H-10000 OTL/OCL Signature Phono-stage Preamplifier

MRSP $45,000 USD

Kevalin Audio is pleased to announce US availability of the new, flagship Allnic H-10000 OTL/OCL Signature Phono-stage. An OTL/OCL (Output Transformer-Less/Output Capacitor-Less) design omits the usual coupling transformer or capacitor at the output stage of the vacuum tube amplifier, thus reducing distortion, coloration, and energy loss. It unprecedented for an OTL/OCL circuit to be used in a phono-stage, which requires a level of amplification much higher than that of a line-stage preamplifier.

Like all Allnic’s phono-stages, except the smallest, the Allnic H-5500, the H-10000 OTL/OCL Signature has separate power supply and amplification units.

The voltages used for the 16 tubes and the nature of their arrangement and function in the H-10000 OTL/OCL Signature’s amplification unit require an exceptionally robust, extremely quiet, high-speed power supply. Thus, it was determined that the H-10000 OTL/OCL Signature’s optimal power supply would be an automatic solid-state rectification and voltage regulation device specifically designed to maximize the performance of the tube gain stages. The power supply has two separate circuits and two DC outputs which couple to the preamplifier via provided umbilical cables. The separate circuits and connections are not for each channel: there is one for each of the H-10000 OTL/OCL Signature’s two gain stages. This configuration provides exceptional stability, reliability, and very low noise.

The H-10000 OTL/OCL Signature’s amplification unit employs 16 vacuum tubes, 8 on each side with each in its own polycarbonate chimney. The vacuum tube arrangements on each side of the step-up transformer controls differ. Because this phono amplifier uses two-stage amplification to attain a high gain of 40-72dB, the left and right channel input signals are each first-stage amplified through an ECF802 triode-pentode tube, then a double triode E180CC, followed by two 7233 triodes. After phono curve correction, the left and right channel signals are each amplified in a second gain stage, again through an ECF802, an E180CC, and two 7233s. However, the tubes of this second stage appear on the chassis top in reverse order to the tubes of the first gain-stage. 

As with Allnic’s other OTL/OCL designs, the permalloy core output transformers that are the pride of Allnic‘s transformer coupled devices disappear from the H-10000 OTL/OCL Signature. Instead, two 7233 output tubes per channel form a single-ended push-pull (SEPP) circuit that uses both positive and negative power to prevent DC from passing to the next stage. The reason the 7233 was chosen as the output tube is that it has very low internal resistance; at only 230Ω, it can powerfully drive the following preamplifier or integrated amplifier without coloration or distortion.

Silver-wired, built-in MC step-up transformers (SUTs) are a primary feature of the H-10000 OTL/OCL Signature. Allnic's phono-stage preamplifiers and step-up transformers initially became famous because they used permalloy, with its high permeability, as the transformer core. Then, the performance of the SUTs was further improved by making the coils with silver wire, which has a higher conductivity than copper. Step-up transformer losses occur due to coil resistance and core saturation during the energy conversion and transfer process, but using a silver wire coil reduces those losses by allowing the coil resistance to be lowered as much as possible. The SUTs are easily accessible on the top of the chassis and adjusted with a turn of one’s fingers.

The H-10000 OTL/OCL Signature allows you to select the amplification factor and input impedance from four options. Looking at the step-up transformers, one per channel at the rear of the top panel, each has four amplification factors and winding ratios indicated: 22dB (×13), 26dB (×20), 28dB (×26), and 32dB (×40). The MM gain of the H-10000 is 40dB, and the MC gain is 62dB, 66dB, 68dB, and 72dB. Once the turns ratio is determined in this way, the MC input impedance is automatically determined by the formula ‘MM input impedance / turns ratio squared’. If the MM input impedance is 47KΩ, then: 22dB is 278Ω, 26dB is 117Ω, 28dB is 69Ω, and 32dB is 29Ω.

The H-10000 OTL/OCL Signature possesses a suite of other features, controls for which are located on its front panel. On the upper center of the H-10000 OTL/OCL Signature amplification unit’s front panel, there is an input selector dial for four inputs, two for moving coil and two for moving magnet cartridges. Below that dial are two pairs of LCR multicurve EQ knobs, one for each channel. One knob of each pair is for turnover, and one knob of each pair is for roll-off. Four balance meters, two for the right and left channels of each of the two gain stages, monitor whether DC is involved during the amplification process. There is also a mute/operate button. On the rear panel there are four pairs of RCA inputs and one pair each of XLR and RCA output connectors.

As just noted, a final highlight of the H-10000 OTL/OCL Signature is that it supports not only the standard RIAA curve, but also other phono curves, such as the Decca and the Columbia, through its ‘LCR Multi-Curve EQ Units’. For example, the RIAA curve can be selected with 500Hz as the low-pass turnover frequency for a 6dB boost in the equalizing stage, and -13.7dB as the attenuation level when playing 10kHz high-pass. In addition to these standard values, the H-10000 OTL/OCL Signature has turnover frequencies of 250Hz, 400Hz, 500Hz, and 700Hz, and high-pass attenuation levels of -5dB, -11dB, -13.7dB, and -16dB. As above noted, the two EQ units per channel are conveniently controlled from the amplification unit’s front panel.

Please email or call to discuss the new Allnic H-10000 OTL/OCL Signature Phono-stage and purchase details.