Galaxy Audio Hot Spot PA5X140 and PA3

These two small powered monitors are in service at the keyboards at Hillcrest E-Free Church in Seward NE. Each have two inputs and are gain-staged to accept instrument- and mic-level signals. However, they're actually fed the line-level outputs from the keyboards, with the second input coming from the mixer in a music-plus-one monitoring arrangement.

Because the input signals are rather hot, all the gain pots are almost closed off completely, giving only a few degrees of rotation between too-loud and off. It was time to do something about it.


The PA5X140 used a C-law pot with an inverting opamp to get the large gain range needed to handle mic to line-level inputs. One end is the input, the wiper is connected to the inverting input, and the other end is connected to the opamp output. Plotted is the gain-versus-rotation of the stage using a linear pot.

The easy solution was merely to adjust the gain of the power amp from 38 dB down to 18 dB, effectively raising the as-used pot position from 5% to about 30% rotation. With only a single resistor change (next to the 1/4in TS jack), un-modding this unit will be trivial if needed in the future.



The beige-faced Hot Spot is, I believe, an ancient PA3. Even the schematic provided from Galaxy had little in common with the actual PCB. Volume control for the vintage model was the normal attenuator with make-up gain. The smoking gun, though, was the pot marking "104KA" -- a 100k linear pot. Volume controls "feel" best with an exponential R-vs-rotation slope to be linear in dB.

Quick mod #2 was adding a shunt resistor of 10k from wiper to ground to fake loggify. Rod Elliott of Elliott Sound Products calls this A Better Volume Control.

Klark Teknik DN410 parametric EQ

This unit came to me from Lincoln Berean Church where it had been in service as the parametric on the pastor's channel. The story goes that in the middle of a sermon, channel A went silent. Chalking it up to a bad channel, the next time channel B was used and the same thing happened. The installed system in the big room sounds very nice and had so far had no major issues, especially a full silence episode so this unit got black-listed as soon as it was patched around.



I received it in a dismantled state from a "no additional time available to give to this" call from their system tech. He had purchased new switches to replace a few that were a little dirty and said Klark Teknik support suggested re-wetting the vertical 4-position hard soldered connectors between the boards.

Repair was then replacing all the pushbutton switches and re-wetting the vertical connectors. This was done after screwing the boards back together into the A and B modules to avoid having stress on the joints when reassembled. Several of the connections looked possibly broken and a few of them were in fact under tension and released when the solder melted.



Since the problem was likely related to heat and intermittent connections, the only true test is to put it back into service on a "money channel" and tempt Murphy.

Last Sunday I patched it into the pastor's and the (electronic) kick drum channels at my church and tweaked away. In operation, the unit was a bit noisy to have channels enabled with no boost/cut but otherwise was the ticket for those sources. Compared to the Mackie 1604's single swept mid EQ, there was plenty of tweaking room available for a nice kick thump. The ability to narrow the bandwidth of a few EQ sections for the pastor's head-work mic was so much nicer than the mixer EQ's compromise.

Two services worth of music and sermons gave no issues, even under some mechanical stress on the case so everything seems to be good to go.

maybe this time