Building the Tiny Giant amp

[Taylor]

This will be the spot for questions about building the Tiny Giant. Questions, discussion, mod ideas, and build reports will go here. Here's my prototype build. I have a few ideas for another one I want to build, this one with 2 of the boards for stereo and some EQ.

[Taylor]

Hey Taylor,

Thanks for the kit! I got it tonight and built it up. The board is top notch quality too! I tested it out with my gateway's generic power supply and on my twin reverb's speaker cab. I'm amazed at how loud it gets. Pretty impressive! Only thing now is that I have a buzz on it that I have to debug. It's got to be due to the crappy power supply I'm using, so I'm thinking I'm gonna just grab a hold of a 24vDC transformer at 4A and build a power supply myself with some decent filtering caps. I know that sorta goes against the tiny factor of it, but I intend to building it into a super small home-made combo amp cabinet 1x12 with a tone stack and the tiny tremolo circuit for fun.

http://cgi.ebay.com/24V-5A-TRANSFORMER-BRAND-NEW-BLOWOUT-SALE-PRICE-/330517526923?pt=LH_DefaultDomain_0&hash=item4cf461398b

That one looks cheap enough to try out. I shouldn't have to change any resistors with the 24 volts on the regulator, correct? Should I worry about excess heat?

I'm also using a cheap power supply and I have no hum, so I don't think you need to go as far as adding a transformer. I suspect you have some kind of ground loop or ground issue. How exactly do you have it built now? Is it in any kind of enclosure? If so, is the enclosure grounded? Have you taken care not to connect the sleeve of the speaker jack to ground as shown in the PDF?

Also, let me know if you had any questions that the PDF did not help with while building it. 

[thedefog]

I'll take a picture of my build. I don't have an enclosure yet. I'm just testing out the input with banana jacks currently, and have temporary speaker and power jacks wired. I did notice though that my power supply was emitting a ultra high pitched squealing sound when it is plug into the wall. I'll get a hold of another laptop power supply to test with and post my results here.

[thedefog]

I just ordered this power supply: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=130343776062&ssPageName=STRK:MEWNX:IT

I will post my results when it arrives. I needed one anyway, and $8.00 was cheap enough to test, and it doesn't hurt to have a back-up power supply for my laptop anyway.

[thedefog]

I meant alligator clips. Don't know why I said banana jacks... Must have been looking at my soundlab synth.

Anyway, your PDF looked great Taylor. I had absolutely no issues building it, and it is all very well marked.

In the meantime, I'm looking into active eq and running a tiny tremolo circuit as well. I like your idea for stereo, I can imagine the possiblilties for stereo effects. A nice stereo ping-pong vibrato like that on a Rhodes piano with the bass and treble swapping sides alternately would be amazing.

[PRR]

If those are the Swiftech MC14 sinks, they are only rated for 5watts... I'd be concerned about not having enough heat sink in this situation.

TDA7240 is 65% efficient.  So if it is puting out 10 watts (which is about the max into an 8 ohm load without too much distortion), then it will consume 15.38 watts.  That leaves 5.38 watts to dissipate as heat.

Dissipation in a Class B amp is greatest BELOW maximum power output. At FULL signal, power comes in and goes out. At half power, a little less power comes in but much less power comes out.

Somewhere in that sheet is a curve showing dissipation peaking near 8 Watts at part power.

I'm not real concerned. Experience with FTC testing which holds an amp near maximum heat for many minutes proves that real-world dissipation is usually MUCH less, even in stage-amps. If you do skate too close to the edge, the chip will shut-down, you feel it and burn your finger, you have a clue to get a bigger sink.

CLEAN power in 16 ohms is 6 Watts (maybe 8W the way car and gitar amps are specced). There's probably a simpler path to 6 Watts in 16 ohms.... and maybe not, since Taylor's kit is so neat.

NewEgg specs: "C/W: 9.0 (including TIM joint)
Maximum recommended heat load: 5 Watts per heatsink"

Taking the first number: 8 Watts at 9 deg C per Watt is 72 deg C rise above ambient. On older discrete audio-amp devices we liked to stay below 50 deg C rise..... but seals and dice have improved a LOT, and the on-die thermal shuts-down on short-term events we may never have known about in the days of mercury thermometers.

The 5W at 9C/W or 45 deg C seems very conservative when this is the major heat-load in the box, but may be appropriate when you have a hot CPU and too much other stuff jammed into a small PC.

[ckyvick]

What sort of power supply would one need to build two of these into one enclosure and use a stereo input jack? Just wondering

[Taylor]

I'll be doing just that pretty soon, so I will report if I have any trouble using a standard 19.5v/4amp supply for 2 boards. My suspicion is that the chip isn't going to actually draw 4 amps of current, but I have seen some supplies on ebay with 7 or 8 amps if that is indeed needed.

[ralley]

Just received by PCB and kit last night - stunning quality.  At first I thought the PCB was missing - it's that small I could barely feel it in the padded envelope it shipped in!

Built it up in <30 minutes, just waiting for my power supply to arrive now.

I've added the Tiny Giant to the Wiki under Pedal Specific Info -> Amps -> Tiny Giant (http://www.diystompboxes.com/wiki/index.php?title=Tiny_Giant).

Rob.

[Taylor]

Hi Rob, thanks for adding it to the wiki - I haven't really looked at that and kind of forgot that it existed!

[bassmannate]

Taylor,

I'm probably going to order a kit here soon. I'm planning on putting it in a large enclosure so I can put it together with several pre-amps. Would I still be fine using the chassis as a heat sink or should I get a separate heat sink? I'm planning on making the chassis from scratch using sheet metal.

Edit: I also have a laptop power supply that I don't use any more. It's older but is 19.5v but at 3A. If my calculations are right, it comes out to 58.5W of power which means it SHOULD work with the amp right?

[Taylor]

Using a bigger enclosure is even better for heat dissipation. Just be sure to keep the regulator's heat sink tab electrically isolated from the enclosure as per the PDF.

That laptop supply should be fine.

[Skruffyhound]

Hi, just subscribing to the thread. I'm waiting to see how you get on with stereo with this Taylor. One of the other boards I got from you is earmarked for my reverb plate to replace the ruby. Thanks for the project.

[Taylor]

Ah, very cool. I was hoping we'd see these turn up in some uses beyond straightforward amplification. I'm building a spring unit right now, but a plate would be quite nice - I'd like to build one at some point. Shame I can't think of those wonderful plate reverb sounds of the 60s without my mind instantly going to Phil Spector on trial...

[thedefog]

Just received by PCB and kit last night - stunning quality.  At first I thought the PCB was missing - it's that small I could barely feel it in the padded envelope it shipped in!

Built it up in <30 minutes, just waiting for my power supply to arrive now.

I've added the Tiny Giant to the Wiki under Pedal Specific Info -> Amps -> Tiny Giant (http://www.diystompboxes.com/wiki/index.php?title=Tiny_Giant).

Rob.

Yup the kit Taylor put together is great. The PCB is top notch, and all the components are perfect and perfectly spaced for the board he sells. Thanks again Taylor for putting this project together. As soon as I settle on a tone stack that I like it is getting built into a mini amp for practice/backup.

[bassmannate]

Using a bigger enclosure is even better for heat dissipation. Just be sure to keep the regulator's heat sink tab electrically isolated from the enclosure as per the PDF.

That laptop supply should be fine.

Awsome. Now I just gotta figure out how big of an enclosure I want and go get a piece of sheet metal. Not sure if I want to use steel or aluminum. Aluminum would probably be a bit easier to work with but steel would be much stronger I would imagine.

[culturejam]

I totally forgot about this project!

Just ordered a PCB/kit. Great work, Taylor.

I was just thinking, though, that maybe a power on/off switch would be more useful (for me) than a standby switch. For amps, I like to be able to turn them off without resorting to unplugging them...even for a really small amp.

I'm assuming that using a SPST switch between the positive (or negative) power supply lead and the PCB will do the trick?

[Taylor]

Yep, that will do it. I should add something about that in the project. I somewhat enjoy the ritual of standby, then power, so I'll probably have both in my bigger version. Plus it keeps speaker pop from happening, I suppose. Thanks for the props - I'm happy about how this turned out.

[culturejam]

I somewhat enjoy the ritual of standby, then power, so I'll probably have both in my bigger version.

Yeah, me too. That's what I was thinking. It's like a little tube amp if you have power and standby. 

[David]

I ordered my kit last night.  The concept of putting an amp right on my pedalboard is something I just CANNOT pass up!  My wife actually PUSHED me to order it.  I guess she doesn't think I can do it...

Anyway, I'm looking at the power supply that "thedefog" identified.  What I would like to know is, what kind of female connector is required to receive that plug?  Surely not a Boss?  Where can I get one?