SUPER STEREO HEADPHONE AMPLIFIER KIT Ramsey Electronics Model No. SHA2 Want to listen to your audio source with headphones but the manufacturer provided no headphone output? No problem; simply connect the line level output to the input on the SHA2, connect your stereo headphones, and you’re all set! This is the next generation headphone amp with the ability to connect multiple outputs and with more control options than our SHA1.
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Ramsey Publication No. SHA2: Manual Price Only $5.00 INSTRUCTION MANUAL FOR SUPER STEREO HEADPHONE AMP TABLE OF CONTENTS Circuit Description................................ 4 “Learn as you Build”............................. 8 Parts List.............................................. 9 Parts Layout Diagram ........................ 10 Assembly Steps ................................. 11 Schematic .......................................... 12 Setup and Testing..............................
CIRCUIT DESCRIPTION Let’s take a look at the schematic diagram, we will follow through from input to output to get a general idea how this kit works, and why. We will look mainly at the left channel circuitry starting at J1. Items in parentheses , ‘(xx)’, refer to the right channel signal path. Standard configuration settings will be assumed. See the optional configurations section for additional operation information. The nitty-gritty of it all A line level audio signal is connected to J1.
C12(C24) is another coupling capacitor, and it serves the same purpose as C9 at the start of the circuit. This prevents the DC portion of the signal on the output of U2(U4) from being sent to the headphones. The clipping detector circuit The clipping detector circuit watches the headphone output signal level and flashes an LED when the output signal comes close to the maximum level available from the LM386. This level is determined by the voltage divider formed by R15 and R17.
impedance makes it possible to connect multiple devices, like the SHA2, with high impedance to the output without having any significant effect on the quality of the signal. This is called bridging the output. Wondering what impedance is? If you know about resistance you know, or I’ll tell you, resistance is a measurement, in ohms, of the amount of resistance to current flow in a DC circuit. Like a garden hose that is crimped.
The power supply VR1, C29 and C28 supply the regulated DC voltage for the circuit. VR1 regulates the input, which should be around 12VDC input to J5, to a level of 10VDC for use in the unit. Yes the internal supply voltage indicates it is 9VDC and here is the reason why. You will notice that diode D1 is connected between VR1 and the power switch. This diode is to prevent voltage being applied to the output of VR1 from battery BAT1.
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.
SHA2 PARTS LIST CAPACITORS 5 10 nF ceramic disc capacitors [marked 103] (C3,13,15,21,25) 2 100nF ceramic disc capacitors [marked 104] (C14,27) 2 100pF ceramic disc capacitors (marked 100, 101, or 101K ) (C11,23) 4 220nF ceramic disc capacitors (marked ) (C6,7,8,26) 2 390nF ceramic disc capacitors(C19,20) 14 10uF electrolytic (C1,2,4,9,10,16,17,18,22,28,29,30,31,32) 2 220uF electrolytic (C12, 24) 1 470uF (C33) RESISTORS 2 3 4 1 1 4 2 ohm resistors [red-black-gold] (R7,14) 470 ohm resistors [yellow-violet-br
SHA2 PARTS LAYOUT DIAGRAM SHA2 • 10
ASSEMBLY STEPS You’ve got your parts sorted, your iron is warmed up, so let’s get started. We’ll follow a logical order when installing the parts in your kit. Take your time and be sure to make good, solid solder connections. Save a couple of the longer leads that you snip off the back when trimming. You need one of them for a later step. Install U3, LM1036N dual DC operated tone/volume/balance IC.
SHA2 • 12
SHA2 • 13
lead is not only shorter than the other, it has a band or stripe running down the body of the part next to the short lead that shows zeros or minus signs. Be sure to install the part so that the positive lead goes into the hole marked with a “+” sign and the negative lead into the other. Push the part down until it sits on the board and solder both leads. Install C15, 10nF ceramic disc capacitor (marked 103). Install C6, 220nF ceramic disc capacitor (marked 224).
Install C14, 100nF ceramic disc capacitor (marked 104). Install R7, a 2 ohm resistor (red-black-gold). Install C23, 100pF ceramic disc capacitor (marked 100, 100K, or 101). It’s tucked in between U2 and U4. Install C27, 100nF ceramic disc capacitor (marked 104). Install R14, 2 ohms (red-black-gold). Install C12 and C24, both 220uF electrolytic capacitors. These are slightly larger than the 10uF caps you’ve been installing but the same rules apply as to polarity.
Install R4, another 1 M ohm resistor (brown-black-green). Install C28, 10uF electrolytic capacitor. Remember the polarity yet again. Install C29, 10uF electrolytic capacitor. Placement. Install C9, 10uF electrolytic capacitor. Watch your placement.. Install C2, yup, another pesky 10uF electrolytic. The lead with the band goes in the hole opposite the one marked with the “+” sign, as usual. Install R1 and R2, both 1 M ohm resistors (brown-black-green). Install H2, one of the three pin headers.
stories about DPDT switches to bore you with. Back to jacks, install J2 and while you’re at it, let’s install J1 and get it over with. Both are 3.5mm stereo jacks. Now install J5, the 2.1mm power jack. Time to install the 9V battery holder. This is where you’ll need that clipped off lead from the beginning of your construction. This is bent into the shape of a staple that will fit through the holes in the battery holder and down through the top of the circuit board.
The battery snap is the last part to be installed. The red lead goes into the hole marked with a “+” sign and the black goes into the “-” hole. You can tin the leads by twisting them together and melting some solder on them or you can simply twist them, put them through the board, and solder them. It’s up to you. Just don’t tin them so much that they don’t fit through the holes in the board. That’s it! But wait, before you grab a battery and fire up your kit let’s check a few things.
SETUP AND TESTING It’s time to apply power to your SHA2 and start listening to your line level sources. You need: • • • • 1. 2. 3. 4. 5. 6. 7. 8. 9. An AC adapter or a fresh 9 volt battery A line level audio source (CD player line out, etc.) A cable to connect the audio source to the SHA2. Either dual RCA to 3.5mm stereo or 3.5mm stereo to 3.5mm stereo, depending on what connector(s) are on your line level source. Headphones Connect your audio source to J1, the line level audio input jack.
You can set the left and right channels independently of each other. H1 controls the right channel of the stereo output and H2 controls the left channel. Pin 1 on both H1 and H2 is marked by a triangle. By placing a jumper block between pins 1 and 2 of H1 and H2, the buffered output follows the input exactly. Whatever you have coming in on the audio input is what will be sent out on J2.
TROUBLESHOOTING While we hoped it wouldn’t come to this, it’s possible that your SHA2 didn’t work as soon as you applied power. The main thing to remember in a situation like this is . . . don’t panic! It’s usually something simple and since you built the kit, you know the kit and you’ll find it if you look carefully. Just follow a logical approach when troubleshooting. The first thing to check is always your component placement, especially ICs, diodes, and electrolytic capacitors.
If you enjoyed this Ramsey product, there are plenty more to choose from in our catalog - write or call today! CONCLUSION We sincerely hope that you will enjoy the use of this Ramsey product. As always, we have tried to compose our manual in the easiest, most “user friendly” format possible. As our customers, we value your opinions, comments, and additions that you would like to see in future publications. Please submit comments or ideas to: Ramsey Electronics Inc. Attn.
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.
TABLE OF CONTENTS Circuit Description................................4 “Learn as you Build”.............................8 Parts List ..............................................9 Parts Layout Diagram ........................10 Assembly Steps .................................11 Schematic ..........................................12 Setup and Testing..............................19 Troubleshooting .................................21 Warranty ............................................
