Jean Hiraga Auditorium & Aquablue NEC Plus Ultra Amp

Photos from the event in the auditorium of Jean Hiraga with his big horn system and detailed information about the new SE amplifier Aquablue Nec Plus Ultra from Benny Glass – DIY Paradiso. This project has been simmering in Benny Glass’ subconscious for many years. In short, it is a DHT SE integrated amplifier that uses the latest technology and combines all Benny Glass acquired knowledge of the last ¼ century in one design.

What we have here is the Nec plus ultra, hoping to achieve a sound that matches the effort Benny Glass put into it.
Nec Plus ultra specifications: 
  • 71A-4P1L-300B 5 power supply transformers.
  • Lundahl choke, Audio Note choke 
  • Lundahl output transformers
  • Eichman speaker terminals
  • Current sources for preamplifier stages
  • Preamplifier driver tubes: Vintage NOS 71A Thoriated Tungsten filaments and Russian NOS 4P1L
  • Output tubes The revered Western Electric NOS 300B
  • All filaments are driven by current sources, which has many advantages
  • Tube rectified preamplifier driver section 
  • Tube rectified LC power amplifier section
  • Huge storage capacitor after the chokes
  • Wooden cabinet (partially)
For the input tube in the first version of this amplifier Benny Glass decided to go with the 4P1L, the driver is the 71A, though the positions could be swapped depending on listening tests and overall satisfaction.

The goal is to achieve the finest harmonics structure possible with vintage tubes because that’s what procures the magic. The signal-to-noise ratio is the other matter. Hence the sophisticated structure of the power supply.
The amplifier is 2x capacitor-coupled, with the possibility to go a very exclusive way, but for the first tests, Benny Glass stays with the proven capacitors.
For the resistors, Benny Glass opted for a combination of Allen Bradley AB resistors and Audio Note non-magnetic silver tantalum resistors, as this is the Ultra-Fi version and they leave a stronger sonic impression than the capacitors. 

Benny Glass also tried Sakuma-style interstage connections and kept coming back to them, but these tubes, especially the 71A, sound better when loaded with a current source.
Listening impressions: “We were amazed at how seamlessly the highs and mids blended, played a special recording with lots of bells and organs, and the whole thing was just stunning.”