Ramsey Electronics Model No. MX-5 Now here’s the simple easy to use mixer for all of you home brew DJs out there! This mixer has two line inputs and one microphone so that you can hook up all of your audio sources to any transmitter or audio amplifier. Perfect for mixing those car tapes before the big trip! • 2 Line inputs and one mic input, all most people will ever need! • Overload protection on the microphone input to “soften” distortion • Requires regulated 9 to 15VDC supply or battery.
RAMSEY TRANSMITTER KITS • FM-10a,25 FM Stereo Transmitters • FM-1,2,4,5,6 FM Wireless Microphones • PB-1 Telephone Transmitter RAMSEY RECEIVER KITS • FR-1 FM Broadcast Receiver • AR-1 Aircraft Band Receiver • SR-1 Short-wave Receiver • AA-7 Active Antenna • SC-1 Short-wave Converter RAMSEY HOBBY KITS • ASA-602 2x60 Watt RMS Car Amp • ASA-604 4x60 Watt RMS Car Amp • SF-2 Super Crossover Filter • SP-1 Speakerphone • MX-5,10 Stereo Mixers • PH-14,15,16 Peak hold Meters, great for VU meters! • LC-1 Inductance-C
Ramsey Publication No. MMX-5 Price $5.00 KIT ASSEMBLY AND INSTRUCTION MANUAL FOR MX-5 STEREO THREE INPUT MIXER TABLE OF CONTENTS Introduction .................................... 4 How Does It Work? ........................ 5 Learn As You Build ........................ 7 Parts List ........................................ 9 Construction ................................. 10 Schematic Diagram...................... 12 Setup And Testing ....................... 16 Troubleshooting ...........................
INTRODUCTION TO THE MX-5 Upon designing a more complex version of this kit, the MX-10, we determined that not everyone needed all of the features in the world, so we came up with this simple design. This is a high quality low-noise mixer capable of handling two stereo line inputs and one mono microphone input. This gives most users all the inputs that they will ever need for making car tapes, DJing for a wedding, using with our stereo transmitter kits etc.
MX-5 CIRCUIT DESCRIPTION We will use the schematic diagram to step through the circuit and find out what makes it “tick”. As you can see, there is only one IC in the entire circuit, but there are four individual operational amplifiers in the one IC. U1:A and U1:B are the main components of the mixer. They are set up in what is called a summing amplifier. If we were to look at the left channel only, we can see what one of the summing amplifiers looks like.
becomes greater than .7V P/P, then the diodes D1 and D2 begin to turn on. This brings R14 into the gain equation as well. Now you have an Rf = R14 in parallel with R16. This brings the overall gain down to less than .1, now the amplifier is working as an attenuator. The best part of the diodes is that they don’t just “snap” on, they have some variance before they are on fully, so this creates what is called “soft clipping”. This soft clipping is a close relative of distortion, but much more tolerable.
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.
As with all Ramsey kits, we want to mount the parts AS LOW AS POSSIBLE to the board. A 1/4” lead length on a resistor not mounted close to the board can act as an inductor or an antenna, causing all sorts of problems in your circuit. Be aware though that if there are stand up components in your circuit, they don’t need to be squished to the board. Keep the portion of the resistor closest to the board mounted right on the board. For each part, our word "Install" always means these steps: ❒ ❒ 1.
RAMSEY MX-5 PARTS LIST Semiconductors ❒ ❒ ❒ 1 LF347 Dual operational amplifier (U1) 2 1N4148 type switching diode (D1,2) 1 1N4002 type diode (D3) Resistors ❒ ❒ ❒ ❒ ❒ ❒ ❒ 10 10K ohm resistors (brown-black-orange) (R1,2,9,10,11,12,15,16,17,18) 1 22K ohm resistor (red-red-orange) (R21). 2 33K ohm resistors (R4,7) 1 220K ohm resistor (red-red-yellow) (R23). 5 1K ohm resistors (brown-black-red) (R14,22,24,25,26). 2 1M ohm resistors (brown-black-green)(R19,28). 1 47K ohm resistor (yellow-violet-orange)(R27).
ASSEMBLY OF THE MX-5 Now we are getting to the good stuff-assembling the MX-5. We will begin by mounting first the low parts, beginning with the parts on the side of the board without the traces. When we are finished with that side, we will begin to install parts on the trace side of the board. This side is where all of the controls go, and will be the side of the board facing the top of the case. 1. Install R1, a 10K ohm resistor (brown-black-orange). 2.
20. Now it is time to install U1, the LF347 quad opamp. Notice how on one end of the IC there is a notch, dimple or dot indicating pin one of the IC. You will need to align it with the notch as shown in the parts layout diagram. Make sure all 14 pins are through the board before soldering, and that none are bent under the IC. 21. Install R19, a 1M ohm resistor (watch out! 1,000,000 ohms!) (brownblack-green). 22. Install R28, a 1M ohm resistor (brown-black-green). 23.
31. Install C6, a 10uF electrolytic capacitor. (Polarity!) 32. Install C7, a 10uF electrolytic capacitor. 33. Install C3, even another 10uF electrolytic capacitor. (Need we remind us about polarity) 34. Install C5, another 10uF electrolytic capacitor. 35. Install C8, just to throw you off, it’s a .1uF ceramic capacitor. This is the only capacitor where orientation does not matter. 36. Install C10, a 10uF electrolytic capacitor. (Orientation!) 37. Install C12, even another 10uF electrolytic.
47. Install J3, another RCA jack. 48. Install J5, the last of the RCA jacks. 49. Install J7, the 2.1mm power jack. 50. Install S1, the DPDT switch. Make sure the part is flush to the board before soldering. 51. Install the battery power clip. Make sure the red wire is installed in the hole marked (+), and the black wire is installed in the hole marked (-). 52. Using a piece of scrap component lead, mount the battery holder to the PC board under where the battery is to go.
the jumpers to the pins of the slider. 58. Install R13, the 10K ohm LINE2 pot the same as described in step 57. 59. Install R3, the 10K ohm LINE1 slider pot in the same way as shown in step 57. 60. Install R20, a 10K ohm surface mounted pot, the last board mounted part. Make sure to solder all three connections and the two solder lugs. Wow! we are already finished putting together the kit! Lets go celebrate and grab a soda or other drink of choice, get an eyeball break and come back in a few minutes.
TROUBLESHOOTING GUIDE Well, we sincerely hope you get to skip this portion of the manual, but this is here to help in the event of an emergency. Remember the detrimental effects an incorrectly installed component may have on your circuit. Keep this in mind as you troubleshoot your circuit for possible assembly errors. PROBLEM: Nothing at all on the output of the mixer. SOLUTION: Check your power supply voltages to make sure you have at least 8 volts over all.
PARTS SIDE VALUES MX-5 Page 16
PARTS LAYOUT DIAGRAM MX-5 Page 17
CONTROL SIDE LAYOUT MX-5 Page 18
USING THE MX-5 PH-15 POWER STC-1 MID BASS FM-25 HIGH POWER HA-3 LEFT RIGHT POWER Above shows a full installation for radio broadcasting using one of the Ramsey micropower transmitters. The parts and pieces are as follows: MX-5, our newly built mixer PH-15, Peak hold meter for watching audio levels STC-1, Stereo transmitter companion. Compression, limiting, bass, midrange, and treble controls. Active 8th order lowpass to get rid of interfering sounds. FM-25, the PLL stereo transmitter.
We sincerely hope you have enjoyed building this kit. We invite you to check out our catalog and see all of the projects that you can put together. We have one of the most complete line of kits available today, and many more products to come. Give us a buzz, well send you a catalog. Call or write: Ramsey Electronics 793 Canning Pkwy.
The Ramsey Kit Warranty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solved without contacting the factory. Notice that this is not a "fine print" warranty. We want you to understand your rights and ours too! All Ramsey kits will work if assembled properly. The very fact that your kit includes this new manual is your assurance that a team of knowledgeable people have field-tested several "copies" of this kit straight from the Ramsey Inventory.
MX-5 STEREO THREE CHANNEL MIXER KIT Quick Reference Page Guide Introduction.......................................... 4 How Does It Work? .............................. 5 Learn As You Build .............................. 7 Parts List ............................................. 9 Construction ...................................... 10 Schematic Diagram ........................... 12 Setup And Testing ............................. 16 Troubleshooting ................................. 17 Parts Value Diagram...
