SUN STORM
Feed-forward, vacuum tube driven, optical compressor.
First of all, what we are looking at and talking about is an original LBA design and a fully functioning prototype, serial number 3-4. I number them by the half rack, since that's how they are built. This represents the 3rd and 4th prototype, which introduce a pile of new features over the previous prototype, as it should be. Each channel of the Sun Storm has knobs for compression (threshold), attack, release, and makeup gain. In the future, there also will be a ratio knob, but on this unit it is a 2-way switch on the back panel (as seen below). The other switches are for a high-pass side-chain filter, stereo linkage, true-bypass, and a power switch. Internally there are set-screws to zero the meter and to calibrate the gain-reduction display on the meter. I'll get into the fine details of this compressor if you read on and you'll soon find some audio examples from this prototype. Please, continue on...
All audio samples are level matched and normalized for consistency.
Download the full resolution (96kHz 32Bit) samples here:
| sun_storm_audio_samples_96k_32bit.zip |
Each Sun Storm requires 12V DC @ 1A from an external AC/DC switching power supply. Low-noise, LBA-tested 5-Amp 12V adapters will be provided with the purchase of Sun Storm prototypes. I didn't provide extra DC jacks for daisy chaining because I wasn't sure how much current would be involved and I didn't know what sort of losses to expect. I know that information now, but I don't know if there will be any power supply noise interference between channels as a result of daisy-chaining. Further testing will be required, but it is my plan for daisy-chaining to be introduced in the next stereo build.
When you switch the front-panel power switch on, an automatic timed startup sequence begins. During this initial period the vacuum tube filaments are getting warmed up with 12V for about 30 seconds before the high-voltage B+'s are automatically turned on. The front panel meter blinks with a dim backlight during this period as well. During the startup sequence, the bypass switch will function, but there will be no audio when active until the startup sequence completes. This "soft-start" helps to extend the operational life of the vacuum tubes and the onboard power supply. Each channel has an LBA designed and built multi-voltage high-voltage boost converter, which is the source of the high voltages necessary for proper vacuum tube operation.
Looking at the gut shots below you can see there's a ton of hookup wire. Over 60' per channel! The next build will have many of these wires converted over to traces on a circuit board. It's far too labor intensive with all this hand-wiring for it to be reasonably priced. I ate most of the cost on this build. I see it as R&D. The customer paid about $1600 for this one-of a kind stereo compressor. I estimate it should have sold for $4000 if I was to break even. I want to eventually have the final product sell for about $1800 for a stereo pair and have it be profitable. That will be a tremendous undertaking for me, but I'm working on it!
Looking at the gut shots below you can see there's a ton of hookup wire. Over 60' per channel! The next build will have many of these wires converted over to traces on a circuit board. It's far too labor intensive with all this hand-wiring for it to be reasonably priced. I ate most of the cost on this build. I see it as R&D. The customer paid about $1600 for this one-of a kind stereo compressor. I estimate it should have sold for $4000 if I was to break even. I want to eventually have the final product sell for about $1800 for a stereo pair and have it be profitable. That will be a tremendous undertaking for me, but I'm working on it!
There's 2 LBA transformers per channel. An RA66 serves as the input transformer and a large FS21 output transformer. The FS21 was developed specifically for this product. There are 2 vacuum tubes per channel. A 12DW7 (ECC832) (V1) and a 12AX7 (ECC83S) (V2). The first stage (V1a) is actually a 12AU7 stage. It's used here as a phase splitter. One signal goes to V2 as the audio path. The other signal goes to the second stage of V1, (V1b) a 12AX7 stage, which serves to amplify what I'll hence-forward refer to as the CV, or control-voltage. The compression knob is actually the threshold control and it controls the amount of signal produced by the second stage of V1. Loud CV signals feeding into this stage can be distorted by over-driven tube compression. After the CV departs it primary tube stage it goes to the optical control board. This hybrid tube/solid state gain reduction circuit uses a single transistor to power the release control and a second transistor to control the Gain Reduction meter. 2 transformers, 2 tubes, and 2 transistors? Yes, I felt it was not necessary or even realistic to try to add an extra dual-triode vacuum tube into the design just to power the release control and the meter. It would make the compressor unnecessarily more expensive. Maybe someday I'll make a crazy rich man's compressor, but for now I'm focused on delivering a high quality, flexible, and great sounding compressor at a mid-tier price. As it is, I'm already working on an update for the stereo linkage control that would use an integrated op-amp to help improve the stereo tracking. In the above photo you may notice each channel has 2 little blue trimmer pots on the GR control board. They are used to calibrate the front panel GR meter. The little black box with the LBA logo is the proprietary LBA Opto-Cell 1A.
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The Sun Storm is a unique design in progress. That is to say it isn't trying to be anything in particular, although it can be distilled down to the optical category. My goals were relatively simple in concept (difficult to achieve). I have a 1960's Altec variable-mu tube compressor, which has taught me a lot. Most of that teaching happened as I modified it to have more functionality. It's a cool tool, but I find it's a bit too colorful for most tasks. I also wish it was capable of much faster attack times. The Altec distorts if you set the attack too fast for it's liking. I assume this is standard with all variable-mu compressors since I spent a lot of time trying to correct that issue to no avail. Negatives aside, it has so much freaking mojo I can easily forget all its shortcomings when used sparingly on just the right source. I wish I had a compressor with that kind of mojo on every source, but not quite so much color. The Sun Storm itself is an evolution of my Op-2 Comp FX pedal, which was a dual tube optical compressor pedal. It's becoming so different now that I can't even compare them, so I won't.
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In a style like an 1176, you have to boost the gain to cross the threshold before it hits the compression circuit. The Sun Storm differs from an LA-2A in every way other than being optical at heart. You can achieve similar compression characteristics as with an LA-2A, but the Sun Storm has a less obtrusive sound in general. She has her color, don't get me wrong, but it's not as overbearing as a vintage Teletronix LA-2A. The goal for me was to create a compressor that could be very flexible in the studio, plus a tube audio path seems to be necessary from customer feedback, and it needs to be high quality and easily serviceable. I have very grandiose plans for how to evolve this compressor design into what I want it to be. Hopefully there's enough cool people out there to keep funding my crazy journey by purchasing prototypes. Keep an eye out on the used store.
All of this stuff I have been making up since October 2024.
I have been designing this compressor from scratch. Nothing else is exactly like it. Every detail. Maybe the concept has been done before... Maybe not, but I can tell you nothing else sounds like it because LBA transformers are part of the equation. I design and manufacture them in-house, which you are surely aware of. To get into what really makes the Sun Storm unique (aside from my transformers and custom parts)... from the research I've done on the topic of compression, it's how the control voltage is achieved and manipulated.
While the Sun Storm is already very developed it is still considered a prototype. Some refinement is necessary. No release date is set at this time, but you may request a prototype for a very reasonable price by simply emailing sales@lightningboyaudio.com. Your purchase will directly further the development of this product and you'll have my gratitude! Thanks for checking out the Sun Storm. Please check back in the future for updates.
Technical Information (please check back for updates):
Flat frequency response +/-1dB : 10Hz-25kHz
Noise floor A-weighted -110dB
Input impedance = 6k Ohms
Output impedance = 600 Ohms
Vacuum tubes = 12DW7, 12AX7
Fastest possible attack time = 10ms
Flat frequency response +/-1dB : 10Hz-25kHz
Noise floor A-weighted -110dB
Input impedance = 6k Ohms
Output impedance = 600 Ohms
Vacuum tubes = 12DW7, 12AX7
Fastest possible attack time = 10ms