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Now let's do a walkabout of the back panel: the inputs and outputs on the back panel reflect (pun intended) the mirror-image, dual-mono circuit inside the Steelhead with their positions to the left and right of the chassis. To the extreme right and left sides of the chassis are the outputs, with one pair of fixed outputs that can go direct to a preamplifier if you don't wish to use the Steelhead's preamplifier capabilities. There are two pairs of variable outputs for a pair of power amplifiers or alternatively, to a power amplifier and line level subwoofer input when using the Steelhead as a preamplifier. Just to the inside of the outputs are three pairs of inputs. Two are for moving coil phono cartridges labeled MC1 & MC2, one pair covers a moving magnet phono cartridge labeled MM. That's great for the vinylphile. You can run three different tables or tonearms into the Steelhead and switch between them to your heart's content. There are two ground points available at the center of the back panel, a black circuit ground terminal and a green chassis ground terminal. There's also a third gold chassis ground connector to the left of the two main ground terminals for flexibility. There is a link between the co-located ground terminals which are intended to remain connected under normal operating conditions. If you get hum in the system, they can be decoupled to trace the hum's origin. There's no right or wrong way of connecting your tone arm to any of them. Just pick the one that provides the quietest connection.
I've always felt it important to hear from the manufacturer about what makes their product tick. No other person can express the inner workings of their creation in quite the same way as the manufacturer. I asked EveAnna if she could walk us through the Steelhead's circuitry (you can follow along the Steelhead biology lesson with the accompanying photos):
"The Steelhead was designed with an outboard power supply to keep the sensitive low-level audio electronics away from things like power transformers (those can radiate magnetic fields adding unwanted hum to the audio) and away from diodes and regulators which add more heat to the critical audio parts. In the external power supply, the mains voltage comes in and hits a little flat-pack power transformer whose job is to step down those big AC wall voltages down for a little keep-alive circuit so that when you press the sleep button on the Steelhead's audio chassis, a pair of relays fire and the big main power tranny comes on the scene to provide all the working voltages for all the different power supplies used to run the unit (or if it is already awake, it goes to sleep).


"All these supply voltages are rectified, filtered and regulated in the power supply chassis, with thoughtful "okay" status LEDs glowing on each rail before running up the umbilical cord to the audio chassis where they mate with a super-beefy 16-pin screw-on plug. Additional filtering takes place inside the audio chassis. Those 8 big black 330uF 350V caps on the audio board made for us by Cornell Dublier are doing some of that for the high voltage B+ rails. More joules, more impact...

"So, with the unit powered up and the delayed warm-up mute circuitry done with its cycle, the Steelhead is ready to receive some actual signal voltage! Selecting one of the input buttons on the front panel causes the corresponding relay at the back panel to allow that input to enter. The first thing the audio signal sees as it makes its way towards the first amplifying stage are a bunch of capacitors switchable to ground by those two clever x100 and x10 labeled knobs on the front panel. The binary switches are located right at these capacitors on the center back PCB. The shafts of these switches are connected to the faceplate's knobs by long garolite extension shafts. Doing it this way keeps the audio path as short as possible, even in this case where we aren't even exactly going through these loading caps. These switching capacitors are being selectively shunted to ground when you dial up which capacitance load you want.

"Next, if you are entering via one of the MC inputs, a second relay sends your tunes through a paltry few inches of silver-screened very low-capacitance cable provided to us by Synergistic Research into our Manley 918A PC poly-screened multi-tap autoformer. We make this exotic part right here at Manley Labs in our own magnetics department, where we also design and make all of our audio transformers and chokes used in all our gear. The 918A has 5 main windings on the primary side, each selectable by the Load Z knob on the faceplate (again coupled to the gold-contact Grayhill switch by a garolite rod, and again keeping the audio path as short and pristine as possible.) Each winding will present a different impedance to the incoming signal and also step up the signal for some nearly penalty-free gain. (By the way, the part number "918A PC" is named after Police Code 918A which means "escaped mental patient", in case you were wondering...)

"If you have entered via the MM inputs, at this point you are on another deck of this same load switch instead, choosing corresponding metal-film resistors for your resistive loading needs. Now we are ready to hit some tubes! But first we're going to pass through a WIMA cap into the gate of a FET acting as a current source for one of Mr. 6922's triodes. One of the source resistors of this FET is relay-switchable for a 5dB gain change, to jump from 50dB of total gain to 55dB; the other 10dB and 15dB gain additive switching happens in the following nearly identical FET + triode stage. However, before the tunes make it to the next amplifying stage, they first must pass through an intricate L-C-R (choke-capacitor-resistor) passive EQ network for the RIAA EQ curves and all four poles are indeed addressed in the design. There are two adjustable capacitors and a trim pot to completely nail the curves and additionally each component in the RIAA networks is preselected and matched left to right for total accuracy.

"Something to note here while staring at all these parts is that each component in the Steelhead was very carefully selected by Mitch when he designed the unit. (He's really tight with his money but not so stingy with mine - trust me :-) Some audiophiles might want to jump in here and replace the two WIMA caps in the signal path. (I thought about it!) However, when they do this, they risk screwing up the DC blocking as these two particular caps were chosen for superior DC blocking behavior over alternative metalized, rolled film-and-foil, mica, ceramic or "more audiophile" capacitors. We tried a bunch of them for this particular application before declaring these particular WIMAs the winners. Another example is the signal wire choice. After one CES a few years ago, I gathered up a whole slew of "audiophile" cables, looking for the lowest capacitance per foot in a 2-core shielded wire. Half the cable companies had no clue what the pF/foot of their cables was (which I found as amazing as if I didn't know what the output impedance or power output of one of our units was. I mean, that's a crucial technical parameter to know! Sorry, I digress...). So I got all these cables and we went through and measured this capacitance-per-foot value and this particular silver wire won the shootout. And why was this capacitance thing so important to us? Well, when you're working with high impedance, as we often do with tubes, those picofarads adding up with every inch of your cabling are going to start rolling off your high frequencies. So that's why that battle line was drawn. There's more to design and component choice than meets the consumer's eye to be sure.

"Back to the tunes in the Steelhead: A host of relays along the top of the main audio board perform all these gain switching, mute, dim and sum jobs, and all along the back of the faceplate is a bunch of logic circuitry required to make all this happen and at the right time, at the push of a switch button. All those grey ribbon IDC connectors you see in there snaking around the left side of the chassis are for carrying control and supply voltages for the logic and relays (not the tunes).


"Now we're all amplified and ready to get out of the unit - but first we need to buffer those tunes and convert the high impedance signal into a super low impedance/high-current output, strong enough to survive what some other foolish audiophile cabling might want to try to do to it. For this task we call upon our fave output stage, the direct-coupled White Follower. Here we have used the 7044 or 5687 tubes which are especially endowed to deal with high cathode voltages, which the upper triode does possess compared to its internal heater element. (Again: a part -- here a tube -- specially chosen as the best part for the job.) The White Follower ejects the audio out at a fabulously low impedance of less than 20 ohms. To help drive high capacity audiophile cables, we have a resistor of 47.5 ohms in series with the giant audiophile 30uF MultiCap® (which removes DC voltages), raising the actual output impedance to less than 70 ohms. This circuit can drive anything now, tube, solid state, it doesn't care - even several microfarads of cable. I love this output stage! We use it extensively in our gear. So now you're out via the fixed output if you are done with this Steelhead.
"But stick around inside for the really clever part. At this point in the circuit comes your line input! This, if you light up the line button -- or the audio from the amplified, EQ'd, and buffered RIAA signal if you don't -- is selected by relay to go to the lovely Noble volume control. At this point in the circuit, we are DC-free and this is why the dim and sum functions live here. After the volume control, we pass through a great-sounding 3uF MultiCap® (to keep the DC on the top grid of the White Follower from reentering our DC-free zone,) and then into to the second complete White Follower output stage which exits at the variable outputs. Even all those RCA jacks on the rear panel are our own design, manufactured for us nearby in Montclair, CA. And that's nearby to us in ChinO, not ChinA!"
Thanks, EveAnna - that was an awesome tour! Looking at the interior, you really get a sense of how beautifully the Steelhead is put together - a work of art!