Tír Na HiFi

*peeks in thread*
backs away slowly...

wushuliu wrote: ↑Wed Feb 07, 2018 4:37 am *peeks in thread*
backs away slowly...

From the project or the thread....

It's a little mad

nige2000 wrote: ↑Tue Feb 06, 2018 12:51 pm

ok when u get it back give me a shout

I did received the amp today, so when you have the time, we can do some tests. :)

Great work done today on reduction of noise/harmonics due to a modification by Nigel. The photo shows the results from Nigel's spectrum analyzer with a 1khz input signal and while the third harmonic can be seen at 3khz the second harmonic at 2khz has disappeared into the noise . The sound quality is much improved in both sweeter clearer treble and more distinct bass, loads more listening to follow.

Heres a pic i took of after

Wow, great clean-up in the noise floor - grounding changes?

jkeny wrote: ↑Thu Mar 15, 2018 11:53 pm Wow, great clean-up in the noise floor - grounding changes?

noise is pretty much the same, a little better but the second pic was an exponential average which shows the constants better or in this case harmonics

OK, averaging explains the squelching of the fluctuations on the plots
So what were your tweaks ?

have not tried mucking about with grounding while running a spectrum as of yet,
i did wiggle the output wire a bit seen nothing id imagine it might only affect input wires maybe
will be lots of uses for this handy device
glad i got it
still only learning the ropes myself so will take a while to calibrate for maximum sensitivity

jkeny wrote: ↑Fri Mar 16, 2018 12:35 am OK, averaging explains the squelching of the fluctuations on the plots
So what were your tweaks ?

i pulled this from a pass article for a ba-3
it is essentially the same for this revision of an f5

"P3 and the Second Phase
Potentiometer P3 is provided for those of you who have distortion analyzers or want to play
with the mix of second vs third harmonic. As with the F5 amplifier, you will find that you can
iteratively trim P1 through P3 for minimum distortion. I do so at approximately the 1 watt
output level (2.8 V). You should start out with the setting at the mid-point. The minimum
distortion point will generally be where the plus and minus halves of the amplifier balance to
such a degree as to null out the second harmonic. By introducing an imbalance you can
variably re-introduce the second harmonic, and depending on which way you turn the pot, you
can choose the absolute phase of the second harmonic.
I knew you would like a choice ;)"