Building the Tiny Giant amp

[mean_dorris]

I had been using a guitar, with similar symptoms, but I got kinda tired of reaching over to strum it all the time 
So now I have a sine wave generator putting through a signal at about -30db
It starts off sounding fine as I go up from 0, then at around 11oclock it starts to get kind of fuzzy, and then at 12oclock it starts to make these quite loud popping sounds that seem to react to my playing. Sometimes they go away when I stop, but other times I have to turn the volume down. I guess it's oscillating or something?

[mean_dorris]

UPDATE:

I was just dicking around with it some more and I wiggled the capacitors near the TDA, the 470uF and the 10uF kind of at the same time and it fixed the problem! I had reflowed them, maybe i damaged them or something. jogina111, that might be a good place to start if you are having the same symptoms as me. so I'll be swapping those out.
thanks for being around, Taylor. I built up an echo base from your pcb last month and it fired up first shot.

EDIT:
jumped the gun, goddamnit. swapped out those caps and it's still happening. i swear i had it going for like 20 seconds! bah

[Cerberus]

Would it be possible to run 2 tg boards in a stereo setup with 1 powersuply and a dual taper volume pot without any problems?

[Taylor]

Would it be possible to run 2 tg boards in a stereo setup with 1 powersuply and a dual taper volume pot without any problems?

Yes, I've done this successfully. Make sure your power supply can handle both boards.

[masterlk]

Hey everyone - finally got my TG going and I am having some of the same issues as just recently mentioned. Clipping badly at around noon and sounding like fuzz and cutting in and out when maxed. Took some numbers and everywhere the schematic shows 11.6v, I am getting 11.35v with a power supply of 16v and 4.5amps. On the schematic it shows the LM338 Vin at 19.5v and my reading is 16.66v. So far are these readings causing any issues that anyone can think of? Further prior to populating the board I measured all the parts and only one came up considerably off, the 470uf cap was actually 370uf, would this cause an issue? Just a thought, could a bad POT cause some of these symtoms? I'm a noob so...go easy on me.

Thanks.

Nick

[Taylor]

Hi Nick, welcome to the forum. The 19.5v is only if that's the voltage of your power supply, so with a 16v supply it's not surprising that you get ~16v there.

I have to admit that I don't know the cause of the cutting out because I have never experienced it. I don't have any place where I can turn it up to maximum - just too loud for the places I can use it. Some amount of distortion is to be expected and could be considered a feature, but cutting out is no good. I will try to reproduce it and see if I can figure out what's up.

[masterlk]

Thanks Tyler. I checked and reflowed my joints and swapped the TL072 and still basically the same, maybe a bit better. After playing the amp again, I would recharacterize my previous assesment, not really clipping "badly" at noon but is clipping a bit. Here's something else I noticed, when the volume is all the way up, that is when it kind of cuts in and out and fuzz type sound. It does the same when hitting the front end really hard with a Madbean Sunking. So, when I pull the volume back just short of full and dial the Sunking back as well, I basically get the same amount of volume but with no cutting out or fuzz. Seems to be ok, not sure what it is about the total cranked position that it doesn't like.

[jogina111]

what  do you use for a  power supply masterlk?

[Taylor]

Some clipping is to be expected, and several people have mentioned how much they are surprised that it clips nicely, unlike many solid state amps.

The preamp is a plain old opamp so there is nothing to be gained by slamming the front end with a booster or whatever. A tube will break up in an interesting way when you do this; an opamp won't.

[masterlk]

For this amp I am using  a 16v 4.5amp laptop ps.



Posted by: jogina111 
Insert Quote
what  do you use for a  power supply masterlk?

[masterlk]

Ok and thanks. My appologies for calling you Tyler in my previous post, sorry. I am going to box this thing up and call it good!



Some clipping is to be expected, and several people have mentioned how much they are surprised that it clips nicely, unlike many solid state amps.

The preamp is a plain old opamp so there is nothing to be gained by slamming the front end with a booster or whatever. A tube will break up in an interesting way when you do this; an opamp won't.

[Puguglybonehead]

Some clipping is to be expected, and several people have mentioned how much they are surprised that it clips nicely, unlike many solid state amps.

The preamp is a plain old opamp so there is nothing to be gained by slamming the front end with a booster or whatever. A tube will break up in an interesting way when you do this; an opamp won't.

I'm planning on using one (or maybe two, with switching) of the ROG circuits as a preamp with this. Was thinking either the Professor Tweed or the Azabache, along with the Matchbox for channel 2. Should I therefore leave out the preamp stage that's in the TG circuit, or am I OK to just add on the ROG circuits in front of the whole thing?

[Taylor]

Either will work, so if you just want the simple path I'd leave the TG preamp in and just add your new preamp in front as if it's a pedal.

[jogina111]

I've got an old power supply from an old PC and Im planning to hack the 12v transformer plus the regulator to make a power supply for the tg...but when I checked the labels, it says 12v-~15amp. 15 AMPERES! Can the tg take that much current? im kinda afraid to just make a PS so I asked just to be sure.

[Taylor]

Electronics will only draw the amount of current they need, so it will draw only an amp or so regardless of how much the supply is capable of handling. So you'll be just fine.

BUT. The rules of helping on forums require that I tell you that working with mains power is dangerous, and if you don't know how to do it safely, you shouldn't be doing it in the first place. If you have any uncertainty about what you're, that's a sign you're not ready to work with high voltages and you should get a friend who knows to help.

Sorry to be disclaimer-ish but I don't want anybody to get hurt, and more importantly, I don't want to get sued by your family. 

[Jdansti]

Why not just tap the 12v from the normal output connector on the computer PS instead of canibalizing it?  It might be bulkier, but you wouldn't have to put it in another enclosure and it would be much less likely to be a safety hazard.

[jogina111]

thanks Taylor and John. Im not very insistent to try hacking the psu now... but my knowledgeable friends might do know how to manipulate electricity so I'm asking them for help.

[jakobmagnusson]

Hi,
Started to solder my Tiny Giant and realised I'm a real noob on this

Some holes on the PCB doesn't seem to have any component that should be soldered to them, I marked them with red circle in below picture. Should I do something else with them?

http://img195.imageshack.us/img195/290/tinygiantpcb.jpg
Thanks,
Jakob

[slacker]

You don't do anything with those holes. The board is double sided, meaning it has traces connecting components on both sides of the board. Those holes are called vias and join traces on the front to traces on the back.

[garcho]

A friend of mine who builds amplifiers answered a dumb question I had with, "when you're not sure if oranges and soy sauce will taste good together, you should try it, and see what happens." He left out part B for dramatic effect, but he was implying that dealing with power supplies and mains is not something you should "try".