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Technolink TC-780i Online Manual
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TC-780i Applications and Usage

The TC-780i is a small (3" x 1.75" x .75") stereo line amplifier designed for either mobile or home use.  Most users will use it to connect a MP3 player, iPod or other portable audio player to an existing auto or home stereo. Doing so is simply a matter of plugging the player into the front panel jack, and adjusting the level control for best  balance. Because the TC-780i provides considerable gain, it can correct level mismatch issues that often cause portable players to be lower in volume than other sources. A second rear panel  input (selected automatically when nothing is plugged into the front input) allows the TC-780i to be used even in situations where all available inputs are already occupied. The mobile installation hardware included allows mounting either over, under or in most dashboards. The underdash bracket can also be used to attach to a in-home stereo cabinet or entertainment center, or the TC-780i can simply be set on a shelf.
Powering the TC-780i

The TC-780i runs on 12VDC supplied via a jack on its rear panel; a LED indicator lights when power is applied. A fused harness with matching plug is provided for in-car use; an optional AC adaptor (the same type that powers our phono preamps) allows in-home use. Although the level control also serves as a power switch, most mobile users will want to wire the TC-780i  so that power is controlled by the car stereo's on/off switch. Home users may be able to plug the TC-780i's AC adaptor into a available switched AC outlet on the stereo's rear panel; this arrangement allows the TC-780i to go on and off with the stereo's power switch. See the connection diagrams provided below for more detail.
Home Stereo Connection / Installation

Always turn all equipment off before making connections. The TC-780i can be used with any stereo, home theatre system, mini-system or other amplifier that has a line input, whether currently in use or not.  Plug the TC-780i's output cable into any of the following inputs; AUX, CD, TAPE PLAY, TAPE MONITOR, TUNER, MD (mini-disc), DAT (digital audio tape), LINE, VCR, VIDEO, DVD, TV, SAT (satellite).  Do NOT use PHONO. If the input has a third (usually yellow) jack for video, simply leave it empty. If you need to use an input which already has a source connected to it, plug this source instead into the TC-780i's rear input pigtail cord. Finally, plug the AC adaptor first into the TC-780i and then into a wall outlet. There is no home "installation" required, although the underdash bracket can certainly be used to firmly attach the TC-780i to a shelf or entertainment center. Double-stick tape or velcro are other mounting options if using screws is impractical
. Below is a TC-780i shown permanently installed using the bracket provided, and in use with a Kenwood portable mini-disc player routed thru the video input of a Pioneer receiver.
Mobile Connection

Always turn the vehicle off and remove the radio fuse before making connections. The TC-780i  can be used with any car stereo that has a RCA jack AUX line input. Plug the TC-780i's output cable into the car stereo's input jacks. If these jacks are already in use (usually by a CD changer), disconnect and plug this cable instead into the TC-780i's rear input pigtail cord.  Connect the supplied DC cord's negative (black) wire to ground. The positive (red) wire can be connected either to the car stereo's amp turn-on lead or power antenna lead; when wired this way, the TC-780i will power off and on with the stereo's power switch. Do not disconnect anything which is already connected to these leads; otherwise your amp or antenna may stop working. If neither of these options is available, connect the red wire instead to the same point to which the stereo's switched power lead is connected; this arrangement will provide power whenever the vehicle's ignition switch is on. You can choose to use the stereo's unswitched power lead connection point instead, but be careful to turn the TC-780i's power switch off when not in use to avoid running the vehicle's battery down. Finally, plug the DC cord into the TC-780i. and reinstall the radio fuse. See the TC-780i Gallery below for installation location and mounting ideas.

Don't have a car stereo with an AUX input? The TC-780i can be used with a cassette adaptor
or RF modulator like the ones above to allow playing thru any car stereo that has a cassette deck or FM radio. If you are already using one of these with your iPod or MP3 player and find that it's annoyingly soft compared to the radio or when playing a tape, the TC-780i can fix this level difference. You'll need a couple of adaptors available at Radio Shack to connect to the output cable of the TC-780i. Stock numbers 274-883 and 274-886 used together will work with most cassette adaptors and many RF modulators.
Mobile Installation

 Both the input and output cables can be extended if needed with ordinary patch cords and butt splices like the ones shown at the bottom of this page. The TC-780i  comes with two front panels; the  installed one used for underdash and home installations, and another for in-dash mounting. Changing panels is accomplished by removing the volume knob (pulls off easily) and the two screws on the TC-780i's rear. Slip the installed panel off and replace it with the other one, then reinstall the knob and screws.

Installation under or on top of a dashboard requires picking a spot and using the supplied self-tapping screws to mount the bracket. If using a drill to facilitate making the holes be extremely careful not to penetrate anything but the dash material. The TC-780i mounts to the bracket using the supplied allen screws and wrench. Note that the unit can be swiveled in the bracket to suit different mounting needs, and that reversing the bracket provides more choices.

In-dash installation requires cutting a hole the same size as the underdash (smaller) front panel; use it as a template to mark the hole, but be conservative; better to cut  undersize and enlarge gradually to fit. Choose a flat or near flat area, and make sure there's nothing behind the dash that will be damaged or interfere. Once you have the hole cut, slide the TC-780i into the dash and mark the two mounting holes. Do not screw permanently in place until you've performed the adjustment procedure described at the right (you'll need access to the bottom trimmer control).
Adjustment (Both Home and Mobile)

After turning your stereo's volume fully down, connect your MP3 player, iPod or other audio player to the front jack on the TC-780i. If the player has a line out jack, use it. If not, use the headphone jack, and set the player's volume control to the middle of its range. Now set your stereo's volume control to your usual listening setting, and select the input to which you've connected the TC-780i. Turn the level control on the TC-780i slowly up to a level which provides approximately the same volume produced by your stereo's other sources (such as CD or TUNER). You may need to increase the player's volume setting somewhat if this level cannot be achieved with the TC-780i's control alone. Finally, if you've connected something to the TC-780i's rear input (we'll call it SOURCE X), unplug the player from the front panel jack. While listening to SOURCE X, use a small staight slot screwdriver to adjust theTC-780i's bottom trimmer control so that the level is similar to that produced by other sources. When you are done, you should be able to switch between SOURCE X, your portable player or your other inputs without routinely having to readjust your stereo's main volume control.

  • Input sensitivity: 100 mV
  • Input impedance: 30kΩ
  • Max output before clipping: 2.3 Volts p/p
  • Output impedance: 2kΩ
  • Gain; 10dB (with trimmer and output control set fully CW)
  • Distortion: 0.1% (measured with 100mV input / 300mV output)
  • S/N Ratio: >90 dB
  • Frequency response: 20–20 kHz +/-0.5 dB

Other Usage Tips

In addition to serving as a convenient method to connect and level-match a portable player, the TC-780i can also be used to improve the performance of other line level sources when connected to the rear input. The three diagrams below show how the TC-780i's additional gain can be used to compensate for weak sources and long cable runs. Note that our larger TC-780LC model is specifically designed for these applications; its higher maximum gain may make it the better choice in circumstances where its size isn't an issue and AC power is available (the TC-780LC cannot be used in a vehicle due to power supply design differences).


The TC-780i measures 72mm long by 45mm deep by 20mm high
(imagine a credit card with the thickness of a 9V battery).
The under-dash front faceplate measures 75mm long by 22mm high.
The in-dash front faceplate 
measures 94mm long by 30mm high.

What's Included
  • TC-780i with integrated input / output cables
  • Two interchangeable faceplates (in-dash and under-dash)
  • Mounting bracket with side screws and allen wrench
  • DC cord for mobile installation
  • Mini/mini-plug cord for iPod / MP3 connection
  • Mini /sub-mini adaptor (for use with sub-mini HP jacks)
  • Stick-on rubber feet for in-home use
(AC adaptor for in-home use is OPTIONAL)
Below are some sample installations and applications for our TC-780i Mobile iPod/MP3 Booster.
Click on the images to see  larger versions.
glovebox mount console mount
tunnel mount pocket
The images above show various mounting positions where the TC-780i can be fitted in a left hand drive (USA/Canada spec) 2000 Saab 9-5. In addition to those shown, several other under- and in-dash locations will work; the ones shown are simply the easiest choices we found. Clockwise from the top left; in the glovebox, in the console storage box, in the center pigeonhole (some 9-5s have an optional ashtray located here), and alongside the transmission tunnel. All of these positions can be secured either with double-stick tape, with velcro or (preferably) with the supplied bracket and screws. All except the console allow the TC-780i's built-in output cable to reach the standard radio location without lengthening. If required, extending this cable is simply a matter of using a patch cord and two barrel splices (see pix at the bottom of this page), easily obtained locally at any electronics seller. Routing wires to the Saab's radio location requires some time and effort (this car is obsessively neat about fit and finish) if you want everything hidden, but isn't beyond the DIY installer. Note the police scanner in the pigeonhole image; this is actually connected thru the rear input to the TC-780i shown, allowing scanner audio to be channeled thru the car's audio system. Just visible at the right is a white iPod articulated mount which is inserted in (and powered by) the cigarette lighter socket; its audio cable occupies the front jack on the TC-780i. This iPod when connected directly to the car stereo plays much more softly than the tuner or CD player; but when connected thru the TC-780i it is adjustable to be just as loud as other inputs. No more sudden and massive volume shifts when switching back and forth between sources...
ebrake ashtray
cubby console
The images above show various mounting positions where the TC-780ican be fitted in a left hand drive (USA/Canada spec) 1994 Nissan Pathfinder SUV or Frontier pickup. These are just a few of the possiblities with these vehicles; there's tons of room and the dashboard has lots of empty area. ALWAYS make sure the way is clear behind before cutting holes in any dashboard; in particular stay FAR away from airbags and any area which is strengthened with metal behind the plastic. Clockwise from the top left; in the area right of the steering column (some automatics have the parking brake handle here, but there is still plenty of room),  in the ashtray hole, alongside the console box next to the driver's seat.and lastly, in the cubbyhole left of the steering wheel. Yes, we know that last image shows a radar detector, not a TC-780i, but it's the exact same size, and its front panel mounts the same way the TC-780i's larger (in-dash) panel does. This particular truck already has lots of "stuff" occupying the most obvious locations; nonetheless we had no problem working around the existing equipment. All of these positions allow the supplied output cable to reach the standard radio position without lenthening. Unlike the Saab 9-5 above, this dashboard is open at the bottom, not finished; this makes running wires and cables a snap. Simply tuck stuff up and under, using wire ties to secure new work to the wire bundles already present.We won't bore you with more pictures of glovebox and console box mounting; what works in the Saab 9-5 will work in most vehicles. Bear in mind that you can also mount the TC-780i vertically (providing you don't mind tilting your head to read the lettering); this opens up all kinds of possibilities...
patch cord and splice
To extend the TC-780i's input or output cable, use a standard RCA cable patch cord
of the appropriate length and two barrel splices like the ones shown above...

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