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DBX 100 Boom Box

Sub Harmonic Synthesizer

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DBX 100 Boom Box


In order to get as much music as possible on a record, recording engineers must limit the depth and excursion of record grooves. So in the recording process, the lower frequencies are often deliberately reduced or cut off altogether.

The DBX 100 recreates this lost portion of the audio spectrum by seizing information in the 50-100 Hz range, creating a signal one octave lower (25-50 Hz) and mixing this new signal back into the program.

By recreating the bottom octave with the DBX 100, you can hear heightened accuracy in the bass, and actually feel the power inherent in a bass note. The solidness and three-dimensionality of bass heard in a live performance, which can be physically experienced, are restored.

The DBX 100 can be enjoyed with almost any component system. It is easily inserted in the tape monitor circuit of your receiver or amplifier.

There are just two controls: One is a Synthesizer control that sets the amount of recreated low frequencies you put into the system. The other is a Low Frequency Boost control specially contoured to produce a smooth blend of the synthesized notes into the music.

As you regulate the Low Frequency Boost control, your ears will tell you when it is set right. The DBX 100 will intensify your listening experience, no matter what kind of music you listen to. If you like rock or jazz or disco, and you have a higher-powered system, the 100 is capable of creating a new dimension, where the physicality of the music will engulf you.

If you like classical music, try listening to Tchaikovsky's 1812 Overture or Beethoven's Sixth Symphony with the 100. The attack of the tympani and the richness of massed double-basses produce a sensation unlike anything you have ever experienced from recorded music.


Dynamic range (peak signal to weighted background noise): 100dB

Input level (nominal): 300 mV

Output level (maximum): 7V rms

Frequency response: 20Hz to 20kHz

Total harmonic distortion: 0.1% typical

Dimensions: 95.25 x 185.7 x 260.35mm

Weight: 2.26 Kg


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re: 100 Boom Box

I would give many thanks to cutloose for the upload of the schematics of DBX 100.
And a medal if the drowing of the same schematics is done by himself !!!!

re: 100 Boom Box

Thanks PUMA05. Yes I did do the drawings myself, reverse engineered off the circuit boards. Took quite a while I must say!
Appreciate any advice if there are any errors found.

re: 100 Boom Box

R83 8,2 not 820 according to previous comment.
The capacitors are strange values (particularly C5) and some missing, like C8.
100Hz R2/R3 (12M) seem as off as C5, should be some ~12k rather than 12M.
R72 and around makes no sense (loop?)

Kudos for the REed schematics, awesome job! Appreciating it much. Just missing joint dots ;-)


edit: musing about synth Q1/Q2, could you re-check the pinout? (base-collector swap?)
The legend on synth brd sheets say "BU2725" https://html.alldatasheet.com/html-pdf/16945/PHILIPS/BU2725DX/247/1/BU27... which seems unlikely for synth and may fit for same annotation components in PSU, Last sheet says "BC341" which is more plausible.

re: 100 Boom Box

Many thanks For the R 83 value. I am still looking For schematics or service manual, it seems impossible to get it.
Someone has had more luck than me?

re: 100 Boom Box

Many thanks For the R 83 value. I am still looking For schematics or service manual, it appears impossible to get it.
Someone has had more luck than me?

bobbysdad's picture

re: 100 Boom Box

Please..... can someone post the schematic to this.
Mine just stopped working and I miss it like crazy.

dead DBX 100

I have one and I'm in great need of schematic diagram.
If anybody has one of knows where to get it, please contact me
Thanks for help, Tony

re: dead DBX 100

Hi, also I have a dead DBX 100, and I am looking for schematics with no results. Mine have a burn out resistence immediately near the ac transformer, the name of the resistence is R 83, the value of the resistor is unknown becouse the hight temperature has burned the colour code.
Perhaps we can help each other with crossing informations.
Thanks for any help.

re: dead DBX 100

R83 is 8.2 ohm (Gray Red Gold Gold)
I just got one free and I see the manual but do I really need a dbx 100? I just listen to old rock albums and CDs.

re: dead DBX 100

Would you have a schematic diagram for this dbx 100?
Regards, Tony

re: dead DBX 100

Do you still need a schematic?

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