Zu Druid 6, Part V
Xiao Nan does not pot his transformers both for maintainability and because potting compromises high frequency performance. You may hear a trace more mechanical hum up close than from, say, a true Quad II. But music-on, this is irrelevant. The amps are quiet electrically. Common to all of Xiao Nan’s amplifiers is exceptional transparency, very high definition, fast transient speed, exceptional soundstaging and depth. For whatever reason, with any of his amplifiers, I am getting more spatial depth in the soundstage than with any amplifiers I’ve had connected to my Zu systems, regardless of price, and that includes the many amps visitors have brought to audition on Zu speakers. That fast, transparent, dynamic, tuneful sound I valued particularly in Audion SET is here. Further, in the push-pull amps, crossover notch grunge is vanishingly low. Some notes on specific amps:
Quad II Clone: Fast, open, dynamic sound. Because Xiao Nan winds the output transformer differently than Quad did, this also changes the feedback behavior somewhat. The result is greater audible difference between KT66, 6L6 and EL34 in the clone compared to genuine Quad II. With EL34, the clone is relentlessly revealing, hi-def and blindingly fast, which is great for excellent recordings/masters/pressings, but not forgiving of flawed wax or digitalis-digital. With KT66 the clone is closest to the original Quad II sound, which was not strictly romanticized but does possess some vintage warmth. The perfect balance is found with the NOS 6L6. With this power tube, the clone is smooth, defined, dynamic; delivering Druid-like tone density and lots of dynamic punch for its power. The amp takes some time to burn in and bloom. About 120 hours will do it. It will sound thin in the bass region until then, but progressively less so.
Williamson (Triode-Mode): Dynamically stronger than the Quad II or its clone. Refined, smooth, high definition, solid deep bass on Definition 4 or Druid 6. Same basic sonic difference between EL34, 6L6, KT66, as in the Quad Clone. Again, I settled on NOS 6L6. In the Williamson, the Quad II and QII Clone, my preferred rectifier is the Tubestore Preferred Series 274B. It gets the most tone, space, definition and dynamic punch from all three amplifiers. This is an exceptional tube amp, that lives up to the Williamson amp legend from shortly after WWII. In fact, it’s the best Williamson implementation I’ve heard and easily walks over a Marantz 8B.
2a3 Push-Pull: Inexplicably bursty and elastic for its 13 watts. And my pair have only 8 ohms windings. On 16-ohm Druid 6 they sound dynamically huge. Excellent bass discipline compared to any SET amp, while retaining all the triode magic, though still quite objective. No slow, lazy, old-school triode amp sluggishness. This amp, Xiao Nan’s custom circuit at my request, gives up nothing in definition, speed and punch to the tetrode and pentodes in his other push-pull amps. The rectifier you want is NOS 5v4.
Klangfilm KLV-204: This is an early post-war German cinema and studio amp. It was used as a monitoring amp in recording studios (so high definition required) and as a reserve amp for cinemas using the larger KLV-402 & 502 amplifiers. It lives up to its high definition requirements. I have known about the F2a tetrode tube for decades and never managed to get my hands on any of the Klangfilm or Telefunken amps that used it. I was excited to get a chance to hear the Shindo Cortese, which promptly disappointed me like most other Shindo amps I’ve heard. But this KLV-204 clone is exciting to listen to! Only 10 watts (I had my pair wound for 16 ohms to use with Druids), it sounds dynamic beyond its means. No detail gets past it. Midrange is tone-dense like a great triode but burstier. Among the quickest, most agile amps I’ve heard at any price. Like Druid 6, this KlangClone is vivid, tonally, dynamically, and spatially. With Druid 6 it is musically amazing on an excellent recording, but the x-ray truth of the combination can render a poor recording too distracting to listen to. Badly recorded or mastered bass, particularly, shunts the illusion of musicality. This is one of my favorite amps ever heard, but it is a specialist and Xiao Nan builds it affordably enough to use it selectively. The F2a tube, btw, is a German Post power tetrode built for 10,000 hours of life. They often go longer. As NOS and vintage tubes go, they aren’t cheap, but they aren’t ridiculously expensive, either, given how long they last.
LS50/GU50 Single-ended Pentode: More like the sound of the Klangfilm KLV-204 than any of the others. Crisp, clear, fast and transparent. Also dynamic beyond what’s expected from its mere 13 watts output. Clean top-to-bottom. A little bass shy compared to the push-pull amps but there’s a remedy. In most tube amps, particularly those with cathode bypass caps, there is a trade-off between ultimate bass performance, and ultimate top end. When faced with this, Xiao Nan prioritizes top end linearity over bass linearity. But making adjustments to the chosen values for cathode bypass caps can land you in your zone. You can do this after getting the amps or if you communicate to Xiao Nan your general preferences, he can reliably adjust for the right value. You just have to communicate effectively. Overall, Xiao Nan’s LS50/GU50 single-ended pentode monoblocks are sonically in the same realm as the F2a-based Klangfilm KLV-204 clones, but not quite so MRI in unsparing revelation. The LS50 has more latitude in acceptable recording quality than the KlangClone. Given the Definition 4 sub-bass extension, Xiao Nan suggest snipping the cathode bypass cap on the E180F driver tube to bring bass performance into better balance with the speaker. But I have to say before doing that, the intrinsic bass from this amp on Def4 maybe a little light, but it is very well presented in terms of character, definition and attack.
300B/2a3 Push-Pull: I commissioned Xiao Nan to build for me a pair of monoblocks that can use either 300B or 2a3 output tubes, in push-pull configuration. I have a quad of KR 300B Balloon tubes held back from my recent sale of my Audion Golden Dream 300B monoblock amps, which I wanted to use in push-pull configuration with either my Druid 6 or Definition 4 system to make continuing use of those magnificent tubes. Xiao Nan indulged me with a custom design. Those amps are arriving in the next day or two. Comments pending if anyone is interested.
Telefunken V69 Clone: Probably last in my series of bracketing amps from Xiao Nan will be a pair of clones of the legendary Telefunken V69 Cinema amp. This is a full Class A, push-pull, tetrode amplifier using a pair of the F2a tetrode tubes in each monoblock. Like the Klangfilm KLV-204, input and driver tubes are the equally-revered EF-12 small-signal pentode. Class A output is 25 watts per monoblock. I will decide in the next day or two whether I will order these, put them in the mix and then vet the whole shebang for what stays and what goes.
You can find Ling Xiao Nan on eBay as seller “fatkit83-8.” If you private message me, I can offer his direct contact information for amp inquiries.
Of course the genuine Quad II remains a highly-viable tube amp for any Zu speaker. It is coherent, musical and also delivers more dynamic shove than its diminutive specifications might lead you to expect. Ling Xiao Nan gives you alternatives, and plenty of them, for less cash. And similar to like-minded Asian originators like mhdt (DACs), Jasmine Audio (phono preamps and amplifiers), and Melody (preamps and amps), all of Ling Xiao Nan’s implementations are informed by music listening and in-depth inquisitiveness seeking more fidelity than he previously delivered at any given time. Just like Sean Casey.
Ask questions if you have them.
Phil
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