Building the Tiny Giant amp

[Hupla]

How could I test the power supply for this? Is there a ball park figure I should be leaning towards for a power supply? Also my 9v regulator max's at 1 amp so I think that should be enough as I wouldn't have many on at once. At most I would be using one digital pedal?

If your 9V regulator can handle 1 amp (e.g. like an LM7809), and is in a TO220 package, then it probably wouldn't even break a sweat - even with a fairly loaded pedal board.  With one digital pedal, and a handfull of analog pedals, you probably don't need more than 200ma for all the pedals together.  I doubt that you would even need a heatsink for the add-on regulator.

Taylor was pretty conservative in specifying the power supply for the TG.  If your laptop power supply handles 3.5+ amps (as marked on the label), there should be plenty for all.  Seems like the TG draws about 1 amp when it starts up, then settles down to a couple hundred ma at moderate volume levels.

Ah that's great news. Thank's for all your help. Just one more question, would it be safe enough to just attach regulator to regulator or should I put some caps either side of my 9v regulator?

[waltk]

Just one more question, would it be safe enough to just attach regulator to regulator or should I put some caps either side of my 9v regulator?

Is this a standard linear regulator?  Does the datasheet call for them?  Can't hurt to have them.  The smallish cap on the output side is usually there to improve stability and transient response.  The one on the input side is probably not necessary.

[phector2004]

What I ended up doing is setting up a 7809 in parallel to the TG. Works like a charm

The heatsink tab on 78xx regulators is connected to ground, so I used a standoff to mount it to the enclosure. Not sure if this could affect overheating of the amp at all, but my reasoning was that the added heat loss won't be shared with the TG's regulator; putting the 7809 at a distant site will dump the full amount at a "colder" spot.

My 1590C takes care of the heat anyways, but it's good practice, I guess?

Is it bad that I used a 1u polarized electro on the output, though? I doubt it's doing much seeing how my preamp's already got a 220uF, V+ to ground

[YouAre]

Does this look like a viable option for a power supply?

http://www.amazon.com/PA3048U-1ACA-PA3282U-1ACA-PA3282U-2ACA-pa3260u-1aca-Satellite/dp/B001MQ35EY/ref=sr_1_5?ie=UTF8&qid=1316622461&sr=8-5

[h8mtv]

I am working on mine. Any reason I can't just add heat sinks and not ground either of them? I am using a roomy enclosure.

Any easy way to add an indicator light or use a lit toggle?

[Taylor]

You can use heat sinks that aren't connected to anything, and then you don't need the spacers/bushings.

For an indicator light, just use an extra pole of your switch to power an LED with a series current limiting resistor.

[h8mtv]

Sweet, mine is a 15a 15v supply. Any suggestions on what value resistor to use for drop down to the LED? I am going to build a floor monitor rig with pedalboard combo thing.

[waltk]

You calculate the resistor value with this formula: R = (V_S - V_L)/I
where
R is the the resistance in ohms
V_S is the source voltage
V_L is the voltage drop across the LED
I is the current in amps that you want to light the LED

So if your source voltage is 15, and it's an ordinary red LED with a voltage drop of about 2V, and you want it fairly bright (20 ma current):

(15-2)/.02 = 650 ohms

I usually go with a bigger resistance because I don't like the LEDs at full brightness.  Other types (colors) of LEDs can have a different votage drop.  Google for "LED resistor calculator", and you'll find a zillion sites using this simple LED resistor formula.  Some have calculators for making whole networks of LEDs in serial and parallel.

[h8mtv]

Thank you.

[ozboomer]

'lo all...

Have been lurking on this for a while... but with a few years of guitar mods under my belt and a couple of JFET Boosters and Ruby amps built, I think I'm ready to give the TG a go(!)

Just a couple of questions, please:-

1. From exploring the web sites, I find the TDA7240A is an obsolete component (so it says at Mouser, for example).  I also can't find anyone locally who carries them (Australia).  Any suggestions on what can be done to substitute another component in the design? (although, for the initial build, I fully intend to buy a kit)

2. A couple of people have used a Big Muff Pedal (BMP) tone stack in the 'middle' of the design to give some tone control.  Can I ask what values of components did you use in the BMP tone control when used in the TG?  Did you actually work out the losses, etc and/or use something like the Duncan Tone Stack Calculator (see http://www.duncanamps.com/tsc/) to design the response or did you just 'cut'n'paste' the original BMP design verbatim?

Many thanks for any forthcoming info...

[PRR]

> the TDA7240A is an obsolete component

If you have a contract with Banjo World to deliver 100,000 units within 3 weeks, and don't have parts in hand, you do NOT want to rely on any "end of production" or "obsolete" parts.

If you are just building one or a few units, if you can find some stock, if they actually get delivered, who cares if it is "obsolete"?

Actually I cared. About 1980 I designed for LM377 which was readily available. So available that I abused the specifications (35V on a "27V" chip). In 1990 the chip quit, but I had an extra. About 1999 it quit again, and LM377 was replaced by 377 with more letters, and that new chip was already "lifetime buy". I bought two, the first was still working when I left in 2010, and the extra is sitting inside the chassis. So it should be good until 2020, forty years after design/build. And that was an exceptionally bad design (I was young, and broke, thus reckless); chips well-used (like Taylor's plan) probably last 30-100 years each (not 4 in 40 years).

[Skruffyhound]

TDA7240A is an obsolete component

If you are in the States look here:
http://www.packetradio.com/catalog/index.php?main_page=product_info&products_id=1003

If you are in Europe like me I suggest Futurlec, who have both required chips for the time being. Post to The EU from the above link was 25 dollars on four 1 dollar chips.

Good Luck

Edit: I see now you are in Oz, Futurlec it is then, they ship from Thailand. The chip has only just been obsoleted so there will be some stock around, but you better get buying if you want a production run out of it.

[Spidermonkey]

I'm having trouble with the TDA7240 and grounding. On the directions, you say to make sure that the heatsink tab on the chip is not connected to ground. But on the datasheet, it says that pin 4 is connected to the heatsink tab, and on my board the hole for pin 4 is connected to ground. Doesn't this mean that the heatsink tab is connected to ground anyway? Or does it mean that I have a solder bridge or short or something?
Edit: I'm an idiot   Could anyone with a working amp post some voltages for the 338, Tl074 etc?
Thanks!

[nowheredog]

Hey Guys, the kit arrived and looks great, but I'm waiting for the PS as well. I'm asking, is there's a way to put an aux input to play with a CD or mp3 player?Thanks

[arma61]

Hi guys!!

I have ? for you all, I've built my TGA with a CondorCab Simulator (from ROG) inside (switchable), it sounds great. I've played a little bit with it and looks like it sounds great with my, newly built, EasyDrive, and hopefully is going to sound even better with the OneChipChorus... So here comes my question .....  say I want these last two effects to be build inside the TGA box and have an outside box with two switches and LEDs  for the effects... you know just like some Fender Amp!
how would you connect and switch those inside the TGA box, may I just run a cable (say 3m, 9ft) and connect the 3PDTs in the external box like they were inside a "normal" fx..... hmm...... I don't think so..... cable lenght capacitance and whatelse!! or do I  need a relais switching setup.

Thx for your help !

Ciao

Edit: I've some DPDT relais, are they going to work with the Millenium Bypass setup ?

[David]

It is with great sadness and disappointment that I report the death of my Tiny Giant, a faithful companion on my pedalboard for the past six months.  The cause of death appears to be an intermittent short at the point where I had soldered a Boss connector to the laptop power supply I used.  There was a spot I missed applying electrical tape to.  The amp died at practice on Wednesday.  As it supplied power to my pedalboard, it took my pedals too.

The pedals, thankfully, survived.  The amp did not.   

Let this be a cautionary tale.

[Skruffyhound]

Sad 

[nowheredog]

I read carefully about the specs of construction, and some of the threads about the  current capability, and I searched in the datasheet of the chip but I don't founded nothing about that. So why this specs?, it's something about trial error?, I have a power supply of 15v and 1,5 Amp, and I want to use a 8ohm speaker. Any advice?

[wakeuptone]

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

[PRR]

> 15v and 1,5 Amp, and I want to use a 8ohm speaker.

Should be OK.

For this amp (bridged-amps generally):

Multiply speaker impedance by 1.5. 8*1.5 is 12 ohms.

Divide 12 ohms inTO the supply voltage. Actually the internal regulated voltage, but it is safer to take the nominal external voltage. 15V/12= 1.25 Amperes current draw at full output.

This is less than the rated 1.5V of your supply. It sure looks worth a try.