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My experience is the opposite

Posted by DAK (A) on June 23, 2017 at 12:36:16

In Reply to: Initial A/B test between PP and SE 6bq5 amps posted by vinnie2 on June 23, 2017 at 06:07:41:

In my quest to verify the difference between the 2 circuits, se and pp. I built a power supply to power both a SE and a PP amp, thus ruling out the power supply as a difference. Then i constructed both amps of the same circuit which is the "RH universal" but for the PP amp i used a Lundahl input/splitter transformer which is, according to what i have read, the transformer splitter the most accurate phase splitter.
PP amp: EICO HF87 output transformers with 6sn7 driver. The split signal is fed into each 6sn7 section which is then cap coupled to the 6550 tube. This circuit uses local feedback only between power tube plate and driver tube plate. I also employed fixed bias to remove the sound of the cap and resistor from the cathode.
SE amp: Uses the exact same circuit except the rh amp with the only difference is the size of the coupling caps and the output trans which are Electraprint. This amp also uses fixed bias to enable tube and operating point flexibility.
Tubes used were the same for each amp. A quad of Sylvania 6550 with RCA red base 5692 as the drivers in the PP and a pair of the same 6550 and 5692 for the SE amp.
My Sonic impressions.
Both amps sound very good indeed. Everything you would like in the sound is there good bass, mid range to die for, and highs that go on until you can only sense it.
The Main Difference that i discern between the two is that there is an aura around the notes or sound of the PP amp. Just a little halo of something i can't really put it into words but this artifact is not present in the SE amp. The sound from the SE amp is more incisive notes or voices seem to have more space or bloom around them.
Conclusions: I was actually trying to achieve a better sound from the PP circuit with the use of the phase splitter. My reasoning was if i could eliminate more of the 2H, second harmonics, there would be more detail and low level information. In the RH amps that i built using recycled OPT from console amps or tape recorders, i found that the low level detail was obscured or inaudible. Kinda like Curt Kobain's singing.
I did not find that this was true and that both amps were not much different in low level information when equal output is observed. This lends me to believe that the output transformer quality is critical to achieving good low level detail from a SE amp. As always, YMMV

Edits: 06/23/17

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