PAiA 9745 Three-One Active Mixer Owner's Manual
The Paia 9745 is a three-input, one-output active mixer designed for modular synthesizer systems. It features 1/8" phone jacks (3.5mm mono) with individual level controls for each input, allowing you to mix audio or control signals with up to 5x gain. This high-performance module is designed to be compatible with most modular synthesizer systems.
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Three-One Active Mixer Model 9745 Assembly and Using Manual This second-generation 9700-series processing element for modular sound synthesizers is designed to provide great sound and excellent value. A three-input one-output active mixer, the 9745 features 1/8" jack (tip-sleeve phone, aka 3.5mm mono) connectors with input level controls. Inputs to the module may be audio or control signals, or both. Individual level controls set the mix of each input to the output from none to full amounts and with as much as 5x gain. This high-performance module is designed to be compatible with most modular synthesizer systems with little or no modification. Most active components are already mounted, making assembly a snap. © 2009 PAiA Corporation ASSEMBLING THE 9745 MIXER Before beginning assembly, go through the manual. Look at the drawings. Feel the parts. You're naturally eager to plunge right in, but take a few deep breaths first. Check the parts supplied against the packing list at the back of this manual. In some cases, notes packed with the parts will be used to call your attention to special situations. If parts are missing, please notify PAiA at [email protected] or by phone at (405) 340-6300, fax (405) 3406378. A NOTES page is included at the end of this manual. Notice that each step in the manual is marked with a checkoff box like this: DESIGNATION ( ) R27 DESC. 100ohm MARKING brn-blk-brn-gld Checking off each step as you do it may seem silly and ritualistic, but it greatly decreases the chance of omitting a step and also provides some gratification and reward as each step is completed. Numbered figures are printed in the Illustrations Supplement in the center of this manual. These pages may be removed for easy reference during assembly. THE CIRCUIT BOARD The 9745 Mixer is built on a double-sided circuit board. Note the “top” side of the board has the connector and control placement designators. Surface-mounted components are on the “bottom” of the board. Install parts to the top of the board and solder them on the bottom. TOOLS You'll need a minimum of tools to assemble the kit – a small pair of diagonal wire cutters, pliers, screwdriver, soldering iron, and solder. 2 Modern electronic components are small (in case you hadn't noticed) and values marked on the part are often difficult to see. Another handy tool for your bench will be a good magnifying glass. Also use the magnifier to examine each solder joint as it is made to make sure that is doesn't have any of the problems in the SOLDERING section which follows. SOLDERING Select a soldering iron with a small tip and a power rating of not more than 35 watts. Soldering guns are completely unacceptable for assembling solid-state equipment because the large magnetic field they generate can damage components. Use only a high quality electronic solder. Your kit is compatible with leadfree and/or tin-lead flux-core solders made especially for electronic assembly. Plumbing solder will destroy your kit with its acid core. Jewelry solder (silver solder) will destroy your kit with its high working heat. Neither is for electronics work. A proper solder joint has just enough solder to cover the soldering pad and about 1/16-inch of the lead passing through it. There are two improper connections to be aware of. Using too little solder will sometimes result in a connection which appears to be soldered when actually there is a thin layer of flux insulating the component lead from the solder bead. This situation can be cured by reheating the joint and applying more solder. Too much solder may produce a conducting bridge of excess solder between adjacent pads causing a short-circuit. Continued feeding of solder into a hot joint can result in accumulation on the underside of the board and may cause bridges or impede the action of mechanical components. If you see this, position the board above the iron tip and the excess will flow to the tip. Use care when mounting all components. Never force a component into place. 3 CONTROLS AND CONNECTORS Controls and connectors will be installed on the top side of the board with the placement designators as shown in the illustration to the right. Miniature phone connectors referenced as “stereo phone jacks” in the manual parts list are specified below with the contact/terminal names, Tip, Ring and Sleeve (TRS) and are labeled on the board and schematic as such. The potentiometers have tabs extending from their body for stability. They have a snap-fit to the board. Align the tabs and pins with their holes and press them into place. There is no need to bend the tabs or terminals. To ensure the best alignment with these parts with the front panel, begin by soldering only one of the multiple terminals associated with each of the following parts as it is installed. Then, if a part is tilted or crooked, it is only a matter of reheating the joint as the part is aligned. Top of circuit board Match the tab of the polarized power connector with the corresponding board marking. DESIG. DESC. ( ) ( ) ( ) ( ) ( ) TRS socket TRS socket TRS socket TRS socket 100K ohm potentiometer, audio 100K ohm potentiometer, audio 100K ohm potentiometer, audio header J1 J2 J3 J4 P1 ( ) P2 ( ) P3 ( ) PWR1 MARKING TRS socket “stereo phone jack” Potentiometer Header 4 COMPLETION The front panel is used for mounting the module in a rack system or cabinet. Complete the module assembly by mounting the 9745 PCB sub-assembly to the front panel as follows: Referring to Fig. 1A of the illustration supplement, use the knurled phone jack nuts to secure the sub-assembly to the front panel. Check for clearance of the potentiometer shafts to ensure they rotate freely. Finger-tighten the phone jack nuts and then use the tips of the diagonal cutters to give them another quarter of a turn or so. Complete the soldering of all multi-terminal parts. Take care the solder doesn't run through to the opposite side of the board when soldering the mounting tabs. With practice, it is possible to flow solder to cover the opening; otherwise, just flow a bit to secure the tab to the pad ring. Cut a 3/8" (10mm) long shim sleeve for each pot from the length of polyethylene sleeve provided. Set the shafts fully counter-clockwise, slip the shims over the pot control shafts, put the knob in place with the pointer aligned to about a 7:00 setting, and use a small screwdriver to tighten the set-screw just enough that it grips. POWERING AND TESTING Power to the circuit is via a four-circuit, dual-polarity DC power supply. A power connector cable matches the header for connection with one of the PAiA 977x supplies at 15v or more. Connect the circuit labeled (+) to the positive DC source (V+), the circuit labeled (-) to the negative DC source (V-), the circuit labeled (G) to the power ground (G), and the circuit labeled (SG) to the signal ground (SG). For other supplies without separate signal and power grounds, use two wires to join the two grounds (G and SG) to the one ground (aka GND, 0VDC or common) at the supply. Before applying power, check again, to be sure the wiring for the two DC polarities and that the polarized 4ckt connectors are as intended (see Fig.1B). Use two-circuit, Tip-Sleeve (TS or mono), cords for patching in or out of the Mixer when connecting with external devices. Within a 9700-series system, either single conductor (Tiponly), or TS cords may be used. If this seems confusing, remember that a regular mono cable will always work for most home studios. PAiA equipment allows tip-only connections for professional applications where star grounding is required. 5 Test the module by connecting the output to a mixer or amplifier and speaker or headphones so signals connected to the inputs can be heard. One signal source may be used for testing with an input connection made and the control associated with the input channel adjusted for a variation in the volume of sound that is heard. Note there is some boost of the input signal as the control is advanced fully clockwise. Check each input this way. With three inputs connected, you should observe that the combination of the three input signals is balanced according to the settings of the level controls. Adjusting one should not affect the other. In1 according to Level1 setting In2 according to Level2 setting In3 according to Level3 setting Mix of In1 In2 and 1N3 6 Signals pass through the mixer direct-coupled, or without capacitors in the signal path. Capacitors can distort a waveform so it is an improvement having the direct connection, but also, this means Control Voltages can be used too. A CV can be combined with another CV such as a LFO or Envelope modulator and their resulting combination will appear with the amounts as set by the Input level controls at the final Output. Inverted, 0V to (-)10V Envelope 10V CV 10V to 0V Envelope 7 Notes DNI marking is Do Not Install note to manufacturer. These are designations where optional 100pF capacitors may be installed for suppression of upper frequency range. Mounting holes are provided on the board for custom applications. 8 Builder's Notes 9 DESIGN ANALYSIS The 3-into1 active mixer consists of three inverting input attenuators followed by an output invert with gain. Taking the first input section as typical, it can be seen that inputting a 10V P-P signal will give a maximum output of 2.2V P-P. The output of this inverter is fed into a potentiometer that is used to further attenuate signals as necessary. All three inverting input sections are then fed into an inverting mixer with a gain of 22. Anywhere from 0 to 20 dB of gain is available from any of the mixer inputs. 10 9745 Parts List Please check the parts against this list. As you locate a part type and verify the quantity (and mounting hardware -- if required) check it off in the space provided. Because we have introduced surface-mount parts with these kits, we are providing the printed circuit card as a subassembly with the surface-mount parts already in place. Also, we want to make you aware that we are using both linear- and audio-taper potentiometers in some of the modules. They are marked differently so we are asking that you check carefully. If anything is missing please notify PAiA at [email protected] or by phone at (405) 3406300, fax (405) 340-6378. Quan Description ( ) 1 9745 PCB Sub-assembly, Active Mixer ( ) 1 9745 Front Panel, Active Mixer ( ) 3 100K ohm Potentiometer, 9 mm Snap-In, Audio ( ) 4 Phone Jack, Stereo, 3.5mm ( ) 3 Knob, Set Screw ( ) 1 Shim, Knob, Polyethylene Sleeve ( ) 1 Header, Vertical, 1row, 4pin ( ) 1 Cable Assembly, Power, 4-wire Test Point Data TP 1 +12 VDC TP2 -12 VDC TP3 0 VDC Power Requirements +15 VDC 10.8 mA -15 VDC 13.4 mA 11 Ref Des P1, P2, P3 J1, J2, J3, J4 PWR1 9745 Active Mixer www.paia.com ">

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Key features
- 3 inputs, 1 output
- 1/8" phone jacks
- Individual level controls
- Up to 5x gain
- Direct-coupled signal path
Frequently asked questions
The 9745 uses 1/8" phone jacks (3.5mm mono) for its inputs and output.
Yes, the 9745 is direct-coupled, meaning it has no capacitors in the signal path. This allows you to use control voltages (CVs) as inputs.
The 9745 can provide up to 5x gain for each input.