Building the Tiny Giant amp

[azrael]

Is it possible to have a headphone out for the Tiny Giant?

Also, for the power jack, does it need to be isolated from the chassis? In other words, do I have to use a plastic jack like the ones commonly used in pedals?

[Taylor]

20 watts would be ear-splitting for a headphone amp. You could turn it down, but I think you'd be in serious danger of destroying your hearing by having that kind of power available. I built the headphone amp at General Guitar gadgets, works well and could certainly be implemented together in the same enclosure with the TG.

The chassis is grounded. Most people these days use center-negative power plugs, due to the Boss standard. Since you're not powering the TG on a daisy chain, you can use whatever plug and jack you like, but if you're using a metal one, you would of course need to use a center-positive plug and jack so as to not short v+ to ground.

[azrael]

That's what I figured, Taylor. Thanks for the speedy response!

[G. Hoffman]

20 watts would be ear-splitting for a headphone amp. You could turn it down, but I think you'd be in serious danger of destroying your hearing by having that kind of power available. I built the headphone amp at General Guitar gadgets, works well and could certainly be implemented together in the same enclosure with the TG.

Oh, I don't know.  I've recorded in a couple of studio's that were using 100 watt Crowns as headphone amps.  You just need to be careful about how high you turn it up, but having the available head room sure does make things sound nice.  Well, nice for headphones.



Gabriel

[p_wats]

We just plug ours into the SAME power strip as the PA .... and use a foam mic cover... No shocks , no spit in the mic.  If we loan the mic out, it gets a different cover... 

That's actually not a bad idea. I've been thinking about bringing my own mics to clubs anyway...

Thanks for all the help guys.

[haroldjenkins]

Hi there.... My kid and I are seriously considering building this amp and pairing it with a FET-based preamp project I found. I have an old amp that I'm planning to gut the electronics out of and using for this purpose. I read the PDF for the project stating the recommended power supply voltage range, but would it be safe to use a 24V/4A switcher? Unless I'm reading it wrong, the LM338 datasheet reads as if it's good to 30VDC. I'm sure I'd have to go with better heat-sinking if it works.
The main reason I'm looking at using this sort of power supply instead of a laptop supply is so I can mount it a little neater inside the cabinet. If I have to go with the laptop supply I'll make do but I'd thought I would throw the question out here.

[Taylor]

You'll be throwing away half the power to heat, so you'll need really good heat sinking. Otherwise I don't foresee any issues. I would still personally prefer to go with a lower voltage supply - I think you can mount them cleanly, but that's me.

[haroldjenkins]

Thanks for the reply, Taylor. Since I'm not interested in building a solid-state space heater, I'll just go with the laptop supply and mount it nice. Perhaps if it turns out allright I'll post a photo of it. It turns out that we'll be using every available pot and switch hole on the existing control panel so it shouldn't look too bad.

[svstee]

So I plan to build this with my daughter. Some planned mods:

1- 2 input jacks so she can plug in a mic at the same time.

Full range speakers, again, the mic.

Building it in a small combo, but with a 1/4" out so it can be a head too.

Probably gonna be pink and purple...

[sgmezei]

Alrighty Team,

My tiny giant fired up and I am trying to use it with a charge pump (madbeans "road rage") to supply 18v. It works fine until I turn it about half way up I get severe oscillation and pulsing. Can this not be powered this way? Am I not supply enough current?

Thanks folks.
ps- All the pin voltages checked fine and I made sure the speaker output was isolated. Used the meter to check for grounding.

Scott

[waltk]

Can this not be powered this way?

Correct, it can't be powered this way.  The onboard LM338 will just regulate the supply down to about 12V anyway.

Am I not supply enough current?

Correct, the the 1044/7660 in the RoadRage can't supply enough current.

[sgmezei]

alrighty. 

thanks team!

[firebird8600]

I am planning to put this in a radio shack plastic enclosure. I noticed that the aluminum lid fits under the plastic one. Is this sufficient for use as the heat sink? What sort of temperatures are normal during use?

[Taylor]

I would not recommend a heat sink with less mass than a 1590a enclosure. I'm not exactly sure to which lid you're referring so I don't know if it will work.

My 1590a box gets just slightly warm while playing for 40 minutes or so. This is at loud apartment levels with bass. If you were gigging with it you'd want more mass than a 1590a.

[waltk]

I am planning to put this in a radio shack plastic enclosure. I noticed that the aluminum lid fits under the plastic one. Is this sufficient for use as the heat sink? What sort of temperatures are normal during use?

The plastic Radio Shack boxes I've seen have a thin gauge aluminum cover.  The problem is there is not much mass to absorb the heat, and not much surface area to radiate it - especially if the aluminum cover is hidden under the plastic cover.  You could try a separate heat sink within the box, but even that would be a marginal solution because there is no to way to vent the heat, and it would build up inside.

[StarGeezers]

  How hot are these supposed to get anyway ?   I always run mine Clean/sweet spot , no real heat detectable ..  but a friend who built one  is using an OD in front, reports a WARM box ...   

[defaced]

How big is the box?  I'd been a while since I've driven the crap outta mine, but I recall the 1590BB that it's in getting pretty warm where the chips are located.  I imagine something like a 1590A would get pretty cooked if the amp were driven hard. 

[StarGeezers]

  Mine is in the 1.5" X 2.5" X 4.75" box .... hardly gets warm ... You guys ever try heat sinks... they Work !!  Fins look Cool too !!!   

[haroldjenkins]

I have mine just about finished. The Tiny Giant works great. The preamp I made works and sounds fine but for some reason the tone controls aren't working correctly just yet so I have to sort that out.

If anyone's interested in adding a headphone output to theirs, I borrowed the headphone jack from my old Squier amp and it has the resistors mounted right on it. From the schematic, it looks like it's just 220 ohm 1 watt resisitors going into both of the stereo contacts of the headphone jack. The schematic shows the headphone jack and speaker hooked to ground so of course that's a no-no. I just routed the wire that's grounded on the Fender amp to the other side of the Tiny Giant's output.

Here's the entire Fender shematic showing the heaphone jack output:
http://music-electronics-forum.com/attachments/3932d1230346488-squier15.gif

[firebird8600]

I am planning to put this in a radio shack plastic enclosure. I noticed that the aluminum lid fits under the plastic one. Is this sufficient for use as the heat sink? What sort of temperatures are normal during use?

The plastic Radio Shack boxes I've seen have a thin gauge aluminum cover.  The problem is there is not much mass to absorb the heat, and not much surface area to radiate it - especially if the aluminum cover is hidden under the plastic cover.  You could try a separate heat sink within the box, but even that would be a marginal solution because there is no to way to vent the heat, and it would build up inside.

Walt, I understand what you are saying, and I agree. By the time I had read your response, I had already finished assembly as planned (aluminum cover under plastic, with a hole cut out of the aluminum for the controls to go through). I put this into the 2.5X3X6" project box.
I tested it at full volume on a 4 ohm speaker with my Les Paul for one full hour. I am slightly surprised that it leveled off at 104 degrees Fahrenheit. Less than 10 minutes after I shut it down, it was back to around room temperature (75 degrees)

I do not know the temperature limits of the components. I do have room to add a fan to cool the amp, but do I really need it?
I am also not averse to scrapping the entire Radioshack box idea for a better one, but it does seem that it may work.