SSPB.V2 Solid State Preamp Buffer Kit

SSPB.V2 Solid State Preamp Buffer Kit

Price: $219

This is a legacy product and is no longer produced or sold by Tortuga Audio.

The SSPB.V2 ("SSPB" or "buffer") is an elegantly simple, high performance solid state JFET buffer kit with flexible configuration options, including an optional op-amp input/gain stage and the ability to run as a pure, direct-coupled input & output discrete buffer. It’s aimed at the DIYer adding a solid state buffer to an existing passive or active preamp to correct an impedance mismatch or increase system dynamics — paired with a volume controller on the front end (not included), the combined volume control/buffer becomes an effective active preamp, with or without gain.

The kit ships as a bag of parts requiring soldering assembly. It does not include an enclosure, interface sockets, jacks, wiring, or the other items typically needed to build a finished standalone buffer — those are left to the builder to source and integrate.

Overview

In its default configuration, the buffer has a direct-coupled input and an AC-coupled output (coupling capacitor). It can optionally be equipped with an op-amp input stage, configurable as either a pure unity-gain input buffer or a gain stage with user-adjustable gain.

The split-voltage power supply, together with the ability to hand-trim the constant current sources, also allows the outputs to be optionally direct-coupled with no coupling capacitor.

The output stage is a discrete, high performance LSK170 JFET transistor providing robust current amplification with low output impedance and minimal DC offset.

A high quality kit

The kit includes 24 unique premium quality parts (43 items total), including:

  • Gold/nickel plated 2.7" x 4.4" printed circuit board

  • Vishay/Dale resistors in the signal path

  • Vishay and Wima polypropylene film capacitors

  • TI LME47920 high performance audio op-amp (optional)

  • Mostly gold-plated pins, jumpers, and sockets

All parts ship in individually labeled clear plastic bags.

Design origins

The SSPB.V2 is a second-generation version of the solid state buffer used in the LDR300.V25 Buffered Preamp. The same solid-state core also appears in the TPB.V1 hybrid tube buffer and LDR3000T.V25 hybrid tube preamp.

Tortuga Audio noted that the design has drawn comparisons to the popular Nelson Pass B1 buffer — while not developed with close reference to that design, a later review confirmed both similarities and key differences: a split-voltage design, direct-coupled input, adjustable constant current source, the option to run direct-coupled output (no coupling capacitors), and the option of an op-amp input buffer/gain stage. After evaluating a range of discrete transistors, the LSK170B JFET was selected as the heart of the circuit.

Key features

  • Kit or assembled/tested — ships as a DIY kit by default (all through-hole parts, no surface mount), or the populated board can be ordered fully assembled and tested for an additional cost.

  • Direct input coupling — no AC input coupling capacitor; minor DC offset on the input is readily accommodated.

  • Optional gain stage — an optional dual-channel op-amp input stage, set up as a unity-gain buffer or a fixed-gain stage. The op-amp is a standard dual-channel 8-pin DIP, socketed for easy substitution.

  • Adjustable gain — from unity up to the op-amp’s recommended maximum, via plug-in gain modules (2 resistors each; one module per channel).

  • Optional direct-coupled output — ships with output coupling capacitors, but the split-voltage supply and manually-trimmed DC offset make direct-coupled (no AC coupling caps) operation possible. No excess DC-offset output protection circuitry is present.

  • Control inputs — 2 external control inputs (0-5V): PowerOn and Mute. Holding PowerOn low turns the buffer on, auto-unmuting after 3 seconds if Mute is also held low; setting PowerOn high immediately mutes and then powers down the op-amp and buffer circuit. Once powered, Mute (+5V) and unmute (0V) work independently, muting via a relay that grounds the buffer’s outputs. If neither input is used, both must be jumpered for the buffer to operate.

Power supply

Internally, the buffer uses a switching regulator producing a +/-15V split voltage, further regulated down to +/-12V via a second-stage pair of linear regulators. Belleson SuperRegulators can be substituted for higher performance, lower-noise power to the buffer and op-amp.

What this kit does not include

  • Wiring to/from the buffer for power and signals

  • Volume control/attenuator

  • Amplifier

  • Enclosure

  • Power supply

  • Interface jacks, plugs, or sockets for power and signals

Requirements

Not an especially difficult kit to assemble, but it requires soldering a variety of through-hole parts. Beyond a soldering iron, a decent set of wire cutters and ideally a volt-ohm meter are recommended. None of the parts are known to be especially heat-sensitive, but the usual caution soldering smaller components (particularly ICs) applies.