Building the Tiny Giant amp

[bigandtall]

I would try to add a line in after the buffer with resistors for mixing.

Does anyone have more info on how to do this or a link? I"d love to know. Working on a project myself right now.

[slacker]

Have a look at the post by PRR on page 6 of this thread.

[Taylor]

The TG and kit are back in stock. I've also totally redone the (innards of) the MusicPCB website so hopefully everything will work more smoothly now. Please let me know if you have any trouble with the new site.

[bigandtall]

I just ordered a cab for this and am putting it together soon. I have an old 20v 3.25A laptop power chord (http://shop.lenovo.com/us/en/itemdetails/40Y7696/460/FB655FA7A2834E04AED9731463CD174E). Is that okay to use or too much?

[Taylor]

Power-wise that should be fine, though I believe some people had noise problems when using a supply with no ground prong on the AC side. Just something to watch for.

[bigandtall]

Good to know!

Any current deals or "ideal" power cords out there that I should know about since the last postings on the subject?

[smurfedelic smurfberry]

The TG and kit are back in stock. I've also totally redone the (innards of) the MusicPCB website so hopefully everything will work more smoothly now. Please let me know if you have any trouble with the new site.

yay! Ordered today.

While my old one lived (i killed it while trying to "fix" things) I found that it wasn't too friendly with pedals i tried. Has this been discussed?  Are there any ideas on how to adress this with modifications.. Well, I will start reading the thread.

[bigandtall]

I thought that the word was that it is good with pedals. My board is populated, I'm just pulling together my cab and speaker.

[smurfedelic smurfberry]

Yeah, I had it mixed up with something else.

[Taylor]

In what way was it "unfriendly" with pedals in your estimation?

[bigandtall]

FYI, if anyone is looking for a cab, this guy makes great champ style cabs at a great price. He does tolex and tweed. With hardware or without. I just ordered a tweed one from him.

http://mergili.com/cabinetsale/

[smurfedelic smurfberry]

In what way was it "unfriendly" with pedals in your estimation?

No, I was completely mixing it with something else that uses a chip amp that begins with TDA7* 

[kinski]

Seems I don't have any 2.2ohm resistors. How important are those values?

[Taylor]

They matter. Together with the two 220nf caps they are for frequency stability of the output. According to the datasheet going any bigger could cause oscillation. "Too low" condition is not explained, at minimum I reckon you'd start to lose audible high frequencies as you go lower. I also think the amp probably doesn't like driving smaller impedances, maybe it'd overheat sooner or make sputtery noises.

If you really don't want to buy anything and you have any small value resistors around you can always parallel and series connect them to get the value you need.

[PRR]

> don't have any 2.2ohm

Five 10-Ohm resistors parallel is close-enough.

[Insulator]

OK... so back when the PCB wasn't available, I got together the bits required and did up a stripboard layout. I know the parts were working when I got them because I had it all running fine on a breadboard. Now that everything's soldered to the stripboard it's not working though, so I'm appealing for some debugging help.

Here's the layout I came up with, in case I've made a mistake there:

On that image, the back pins of the TDA would be the higher 3 of the 4 available slots - I ended up drilling holes between the traces, ensuring pin 4 was completely disconnected, then attaching pins 2 and 6 to the outer traces (I hope that explanation makes sense). Relatedly, I'm relying on the enclosure to join up my grounds - I'm using metal standoffs attaching to the outer strips and not using a pad behind the TDA. I'm fairly confident they're all connected, having done continuity checks with my multimeter. I noticed the official PCB seems to be using the opposite side of the TL072 to me, so that's different as well.

When I power the board, I'm getting a brief pop through my speaker, then silence. I'm using a 1.2k resistor and have ~13.6V out of the regulator. On the pins of the TL072 I have:
1 & 2 = 6.8V
3 = 6.49V
4 = 0V
5 & 8 = 13.6V
6 & 7 = 13.0V
Do these sound plausible, given that I'm using the opposite side of the IC to standard?

TDA pin readings:
1, 2 & 3 = 0.8V
4 = 0
5 & 7 = 0.09V
6 = 13.6V

Any advice on how to narrow down other potential problems is appreciated - I've about reached the limits of my experience/knowledge. Hoping I haven't killed one or more of the ICs with my sub-par soldering skills, but that isn't entirely unlikely.

[Insulator]

Quick update, in case anyone is wondering - I made myself an audio probe and I'm definitely getting good audio right to the TDA. I can't identify any connectivity issues for the TDA itself, so I think I've probably killed the chip itself somehow. I've ordered a replacement...

[bluebunny]

I "scored" a crap one off the bay.  Might have been Chinese.  Might have been a fake.  Anyway, didn't work at all - much like yours, as I recall.  Replaced it and it worked just fine after that.

[smurfedelic smurfberry]

added a james/baxandall tone stack, my favorite out the 3 tone controls i tried. (pcb available on my blog)



thank you taylor for getting this back in stock!

[Jdansti]

Looks great, Petter! I'm curious as to where you placed the tone stack relative to the Tiny Giant circuit.