UPDATE:

Since only one extra resistor value is needed to get the higher impedances, it's been added to the kit. Now you can choose between these two options.

The input impedances on the Muffsy MC Head Amp can be changed to your liking. To help you find the right values, here's a nifty input impedance calculator.

You can play around with the values for R1, R2 and R3, and the calculator will show you what the input impedance choices will be. With all the switches set to OFF, the input impedance will be equal to R3.

The picture shows the values that are included in the kit.

PLEASE NOTE:
The resistors R3 MUST be installed, or you risk that the Muffsy MC Head Amp won't function.

Here's a suggestion for other component values, if you need a bit higher impedance:

After a lot of testing, ordering of components, assembling kits, more testing and writing build instructions, the Muffsy MC Head Amp kit has finally launched!

If you're looking for a way to use low output MC cartridges with your Muffsy Phono Preamp, or any other MM phono stage, look no further! Get it on Tindie today for only $79!

One very important requirement before launching the kit was to have a section in the build instructions on testing the circuit before you power it on, and troubleshooting the head amp if the tests fail. That all came together last night, and then it was just a matter of opening the gates at Tindie.

The build instructions for the Muffsy MC Head Amp contains every step from start to finish, including customization, testing and troubleshooting, all in one single page. This makes it easier to build than ever. And remember: If you don't know how to solder, EEVBlog's videos will get you going  in no time at all.

It's done, it's built, it's the first of its kind, it's plugged in, it sings! 

No hiccups, no artifacts, it just works. It's playing the 40th anniversary "Crime of the Century" by Supertramp right now.

Sweet :)

This does mean that, with some effort, the kit will be ready in about two weeks. The kit is available as of September 21st!

Also, the build instructions are very close to finished, I'm still writing the part about testing to make sure your head amp works before plugging it in.

http://www.muffsy.com/build-the-muffsy-mc-head-amp-mh-1.html

That's right, the MC Head Amp made it to the front page of HACKADAY, which is a great honor!

Unfortunately, there's some confusion in the article and in the comments that I would like to address here.

The Article Mixes the Phono Preamp and the MC Head Amp

The article shows the Muffsy MC Head Amp and the Muffsy Phono Preamp.

• The Muffsy MC Head Amp is a high quality gain stage that makes it possible to use an MC cartridge with an MM Preamp.
• The Muffsy Phono Preamp is a phono stage that applies RIAA equalization to the signal and amplifies it so it can be used with your stereo's input.

The HACKADAY article lists the specifications for the Muffsy Phono Preamp, which is why it goes on explaining variable gain and RIAA equalization.

Some of the Comments are Critical to the Project

Instead of tackling each comment, here's some more info on the Muffsy MC Head Amp:

• It amplifies very low signals, typically between 0.1 and 0.5 mV, to between 3.5 and 8.5 mV.
• With signals this low, (1/1.000th or less of the signal from a DAC or CD player) the noise plays a very significant role. There are only a handfull of op amps that can handle this task, I chose the LT1115.
• Sockets are used for the op amps, so that they can be replaced if anything goes wrong. It also used to avoid overheating the op amps when they are soldered in place. That makes sense for a DIY project. Leave them out if you are confident that you don't need sockets.
• There is confusion whether or not the PCB has ground planes. Rest assured, it does.
• The kit comes with shielded cables that share the ground. That's why it's only three inputs/outputs. Left, right and shared ground.
• A DC Servo does add capacitors in the signal path, even more of them than when using output capacitors. It's just another way of removing the DC component in the signal. This particular design even limits the bandwidth, starting the attenuation at just above 100 kHz.

So, why did I go for an op amp based head amp then?

• Because it's a kit, one that can be built by people who have never tackled DIY electronics before.
• Op amp circuits are easier to build, the result is very predictable.
• It works with the existing Muffsy power supply, no need to design more components.
• Discrete (transistor) based circuits can be better, but require matching of transistors and tuning after installation.

Summary

The Muffsy MC Head Amp performs wonderfully. It is completely silent, it has a very low noise floor and it does not add coloration to the sound. The sound signature of your MM phono stage will be what you hear when using the Muffsy MC Head Amp.

The Muffsy Phono Preamp measures and performs along the lines of really expensive solutions, but costs only $79. The circuit is much simpler and easier to build. If you enjoy making your own equipment, this project is for you.

Great care is taken to remove all sources of interference. The kit is complete, there's no question marks or missing pieces, which gives you a fully working product when you're done building it, and you won't get better quality PCBs or components anywhere. Use the recommended enclosure, and you don't have to do any metal work, the circuit boards slide into the grooves of the cabinet and the back panel completes it with all switches and connectors.

Wondering how the Muffsy MC Head Amp measures? Look below for the numbers.

• Topology: Dual mono
• Gain: 24.6 dB
• 0.3 mV input = 5 mV output
• 0.5 mV input = 8.5 mV output 
• Input impedance: 47 - 100 ohms, in four steps
• THD: < 0.1 % *)
• THD+N: < 0.6 % *)
• SNR:  71.8 dB, referenced to 0.5 mV input @ 1 kHz
• Frequency Response: +0.0 / -0.1 dB (20-20.000 Hz)
• IMD (ITU-R): 0.001 %
• DC Offset: < 0.1 mV
• Dynamic range: > 110 dB, referenced to 0 dBV output
• Power requirements: +/- 15V at < 50 mA
• PCB Size: 84.0 x 59.4 mm / 3.3 x 2.3 in

You may have noticed that the Muffsy MC Head Amp is on its way. UPDATE: It's already here!

Here's why you might want one for yourself.

The basic purpose of a head amp is this:

• To use a low output MC (moving coil) cartridge with your existing MM (moving magnet) phono stage.

An MC cartridge typically has 1/10 of the signal strength of an MM. The signal from your MC pickup will be amplified by the head amp to a level that can be handled by the phono stage you already own. It does so without adjusting the RIAA curve. But why?

As it turns out, there are a number of reasons:

• Your favorite phono stage or amplifier only has MM input
• The quality of the MC input on your phono stage or amplifier isn't good enough
• A step-up transformer is too expensive
• Your current MC phono stage lacks the settings you need
• You want to try what MC cartridges are all about, without having to buy a new and expensive phono stage

The MM and MC cartridges behave quite different. The best topology for low noise with MM is not the same as that for MC. In short: MM cartridges need low current noise and MC cartridges need low voltage noise, but an amp can only have one of those. If there's one input stage on your MM/MC phono stage, you can be relatively sure that it is optimized for only one of them. Most likely moving magnet. A dedicated head amp ensures the best sound quality at all times. Now you can use your vintage amp, tube phono stage or any other MM phono stage with an MC cartridge.

If you have found the phono stage of your dreams and it only has MM input, you will need a head amp or a step-up transformer in order to use an MC cartridge. Step-up transformers range from expensive to very expensive. That's not to say that phono stages or head amps don't, but they can be had for less money. Look no further than to this site for proof of that.

If you're on the lookout for a DIY MC head amp, the Muffsy  MC Head Amp is among the simplest and best options out there. And I'd wager it'll be the cheapest as well. It is extremely easy to build, can be had with both a power supply and a back panel, and does not require any drilling or enclosure modifications of any kind. 

Every care is taken to ensure the very best sound quality, and to avoid all noise and distortion. It measures and sounds excellent, and you get the satisfaction of building your own hifi gear.

Stay tuned for more in-depth information about the Muffsy MC Head Amp.

While we're waiting for the Muffsy MC Head Amp, here's a sneak peek of the new back panel for the B0905 cabinet.

There are a lot of considerations to make when dealing with the very low output from an MC cartridge. Noise and interference should be avoided in all parts of the design, and that's why there's a new back panel available.

The back panel for the Muffsy Phono Preamp uses pieces of wire to manually ground the RCA connectors and the ground screw. For MC, these could in certain circumstances act as small antennas, so best get rid of them. As you can see from the above picture, there's copper exposed around the holes for the connectors. These will make contact with the connectors, and there are copper traces beneath the black coating that connects them together.

Not only is this better suited for low level signals, it's even much easier to build.

The Muffsy Phono Preamp is, and will continue to be an MM phono stage. Moving magnet and moving coil cartridges require different operational amplifiers, so a combination of MM and MC is not feasible at this size and price point. 

Until now, the only way to use the Muffsy with moving coil cartridges has been to use a step-up transformer or a separate head amp (of which there aren't many around). Now that's about to change!

The Muffsy MC Head Amp is a very high quality amplification stage that brings the MC signal up to MM levels, and it goes between your turntable and the Muffsy Phono Preamp (or indeed any MM phono stage).

The design goals for the Muffsy MC Head Amp have been:

• Dual mono topology
• Signal-to-Noise ratio above 70 dB
• Variable input impedance
• DC servo to eliminate input/output capacitors
• Gain of 24.6. 0.3 mV input gives 5 mV output / 0.5 mV gives 8.5 mV out
• Same great PCB quality as the other Muffsy products
• The Muffsy MC Head Amp will fit in a B0905 enclosure together with the Muffsy PSU
• Easy and understandable build documentation

I've been running the latest prototype with an Ortofon MC30 Supreme for quite a while now, and the Muffsy MC Head Amp is brilliant. It's absolutely dead quiet and offers the same pitch black silent background, the great soundstage together with the rich and revealing sound that the Muffsy Phono Preamp is known for.

Be on the lookout for the Muffsy MC Head Amp very soon. Here's some more information about the project from the very beginning: https://hackaday.io/project/12483-muffsy-mc-head-amp