| georgiano |
hello guys.
i'd wanted to build 3886 amplifier for a long time, but couldn't decide wich schematic to use. i found this forum several days ago(it was such a surprise for me that lm3886's were such respected chipamps), and downloaded several schematics from here.
my problem is that i can only build schematic, and i'm totaly helpless in creativity. i mean looking/examining scheme i can not figure out what and how to change to make it work and sound better.
well, i'm looking for help and advice from you guys.
which schematic do you recomend to build, looking at quality - not simplicity? i know, "best" is word subjective, and if it cannot be said wich design is best, it certainly can be said wich ones not to build. so there must be well proven designs, that are a head above over others.
i understand that this question would be often raised up, and that i should use search, but searching this forum and finding long threads(some over 170 pages :) ) they say nothing to me because higher skills required to understand them.
well, i have built several amps before, solid state and tube, so i'm not totally dumb at all:)
my goal is to build decent sounding (as much can be achaived from 3886's) amplifier for 60 wats of power at 4 ohms of load.
can someone give some decent schematics?
thanks for reading this :) |
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| Bazukaz |
I would recommend you use circuit that is in Lm3886 datasheet.
It can be found at www.national.com
It is very simple and easy to build.
However , don't forget that all ground connections must come to a one ground point.Forgetting to do so may cause stability problems or/and increased distortion. |
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| Jay |
| The balanced one is the best sounding. But it is not a well proven design. Unless you know electronics well, you should find help from metalman to build one without much problem. Unless Nelson Pass himself design the schematic, I will prefer to stay away :D |
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| sagarverma |
hi Jay,
its your territory(lm).advise req.i also need that(my lm amp burned out and took away my $100 pioneer woofer with it:bawling: ) |
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| georgiano |
well, i was considering to build mauros design. i found schematic on first page. but found on 170-th page that there was RevC version of it. i cannot read all the 170 pages. do you have this version of his amp?
i read X-Calibre topic too. is your amp's final version available on topic's first page?
there was also word Thorsen floating around. i couldnt find out what it is, looks like it is a good design too.
| quote: | | I would recommend you use circuit that is in Lm3886 datasheet |
something makes me to think that schematic in datasheet shouldn't be the greatest available. i don't like "example" word in there ;)
| quote: | | The balanced one is the best sounding. But it is not a well proven design. Unless you know electronics well, you should find help from metalman to build one without much problem. Unless Nelson Pass himself design the schematic, I will prefer to stay away |
sounds chinese to my ears :) |
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| Nordic |
| Somewhere between page 152 and 156, we posted the full schematic.... sure you'll find it now. |
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| Jay |
Hi sagarverma,
nice cat you have there! I always like cats because they seems to like me. I don't know why, but I guess they have a good intuition about good people :D ;)
Anyway, I have lots of experience with chip amps in the past, but not with GC. I built several GC but don't have enough time for tweaking and comparing with the same setup, so it is actually difficult to tell which schematic is better than which.
Often, first impression tells the truth. So I was impressed with balanced one (hi georgiano, sound chinese you said?), and the single supply example. (Hi georgiano, National examples are not as bad as Philips').
And then about inverting schematic. It is almost coincidence that everytime I like my chip amps (or opamps pre), they happen to be inverted. And I have good impression with inverted GC as well (compared to non-inverted). |
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| sagarverma |
hi jay,
i have made only single ckt of lm,from app. notes.its ok.but due to my fault,it smoked out and took my woofer with it.
offline::::::cats r cute,so r cubs(lion's strictly).:cool: |
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| georgiano |
| quote: | | hi georgiano, sound chinese you said? |
yep:rolleyes:
| quote: | | Hi georgiano, National examples are not as bad as Philips' |
yea, but i am looking for the good one, not for "not as bad" one. |
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| Mick_F |
I made a "copy" of the Gaincard amplifier on the basis of the LM3886. I like it a lot and a detailed description is here
Mick |
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| doggy |
hi Mick
Nice pictorial guide to your project and great clear close up shots; what camera did you use?
And also I am trying to get a handle on these op amps; If anyone would care to help me understand the question is: what effect has the feedback resistor? I have seen different values 4.7 kr to 22kr; anyone care to comment?
cheers
doggy:santa2: |
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| Nordic |
| It in combination with the input resistor defines the gain level of the amp, you get the gain by deviding the Fb resistor with the input one.... so an amp with 220k feedback and 10k input resitor has a gain on 22, the input resistor in turn would determine the input sensitivity.... i.e. how high a voltage the signal would need for peak levels. |
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| doggy |
Yes, have been searching, Rod Elliot has a lot of good info. Still, I have seen ratios of gain from 21 to 28; also what factor would you use to set the gain? distortion or. And also the resistor to ground I have seen 100r to 1k ohm. I guess with 100r more output power will be wasted to ground as heat?
doggy
:rolleyes:
p.s. sorry georgiano, my intention is not to divert this thread, I am also building a lm3886tf amp without a pcb.:) :) |
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| Mick_F |
Doggy, the pictures were taken with an ordinary Ricoh Caplio el cheapo digital camera.
The amount of gain depends on the rest of your system. If you have a pre with gain, you can user lower values such as 20 for the power amp. Without you should go for higher values. Mine has a gain of 33.
It is easy to exchange the ground resistor in the feedback loop (or, as Nordic says, the input resistor for inverted designs) to set different gain, so just try it out.....
Mick |
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| Jay |
Hi doggy,
I have always tried to use as small as feedback possible, as long as the circuit is stable with such a small feedback. Linearity has never been my concern. This is still on topic ;)
There you are, georgiano.
Even with the "same" circuit, you can still have choices to make it different, hence different result or quality. Different gain/FB, different pot, different component type, and at last something you cannot control is the power supply quality. Remember also that mostly I made mine using P2P like Mike did.
If the balanced 3886 you have heard sounded like chinese, and that you want something that is not just "not as bad", why build GC?? It's not an audiophile quality amp by itself. Maybe not with the right preamp or driver or anything you can add in front of it (like Mauro's). |
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| georgiano |
| quote: |
There you are, georgiano.
Even with the "same" circuit, you can still have choices to make it different, hence different result or quality. Different gain/FB, different pot, different component type, and at last something you cannot control is the power supply quality. Remember also that mostly I made mine using P2P like Mike did.
If the balanced 3886 you have heard sounded like chinese, and that you want something that is not just "not as bad", why build GC?? It's not an audiophile quality amp by itself. Maybe not with the right preamp or driver or anything you can add in front of it (like Mauro's).
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as i mentioned in first post, i'm not Shakespeare of electronics. i mean i cannot compose or tune up circuits. but it doesn't mean that i cannot build something that i see and cannot tell what type of circuit it is.
there is different levels of diy people, and i am at that level where i can just build with given schematic if further tuning is not required. and i am not proud nor am i ashame of it. :)
talking about balanced amps. i really don't know what it does mean. and i have never said that i dont want to build it. if it really sounds best and if you'll show me the schematic of it, i will gladly build it. but just saying to build balanced one helps me no way, for the reasons written above. :)
why 3886 amp?
it is cheap.
it is not so hard.
it is chip amp forum :)
yes i know, it is NOT audiophile. but it doesn't mean not to try to get the best out of it. if you can show me some audiophile grade schematic which will not be much complex and expensive than 3886amp, i will be happiest man on the earth :)
and i have not heard any amp on 3886 yet. nor the balanced one.
i'm open to any idea and advice :) but pleeeease, dont write it with pro language :)
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Maybe not with the right preamp or driver or anything you can add in front of it (like Mauro's).
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you mean it's bad or it's good? i have stopped at Mauro's RevC design at this moment. |
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| Mick_F |
Who says that the LM3886 cannot be used to build an audiophile amplifier?
Mick |
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| rudi |
I think you have a few choices and if you are looking at Mauro's design. I suggest you buy a board from Twisted Pear audio. They have a very neat little board that will do you fine, I can guarantee you it is Audiophile quality
If you feel like etching the board yourself you have two options. Do the My-Ref that Mauro originally did or you can build the X-Calibre. I can give you all the needed implementations and you need not do another bit of tweaking after that. |
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| Jay |
| quote: | Originally posted by georgiano
and i have not heard any amp on 3886 yet. nor the balanced one.
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Oh, now I see what you meant with "it sounds chinese". I misinterpreted
that. Well, with balanced amp, you need 2 LM3886s for each channel.
I had a hard time following the thread about this design. A hard time
also in building it. Not design you're looking for IMO.
So, it seems that good LM3886 designs incorporate extra devices, mostly
a buffer (I don't think there's a CDP-->Chip Amp-->Speaker link that can
produce audiophile sound).
JLTi has a tube buffer. No documentation found for the audiophile grade
circuit of this amp. It is for more knowledgeable DIYers.
Mauro's design with LM318 (if I'm not mistaken) is the one with good
documentation. I think you are already on the right direction.
I didn't have LM318 so I haven't built this one. May be I'll try harder
finding one someday, because I still have plenty of LM3886 anyway.
Well, who said 3886 based amp cannot be audiophile quality? :) Of course,
it depends on your definition of audiophile quality. People who are
often called Audiophiles, tend to be more involved with tube amps. If
you're a tube fanatic (where I'm not), I don't think you will call GC
an audiophile amp. IMO, audiophiles would never stopped finding "better"
sounding system. If you're one, I don't think you will stop at 3886.
By that, 3886 amps are not supposed to be audiophile amp.
Pass Labs' Aleph3 is better than GC. Actualy, Aleph3 was the amp I used
to compare with my GC. That's why the GC failed. The comparison is done
with the same system, and with enjoyment as the only parameter. I don't
know how much it will cost you to build an Aleph. Aleph doesn't need
expensive components like GC. The cost probably high in transformer.
Probably. |
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| sagarverma |
| quote: | Originally posted by Mick_F
Who says that the LM3886 cannot be used to build an audiophile amplifier?
Mick |
it can be.use it with 3 or 4 or 5 or 6 or..............way Xover,and it will definately be audiophile. |
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