PH 9.0X Details and Benefits!
This on our website, but I wanted to give the full details here also.
What the PH 9.0X upgrade includes:
The upgrade to the PH 9.0X involves the addition of a pair of Lundahl gapped output transformers,
commonly used in SET tube amps. The addition of these transformers also means the elimination of a
pair of chokes and coupling caps, all in the signal path.
Why this upgrade?:
The circuit change made to the PH 9.0X, make it much closer to the PH 150 in terms of overall circuit
design. Various other circuit differences in the PH 9.0 vs. the PH 150 were implemented, to see where
the PH 9.0 could be improved. Most either made no difference, or for whatever reason, did not sound as
good in the PH 9.0. This circuit change however DOES make a difference. The use of the Lundahl output
transformers was one of the cost cutting design changes made to the PH 150 to achieve the PH 9.0. I
found that the improvements were simply big enough that it warranted offering the upgrade, as an add
cost option for the PH 9.0.
Sonic Benefits:
The sonic benefits of this circuit change are obvious and significant! There is better bottom end, more
weight and authority to the sound as well as improved resolution, detail and soundstage.
Technical Explanation:
Eliminating the coupling caps simply cleans up the signal because no coupling cap sounds better than
the best coupling cap. This can be done, because the output transformers can absorb the DC voltage
present at the outputs that the coupling caps otherwise block.
The chokes are replaced also, as the primary winding of the output transformer serves the same
purpose, but does so with a much higher inductance, translating to better bass and performance.
