What is a buffer?
In simple terms, a buffer is an active preamplifier with no volume control, no input switching, and no gain (voltage amplification). What’s left is a unity gain current amplifier with a low output impedance that delivers the audio signal with more power and authority while acting as an electronic firewall between your source and your amp.
Why use a tube buffer?
Improved sound quality – This is job #1 of any buffer. If it doesn’t make your existing system sound better overall then either you have a great system already (congrats!) or you need to get a better buffer!
Add more authority and punch into your system’s dynamics – A buffer’s main job is to be a power/current amplifier. A buffer doesn’t make music louder. It makes music sound bolder and more robust.
Beautiful tube harmonics – Call it euphonics, call is harmonics or call it distortion, the fact is tubes deliver a low level of second order harmonics that most people find musical and pleasing to the ear.
Sand the digital edge off your DAC – Even the best digital sources and DACs are usually solid state designs that can come across a bit dry or even harsh at times. A good tube buffer can mitigate this little or no downsides.
“Tubify” your solid state system – Some solid state systems (solid state DAC, solid state preamp, solid state amp) suffer from the solid state blues. Adding just the right touch of tube dynamics can turn a good system into a great system.
Use your passive preamp with long cable runs – If you love your passive preamp but need to run longer cables to you amp, adding a buffer between your passive preamp and amp eliminates the cable length constraint.
No impedance mismatches between components – Adding a buffer between any two components creates an electronic firewall that makes any impedance mismatch problem moot.
Drive a subwoofer amp from your passive preamp – If you love your passive preamp but find it can’t drive both a main and subwoofer amp, a buffer will resolve this.
TPB.V3 tube preamp buffer
The TPB.V3 tube preamp buffer deliver robust dynamics with just the right touch of that airy and sparkling sound that only tubes can deliver. If the rest of your system has that dry solid state sound, adding in the TPB.V3 tube preamp buffer rarely fails to satisfy.
The TPB.V3 is our 3rd generation tube buffer that is designed as both a stand-alone tube buffer board and also as a plug-in module. to the V3 Max. When used as a plug-in, it mounts directly on to the V3 Max attenuator/controller board turning the V3 Max into a compact, high performance tube preamp.
Dedicated tube/JFET per stereo channel
Direct coupled tube input stage
The incoming audio signal connects directly to the triode’s grid with no input coupling capacitor. A 100k ohm Vishay Dale resistor sets the tube buffer’s input impedance making the tube buffer extremely easy to drive.
We chose the 9 pin 6H30Pi Gold triode tube from Electro-Harmonix because of its growing reputation for sonic excellence, robust long-life, and the fact that it’s a contemporary tube that isn’t likely to go out of production for a long time to come.
We run the 6H30’s at a much lower plate voltage than most other tube preamps. This lowered voltage reduces tube stress and together with its already robust design all but guarantee that the 6H30’s will last indefinitely.
Most importantly, the 6H30 is a delightfully smooth, neutral and muscular sounding tube with just the right amount of tube euphonics.
Powerful solid state output stage
The output stage of the TPB.V3 is the buffer proper. And the heart of any buffer is its current amplifier (a.k.a. “current drive”). Unlike a voltage amplifier (voltage gain stage) which makes music louder, a current amplifier delivers the music with more authority, power and dynamics. To use the garden hose analogy, if music volume is water pressure, then current drive is the capacity to deliver the water flow. That’s the job of the audio buffer; to effectively deliver the content of the audio signal represented by the voltage.
To this end, we employ the highly effective, low noise LSK170 JFET transistor in an elegantly simple class A constant current circuit with commensurate low output impedance. The result does not disappoint.
In fact, this is essentially the same proven buffer design used in our SSPB.V3 solid state preamp buffer. However, unlike the solid state buffer, the tube buffer requires that we use a DC blocking capacitor at the output to deliver a zero DC offset.
Tube rolling possibilities
The TBP.V3 tube preamp buffer allows you to substitute the stock 6H30 tube with any tube from the 6DJ8 / ECC88 / 6922 / 7308 family of tubes which opens up a big wide world of tube rolling possibilities. More info on tube rolling the buffer can be found here.
Optional gain if you need it
The TPB.V3 is configured by default as a unity gain buffer, i.e. no volume amplification . The reason for this is quite simple. Most home audio stereo systems do not require signal amplification by a preamp/buffer in order to achieve sufficient volume levels. And since all amplification increases signal noise, why amplify any more than is necessary?
For those systems that need a little more volume headroom, the gain of TPB.V3 tube buffer can be increased by the user by swapping out the unity gain plug-in gain modules with higher gain plug-in modules of +3 dB (1.414 x gain) or +6 dB (2.0 x gain).
Robust hybrid power supply
The TPB.V3 is powered by an oversized 45 VA multi-stage power supply that starts with a highly efficient switching stage that converts either 120 or 240 VAC mains power into 12 VDC. The raw DC power is goes through a filter into pair of dedicated linear DC-DC regulators to deliver separate dead quiet DC current to each tube heater element. A separate circuit boosts the raw DC voltage which is then run through yet another DC-DC regulator to deliver low-noise plate voltage to the tube.
Given its high current capacity, the TPB.V3 is able to handle the current requirements of almost any 9 pin tube available today. Power supply will not be a limiting factor for those who consider tube rolling to be an official audio sport.
Output Coupling Capacitor upgrades
Since the TPB.V3 relies on an output coupling capacitor to pass through the audio signal, the performance of that capacitor becomes the ultimate limiting factor in performance. We employ a good yet modest stock polypropylene output coupling capacitor that can be upgraded to either an excellent high performance V-Cap ODAM (oil damped advanced metallized) capacitor or the quite pricey V-Cap CuTF (copper foil fluoropolymer film) capacitor for those seeking the ultimate in performance.
These specifications reasonably reflect the current model and are subject to updating and modification without notification.