The BSTRD - Measurements

A project log for The Muffsy BSTRD - Class A Valve Preamp

An open source Class-A valve preamplifier and regulated PSU, complete with Eagle project files and detailed Bill of Materials

skrodahlskrodahl 12/19/2016 at 08:200 Comments

We've already established that The BSTRD sounds pretty nice, but how does it measure?

Keep in mind that my QA400 audio analyzer has a tendency to pick up 50 Hz mains when used with a computer connected to mains (it does better on a battery-only laptop), so this will skew the results a tiny bit.

I'd say it's what you can expect from a tube construction, or better.

The frequency range +0/-3 dB is 10 to 30.000 Hz. SNR is 83.5 dB (without A-weighting) and 93.2 dB (with A-weighting).

This thing produces harmonics, with the second being prominent. 3rd harmonic and greater are near or below the noise floor. As a result, it shows THD measurements of 0.35-0.4%.

The SNR/THD(+N) measurements have been done at 1 Vrms output. The numbers are will be even better at 2V output, which is the common output of modern equipment.

Frequency range (10 Hz to 30 kHz):

SNR/THD(+N), without A-weighting (1 Vrms output):

SNR/THD(+N), with A-weighting (1 Vrms output):