Tocoi

Insanity Can Be Yours [pic]
1,500W / 4 Ohms Power Amplifier
Rod Elliott (ESP)
[pic]
Introduction
This project is mainly in answer to those for whom no amount of power is enough. I have lost count of the number of times people have asked if it's alright to increase the supply voltage on every circuit published, and in general the answer is no - it's not alright. Every design on this site isoptimised for the stated power. There is always some flexibility, but you must be very careful to make sure that transistor safe operating area (SOA) is not exceeded. There is also a maximum voltage for any semiconductor, and devices must be selected to ensure they are used within their ratings.
While (lateral) MOSFETs offer some real advantages, they are relatively expensive, and difficult toobtain with voltage ratings above 200V. Vertical MOSFETs (e.g. HEXFETs and the like) are a possibility, but suffer gross non-linearity at very low currents. Therefore, a relatively high quiescent current is needed, and this makes heat removal that much more difficult. There are other issues as well, but a discussion of them is outside the scope of this article.
|WARNING|
|This project describes an amplifier, power supply and tests procedures that are all inherently dangerous. Nothing described in |
|this article should even be considered unless you are fully experienced, know exactly what you are doing, and are willing to |
|take full 100% responsibility for whatyou do. There are aspects of the design that may require analysis, fault-finding and/or |
|modification. |
| |
|By continuing to read this article and/orcommencing work on the project, you provide your implicit agreement that ESP shall be |
|held harmless for any loss or damage, howsoever caused. You accept all risks to life, limb and finances (this will be a very |
|expensive undertaking) that the project may present. ESP accepts that there may be errors and/or omissions in the text and |
|diagrams that follow, and you accept that thesebecome your responsibility should you decide to build the project. |
|No assistance whatsoever will be provided for this project! If you ask me questions about it, they WILL NOT be answered! |


Capable of 2kW peak and a minimum of 1.5kW continuous, it has to be said that this amplifier will blow up any speaker connected to it. Regardless of the claimed power that variousdrivers can handle, they can't. To put this whole issue into perspective, take the most powerful and robust driver you can (8 ohms), and connect it directly to the 110V mains (I recommend this as a 'thought experiment', rather than actually doing it!). 110V RMS into 8 ohms is 1,500W. How long would you expect the speaker to last? Most will be toast within perhaps 30 seconds or less! A very few willlast slightly longer, but none will take that level of abuse for more than a few minutes.
I strongly suggest that you read Power Vs. Efficiency before continuing.
Have a look at the voicecoil of any speaker. Imagine how hot it will get with even 100W of continuous power - feel a 100W light bulb - 100W is enough to make any small mass get very hot indeed, very quickly. 1,500W is an awesome (scaryeven) amount of power! Look at the size cable needed to carry 20A, then look at the wire size used for the voicecoil. If you don't see a real problem, then I suggest you abandon electronics take up flower arranging as a hobby.
It must be understood that this is a 'brute force' approach, and that much is deliberate. Although it would be possible to use more finesse in the final design (such as...