Building the Tiny Giant amp

[waltk]

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?

There are other power supplies that are as good/cheap.  Search for "IBM 16V 4.5A" on Ebay, and you'll find hundreds.  Taylor has updated the build documentation recently, and he's suggesting a laptop power suppy from 15-20 Volts.  The reason that less voltage (within that range) is better is that any extra power supplied to the board must be dissipated as heat by the onboard voltage regulator. 

I'm not sure what size plug they are using, but I found it easier to cut the plug off and attach a standard Boss type plug anyway (2.1mm X 5.5mm - inside, outside).  That was my preference because I already have a stock of that size plugs and jacks.

[David]

I see.  That takes care of the low-hanging fruit.  Thanks for the insights, Walt.  I'll check out the power supply you indicated.

[David]

Now for the next set of questions.  In the build instructions, there are two paragraphs that seem like they might conflict.  If you intend to use the case for heat sinking purposes, would you not WANT the amplifier and regulator ICs to be mounted directly to the case?  Especially if you use a plastic jack for the speaker cable?  I thought also I should use a plastic jack for the audio input, although that throws me into a tizzy about grounding.

Anyone got any ideas how to sort this out?  And also, how would one tie into the amp circuit to provide external power -- like to a pedalboard?  I was actually thinking I could connect a 9V regulator and some capacitors to the external power connections and run it to two binding posts inside the amp case.  I could then connect a series of power cables with male Boss connectors on one side and rings on the other to attach to the binding posts.  This way, I get an amp AND a power supply AND a distribution bus AND only one power cable coming to the pedalboard. 

[waltk]

Now for the next set of questions.  In the build instructions, there are two paragraphs that seem like they might conflict.  If you intend to use the case for heat sinking purposes, would you not WANT the amplifier and regulator ICs to be mounted directly to the case?  Especially if you use a plastic jack for the speaker cable?  I thought also I should use a plastic jack for the audio input, although that throws me into a tizzy about grounding.

The amp IC has its heat sink tab internally connected to ground, so attaching it to the enclosure both grounds it electrically and provide a good heat sink (a desirable thing).

The voltage regulator has its heat sink tab internally connected to the V+ output - so  you MUST NOT connect it to ground.  That's why Taylor provides the special bushing with his kit; so you can physically attach the voltage regulator to the case for heat sinking purposes, while keeping it electrically isolated.

Because of the design of the chip amp, you don't want the speaker outputs connected to ground - or anything else.

Your plan to use the power supply for multiple purposes will work fine (I've done it).  You could actually power the rest of your pedalboard off of the same laptop power supply.  Depending on how big your pedalboard is (how much current your pedals draw collectively), you could do it with an LM7809 (1 amp), LM317 (1.5 amp), or LM338 (5 amp).

[Taylor]

David, some of your questions are covered in the PDF. Check it over a few times to get familiar with some of the details of the project, w.r.t. grounding especially.

[thedefog]

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?

Hey there,

The type plug used on the supply I bought fits into a 2.5mmx 5.5mm, so the boss-style won't work. Radioshack sells these though, and that's what I wired it up to.

I was going to build an enclosure for this mini-amp, but realized that I suck with wood-working and that it would probably look like total crap. Good thing I had my dad's busted TEAC Reel-to-Reel sitting nearby. I made a speaker baffle from a piece of scrap wood and dremeled out a circle, mounted the speaker, and fit it right inside the TEAC. It even has a little side-pocket where the input.output controls used to be for guitar input/volume/tone.

[wakeuptone]

Taylor.... If I have the preamp, do I still need TL072 as you schematic.? 

[Taylor]

You can skip it if you want. But I find it easier to just build it stock. You don't gain anything by bypassing the buffer, and it's cleaner (the wiring I mean) and only like 50 cents in parts, but that's just me.

[wakeuptone]

You can skip it if you want. But I find it easier to just build it stock. You don't gain anything by bypassing the buffer, and it's cleaner (the wiring I mean) and only like 50 cents in parts, but that's just me.

Taylor...thank you.  I will buy the stock board and try it

[rotylee]

Resistors
all 1/4 watt

1 – 100k            Brown, black, yellow,
1 – 220k           Red, red, yellow,
2 – 1m      Brown, black, green,
2 – 2.2R            Red, red, gold,
              [Marked "2R2" on the board - this is 2.2 OHMS]
1 – 1k      Brown, black, red,
1 – 120R           Brown, red, brown,

is this correct?

[thedefog]

Hey guys,

I got the new power supply the other day and finally got around to testing it with the amp. It wasn't the source of my buzzing noise unfortunately...

I double checked with the schematic and tested my voltages, which all checked out good. All grounds are going to where they need to, and my heatsink is not shorting to the back of the V+ regulator. I reflowed solder in case I had any cold joints (doubtful) and triple checked my wiring. Also rechecked resistor and cap values and orientation. All checked out good.  The buzz gets louder as I turn the guitar volume down. With no instrument plugged in, it is a very loud buzz. When I ground the input wire, it completely goes away. When I remove the TL072 out of the socket, there is only a faint buzz present. I tried different TL072s as well as other dual opamps and it didn't help. Something is up with the input buffer stage, only all my grounds and part values are correct.  

[Taylor]

Resistors
all 1/4 watt

1 – 100k            Brown, black, yellow,
1 – 220k           Red, red, yellow,
2 – 1m      Brown, black, green,
2 – 2.2R            Red, red, gold,
              [Marked "2R2" on the board - this is 2.2 OHMS]
1 – 1k      Brown, black, red,
1 – 120R           Brown, red, brown,

is this correct?

Yes, that's right. Do you have a multimeter? It will be incredibly helpful to you on this build (checking ground continuity as mentioned in the PDF in addition to checking resistor values).

Hey guys,

I got the new power supply the other day and finally got around to testing it with the amp. It wasn't the source of my buzzing noise unfortunately...

I double checked with the schematic and tested my voltages, which all checked out good. All grounds are going to where they need to, and my heatsink is not shorting to the back of the V+ regulator. I reflowed solder in case I had any cold joints (doubtful) and triple checked my wiring. Also rechecked resistor and cap values and orientation. All checked out good.  The buzz gets louder as I turn the guitar volume down. With no instrument plugged in, it is a very loud buzz. When I ground the input wire, it completely goes away. When I remove the TL072 out of the socket, there is only a faint buzz present. I tried different TL072s as well as other dual opamps and it didn't help. Something is up with the input buffer stage, only all my grounds and part values are correct.  

Hmm. I'm not an expert on switch mode power supplies, but my assumption was that, with the switching action and regulation in the supply, then regulation on the amp board, there would not be much chance of 60 cycle hum coming from the supply. So this leads me to think that the hum is coming from another source and being coupled through the signal grounds. Do you still not have it boxed up or shielded at all? I never built one that wasn't in an enclosure, but that seems like it could contribute. Any other parts of the puzzle you can provide - what kind of guitar with what kind of pickups for example.

I will think some more about what might be happening and get back if I can think of anything.

[thedefog]

I'm running it outside of an enclosure, no shielding, so that probably explains a few things. I'll triple check my continuity to ground everywhere again just to be sure, especially on the input buffer stage. I'm using my tele with a humbucker in the bridge, and the noise doesn't really change much in volume between the HB and single coil. It is quite in my other tube amps.

Shielded input cable may help my cause a little here, I'll try that out and see if it helps. It is definitely 60hz hum I'm getting.

[thedefog]

I made a mounting plate for the input jack, power, volume, and a tone stack (BMP) into cabinet I am using, and that pretty much took care of all the cyclical hum I was getting.

[Taylor]

Cool, glad to hear that it's sorted. I had a feeling some shielding would do the trick.

[StarGeezers]

  Got my power supply ordered off Flea Bay !!!   TG kit on the way ...   Very exciting !!!   

[Brymus]

  Got my power supply ordered off Flea Bay !!!   TG kit on the way ...   Very exciting !!!   

LOL now your gonna be banned from SEwatt
How are the Stargeezers doing this year ?
You actually live close to Taylor ,same area at least.
You still using your Croaker amp ?

[ckyvick]

Is this a good ps?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270607079418

[Taylor]

Yes, that looks good.

[David]

David, some of your questions are covered in the PDF. Check it over a few times to get familiar with some of the details of the project, w.r.t. grounding especially.

I got it.  Closer reading did the trick.  I also got my kit today.  Excellent workmanship!  Now, some more questions:

1)  I am not familiar with soldering to a board with little grommet-like things like this one has.  I presume I simply solder to the grommets?!?  Is a special soldering tool required?  I have the standard 25W small soldering iron.  It has a point, but I'm not sure how well it will get into those grommets...  Also, I presume the components will go on the silkscreened side of the board?

2)  Since I am planning to draw power from the specified connector to feed my pedalboard, I got a castoff power supply from the local computer store that puts out 5A so there's an amp or so available to my pedals.  Unfortunately, this supply delivers something like 18 volts, but my amp is going into a RACO box.  That should be enough metal to keep the temp down, right?  Would I get the ground connection from the point where the power supply ground connects to the amp board?