Introduction: Muffsy Phono Preamp PP-3

Picture of Muffsy Phono Preamp PP-3

Visit the Muffsy Home Page for more resources.

A Hifi Phono Stage

The Muffsy Phono Preamp PP-3 is a hifi pre-amplifier for vinyl turntables with MM and high output MC cartridges.

With its no-nonsense, straight forward design that focuses on both performance and cost, this project caters to audiophiles and music lovers alike.

For once, there is no magic involved in a true audiophile piece of equipment. You get spectacular RIAA compliance (+/- 0.025 dB, 1-100.000 Hz), ultra-low noise, a wonderful great sound stage and superior detail. All done with one small PCB and standard, off the shelf components.

Specifications

  • THD: 0.00190%
  • THD+N: 0.01013%
  • SNR: 112.83 dB (Shorted inputs, relative to 1 Vrms/0 dBV)
  • Crosstalk: -102.24 dB
  • IMD: 0.0195% (ITU-R, 19+20 kHz)
  • Dynamic Range: >110 dB (THD+N: 1%)
  • RIAA Compliance: +/- 0.025 dB
  • RIAA Equalization: Passive
  • Gain: 36-46 dB in four steps
  • Input Impedance: 17k-150k ohm in fifteen steps
  • Input Capacitance: Optional (space for capacitors on the PCB)
  • PCB Size: 84 x 56 mm

Available as a Kit

The Muffsy Phono Preamp PP-3 comes as a kit, in the Muffsy Store and on Tindie.

Complete and Easy to Build

The Muffsy PP-3 kit contains everything you need to build a fully working phono stage. As long as you've got a soldering iron and a pair of pliers, you will be able to build it. It even comes with soldering wire!

Please note that the kit doesn't include power supply, cables and connectors, and enclosure. Alternatives are included in these instructions, follow them and you will have a complete phono stage.

Extensive Documentation

All the information you could ever want about this phono stage, including schematics and modifications, is available on the Muffsy Home Page.

Step 1: Instructions Overview

Picture of Instructions Overview

Detailed Illustrations

These instructions will guide you all the way from a bag of components to a fully functional phono stage.

Each step has a picture that outlines the components that will be mounted and an annotated picture of the real board in progress.

Contents

  • Steps 2 through 10 show the actual soldering of the components
  • Step 11 shows the back panel
  • Step 12 shows the audio and power supply wiring
  • Step 13 handles the enclosure
  • Step 14 describes the different settings on the board

Before you Begin

  • Soldering the Muffsy Phono Preamp PP-3 will take up to one and a half hour.
  • Make sure you have enough time, and an environment without distractions.
  • Don't stress, just enjoy building.
  • Take the time to read and understand the instructions.Make sure you understand each step. If not, read again or ask a question in the comments section.
  • Notice that many components must be oriented a certain way. Look at the pictures to avoid any confusion.

How to Solder

If you're just starting out soldering, or if you need an update on how to solder,SparkFun has a great tutorial for soldering through-hole components.

If you have never soldered before in your life, I strongly recommend that you look through the two instructional videos above from EEVBlog. (How to solder part 1 - Tools and How to solder part 2 - Through hole components)

A Note on the Printed Circuit Board

The high quality printed circuit board has plated-through holes. Do not attempt to drill these holes to make them bigger. Doing so will break the board.

It is safe to drill the four screw holes (one in each corner) to make them larger.

Step 2: Solder the Resistors

Picture of Solder the Resistors

Before you start soldering the resistors, consider if you want to:

With these decisions made, go ahead and solder all the resistors as shown in the pictures above.

Make sure that the right resistor goes in the right place. Orientation does not matter for the resistors.

Step 3: Solder the DIL Sockets

Picture of Solder the DIL Sockets

The DIL (dual in-line) sockets are the next components to go on the PCB. These sockets are used so that the amplifier chips (operational amplifiers) can be replaced if needed.

Notice that the sockets have a notch in them. This notch needs to match the picture on the circuit board.

When soldering these sockets, a piece of tape can be used to hold them in place.

Step 4: Solder the DIP Switches

Picture of Solder the DIP Switches

The DIP switches go in next.

Note the orientation. If you mount the switches the wrong way around, you will have a hard time configuring the right settings for your preamp.

Now is a good time to set the switches 2 and 3 on the input impedance switches to on, and switch 1 on the gain switches to on (as shown in the picture above). This will be your starting configuration. The input impedance is now 47 kohm and the gain will be 40 dB.

Step 5: Solder the Ceramic Capacitors

Picture of Solder the Ceramic Capacitors

Next, solder the four ceramic bypass capacitors.

Orientation does not matter for these capacitors, I like to have the markings outwards so they can be seen.

Step 6: Solder the RIAA Polyester Film Capacitors

Picture of Solder the RIAA Polyester Film Capacitors

These are the polyester film capacitors for the RIAA filter. There are a total of six capacitors, three for each channel.

Orientation does not matter for these capacitors.

A RIAA equalization filter is what makes this preamp turn the signal from a record into something you can actually listen to. Check out this Wikipedia article to learn more.

There are two main ways of doing RIAA equalization. It can either be active (in the feedback circuit of the amplifier) or passive. While there are good things to be said about both techniques, a passive filter generally has better RIAA compliance, less noise and can't be overdriven. This are good factors for DIY, so the Muffsy PP-3 employs a passive filter.

Step 7: Solder the Output Capacitors

Picture of Solder the Output Capacitors

These are also polyester film capacitors, and they are located on the right side of the PCB.

Make sure that they are mounted over the sign that looks like this: -||-. One of the legs must be in the hole towards the center of the board. Orientation does not matter for these capacitors.

These capacitors are there to filter out any DC components in your signal. Without them, the sound could sound very bad and you could damage your speakers.

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

Picture of Solder the Electrolytic Capacitors and Mount the Operational Amplifiers

These four capacitors (10 or 22 uF, depending on what you chose when ordering the kit) have to be oriented the right way. The white band shows the negative leg, and points downwards for all four capacitors.

Now is also a good time to mount the operational amplifiers into the DIL sockets. Make sure that the notch or mark on the opamp is oriented the same way as the notch in the socket.

Step 9: Optional: Solder the Input Capacitors

Picture of Optional: Solder the Input Capacitors

If you have determined that your phono stage needs additional input capacitance, solder the capacitors in place in the positions shown in the pictures. These capacitors are not included in the kit.

If you don't need additional input capacitance, which is most likely, leave these positions empty.

Orientation does not matter for these capacitors.

Step 10: Solder the Screw Terminals

Picture of Solder the Screw Terminals

These screw terminals let you connect input, output and power without having to solder the cables in place.

Take a moment and think about which way you want the holes facing. If your enclosure has lots of space, have the holes facing outwards. If your space is constrained, it might be wise to have the holes facing inwards.

With this step, you are done soldering the Muffsy PP-3. The final steps will show how to power, wire and house the phono stage.

Step 11: Back Panel

Picture of Back Panel

The back panel is where you have your audio inputs and outputs, as well as the power connector and power button.

There are many ways to do this, have a look at this article to see how I did it:

Step 12: Audio and Power Wiring

Picture of Audio and Power Wiring

There are several ways of powering the Muffsy Phono Preamp, they all involve either a power supply or batteries.

The best option is using the Muffsy Hifi Dual Power Supply, (available as an option with the kit) which lets you power the phono stage using a wall adapter so you don't have to take the risk of connecting mains power. Have a look at these two articles for audio and power wiring:

Step 13: Enclosure

Picture of Enclosure

A nice enclosure is the key to a decent looking project. This article shows one of the endless possibilities:

As both the Muffsy PP-3 and the Muffsy Hifi Dual PSU are 84mm in width, they will slide right into the grooves in a B0905 enclosure. That means there's no need for drilling the aluminum cabinet.

Step 14: Adjust the Input Impedance and Gain

Picture of Adjust the Input Impedance and Gain

One of the great advantages of the Muffsy Phono Preamp PP-3 is the ability to change the input impedance and the gain. Most phono stages come with fixed settings for both of these parameters, while the Muffsy PP-3 gives you full control.

We did configure the default settings back in step 4. Now that you have a working phono stage, these can be tweaked. Input impedance and gain are set using the on-board DIP-switches.

Input Impedance

The switches to the left (with four settings each) will set the input impedance according to the table above.

The industry default input impedance for MM cartridges is 47k ohm. There are many cartridges that will sound better at other input impedances, and the Muffsy PP-3 gives you a whole range to choose from.

You are encouraged to play around with the input impedance settings to find one that suits your setup. Keep in mind:

  • Turn off (or mute) your amplifier when changing the settings
  • Don't play anything on your record player
  • Never set all four switches to the "OFF" position
  • Use the same settings for both switches

Gain

The gain is set using the switches to the right of the board, the ones with two settings, according to the table above.

Think of it as a fixed volume control for your phono stage. It will be useful to change this value, depending on the output level of your phono cartridge and the sensitivity of your amplifier.

Experiment with the gain settings to find the right one for your setup, but remember:

  • Turn off (or mute) your amplifier when changing the settings
  • Use the same settings for both switches

Comments

svit1 (author)2015-08-25

I am just started woth TT phono. I want to know where did you connect the ground from the TT to Phono? . Thanks.

svit1 (author)svit12015-08-25

I just saw that you linked the ground from input and out put all together to the screw right? Thanks

skrodahl (author)svit12015-08-27

Yes, that's right. This might explain it a bit better:

http://muffsy.com/audio-wiring.html

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