Newbie GainKlone

[VoLCoM]

Hi,
I'm starting building a gaincard clone with a LM3875 and i wanted to know if i have to use a for example 40-0-40 or I can use 40-0
because i'm going to power it with Batteries like...2 12V
in series l'll have 24 volt is it enough to power this GainKlone?
and if i must use 40-0-40
how do I do this with batteries?

[Steve Eddy]

Originally posted by VoLCoM
I'm starting building a gaincard clone with a LM3875 and i wanted to know if i have to use a for example 40-0-40 or I can use 40-0
because i'm going to power it with Batteries like...2 12V
in series l'll have 24 volt is it enough to power this GainKlone?
and if i must use 40-0-40
how do I do this with batteries?

A single 24 volt supply (i.e. 24-0) is really no different in terms of power output than a double 12 volt supply (i.e. 12-0-12). If you're just going to use two 12 volt batteries, then make the supply 12-0-12. But that will only get you about 6 watts or so. If you want more power, you'll need to get another pair of batteries and connect each pair in series so you essntially get a 24-0-24 volt supply. If you get to more batteries again, you can do a 36-0-36 volt supply.

It really all depends on how much power you need.

se

[VoLCoM]

I'd like to get 60watt is it possible with a LM3875?

i'd like to make this small and "not heavy" lol. Because I want it to fit in my backpack with 36volt how much power can i get?? i have to mention the amp will not be Stereo. I'll plug the 2 channels of my walkman in the amplifier and the output will be in 1 Speaker and i want it to play very loud!
lol
-Guillaume

[Rarkov]

Hiya,
No, the chips are rated for 56W if my memory recalls...Also the distortion goes sky high when you get anywhere near that level. a +-24V supply is fine. Do the following:

|------ +V
+
12V
-
+
12V
-
|------ 0V
+
12V
-
+
12V
-
|------ -V

Sorry - I know it isn't that clear, but it'll work!

You may have read my recent thread on PICs of my gainclone, but they already play extremely loud. I found that supplying them with 38V did more damage to the sound (and percieved power output) than good. Stick with a 24V supply and use sensetive speakers. That is far more important! Have fun!

Edit:
You can't just tie the two Left and Right signals together by the way...You'll have to use an Opamp mixing circuit to make it Mono. You could make a (still) stereo cheap amp by using the same power supplies etc so no need for extra caps, rectifiers etc. You decide.

Gaz

[shyfx]

I hope I am not hijacking the thread here, but on the power supply questions for a gainclone, can you use a transformer that isn't centre tapped and use a circuit like this to get the +, 0, - ?


ps; i thought I would post it here because maybe you can use a single battery and power the gainclone with a circuit like that instead of multiple batteries

[VoLCoM]

Rarkov,
You mean...that i plug 2 12V in Series to Get 24V on the +
and the same on the -
If the batteries are for example 7 000mah this mean that i'll get
for the total 14 000 mah and 24V ???

Can i plug the batteries in the circuit of shyfx???
or i have to change the resistor value?
or I didn'T understand right and these are 2 different ways?
which one is better?

[Rarkov]

Hi,
No you've misunderstood a little. The method with 4 batteries that I explained will give you 7000mah (if that is what one cell is rated at). This would double if they were is parallel, but then you would only get 12V...You see electronics is all about trade offs!

The circuit indicated by shyfx is to give the same effect but only using "one" cell. If you look at the circuit, it produces a virtual ground half way between the full potential of the cell. So for this application you would still need all 4 cells to produce the +-24V. This is why I had "one" in quotation marks! Now this is where I am slightly sketchy - but I think that this also halfs the current, so it would become 3500mah, because it drains both + and - rails from "one" cell instead of two.

There for, I believe that my method is better...but I am ready to be corrected if I am wrong.

At the end of the day, it is your decision.

Gaz

[analog_sa]

Btw the inclusion of the 1.5k 'class A' resistor is very controversial. You should build without it first and then try to include it and listen.

[Verbal]

Volcom, check this thread:
Battery-powered supplies

I'd like to get 60watt is it possible with a LM3875?
i'd like to make this small and "not heavy" lol. Because I want it to fit in my backpack

Depends on how long and how loud you want it to play. But you should be aware that batteries are heavy. +/-24V,7Ah in SLAs weights 10kg+.

but I think that this also halfs the current, so it would become 3500mah, because it drains both + and - rails from "one" cell instead of two.

No, because the "one" is made up from the same number of batteries as the two (i.e. four ), so capacity would still be the same. Don't see the point though, if you're using an even number of batteries why not just take the midpoint.

[VoLCoM]

I went at my local electronics center and i have found 3 type of batteries http://www.master-vox.com

12V 18AH Lead Acid (WP18-12) ---$39.00 CAD
12V 6.5AH PANASONIC ( PA-12V65P ) --- $32.00 CAD
12V 7AH (IM-1270) --- $24.95 CAD

I have to carry them in my backpack.....so it must not be dangerous which one should i choose?
i want the amp to play..at leat 2 hours with a 3875 or 3886