It has taken us some extra time, but we finally got round to measure the Le Monstre Deluxe as well.
This has original transistors, all TaN resistors, including Shinkoh for the 220R in the feedback network, RA12P trimmer, Riedon 1R 35W thin film, etc.
As described in the article.
View attachment 1317284
The surprising thing is, that H2 & H4 are ~20dB lower than the previous prototype using same active devices.
So what has changed ? 20dB less even harmonics cannot be just due to the passives.
Well, the JFETs used in this were matched at Id with 50R source resistors, instead of at Idss.
They also happened to have quite close Yfs at that current.
On top of that, we used the current source bypass to keep the 1k drain resistors and 0.7A bias.
So the trimmer was almost at its mid-point when DC offset is trimmed.
And now you get near perfect even harmonics cancellation from top and bottom halves.
And
maybe the higher bias with the original output devices also contribute to some extra distortion.
Just tells you that no two Le Monstre's can be exactly the same, unless you measured every active component upfront.
Cheers,
Patrick