Crazy idea ! - thyristor amp

[Nysan]

Had a crazy idea about building an amplifier that worked with
+-230 V DC rails.
This would be done by operating thyristors in their "linear"(far from it) state.
This obviously would sound like **** if not a normal speaker will be used (and destroying it in a nice way).
The aim is to find a suitable mass of the moving part of the speaker to cancel out some disturtion.
The thyristors are probably not as fast as I want them, thus this
channel would have Low Bass Amp properties.

I am obvioulsy not an audiophile, this project is all about the Watts.
Do you think it is possible to make?, maby someone has already done it?

/Dave

[Snokker]

Hi Dave,

An original idea. Before you start building take notice of the fact that a thyristor won't switch off once it is triggered. For that you need an GTO (gate turn off thyristor). If you should manage to switch off on time by a negative current it would not be capable of playing music above some kHz due to the spreading time, recovery time etc.
For simple amplifiers try tubes or Power fets on 230V!!

[johnnyx]

You need an extra set of thyristors to turn the main ones off. Years ago, inverters for industrial ac motor control used thyristors, generating 3phase ac. Now they are still used for dc motors, inverters use IGBT or bipolar modules. You could make a switching amp, ClassD, but I suspect the switching frequency would be too low. They're fast, but not that fast. I've often thought about making a power amp using industrial bipolar modules. One module for several kilowatts of power.

[gmarsh]

If you can find a way to operate a thyristor in an any sort of linear region, I'd be impressed... I'd sooner build something like that using IGBTs, but it sounds like you have quite a challenge on your hands

[Nysan]

Thanks for your thoughts.
You are probably right that a better approatch(spelling?) would be to use Class D.
But I dont think driving the thyristors in the "linear" mode is
impossible, just close to impossible.

/Nysan

[ClassD]

Yep, there should be no problem making a class D amplifier with 230V rails. You could easily get MOSFETS that have a high enough voltage rating. IGBT's could also work, but MOSFETS would probably be a better choice for the high switching frequencies of the class D design.

[Circlotron]

Originally posted by gmarsh
If you can find a way to operate a thyristor in an any sort of linear region, I'd be impressed... I'd sooner build something like that using IGBTs, but it sounds like you have quite a challenge on your hands

A thyristor (specifically an SCR) does in fact have a fairly ugly linear region from zero to 100mA or so, depending on it's size. Beyond this current the device will latch on as it is supposed to do. I did once see a circuit for one being used as a high voltage transistor.

Short answer - a thyristor is really no good for an audio amplifier. A pity really, because I have seen some rated at 4500V, 5500A