Small SS poweramp

[zedsnotdead]

Hi people!

This is my first post and I am sorry to bother you with this, as I know there are similar questions posted like this one.
Well, I used the search function to find information os this, but I am a newbie when it comes to electronics, and I think I didn't find the right answer.

So, I need to build a SS poweramp, the cleaner the better, with around 3-5W and to be fed with a 9V-12V powersupply (like the regular ones we see feeding stompboxes), and connect to a 8Ohm speaker load.

I found about Tiny Giant amp, but it needs 4A current and it's 20W... so no luck with that one I think? Also had to buy the PCB, and I was hoping to etch it myself.
Also found about beavisaudio noisycricket, but... 0,5W is too low power...

DO you have any more suggestions I could check?

Thank you so much! Really appreciate your patiente and time with ths one.

[zedsnotdead]

err... I am embarresed to say it but... I don't know how to design a PCB, i Just know how to print the ready-to-transfer layout and etch it...
Sorry, my skills aren't so good yet.

[Jederino]

Nah, don't be embarrassed, some of us only know how to buy prefab boards.  Har har!

Not sure if this helps, but looks at Tayda's kits.  There's some power amps in there.

http://www.taydaelectronics.com/electronic-kits.html

[zedsnotdead]

thnk you for your reply!

well it might be difficult to me to buy anything tayda have cause i am not in US...
I checked tayda kits and the only amp is that LM386 stereo one, I think... The one I am trying to find is a practice poweramp for guitar (mono).
My aim is to find a DIY project (if it has a PCB layout ready it would be nice) that I could buy the parts, etch the PCB and so on.

[chromesphere]

Hey zed, there was a small wattage (2w approx i recall) amp going around called the punch amp.  I built it up, it was ok, for practicing on.  Search the forum for that one.  Theres also a tonne of others.  Some more powerful.  Hopefully others will chime in with suggestions.

Heres a video of the punch amp:

I also built a smokey amp, sounded quite good and had a bit more volume then the punch, but it wasnt clean by any stretch of the imagination, and it was the most temperamental thing you have ever seen.  Heres a video of that one:

A couple of options anyway.  Check out Petey Twofingers channel as well, he's got loads of experience with battery / small scale amps.

Good luck!

Paul

[WaveshapeIllusions]

The Tiny Giant should still be useable. If you use a lower supply voltage you will need less current and it would be less power. For example, if you run it at 9V it will come out at ~9 watts of power and you'll just need an amp of supply power. A few things will likely have to be changed though, as I believe it uses a regulator. You may want to ask for more details in the Tiny Giant build thread.

[Seljer]

The output power is largely a function of supply voltage. So you can take something like the Tiny Giant (or any other of the TDA or other power amp chips) and run it off 9V and you'll get about 6watts output (you'll still want at least 1.5A from the supply though). Reference the data sheets.

[psychedelicfish]

The TDA1905 is a good chip to use, it can easily do a nice sounding 5w, and I could design a PCB for you if you want

[zedsnotdead]

Thank you so much all of you guys!!

(and hello again Paul! Nice to see you here!)

So what I understand is:

1- TinyGiant can run on a "normal" 9V PSU, as long it has enough current to drive the 8 Ohm speaker (right?)
2- Punch Amp, it's really interesting! Just found the thread and .pdf (which includes the PCB layout).  Just a question though: if I want to regulate the volume should I use a 1M log connected to output? and it delivers only 1W right? (maybe enough loud when connected to a 10" 8 Ohm Celestion speaker I reckon?)

[jogina111]

even the noisy cricket can drive up to 4x12 cabs.. I just dont know if you'd want some overdrive..

[earthtonesaudio]

Thank you so much all of you guys!!

(and hello again Paul! Nice to see you here!)

So what I understand is:

1- TinyGiant can run on a "normal" 9V PSU, as long it has enough current to drive the 8 Ohm speaker (right?)
2- Punch Amp, it's really interesting! Just found the thread and .pdf (which includes the PCB layout).  Just a question though: if I want to regulate the volume should I use a 1M log connected to output? and it delivers only 1W right? (maybe enough loud when connected to a 10" 8 Ohm Celestion speaker I reckon?)

The Tiny Giant is almost exactly what you want.  With a 9V supply, the output power of the TDA7240A is about 6W.
If it was me building it, I would omit the regulator and just wire +9V to the pad where the regulator output used to go.

[Renegadrian]

TDA 2002 or 2003 - you should get 8-10W
Quite easy to build one!

[teemuk]

So, I need to build a SS poweramp, the cleaner the better, with around 3-5W...

This is your first problem. For clean tone you need power so if you want a clean amp you most definitely do not want a low power amp at the same time.

...and to be fed with a 9V-12V powersupply (like the regular ones we see feeding stompboxes), and connect to a 8Ohm speaker load.

And here's your second problem. The supply voltage is way too low to get sufficiently high output power, especially to 8-ohm load. If you must use low supply voltage then you should consider using lower load impedance. Something like a 9VDC supply will produce way more power to, say, a 2-ohm load than it does to a 8-ohm load. Furthermore, you can try a bridging setup to develop even more voltage across the load.

I found about Tiny Giant amp, but it needs 4A current and it's 20W...

Most power amps will draw lots of current, it's simple Ohm's law. And yes, with output power levels that deliver ample headroom the power supply must be designed to deliver that current. So ditch those wall warts (that can only deliver few milliamps for pedals) before you even start. It's just something you have to live with.

---

Since clean tone is the goal I would seriously consider forgetting the wall wart power supplies completely, going straight to >60W designs and/or choosing an efficient class-D design (discrete or chip) for the power amp.

[tca]

^ That, and also the speakers efficiency. If you are using a  10" 8 Ohm Celestion speaker I think you'll get enough clean power with the PUNCH. But... powering it with 9V to get 1W you will need at least  this current: I= sqrt(P/Rspeaker)=1/(2*sqrt(2))=350mA. A 1W amp with the right speaker can be very loud.

There's no way around it. You want clean power, you have to supply the needed current.

There is really no such thing as a *small clean amp* (small is a relative measure), the hard part of all this, in what concerns amplifiers, is not amp it self, but the power source! Designing the power source comes first.

P.S.
You can build the PUNCH and feed it with a 9V/100mA wall wart, it is already loud and clean with that, but not 1W.

[earthtonesaudio]

A "small clean amp" is a large amp turned down.

[zedsnotdead]

Again thank you so much for your replies.

So the "main" problem is the PSU right?
I thought that as a EHX .22 Magnun could deliver 22W (@8 Ohms) with a 18v psu, a 9V PSU should be enough for 5W @ 8Ohm... gess I was somewhat wrong, specially if I want a clean amp.
The amp is to be used with guitar and stompboxes. So I thought the cleanest, the better for this purpose...

@tca: not 1W? What if I get a 12V DC wall wart?

[Mark Hammer]

What function do you intend for this amplifier to fill?  Is it intended as a bedroom practice amp?  a busking amp?  a coffee-house self-accompaniment amp?  a gymnasium announcement amp?

I ask because the power output goals will determine the power-supply requirements.

I have to say that I am routinely surprised by just how loud my little LM380-based 12VDC-powered (8 rechargeable C-cells) amp can get.  Not that you shold make one, but sometimes the wattage requirements can be less than what we think they need to be.  Five watts is not that nmuch louder than 1-2W, and the audible differences can often be more than offset by speaker choice and cab design.

But again, this comes down to what you intend to use it for.

[tca]

Instead of writing everything down, here is a thread with a lot of info that is related to your project: http://www.diystompboxes.com/smfforum/index.php?topic=102512.0

Cheers.

P.S. (edit)

no 1W, maybe 0.6W

[zedsnotdead]

Ok, so I have this:
-  PSU that is rated 12V@500mA (or 9V@600mA), unipolar.
- Speaker is 16 Ohm (not 8 Ohm, my bad...) - http://www.eminence.com/speakers/speaker-detail/?model=Legend_10516

So, it's a guitar pratice amp. With your help I understood that anything from 1W to 5W should suffice, as long it takes pedals OK (that's why I thought of a small "clean" amp)

LM386 out of the equation then. So it's the tiny giant or punch. I lean towards the later because I could etch the board myself, and also I don'0t know if a unipolar PSU would work with tiny giant.
Agree?

@tca: just noticed you're from Portugal.
posso enviar PM?

[mistahead]

Go old school and learn some interesting fundamentals...

I'm concurrently playing with a bridged LM386N-4 (oh why oh why are there so few online schems for applications using the -4 in bridged mode) and as part of teaching myself I'm working towards a multi-stage discreet transistor amp, testing out different class layouts and approaches on my breadboard.

So why not build a discreet AB transistor amp?