Voltage multiplier for TDA2030?

[Taylor]

Would it be possible to use one of the voltage multiplier circuits out there to derive 36v from a regular 9v wall wart? I'm looking for something to power a TDA2030 power amp. Most of the multipliers I see are for a range of 100-300v or so. I'm looking for something more modest.

Would there be any issues with running this chip with a multiplier circuit? I'm not exactly married to that chip in particular, but it looks good since it has decent power and runs on a single-sided supply.

[davidallancole]

Better off buying a wall wart that outputs 36V.  The switcher would be switching a lot of current to run that TDA2030 full bore into a speaker

[Taylor]

Ok, I should give more back story. I was thinking about doing an amp project for the forum, with a manufactured PCB. I wanted to investigate the possibility of making one that does not require working with mains power or transformers, or special power supplies, as these turn off potential builders, interest goes down and price per board goes up.

I checked out 36v wall warts, but they seem to be in the $60-$70 range. That will put off most people.

[petemoore]

  The chips are amazing, compact, well featured, very sensative and powerful, hot little buggars, can draw amazing current for their size.
 They're like a reflection of the input a suitable power supply like "a glassy pool of potential power", between the PS and heatsink/layout, the amp chips circuit alone starts looking like a small addition for effect.
  These chips [IIRC] don't exactly state the detailed rules of the games:
  Find the transformer, find the filtercapacitors, and whatever else you want with it.
  http://www.parts-express.com/wizards/searchResults.cfm?searchFilter=POWER+SUPPLY&srchExt=&perPage=25&sortBy=1&layout=LIST&page=1&srchPrice=&srchCat=&srchMfg=&srchPromo=&srchAttr=
  I got the PS4KX Ripple Free regulated for a Pyramid Blue amplifier [same place]. 12V @3amp seems to work [2x35w Ch.], it's nice to have clean power around.
     

[waltk]

If you want to avoid special power supplies, you might want to consider going with a chipamp intended for car audio.  There are a boatload of these out there, and they work fine off of a common 12V wall wart.  I've had good success with TDA2005 and TDA7240 amps.  All you need is a simple buffer and tone control in front of the standard circuit referenced in the datasheet.

Here's one I made with a TDA7240 that cranks out a ridiculous amount of sound for its size:

[Taylor]

Ah, great idea, I will check those out.

[R.G.]

From physics: Power out = power in - losses

Skipping about three pages of math, a solid state class AB biased power amp (all the chip amps are this except the class D switchers) can be no more than 78% efficient, roughly, so you have to supply them with DC power equal to at least power out divided by 0.78. More if it's not a perfect amp, and no amp is. A 2030  running from 36V needs a couple of amps of current from the power supply.

A perfect power supply converter (if that existed) would convert power at 100% efficiency. So if it's 36V at 2A, that's 72W of DC out, so you'd need at least 72W of DC in from your 9V supply. That's 72W/9V =  8A. And since switching power supplies are not 100% efficient, add about 15% for losses. Call it 9.2A out of the 9V power supply.

A voltage multiplier to convert 9V up to 36V at 2A would pull over 9A of 9V. So the common voltage multiplier chips are not even close. The common charge pump inverters amount to about a 40-80 ohm resistor in series with the single-conversion voltage. On average, each additional multiple would add another equivalent series resistor. So quadrupling (roughly) 9V to 36 would make a charge pump chip of the normal sort look like a 36V supply with 160-320 ohms in series, and there is no way to pull 2A from that. Even a 1A drain through 160 ohms would drop 160V. That is - you can't get there with a charge pump chip. Maybe 100 of them pumping in parallel. Impractical.

As a practical matter, you need to either lower the target power supply to fit a commonly available 24Vadapter, go for a bigger and less available adapter, use a prepackaged power supply, or somehow otherwise figure out where you're going to get all that DC power.

[davidallancole]

Is there any wall warts that are cheap enough that just have the transformer in it?  Then all you would need is the fuse and rectifier/caps in the chassis.  You could make a powersupply board to go along with the TDA2030 pcb.

[frequencycentral]

So it would seem that DC voltage multiplication won't get enough current. What about using a 9v AC wall wart, with cap/diode %^&*croft Walton voltage muliplication and then rectification to DC? Would that get enough current, providing the AC wall wart is putting out enough juice to start with?

[Nasse]

Lead acid batteries are not cheap, but would deliver the current. Portable guitar amplifier...

Idiot proof and simple charging and protection of batteries from goin deep down might not be so simple and cheap

http://mycaramplifiers.com/wp-content/uploads/2009/01/200watts-amplifier-300x208.gif I have a pair of about similar amps done on elektor pcb some 25 years ago, it has an arrangement it can work with symmetrical or single supply with no output caps if i remeber I used it down to 12 volts

http://mycaramplifiers.com/tda2030-amplifier-circuit-47.html few circuits and pcb patterns taken from elektor perhaps

[R.G.]

The reason I started my reply with the physics reference is that you have to remember that Mother Nature is very jealous about the conservation of matter and energy. And for us mere mortals without nuclear or relativistic reactions available to us, that contracts to conservation of energy. You have to put into the box as much energy as you take out, plus some more for any waste heat the box produces. Period and end.

So if you want 0.9W of power out, and you are using 9V as a power source, you simply must put in at least 0.1A of current, and you only get down to that current if the box is 100% efficient. A class AB linear amp can't be more than 78% (about) efficient theoretically, so you have to put in at least 1.15W to get 0.9W out, and that means that the 9V supply current will be 128ma. In addition, if you can't use the 9V directly, but instead have to put it through an up-verter, you pay for the up-verter's waste heat as well.

Charge pumps are good, but limited in current. It's not obvious, but a %^&*croft-Walton multiplier is a charge pump converter, just built using diodes and caps instead of an active switching circuit. You lose one or two diode drops minimum from the voltage you pump up for each stage you add. That loss comes out as heat in the energy equation and a lowered output voltage at the voltage output end as well. The more stages of multiplication you do, the higher the input currents get. for a fixed output current. It's not possible to NOT pay the conservation of energy price.

About the optimum thing to do in this vein is if you must have 36V out at some substantial current, you can use a transformer powered doubler.

To get to 36V dc, you need a peak AC voltage being rectified of 36Vdc plus a couple of diode drops, for about 37.4V, and that is then divided by 1.414 to convert peak voltage to RMS, and you get 26.449... volts AC needed. Hey! That's close to 24VAC! What if...

A 24Vac transformer produces 33.936V peak, minus a couple of diode drops for the rectifiers, giving 33.9Vdc before capacitor ripple. Capacitor ripple is whatever you want to make it by how big your capacitor filters are. In reality, a 24Vac transformer, probably puts out 24Vac at full load, and closer to 26-27Vac at no load.

So a 24Vac transformer is almost exactly right for getting 32Vdc, even with losses. It is probably impossible to hear the difference in sound pressure level between a 2030 powered by a 32Vdc supply and a 36Vdc supply.

If it were me, I'd find a 24Vct adapter good for an amp or two and have done with it. Otherwise, a designer on this is going to have to do some clever energy budgeting and power supply up-verter design to get the thing to run from 9Vdc.

[earthtonesaudio]

While you could not build a DC amplifier with (power out) > (power in), you could build an audio amplifier with (peak power out) > (average power in), as long as the average power out is less than the average power in.

The key is storing the energy from the power supply in reactive components to be added to the power supply *only when you need it*.  For this you'll need to go to class G or H amplifiers, and those can be quite difficult to find.
For example this vaporware amp claims 100W output from 4 C-cell batteries, for 360 hours!
There are more obtainable examples of class H? amps that use bootstrapping to achieve high temporary output levels, particularly in car audio.

For a "forum project" however, I think you would have better results choosing something simple and proven, like the 24VAC transformer RG recommends.

[waltk]

I'm sticking to my earlier suggestion to use a chipamp that only requires 12V, and thereby avoid higher-voltage wall warts that might be relatively pricey and difficult to find.  Here are things that I've actually done and work well...

1. Pick a chipamp designed for car audio.

2. Because high-current wall warts are difficult find and/or pricey (even for 12v ones), buy used laptop power supplies on ebay.  These typically put out 14-20 volts (depending on the laptop they are intended for), and can support current draws between 3.5 and 7 amps.  My favorite so far is one intended for particular IBM laptops - 16 volts/7 amps.  So that's over 100 watts - more than sufficient for small chipamps, even after you regulate the voltage down.

3. Powering these small chipamps with a battery is absolutely doable (if that's what you prefer).  You just have to pick the right battery.  I have used 18-volt lithum batteries that are for my drill very successfully.  They're rechargeable, light weight, and have a high engery density.

Here's an example of a cigar-box amp complete with a TDA7240 chipamp, a BSIAB2 for the pre-amp, a scavenged reverb pedal, and the battery.  Just plug in to a cab, and it's good to go for hours of playing.

[tuckster]

Someone in another forum told me that TDA1562 has an integrated load pump.
http://www.datasheetcatalog.com/datasheets_pdf/T/D/A/1/TDA1562.shtml

I ordered a switchable notebook psu 15-24V for ~25€ because I already had a TDA2040 (I wanted to build TDA20x0 from ggg) but then I was told that pic.12 (http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf) should be the better one with a single supply no messing around with bipolar supplies.

[davidallancole]

Because of the power supply involved here, its not going to be as cheap as or necessarily as easy as a 9V battery or wall wart.  Thats just the facts of it.  If you want to make it easy for beginners, you could design the pcb to include the fuse, rectifiers and caps all on it.  Then a person just needs to wire up the transformer to the PCB.

[Taylor]

I think waltk's idea is probably how I'll go. I could possibly buy a bunch of laptop supplies in bulk to sell with the boards.

[petemoore]

  if batteries are to be used as PS and higher voltage is desired, a series of batteries adds, 3x9v = 27 [quickly and fairly painlessly, other battery options are available], and will be more effecient [since the single 9v will need replaced more than 3x as often, given that the components used to create higher voltage aren't perfectly effecient]...basically you'll get more power out of three batteries than 1 battery 'multiplied'.

[Brymus]

I agree going with a car chip amp makes it easy.
I powered my project with 8 rechargable AA batteries.
Lasts a couple of hours at drum usable volume.
Also even Radio Shack sells 12V transformers for about 10$ .
I understand you want to keep people away from mains wiring but,hooking up a transformer and a couple of diodes isnt really that hard.
You are gonna need a couple of amps too.
BUT going with the car chip amp it is easy enough to use rechargable batteries for those afraid of mains wiring.
The TDA series are easy to impliment,take pedals and preamps well.
And are super cheap at the right places> Tayda ,Apex Jr,ect

Here is my practice amp design(using batteries or transformer),also my first contribution to the forum complete with sound clips and schematics.
http://www.aronnelson.com/gallery/main.php/v/Brymus/TDA1519b_386AMP/

But on the other hand going with a split power supply of +/- 18V is what powers most commercial practice amps in the 10-20 watt variety.
Here is one of my favorites using a TDA 2040 IC http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=43535&g2_GALLERYSID=f8218711e5b6bfd6b12f74051ff484f9
IIRC the TDA 2030 would swap right in.
I have several amps (like 100s) in the zips I dont remember if they are all tube or SS though.http://www.aronnelson.com/gallery/main.php/v/Brymus/Schematics/

You could always check out ChipAmp.com they have lots of kits for the DIY ,and see how they treat the mains wiring issues.
Also GGG has PCBs for chip amps IIRC

It would be nice to see a good amp project ,that Aron could stock ICs (and other parts) for,I think that would help the store.

[Nasse]

TDA2030 is tempting because there exists lots of stories about it´s good distortion behaviour. Or perhaps some other chipamps are not so good, I mean nasty clipping, or have that magig non mojo "tired transistor tone"

Was thinkin about those applications where two 2030s push opposite phase to get more from low (car battery) supply, perhaps for guitar the drawbacks of dual arrangements do not matter but what does it do to distortion when pushed? Never tried my 2030 amps at full blast 

I have these "200 watts" amps and what amazed me was cheap parts just ordinary caps and resistors, no high power resistors on board  or electrolytic caps in series with speaker, and that version I have, is done so that you can use dual or single supply without any modifications to the circuit, plus a range of supply voltages appcepted

[Taylor]

I have these "200 watts" amps and what amazed me was cheap parts just ordinary caps and resistors, no high power resistors on board  or electrolytic caps in series with speaker, and that version I have, is done so that you can use dual or single supply without any modifications to the circuit, plus a range of supply voltages appcepted

Can you give a little more info on that? Is that a commercial thing or something you built?