Hifi Preamps for your Record Player

By: skrodahl | October 16, 2018

Several people have been in touch lately with questions on how to modify the PCB into something it isn't right now. Popular requests are balanced inputs and/or balanced outputs, and DC servo on the outputs.

The PCB itself doesn't really lend itself to any of the modifications above, but you could always try doing add-on boards or roll your own from the open source freely available schematics.

An explanation of the Muffsy Phono Preamp PCB layout can come in handy for such alterations. And wouldn't you know, here it is:

Muffsy PP-4 PCB Layout
The Muffsy Phono Preamp PP-4 PCB Layout

Modifications you can do are changing the input impedance and altering the variable gain. I'm also happy to announce that the gain calculator has been updated to show the output voltage and voltage gain:

Muffsy PP-4 Gain Calculator
Muffsy PP-4 Gain Calculator

Finally, if you want to make major modifications, a way of simulating the circuit would really come in handy. Well, here's the Muffsy Phono Preamp LTSpice simulation file.

Muffsy LTSpice Simulation
Muffsy Phono Preamp LTSpice Simulation

By: skrodahl | March 15, 2017

The instructions give you three alternatives for powering the Muffsy Phono Kits. Here's another one:

Step-down power converter - Dual power supply
Step-down converter - Size comparison

This step-down power module is available on Tindie, and can provide up to two amperes of power. Use two of them and connect a 15V DC power supply at VIN/GND as shown in the picture above, and you will get a +/-12V output. This will provide sufficient headroom for the Muffsy Phono Kits.

The ripple is some 18-20 mV. This is waaaay higher than the Muffsy Power Supply, but should work reasonably well. Especially if you're strapped for space.

A small word of caution: The output voltage is set using very small surface mount resistors (included). You will have to do SMD soldering. It keeps the common ground though, so it should be able to work alongside other power supplies with all grounds connected.

No complaints on the price either, I paid $20 for five of these modules and international shipping is $3.

By: skrodahl | March 11, 2016

Hot on the heals of the official Muffsy PCB, here comes another option.

Over at theslowdiyer's blog, you can now find the project files for the Muffsy Clone.

The Muffsy Clone PCB

Everything you need to build your own Muffsy Clone is available at his site. There's an impressive lot of information about his design goals and on how you should go about building the project.

Go here to see all of it, and build your own Muffsy Clone: 

Theslowdiyer - Muffsy Clone Project Files

If you are looking for a suitable power supply, theslowdiyer's got you covered as well with his GP-PSU v2.

theslowdiyer's GP-PSU v2 - Silkscreen

By: skrodahl | January 27, 2016

Yngve from Norway has built a total of five Muffsy Phono Preamps by now, but this has to be his coolest project ever. When he bought a Dual 1225, he decided to give it an integrated phono stage, using the Muffsy.

Muffsy compared to the Dual 1225

The Dual 1225 was opened, the drill was brought out, and the Muffsy placement was decided.

Muffsy mounted inside the plinth

Next is the cabling, Ynge decided to connect the tone arm cables directly to the Muffsy input.

Cabling in progress
Tone arm cables

There was even space for a power supply and a transformer inside the Dual 1225.

Yngve reports that he's very happy with his upgraded Dual. There is absolutely no noise or any distortions, so he has succeeded with his well thought out layout.

Power supply mounted inside the Dual 1225

By: skrodahl | January 26, 2016

In Copenhagen, just across The Bridge from me, lives slowdiyer. He has designed the Muffsy Clone, his own version of the Muffsy that suits his needs exactly.

It is a mono version with single instead of dual op amps, which lets you use op amps like LME49710, LT1063, LT1028, AD797, OPA627 and more.  Being mono, you can use two power supplies and run it as dual mono if you'd like.

It does away with the variable input impedance, retains the variable gain and adds a mute circuit. The Muffsy Clone has space for a really large output capacitor as you can see in the picture below.

The form factor is 100x37 mm, compared to Muffsy's 84x56 mm. The boards are designed to be stackable.

The Muffsy Clone

There are a lot of other considerations that he's taken care of, all of which are described here. The same blog post also includes all of the project files, enabling you to make one for yourself.

Muffsy Clone in Enclosure

I'm anxiously awaiting his listening experience, as he's yet to finish the power supply to fire it up.