Tube Sounds

Tube Sounds

Immediately after power on, tubes make both acoustic and electrical sounds observed during the first few minutes. These sounds vary including (but not limited to) hums, buzzes, pops, sheens, shimmers, glass shattering, thunks, etc. The sounds are caused by thermal expansion of both metal and glass components of the tube. Sounds emitted may vary each power up cycle. Here are a few recordings to provide some insight as to the sounds made, in this particular case, on a particular power up cycle, by Linlai E-300B in an Eddie Current Studio B.

The recordings are calibrated, both electrical and acoustic, as follows:

-6 dBFS = 64 dB SPL

You may listen to them at any level to hear the type of sound. In order to experience them in context it is important to calibrate playback such that the recordings will be heard at actual sound levels. Also remember the acoustic recordings were made with the measurement microphone at approximately 1 cm between two 300B tubes. In other words, having your ear so close to the tubes as to risk burning the pinnae.



Electrical recordings were made with a Schiit Load set for 300R

Calibration
Using the calibration recording set the output level for the appropriate Vrms according to the following excel ready formula

Formula to determine Vrms calibration from headphone Sensitivity and Impedance:
=SQRT(($B$2*10^((A13-$B$3)/10))/1000)
where $B$2 is impedance in ohms
and $B$3 is sensitivity in dB/mW

Examples

12.2 mVrms Sennheiser HD6xx
11.0 mVrms HiFiMan HE-500
2.3 mVrms Focal Clear

Acoustic SPL level measurements


1. t= 0S Sound of Studio B Power Supply toggle switch at 1 meter distance combined with 300B tube glass sounds
2. t=42S Both electrical and acoustic thunk
3. t=60S Acoustic shimmer

Electrical measurements:


Flac files attached below