Building the Tiny Giant amp

[Taylor]

This is my guitar amp.  Preamp, Overdrive, Reverb is my design.  Power by Taylor

Wow! I want one.   Fantastic work.

[nowheredog]

Well, Job is done, finally I used a 19v 6a PS, and seems work great (the sound is pretty amazing and very natural). Now the bad news. The thing is really humming. First of all I made a mistake mounting the caps and one of the 22uf I put inverted, so it was a nightmare to desolding (I used a pump) and I think I broke one of the pads outside. Somebody can give me the voltage (the cap is the one is closed to the pin 1 of the tda). I want to check this to be sure it's not broken and is the possible humming problem. So for your convenience I describe all the setup. 3 wire PS. Aluminium case, isolated jack for speaker, non isolated jack for the input. And the negative is grounded to the box in some point or another.

[nowheredog]

I´m getting 5,36v aprox in both of them. So I think they´re working

[nowheredog]

Problem solved. Like the most of people who had the same problem it was the 3 wire plug. And why this if I saw that I have a 3 wire one?. Because the third vire it was disconnected!!!! Didn't remember I made by myself long time ago because the cable came with another country plug, so I leaved the ground unplugged. Dumbass.

[nowheredog]

I want to go a little far and put a 7809 regulator to feed my pedalboard. But I don´t want to get the current from the pcb, instead, direct from the input, so doesn´t matter if the amp is turned on or off. My question is, it had to be isolated too to avoid ground? or can be directly attached to the box ?(disipation can be better I think). Can I expect some problems in that way? Thanks.

[phector2004]

Mine isn't isolated, as the heatsink on 78XX regulators is tied to ground. It'll work fine bolted onto your enclosure, assuming all 7809 chips are made the same way

[Skruffyhound]

Doesn't that get pretty warm dropping 6 volts (assuming 15 volt supply)?

[phector2004]

Nope.

I'm running a boogie, so the current draw is small. I don't know what it is exactly, but assuming 50mA, that's 1/4W?

Then again, I've also got everything mounted in a C-sized enclosure.

I'm guessing it's not a good idea to run a dozen pedals off your TG supply, though. Especially not digital ones!

[Skruffyhound]

Right, if it's not drawing much then that makes sense. I was under the impression that people were powering their pedal boards off the extra amps. Perhaps they use a different method to drop the voltage.

[nowheredog]

Well here is mine. How you can see I inserted a 7809 in a small pcb with two filter caps, direct to the main supply so I can have the pedalboard feed-ed independently if the amp is turned on or off. The main supply is 6A so I don't expect current problems.  I trimmed the back case to be sure is not  in conflict with the 12v regulator. I want to put a one knob tone control like Paul did. And the next, is time to paint the whole thing. Best regards guys and thanks Taylor for this great project.

[phector2004]

Your power supply seems to be good for the job, as I doubt you'll need anything over 1A for your board. If, however, you've got the TG cranked and you're feeding a lot of high-current-drawing pedals, it will get hot. I don't know exactly how hot, maybe just too much to touch, maybe enough to burn the tolex on your cab. It might have been wiser to mount your regulator board farther away from the TG to dissipate the heat over a larger area.

In any case, everything should be fine, just keep the heat issue in mind!

Enjoy your new amp  

[sgmezei]

Okay, I need to order two power supplies for two separate tiny giants.
I understand the specs I need but there are SO many on ebay and amazon.
15-20V DC with at least 4 amps

Any recommendations for finding a power supply? Anything from our usual DIY vendors?
Maybe a switchable power supply for 15 to 20volts? (I have heard these are usually cheap garbage though)

Thanks for the help.

Scott

[Taylor]

I would search for 15vdc laptop supply, then filter buy it now, priced low to high, and grab the first one that's an adequate amp rating. You can probably get them for $10 each.

I would avoid switchable voltage ones. That won't do any good for this amp because of the regulator, and it might make for weird issues.

[sgmezei]

Thanks Taylor,
Awesome, speedy reply.

[musicisphysics]

Would there be a problem in just leaving out the 10k pot and running the signal straight to the TDA7240A from the TL072 through a cap?

[Taylor]

No, no problems other than that it will be quite loud if you don't have a volume control elsewhere.

The board already has a cap before and after the pot so you could just jumper the pot pads. Make sure you know which two to jumper though. You could also leave one of those caps out, but honestly it's easier to leave them in IMO.

[myramyd]

Hello Taylor,

(The bad luck continues!) My TG suddenly stopped working the other day. It was working fine--I was testing my guitar wiring and it was on, then I unplugged it from power, then plugged it back in 10 minutes later and it "thumps" the speaker when I plug in the power but no sound.

All the voltages still check out (jack, IC, etc.). The only thing I notice is that now the sleeve lug on the speaker jack has continuity with ground. Tracing along the schematic, I get ground continuity all the way along the path of that wire--Pin 7 of the chip, both sides of the 2.2R resistor, and both sides of the 220n cap. Don't know if that is normal or not but, I didn't get ground signal on that lug before.

Any ideas? Thanks.

J

[Taylor]

What kind of jack is it? Any chance the jack is connecting to ground?

[myramyd]

It's a plastic "Marshall" type speaker jack. It was working fine for a few months then it did this all the sudden. All I did was unplug it, then plug it back in 10 minutes later.

J

[Taylor]

Hmm. Are the heat sink tabs of the ICs still discontinuous to ground?