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PHONE PATCH
MIXER KIT
Ramsey Electronics Model No. PPM3
Ever wish you could broadcast on-the-air telephone calls like
the commercial radio stations? Well now you can! The PPM3
gives you the ability to broadcast both sides of a phone
conversation without having to change any connections to
return to your music or other programming. Perfect for the
budding talk radio star in your house!
• Operates on 8 to 12 volts DC
• Automatic noise gating
• Automatic variable gain and compression
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Ramsey Publication No. MPPM3 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR PHONE PATCH MIXER KIT TABLE OF CONTENTS Introduction ...........................................4 Theory of Operation ..............................5 Learn As You Build ...............................8 Parts Placement Diagram ...................11 Parts List .............................................12 Schematic Diagram .............................14 Assembly Steps ...............................
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PPM3 INTRODUCTION We’ve all heard those awesome call-in programs on the radio. You know, the ones where the host lets the average Joe give his opinion on-the-air to all of his listeners . . . regardless of intelligence level or speaking skills! Yes, we’ve all been embarrassed for poor old Joe when he puts his foot in his mouth and we’ve all thought that we could be much more brilliant and interesting than the high paid host we’re listening to. Well, here’s your opportunity to try your h
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PPM3 CIRCUIT DESCRIPTION The PPM3 is essentially a stereo audio mixer, with one stereo line input and two specialized mono inputs, each feeding into the stereo line output. The phone and mic inputs each have a pre-amp stage that acts as a complete sig- nal conditioner. The mixing core is done with two op amps, U2:C for the left channel and U2:D for the right channel. The line inputs are AC coupled and volume adjusted by R2 and then fed into the mixer. The maximum voltage gain from
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The microphone pushbutton switch (S3) is used to turn on the mic channel by pushing it in, and to mute the mic channel by leaving it out. The mic LED is powered on when the mic is on by using the other half of the switch. The phone line input is meant to monitor both ends of a phone conversation. An external local phone connected to the output phone jack is needed to per- form dialing and to take the phone line “off hook” in order to answer a call. The phone input can be disconnected
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the far-end phone. So the solution is to use a high amount of compression in order to amplify the far-end, weaker signal much more than the local stronger signal. In this way both sides of the conversation are closer to each other in signal strength when applied to the main mixer. A 100K ohm resistor was used to set the compression level around 7:1. The same chart that was used for the mic circuit can also be used with the phone circuit if a different com- pression ratio is desired. Th
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RAMSEY “LEARN-AS-YOU-BUILD” ASSEMBLY STRATEGY Be sure to read through all of the steps, and check the boxes as you go to be sure you didn't miss any important steps. Although you may be in a hurry to see results, before you switch on the power check all wiring and capacitors for proper orientation. Also check the board for any possible solder shorts, and/or cold solder joints. All of these mistakes could have detrimental effects to your kit - not to mention your ego! Kit building tip
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Although we know that you are anxious to complete the assembly of your phone patch mixer kit it is best to follow the step-by-step instructions in this manual. Try to avoid the urge to jump ahead installing components. Remember that all of the components will be mounted on the component side of the circuit board and soldered on the solder side of the circuit board (the side that contains the printed circuit traces). Have a look at the parts layout diagram to help with your assembly. Use
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Once this is accomplished, the part can be installed by holding it with tweezers in contact with the “tinned” trace and re-heating the solder (see the associated diagrams). Another commonly used technique is to glue the surface mount components to the printed circuit board before soldering. The procedure is to take a small amount of glue (usually with a pin or toothpick) and “dab” the circuit board in the place where the component will be affixed. Be careful not to apply too much glue as w
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PPM3 PARTS PLACEMENT DIAGRAM PPM3 Page 11
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PARTS SUPPLIED WITH YOUR PPM3 KIT Capacitors 1 2.2nF ceramic disc capacitor [marked 222] (C16) 1 5.6nF ceramic disc capacitor [marked 562] (C33) 3 10nF ceramic disc capacitors [marked 103] (C11,C13,C23) 2 High voltage 10nF capacitors [large red capacitors marked .01M] (C3, C4) 1 47nF ceramic disc capacitor [marked 473] (C31) 4 0.1uF ceramic disc capacitors [marked 104] (C8,C9,C22,C24) 1 High voltage 0.1uF ceramic disc capacitor [very large orange cap
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2 SSM2165-1S surface mount microphone amplifier ICs (U1,U3) Miscellaneous Components 3 DPDT switches (S1,S2,S3) 1 1/4” stereo jack (J7) 1 Dual RJ11 jack (J1) 1 2.1mm power jack (J4) 2 Dual RCA jacks (J2,J3) 1 Isolation transformer [large yellow part with 6 leads] (T1) 1 Piece of heat shrink tubing PPM3 Page 13
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PPM3 SCHEMATIC DIAGRAM PPM3 Page 14
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PPM3 PHONE PATCH MIXER ASSEMBLY Assembly of the PPM3 is easy but still requires some time and patience. We will start with the surface mount parts and get them out of the way. As with any static sensitive parts be careful when installing the IC’s in this kit. Don’t rub your feet across the carpet and then grab the chip out of your kit as it may be damaged. It’s helpful to ground yourself to a metal object before picking up and installing the next three parts. 1. Install U3, the SSM216
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5. In the same way install C20, a 10uF electrolytic capacitor, again checking your polarity before soldering. 6. Install C19 and C18, noting that these are also 10uF electrolytics and the polarity is exactly opposite to the two parts you just installed. Simply follow the silkscreen and layout diagram for proper placement. 7. Install R14, 10k ohms (brown-black-orange). Resistors have no polarity and can be installed in either direction, although your board will look more uniform i
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25. Install R19, 470 ohms (yellow-violet-brown). 26. Install R27, 15k ohms (brown-green-orange). 27. Install C23, 10nF (marked 103). 28. Install C22, 0.1uF capacitor (marked 104). 29. Install R22, the last 15k ohm resistor (brown-green-orange). 30. Install R18, 10k ohms (brown-black-orange). 31. Install R16, 10k ohms (brown-black-orange). 32. Install R7, 4.7k ohms (yellow-violet-red). 33. Install R8, also 4.7k ohms (yellow-violet-red). 34. Install R11, 4.7k ohms (yellow-viole
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We’ll skip T1 for now and come back to it later. 46. Install C31, 47nF (marked 473). 47. Install D2, 1N4148 diode (orange glass body with a black band). Orient the black band with the band marked on the silkscreen and PC board layout. 48. Install D1, the last 1N4148 diode (orange glass body with a black band). Again, make sure you line up the black band on the part with the silkscreen marking for the part. 49. Install C1, 10uF electrolytic. Remember to line up the positive lead corr
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save them for last. Ok, that’s not the reason, it just makes sense to do them after all the big, bulky parts are in. 61. Install C10, the big 1000uF electrolytic capacitor. Ok, one last time, for real, make sure you get the positive lead and the negative lead oriented correctly before soldering. This one make a big band when it explodes. 62. Install J4, the 2.1mm power jack. It should fit snugly in the board but be sure it’s flat before soldering. Make sure you use enough heat on the gr
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72. Install R15, the other 10k audio pot. 73. Install R2, the 10k stereo audio pot. Now the LEDs. As you may know, LEDs have a polarity just like diodes (they are diodes, light emitting ones) and must be installed correctly to work. The diagram below shows the anode (positive) and cathode (negative) pins of an LED. Your PC board is marked with a little diode symbol that looks like a triangle. The longer anode lead goes toward the large flat end of the triangle and the shorter cathode
