A unique offering in dr. z’s ever expanding line of hand-wired tube amps, the Z-Plus resulted from a request by Joe Walsh for a new amp to use on the Eagles’ 2018 tour. Walsh famously used small Fender tweed combos on many of his legendary recordings, so the starting point for Dr. Z’s Mike Zaite was classic single-ended class-A architecture, but with his own twists on a design that would also reflect Walsh’s appreciation for vintage hi-fi audio amps.
The result was the Z-Plus, a parallel single-ended amplifier that uses two 6V6 power tubes in true class-A configuration. Imagine two single-tube tweed amps in one package and you’ve got the idea. Of course, bringing the concept into something befitting Dr. Z required that the amp be its own thing, so along with a half-power switch, tube-driven reverb, and an effects loop, the circuit housed within the custom aluminum chassis also reflects the builder’s typically high level of quality and attention to detail. The hand-soldered connections on the terminal board are neat, and the list of top-grade components includes German-made F&T electrolytic caps, a PEC pot for volume control (the other pots are Alphas) and an output transformer made especially for this amp that uses highest-grade M-6 stacked laminates. (Stacking factor is the ratio of the actual volume of steel in a transformer stack—not including air or insulating materials—compared to the measured dimension of the stack. The M-6 designation means that the laminations are smoothly finished everything else in the assembly process has been optimized to produce a very high-grade unit.)
The Z-Plus LT Combo on review here has a slightly larger cabinet (22.5” wide x 19.5 high x 10.5” deep) than the Studio Combo version, and is available with the standard, Eminence-made Z 12 speaker or a Celestion Alnico Blue, which adds $200 to the price. Since Walsh specified the Celestion for his personal amp, we opted for it too.
Tested with a Gibson Historic ’59 Les Paul, a G&L ASAT Classic (with Seymour Duncan pickups), and a Fender Strat, the Z-Plus offered up excellent tones with no fuss. Being a true class-A design—as opposed to an amp that is biased “toward” class A—it has that inherent quality of adding a layer of second-order harmonics to the sound, and you can hear it in the complexity and dimension this amp delivers. The Z-Plus has good clean capability too, and, in 15-watt mode, there’s headroom aplenty for jazz and other styles with the Volume knob kept around 9 ’o clock with the Master turned up. Advancing the Volume into the breakup range brings juicy texture into the brew, and pushed further into saturation, the Z-Plus’s grind gets more intense and the feel more compressed, yet you can pull right back to a cleaner tone by rolling down the guitar volume.
This is a fairly loud amp when cranked, and the half-power setting is handy in situations where you want to keep a lid on the volume without cutting back on power-tube distortion. The passive tone controls are augmented by a Cut control that attenuates high frequencies in the output stage. Because it operates independently of the tone stack, you can still use Cut even when the EQ section is bypassed via the included footswitch. Bypassing the tone stack elicits more gain from the circuit, and having it on a footswitch lets you click between cleaner rhythm tones and more heavily saturated sounds for solos, slide work, etc.—effectively turning the Z-Plus into a two-channel affair. There’s even a knob on the side of the footswitch to adjust the amount of EQ bypass. Another great feature is the tube-driven spring reverb, which sounds excellent whether used for a whiff of airy reflection or for super pinging surf effects. The Celestion Alnico Blue speaker is an excellent match here with its bright, ballsy response, and the total package adds up to be one of the most thoroughly enjoyable amps I’ve played, and an easy Editors’ Pick Award winner.
JOE WALSH ON THE Z- P LUS
> “I recorded ‘Funk 49’ with a Telecaster straight into a blackface Champ with an 8″ speaker and one output tube, and that’s why it sounds like it does,” says Joe Walsh about what he was seeking when he asked Dr. Z founder Mike Zaite to design a new amp for him. “That sound mystifies most guitarists. Single-ended amps can be magic in the studio, but they don’t work at all for live performance. I call up Z sometimes and we talk amps, so I said to him, ‘How do we get a Champ sound at stage volume?’ As usual, Z goes, ‘I don’t think you can do that, but let me think about it.’ Then, he calls me in the middle of the night and says, ‘I’m in the shop, and I’ve got a couple of ideas. I’ll get back to you.’ The result was two output tubes wired in series, which keeps the amp single-ended, but it’s way over twice as loud. No push-pull, no phase-splitter, no biasing issues—none of that. It’s a high-powered Champ offering a world of new sounds with any pickup. You should hear ‘Funk 49’ through it. Thanks, Z. U da man!”
MODEL Z-Plus LT Combo
PRICE $2,195 street (as tested, with optional Celestion Alnico Blue speaker)
CHANNELS 1 (w/footswitchable EQ bypass)
CONTROLS Volume, Treble, Middle, Bass, Reverb, Cut, Master
POWER 15 watts, switchable to 7 watts
TUBES Four 12AX7s, one 12AT7, two 6V6s, 5AR4 rectifier
EXTRAS Outputs for 4Ω, 8Ω and 16Ω cabinets. Effects loop. Half-Power switch. EQ bypass jack (footswitch included)
SPEAKER 12″ Z 12 (made by Eminence). Celestion Alnico Blue upgrade ($200) WEIGHT 42.26 lbs
BUILT USA KUDOS Awesome sonic complexity. Excellent reverb. Variable EQ bypass footswitch.
Dr. Z Z-Plus LT Combo
Source: Guitar Player