Sun Storm progress

Sun Storm prototype #5 is now complete and will shortly be shipping off to it's owner, Todd.  This prototype vastly outperforms its predecessor in just about every category.  The most obvious visual change is the addition of a 3rd vacuum tube... a large 12BH7.  This extra tube is responsible for increasing the current of the compression control voltage.  It was necessary to achieve a faster attack time and more compression.  The extra tube required a redesign of the onboard power supply in order to facilitate a 3rd B+ high voltage source.  Since Todd wanted a mono compressor I tried out an idea with the link switch.  Instead of providing stereo linkage, it makes the compressor act as a limiter when engaged.  The compression knob acts as both the threshold and the ratio, although it's max ratio isn't as high as the limit switch.  The next prototype will be stereo and the link switch will do its intended job.  So, for the next build I'll need to figure out something different with the faceplate in order to cram another switch on there for limiter mode.   Speaking of crammed, take a look inside.

With each prototype I reduce the wire count by transitioning circuits to circuit boards.  It's a lot of work designing circuit boards and it can get expensive and time consuming when there's mistakes.  The goal is to have the fewest wires possible.  I have a lot of work to do before this is a final product, but sonically it stacks up.
It actually sounds really great and works well on a lot of different sources.  The only issue I found in the studio with this compressor is the attack time isn't quite fast enough to perfectly grab super fast and loud transients, ie: a loud strike of a hard pick on a palm muted bass string.  However, it works great on drums.  I especially love the punch and tone you can get out of a kick drum with this.  I was able to get super fat snare sounds with tons of crack too.  It doesn't behave like an LA-2A at all.  I couldn't get the compression style to match.  The closest setting worked really good on vocals and that was with the fastest attack and slowest release.  I'm super pleased with how well this turned out compared to the previous prototype.  Here's a simple comparison: 

Proto #4
​THD+N = 1.7%
f response = +/-2dB from 20Hz-23kHz 
Attack range = 10ms - 15ms
Max compression = 8.6dB
Tube compliment = 12DW7, 12AX7 

Proto #5
THD+N = 0.341%
f response = +/-1dB from 7Hz-24.3kHz. -3dB@ 5Hz & 29kHz
Attack range = 1ms - 51ms
Max compression = 20dB
Tube compliment = 12BH7, 12DW7, 12AT7