Building the Tiny Giant amp

[potul]

Some chips do something like that when over-loaded or over-heated.

Use your finger. (If you can't type afterward, it's too hot.)

Hi Again,

I just installed a heatsink I took from an old computer, and now things are much better. I can now fulfill PRR rule (I can hold my finger on it, and continue playing afterwards), even at max volume. And the "farting" is gone.

Thanks for your help!

I still have to work on some dampening, because being the container a metallic one, there is a lot of rattle that can be mistaken as distortion, but I still can hear some distortion (maybe from speaker) at moderate levels. I will keep on trying.

Mat

[Rock_on]

Sorry-I guess I screwed up again. When you said you wanted to make your own regulated power supply and asked for help doing that, and you said you couldn't find a substitute for the 338T (which the design calls for), it took this to mean that you couldn't get a 338T and were trying to figure out how to make a supply that would make the amp work without the 338T. That's why I asked you the questions about what kind of supplies you had to work with. So I'm a little confused by your requests and comments, and I don't mean that in an insulting way.  You're not my wife are you???

Either way, I'll step aside and let y'all figure this one out.

Ok to clear this up

I just answered your question what would i do if i had lm338T

What kind of supply?? As long it's compatible with the TGA (tiny giant amp) if possible the best voltage for it

Thanks.. Is it clear now? Just tell me

[Jdansti]

>Thanks.. Is it clear now? Just tell me

Yes

>What kind of supply?? As long it's compatible with the TGA (tiny giant amp)...

It's designed for a laptop power supply.

>...if possible the best voltage for it

15-20 volts DC (closer to 15 is better due to less heat dissipation than higher voltages).
4 amperes or more.

[potul]

Hi Guys,

I was wondering..... How important is the value of the pot being 10k?
I have now in my TG a linear 10k pot instead of a log one. And of course.... I can only use a portion of its range, most of the change happens at the beginning of the knob rotation.
If I taper it to be more "log", with a 2k resistor, I will have a total resistance of 1.7k.  Will this have any side effect in the circuit?

Mat

[Rock_on]

Now im asking for a regulated (15-20 volts, it's up to you what you think is the best for that range) power supply circuit for the TGA..

I dont want to buy a supply, it's better to make one..

So can you design one please? I cant make one that's why..

It's the LM338T and/or a regulated power supply missing.

[potul]

Hi Rock on

sorry for stepping in, but I don't get the point of your question. If I understand right, you can't source easily an LM338T, and then you ask how to build your own power supply because of this. Are you aware that in order to build a regulated 12V power supply, you will probably need an LM338T or similar? So... this will not solve your problem, you should concentrate on finding a voltage regulator that can handle the amount of current needed. (like the one I posted some days ago)

Let me explain you how this works:

-LM338T is a voltage regulator. It gets fed with a voltage that can range from 15 to 20 (or more), and delivers 12V (in this circuit. It can be configured for another voltage if needed).
-The circuit of the TG is designed so that this regulation is included, so you just need to find a laptop or similar power supply, and use it.
-If you have already a power supply that gives 12V, capable of delivering 4A, you can skip the LM338T and feed directly the 12V
-If you have to build a power supply,... most probably you will need an LM338T or similar anyway, so I don't see the point in doing this.


Mat

[potul]

(duplicated)

[Jdansti]

>I dont want to buy a supply, it's better to make one..

No, when it comes to power supplies and dealing with mains voltages, it's better to buy one.  Mains voltages can kill, so although many of us on the forum can answer your question, we won't. It's not that we don't like people who ask how to build power supplies, it's because we don't want them to hurt themselves.

I know how to build power supplies and I've built them. I have some formal electronics training (though I'm not an EE) and know the requirements and hazards. Even so, I normally use a cheap unregulated wall wart that steps the voltage down to a safer level and build off of that. For example, if I need 12VDC, and I have an 18VAC wall wart handy or I find one cheap, then I'll make a circuit to convert it to regulated 12VDC. By doing it this way, I let the manufacturer of the wall wart do the hard part of making sure part of the circuit in contact with the mains voltage is safe. All I have to do is play with the lower voltage side.

BTW, as Potul said, a regulated power supply needs some type of regulator regardless of whether you build the whole thing from scratch or work off of an unregulated wall wart.

Since you asked for a circuit, here's what you'd do. I haven't had a chance to look up the regulator you'd need.

[Rock_on]

Ok sorry guys for the inconvenience

I have here 12v dc supply i got from our old vonage..

Its current is not enough and it's not 15 and also i dont know if it's regulated

Can you help me with this??

And if 12v is not enough i assume that i'll do bipolar right??

[potul]

If it's 12v, I would try to feed it directly to the TG after the regulator and see how it performs in terms of noise.

Unfortunately, it's not an easy task to regulate 12v to 12v, you always need some margin. But there are chances that the 12v PS you have works ok as is.

Mat

[Jdansti]

If you decide to go with 12V, here's a way to do it: http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg897715#msg897715

Be careful with your Vonage supply. Most 12V models on the web are 1.5A. It might get a little warm!!!   it might become damaged too. It might have an internal fuse or thermal shutoff, but ready to pull the plug. The current draw will increase as the amp's output volume increases.

[Moxienator]

Hey guys! New here, but been lurking for a while. I'm building the TG,
and was hoping to add a reverb stomp box from BYOC into it. My question
Is in regards to the byoc reverb's negative ground. Do I connect the
- pad on the PCB to the ground on the TG? Will this work or make
Some expensive garbage? The 11.6 out from the TG will be stepped
Down to 5v for the Belton reverb module. I'm planning on using the
max 5053 ( i think its that regulator) which is a step up from the one in
The byoc kit, along with a heat sink on it. My second question: even though
I'm drawing power for the 5v regulator, is it conceivable to power a second
"Stompbox" off the 11.6v out? Like a fuzz face or blues breaker? I'm
Powering this 1-12 combo ("the M.OXIE-Verb 112") with a 16v 4a PS.
Any help would be much appreciated!

[Jdansti]

Welcome to the forum!  

What is the voltage requirement for the reverb?  Assuming it's 9V, if it were me, I would install a small regulator circuit using a 7809 to bring the laptop power supply down to 9V for the reverb. You could incorporate this on the reverb board the way that the TG has its 12V regulator on the board, or you could make a little board for it.

To answer your question about the ground, you should tie all of the grounds for all of the boards to one point (assuming they're all negative ground) regardless of how you do the power.

Here's an example:



Edit:  Bypass and power switches omitted from drawing.

[potul]

If I'm not mistaken, taking a look at the schematic of the BYOC reverb looks like you can power it directly from 12v as it is. Why do you want to change the regulator?

Mat

[Jdansti]

^ Good point.  I got off track there about powering a generic stompbox that requires 9V.

The TG board has a 12V take off point so you can power other 12V devices. The grounds should all be connected.  As you mention, there's no need to replace the LM338T regulator as it's output current is rated at 5A.

[Moxienator]

Wow,Thanks Guys!

@Jdansti- The requirement for the Belton reverb module is 5v.

@Taylor- The Regulator id be replacing isn't on the TG, its on the PCB for the reverb. Its normally the MC78L05, which may need a bigger heatsink than usual, as in pedal form, the stepdown is from 9v to 5v. I'd be replacing it with the MAX5035, which should easily handle the 12v - 5v with the heatsink available at Small Bear.

@potul- Just want to make sure heat will not be an issue.

I'm placing this mess in a small amp chassis which is much thinner (.04" aluminum) than the typical "stompbox" you guys have been using in lieu of heatsinks, and thus the concern for heat. Maybe i'm worrying over nothing and it'll be fine. But OTOH, Reality has a way of intruding on Designs....

@Jdansti- Thanks for the Ground info! Got confused while elbow-deep in schematics. Yes, the Reverb PCB is Neg GND. Nice mock-up BTW!

Last night after polishing up the schematics i've drawn up, I realized there is a lot of room in the enclosure im using and decided to put in a second effect into it, running off the 12v also. I don't think there'll be an issue as the power supply will put out 4a of current. A simple Dist/OD/Fuzz pedal is what i'm shooting for. Time to cook up some distortion.....

[Jdansti]

>@Jdansti- The requirement for the Belton reverb module is 5v.

Right. My experience has been that effects that use single PT2399s or the Belton bricks are powered by something higher than 5V, and there's a 7805 or 78L05 onboard to supply 5V to the PT2399 or the brick. I think we're saying the same thing.

>@Taylor- The Regulator id be replacing isn't on the TG, its on the PCB for the reverb. Its normally the MC78L05, which may need a bigger heatsink than usual, as in pedal form, the stepdown is from 9v to 5v. I'd be replacing it with the MAX5035, which should easily handle the 12v - 5v with the heatsink available at Small Bear.

If I may chime in on this one, when I built the Solstice reverb (two PT-2399s), I had problems with the 78L05 and swapped it for a 7805. I found that the 7805 had no problems with: (1) 9V input, (2) powering two PT-2399s, and (3) no heat sink. I think it would have worked with a 12V input because the current draw was so small. I suspect that the BTDR-1 in the BYOC reverb, which has a max current of 100ma, would work fine with a 7805, 9-12V input, and no heat sink. If you did need a heat sink for the 7805, it could be a very smallish DIY custom piece of metal (some small cut up squares from a soft drink can).

[Rock_on]

Hey guys i foud LM138 and LM238

138 i think can give high current output for a short time only how about the 238??

And btw

Can i use transistor to amplify my vonage PS which has 1.5A if 138 and 238 wont work??

And also use a transistor to regulate??

[Jdansti]

>138 i think can give high current output for a short time only how about the 238??


LM138/238 Icl = 5A max
PS =4A min

It's cutting it a little close, but just make sure you have a good heat sink on the reg.  So you have access to LM138 and LM238, but not LM338?  


>Can i use transistor to amplify my vonage PS which has 1.5A if 138 and 238 wont work??

No. I think this would defy the laws of physics.  Ask everyone you know if they have a PS that says 12VDC/4A or greater. Especially laptop supplies. If the supply is between 12 and 15VDC and >/= 4A you can skip the regulator. If you get one >15A, you should use the regulator.

>And also use a transistor to regulate??

Yes. This usually involves a transistor or two, zener diodes, and a bunch of other components. See: https://www.google.com/search?q=transistor+voltage+regulator+schematic&client=safari&hl=en&tbm=isch&tbo=u&source=univ&sa=X&ei=EIhyUaeAJamO2QXwzIBo&ved=0CDAQsAQ&biw=480&bih=229

[Moxienator]

> I think we're saying the same thing.

It appears we are.

>problems with the 78L05 and swapped it for a 7805.
>heat sink for the 7805, it could be a very smallish DIY custom piece of metal (some small cut up squares from a soft drink can).

Thanks Jdansti! I will try that. I may actual build the solstice instead of the BYOC kit, I haven't really decided yet. Still working out the kinks.
Am I correct in assuming that the 4A PS should allow for two "pedals" to be added onto the TG?

Input -> Switch 1 -> TG Preamp -> "Fenderish" Tonestack -> Switch 2 -> TG Poweramp -> Output
               I    I                                                                          I   I
         "Ube Reamer"                                                               "Reverb"