A Power Amp for the 3-Way Classic
The schematics above is from a Hifimediy T1X4, TK2050 4-channel STA508 board. I have used this board in another DIY build and I will scavenge it to build a combined active filter and 4 channel power amplifier for my 3WC. I will also scavenge another DIY build for the transformer, power supply and a "thumpinator". Below is a picture of the "woody" 4-channel amplifier (bottom) and active filter (on top) that will act as donors for this build.
I decided to use a similar cabinet as the one I used for my PreFUNK preamp. This is what the inner box looked like wired up the first time. I was a little bit worried about having the active filter in the same enclosure as the switched power supply for the power amp. I therefor used a "Faraday cage" housing the active filter board just like the one I made for my preamp. Hopefully better than nothing.
This is what it looks like with the outer cabinet fitted (from the front and the back). I used Neutrik speakON NL4MPR connectors instead of the more common speaker binding posts. Not as generic but very convenient when running 4-channels in BTL. Faceplate from Schaeffer AG (that would be Front Panel Express in the US) made using their Front Panel Designer software. I named it PwrFUNK 101 to go with my PreFUNK 101.
Everything worked just fine except for a loud thump at power off! I have used the Hifimediy T1X4 before but only with a pair of Single Supply BTL Amplifier Speaker Protection boards (Rod Elliott's P175). I have had no problems with thumps at power on or off with these boards. I didn't think I really needed them but now I realized that I do. The only problem is that I did not design my P175 boards with real estate in mind. It will therefor be tough to fit them in this box with the current layout. Back to the drawing board...
After trying a couple of alternatives, this is what I settled for. Amp board removed and everything that might fit under it moved to make way for my gigantic P175 boards (bottom middle).
Then a piece on 4 mm plywood on 25 mm distances to lift the amp board on top of it.
A couple of hours later (to hook everything up) and it was finally time to stack the 3WCs on top of the sub-woofers. My oldest daughters first comment - dad, that didn't turn out good, they look like a pair of droids! And for once I had to admit that she was right...
So the sub-woofers had to go, great concept lack in execution. The 3WCs are standing on the floor right now for a first listening impression. The PreFUNK + PwrFUNK combo is feeding them and there is no lack of bass, at least if you push them up against the wall like this.
My first impression is great versatility. This works well with different kinds of program material on high as well as on low volume. Sound is very clean and balanced. Great bass, maybe a small hump down low. I will add some lining inside the cabinets and move them further out from the wall. It is going to be really interesting to continue to measure and tweak both the PwrFUNK and the speakers.
