The legendary George Wright WPP-100C phono preamp. In excellent condition, with a full second set of spare NOS tubes, direct from George a couple years ago.
This is the phono preamp that put Wright Sound on the map, and has garnered excellent reviews from around the world. Very unique, it uses 2 x 12AU7/5963, plus 4 x 6ER5 (framed-grid triodes), also a tube rectifier and voltage regulator. Includes the main chassis and the outboard WPS-02 power supply, 2 full sets of NOS tubes (Amperex 6ER5s, and some nice 5963/12Au7s. Amperex 7316s also available). Also includes the stock tube shields that George supplied with these units.
Gain is up to 65db and is infinitely adjustable via potentiometers on the top of the unit. In my experience it has been a very quiet unit without any hum or noise (which is rare for a tube phono preamp).
Asking $750, including the original tubes and full spare set of NOS tubes, all of which were specially selected and graded by George for this application.
See these pages for details from his (archived) site:
http://web.archive.org/web/20021209042637/www.wright-sound.com/tech_talk.asphttp://web.archive.org/web/20021209073849/www.wright-sound.com/products/MoreDetail.asp?Id=2Text directly from the Wright-Sound site:
"WPP100C Phono Preamplifier
The two-piece WPP100C Phono Preamplifier has low-noise circuitry and passive equalization as well as a dedicated line amplifier. Our phono preamp comes with a polished copper-plated chassis, not just for looks (although it does look nice!), but mainly to keep the ground plane resistance as low as possible. Includes a WPS04 power supply.
The phono cartridge jack is coupled directly into the grid of the first stage. The cathode is bypassed by a small capacitor paralleled with a large value filter to bring the cathode reactance as close to ground as possible. The frame element is tied directly to ground, and the plate is coupled through a capacitor into the passive RIAA equalizer circuit into the next stage grid. The cathode and frame are hooked up as in the first stage. The second phono stage is capacitor coupled directly to the linear level potentiometer.
Specifications
Frequency Response: Better than 20 Hz to 20 kHz, plus/ minus 1 dB RIAA curve
Distortion: Less than 0.4 percent total harmonic distortion
Input Impedance: 47 kilohms
Output Impedance: 2 kilohm, nominal; will drive loads down to 600 ohms with some loss of output level
Voltage Gain: 0-60 dB, nominal
Tube Compliment
2 x 5963 (12AU7)
4 x 6ER5/EC95
1 x 6EA7/6EM7
1 x 6X4
WPS04 Power Supply:
The power supply uses a full wave tube rectifier through a double Pi filter into the series pass inverting regulator stage. DC output is then fed back through a control stage and back up to the series regulator. This reduces noise and keeps the DC constant throughout it's operation. The filament uses fast recovery diodes with slow start circuitry driving into a large filter capacitor to provide a clean filament source. The LED's show both filament and plate status. On the filament side, the green LED will come on as soon an the power supply is turned on. The amber plate LED will come on approximately ten seconds later as the tube rectifier warms up. The WPL10V and WPP100B/C use a cannon XLR-type 4 pin inter-connection with a shielded DC cable to keep noise away from the preamp chassis.
Why I Use Framed Grid Tubes in my Phono Stages:
First of all, they sound better. In 1968, I was trying to build a better phono preamp that would bring out more detail. After building most types available, I was not satisfied with the results that I got. I had built some high frequency radio equipment and was impressed with the ability of framed grid tubes to amplify RF signals without losing gain through over neutralization.
I built my first framed grid RIAA phono preamp in February, 1968. From the moment I listened to it, I was struck by it's ability to bring out detail I had never heard before. It was clean and sharp. Everyone who heard it thought it was great, but in 1968 everyone was dumping tube equipment for that solid state stuff. In 1995, through some friends, my interest in producing consumer equipment was rekindled, so I'm off again building great sounding tube equipment.
Framed Grid:
Not to be confused with frame grid, a framed grid tube is a high amplification(mu) VHF triode with a slotted frame around the grid to shield part of the grid structure and allow a controlled field of electrons to flow through to the plate. This may seem like Voodoo electronics, but because of the capacitance coupling in high mu triodes between the plate and the grid, the capacitance times the mu factor produces high frequency loss, depending upon the grid and plate impedance. A typical 12AX7/ECC83 high mu tube has a capacitance of 1.5 to 2.4 picofared between the plate and the grid. Multiply this by it's amplification factor of 100 and you come up with an active degenerative capacitance of 150 to 240pf. Using this tube in a high resistance mode with this type of capacitance will round off the high frequency content, depending upon the grid and plate resistance and loads. The framed grid, in comparison, depending upon type, is 0.2 to 0.5pf with a mu factor of 70-80, thus the degenerative effects are greatly reduced. In addition, these tubes have lower plate impedance and a smaller grid structure that helps more detail pass through. So you see, it's not really Voodoo electronics, it's physics.
"
(Pictures coming soon)
Thanks for looking!
-Ed Sawyer
ed@edsawyer.com
