This is a “one of a kind” preamplifier. It uses the 26, an early DHT, capable of a pure sound . Who ever is familiar with the 26 sound can say that it excels in musicality and emotion.

At the demand of the client, the preamplifier was carefully designed in one enclosure. Despite the challenges of a single enclosure DHT preamp, the 26 device is as quiet and as little microphonic as possible. 26 tube is known for picking up noise/hum from proximity to the AC radiating area. I highly recommend a dual enclosure scenario, with a separate power supply. However, if used with low power tube amps that have low to medium overall gain, this preamp will perform great.

The preamp has 2 distinct zones (looking from above): on the right hand side is the power supply zone and on the left hand side is the main signal path zone.

The power supply area is packed with separate supplies for each filament of the 26 tube, the regulated DC for the remote control unit and the high voltage unit. Each 26 tube filament has a raw DC supply using 40,000uF of filtering capacitance per channel, and a much praised Coleman filament regulator. The high voltage supply is using a type 80 tube as rectifier and a CLCLC filter, followed by a special Mosfet shunt regulator that brings the ripple down to uV levels.

The signal path of this preamp is as short as it can be, and free of coupling or decoupling capacitors. That was possible by:

•  Using filament bias circuit, where the filament is in series with the low value (10 ohms) bias resistor. This resistor doesn’t need to be decoupled. The filament current is adjusted by the Coleman regulator (which is a CCS-constant current source).
• Using a line output transformer by Lundahl LL2763/7mA

The line output transformers are made by Lundahl in Sweden, and they have 4 balanced secondary windings. There are 3 4PDT switches on the back panel, aligned with the left and right RCAs. If they are all toggled upwards, the gain of the preamp is 12-13dB, and if they are downwards the gain of the preamp is 6-7dB. The high gain position implies a 2:1 output ratio and the output impedance of the preamp is 2200 ohms. The low gain position implies a 4:1 output ratio and the output impedance of the preamp is 600 ohms.

The input of the preamp is DC coupled using a motorized Alps Blue Velvet remote control by Bent Audio. This is a high quality, super quiet remote.

The preamp is provided with 3 inputs switched by a high quality Seiden selector switch made in Japan.

The enclosure is a very sturdy 1/8” thick aluminum chassis by Landfallsystems.

The top plate is custom CNCed and anodized at Front Panel Express. The sides and front are wrapped with ¾” American cheery hardwood that was stained with General Finishes Antique walnut gel stain and coated with 4 layers of oil based urethane.

The preamp will sound smooth, clean and clear sound with 0.05% THD second harmonic predominant at 2Vrms output.