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Designed around the THAT 4305 dynamics processor IC, the B16 is a fairly easy to build and
use compressor that is useful in a wide variety of applications. The low distortion VCA, Burr-
Brown op-amps, and state of the art line driver and receiver ICs combine to form a transparent
circuit that keeps levels under control while adding a minimal sonic imprint. An optional
transformer allows for a true floating output and some transformer color, if desired. Attack and
release timing is generated by a program dependent non-linear capacitor circuit that eliminates
the need for separate attack and release controls.
Who Should Build This Kit?
The B16 is not difficult to build, well, other than the 4305 IC...but it also is not intended for
absolute beginners. The soldering on the 4305 IC can be done by SCA for an additional
charge! You should have built at least one project on a printed circuit board (PCB) before trying
the B16. Sorry, but soldering cables doesn't count. If you've never built an electronic project
of any kind, this is probably not the one to start with. To guarantee success make sure you
have:
•
The ability to make basic voltage and resistance measurements using a digital multi-
meter (DMM).
•
At least a rudimentary understanding of Ohm's Law and the relationship between
voltage, current, and resistance.
•
Some experience soldering on printed circuit boards.
•
The patience to follow instructions precisely and work carefully.
Essential Tools
Fine tipped 20-30 Watt soldering iron w/ cleaning sponge (Hakko 936 or similar)
Eutectic (63/37) rosin core or "no clean" solder (.025" diameter is usually best)
Good-quality DMM
Small needle nose pliers
Small diagonal cutters
Phillips screwdriver (#1)
Flat jeweler's screwdriver
Highly Recommended Tools
Lead bender (Mouser 5166-801)
Magnifying glass
To adjust makeup gain, you'll need the ability to generate and measure audio test signals
between –20dBu and +20dBu. Most DAWs can accomplish this task.
B16 Compressor Rev 2.1
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Summary of Contents for Seventh Circle Audio B16
- Page 1 Who Should Build This Kit? The B16 is not difficult to build, well, other than the 4305 IC…but it also is not intended for absolute beginners. The soldering on the 4305 IC can be done by SCA for an additional charge! You should have built at least one project on a printed circuit board (PCB) before trying the B16.
- Page 2 Optional Tools Panavise with circuit board head (PV-312, PV-300, and PV-315 or PV-366) Oscilloscope Signal generator Work Area Find a clean, flat, stable, well-lit surface on which to work. An anti-static mat is recommended for this project. If you’re in a dry, static-prone environment, it’s highly recommended. The importance of good lighting can’t be overstated.
- Page 3 Use a piece of stiff cardboard to hold the parts in place while you flip the board. First, orient the board as shown. Before installing the resistors, prepare the leads using small needle nose pliers or a lead-forming tool as shown Whatever you do, don’t bend here.
- Page 4 Solder U1 taking EXTRA care to not use too much solder and create shorts! Use a microscope, magnifying glass, or cell phone camera, zoomed in, to check your work! IF YOU ARE UNCOMFORTABLE SOLDERING THIS PART, SCA CAN SOLDER IT FOR YOU FOR A SMALL CHARGE! Insert the 1/4-watt resistors.
- Page 5 Next, add switching diodes D1 through D3. Diodes are polarized and must be installed the right way around! The colored band on the diode matches the white band on the silkscreen. Next, add the protection diodes D6 through D18, the black ones. Diodes are polarized and must be installed the right way around! The colored band on the diode matches...
- Page 6 Install the ceramic, yellow capacitors. These capacitors are not polarized and can be installed in either direction, but pay close attention to the capacitor markings! These parts look alike but they are not interchangeable. Putting one in the wrong spot will not prevent the compressor from passing signal, but it can seriously impair its performance! Install the film capacitors at C16 and C21.
- Page 7 10. Install LEDs D4 and D5. LEDs are polarized and must be installed the right way around! Install the long lead opposite the flat side of the silkscreen outline. 11. Add blue EMI filters L1 through L6. These parts are not polarized and can be installed in either direction.
- Page 8 12. Add tantalum capacitor C10. Electrolytic capacitors are polarized and must be installed the right way around! Be absolutely sure to observe the correct polarity when installing these parts. The positive lead is marked with a colored stripe. The positive pad on the circuit board is marked with a small "+"...
- Page 9 14. Attach trim potentiometer R8. 15. Install relays RLY1 and RLY2.
- Page 10 16. Carefully mount the toggle switches SW1 and SW201. Be sure they're seated flat on the board before soldering the leads. You may find it easier to solder the first lead of each switch while the board is component side up.
- Page 11 17. Add J2, the MOLEX power connector. Be sure to orient it as shown, with the locking tab away from the edge of the board. 18. Attach panel control potentiometers R1 and R4. Make sure the controls are seated as flat to the board as possible before soldering the leads.
- Page 12 20. Using the hardware supplied, attach heat sinks to U5 and U6 and solder them in place. Make sure to install the regulators correctly! These parts are not the same and are not interchangeable. 21. Install the bulk filter capacitors C17 and C21. Push them in firmly until they are fully seated against the board.
- Page 13 22. Check your work carefully up to this point. Don’t install the other ICs yet. Initial Power-Up and Testing. 23. Again, carefully check your work for solder bridges and open or poor joints. Make sure you've got the right resistors in the right locations. Make absolutely sure you've got all the polarized parts soldered in the right way around! Double check to make sure you haven’t inadvertently swapped the voltage regulators.
- Page 14 As+-18V As++18V 26. With the negative probe still at PGND, measure the voltage the –18V pin 4 shown above. You should measure very close to -18V. 27. Set your DMM to measure DC voltages of 50V or greater. Center toggle switch SW1. With the negative probe of your DMM connected to PGND, you should measure about +47V at the anodes of D17 and D18.
- Page 15 33. Center SW1, the top toggle switch, and throw SW201, the bottom toggle switch, to the right. 34. Connect the power and apply a 1 kHz signal to the input of the B16. Adjust the signal generator output level to -10dBu. Connect the B16 output to a level meter.
- Page 16 36. Center the Makeup Gain (bottom, inner) control. Throw SW1 to the right (bypass) and observe the change in level on your meter. Adjust the gain trim pot R8 so that the output level does not change between the center and right switch positions on SW1.
- Page 17 Keep in mind that sockets may cause reliability issues in the very long term. IC Sockets are optional and not included with the kit. The B16 can be ordered with an optional output transformer. If you’re installing a transformer, remove (or do not install) the 0R jumpers at R38 and R39. Be sure to install spacers between the board and the transformer.
- Page 18 In Use Compression Ratio – Adjustable from 1:1 (no compression) to infinite (hard limiting.) The ratio increases as the knob is turned clockwise, so maximum compression occurs with the control fully clockwise. Threshold – Controls level where compression starts. Signals below the threshold level are not affected.
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