Hifi Preamps for your Record Player

Build the Muffsy Phono Preamp PP-3

The Muffsy Phono Preamp kit comes with all on-board components. Have a look at this page to learn about how to turn it into a complete and fully working phono stage.


You can also have a look at the schematics for the Muffsy products under the Modify It page.

Illustrations Explained

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.

PCB Overlay

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.

Actual PCB with Comments

Step 1: Check the Kit Contents

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:

 Quantity Component
1 Muffsy PP-3 Printed Circuit Board 
 2 Resistors 0.25W,  100 ohm
 2Resistors 0.25W, 130  ohm
 2Resistors 0.25W, 180 ohm 
 4Resistors 0.25W, 300 ohm 
 0Resistors 0.25W, 430 ohm  (replaced with 300 ohm)
 4Resistors 0.25W, 2k2 ohm 
 4Resistors 0.25W, 3k3 ohm 
 2Resistors 0.25W, 16k ohm 
 2
Resistors 0.25W, 33k ohm 
 2Resistors 0.25W, 82k ohm 
 2Resistors 0.25W, 110k ohm 
 2Resistors 0.25W, 150k ohm 
 28-Pin DIL Sockets 
 22-Way DIP Switches 
 24-Way DIP Switches 
 2Operational Amplifiers 
 4Ceramic Capacitors, 100 nF 
 2Polyester Film Capacitors, 47 nF 
 4Polyester Film Capacitors, 68 nF 
 2Polyester Film Capacitors, 1 uF 
 4Electrolytic Capacitors, 22 uF 
2 DG301 Screw Terminals, Two Positions 
2 DG301 Screw Terminals, Three Positions 

All resistors are 1/4 W, metal film, 1% tolerance.

Note:

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.

Step 2: Solder the Resistors

There is a total of 28 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.


Before you mount the resistors, have a look at the possible modifications you can make and replace the necessary resistors accordingly.


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.

All resistors
Resistors mounted on the board

Step 3: Solder the DIL Sockets

These are the sockets for the operational amplifiers. 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 two 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.


Using a piece of masking tape to hold the sockets in place might be a good idea.

8-Pin Dual In-Line Sockets Position
DIL Sockets, notice the orientation

Step 4: Solder the DIP-Switches

These four DIP-switches are here to adjust the input impedance and overall gain of the phono stage.


It is absolutely essential that you get the orientation right. If you don't, adjusting the features of the preamp will be very difficult and confusing.


Use a piece of masking tape to hold the switches in place while you solder.


Now is a good time to set the default settings of the phono stage. Set switch 2 and 3 on the input impedance switches to on, and switch 1 on the gain switches to on. The input impedance will now be 47k ohm and the gain will be 40 dB

Position of the DIP-Switches
Pay attention to the orientation of the switches!

Step 5: Solder the Ceramic Capacitors

There are four ceramic capacitors, two on each side of each DIL socket.


These capacitors can be oriented which way you like. I like to mount them so I can see the text on them.

Position of the ceramic capacitors
Ceramic capacitors mounted on the board

Step 6: Solder the RIAA Polyester Film Capacitors

These are the six capacitors in the RIAA filter. 

They are bipolar, so orientation is not significant. I still like to place them so that the text is visible.

Placement of RIAA capacitors
Board in progress - RIAA capacitors

Step 7: Solder the Output Capacitors

These two 1 uF polyester film capacitors makes sure that no direct current (DC) enters into the next amplification stage (preamp or power amplifier).


They can be oriented either way. Note that the PCB has space for two different sizes, 5 and 10 mm lead spacing. One of the legs must be towards the center of the board, and the capacitors must span the "-||-" symbol. The pictures below explains this.

Placement of the output capacitors
Output capacitors mounted on the PCB

Step 8: Solder the Electrolytic Capacitors and Mount the Operational Amplifiers

The four 22 uF electrolytic capacitors must be oriented correctly, or there's a chance they will go up in smoke.  


The board shows a plus (+) symbol, this is where the longer leg of the capacitors will go. The capacitors have a white band with several minus signs (-), this side also has the longer leg. This side goes downward when the board is oriented as shown on the pictures.


Now is also the time to mount the two operational amplifiers into their sockets. They are small eight-legged chips, and the dot and/or notch matches the notch in the sockets. Make sure they go in the right way, and that no legs are bent so that they miss the hole.

Electrolytic capacitors and operational amplifiers
Electrolytic capacitors and operational amplifiers mounted on the PCB

Step 9: Optional - Solder the Input Capacitors

For some very special setups/cartridges, you may need some additional input capacitance. If you do, mount these two capacitors now.


It is very likely that you won't need them, and they are not included in the kit. 

Input capacitors placement
Input capacitors on the PCB

Step 10: Solder the Screw Terminals

These screw terminals will make it easier to connect the power and audio cables.


Orientation of the Screw Terminals

B0905 Cabinet: If you are using a B0905 cabinet, you really want the holes of the screw terminals pointing inwards. If you don't, you risk shorting the cables against the wall of the cabinet.


If you have a lot of space in your cabinet, having the holes of the screw terminals pointing outwards from the board is normally the way to go.


Screw terminals, with descriptions

Construction Complete