The HPA-15000 is Allnic Audio’s flagship Output Transformer-less (OTL) and Output Capacitor-less (OCL) stereo headphone amplifier. Unlike the HPA-10000 which is designed to perform best with dynamic type headphones, the HPA-15000 is designed for excellent performance with all headphones, including more inefficient ribbon and planar-magnetic types. Like the HPA-10000, the HPA-15000 utilizes a true balanced Positive-Negative cancellation circuit. It features pre-out connections, allowing it to also serve as a superior All-in-One line-stage preamp for most amplifiers. However, the HPA-15000 uses a different tube set, which results in consequential changes to the circuitry. It also offers a Harmonic Balance Mode option for use with ribbon and planar-magnetic headphones, utilizing an analog filter to produce a more natural sound with these types of headphones, without compromising any of their unique benefits.
In common circuits, output capacitors or output transformers are required to separate the AC music signal from the DC operating potential. If this is not done, the latter will destroy the power amplifier, the loudspeakers, or both. However, these two coupling devices also introduce their own influences on the transmission of the musical signal, adding their own character (coloration), increasing distortion, and consuming small signals, all as predicted by physical efficiency theory. In addition, they also limit signal dynamics. For these reasons, the elimination of output transformers and capacitors has been considered the best solution for the design of the most accurate amplifiers. Removal of these two coupling devices from the signal path achieves the best results possible:
• No coloration of the musical signal
• Extremely detailed expression, natural harmonics and subtle musical decay
• The lowest possible distortion
• The widest musical dynamics and frequency range
In the HPA-15000 OTL/OCL, there is no coupling device between the amplifying tubes and the headphones (or power amplifier when used as a line-stage preamp); that is, the final gain/output tubes are directly connected to the headphone outputs. Thus, the benefits listed above are fully present in the Allnic HPA-15000 OTL/OCL.
The HPA-15000 may be ordered with, at no additional cost, one RAAL Direct Drive balanced output dedicated to RAAL ribbon headphones. With this option installed, RAAL headphones can be connected directly to the HPA-15000 without the use of the RAAL Direct Drive dongle.
This option requires installation of a 0.2 ohm transformer for that output only, so the RAAL output will not be OTL/OCL. However, this output transformer is the best Allnic makes, a silver wire wound, permalloy core transformer like the incredible, silver Step Up Transformers on Allnic’s famous, top-of-the line phono preamplifiers – one of the very best transformers available in the industry and capable of allowing your RAAL headphones to perform at their spectacular best. Please request RAAL Direct Drive when ordering.
This model was designed for and voiced with RAAL Ribbon and Hifiman Susvara Planar Headphones. Click here for the Allnic Regional Distribution Network.
