It puts more strain on power transformerr and rectifiers, possibly shortening their life.
2) It could possibly allow the output transistors to operate outside their safe operating area.
3) Protection circuitry can counteract you effort, introducing new nasties.
Me too. It works, but you must keep the caveats in mind.
This is what we all would design and build if time and money were no object.
Good luck polishing those turds. At the very least you'll learn something.
Indeed.
You could add on an auxiliary capacitor bank. There is room in there.
No need to even remove the stock caps.
A bank of 4x 4700 uF per rail would do the trick. You can mount it above the input jacks.
Thanks but i do not understand ,,,, which input jacks ?
even if i limit at a 50% uF increase ? i can also act on the caps grade, a better quality i mean
the Transistors are what convinced me to buy it. Are Sanken ! 200W type
I like them even also esthetically.
But I understand your points and thank you for the advice.
I think it would be better to re-size my expectancies
I mean cheap equipment are limited by design and the upgrade is a real challenge
The transistors are quite cheap but the components more expensive and so where the saving is done are so important for the overall performance
I usually look at the transformer. This should be a 200VA. Too little
A good start is 200VA/channel
And actually i heard a harman kardon hk 670 ... much better in my opinion
Much more dynamic
It has a 400VA transformer ... and i heard this, A nice amp indeed but too complex in the input selection section
Thanks again and kind regards,
gino
Because is the economy. You cannot sell a component if there are better and cheaper ones.
If an amp costs let's say 1000 $ new the cost of components would be how much ? 150 $ ? and so the two ps caps how much ? 10 $ ?
If I put two high grade caps of 30$ each I would expect better overall performance.
This caps are labeled Nad, The manufacturer is a mystery ....
I will replace them with good quality caps and see ... and listen i mean,
At least they should be more reliable, with more residual life
The caps are the first part that go in restoring old equipment i guess.
Regards,
gino
I am going by the photo you posted. Is there not enough space to stuff a small PC board somewhere?
You could go 100% increase without worry, in my opinion. Try it and see.
Sometimes. And sometimes it's not worth it. But I've obtained surprisingly good results before.
Well sure. But it reaches a point where you're better off buying or building better equipment.
I do encourage you to try out some of your ideas. I've been down the same road already and I do not regret it; I have successfully met (and even exceeded) my expectations. You will learn something if nothing else. Just remember that you might damage your equipment or waste money on parts. The liability is all yours.
Audio people do this all the time. All you need to sell an expensive inferior item is a good story and some nice pictures, and a few friendly journalists. The really difficult thing to sell is a cheap good item, as people have been conditioned to expect to pay a lot.
As I said, you can't assume that money buys quality. Even when it does, in some cases an 'inferior' component might suit the circuit better. For example, sometimes highish ESR is need to dampen a resonance. 'Upgrade' and you get HF ringing.
I have noticed a phenomenon on here. (It is much worse on other audio sites) The smaller the understanding of audio electronics, the greater the enthusiasm for 'upgrading' by swapping components such as caps, opamps and valves.
This is so true. It's marketing 101.
I've always been one to advocate designing circuits with available components in mind. Some DIY concepts demand results only available from unobtanium parts. If you design a circuit properly for the parts you intend to employ it will work the way you intend it to.
There are times when swapping parts is worthwhile, but it is not the panacea some people make it out to be. I have "upgraded" consumer products successfully before (while being aware of the caveats) but I had a clear understanding of what I was doing and I was not employing a shotgun approach. And as I pointed out, it is often not worthwhile.
I understand it does not make a frog turn to a prince. But ...
If you upgrade a standard cheap pot to a series attenuator you get improvement.
If you replace standard ps caps with higher grade caps you still should get improvement
If you replace a let's say 200VA transformer with another one 500VA with very good regulation you stil get another improvement
How a better part can damage i cannot see
I understand that if a cheap amp has strong limitation by design in current delivery this is indeed a bottleneck
But if you are smart enough you can modify the relevant circuit to get higher current delivery
The only things that seem to me very good even in cheap amps are usually the output transistors.
In a cheap nad c352 i have even found one pair per channel of the exceptional Sankens !!!!
Surely these are not a bottleneck
If I were smart I would remove any current limiting circuit at cost of risking the worst
And after i would upgrade the PS caps with higher grade and higher uF.
Maybe not too much higher ... 50-60% more ?
I am pretty sure that with just these two mods the c352 would sound remarkably better. I am sure of this.
I have the service manual of the c352 but i cannot understand how to eliminate these current limiting circuits that i am pretty sure do exist.
For instance, some years ago i bought for almost nothing a very nice (really) vintage Kenwood amp of which i loved the construction.
This one here
I put it in the system ... what a delusion
An extremely clean sound ... but without bass and so body
I was very disappointed and gave it away for nothing to a friend who is a collectionist
Then I understood that maybe the reason was some current limiting circuits too conservative
This amp revised by a smart guy would fly !
Completely dual mono with 300VA of transformer per channel ...
To find something similar on the market we have to spend at least 2000 $ (or more)
When i will retire i will start studying these damned current limiting circuits and will hunt for old vintage equipment to restore, just for fun
These things are amazing beasts ... but imprisoned. By design.
What a beauty it was ...
Thank you very much to anyone one for the great help
Have a nice day ! In the end ... it's friday !!!!
Bye !
gino
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Not really
, you will lose resolution when trying to set the volumeSurely you'll be better with another pot (a good quality one) or a "digital" pot.
The only improvement I see is, assuming the PS is working properly, a longer operating life for the circuit....but you won't see it before the next 20 years
This is quite true if you are sure your device needs a more powerful PS, but you have to measure several keys parameters and check their values in order to "draw the line"
Have you read about those guys who do "op amp rolling"??? Well, most of OA that they qualify as "bad for sound" (and they are really expensives ones) are oscillating because the PCB and circuit layout wasn't designed for that kind of chip. Even when an oscillation won't damage the circuit, it probably will blow your tweeters...
Sure it is, but you have to study and analize (by simulation) the schematic to check if your modificacion will improve things or it will exceed OPT SOA and it will blow out your output stage.
Happy week-end!
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Current-limiting circuits, when present, are there for a purpose and are based on the very simple idea that clipping peaks does less harm to the listening experience than total silence (due to destroying semiconductors). Simply disabling them shows lack of understanding. A car will go faster for longer if you lighten it by removing the brakes. The ride is exciting; the journey's end is painful and might not be repeatable for either car or driver.
Not really
Surely you'll be better with another pot (a good quality one) or a "digital" pot
Hello ! with a friend we compared an alps blue to a series attenuator
there was no comparison with the attenuator resulting much better
The sound was so sharper and cleaner that was even scarying
I have a nice recording of a cello ... the sound was so metallic so real that was sublime
I have never heard such precision with usual pots
And apart of few very exotic pots like this one
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or this one
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the best preamp use attenuators.
The only improvement I see is, assuming the PS is working properly, a longer operating life for the circuit....
but you won't see it before the next 20 years
so why some manufactures do offer ps caps upgrade then ? just a marketing move ?
I dont think so. There must be something of sound in this solution.
This is quite true if you are sure your device needs a more powerful PS, but you have to measure several keys parameters and check their values in order to "draw the line"
I agree. I am too simple. Then i read that during the peaks the ps caps are working. The transformer is somewhat slower and its duty is to keep the caps charged.
So for the impulsive power caps are more decisive.
this i agree completely. I played with op-amps thinking that they were like Lego pieces
how wrong i was. I got noise and oscillations as you say.
I would never experiment again with op-amps without having a tested pcb and clear directions. Never.
But just replace two caps is another matter.
To blow a pair of Sanken is not that easy
I touched the fins and they are always cold.
The problem is that the Sankens do not get enough "juice" from the ps.
If so they would make even this little amp really sing.
They are 200W types. Some designers consider them the best available for audio amps.
The cure could be a serious 400VA transformer and two big blue caps (or other colour, but at least 20,000uF).
And some circuit mods i agree, that is where i am completely lost.
This bloody current limiting circuits.
They put them also to avoid any problem with assistance.
And so I got 1 or 2 ampere to the speakers ... and the woofers doze.
Happy weekend to you too
Thanks and regards,
gino
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In general, using "better parts" won't cause damage. However there are exceptions.
Perfect example! Increasing the power supply caps increases the power (and heat) dissipated by the transformer and rectifiers. So if you increase the capacitance too much, you risk burning out the transformer and/or rectifiers (plus any collateral damage).
That said, a 50-60% increase probably won't hurt anything.
Generally, yes.
It also increases ripple current, challenging the grounding scheme and potentially radiating more noise.
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