Don't get too preoccupied with distortion figures, they are notoriously not great as a measurement of an amplifier's goodness.

the other interesting point on distortion, that I learned during this amps design phase, was the significance of "inaudible" elements.  Frequently Owen would pick up a distortion component in the audio band that he couldn't identify the cause of , only to see it mirrored at much higher frequencies (I am fairly sure he said megahertz), and fixing the cause of the distortion at frequencies way above the audio band, eliminated the "ghost" distortion in the audio frequency.

Yes I agree with all the above posts, very interesting to have the designers input.

James

I'll be round at 7 if that's still OK - with Pip and "little shoe box".  You didn't seem very familiar with my new (borrowed) toy so maybe this will be of interest 

Benchmark AHB2

(Although clearly the author and I have a different interpretation of the word "poor" - £3000 is still a lot of bucks for me)  Is it a rude question to ask what it cost you to build your SECA?  I see the one it is replacing retails for around £5000

Please report guys Have a good session

It's the comfy cushion that you have to be afraid of

Pinkie. There is no crossover region in a SECA so crossover distortion is zero. The main disadvantage of SECA is no ability to move into class A/B and so it can't deliver more power into lower load impedances. As Colin quotes 40W into 8 and 61W into 4 it must have been designed to have sufficient standing current to give this output into 4R. It is a brick wall current limit usually though. Not that any of this need be an issue if you don't have awkward speakers or if they are efficient enough to be nowhere near clipping the amp at the listening levels chosen of course. As it has a huge damping factor there should be no loss of control/grip into any impedance up until it clips though (probably about 28W into 2R at a guess).

Can we have before and after piccies please

BTW we have windows

Well, Richard has just left, and for those who haven't met him he isn't really pink as his Avatar name suggests.
Had a good time spinning tunes that we both knew and talking only when we had to    We listened to a mixture of Sting, Santana, Christian Mcbride, David Midgen, Adele etc.

Since I fried my LDR, don't ask, I have been using a TOCOS carbon pot to attenuate between my DIY DDDAC and the 40W SECA.  After fully settling into the groove of the evening Richard and I striped out the carbon pot and put in his mains powered Pip passive pre amp into the system; you can see it on top of the silver TQ Amp.  At first I thought we had lost something, then I soon realised that the Pip had pulled the sound together helping the bass integrate with the mid range and the treble and to present a more cohesive presentation, nice piece of kit there Richard. 
After a bit more chit chat and a few more tracks Richard put the smart looking new Benchmark amp into the system in place of the SECA, as he said just about the size of a shoebox which we sat nicely on top of the Pip.  How did it sound? Well very good indeed! It gave us good separation, detail, drive, speed and a sense of air.  But we did loose the palatability of the SECA amp, the texture and the tone.  The Benchmark was brilliant, and I loved the tight punchy bass notes but you didn't get that big deep wallop of the SECA or the rich tones or the huge presentation presented by the SECA but the Benchmark is a very clever amp and not harsh or bright in any way at all. Horses for courses I guess.  One thought I had which I mentioned to Richard is that the broad and deep bass that the SECA gives really causes the speakers to pressurise the room leading me to think I absolutely must acousticaly treat the room, because the whole room kind of reverberates.
A good evening none the less.  One which we should do again before Richard emigrates to France, but lets see if we can get John and Steve to attend.