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At 50 watts, Mr. Park's quad-paralleled A-6000 monos are the most powerful 300B single-ended production amps on the planet. Quick-watted math reflexes will instantly doubt the figure. Traditional 8-watt per precedents would only net 32 watts from a quad scheme after all. Roger Modjeski in the US of course also is known for obtaining more true output power from his tubes than is conventionally considered feasible. How does Mr. Park claim to do it?


Essentially, he refers to the 300B's deep grid bias as requiring powerful drive. Conventional power limitations are said to arise from pre-distorted driver circuits with compromised power transfer. He believes that the only two proper ways to drive 300Bs to their full sonic and power potential are interstage transformer coupling and plate loading by choke. The original Western Electric 91B circuit used a 310B or 6SJ7/6SH7 pentode driver with high internal 100K impedance which K.S. calls "notorious for distortion with undue sensitivity of the screen grid condition and poor frequency response at the extremes". Popular two-stage driver circuits around the 6SN7 run each half of the twin triodes to make up one stage. "They aren't sufficiently powerful, suffer too much gain and rely on capacitor coupling which transfers an insufficient amount of drive power to the 300B grid. Most of it is converted to useless heat at the 6SN7's plate resistor. Compare the latter's 27K load impedance/DC resistance to the 2K DC resistance of our choke transformer."
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K.S. doesn't like EL34/6V6 or 349A-as-triode drivers either because of their large plate resistors and coupling caps. So he loads the plate of his single-stage 6GV8* pentode driver circuit in triode mode with a 100% nickel permalloy PC-core choke inductor of very low power loss and infinitely high load impedance. This transfers a 150V instead of 70V swing voltage to the 300B (in his T-1500 and T-3000 single-ended single and parallel integrateds, K.S. uses a 14GW8 choke-loaded pentode driver). He also insists on fixed bias to eliminate "those hot cathode resistors", increase power output and lower distortion. The PB-core Permalloy output transfortmers sport "extremely high initial permeability to allow lower primary winding turns while retaining high open circuit inductance. They also uses a very big nickel core to avoid magnetic saturation."

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* The noval 6GV8 pentode is equivalent to the ECL805/85 and 6F5P and was made/branded by companies like Siemens, Lorenz and RCA.
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For his top A-6000 4x300B single-ended monos, Allnic Audio thus claims 50 watts at the usual, not liberally relaxed THD figures. Voltage gain is 24dB and input sensitivity 0.7V. The L-4000 linestage also runs a single gain stage only. And output transformer coupling. The latter again eliminates the usual power loss of coupling capacitors. Allnic claims 16Hz to 75kHz -3dB bandwidth for its preamp's output transformers. They couple to high gm, hi mu D3a/7721* voltage gain tubes of low internal resistance. The 150-ohm output impedance is constant at all frequencies to not suffer the steep rise at low frequencies which cathode follower circuits are prone to.
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To optimize noise floor and dynamics, two 6485s and two 7233s perform "ultra high-speed automatic voltage regulation. They protect the amplifying tubes from AC line changes and cope with all abrupt internal current demand scenarios". A 40-second auto-mute warm-up circuit prevents turn-on transients. Two back-lit analog current meters on the front confirm operational status. Allnic's Absorb-GEL tube damper sockets control tube microphony. An oil-clutched precision motor controls Allnic's premium stepped resistor attenuator via remote. Signal input is via 2/3 XLR/RCAs, output via single XLR/RCAs. Voltage gain is 20dB, maximum non-clipped voltage swing +/-15V RMS and S/N ration -90dB.

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* The D3a is an NOS Siemens/Halske postal-service, 10,000-hour long-life pentode with 35mA mutual conductance. The 6485 was made by GE and is equivalent to the Tesla 6F36, the 6AH6 and the Russian 6J5P. The 7233 is a noval low-mu miniature series regulator triode. These same valves also show up in Allnic Audio's smaller L-1500 line stage, albeit with just one 6485 and 7233 each.

That's the short version of our introduction to Allnic. For a quasi factory tour appropriate considering the brand's unfamiliarity to the West, proceed to Sidebar 2 for photos and an introduction of team Allnic Audio Labs.
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