High-Fidelity Headphone Amplifier AudioValve Verto black

Overview

The passive box can be used with AudioValve RKV II and RKV III tube headphone amplifiers. There was a simple idea behind the VERTO. Why not use the transformer in step-up mode to produce the high voltage for STAX electrostatic headphones? The RKV models use one transformer per channel (impedance) to drive low impedance headphones (<100 Ohm). In the RKV III, the transformers are mounted inside the housing, for the RKV II, the impedance can be purchased as a separate box. The RKV II and III are considered to be among the best headphone amps, regardless of price, see many reviews all over the world.

For a game-changing product, a simple idea is not enough, you also have to find a suitable implementation. There are already promising approaches on the market combining transformers with headphone amps to drive STAX headphones. But RKV and VERTO now exploit the full potential of this approach. The inductance and capacitance of the transformer can damage the sound. The Pikatron output transformers we use have very little stray inductance and capacitance. To avoid any distortion, we only use a low step-up ratio of 1 to 5. But the key is the fact that the output impedances of the RKV II and III are extremely low, too low to cause a negative effect on the sound.

The VERTO supports the current STAX PRO socket with 580 V DC bias as well as the old 300 V bias used by older STAX headphones. The higher PRO bias uses a 5-pin connector, the 300 V DC bias can be identified by a 6-pin headphone jack at the end of the headphone cable. The VERTO is therefore suitable for all STAX models.

The VERTO is connected to the headphone amp with a telephone cable and a standard plug supplied with the VERTO. There is nothing to buy for you in addition to the VERTO. Moreover, the VERTO does not require a separate supply voltage. This ensures that there is no interference and hum caused by the mains connection. The RKV III must be put into OTL mode when driving the VERTO.

To increase versatility, we have implemented a switch for 8 Ω as well as 32 ohms. You can thus connect highly efficient speakers as well as low impedance headphones. Feel free to drive mobile headphones designed for Apple devices as well as low impedance high-end designs like Audeze or Abyss. Check to drive your highly efficient speaker with your RKV and VERTO tube and transformer chain!

Since the connection of the VERTO to the headphone amp is implemented via a standard telephone jack, you can also use it with other headphone amps instead of the RKV II and III. You will get very good results in case you use a headphone amp with low output impedance and high output voltage. We doubt that you will get the same ultimate sound quality as with the RKV models. The RKV II and III are capable of delivering a 100 volt peak-to-peak drive.

We use only high-quality components inside the box. The Picatron transformers are built to our specifications. For wiring the main audio connections to the headphone jacks and the female STAX cable, we use a well-known German manufacturer of premium audio cables called HB Cable Design from Cologne. The cable core consists of multiple-stranded, silver-plated oxygen-free copper conductors.

Technical specifications

Compatible with all STAX electrostatic headphones
Suitable for low and medium impedance dynamic or planar headphones
3 switchable modes for STAX electrostatic mode, 8 Ω and 32 ohms
60 cm cable with phone plug attached to the housing for connection to the headphone amp (such as Audio Valve RKV II and III)
No separate supply voltage required, a static high voltage is generated by the signal
A high-quality galvanically coupled Pikatron output transformer for each channel
Internal bias voltage for STAX 300 + 580 VDC (LED controlled)

Design

Internal HB cable with a cross section of 0.72 mm2, embedded in PTFE Teflon insulation air. The termination is a solid 5 mm diameter silicone, the high voltage signal line to the outside is reliable and well insulated
The device provides both the necessary static voltage for headphone operation of 300/580 VDC and a signal voltage of up to 550 Vrms
Bandwidth up to nearly 100 kHz - (470 pf load)