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Old 13th December 2004, 05:08 PM   #11
Cobra2 is offline Cobra2  Norway
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Default I think the LM3886 is good

but it all comes down to what you compare it against.
IMO it works great, considering cost & parts-count.
The fact that Jeff Rowland uses them is no guarantee for sound-quality...he also uses icePower & smps...

I have much better transistor and mosfet amps around, driving any load, but also carries hefty price-tags...

Arne K
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Old 13th December 2004, 06:10 PM   #12
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Default Re: Well, P-A......

Quote:
Originally posted by Jocko Homo
Enquiring minds want to know........

A member asks this unrelated question in this thread:

"will i be sinbinned for this as well?" for throwing politics into this discussion for no good reason.


Well? Be consistent for once.

Jocko

and so, i'l get back onto the topic then Mr.Homo.

I must personally admit that i'm not impressed by the lmxxxx line of chips so far, but i have only gone so far on teh subject, so i have lots of things to try before i make a definite conclution.

So many people cant be wrong, or at least so i hope.

As for audio Nirvana, i dont think it can be found in a chip.
the search continues.

regards
marius
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Old 13th December 2004, 06:27 PM   #13
XELB is offline XELB  Portugal
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Hello.

Since you all are speaking about sound quality and I am new arround here....
I would like to build a Kit..... a kit that could drive my 6 oms speakers!

Now I am using a Pioneer A-702R wich sounds nice!

Building a Amp based on the LM3886 Kit could I achive better quality and drive my Wharfedales?
(compared with the Pioneer A-702R or Audio Analogue Puccini special edition)



Thanks.
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Old 13th December 2004, 06:29 PM   #14
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Default Re: Re: Chip amplifiers

Quote:
Originally posted by moving_electron
[snip]"Some implementations (DIY or most commercial) using high capacitance standard supplies (non-regulated) produce non exciting sound. A well implemented chipamp using low capacitance supply (arguably creating some limits) or using a regulated supply can sound very very good indeed."
[snip]

This is conflicting. A high cap supply will appear very close to a regulated supply. A low cap supply will heavily modulate output on peak signals, which both a high cap and a reg supply will do (much) less. Are you sure you haven't switched your statement around?

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Old 13th December 2004, 06:53 PM   #15
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Default Re: Re: Re: Chip amplifiers

Quote:
Originally posted by janneman



This is conflicting. A high cap supply will appear very close to a regulated supply. A low cap supply will heavily modulate output on peak signals, which both a high cap and a reg supply will do (much) less. Are you sure you haven't switched your statement around?

Jan Didden

Not with GC's. as everyone who have played with theese chips know, they sound like **** with high large reservoares of capacitance, or rather the inductans that the capacitans brings with it, to more or less extent.

I'm being rather bastant (as in dead certain that my knowledge is aqurate) here now, but this is regarded as a common fact concerning GC's is it not?

regards
marius
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Old 13th December 2004, 06:58 PM   #16
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P-A, you opened this thread in my name?
Wooooowww!
Fair play!!!
Did I ever said that an LM3886 is not a good power IC?
It's what I use!
Your implementation of the LM3886 is not correct.
It doesn't sound good.
High capacitance unregulated with these chips doesn't sound good, and the only thing that improves this with fantastic results is the snubber on the PSU, with the values I reported on this forum.
You can see the snubber on roibm's PCB, can't you?
You can also see some electrolythic caps on the op-amp's PSU pins, can't you?
You can see that I advised him not to use the caps across the diodes, can't you?
You can't see but I tell you: I advised him to remove the servo (and terminate that op-amp's channel).
You can't see but I tell you: without the servo he has 0.2mv DC offset.
You can't see, but I told him to remove the cap from NI to gound (filter) and also the cap across the feedback resistor of the op-amp, can't you?
You can't see but I tell you, he's not using the AD8620 anymore, I advised a much better option.
Your zobel was removed and the output snubber has other component values.
Do I need to say more?
The changes were much more that these, they included changing component values too, and the amp sings now.
For all this work, I would do an amp from scratch.

PS: with a good PSU (and some other tricks) I'm now getting an LM1875 to drive my difficult Epos 11 speakers, with very good results.
So, forget the chip for a while and concentrate on the rest of the amp.
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Old 13th December 2004, 07:00 PM   #17
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A high cap supply will also have greater inductance. The solution is to decouple the power supply with smaller cap. As large caps can resonate with small parallel caps, the small resistors in series with large caps are required. I don't know why Carlos placed them in series with small caps.
Another solution to lower inductance is to put several smaller caps in parallel e.g. 5x2200uF instead one 10000uF. May be Carlos can check it.

Ooops, I think this will appear after Jan post. You are so fast, my friends
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Old 13th December 2004, 07:11 PM   #18
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Quote:
Originally posted by dimitri
A high cap supply will also have greater inductance. The solution is to decouple the power supply with smaller cap. As large caps can resonate with small parallel caps, the small resistors in series with large caps are required. I don't know why Carlos placed them in series with small caps.
Another solution to lower inductance is to put several smaller caps in parallel e.g. 5x2200uF instead one 10000uF. May be Carlos can check it.
I've tested that.
Of course I use a small film cap after the big ones.
But it isn't a solution, the amp will still not sound good.
Paralleling caps is also not a solution, I've tried that long ago.
Only the snubber makes a "click".
Suddenly the magical midbad and treble that were muted appear from nowhere and then yes, you have a serious amp, not for kids.
With the snubber, the amp sounds as good as the low capacitance one (1000~1500uf per rail/chip) in the midband and treble, but with the added advantage of much better, tight bass and driving ability.
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Old 13th December 2004, 07:15 PM   #19
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Default IMO, it's a "catch 22"

The chip does not sound good with large caps...but cannot drive any more complicated load than a 1.th order 2way system with small caps...

I will save my chips for a more "PASS" way of use...maybe among the 7...

Arne K
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Old 13th December 2004, 07:16 PM   #20
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I so look forward to try this snubber of yours, Carlos..

is the wattage value of the resistors very critical? and the caps? i had theese 100-140 pf 1000v condensators i needed to get rid of, but they dont acuratly match the values you posted. Is this critical? common scence tells me no, but then, this is audio, no logic should bhe applyed here.
they were so bothersome to have lying around, so why not put them in the GC?
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