TPB.V1 Tube Preamp Buffer

The TPB.V1 allows substituting the stock 6H30 tube with any tube from the 6DJ8 / ECC88 / 6922 / 7308 family, opening up a wide range of tube rolling possibilities.

The TPB.V1 is more than a conventional unity gain buffer. Whereas most audio buffers have only a unity gain buffer stage, the TPB.V1 is a hybrid tube preamp/buffer with an adjustable-gain tube preamp input stage as well as a solid-state buffer output stage.

Like all buffers, the TPB.V1 has no volume control of its own and belongs downstream of an existing preamp or source device that has its own integral volume control — a great match for anyone with a passive preamp looking to add tube euphonics and more authoritative dynamics without going back to a conventional active preamp.

The TPB.V1 is ideally suited for use with passive preamps such as Tortuga Audio’s own line of LDR passives, but works well with any type of preamp. For passives, the buffer makes impedance matching issues moot and allows long runs of interconnect between the buffer and the amplifier — overcoming any weakness a source might have driving a passive preamp directly. For those driving multiple amplifiers from a single passive preamp, the TPB.V1 also eliminates impedance issues from driving multiple loads in parallel.

The challenge with any active line stage component, including preamp buffers, is delivering a satisfying listening experience that remains true to the source material while enhancing the audio signal with minimum ill effects. The TPB.V1 achieves this through a hybrid tube/solid-state design that keeps the signal path short and simple without compromising performance.

The incoming audio signal connects directly to the triode’s grid with no input coupling capacitor. A 100k ohm input impedance makes the buffer extremely easy to drive. The input stage uses the 9-pin 6H30Pi Gold triode from Electro-Harmonix, run at a much lower plate voltage than most other tube preamps — reducing tube stress and, combined with the tube’s already robust design, helping ensure a long service life while delivering a delightfully smooth yet muscular sound with just the right amount of tube euphonics.

The default gain of the TPB.V1 is unity (0 dB), adjustable by the user via internal jumpers to either +3 dB (~1.414 Vo/Vi) or +6 dB (~2 Vo/Vi) for systems that need more volume headroom.

Each stereo channel has its own dedicated 6H30 tube for the best possible channel separation. In single-ended configuration only half of each triode is used; in balanced configuration each triode handles both phases of its own stereo channel.

The TPB.V1 has two independent oversized DC power supplies, one dedicated to the tube heaters and the other providing clean DC power to both the tube and solid-state signal path stages. Because the 6H30 draws considerably higher heater current than most triodes, an oversized 40VA toroidal supply is combined with a switching DC-DC regulator capable of powering a pair of 6H30s with substantial design margin while minimizing noise and thermal issues.

The output stage is a solid-state design delivering the audio signal with ample current at low output impedance, using less complex hardware than would be possible with tubes alone. The proprietary Class A output stage uses a FET in combination with a constant current source, delivering compelling, robust dynamics. The output stage core is encapsulated in a 4-pin removable, replaceable plug-in module.

These specifications reasonably reflect the final production model.