Voltage multiplier for TDA2030?

[Nasse]

That was some Elektor circuit published 25... 30 years ago. I believe that supply voltage middle point circuit is such that low current only goes trough it, and done with two resistors. Must dig my "archives", perhaps could find the magazine

EDIT still not find the magazine got few hours sleep

but googled this http://www.eleccircuit.com/power-amp-super-bridge-120w-by-ic-tda2030/ which pcb is copied from that Elektor article, schem is sgs application. Must verify that schematic, those two 2,2 k resistors drawn wrong perhaps...

That another transistors boosted sgs application with  and E*****r pcb is nice too, about 40 watts and simple might be nice for practice amp http://electroschematics.com/103/40w-audio-amplifier-tda2030-bd712-bd711/

[Lurco]

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

july/august 1984 circuit #20 ? or a TDA7370  project? And whatever happened to the LM12 from NatSemi?

[Nasse]

"july/august 1984 circuit #20 ?"

Can´t say which number it was, perhaps not summer circuits collection but whole story few pages though basically it is mostly same, only pcb added and legthy info about power supply and current needed versus supply and speaker impedance, how to connect preamp when dual or single supply,  etc etc. One thing worries me I never matched the transistors but dunno if it really matters. Sound quality is "pleasant" but not such punch and clarity and tight bass damping factor as LM3886. Once when kids where young and they had school disco I played a subwoofer for four-five hours as loud as I could, and it did not get that much hot. Only one small electrolytic cap dunno if it is aged or not, should be easy job for me to get those workin some day

TDa7370 is another car stereo chip, among many others new and perhaps better that other people suggested. I have done two, simpler than simple and solid as rock bulletproof performance, it might be something like 2 x 17,5 real watts with single 12 volt supply, something like 4 x 2030s on one chip, component count was low

[Lurco]

It was the february 1986 edition. The connection of the two 2.2k resistors R8 and R10 indeed needs to be connected to ground in that googled article you found ( http://www.eleccircuit.com/power-amp-super-bridge-120w-by-ic-tda2030/ )

[Nasse]

Perhaps few dots missing here and there on that schematic, layout seems right what I have. I was reading tda2030 datsheet and there was that bidged circuit with split supply no extra transistors...

I was watching nightmares while sleep and thought if those circuits would be closed in a box and have puppies, would it be possible to just have bridged circuit without those trannsistors, but with that dual or single supply option and without output cap, perhaps if just leave off those transistors...

[PRR]

The problem is that you want POWER and most wall-warts and volt-boosters only give power.

Use 12VDC power and car-sound chips.

Higher voltages with large power are hard to source except by pot-luck. (I have a 36V 0.9A desk-lump here but I could not find another if I needed it.)

Car-sound chips may be fairly simple, are optimized for efficiency.

The major drawback is that to get good power in speaker impedances with just 12V, we use two amplifiers (may be one chip) and both sides of the speaker are "hot". This conflicts with the guitar-amp custom of using a 1/4" grounded-shell jack for speakers. You may insulate the jack (the all-plastic jacks are fragile but self-insulated) from chassis, use a plastic/wood chassis (only the preamp stage needs metal sheilding), or put a proper connector on the amp (SpeakOn is good but expensive) and appropriate cable.

Most car-sound chips, if a speaker line is shorted to ground, won't blow-up but will shut-down politely. However this may be hard for some users to diagnose.

12V DC supply in a bridge-mode amp will put 8V RMS across a load. This is 8 Watts in 8 ohms or 16 Watts in 4 ohms. (You see higher numbers on some sheets, 18W 22W even 24W; they use 14.4V power and crank past clipping level to get a 10% reading on the THD meter. This is specsmanship. There's really only about 10% power-output difference across all the car-sound chips, and that extra 10% requires large bootstrap caps.)

20 Watts output will need 30+ watts of DC power. Your 12V supply must be rated 2.5A-3A. This probably won't be a wall-wart.

Regulated is not essential. The carsound power chips have good power-junk rejection and will tolerate 16V (often more if it sags when working hard).

This 8W-22W is more than a Champ or Junior, but will not replace your Twin or SVT. If you want a BIG amp, you just have to play Sparky and build/recycle power-amp power supplies; what we need isn't really used in any other electronic boxes.

The carsound chips usually give a gain of 100. For 8V out this is 80mV in. You would add volume and tone control here. For 20dB tone loss you need 800mV into the tone control. For 20mV input sensitivity you need preamp with gain of 40. Since guitar inputs can be as hot as 500mV, and gain=40 gives 20V out of the preamp, and you can't do that with 12V supply, your preamp probably wants to be variable-gain. Say 5-50. You might plagiarize commercial small-amp plans for known-good low-volt preamps.

You probably can't build this for less than you can find 10W-20W amps in pawn shops. You can't approach the economics of MASS production and marketing. And 1980s-1990s transistor amps may be easily modifiable or re-packaged. If they have a few busted knobs and jacks, so much the better: you would replace them anyway and the as-is price is lower. But there is some fun in roll-yer-own, and then you KNOW everything that is in there and how to change it.

PS --- Jameco 24V 1.2A 28.8W Part no. 139096 $15 is another possibility. You may use a non-Bridge chip (such as the ever-popular 2030) with output cap and grounded speaker jack. Non-Bridge on 24V is about the same power as Bridge on 12V, still 10W-20W. The preamp gain is not so critical. Jameco suggests you can buy 500 of them, but I don't know the long-term availability. And with some design care, you could run the amp on 12V 1A wart or car/drill battery for 2W-4W output.