Re: 4000 watt Audio Amp to drive Tesla coil (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 11 Sep 2007 08:34:11 -1000
From: Chester Lowrey <hilo90mhz@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: 4000 watt Audio Amp to drive Tesla coil (fwd)

Car audio amps do have DC-DC SMPS that take the 12V up to +/- 50v or
something about there... ive worked on a few of them... So the 128V needed
to drive a 4 ohm load isnt unbelievable..

I still dont think this is a very viable option as they are two completely
differnt goals.. the audio amp is NOT designed for this..

and what about the 20KHZ bandwidth that of the amp? not to mention that it
probably cant deliver near full power at 20khz as you usually want all the
power for bass.. infact if this is a subwoofer amp it would be pretty
hopeless

Id say build something from scratch.. but then its easy for me, but can be
fun to learn if you aren't already proficient in electronics.

Good luck and if you do go for it id love to know what happens..

Chester

On 9/11/07, Tesla list <tesla@xxxxxxxxxx> wrote:
>
>
> ---------- Forwarded message ----------
> Date: Mon, 10 Sep 2007 21:48:20 -0700
> From: Jim Lux <jimlux@xxxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: 4000 watt Audio Amp to drive Tesla coil (fwd)
>
> Tesla list wrote:
> > ---------- Forwarded message ----------
> > Date: Mon, 10 Sep 2007 10:57:28 -0700 (PDT)
> > From: Timka <tomasdoc2002@xxxxxxxxx>
> > To: tesla@xxxxxxxxxx
> > Subject: 4000 watt Audio Amp to drive Tesla coil
> >
> > Hello all,
> >
> >   Did anyone ever used and audio amp to drive Tesla coil before?
> >
> >   I came across a few mosfet amps on EBay, new but relatively cheap. The
> one I was looking at is rated at 4000 watts bridged output into 4 Ohms load.
> Now, I figured if I would use copper tubing, the resistance wouldn�t be a
> major factor after all.
> >
> >   Another good thing is that I can feed anything into it via signal
> generator or even audio to see how coil behaves.
> >
> >   Now, nasty things that I worry about:
> >
> >   1) It would really suck if I ended up blowing final mosfets due to TC
> secondary kick back and frying internal circuitry, which would be a total
> fiasco and probably would puzzle a lot of clerks at the return department.
> Ad states that amp employs overload protection but whoever designed them
> back in China never envisioned a million volts kickback from an ordinary
> speaker, so I'm not holding my breath there. Any suggestions here?
> >
> >   2) What kind of power supply is needed? In a car amp works off
> alternator and use around...... around a lot of amps! In fact, not every
> alternator can pull a 4000 watts amp as the most of them is in the area of
> 120 amps on average. Here is quick math for 4K watts amplifier:
> >
> >   1 channel with 4000 watts RMS per channel doubled to the account for
> amplifier inefficiency (4000 watts X 2 = 8000 watts), then divided by the
> average output Voltage of an alternator, 13.8 volts (8000 divided by 13.8= 580 amps). Since the average signal requires about 1/3rd of the average
> power in a tone used to drive TC, dividing by 3 (580 amps divided by 3 = 193
> amps). This is the result of the amplifier's approximate average current
> draw.
> >
> >   Soooooooo, how and where in the world do I get a source of 200
> constant amps at 13.8 volts? This is not your average power supply you can
> plug into a wall. I was thinking of getting a car booster/starter a.k.abattery charger, it's the size of small fridge, with 2 fat clammed cables,
> weights about 60lb and probably employs a very large transformer you can use
> to kill your mother in-law that can be plugged into a wall. Another ad
> claims that this car starter can give an instant 300 amps surge or so but
> how about using it for longer than instant or lets say 10 min? Can it pull
> this amp? Of course I can add a few 2 farad audio caps in between, but would
> it be enough?
> >
>
> You don't.. 4kW RMS is probably a bogus spec. (something like "peak
> music power", which has no real meaning)  For one thing, to put 4kW into
> a 4 ohm load takes, let's see.. P=E^2/R 4000*4 = E^2 ->
> Vrms=sqrt(16,000), or about 128 V.
>
> If you buy a "real" multi-kW audio amp, they tend to run off 120 or 240V
> supplies at tens of amps.  Check out the products from, e.g. Techron or
> Crown.  I have a couple Techron 7560s at work, and they're a pretty
> beefy unit.. rack mounted, about a foot tall, etc.  They'll comfortably
> put out a couple kilowatts at 120V, and you can bridge them.  They're
> basically a giant power op amp.  We use them to do things like drive big
> voice coil positioners on shaker tables, simulate power supply
> transients, etc.
>
>
>
>
>