I have no direct experience of the 606, and any in-built failure modes, such as there are with the 405.  But looking at the schematic, there is no output crowbar, which is good!

Most kind of you John!

I purchased the boards, and populated them myself, from www.signaltransfer.freeuk.com/ .  You can buy them ready built and tested, but you still have to be competent in DIY audio.

What you'd need is two Load Invariant or Trimodal (that you can switch between Class B, AB and A), plus a power supply board.  Then you'll need a suitable toroid to provide 45/0/45V DC.

The Load Invariant design in my set up produces 110W into 8 ohms and 180W into 4 ohms - provided that your mains transformer is stiff enough.  I went over the top with heatsinks - I specced them for continuous sine at full power indefinitely. Which means that they never get more than hardly warm at all at ear-bleeding levels.

Agreed. Bear in mind, though, that the active output stage of a beefy solid state amp is often subject to negative feedback so it will try to compensate for the back-EMF of the driver and retain control.

I've never seen them quote a figure for it, Steve. However, 16 power MOSFETs per channel would indicate a suitably low output impedance leading to high damping factor.

I think that is a non-sequitur Martin.  Paralleling devices improves the available current (assuming the power supply is up to snuff).  So such an amp will try to double the power output each time the driver resistance halves.  A practical amp never quite manages that for various reasons.  But I do not believe that parallel devices implies a low output impedance.  In fact it may actually be higher than an amp with fewer parallel devices.  MOSFETs are extremely prone to RF self oscillation, with explosive consequences (literally! Got the badge and almost the scar), and massive paralleling usually needs precautions to prevent this that can push output impedance higher.  Anyway, you can cheerfully get 500W plus into 8 ohms out of three MOSFET pairs using +/-90V rails.

Aha.  Hence so many FET's - the power doubling into each halving of speaker impedance.  Must have one hell of a PSU - you need a 3kVA mains transformer to pull that stunt, and a LOT of reservoir caps.

Edit: OK - just read the specs on Chord power amps.  Switched mode supply with 3-4kVA capacity.  All you need is £8k for the stereo one   . I shudder to think how much the SPM 6000MkII Reference mono power amplifier is that can throw out 3kW into 2 ohms.  Even a 2 ohm dummy load to test that sort of spec is not a cheap thing in its own right!

Yes yes, all this horse power is sexy:) but...
How the hell did John's 3kg Behringer do it so well allbeit only in the 20-90Hz range in my system - explain me that?

All the tech specs can tell you a great deal, except how it will sound in your system ?it will give you an indication of possible traits, unless you are viewing sideband graphs for dac frequency plots que AP or MAR system champions.

Power is nothing without control, yet so many amplifiers have superb control of drivers yet the music is total locked into speakers never free or open or articulate and therefore constipated in delivery ?

I have listened to many amplifiers over the years some with just two pairs of FET's sounding great and a couple of amplifiers with a couple with at least twelve pairs sounding damn fine as well

The key here is implementation of the design all aspects of the whole must be careful fully thought out.

Looking at amplifier speaker impedances to suit your system imho is more important towards improved sound quality than looking for 3.2kw@1ohm lol

Power supplies, stiff enough, quiet enough, storage capacity to cope with big transients , fast charging of the caps, short signal pathways, pre stage, band width, feedback which way to go?

Negative, closed loop, DC coupled , positive feedback, each has their benefits and draw backs, specific class, a, a/b d both fully digital or pwm switching, switch mode psu is toroidal heat dissipation, circuit boards, 4'6 or 8 layer?

Fully discrete, through hole, valves or integrated circuits (op amps' etc)

Will it pass CE testing,

Here's a thought the LDV covers up to 50vac any voltage over this is outside this spec to generate large power figures then as Craig has pointed out you are going to need to raise the rail voltages to +/-90v so the need to swing 180v is required which in reality takes your speaker cable out if the LDV and into CE approval

In all my years of designing and working with different companies with amplifiers some of the very best sounds have come from 80-120Wrms for solid state

We have not discussed on chip switching (lower power devices ) which doesn't suffer from the usual FET drawbacks though smaller power outputs limit overall design parameters


My suggestion for Steve would be a high bandwidth 100khz+ class d around 100Wrms to start with.

Having an ultra stiff, ultra fast, ultra quiet psu with ultra fast storage is no guarantee of a good sound but it helps a lot

One thing you forgot, TonyC, is the topology: Class A (very rare), Class AB (very common), sliding bias etc.

How much of your listening is done while in Class A is a very good question to ask.