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MC head amplifier design ideas
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Principles of MC Head Amplifier Development
What do we expect from such a circuit?
Let's discuss some easily measurable parameters:

• Signal to Noie Ratio
The input signal is low enough (<1mV, sometimes below 0.1mV). It is a real challenge to build a low-noise amplifier for this input level.
Fortunately, it is not impossible: semiconductor devices are available with very good noise parameters.

• Distortion
In this case the low level of the input signal comes in handy: in general, higher input signal produces higher distortion in such devices. In addition, we can use amplifiers without feedback (which is generally preferred in the audiophile world) and the distortion of such a circuit can be theoretically calculated or simulated easily and exactly (see the details later).

• Frequency Response
Fortunately, this stage does not have any parts which could bother the frequency response (at least in the audio frequency range), so the flat response can be reached easily. Only the decoupling capacitor (which can even be omitted in some cases) could change it, but it is calibrated for noise and therefore its corner point is out of the audio range (see the noise calculation page for details).


Do we use transformer instead?
I am got involved in a religious war again. The audiophile world is divided - this question probably cannot be answered generally. At last I vote for head amplifiers - maybe because I am tinkering a lot and I had problems with transformers. Especially as the transformers always provided 50Hz hum for me, even the expensive ones. (However, I tried only few of them). Now I prefer head amplifier and I hope the device documented here is in the running against the expensive step-up transformers (and head amps, too).

Circuit Development
When I got my first MC cartridge (in the 80s), I started to build head amplifier. There were a lot of circuits in the magazines, and I tried some of them. Unfortunately, none of them was acceptable: most of them was noisy, some of them received the radio, but every single circuit was problematic. I had to start my own circuit development.

• First Tries
As I mentioned before, I had tried some circuits without success - I do not want to mention more details about them.
Let's see my first successful head amp:

Simple, but surprisingly good head amplifier
In those days (in the 80s) it was problematic to find proper transistor type for such a MC head amplifier. A simple audio transistor (e.g. BC413) produces too much noise in this circuit - however, I found such circuits in the magazines. I read an article about internal base-connection resistance, and BFW16A is mentioned there, as a good candidate for MC head amp. I tried this circuit and found it the best of all: it has low noise and good immunity against EMI.
Usually the simpler is the better - as in this circuit too. The more complicated circuits produced more problems for me: not just more noise, but radio reception (EMI), and others. I am not against feedback, but in this case the feedback circuit increases the impedance in the base-emitter stage which means more noise, and decreases the EMI immunity. The input decoupling capacitor has large value for the same reason: reducing it to e.g. 220uF increses the noise in the lowest range significantly (see Inb and Vnb description on the noise calculation page).
There are better transistors today, see below.

• Circuit Diagrams
These are my newest circuits (in 2018):