Building the Tiny Giant amp

[frequencycentral]

[Jdansti]

> Am I correct in assuming that the 4A PS should allow for two "pedals" to be added onto the TG?

You should be fine.

[Taylor]

Great build, Rick. 

[Moxienator]

Thanks for all the help guys!

Schematics done, just waiting on the pcb to arrive. Its been a little over a week. Should be here soon.

Sweet build man! That cabinet is awesome!!!

[Rock_on]

Ok thanks!! ^^

I still dont know if we have

138 and 238 i just saw these two when i googled lm338

The shop said their next order would be on june

[Jdansti]

^ BTW, I noticed in an early posting of you're that you're in the Philippines. You might want to contact jogina111 about where he gets his parts since he lives there too.

[Rock_on]

O yeah right.. I forgot about that. Thanks!!

[Rock_on]

I looked at the LM338T datasheet and there I found the schematics but the problem is the transistor values are not specified but the resistor values are specified

[Jdansti]

I looked at the LM338T datasheet and there I found the schematics but the problem is the transistor values are not specified but the resistor values are specified

I'm sorry, but I don't follow what you mean about the "transistor values". The following is an example of how to use the LM338. There are no transitors necessary. This example includes diodes to protect the regulator from capacitor discharges.  


Data Sheet: http://www.ti.com/lit/ds/symlink/lm138.pdf

The TGA schematic shows a similar circuit, but without the diodes and with a fixed resistor instead of a pot since you don't need the regulator's output to be variable.

[Rock_on]

Download the LM338T datasheet

You'll see that there is a page there about the LM338T's inside circuit

Bad english isn't?

[Jdansti]

Do you mean this?





If so, this is an equivalent schematic of what's going on inside of the 338. You have no control over this and you don't need to worry about it. It's there for engineers to understand how the chip operates and to assist them if they want to design circuits that are different from the application examples listed on the data sheet. So unless you need to design something exotic, ignore it!

[Rock_on]

Yah that's it

What im trying to do now is make my own LM338

[Jdansti]

Yikes!!!

Several comments about this (besides yikes!).

1) The schematic of the 338 "guts" may not show everything going on inside. It may be what's called an 'equivalent circuit'.

2) Even if the guts schematic were perfectly accurate, your chances of building to that schematic and having an operating regulator are about ZERO.  I'm not doubting your ability-even the best builders on this forum would have major problems getting something like this to work.  

3. It would be easier to use another regulation method such as a smaller regulator circuit based on transistors, or one based on zener diodes.

Edit:

Seriously, PM jogina111 over in the Philippines and ask him how he provided power for his TGA.

Calling Mark/jogina111: please help us out here!

[Rock_on]

What if i use transformer from an old computer speaker??

220-9v i think the current is 3

Can i use that?? I'll just build my own again..

What ic to use??

[Rock_on]

What if i use transformer from an old computer speaker??

220-9v i think the current is 3

Can i use that?? I'll just build my own again..

What ic to use??

[Jdansti]

Hopefully you're talking about a manufactured power supply and not a raw transformer. If so, that would work. You'd have reduced output volume, but it would still be more than loud enough to irritate your entire family and probably the neighbors.

Here's what the data sheet shows for 9V operation:




BTW. I'm curious-you can buy the TDA7240 locally, but not the LM338?  Correct?

[Rock_on]

Even jogina knows that..

Hmm im talking about a small square with 4 wires

[Rock_on]

Even jogina knows that..

Hmm im talking about a small square with 4 wires

[Moxienator]

Anyone have any exp using the Azabache? I include it in this topic as I'm
Planning on using it in the TG build. I'll be wiring it pre-preamp and using it
As my "channel 2". Any thoughts?

Also, I'm debating on using the Solstice reverb instead of the BYOC reverb2
Any solstice uses out there?

It's really a toss-up between the Azabache and Ube Reamer, as well as
Between the Reverb2 and the Solstice. They all seem to sound good....

[Jdansti]

Even jogina knows that..

Hmm im talking about a small square with 4 wires

If it looks like anything in the picture below, the answer is no.



If you're thinking of making your own power supply connected to the mains power, I gave you my opinion on page 33 when you asked the same question.  http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg906387#msg906387

An Internet forum is not the place for a novice to learn about working with mains voltages.  If making a supply for a guitar amp is worth risking your life, you should seriously think about dropping the guitar and learning drums.