Building the Tiny Giant amp

[pruttelherrie]

Ok, took it to the rehearsalspace this afternoon.

It is LOUD, but you'll have to manage your levels right to get the max out of it and the volumepot has no volume effect past 9:30.
Playing through a 4x12 (V30's), at 16ohm it was not loud enough for our typical rehearsals, but in the 4ohm input it was ok. It was pretty bright/trebly though, it might need some kind of low-pass.

Please note: I'm not complaining here, just reporting!
Taylor, thanks again for providing this kit!

Iwan

[Taylor]

Cool, glad you like it.

When you say it sounds pretty bright/trebly, what you're hearing is the actual sound of a guitar without tone-shaping.  I actually like it the way it is (I also play it through a 15" bass cabinet, so that will give me much more low end than a guitar 4x12), but I always assumed that most people would not want to play it straight without any EQ or pedals in front. If you want a more common guitar amp sound, you definitely need to get that with your pedals or by adding some kind of EQ to the amp.

[PRR]

> LOUD
> the volumepot has no volume effect past 9:30.
> pretty bright/trebly

Odd. The gain is very typical of other guitar amps. The amp is "flat", and guitar amps usually boost treble.

Makes me wonder if there is some build error. Wrong-value cap in wrong place.

Is volume pot linear or audio?

If no build error: if you have space, you could insert the classic Fender Tone Stack. Re-scaled for the lower impedance of TDA. Cuts gain, and allows taking out the nasal midrange so boom and sparkle cut through.

[pruttelherrie]

Uh-oh some misunderstanding here.

Rehearsalspace testing was with a rackmount high-gain tube preamp. (Full disclosure: Ultimately I'm only interested in tah br00talz, even though I'm a FX junkie with a case of GAS)
I had to turn down a lot of trebles to get it to sound like the normal rackmount (tube) poweramp.

This build used the musicpcb kit, I don't think I have mixed up capacitors.

[thedefog]

Uh-oh some misunderstanding here.

Rehearsalspace testing was with a rackmount high-gain tube preamp. (Full disclosure: Ultimately I'm only interested in tah br00talz, even though I'm a FX junkie with a case of GAS)
I had to turn down a lot of trebles to get it to sound like the normal rackmount (tube) poweramp.

This build used the musicpcb kit, I don't think I have mixed up capacitors.

I just built a Big Muff tone stack into it right on a pot and that worked pretty well for being able to dial in a nice warm sound. Then again, I'm also using a cheap-o single 12" speaker, so it was already a little dark sounding. But I like that so it works great for me as a practice/synth/effects testing amp for home.

[p_wats]

Hey guys,

I finally had time to test this guy out tonight. So far all I've done is populate the board and gator clip the peripherals so I could try it out (with heat sinks in place).

Sounds great, but there's a lot of hum---is this likely simply because it's not boxed up or have I over-simplified the grounding scheme by not connecting anything together (just all leads from the PCB as shown in the PDF)? How particular does the wiring need to be to avoid hum as well?

What I can hear sounds great though, so I'm very excited.

Thanks!

[Taylor]

Check back over the thread, especially thedefog's posts, who had the same problem. Not having it boxed is probably at least part of the problem.

[p_wats]

I was messing around with it tonight using an OD/Boost circuit in front as a preamp and ooh boy that was fun.

So far I find my Tiny Giant (un-boxed, just gator clipped) to get unruly very quickly with a turn of the volume knob (though I'm using a linear 10K, as that's all I have right now, so my taper isn't what is expected). The best result so far has been with the amp very low, but a MyTon Blonde in front supplying the gain.

I could use a bit more treble so far, but the cab I'm running it through is far less than ideal. Very fun.

[StarGeezers]

Er, Taylor ... Got my TG board populated ... but I seem to have an extra cap  (224L)   , from the kit ... did I miss something   I can't seem to find a place for it    Can't wait to get the TG working/playing !!! 

[Taylor]

No, that's just a freebie.  There was an error with some of the kits that they got a wrong cap, so I went back and added the correct cap to them, but left the wrong one in. So that extra 220n is not needed.

[StarGeezers]

  OK, Thanks !!!   I looked and looked for that one ....hahahahahaha

[Hayden]

 I am using a 6 inch 4 ohm speaker rated at 65 watts. It has a pretty good size magnet. Is this a suitable speaker for maximum volume. It sounds really good but wondering if a lesser speaker would be better. I was going to post a pic of the finished cabinet but couldn't figure out how to do that.

[Taylor]

There's no issue with underpowering a speaker. If you want more volume, you'd need to check out the speaker's sensitivity/efficiency rating, and you also need to take into account the efficiency of the cabinet it's in. Guitar cabs are basically the worst cabinet design possible from the standpoint of real engineering, and in general they have very bad sensitivity ratings. But most guitarists prefer that type of cabinet for the sound.

[PRR]

> a 6 inch 4 ohm speaker rated at 65 watts

A small speaker with a large power rating, mass-market, is surely a LOW efficiency speaker.

(There's also hot PA system array midranges, but flubby home speakers are a million times more common.)

Fondle the paper. Is it thin and hard (and light) like typing paper? Or thick and fluffy (and heavy) like compressed paper towels?

To get LOUD you want a large speaker or a large amp (or both). "Large" amps are not physically large and no longer very expensive. When customers demand compact boxes and medium loudness, the designer goes with a small speaker and "large" amp to brute-force the insufficient cone area.

Also small speakers "sound" small. Your ear can tell the size of a sonic object; sometimes small speakers doing full-orchestra can trick the ear and "sound big", but a naked solo guitar makes the source size more obvious.

If you are broke, but happy, do it.

If you can spear a few dozen bux, get a GUITAR speaker nearer 10". Aside from being light and efficient, it has "zing" that you don't want in a hi-fi but DO want when making music with the fairly boring sound of bare steel string on solid axe.

If you want a MAXimum of sound for a minimum of Watts (as in tubes or battery-power), go with the biggest cone(s) you can carry. A Four-Ten stack is an excellent start. But a tight fit in the Civic.

I have a concept that guitar "should be" a Ten or a Twelve, about the size of the active part of an acoustic guitar's soundboard. (The edges don't vibrate much.) And electric guitarists want "MORE!" and should start with the killer Two-Twelve Twin. (OTOH there's kick-butt sound in one heavy-duty Twelve with a 300-Watt amp.)

> the efficiency of the cabinet

Cabinets don't have an efficiency.

Speakers and their cabinets/baffles "should" be integral, but are normally made by very different workshops, and speaker makers don't like to get involved in cabinets (which are often more looks than function).

Cone speakers "need" a baffle to support their lowest octaves. The box has little effect in the speaker's middle register, but a naked speaker is gut-less. A large baffle supports down to a certain bass limit, a clever tuned box can support even better to a certain note then sacrifice all lower notes.

> Guitar cabs are basically the worst cabinet design possible from the standpoint of real engineering

No, they are (many of them) an excellent compromise between efficiency, projection, and size, over the narrow band and desired response shape for guitar. This is a different problem than what T&S published on. Thiele's work is applicable, but too high-level for ordinary people, and focuses on the "flat" result. Small specifically targets extended lows in small boxes, rather than the rising response and LARGE cone area needed for loud portable guitar amplification. Don't let the experts buffalo you. The Fender Twin is a fine design for ballroom use. The Twin with two JBL D-120s is an astonishingly efficient air-whacker, 100Hz-1KHz. It sucks below 80Hz and the phasiness above 500Hz is very strong. An unfaithful hi-fi but a wonderful guitar voice.

[Taylor]

Ok, me debating you is like me picking a fight with Ivan Drago, but what the heck? 

Cabinets don't have an efficiency.

Perhaps you meant this as more of a semantic argument, but do you disagree that, for example, a horn loaded cabinet increases coupling efficiency? And does that not have the effect of blasting my ears more?

> Guitar cabs are basically the worst cabinet design possible from the standpoint of real engineering

No, they are (many of them) an excellent compromise between efficiency, projection, and size, over the narrow band and desired response shape for guitar. This is a different problem than what T&S published on. Thiele's work is applicable, but too high-level for ordinary people, and focuses on the "flat" result. Small specifically targets extended lows in small boxes, rather than the rising response and LARGE cone area needed for loud portable guitar amplification. Don't let the experts buffalo you. The Fender Twin is a fine design for ballroom use. The Twin with two JBL D-120s is an astonishingly efficient air-whacker, 100Hz-1KHz. It sucks below 80Hz and the phasiness above 500Hz is very strong. An unfaithful hi-fi but a wonderful guitar voice.

Well... for example, standard guitar cabs have intense beaming and terrible off-axis frequency response. That could be improved easily and with no drawbacks. The freq response you mention might be right for the guys 15° off-axis, but for anybody right in front of the cab all they hear is 1k shredding their ears, and for anybody 50° off, all they hear is mud. If you like the response of that cab, wouldn't it be nice for the whole audience to hear it?

Maybe my assessment was exaggerated, but unlike tubes, I don't see much reason to cling to obsolete tech in this particular instance. But it was mostly meant as an aside, and I don't begrudge people using what they like.

Ok, now go ahead and break me.   

[azrael]

SO, it definitely needs to supply more than 4A? I have an extra laptop supply that can do 3.4A.

[waltk]

SO, it definitely needs to supply more than 4A? I have an extra laptop supply that can do 3.4A.

Mine draws about 1A when I first turn it on for a second or two.  Then it settles down to about 70ma with no input.  With the volume turned up and playing hard it doesn't draw that much.  Even if the laptop supply can't supply more than 3.4A (and it probably can for intermittent peaks), I would think it would be fine.

I believe Taylor's recommendation is a conservative one, based on the theoretical power requirements of the chipamp.

[p_wats]

I'm finally ready to box mine up. For the sake of simplicity I'm going to ditch the OD-pedal-as-preamp and just implement the BMP tone control. Where do you think the best place to slot that in would be (I assume I could interrupt the connection to the volume pot and toss it in there...)?

[Taylor]

I would do it the way PRR has suggested here:

http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg768743#msg768743

[p_wats]

I would do it the way PRR has suggested here:

http://www.diystompboxes.com/smfforum/index.php?topic=89687.msg768743#msg768743

Ahh, didn't see that. Nice looking option. I don't think I have room for so many knobs in my enclosure though. A simple single knob tone-control is all I can likely fit.