For sale is my John East U-Retro Deluxe preamp (4 knob, black version). [DEL]$260 shipped. PayPal only. No trades.[/DEL] SOLD!! The preamp is in like-new condition with no issues at all. I'm just wanting something a bit simpler. Controls: vol/blend stack, treble/bass stack with push/pull treble, mids/mids sweep stack, push/pull tone control for active/passive selection Official Description: The U Retro's high quality circuit uses one single knob and three dual concentric knob stacks. It includes a passive blend plus a 3 band equaliser with bass, variable frequency mid, treble and bright function. A passive tone circuit is also included which operates in both active and passive modes. The passive tone pot has a push/pull function which switches between active and passive paths: Active - Signals from the pickups pass through the passive blend, passive tone, into the preamp input stage. Then through the equaliser and volume section within the active circuitry, and on through a low impedance output stage to the jack. Passive - Signals from the pickups pass through the passive blend, passive tone and then on through the passive volume control section which feeds the jack. A very gentle built in contour gives immediate colour without detracting from the basic sound of any bass. The active blend circuit prevents the loss associated with many passive basses where, when both pickups are up full, the signal from one pickup feeds into the other and vice versa. A standard PP3(9v) battery is used to power the U Retro. Technical Specifications Volume/Blend (Knob stack) Volume The Volume has two sections under the same knob. A high impedance section is used for the passive path and a separate additional section is utilised in setting the volume for the active path. When used active, this knob has active circuitry after it so that the feed to your amplifier is a low impedance drive. A 0-12dB preset allows gain adjustment for the imput stage of the preamp. Blend The Blend knob, fully operational in both active and passive modes, sets the balance between the pickups. This is a very conventional control type, used on many different types of basses. Turn it fully clockwise for the neck pickup alone and full anti-clockwise for the bridge pickup. The midway position, which has an indent, gives an equal mix of both pickups. Bass & Treble (Knob stack) Treble (+12dB @ 3 kHz, -12dB @ 1kHz) The upper knob is the Treble control with boost and cut. The central 'flat' position is indented. The cut settings work on lower frequencies compared to boost to give a deeper sound when the top is rolled off. Bright (+8dB @ 7kHz) Pull the Treble knob for the Bright setting. Bass (+15dB @ 50Hz) The lower outer knob is the boost only Bass control. The frequency band of boost gets progressively lower as the boost is increased. An indent midway is included to aid the setting of this control. Mid Level & Frequency (Knob stack) Boost/Cut (+/- 12dB) The upper knob controls the amount of Mid boost or cut at frequencies according to the setting of the Frequency knob. The midway indent is the 'flat' position. Frequency (150Hz - 3kHz) The lower outer knob is continuously variable and sets the Mid frequencies for boost or cut. Passive Tone (Single knob) The passive tone pot consists of two sections, one for each pickup. Two sections are necessary since the pickup signals are kept separate and fed to their own individual input amplifiers prior to the electronic blend circuitry. To retain the characteristics of a true passive tone, its circuitry is connected directly to the pickups at all times and therefore function in both active and passive modes. The roll-off frequency is set to give a deep mellow sound. ACTIVE PASSIVE SWITCH Pushpull on the passive tone knob. Power The PP3(9v) battery is switched on automatically when a mono jack is plugged into the socket.