Lm3886 Bpa

[jaudio]

Macboy:

You explain things much better than I.

 

[macboy]

What is the (E24) ?

Did you ever notice how resistors (and capacitors and inductors) only come in certain values? E24 is a standardized set of values for these components. It defines a set of 24 values per decade. This webpage has a good explaination. Typically, cheap 5% carbon resistors are available in E24 values. More expensive 1% resistors are usually avaiable in E96 values.

 

[jaudio]

Yes I've noticed. Now I know why

I should be more carefully. I pull 4k and 48k out of the air as an example.




Thanks Macboy

 

[thomasfw]

Dear all,

Thank you so much for you help !

Please comment the value of "C" and "RL" !!
(Six LM3886 parallel together)


Thomas

 

[thomasfw]

Dear all,

Thank you so much for you help !

Please comment the value of "C" and "RL" !!
(Six LM3886 parallel together)


Thomas

 

[thomasfw]

Dear Macboy and all,

I found a kit from Tai Wan use another way to adjust the
DC offset.
Please see the attachment !

Thomas

P.S. Regarding to my last post, I plan to use "DRV134".
Is it affect the calculation for the "C" & "RL" ?

 

[jaudio]

"c"=159155/(4k*10hz)=3.97uf for example

RL depends of the source out impedance. Most amp are bewteen 10k and 100k,these values work pretty good

What is the benefit of adding more parts?

 

[jaudio]

C determines low frequecy cutoff

If you want a cutoff of lets say 20hz and say your input resistor is 4k then 159155/(4k*20).

To ensure that low frequecy is not cutoff above 20hz,you would divide 20hz by 4.

So it will be 159155/(4000*(20/4))=7.9578uf or 8uf

 

[thomasfw]

http://www.shine7.com/audio/jeff.htm


There are lots of Photo !

Thomas

 

[jaudio]

Thomas is this your first project?

 

[thomasfw]

1st in chip amp, but no for audio.
Buy the way I found that the 3.3uf is very expensive (wima)!!!
I plan to use 12 pcs per channel (6 paralell and then bridge).
Is any alt. way ?


Thomas

 

[jaudio]

Dear Macboy and all,

I found a kit from Tai Wan use another way to adjust the
DC offset.
Please see the attachment !

Thomas

What was the claimed benefit by using this offset circuit?

Try Ero capacitors

 

[thomasfw]

Try Ero capacitors

I don't know about this cap.

In Hong Kong most common is "wima, rel-cap, auricap, Elna etc.,"

Can you give me a link, please !

Thomas

 

[jaudio]

Surplus dealers may here them. I have seen a ero dealer in hong kong. I will search when I get home.

Are you going to use a pcb or use point to point? If you are going point to point then wire each chip amp separtely. If might be a good Idea to wiring at least 20 chips and match 12 as close as possible(match dc offset before adjusting trimmers). Another benefit of wiring separte amp is that you can pull the damaged chipamp module out.

Try to keep it simple.

 

[thomasfw]

Dear Jaudio,

1st in chip amp, but no for audio.

Should be "1st time in Chip Amp but not for audio"

I have built many Tube Amp.
By the way, can you tell me how heat (temp) the "Bpa" is when it is full power ?


Thomas

 

[jaudio]

It depends on the size of the heatsink. I have four chips on a 15.5" x 3.5" x 1.75" heatsink. The heatsink gets just alittle warm idle. you will need a larger heatsink,if you use 6 chips. You have built tube amps,so you should have no problem going point to point.

Have you used the 6922 at low voltage? I may need help.

 

[Billy0810]

Jaudio:
I want to build a BPA200 base on your advices too. (2Paralleled and 2 bridged per channel)Is this schematic OK?(Power supply and the mute resistors are not shown)

 

[jaudio]

Sorry it will not work.

You can not make adjustment on the +signal that way

The lower half has the gain of about 1,so the halve dont match

try this

 

[jaudio]

You can go to www.national.com to get application note AN-1192 look at figure 7.0 page15. Schematic is like yours and you can see your mistakes


Good luck

 

[jaudio]

Jaudio:
I want to build a BPA200 base on your advices too. (2Paralleled and 2 bridged per channel)Is this schematic OK?(Power supply and the mute resistors are not shown)

I use 24k bewteen pin 8 and - powersupply. Do a search on this site for powersupply schematics

You need least 40000uf capacitance and a transformer with dual 24volt and no less than 400va.

www.tnt-audio.com/clinica/ssps1_e.html
www.linkwitzlab.com/images/graphics/3886pwr.gif
www.sero-distortion.com/techno/powersupply/powersi.htm
www.sound.westhost.com/power-supplies.htm