Beginner's Gainclone, HiFi LM1875, The Amplifier Board

[danielwritesbac]

This is for the purpose of an accessable hifi gainclone amplifier, it is in reference to Commercial complete Gainclone kit for a beginner? and it is by request.

Here's LM1875, at low cost, and easily made by following the "play by play" photographic format.

But, first, let's have a look at how "not" to use the LM1875: If you're planning the manuever of pushing inefficient speakers with great force, then try something else.

Since this thread starts from Gychang's post and since he is famous for the B20 hifi genre speakers, then I think that the laid-back hifi sounds of LM1875 could be a perfect fit.
The chip also works as well with large DJ speakers, as it does with most speakers at 88db efficiency or higher.

The LM1875's large tolerances, "only 5 pins hookup," and the absence of the spike system, can give you 25 watts per channel of high fidelity, at a bargain price, and with an easy time of building your own.

[danielwritesbac]

There are kits for LM1875. Have a look:

http://www.electronics123.com/s.nl/it.A/id.425/.f

http://www.siliconchip.com.au/cms/A_103236/article.html

Mini LM1875 design Wow!

Finally made a LM1875 amp


And, we can build our own on veroboard (phenolic board), with parts available anywhere. . .

[danielwritesbac]

For example, here's an LM1875 that I built on veroboard (phenolic, no pads) quite a while back.

For now, I'd like you to see that the 5 pins are quite useful and well located.
Here we have the input on the left side, and the power circuit is down the middle, and the speaker output is on the right side.

The optional items were deleted from this photograph, so you can have a clear view:

Edit: Note that the ground stripe that's down the center doesn't connect to the LM1875 chip.

[danielwritesbac]

Parts list (per each channel):

LM1875
A size TO220 Heatsink Insulator

Phenolic board (veroboard)

Resistors
27k
15k
820R
470R
2.2R

Capacitors
2 of 470uF 50v electrolytic
2 of 100nF ("104") ceramic

This is about $6 worth of parts.

[danielwritesbac]

Okay. I just got a request for "Technicolor"!

I can't wait to see John's reaction to this one.

[Bluto]

Hey Gychang -

Hear that??!!

Famous!!

Someday I'm gona be famous too!

Bluto

[Nuuk]

Someday I'm gona be famous too!

"Fame is but a fruit tree
So very unsound.
It can never flourish
Till its stalk is in the ground."

Nick Drake. (Song 'Fruit Tree' from the album 'Five Leaves Left')

[danielwritesbac]

Originally posted by danielwritesbac
Parts list (per each channel):

LM1875
A size TO220 Heatsink Insulator

Phenolic board (veroboard)

Resistors
27k
15k
820R
470R
2.2R

Capacitors
2 of 470uF 50v electrolytic
2 of 100nF ("104") ceramic

Whoops! Where's the input filter cap?
I forgot to list the 2.2uF capacitor.
*This can be a "made for audio" electrolytic or a "poly" capacitor.

Application note:
Since LM1875 is a lower powered amplifier, you can use a poly input filter cap of a smaller value, so that it produces rich bass, but not lower than "about" 40hz. That "conserves" the power of your LM1875 so that it will play as loud as a larger amplifier. This poly cap can be as small as 0.47uF.

A friend sent me an e-mail about the missing cap, and he gave me some more goodies for our "optional components" section, which is coming up, right after the assembly demonstrations.
Thanks man!

[Edits]

Hi, you give me reasons to cook my LM1875. I'am watching!

[danielwritesbac]

Originally posted by danielwritesbac
. . . poly cap can be as small as 0.47uF.

And, he just emailed me again. The forum regulations prevent me from simultaneously quoting the contents of his email and giving his name.

I DO wish that I could give him credit. But, the content is most important, and here it is.

I don't agree that a low power amp should settle for reduced performance.

Therefore, choose your input filter cap size, based upon the capabilities of your speakers.
Simply put, that's "smaller with smaller" and "larger with larger"

We're aiming for efficiency, not limitations. So, I hope to have cleared that up.