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Vacuum Tube Sound Samples
How does one describe the sound of a vacuum tube? Here you will find some sound samples that might give at least an inkling. Granted that the samples you find here will only be as good as your reproduction equipment, but I hope that these will at least whet your appetite to hear the real thing.
Special thanks to Mikkel Simonsen for graciously hosting this site.
Tube Preamp Real McTube "Li'l 4x4" "BAMTRAT" "MiniBlok"

The High-Precision Tube Phono Preamplifier

The samples were recorded directly from the "Standalone Phono Preamp", the identical circuit as used in the phono section of the "RA-100 Reference Amplifier". The turntable used was a TEAC model TS-280S, with Audio-Technica AT125-LC (Shibata stylus). The output of the phono preamp was fed directly to the line input of my Audiotrix 3D-XG sound card, and recorded in realtime using CoolEdit.

The audio (wav) file is a short 12 second snippet from the resulting recording. This is provided mainly to eliminate any possible distortion introduced by the MPEG encoding process. The second file is the MP3 of the entire track, encoded at twice the normal bitrate (256 kbps).

The track selected is from "Audio System Test Record", produced in 1984 by McGill University Records with the assistance of the National Research Council of Canada, and distributed by Sound and Vision magazine. From the record's liner notes:

  "Donald Steven: On the Down Side Keyboards - Art Maiste; Sax - Janis Steprans; Synthesizer - Luc Beaugrand; Drums - Pierre Béluse; Bass - Michael Donato. Producer: Donald Steven; Recording Engineer: David Kelln.

      "On The Down Side is rife with especially well-recorded, subtle percussion sounds, useful for checking tweeter performance. The cymbals should have a gentle shimmer; later, a metallic ring. The saxophone should sound like a sax, not like a kazoo (the latter a sign of midrange colouration), and be free of harshness or stridency. At the beginning, are the deep electric bass notes clearly defined and differentiated? Can you hear the wind chimes? The recording was made on a 24-track machine with some artificial reverberation, equalization and compression carefully applied where needed."  

The "Real McTube II" Overdrive Preamplifier
  1. Clean guitar (128 kbps mono MP3, 25 sec., 398 kB)
  2. Mild overdrive (128 kbps mono MP3, 34 sec., 542 kB)
  3. Full blast distortion (128kbps mono MP3, 46 sec., 728 kB)
  4. Bass, full distortion (128kbps mono MP3, 18 sec., 286 kB)

These sound clips demonstrate the range of possibilities provided by "The Real Mctube" instrument preamplifier. All clips are direct recordings of the output of the prototype "Real McTube II", fed from a Stratocaster-style guitar custom-built for me by Doug Thompson, strung with "jazz" gauge strings. Clips 1 and 3: both Bartolini pickups; Clip 2: bridge pickup only.

A more recent addition (May 2001) is the bass clip. Obviously, I'm not much of a bass player... but the clip should give a pretty good idea of how the Real McTube works with electric bass. (This one was a Yamaha RAX200 with old dead strings.)

More "Real McTube II" Samples
  1. Clean guitar (128 kbps mono MP3, 12 sec., 190 kB)
  2. Low gain (128 kbps mono MP3, 14 sec., 219 kB)
  3. Maximum gain (128kbps mono MP3, 16 sec., 254 kB)

(December 2001) - Jeff Leites sent these excellent sound clips from his implementation of the McTube. These are good in that they demonstrate various gain settings with essentially the same source and tune.

Jeff actually sent an additional clip, at medium gain setting, but as he writes, "I wish I had turned down the gain a little bit for the 'mid gain' sample, though I can see there is a slight difference on the graphic when I recorded it with Sonic Forge XP, it sounds very close to the 'max gain' sample."

Pedro's "Real McTube II" Sample

(January 2002) - Pedro sent yet another clip, this one from his 240VAC implementation of The Real McTube. Further information about his project is at his website (under Effects --> McTube 2).

Brad Davis' "Real McTube II" Sample

(April 2002) - Brad Davis sent this clip, and writes: "Hello. Thanks for such a cool project. I completed the circuit (it's still looking for a home chassis, though) and really like the sound! I DO have a few questions for you, but first please accept and post this sound byte mp3 I recorded tonight with the circuit lying in a ball in the floor.... I'm using my fender american deluxe fat strat w/ a reissue Fender Deluxe Reverb Amp. I was looking for a good vintage distortion box and was interested in learning about vacuum tube stuff (this stuff is cool!), so this project was a good intro.

Once I get all the hiss/noise issue solved, I'll be a happy camper (oh, and a chassis)...

"This sample was recorded using Cakewalk Pro Audio 9 , Shure SM57 mike, and above mentioned equipment."

The "Li'l 4x4" Instrument Amplifier

  1. Li'l 4x4 Demo (128 kbps mono MP3, 28 sec., 450 kB)
  2. Get the Full version from my IUMA.com site (Sor - Study in B minor)

This is a short clip of a recording I made using my Stratocaster-style guitar, plugged into the "Li'l 4x4" instrument amplifier. It was close-mic'd, no equalisation or other FX; it went straight from the mic into the computer. Notice how clean and quiet this little thing is?

If you want the full performance of this tune, pick it up from my IUMA.com site (Sor - Study in B minor). For public release, it was only gently massaged with a touch of reverb and gentle EQ (mids depressed a bit).

"BAMTRAT" Tube Theremin

  1. Raw Demo (128 kbps stereo MP3, 1 min. 12 sec., 1.1 mB)
  2. Processed (128 kbps stereo MP3, 1 min. 9 sec., 1.1 mB)

This is a "live" recording of BAMTRAT, my "Battery AM Tube Radio Authentic Theremin". The left channel is the signal as picked up by a microphone in front of the built-in speaker, and the right channel is the direct input taken from the speaker terminals. Pretty much all of the instrument's playable range is demonstrated here. Please be kind with your critiques of my theremin playing style! ;-)

The "processed" version was given a mild roll-off (to simulate being played through an instrument cabinet) and stereo reverb added (to simulate playing in a large hall).

"MiniBlok" SE & PP Triode Amplifiers

This is a little experiment to determine whether it is possible to hear the effect of the "harmonic signature" (i.e. the relatively high 2nd harmonic content) of the single-ended triode (SET) amplifier. Furthermore, is the SET sound better due to "euphonious distortion", or worse because of inaccuracy? A new addition is the output of an otherwise similar push-pull amplifier, for critical comparison.

The input file is a short snippet from Beethoven's Ninth Symphony (as recorded by Bruno Walter in 1959), ripped directly from CD. The output file was recorded directly from an 8-ohm dummy load resistor at the output of the little MiniBlok SET amplifier. The level was set such that the highest peak just reached the 2-watt peak power level (4 volts into 8 ohms, corresponding to 1 watt RMS, if the source were a sine wave with the same peak value).

Save the two files to disk, and listen to each in turn (preferably using good headphones plugged directly into your sound card). You may have to go back and forth a few times to hear the difference(s). Notwithstanding the slight loss of highs due to the inexpensive output transformer, do you hear a "warmth" or "tubey" sound in the output file? If so, is that a Good Thing or a Bad Thing?

NEW Output from the MiniBlok II push-pull version is now also available for comparison both with the source signal, and with the output from the single-ended version. Can you hear a difference? Which do you prefer?

Back to MiniBlok Project
Back to MiniBlok II Article

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Carefully crafted original compositions by Fred Nachbaur

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