It didn't explode....... YET (aka niges amp)

[Derek]

Delighted it was an easy fix, we had to throw you a "deliberate" mistake just to test the system works.
I'm going to the suitably embarrassed corner now.

[nige2000]

Well it's easy enough to make mistakes
I've been looking into these a bit every day since monday
And i never seen it until the tell tale voltmeter said something was a miss

[Fran]

I did a bit of measuring tonight, just on one of the amps (will do the rest soon). I didn't have a suitable 8ohm resistor so used 10 ohm instead, but it gives a good indication. I measured 45w RMS into 10ohm and 73w RMS into 5 ohm. This is very close to design spec. These chips don't handle sub 4 ohm loads brilliantly, so we just need to remember that in the future. It won't do any harm (other get warm) but you will get a little breakup on peaks.

Fran

[nige2000]

right although the video i took isnt clear

i got my trios to clip at 20 and 50 hz at 18v peak to peak
their 4 ohm speakers
still even at that its plenty loud just below that without the possibility of a below 50hz clip
above 6ohm speakers will be a breeze to it

[nige2000]

this was 20-1k hz


little did i know that with the setting up i accidentally disconnected the bass driver
thats why there was no clipping up to 60v pp

[Sligolad]

After a long educational and interesting journey with many hours shared in pain and joy with the GB crew I am on day 1 with the one of the 7 amps.
This one is now finished and along with 5 more awaiting final reports, the final one is very close just awaiting some Volt meters.

I can make the first report on one of the finished amps and it looks way better than expectations and sounds better than i remember the prototype on first listen on my secondary system with Tannoys, Meitner and JPlay, that says a lot!
Will give it a day or two to settle in before pairing it with the main audio PC, Big7 and Raidhos.

Great work by Nige and the crew to finish this out as I believe everyone involved will agree it was much more work than any of us would have imagined....will think long and hard about the next GB idea but as always we will forget quickly and most likely jump at it again if the bait looks tempting.
Glad I jumped on this one as it has been a great journey and worth it in the end.

Thanks to Nige particularly for having the balls and determination to see this through.....it was worth it and I am sure it will be all positive reports from here on in.

[ho66es]

well done all of you!

[nige2000]

for anyone thats interested in measurements i ran a distortion test at 1khz 40v pp and at 20v pp (thats way way louder than you'll be listening)


by conversion thats circa 0.02% thd

not bad for amateurs i think

also would like to thank all involved as it was very much a group effort

really pleased the way alls worked out

maybe for next GB we will go with a lighter bite

After a good soak test 3-4 wks there will be an amp to lend out to tirna members to try out for maybe a week or two at a time

please register your interest here

[Ivor]

please register your interest here

Consider me interested. Purely academic of course! Maybe I don't want to hear it?

[Fran]

Well, I can tell you - if you are worried about listening to the amp, you definitely don't want to hear the DAC he gave me a lend of!!


Seriously though, its been quite the trip - I think we'd all say it took far more work and probably money than any of us thought but the end result is just fantastic. For what its worth, its now the best amp in my collection by a country mile - and I would have thought I have some nice amps here. I might also add that the distortion plot that Nigel posted above is pretty damn good for any amp anywhere - in particular, there are no harmonics anywhere in that spectrum, which is very unusual. The THD value is really just the noise floor of the amp - to put it in context, -72dB is the equivalent of about 4000x lower than the signal..... which is very indeed, even with the 40V under test here.

All in all, a cracker of an amp and we are very lucky to have one.

Thank you Nigel, and to all who took part.

Fran