Mesa/Boogie Subway TT-800 Owner's Manual page 7

OVERVIEW: REAR PANEL
On the rear panel, you will find the power switch, and the AC mains inlet on a standard IEC "C14" connector. The SUBWAY TT-800
contains an auto-ranging universal power supply that can accept and operate on any voltage between 100-120 volts & 220-240 volts
AC, 50/60Hz without the need for any user adjustments or fuse change. This feature makes these amps ideal for the international
touring musician who plays in a variety of global regions. The only thing necessary to make the amp work is the correct power (mains)
cable that matches the power outlet/receptacle of the region. It is important for the mains power to be grounded/earthed for safety
as well as for EMC reasons.
Next are parallel connected NL-4 SpeakOn™ connectors, which are wired with the amplifier positive to terminal "1+" and the amplifier
negative to terminal "1-". An IMPEDANCE SELECTOR switch provided to properly match the power amplifier to the load.
The SUBWAY TT-800 is equipped with a HEADPHONE output, which will drive all common headphones and IEM ear pieces between
8 and 32 ohms (and can be used safely with no speaker cabinets connected to the head), a MUTE/CHANNEL SW footswitch jack
that mutes the signal when the tip is shorted to the sleeve and switches channels when the ring is shorted to sleeve. Additional con-
nections are provided for individual serial CHANNEL EFFECTS LOOPS, an AUX input, and a TUNER output.
One feature that sets your new SUBWAY TT-800 apart from the rest of the market is the inclusion of a two studio grade XLR balanced
DIRECT OUTPUTS. Unique to this amp is that both DI outputs are tube driven, the first is pre eq and pre channel switching, the sec-
ond is post channel effects loop, volume and channel switching so that the signal automatically tracks channel switching and channel
volume balance, even if an external preamp is being used in place of one or both on-board preamps. A MIC/LINE level switch and pin
1 GROUND LIFT switch is provided on both DI outputs. Circuit attributes include full phantom power protection, high RFI immunity
and extreme tolerance to ground potential differences.
Another feature carried over from the Subway WD-800 is the inclusion of a USB charging port, which allows you to charge most USB
connected devices. This can be handy when rehearsing with an MP3 player, tablet, or phone. With a suitable converter cable, USB
power can be used to power pedals and outboard devices.
OVERVIEW: TUBES / VALVES
The SUBWAY TT-800 uses specially designed circuitry that replicates the uniqueness of our earlier legacy designs, but doing so in
ways that allow us to exploit advantages of modern lightweight technology while remaining faithful to Randall's vision. This involves
a type of design called "blueprinting", where we take the response curves of the original circuits and overlay response curves of
prospective new circuits to match up the various parameters (including frequency, filters, dynamics, linearity, clipping/overdrive re-
sponses). Once we matched up the curves as closely as we can, we shared these results with original design team (yes, many are
still here!) to get a sense of what differences they might have preferred, with the benefits of hindsight and newer technology. This
included extensive discussions regarding evolutionary changes in requested feature sets, music styles, playing styles, speakers,
instruments, expectations, and player needs. The result is that these circuits, using 12AT7 and 12AU7 tube types, were consistently
chosen as meeting the above criteria best. The 12AX7 variants just didn't have the necessary performance parameters to match the
target curves with the newer circuitry, and may not bias up properly like a 12AT7 or 12AU7.
V1: This tube handles the input gain and buffering functions, and is located after the deep and bright filters. Generally, this tube is not
overdriven except with the GAIN SWITCH in the high position, with a high output bass and an aggressive playing style. In general,
a 12AT7 will have slightly more complex harmonics and add a little more texture compared with a 12AU7 in this position. A 12AU7
will typically be a little tighter with a lower ratio of harmonics which may feel a bit more articulate and open with a "simpler" feel. The
amp ships with a 12AT7 in this position.
V2: This tube handles all of the BOOGIE CHANNEL gain as well as driving the tonestack eq. network. As the GAIN CONTROL is
turned up you will reach a point where this tube will begin to overdrive. Given that the channel is strongly based on the Mesa Bass
400/400+ topology, this will produce that classic Mesa Bass 400/400+ signature tube growl. Generally, a 12AT7 is the preferred tube for
this position because it tends to overdrive a little bit earlier and has a bit looser feel to the overdrive. If you prefer a cleaner, punchier,
less colored tone when driven hard, a 12AU7 may be a better choice. The amp ships with a 12AT7 in this position.
V3: This tube handles all of the SUBWAY CHANNEL gain as well as driving the Baxandall eq. network. As the GAIN CONTROL is
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