Not that I've felt particularly idle, but I've found another(!) potentially useful feature to add to the T-Amp, and it's all my sister M's fault. See, she's getting married next weekend, and I'm DJ'ing the reception. I'm not a professional DJ, I just have a decent MP3 collection and an inability to say no. As I think I covered elsewhere in this blog, I DJ'ed my friends S & J's wedding, and used an older amplifier that I have to drive the speakers, along with the two Sony subwoofers I had in the house. In the intervening time, I've built a pair of subwoofers, and they're currently doing duty upstairs in the bedroom while the two Sony subs are downstairs with the big-screen. The problem is that the amplifier is a 1989 vintage (last year in college), so it doesn't have a dedicated subwoofer output. Both the Sonys and the Triskas can either take in line-level input, or speaker-level input, and I've had to use the speaker-level input as a pass-thru to the mains, which seems wasteful, since the subs are active (have their own internal amps). The signal path looks something like this:
I want to use the Triskas because I don't want to tear down my home theater setup, and they have plenty of power to do the job. They have an adjustable low-pass built-in so that the sub only reproduces the lows, but unfortunately the full-spectrum signal gets passed on to the mains. I want the bass to thump and the mids and highs to be unmuddied, so letting the subs be solely responsible for the low end seems like the best solution.
Being a fan of Parts Express, I looked, and lo and behold!, a solution. They sell a pair of 200 Hz high-pass line-level crossovers designed to be put between the source and the amplifier. Since the Triska subs are active (have their own power supply and amplification), I can split the signal out of the mixer with a Y-cable, plug the unaltered signal into the subwoofer's line-level input directly, plug the crossovers in just before the amp, and hook the mains up to the amp directly,where they'll only reproduce anything 200Hz and above.
The mains will be happier with less low-end work to do, and the subs will be more or less independent. The downside is that I won't be able to adjust the volume from the amp, but since I'm using a mixer anyway, that's not a big deal.
Okay, I told you that story to tell you this one. Naturally, since I ordered the high-pass filters, I got to thinking that the reboxed T-Amp might benefit from the same kinda setup. Or put another way, I wondered how hard it would be to give the T-Amp subwoofer output ports. So, of course, that led to another switch, another set of RCA jacks, and the filters. Since I've reached the point where keeping the connections in my head is getting hard, I produced two block diagrams detailing the internal circuitry.
Diagram #1 is the rebox project I'd more or less settled on in the last post. Independent power, left and right volume, three selectable inputs, spiffy blue LEDs for everything.
Diagram #2 adds the subwoofer ports and the switchable 200 Hz high-pass. Of course, this design relies on the subwoofer being A) active and B) capable of accepting full-spectrum signal and internally low-pass filtering it at least 200 Hz (wouldn't want a frequency gap), but since I'm building it for me, and all of my subwoofers are capable of that, it's not much of a hurdle.
Requirements creep is going to end up killing me, but I think this is a good addition. I'll make my final decision after I get my Parts Express order in and test the wedding setup. If the filters do good there, I'll definitely have to score another pair and add them to the rebox.
And finally, yes, of course, I'm tossing around the idea of building another Triska sub with the same walnut veneer that I'm using for the amp, which of course leads me to think about reboxing the speakers I'm using with it, to also have that same walnut finish...seriously folks, it's a sickness with me. I like to tinker, and I like things to match.
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