Reboxing the T-Amp: The Parts

The parts list so far:

Parts Express:

• 060-315 SPDT Mini Rocker Switch (power switch)
• 060-322 DPDT Mini Rocker Switch (source select switch*)
• 090-278 Gold RCA Jack Solder-type w/Nut Pair (RCA inputs)
• 090-317 3.5mm Stereo Panel-mount Jack (MP3-player input)
• 090-475 Dual Binding Post (speaker terminals, 2 needed)
• 090-488 Panel-mount DC Jack
• 070-008 Ultra-bright Blue 5mm LED 1500 mcd (power indicator)

Elsewhere:

• 50K-ohm Audio-taper Dual-gang potentiometer (I've found this on eBay, from West Florida Components)
• Silvertone Knurled Knob (Radio Shack) [any knob that will fit on your pot's shaft will do, I happened to see the silver one in my local 'Shack and liked it, so I bought it]
• 3-12V 1300 mA Universal Digital AC Adapter (Wal-Mart) [really, any 12V wall-wart with a type-K center-positive plug*** that can deliver over 1000 mA should work fine, but this one looks like it could charge/power your iPod/MP3 player at the same time via its USB power port.]

This pretty much covers the basics. With the above parts, you could re-host the T-Amp into any sort of enclosure with higher-quality parts, and even add the ability to use line-level RCA inputs that most audio components use.

I'm rarely content to leave well-enough alone, so there are some elements of the design that are still in flux. For example, the dual-gang pot pretty much ensures that both channels are always at the same volume level. Instead of a single, dual-gang pot, you could easily use two 50K audio-taper pots to control the left and right channel volume independently.

In like fashion, you wouldn't have to stop at a single RCA input. With a 3P4T (3-pole, 4-throw**) switch, you could easily have 3 RCA inputs and the headphone input. With a 4P4T, you could add an LED for each input that would light when that input was selected. Obviously, the number of inputs would be limited only by the highest-throw switch you could find that could handle all the necessary poles.

No audiophile amp would be complete without some sort of VU meter for the audio channels. With this circuit and the right panel-mount meters, you could easily add VU-meters to your amp, enhancing the face appeal (at least to me...there are also LED-based designs).

Of course, you could search the web and find ways to add tone control, or graphic equalizers, but if you're driving this with an iPod primarily, you already have a pretty wide selection of EQ settings to play with. With the right crossover network before the amplifier stage, you could set up an output to a powered subwoofer. But if you wanted to get really squirrely, why not rig in a karaoke circuit? If you did, you'd want to wire in a switch that would either apply the karaoke effects or not, and you'd probably want to wire it between the input stage of the T-Amp and the output stage of your multi-input selector (so that you could karaokify anything coming from any of your sources.

Obviously, I have some thinking and planning to do, to figure out just what I want my FrankenAmp to be. But I have options, and the basic parts list is pretty static. As I make decisions, I'll add a post.


* This switch is only necessary if you want both RCA and headphone inputs. In a one-input application, this switch is unnecessary. See text for possible replacement/repurpose of this part (if a different input selector is used, and a karaoke circuit is included, this switch could be used to control whether the karaoke circuit is on or not)

** "Poles" on a switch refer to the number of independent lines the switch can handle. "Throw" on a switch refers to how many different positions those lines can be switched to. For example, a 3-pole, 4-throw switch would be able to accept 3 input lines (ground, left, right) from up to 4 sources and switch between them.

*** Type K is a 5mm outer-diameter, 2.1mm inner-diameter power plug. Most "adapta-plug" wall-warts come with this size plug, and will let you choose whether the center is positive or negative. Obviously, since you're also replacing the DC power input jack from the stock T-Amp, if you have a wall-wart available with a different size/orientation plug, you could simply purchase the correct DC input jack to mate to your transformer.