LOOP RETURN: This input comes in after the Input Selector and just before the Stingray iTube’s Balance and Volume
controls. If you have all your sources going into another external preamplifier, or even a Home Theater surround processor,
then you could plug that preamp’s outputs here and let the Stingray iTube just function as a stereo power amplifier when the
Loop is active (see the previous page for more information). The Volume and Balance controls still function in this mode. The
REC OUT and LOOP RETURN function as an insert point or effects loop, meaning you can insert something like a crossover,
equalizer, or you can even monitor off your tape deck’s 3rd head using the INSERT button on your remote as a tape monitor.
*NOTE: If you are using Input 4 (iPod) and REMOVE your iPod, this input will automatically mute itself. If you are using the
LOOP RETURN for an extra source, that source will also be put into mute. To disable this inadvertent mute, simply select
any of the other 3 sources with the Input Select knob and the LOOP RETURN will be unmuted.
SUB OUT: This is a line level output after the Stingray iTube’s volume control. Use this output to feed the input of your sub-
woofer amplifier. The signal level of the output follows the main volume control in the Stingray iTube so that if you change
the volume control on the Stingray iTube, your external powered subwoofer amplifier will also track and change volume.
Remember this is a LINE LEVEL output, not a speaker output. If your subwoofer only has speaker level inputs on it, then
you need to drive it with the speaker outputs on the Stingray iTube. Use of the headphone jack mutes this output. *NOTE: Do
not use a Y-cable to connect a mono subwoofer to the subwoofer outputs. This will mono the main output from the amplifier.
Instead, just use a single channel to drive a single powered subwoofer input, or use the speaker level inputs off the Stingray
binding posts. Alternately, you could use an external Stereo to Mono combiner such as the RDL TX-LC2 Audio Combiner.
This would sum both Left and Right signals and provide a Mono balanced output to drive a powered subwoofer input. If you
need to drive an unbalanced input, use the (+) and Ground outputs.
TRIODE / ULTRALINEAR SWITCH: Located on top of the unit, just above the speaker posts. This switch changes the
configuration of the output tubes and how the screen grids drive the output transformer. Triode mode hooks the screen grids
up to the output tubes’ anodes and will give you around 20 watts. UltraLinear, also known as “Partial Triode”, connects the
screen grids to the UL taps on the output transformer’s primaries and will yield around 40 watts of output power. Triode mode
tends to give you a more etheral and delicate sound while the UL mode has a more aggressive or punchy sound. Feel free to
experiment and pick whatever operating mode you like the sound of best in your system. What will “sound best” really de-
pends on your system and your room and your speakers and your tastes and what you are looking for. We do not suggest you
play with this switch all the time. You should never switch up and down rapidly as there are high voltages on this switch, and
you’ll blow something up quickly by nervously fidgeting with it. We strongly suggest you pick the setting you like best and
just leave it there.
B+ FUSE HOLDER: Should you need to replace this fuse, simply insert a flat-head screwdriver in the slot (after making sure
the unit is powered down completely, of course) and turn it counterclockwise. The fuse holder should pop out with the fuse.
Replace the old fuse with new one, push the holder back in, and turn the screwdriver clockwise to lock.
SPEAKER POSTS: The speaker connection posts are on the back side panels. The RED is positive and WHITE (or black) is
negative (ground). Be sure you have speakers (or a 4 to 10 ohm load resistor) connected to these terminals before powering on
the Stingray iTube. Tube amps (unlike solid state) require a speaker if there is any chance there will be a signal applied.
Watch out for reversing the positive and negative wires either at the amp or speakers (unless you want to simulate a re-
cord company executive’s office hi-fi). The lows get lost, and the image is very weird. If in doubt, try reversing one channel,
the way with the most bass is correct.
These terminals will accommodate most thicknesses of bare speaker wire and most U shaped terminals or banana
plugs. The only thing that they don’t like is thin wire. You should avoid thin wire for speaker cables in general. Use at least
18 gauge (18AWG) or heavier. Bigger wire has smaller AWG numbers. Be sure that the top bolts are tight, but avoid over-
tightening that might be difficult to undo or may damage the posts. In other words, firm as “strong finger tight” but less than
“big wrench tight”.
These outputs are appropriate for speakers rated between 3 and 10 ohms which includes all those 4 and 8 ohm speak-
ers. For reference, the amp design and output transformers were optimized for 5 ohms. You’ll get a little less maximum power
on either side of 5, but don’t forget that your speaker manufacturer is giving you a nominal impedance figure when he tells
you that you have “an 8 ohm speaker” which means your speaker’s actual impedance swings wildly vs. frequency all over
the place. In real life, we have found 5 ohms to be a good place to be for most people. If you have some wacky speakers that
hit strange extremes, then you might be a good candidate to order some custom other-impedance output trannies from our in-
house magnetics department.
S-VIDEO OUTPUT: Located on the Left-Front panel. If a video (or photos) are being displayed on the iPod, they will also
output to this jack. Check your local RadioShack (or equivalent electronics store) for S-Video cables to help you get video
from the Stingray iTube to your TV or computer monitor. *NOTE: Certain newer generations of the iPod may not be able to
send video through this jack due to circuitry changes in the iPod itself. Generally speaking, any iPod produced before July of
2007 should be able to export video with no problems.
HEADPHONE JACK: Located on the Right-Front panel. Plugging headphones in will mute the speaker and subwoofer
output.
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