Mods to XTP Trifecta 4200 4-channel amp

boaterdad said:

Hello, forum noob here. I'm a physicist but do mechanics, not electronics, so go easy on me.

I searched these forums and read through what seemed appropriate, like this thread.

My son and I are putting together a relatively affordable stereo system for his wakeboat, an older Ski Nautique. The system will consist of the following:

200W x 4 ch. @ ? ohms amp driving four speakers in the boat
125W x 2 ch. @ 4 ohms amp driving two tower speakers
self-amplified subwoofer

My question is about the first item. The amp is an XTP Trifecta 4200. It is being "re-purposed". XTP was designing a system with this amp and tower speakers which had midwoofers and HLCD horn tweeters driven by separate channels of the amp. So channels 1 and 2 were to drive the midwoofers, and 3 and 4 the tweeters. The speakers were never mass produced, and the amps sold off. I actually got 2 new amps for 27 bucks each at an auction.

The manual is awful. I don't know if the 200W is peak or RMS (don't really care), and if the amp is rated for 4 ohms or 2 ohms minimum (do care).

Channels 1 and 2 have a high pass filter (HPF) that is adjustable between 70Hz and 300Hz, which works great for our use. Channels 3 and 4, meant to drive the tweeters, have a HPF adjustable between 2300Hz and 3000Hz, which is of course terrible for our use, where we are trying to drive combination speakers, each with a midwoofer and dome tweeter (and I assume their own crossover inside).


What I have done on the test bench:

1. Tried bridging. Bridged 3 and 4 still go through 2300Hz HPF.

2. So now running two 4 ohm speakers in parallel on each of channels 1 and 2. Not sure if the 2 ohm impedance will burn out the amp long term. Oh well, I have a spare amp.


HERE'S WHAT I WOULD LIKE TO DO:

I want to change the channel 3 and 4 HPF to be just like the channel 1 and 2 HPF. Move it down to 70Hz to 300Hz.

OR, move it to a fixed 100Hz HPF.

OR, just bypass it completely.


PROBLEMS:

a) I cannot locate a circuit diagram.

b) I know what HPF circuit diagrams look like on paper... beyond that, I have no idea what I'm doing.


I guess my questions are... how would I identify what components make up the high pass filter(s) for channels 3 and 4, and... what would I do to change them (e.g. different R and C values?) or to bypass the filter(s). I know it's tough without a circuit diagram, but maybe some general guidance could be given, or I could open it up and take some pictures...


Do I have a prayer? If not, I'll leave the speakers in parallel and cross my fingers. It's a shame to ride two channels hard while two are loafing, though, just because of that doggone HPF.

Thanks in advance.

Steve

Click to expand...