Best amp possible for the hd-650

[jcx]

the "meter jockey's" at least have a goal, means to achieve it

but looking a "musical" amps - there isn't any consensus, any universally accepted formula, for every "x % n_th harmonic is good, y% m_th harmonic bad you can find other tweak audiophile designers doing it the other way 'round
easy to find highly praised amps with cheap iron, bad tube bias choices - apparently just because the amp uses tubz– and plenty of “subjective” reviewers willing to praise anything with the right “story” – regardless of whether the hardware in question actually physically behaves as described

serious artists do spend years mastering their palettes – when tweak audiophile designers start talking n-th order Volterra Kernal hypersurface shapes, profiles I might give them some credit

 

[abraxalito]

the "meter jockey's" at least have a goal, means to achieve it

Indeed they do. They just tend to ignore evidence that points to that goal not being correlated with SQ.

 

[jcx]

the meters we can easily read with today are actually the same Flagship ADC chips used in the studio to "meter" the music -the very same ADC chips that turn microphone V into sampled data

hard to make a case for the same ADC chips somehow "missing something" when connected to a amp for test when the same
ADC chips are used in the recording process

 

[chris719]

composite op amp circuits can beat that - I couldn't see any 1 kHz IMD product in one of my multiloop circuits with 10+11 kHz 1:1 with test signal fundamental removal arrangement and 30 dB amp ~ -160 dB resolution floor with 100 s averaging - did have to replace NP0 caps with polystyrene

so basically unmearurable distortion from active parts is possible - then care in passives part selection and layout of course

Quick OT question, where do you get polystyrene caps in the US still, are you using the Xicon from Mouser?

 

[jcx]

junk drawer 25+ yr old stock

haven't bought any recently but when starting on a BOM for a new design I came across LCR

LCR Capacitors - Capacitors and EMC filters seems to have parts in US distribution

make extended foil too

http://www.lcrcapacitors.co.uk/2011-pdfs/polystyrene/fsc-ex.pdf


the NP0 were good to ~-110 dB distortion, at a AP “Analog Master Class” seminar Bruce Hofer seemed surprised my measurements of NP0 were so bad - may go with brand, possible termination problems with my AVX thru hole parts rather than NP0 dielectric performance limit

I will simply quote the results from Samuel Groner's thesis.

Distortion of capacitors at +20dBu on the capacitor, 1kHz

Polysyrene LCR components FSCEX 10nF - no visible harmonics above -153.4dB noise floor (none nada zilch)

Vishay MKP1837 PP film - same

Vishay COG/NPO - same, noise floor -142.5dB (ceramic BTW, this was 1nF which I assume is why the noise floor was higher)

Dick, I'm not being a trouble maker and I'm asking nice could you please show me schematically how to put a sine wave through a C with rectifying defects at the input to get the cancellation of distortion.

 

[31697B]

The issue today - not back when electrolytics were commonly used as coupling caps... even mylar were a lot better. Today, film caps are the norm. Thanks to someone named Marsh and Jung. [] BUT, the problem of high capacitor distortion is still with us with filters... active or passive... where there IS a large voltage drop across the caps. Filtered used in removing noise or in crossovers etc. Or in the feedback networks of amps or used for compensation. There we are still dealing with voltage drops across the cap and so the best films are needed in those places/apps.

Thx-RNMarsh