Building the Tiny Giant amp

[smurfedelic smurfberry]

Thanks John!



"In" on the schematic is connected to the Tiny Giant PCB vol hole 3. "Out" is connected to 2, and GND to 1.

(The values comes from Super-Freq's blog, mostly)

[Jdansti]

Thanks. I'm kinda new to playing with tone stacks and haven't had success in the past trying to add them to amps. So you sort of wired it in parallel to the volume pot like this?



If so, that explains why my tone stack experiments never worked.

[smurfedelic smurfberry]

Sort of, yeah, I mean I don't have two volume pots, but I'm sure you understood that.

I tried the treble-mid-bass type stacks used by fender and marshall, didn't like them one bit for some reason.
The Stupidly Wonderful Tonecontrol v.3 or something like that was pretty neat for being a one knob tone Control.
Also goes in right Before the volume knob.

Something I wanted to do, but wasn't successful with pulling off was to use the 2nd IN/OUt channel on the TL072 for optional low-gain overdrive. Would love hints on how to do that, because what I did sounded like ass.

[Jdansti]

I built a Bandaxall, Fender and some other tone stack a while back and just tried placing it in front of this amp: http://www.amazon.com/gp/aw/d/B00C4OP75S/ref=sr_sp-atf_title_1_1?qid=1407914585&sr=8-1

It didn't work - probably because I just stuck it on the front end instead of after a preamp.

[smurfedelic smurfberry]

Hm, I got some results enough to feel comfortable that i had put everything together right with both the Orange Micro Crush and the Orange Micro Terror, just between the input jack...

[Jdansti]

There must be something going on that I haven't learned yet about the proper tone stack location within various types of amps.

[Insulator]

New chip is in, everything installed in the enclosure, and it lives! So, that vero layout is verified OK in case the PCBs ever go out of availability again.

Just got to stick some "Tiny Giant" text on the enclosure somewhere and then I'll post some pics of the finished product.

[Jnasty1217]

Hello, everybody.

My first attempt at the Tiny Giant has thus proven unsuccessful and i would like to know where to begin troubleshooting.

FYI: I am trying to wire a single coil pickup directly to "in," and an 8 ohm speaker directly to "out."

I have a 15a 5v power supply. upon powering up the circuit, i get no noise but my heat sink heats up quickly.



thanks

[waltk]

Well, a 15V 5A power supply would work better than a 5V 15A power supply.  Assuming that's a typo, you should check to make sure there's no continuity between the tab of the LM338 and your heatsink/enclosure.

[Jnasty1217]

Well, a 15V 5A power supply would work better than a 5V 15A power supply.  Assuming that's a typo, you should check to make sure there's no continuity between the tab of the LM338 and your heatsink/enclosure.

i did have the LM338 bolted directly into my heatsink. after i fixed it, i still have the same problem. is it possible that i fried it?

[waltk]

The LM338 is supposed to have it's output protected against short circuits, so maybe it's still OK.  Is the heatsink shared between the LM338 and TDA7240?  Do you know which one is producing all the heat?  Did you go through the build guide and verify that things that aren't supposed to be connected really aren't?  It's OK if the TDA chip tab is grounded, but not the LM338.  Neither speaker connection should be grounded.

[Jnasty1217]

The LM and the TDA do share the same heat sink, but i have the silicon spacers behind both. The LM is the one producing all the heat. Nothing is connected to ground that shouldn't be connected to ground. still no noise at all.

i was checking continuity and accidentally, one of my leads bridged two pads and i got a crackle through the speaker. so far, that's the only sign of life.

[StarGeezers]

 Don't the spacers go on each side of the chip ?

[jogina111]

rearding the 1uf cap on pin3 of the 7240, can a polarized electrollytic one be used? if so, which way should the positive/negative side go?

[rocket8810]

i was thinking, instead of adding a tonestack at the end, would it be possible to essentially put an amp sim pedal in front of the Tiny Giant. i was thinking that this would make the Tiny Giant sound like whatever the amp sim pedal is emulating, and give you an eq. so, if a citrus graphic MKII was put in front it would sound more like an orange, and DLS would make it sound like a marshall, etc. or am i wrong? cause i was thinking about doing that if possible and making a small amp to test effects instead of using my mesa at all hours of the day.

[smurfedelic smurfberry]

i was thinking, instead of adding a tonestack at the end, would it be possible to essentially put an amp sim pedal in front of the Tiny Giant. i was thinking that this would make the Tiny Giant sound like whatever the amp sim pedal is emulating, and give you an eq. so, if a citrus graphic MKII was put in front it would sound more like an orange, and DLS would make it sound like a marshall, etc. or am i wrong? cause i was thinking about doing that if possible and making a small amp to test effects instead of using my mesa at all hours of the day.

For what it's worth, I've run the fetzer valve in front of the tiny giant with satisfying results, and also the valvecaster.

[jogina111]

would it be safe to run the TG with a speaker rated at 200w? what would be the harmful effects to the speaker?

[Taylor]

That would be fine. The power dissipation rating means it can handle less than or equal to that amount of power before damaging the speaker, so it's fine to send less than the maximum for which it's rated. In fact, you should always use a speaker rated for more than your amp power if you don't want speaker distortion.

People sometimes write that "underpowering" a speaker can be bad but I think this is at best a fringe scenario and not something you should worry about here.

Speaker ratings can be listed in various misleading ways, so always go by RMS, not peak ratings.

[PRR]

> be safe to run the TG with a speaker rated at 200w?

Absolutely safe. Go ahead.

The flip-side is: a speaker built to withstand 200 Watt abuse has to be heavy-duty. Which means heavy. Which means less sound-output per Watt.

You *may* find that a light-cone speaker rated say 30W will (for the same power) be louder in the room than a similar heavy-coil speaker rated 200W.

And there are special-purpose "high power" speakers that just suck for guitar. A 200 Watt car sub-woofer will be very lame in the 80Hz-5KHz guitar band. But it stays the same lame all the way down to 50hz or 40Hz. Which is the only way to get gut-slam in a small size. But the 40Hz-80Hz does no good for guitar (even drop-tune), and the excess mass to pull it down an octave clobbers 6 octaves of guitar sound.
_____________________________________

> Speaker ratings can be listed in various misleading ways

Yes. If possible, use speakers RATED for guitar.

Guitarists max-out their amplifiers for long periods of time; guitar-speaker makers have to rate them that way.

Car-speakers are usually semi-honest. Some owners do max-out the amps (you have heard them drive by). Especially the ones who put in aftermarket speakers. The Tiny Giant is fairly safe for most larger car speakers, because it "IS" a car-radio amplifier with a little less power than a screaming car's alternator.

Hi-Fi owners do NOT max-out their amps. A 200 W hi-fi may have short peaks over 100W but plays at an average power (over a few seconds) of 20W, 10W, or less.

[tombaker]

rearding the 1uf cap on pin3 of the 7240, can a polarized electrollytic one be used? if so, which way should the positive/negative side go?

If you were to use a polarized electrolytic capacitor the negative side would be closest to pin 3 on the TDA7240 chip. On the musicpcb pcb the negative side would be closest to the 1M resistors.

I don't see that there would be an overly audible problem although it is widely thought that electrolytics should be kept out of the signal path as their noise rating is higher than say polypropylene.