lm1875 gainclone lack speed

[tonitze]

Has anybody any idea why my lm1875 gainclone lack the speed compared to the tda7375? Could it be the 2x12vac 120va trafo and 8x byv28 sharing for both channel? The sound is indeed quite good but the music tend to slow down. I follow exactly Brian Gt lm3875 based gainclonce components value on my lm1875 gainclone. Is it ok to apply the value to lm1875?

Toni.

 

[peranders]

It can be something about available power. You maybe need a more powerful amp with more current and more speaker control?

 

[tonitze]

Thanks Peranders,

may be I should upgrade the trafo with higher rating like 2x18 300va perhaps?

Toni.

 

[li_gangyi]

12 volt per rail is tethering on the edge~!! I suppose you mean 12VAC...yeah might wanna go higher something in the region of 18-22VAC will do pretty well for you...I use a 22V dual trafo with 4.5A of current...seems to work well for 2 channels...

 

[tonitze]

Thanks anyway. I stop listening to the lm1875. Back to the tda7375 which had more speed. I'll try with bigger trafo the next time. Maybe it should solve the problem.

Toni.

 

[CRFX]

I'v been using a lm1875 for a while and haven't nocticed any problems like that, and im running 8 channels on a 12V 3A transformer. Althogh I never turn them up high enogh to max the transformer.

 

[tonitze]

Oops..! Then what might had gone wrong with mine? Maybe the component value being used thru out, I follow exactly the value use for lm3875 by Brian GT and Peter Daniel. What about BYV28, are these good for GAINCLONE?

TONI

 

[philb]

which pcb

i'm building am amp using the lm1875, and wanted to know which pcb to use. The National datasheet gives two pcb's one for plit supply and one for single, what does single and split mean, and which one do i use for 5 channels?

thanks

 

[li_gangyi]

single supply applications require only one side of a supply...BUT u have to use at least 12V if u're aiming for +/-12V originally...split supply means u use a centre tap rafo or a dual sec trafo and produce +/- voltages...a spilt supply system will require slightly less parts...

 

[philb]

That makes a lot of sense

Thank you very much li_gangyi, that really makes sense and i can't beleive that i did not figure it out myself. Thanks for the help now it's time to go make some pcb's. I'd like to post some pics of thm when they are finished.

 

[philb]

stage 1

Here is the PCB ready to be dipped in ferric chloride.

 

[philb]

stage 2

please note that i don't have a digital camera and i am actually scanning the pcb. That said here it is all etched.

 

[carlmart]

Next time I would advise you to use a different technique for your prototypes, instead of a felt pen.

Use translucid tape to cover all the copper, then carbon copy your pcb design onto it. Then use a razor blade or surgeon knife to cut the tape away following your pcb design and exposing the copper.

Then dip it in the acid.

It's quite easy and gets good looking results. It's good for just a few boards, or it will get tiresome.


Carlos

 

[GringoAudio]

no pcb point-to-point

It ain't really a gainclone with a PCB. Try soldering directly to the chip legs. Its easy and follows the Gaincard philosophy of shortest possible signal paths...(not sure I believe that though). But anyway the making of a PCB is a roadblock you do not need with the very few components required in a minimized gainclone. Just solder!
Greg

 

[philb]

actually i did cut the traces out with an exacto. But then just colored inside the lines. When you say to use tape do you mean leave it on while in the ferric chloride? If that works with the tape on it will be a huge timesaver. Also my pcb's are mirrored, so i must surface mount the components, not a big deal. Thanks for the help.

 

[philb]

it works!!!

It works, it plays and it's my first amp. It buzzes a little but there is so much info on how to stop that in the forums that it should be a simple fix.

 

[Igla]

TDA7375 help

HI !
I would need a little help with TDA7375 chip.I plan to build an amp.
I have the chip and all the parts and the schematic is very simple.
I just dont understan, what to do with stand-by pin.I dont need stand-by function.Can I just leave the pin unconected?
I have read the datasheet but I don't understand if there should be some voltage on that pin to disable stand-by mode or is it just the opposite-apply voltage to enable stand-by function.
Any help would be welcome.
By.
Igla