Phono Amplifier

Introduction¶

A teeny, tiny, awesome sounding and accurate, stereo phono amplifier – so you can plug your record player in, and get some sound coming out!

It’s super tiny because I wanted to take up as little space as possible, since you’re not interacting with it – it does nothing except take external signals and route them into your modular setup.

For instance, the sound output isn’t included on the front panel. Why? Because in my scenario you’d internally connect them directly to another module. If they’re always connected, there’s no reason to take up all this extra space with a two whole audio jacks.

Of course, you can always add output jacks (Eurorack or line level; or both!) by putting a tiny jack tile next to it; something like this by Erthenvar. Note that their tiles might be of a different “1U format”.

Photos¶

Front panel design still TBA. Once I work out what aesthetic I’m after, and do a respin to fix a board dimension issue.

Sound quality¶

On paper¶

It’s designed to accurately reproduce the RIAA curve to 0.1dB up to 13kHz, -0.6dB at 20kHz.

[graph of flatness from simulator goes here]

However, I’ve yet to do a proper noise analysis on the constructed circuit, so real world will probably be worse, but I doubt it would be by very much.

Noise-wise, you get about 76dB signal-to-noise which is very good! But to tell the truth, noise figures for most good preamps are pretty useless; unless you have a really crappy , but for most preamps, well, I’ll be honest; vinyl surface noise will almost always dominate.

Real world¶

In the real world? Well, super subjectively; these sound… really damn good. Low end response is better. I built another, cheaper design (less components; some electrolytics) that didn’t seem to have the same low frequency response, though the other bands seemed fairly the same.

If you didn’t need to play very bass heavy music, you could definitely get away with the cheaper, lower component design; which was just the textbook RIAA response curve with two opamps.

That said, both of these DIY designs blew out of the water a cheap portable preamp I purchased, and the built-in phono preamp in a Pioneer DJ mixer I’ve used.

The only downside is you can really tell when a record is mastered terribly. ;)

Specifications¶

Size¶

1U, 14HP (70mm)

Input¶

• RCA jack x2 (for stereo input)
• 5mV @ 5cm/s groove modulation typ.
• Ground point

Output¶

• Stereo output at line level (with ≈30dB headroom)
• Stereo output at 10v p-p with 2dB headroom (Eurorack level)

Gain¶

+11dBV (+13.2 dBU)

Settings¶

Adjustable loading capacitance between 0pF and 767pF

Additional information¶

Loading resistance fixed at 47k ohms

Purchase¶

Not yet; though if you’re interested, please email me!

Schematic¶

Click for PDF version