Car audio amp for powering ultrasonic signals?

[FirePhage]

I'm wondering if one can modify an off the shelf car stereo amplifier to power ultrasonic frequencies? The output would need to be clean, adn as noise free and distortion free as possible, of course. Would it just be too much work? or is it a fairly simple mod?

As you've probably guessed, i'm not particularly strong with my electronics knowledge, but I'm getting better as fast as I can, so don't hate on me! lol Also, you don't want to know what i'm using it for- trust me. lol

Thanks in advance!
FirePhage

 

[KeepItSimpleStupid]

You really havn't said anything about the specs of the transducer, the voltages, power and frequencie(s) involved etc.

My home amp which is a version of this Leach Amp Plans - Part 1 could likely be modified for such use with only a couple of components changed. My amp does not have the VI limiter. Freq response is something like 0 to 800 kHz unrolled off. It's been intentionally rolled off to be from 0.5 Hz to 40 Khz.

It would be really tough to say any car amp or any home amp could be modified, but some MAY be able to. Changes involved would be to remove any filters or signal conditioning that affects the frequency response. Then the feedback network has to be modified. The amp had to have been designed for wide bandwidth use before it was intentionally rolled off.

 

[Mr RB]

Most of the modern amp chips will work well into the ultrasonics. I built a stereo map using LM3876 ICs and the standard amp configuration is good for 100kHz.

Sometimes they put a capacitor in the feedback circuit to roll the gain back at higher frequencies, so it may not be hard to mod an amp too.

 

[audioguru]

Many car amplifiers don't produce high audio frequencies so ultrasonic frequencies will not work.
The datasheets for TDA2003 and TDA2004 car amplifier ICs show a cutoff frequency of 15kHz which isn't even hi-fi.
A TDA2005 rolls off at 20kHz and a TDA7240A rolls off at 25kHz.

 

[FirePhage]

Sorry about the lack of info here. I'm not sure what transducer I will end up using. I was figuring that with my rather limited knowledge of electronics, I'd probably have to find a transducer to fit whatever circuit I ended up with. Thanks for the link to the leach amp plans- very cool.

As for the infor requested. I need an amp that can be powered by an automotive electrical system, and accurately put out an ultrasonic frequency up to 50khz (adjustable) with an output of roughly 1300 watts rms coming out of the transducer (that is, taking into account the efficiency and such of whatever transducer is used). And preferably at 1.2-1.6V.

It seems that the possibility of modding a audio amp may very well be dependant on the design of the amp itself, making the answer different from one model to the next. I figured this would be the case.

One thing I was wondering was the possibility of sending a single signal tone through an unmodified amp, and then using a 555 circuit or such to open and close the circuit to the transducer at the desired frequency- effectively giving me the high powered ultrasonic square wave i am looking for. Of course, the 555 circuit would have to be able to handle the high power load, and I'm not wondering if doing such would damage the amplifier.

Thanks again!

 

[audioguru]

1300W from an old linear amplifier uses 2200W. You will have 900W of heat to dissipate somehow!
In a A car's electrical system the alternator will instantly fry and the battery will boil since the DC current will try to be 183A!

You might find an ultrasonic transducer that can survive 30W. Then for 1300W you need 44 of them.
You are having a wild dream.

 

[Nigel Goodwin]

As for the infor requested. I need an amp that can be powered by an automotive electrical system, and accurately put out an ultrasonic frequency up to 50khz (adjustable) with an output of roughly 1300 watts rms coming out of the transducer (that is, taking into account the efficiency and such of whatever transducer is used). And preferably at 1.2-1.6V.

What actually are you trying to do?.

I'm with Audioguru your ideas seem totally impractical.

 

[FirePhage]

I know this idea seems impractical. But my calculations say this is what I need to get the job done. That job being electrolysis- converting water into hydrogen and oxygen for use as a fuel. Instead of a transducer, I'll be using electrically connected steel plates submerged into water. The resistance of the water can be controlled easily.

Thanks for the help.

 

[audioguru]

HHO for cars is a SCAM.
It takes more energy doing electrolysis that you get by burning the resulting hydrogen.
It messes up the air-fuel ratio which makes the engine run too lean so the valves and pistons get burnt.
Then the emissions is very high.

 

[FirePhage]

I didn't say anything about cars. I'm looking to make a replacement for oxy/acetelene torches and such as that.

 

[audioguru]

I saw a video of a plumber using a huge HHO machine instead of a little propane cylinder. It was powered by mains electricity.
They showed an HHO torch that has an invisible cool flame.

 

[FirePhage]

Yeah- cool stuff! HHO burns invisible, so extra extra precautions need to be taken with it, but damn, is it effective! lol I'm trying to make a more portable version of that kind of setup.

 

[Mr RB]

Why do you need ultrasonic frequencies? The output/efficiency of the HHO cell is based on plate area and conduction losses and frequency will have little or no effect on efficiency. DC will work best of all as you get max current all the time.

 

[FirePhage]

plate area, and other factors are part of the equation, but my research shows that introducing a harmonic at resonant frequency of the water will help with dissociation, thus increasing the efficiency.

 

[audioguru]

Water does not resonate. But in Google there are fiction articles about quacks making HHO by vibrating water at about 42kHz. One guy had it blow a hole in the ceiling and through the roof! Fog appliances vibrate water at an ultrasonic frequency and they don't make any HHO.

A microwave oven heats water by dielectric heating at 2.45GHz. Additional heating can be done by water vapour absorbing energy at 22GHz.
So the very low frequency of ultrasonics will do nothing exept maybe stir the bubbles of gases away from the plates.

 

[Mr RB]

Audioguru is very right about ultrasonics not being the "resonant" frequency of water, all of the stuff you will read about that is pure bunkum.

But you may get some improvement in plate clearance by vibrating the plates (and/or water) at an ultrasonic frequency. For the same reason an ultrasonic cleaner blasts dirt off surfaces the ultrasonics can blast bubbles clear of the plates giving you maximum free plate area for electrolysis. But please don't say this has anything to do with the "resonance of water" as you will lose credibility.

If you did want to use ultrasonics for plate clearance I would try a separate agitator to the plates, maybe something like an ultrasonic cleaner transducer to agitate the plates or water, and run the plate electrolysis from DC.

 

[KeepItSimpleStupid]

I've used a Hydrogen/Oxygen torch for quartz glassblowing We had to because of cleanliness and temperature. I do belive that the orifices have to be different than MAPP or acetetylene. It's difficult to see a pure Hydrogen flame and it's a more dangerous gas. We did have the tank outside and had a Hydrogen detector for the room. I've also used Oxy/Acetelyne, propane, Oxy/propane, Mapp, Oxy/Map and Hydrogen/Oxygen torches.

I also did electrolysis of water when I was a kid using the upside down test tube trick, a platinum screen for an electrode and water. Bottom line, it takes a lot of energy and it's slow. You'll also probably need to compress it to make it useful.

These properties: Flammable Properties of Hydrogen | eHow.com make Hydrogen less safe. I've also had to clean up from a spontaneous Hydrogen explosion in lab where it probably autoignited. I designed the auto-shutdown system for the lab and it worked as intended. The delivery system had to be re-designed after the blast. Not a scorch anywhere, but a powerful blast nonetheless.

You heard what happened in Japan with the reactor buildings and the build up of Hydrogen. Nitrogen injection is being used to lower the concentration and autoignition concentrations.

Electrolosis is impractical because of the amount of energy used to extract the Hydrogen. Electrodes and wires need to be made of corrosion resistant metals for purity and to prevent oxidation. A platinum screen is good choice.