My LM3875 Poweramp

hatasa · 2003-02-07 4:52 pm

Hi,

Circuit base on the gaincone, but without the volume....

And the gain is lower than the suggestion circuit.

The Power supply cap using a pair of the 4700uf
working voltage at +/-35V

Using the 470uf for the by-bass

Resistance using with the RMG Japan...

Sound looks great, still running-in!

An externally hosted image should be here but it was not working when we last tested it.

Ilianh · 2003-02-07 5:04 pm

Hi, Good work, they look great

I've always wondered, those amps have 2 channels, they are 30 watts on 8 ohm each i think, can you bridge them?
to make like 60 watts on 8 ohm? Because I have like 5 lm3875 and i wanted to do something out of them.

Christer · 2003-02-07 5:10 pm

Those are probably the smallest monoblocks I have seen.
I wonder, however, do those boxes really provide sufficient
cooling or are you running the chips on rather low supply voltage?

SlaitH · 2003-02-07 5:12 pm

looks very nice

cool thing with the small boxes. There isn't any coolers it doesn't get to hot??

/Patrik

Ilianh · 2003-02-07 5:15 pm

Its true that these generate alot of heat, and I bet those monolocks get hot.. But I'm sure that unless excessive hours of listening at max volume its not dangerous for the LM's.

halojoy · 2003-02-07 5:35 pm

hatasa - real good DIY Audio!

hatasa,
this amplifier DOES NOT fit in,
in the "UGLY amplifier" thread.
I like your work very much.

I do not think there is any worrying for too much HEAT.
When listening to music in a normal way
not much cooling is needed.
And I am sure LM3875 can take a lot.

Of course Capacitors can suffer from heat.
That is why I never put them TOO CLOSE to big heatsinks.

/halo - wants to buy hatasa amps ...

Ilianh · 2003-02-07 5:51 pm

Hi, Good work, they look great

I've always wondered, those amps have 2 channels, they are 30 watts on 8 ohm each i think, can you bridge them?
to make like 60 watts on 8 ohm? Because I have like 5 lm3875 and i wanted to do something out of them.

gosh... that was bad sorry, I got mixed up with some other amplifier with similar a name ... My bad..

lm3875 are 56w into 8 ohm.... with a 100w peak.

bah.....

(no, I'm not drunk)
I'm at school, working on lab, just tought I'd take a pause to see whats up on diyaudio..

halojoy · 2003-02-07 5:58 pm

hatasa said:
Hi,Circuit base on the gaincone, but without the volume....
And the gain is lower than the suggestion circuit.

The Power supply cap using a pair of the 4700uf
working voltage at +/-35V
Using the 470uf for the by-bass Resistance using with the RMG Japan...

The only thing I would change is the Black Gates.
In my Opinion just a waste of money.

And ordinary Resistors are absolutely good enough
for any circuit.

/halo - have a little less money, than others :clown:

and manage just as good anyway

captainpabst · 2003-02-07 6:03 pm

ok call me an idiot, but i've been wanting to do a gainclone amp for a while (not the reason i'm an idiot

) i only say that because i havent been able to find any schematics, so here i am asking. i'll probably be using lm3886t chips. so post a schematic for my simple mind. thanks
-Eric

Peter Daniel · 2003-02-07 6:07 pm

http://home.student.utwente.nl/f.s.bouwman/audio/thor-amp.html

Cradle22 · 2003-02-07 6:15 pm

Re: Re: My LM3875 Poweramp

Hi!

halojoy said:
/halo - have a little less money, than others
and manage just as good anyway

/nice statement, I could include that one as well as my catchy line...

Instead of BG I take Panasonic FC, not that cheap, either, but compared to BG...

The only part I make no compromises are the PSU caps... BHC SlitFoil all the way (if capacitance exceeds 5000 uF, else I also take paralleled Pana FC)...

Still I keep spending too much money on audio electronics which I never use after they are finished...

Nice Weekend!

Arndt

platenspeler · 2003-02-07 6:51 pm

saletel said:
ok call me an idiot, but i've been wanting to do a gainclone amp for a while (not the reason i'm an idiot ) i only say that because i havent been able to find any schematics, so here i am asking. i'll probably be using lm3886t chips. so post a schematic for my simple mind. thanks
-Eric

I built this one:

An externally hosted image should be here but it was not working when we last tested it.

Resulting in:

An externally hosted image should be here but it was not working when we last tested it.

Internals:

An externally hosted image should be here but it was not working when we last tested it.

Rest of story and links on http://www.euronet.nl/~mgw/diy/uk_index.html GeenKloon project.

regards,

Maarten

captainpabst · 2003-02-07 7:00 pm

thanks for the links and schematics, now i jsut need time....
-Eric

Boxbldr681 · 2003-02-08 12:04 am

Glad I read throw this post..Copy a schematic or two and checked my IC drawer and behold 1 LM3875. Junked a old mike amp for it's box and 2 hours later have a good looking single channel "Gainclone". Fired up with now problems and sounds pretty damn good. Didn't have anything other than a Spague 2.2 cap for the input but should do fine I'll hope. I'll look at it though the scope when I get a good tone generator, the one I use for R.F. amps is not to pretty.
Now I might just make a pair for my work room. I think for the size and ease to make that it sounds real good. Nice project...
Now to find a larger box or two that match.

jean-paul · 2003-02-08 12:20 am

The only thing I would change is the Black Gates.In my Opinion just a waste of money. And ordinary Resistors are absolutely good enough for any circuit.

Halo, just try BG once and you'll talk a different story. Keep your open mind and experiment first and criticise afterwards. You won't for sure, I can tell you that.

What's the point anyway of changing them when they are already built in ?? A real waste of money...

Jean-Paul

Peter Daniel · 2003-02-08 12:33 am

The only thing I would change is Black Gates too, but to non polar type N. They supposed to be twice as good as standard ones and 3 times more expensive.

grataku · 2003-02-08 12:36 am

hatasa said:
Hi,

Circuit base on the gaincone, but without the volume....

And the gain is lower than the suggestion circuit.

The Power supply cap using a pair of the 4700uf
working voltage at +/-35V

Using the 470uf for the by-bass

Resistance using with the RMG Japan...

Sound looks great, still running-in!

How does the sound compare to the Audio Research on the lower shelf?

Lovely rendering of the Gainclone by the way!

SkinnyBoy · 2003-02-08 2:48 am

I think they would look better one stacked on top of the other... lol,..

I think its time I did something. .

hatasa · 2003-02-08 4:23 pm

Hi all,

Happy to got many feedback for the job....

Today I tried to operate the amp from 9am to 6pm. With the normal volume, ofcoz there are the room with the air condition.... The room temp. around 21c to 24c. I found that the case usually stand around 45-50c there! It looks quite stable....

I using the Redrose Rosebud Speaker
Preamp using with the Clone Marantz Model 7 tube line stage (And I dont think it matching well with the gainclone..... I building the new opamp preamp for the gaincone)

Source using the modified Pioneer DV-733A (US version should be Eilte DV47), with the LCaudio Zapfilter and the M2XO-1ppm clock module which using TCXO from the new company called MOD2.)

Will update more info on Monday..... bigeyes:

PS: Ah! Yes! Another amp which you saw on the photo is the AudioResearch Classic 30 Poweramp!

:

pinkmouse · 2003-02-13 12:55 am

Does any one have any objections if I split this discussion off into another thread?

The subject has drifted slightly off topic

The new thread is here:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=11099

My LM3875 Poweramp

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