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Frontal stack and then viewed from the right side where the power switch resides on the main unit. Note old-style chassis vents.

Three closer looks at the main unit's guts.



Main unit details.
The PX4/300B—or 45/2A3—switch is on the back of the main unit right above the main RCA outputs.
The large hand-written serial number is a touch of (cough) class the piece could have done without.

A full-size view at the power supply.

Some detailed looks at the power supply unit. Since the rectifiers ship uninstalled, you'll have to unscrew the cover and
insert them before you fire things up. The rotary bias meter adjuster should be all the way counter clockwise at that point.


Given the rarity of Yamamoto's 8-pin combo socket, I was surprised to find no instructions on how to properly orient the 300B and PX4 and further surprised that Craig agreed when I suggested that this really invited user error. "Most of my tech support problems are from tubes being improperly oriented and forced into the sockets. I even get the 6SN7 put in wrong.

"I know right away when the customer says the tube was really hard to put in and there's no sound. The large pins face inwards.



"The fatter heater pins will be inline front to back and point chassis center. If you look closely at the sockets, you can tell which two pins are largest. Another strange thing about the Yamamoto sockets is that the tube pins will bottom out in the socket before the tube base is flush with the socket top."


If you were a manufacturer with repeat service issues caused by poor instructions, wouldn't you have long since rectified that? Perhaps more unmistakable illustrations than the certainly confusing bottom-view schematic above Craig had only emailed when prompted will be included in the future. That drawing doesn't even orient the socket as installed; and most users won't know a plate from a grid pin. To be sure the PX4 uses the same UX4 pins of the combo socket so it seats like a 300B. Both fat pins face inwards.


Where Craig failed far worse was mentioning anywhere in the shipment that his single-ended preouts are in fact fixed outputs. They bypass the volume control, output selector and operate even with the amp powered down. Not knowing this from the instructional sheet or—what a thought—any labeling on the amp, I promptly connected the Eddie Current via my usual RCA interconnects to a 10V-out source and amp whilst the BA's volume was carefully set to zero. Imagine my shock when 'play' didn't net mute but extreme levels. Completely caught off guard I quickly turned the output selector from line to cans to protect my speakers. That didn't cut the sound either. Hitting 'pause' on my iMac took a few seconds longer before the madness stopped. Would Eddie Current pay for damages to your equipment? I doubt it. Craig's belated and entirely unapologetic explanation that his balanced line-out can drive 100 feet of cable without loss due to extremely low impedance barely registered. I was too dumbfounded by his inexplicable carelessness and pissed that someone would take such risks with my (work) equipment. Who was I dealing with here?

As subsequent emails explained, a 35-year+ project engineer for Urei, JBL professional and such who was "used to dealing with people with a certain level of technical expertise". The Balancing Act in particular turns out to be a mostly custom-made model. Advance interactions between maker and buyer settle the desired feature set. In my case technical expertise was simply supposed to include mind reading. Craig has since committed to properly labeling his fixed RCA outputs as well as describing them as such in a new owner's manual. This made me comfortable to proceed. To properly evaluate the BA as a preamp with XLR outputs exclusively, I contacted Zu to purchase a 6-meter set of balanced leads from their newest Event line. That's because my setup of source/line gear on the sidewall and amp/s between the speakers necessitates one long interconnect. I bought an equivalent RCA lead too so that comparisons with my ModWright LS100, Esoteric C-03 and Bent Audio Tap-X preamps would eliminate cable differences.
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