This kit is for sale on Tindie:
This is how you connect your Muffsy MC Head Amp when you're done building it:
Ready? Here we go!
The picture below is a larger version of your printed circuit board. For each step, this will be used to show you which components you will be adding to the board.
This picture shows you where you are in the build process. It also shows what each component looks like, and it will contain special instructions or information.
Before you start building, check that you have all components and familiarize yourself with the kit. Here's a list of the kit's contents:
|1||Muffsy MC Head Amp, Printed Circuit Board|
|2||Resistors 0.25W, 47 ohm|
|2||Resistors 0.25W, 100 ohm|
|2||Resistors 0.25W, 150 ohm|
|4||Resistors 0.25W, 220 ohm|
|2||Resistors 0.25W, 300 ohm|
| 2|| Resistors 0.25W, 750 ohm|
| 2|| Resistors 0.25W, 100k ohm|
| 4|| Resistors 0.25W, 1M ohm|
| 2|| Film capacitors, 330 pF|
| 8|| Ceramic capacitors, 0.1 uF|
| 4|| Film capacitors, 1 uF|
| 2|| Operational amplifiers, LT1115|
| 2|| Operational amplifiers, OP177|
|2|| Electrolytic capacitors, 100 uF|
| 1||Four-way DIP-switch|
|4||8-pin DIL sockets|
| 1||Screw terminal, 3 positions|
|1||Sticker with alternative impedance values|
|30 cm / 1 ft||RVVP 2x0.2 shielded audio cable|
This high quality printed circuit board has plated-through holes. Do not attempt to drill the holes to make them larger, doing so will destroy the board. The four mount holes, one in each corner, may be drilled to size.
There is a total of 18 resistors that go onto the printed circuit board. The resistors are bidirectional, meaning that you don't have to worry about which way they are oriented.
All orders after 2016-09-28 are shipped with resistors that will let you choose between these two input impedance schemes. When you're done, you will end up with either 2x 220 ohm or 2x 300 ohm resistors that are left over.
It's recommended that you measure the resistors before you put them in place, and make absolutely sure that the right resistors go in the correct positions.
The picture below shows all the standard resistors soldered in place. The resistors in the kit are Multicomp MF25, 1% tolerance with a temperature coefficient of ±50ppm/°C. They are very fit for the job, and you should not have to worry about replacing them with more audiophile resistors.
These are the sockets for the operational amplifiers, and there are four of them. They will make it easier to replace the small chips later on if you should want to. Soldering the sockets will also make sure you don't overheat the operational amplifiers when installing them.
The orientation is very important for these four sockets, get it wrong and you will be confused about which way to mount the operational amplifiers. There's a notch in the socket that matches up with the picture on the printed circuit board, as shown in the pictures below.
Note that the text beneath the DIL sockets refers to the operational amplifiers that will be mounted later.
Using a piece of masking tape to hold the sockets in place might be a good idea.
This four-way DIP-switch is here to adjust the input impedance of the head amp.
It is absolutely essential that you get the orientation right. If you don't, adjusting the features of the head amp will be very difficult and confusing. The text "ON DIP" goes towards the top of the board and the numbers "1 2 3 4" go towards the bottom, as shown in the photo.
Use a piece of masking tape to hold the switch in place while you solder.
The input impedance can be set between 47 and 100 ohms, or between 50 and 300 ohms (alternative resistors) in four steps, according to the tables below (and the text on the board itself).
The safest choice is to set the impedance to 100 ohms, unless you know exactly which impedance your cartridge needs.
The eight ceramic capacitors shown in yellow in the picture below are up next.
They don't need to be oriented in any special direction. It's a good idea to mount them with the text outwards though, so that the values are visible.
These are Wima FKP2 polypropylene capacitors. There's two of them, one for each channel. Mount them as shown on the pictures below, orientation does not matter.
These four larger capacitors are Wima MKS2 polyester models. There's four of these capacitors. Orientation does not matter, although it looks nicer if they're all mounted the same way. These pictures show where the capacitors go.
The kit contains one screw terminal with three inputs that connects to the power supply. There is space for screw terminals on the signal input and output, but these really should be soldered directly to the board in order to avoid introducing noise into the circuit.
Solder the screw terminal as shown in the pictures below.
These two electrolytic capacitors form the power supply decoupling together with the ceramic capacitors in step 5.
Please make sure that they are mounted correctly, or they can go "poof". The longer leg goes in the hole marked '+', the shorter leg (which has the white strip with the '-' symbols) is oriented to the left, when the board is seen as it is below. The second picture shows how it should look when you're done.
Follow the build instructions for the Muffsy Power Supply v4.
PLEASE NOTE: Make sure that you don't exceed the maximum voltage of your operational amplifiers. The Muffsy Power Supply delivers +/- 15 volts, which is fine for the op amps delivered with the kit. Others, like certain discrete operational amplifiers, max out at +/-12 volts. (Have a look here if you need to change the Muffsy Power Supply's voltage.)
These are all the parts you'll need for the back panel, all of them are included in the back panel kit:
Take the four RCA connectors and put the plastic shims on them. The plastic shims on the front can be left out, but you will find that the connectors are easier to tighten with the shims though.
Mount the two RED connectors in the top holes, and the two BLACK connectors in the bottom holes:
Insert the ground pads on the top two connectors and fasten them with a nut. Fasten the bottom connectors with nuts only.
It's a good idea to use a couple of wrenches to make sure the RCA connectors are tightly fastened. If they are loosened and twisted around, you could snap or short the signal cables connected on the back of the connectors.
These connectors are electrically connected together inside the back panel, do not use the plastic shims on the back. If you do add these shims, you will get humming and poor sound quality.
Mount the ground screw and fasten it with a nut. Add the shim and the knurled thumb nut:
Mount the power connector. The hole is not centered, make sure it is towards the top of the board. Fasten the power connector with the nut that comes with it:
Click the power button in place. Make sure the "1" is on top:
Your back panel is now done. Here's how the backside looks when it's finished:
The information below is for the Muffsy MC Head Amp, Muffsy Power Supply and Muffsy Back Panel mounted in a B0905 cabinet.
You may want to do this in an entirely different way if you don't have all these components, if you want to incorporate the Muffsy Phono Preamp, or if you want to use a different enclosure.
Cut two pieces of the shielded audio cable, approx 7 cm long. Strip the wires as described below:
When you're done, the cables will look like this:
Twist the shielding (the exposed outer wire) and strip about 0.5 cm from each of the red and white wires. Twist the ends tightly.
Solder the 1.5 cm ends into the inputs/outputs on the Muffsy MC Head Amp board. Soldering, instead of using screw terminals, will make a better signal connection. This is very important when dealing with sub-microvolt signal levels.
Cut one piece of black wire to about 2 - 2.5 cm, two pieces of red and blue wire, and strip about 0.5 cm on each end. Tin both ends of each cable:
Connect the tinned end of these three wires to the power output screw terminal on the Muffsy Power Supply.
Stick the other end of these three power cables into the MC Head Amp Board, crossing over the red and blue ones, and fasten the screws.
Cut a red and a black piece of wire to size, approx. 4 cm (these may need to be shorter or longer, place your cables over the boards and cut to the length that suits your assembly), and connect the two boards as shown below. It does not matter which color goes where.
Cut a piece of red wire, ~3 cm, and strip 0.5 cm from each end.
Solder this wire between the bottom of the back panel's power button and the L-shaped terminal on the power connector.
PLEASE NOTE: Take care not to apply too much heat to the connectors on the power button. The plastic could melt otherwise. (I've used 330 degrees C / 625 degrees F).
Cut two cables. Red = 5 cm and Black = 6 cm.
Strip ~0.5 cm from both ends of both cables, solder the shorter red cable to the bottom terminal on the power connector (the next one, clockwise from the L-shaped terminal).
Solder the black cable to the upper terminal of the power button, making sure not to overheat it. (Again, I've used 330 degrees C / 625 degrees F).
Solder the input and output signal cables to the back panel.
GND Terminal: Shield
Top RCA: Red
Bottom RCA: White
Solder all of them, aligned with the back panel as shown below:
Solder the red and black power cables from the Muffsy Back Panel to the Muffsy MC Head Amp. It doesn't really matter which cable goes where, it does look nicer if it matches the cables from the Muffsy MC Head Amp to the Muffsy Power Supply though.
Finally, dab some solder on the corner pad on the Muffsy Back Panel. This will help ground and shield the entire head amp later on.
Use just a small amount of solder and smear it around the pad.
Mounting the Muffsy MC Head Amp in the B0905 cabinet couldn't be easier. Just slide the boards into the grooves of the cabinet, starting with the Muffsy Power Supply.
Screw the back panel in place, using the provided screws.
Test fit the upper part of the enclosure to see which way it fits. File or sand away the paint from the upper left corner.
This is where the tinned ground pad on the Muffsy Back Panel connects to the enclosure.
Testing the Muffsy MC Head Amp before using it is essential. If these tests are not successful, it's very likely that you will damage the operational amplifiers.
You will need a multimeter capable of measuring both AC and DC volts for these tests.
The OP177 operational amplifiers are there to make sure that there is no DC offset on the signal. If there is only one of the voltages present, +15 volts or -15 volts, they will work very hard to correct this, frying your LT1115 operational amplifiers in the process.
If you're using batteries, this can happen if only one of them runs out of power. This is why you're discouraged from using batteries to power your Muffsy MC Head Amp, and why you need to be 100% sure that the voltages are correct.
Before you go ahead, you should visually inspect the circuit boards.
If you have installed the operational amplifiers in their sockets, please remove them. The purpose of this test is to make sure that they're not being damaged.
This is your very first test. Turn the power button ON, and touch the components on the Power Supply to check that they don't get hot.
If any of the components get hot to the touch, there's something wrong with your power supply or cabling. Remove the power adapter immediately and check the power supply board for errors.
If the components stay cool, move on to the next step.
These are the errors you can get:
Make sure you have an AC power adapter:
Check that the power supply is getting power:
If your turntable has a built-in phono stage, make sure it's turned off.
The output from the Muffsy MC Head Amp needs to be connected to a phono stage for MM cartridges. That could be the Muffsy Phono Preamp, or your existing phono stage.
If you have gone through all the tests and the troubleshooting, and your Muffsy MC Head Amp still isn't working, please contact me so we can find and fix the problem together.
Before you mount the operational amplifiers, disconnect the AC adapter and turn the power switch to OFF. If you don't, the op amps may be damaged.
There are four operational amplifiers in the kit. Two marked LT1115 and two marked OP177. The LT1115s do the amplification and the OP177 make sure that you don't have any DC in your signal.
Mount the operational amplifiers in their sockets, as shown in the picture below. The sockets and operational amplifiers have a notch that correspond. Insert the op amps carefully into their sockets without bending any of the legs, and check that the orientation of each chip is correct. Mounting them wrong will most likely damage them.
Connect the AC adapter and turn on the power, while touching the LT1115 operational amplifiers.
If the LT1115 op amps get really hot, disconnect the power immediately, and go through all the tests again. The LT1115 operational amplifiers will get a little bit warm when the head amp is powered on, but they should not be burning hot.
Here's a few parting words before you enjoy your new Muffsy MC Head Amp: