carlosfm said:
Carlos, the first (100n) AND second (120n + 1R) snubbers are parallel with the reservoir caps -- it's a network ! You should look at it in series.
I didn't, but I may not have explained myself very clearly though, I'm well aware it has nothing to do with the diodes (even though it apepars across them), that was my point.
Here I disagree, the chip sees the 1R + cap as part of it's decoupling. It looks like a cap with high-ish ESR.
Andy.
ALW said:
It does.😀
But somehow it makes using big caps before it have much less impact to the sound.
Hi Carlos,
sorry for asking again, but could clarify if you still use a small cap between +/- pins after the RC (1R + 0.12uf)?
Right now, I am using 4700uf Sikorel and 1uf Auricap across +/- pins.
BTW, thanks for posting result. Very good info.🙂
sorry for asking again, but could clarify if you still use a small cap between +/- pins after the RC (1R + 0.12uf)?
Right now, I am using 4700uf Sikorel and 1uf Auricap across +/- pins.
BTW, thanks for posting result. Very good info.🙂
Hey Carlosfm,
Quick question... did the unregulated psu you have here sound better than the regulated psu for the GC that you posted earlier on? I'd like to know so I can choose the better one and go ahead with my GC upgrade 😀 Thanks
Quick question... did the unregulated psu you have here sound better than the regulated psu for the GC that you posted earlier on? I'd like to know so I can choose the better one and go ahead with my GC upgrade 😀 Thanks
ChuckT said:
Can you clarify?
I don't understand your question...
It's all in the schematic.
The amp has 100uf+100nf per rail.
No cap between + and - rails.
300_baud said:
I haven't yet made a direct comparison, but as I said on a previous post, I still think that regulated PSU is better.
If your speakers are easy to drive you can go unregulated.
Capacitors C10 & C11
I simulated the Regulated Power Supply in Protel and the software kept on complaining that the ADJ pin had no "driving source".
Once I removed the capacitor that connects ADJ to GND it worked fine.
Does the design really need these caps. I mean what is their underlying purpose?
I simulated the Regulated Power Supply in Protel and the software kept on complaining that the ADJ pin had no "driving source".
Once I removed the capacitor that connects ADJ to GND it worked fine.
Does the design really need these caps. I mean what is their underlying purpose?
Re: Capacitors C10 & C11
😕
This thread is not about regulated PSUs.
Anyway, are you talking about the LM338?
The CAdj cap reduces ripple, check the datasheet.
D_GR8_1 said:
😕
This thread is not about regulated PSUs.
Anyway, are you talking about the LM338?
The CAdj cap reduces ripple, check the datasheet.
Re: Capacitors C10 & C11
Go read page 8 on the LM317 datasheet. This capacitor is very important on chips like the 3X7, 338 and other variable regulators, where it's not advisable to use large capacitors at the output, to improve ripple rejection.
National claims that more than 10uF does not "appreciably" improve ripple rejection at frequencies above 120Hz. But they also advise to use tantalum caps, which in my experience and other diyer's is ominous. That proves that sometimes the datasheet can and should be twisted a bit.
Many designers claimed great improvements by using medium to large caps at this pin, properly diode protected, of course.
Carlos
D_GR8_1 said:
Go read page 8 on the LM317 datasheet. This capacitor is very important on chips like the 3X7, 338 and other variable regulators, where it's not advisable to use large capacitors at the output, to improve ripple rejection.
National claims that more than 10uF does not "appreciably" improve ripple rejection at frequencies above 120Hz. But they also advise to use tantalum caps, which in my experience and other diyer's is ominous. That proves that sometimes the datasheet can and should be twisted a bit.
Many designers claimed great improvements by using medium to large caps at this pin, properly diode protected, of course.
Carlos
how come?
This may seem a bit not directly connected to the current discussion.But after reading this thread I thought of doing a slight experiment. I had a unregulated PS with 6800uf per rail.It is just ordinary bridge rectifier without any snubber or anything else.I am using diodes that are capable of handling 6A current. I replaced the 6800uf with a 1000uf capacitor. I am using lm3886 based GC.
The difference that I could make out was the amp sounded somewhat lighter and a bit nice to hear.But when I had used the 6800uf capcitor on rails it sounded more kind of heavy.
Is it beacuse of the big caps??
This may seem a bit not directly connected to the current discussion.But after reading this thread I thought of doing a slight experiment. I had a unregulated PS with 6800uf per rail.It is just ordinary bridge rectifier without any snubber or anything else.I am using diodes that are capable of handling 6A current. I replaced the 6800uf with a 1000uf capacitor. I am using lm3886 based GC.
The difference that I could make out was the amp sounded somewhat lighter and a bit nice to hear.But when I had used the 6800uf capcitor on rails it sounded more kind of heavy.
Is it beacuse of the big caps??
Re: Re: Capacitors C10 & C11
There's a very good reason for using a tantalum -- they are much better in preventing oscillation in low-dropout regulators (not the LM317 -- this isn't an LDO) because of their low ESR, they are more temperature stable, and smaller-- so says Nat Semi.
I doubt they sound very good in a signal path, however. I measured the distortion of some tantalums (2 back to back) just now at around 1.0% -- compare this to a polypropylene at a negligible level.
carlmart said:
There's a very good reason for using a tantalum -- they are much better in preventing oscillation in low-dropout regulators (not the LM317 -- this isn't an LDO) because of their low ESR, they are more temperature stable, and smaller-- so says Nat Semi.
I doubt they sound very good in a signal path, however. I measured the distortion of some tantalums (2 back to back) just now at around 1.0% -- compare this to a polypropylene at a negligible level.
Re: Re: Re: Capacitors C10 & C11
For a regulated PSU to use on a GC, normal voltage is around 30V.
I don't think that tantalum caps exist at more than 35v rating, and even these are already big.
They are not reliable when working close to their voltage rating.
Huh.... no, let me put it this way: they are not reliable.😀
jackinnj said:
For a regulated PSU to use on a GC, normal voltage is around 30V.
I don't think that tantalum caps exist at more than 35v rating, and even these are already big.
They are not reliable when working close to their voltage rating.
Huh.... no, let me put it this way: they are not reliable.😀
Re: Re: Re: Capacitors C10 & C11
There's a very good reason for no using tantalums: they catch on fire. Seen several cases of that. A good low ESR from Panasonic should do better.
For a good attack on tantalums by serious people read this:
http://www.capacitors.com/picking_capacitors/pickcap.htm
Carlos
jackinnj said:
There's a very good reason for no using tantalums: they catch on fire. Seen several cases of that. A good low ESR from Panasonic should do better.
For a good attack on tantalums by serious people read this:
http://www.capacitors.com/picking_capacitors/pickcap.htm
Carlos
Re: Re: Re: Re: Capacitors C10 & C11
having been a subscriber to Audio in the 1980's I read Walt's article in its original form!yet there are a few recidivists who continue to believe that tantalums have a place in the signal path.
here's my experience with an LDO -- ultralow noise units from Linear -- they worked OK with an aluminum electrolytic, but very very well with tantalum.
in the regulated GC as put forward by Carlos, a standard, off the shelf regulator is employed so I wouldn't expect the same kind of problem as with an LDO. I don't have any tantalum's over 35V in my lunchbox anyway.
when tantalums fail, they fail miserably, shorting out -- and they can take the regulator with them !
it may not be as important in Brazil or Port -- but tantalums have better ESR over temperature -- in cold temperatures an aluminum electrolytic isn't what it's thought to be!
carlmart said:
having been a subscriber to Audio in the 1980's I read Walt's article in its original form!yet there are a few recidivists who continue to believe that tantalums have a place in the signal path.
here's my experience with an LDO -- ultralow noise units from Linear -- they worked OK with an aluminum electrolytic, but very very well with tantalum.
in the regulated GC as put forward by Carlos, a standard, off the shelf regulator is employed so I wouldn't expect the same kind of problem as with an LDO. I don't have any tantalum's over 35V in my lunchbox anyway.
when tantalums fail, they fail miserably, shorting out -- and they can take the regulator with them !
it may not be as important in Brazil or Port -- but tantalums have better ESR over temperature -- in cold temperatures an aluminum electrolytic isn't what it's thought to be!
Re: Re: Re: Re: Re: Capacitors C10 & C11
That is exactly what happened to my old scope.
It's broken, no image, smoke at power-on.
Two weeks ago I opened it and the problem was a shorted tantalum cap that took the life out of a bunch of transistors.
Curiously, the tantalum cap was intact, no sign of anything wrong, but shorted.
What
ed was the transistors.
On regulators I would rather use an electrolythic bypassed with a ceramic than use tantalums.
jackinnj said:
That is exactly what happened to my old scope.
It's broken, no image, smoke at power-on.
Two weeks ago I opened it and the problem was a shorted tantalum cap that took the life out of a bunch of transistors.
Curiously, the tantalum cap was intact, no sign of anything wrong, but shorted.
What
ed was the transistors.On regulators I would rather use an electrolythic bypassed with a ceramic than use tantalums.
The benefit of tantalum capacitors is their size. If you're building something to a size limit then they can be a good choice.
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