2016 SP-1 Pro Valve Expander

What is the SBS Designs SP-1PRO 2UBE Processor?

The SBS Designs SP-1PRO is a Vacuum 2UBE Processor with 7 front panel useable controls designed to let the end user Sweeten up and improve the dynamic range of any full range source.

A carefully designed expansion process will bring out exciting detail that is so often masked by recordings that are compressed and engineered to be mono compatible. The SP-1PRO will also bring back amazing detail to digitally stored / processed recordings which where subject to data reduction processing.

SP-1 PRO has a sub bass expander and an extended range of top treble expander. These expanders are top quality fully analog which use no vca’s and contain no noise or distortion generators. They add dynamic range by controlling the target frequencies with photo resistors.

SP-1PRO Front Panel:

Front Panel Low & High Thresh Controls:

Section A:

SP-1 PRO offers front panel Bass & High threshold pots that allows the end user to adjust at what level the low frequency and high frequency expanders begin to increase dynamic range, turning down a control all the way bypasses that expander.

These expanders are subtle and employ control feedback systems to monitor the depth of expansion and prevent obtrusive runaway operation, even if the controls are turned up too high. The low frequency expander has a program dependent release time limit, so it will not add any annoying droning or rolling bass to a source.

The high frequency expander operates relative to the overall spectrum of the music being played, so it will not produce over pronounced highs that sound like someone turned up a treble control too far. These expanders will not create something that is not in the recording. The material must contain low and high frequency information for the processor to work with.

The expansion circuit in turn feeds a two stage zero feedback tube amplifier, these tube amplifiers are the same class A types used as gain stages in vintage recording equipment. They are not designed to create tube distortion like a guitar amp, but they will warm the sound by imparting the natural characteristics of the triodes.

Front panel Tube mode control operation:

Section B:

One of the most unique features offered with the SP-1PRO is Low & High front panel “Tube Mode” Presence Adjustment, controls.

SP-1PRO offers Independently controlled front panel Tube Mode controls that are designed to increase or decrease the effective presence of the expansion process triggered by the larger front panel Low & High Thresh pots.

Setting the 4 front Panel Tube Mode controls to be as low or as high as you desire sets the Low & High Thresh pots to have as minor or as drastic amount of an effect on any source you are mixing or playing back.

Imparting the Tube Stage by (Offsetting The Tube mode controls):

SP-1PRO gives the end user the ability to offset the 4 Front Panel Low & High Tube Mode pots for the left and right channels independently.

Choosing to offset the Tube Mode pots, offers slight natural differences in Transfer function between the vacuum tubes, improving the stereo image of an otherwise clinical and “One Dimensional” recording.

That Vintage Sounding “Tube Warmth” is imparted on to the recording, and helps enhance the apparent dynamic range of the music.

Front Panel Bypass & Headphone Out:

Section C:

SP-1PRO offers a true front panel wet dry bypass switch for comparing. The SP-1PRO Features a high quality Headphone amp with front panel level control.

CH1 & CH 2 Balanced or Unbalanced mode:

With circuit layouts from classic designs to modern designs varying, The SP-1PRO has independent internal balanced or unbalanced switches on the circuit board This was offered so the SP-1PRO can be used in any fully balanced or unbalanced circuit without any issues of loss of drive.

SP-1PRO I/O Panel

XLR Balanced inputs & outputs
Master input gain trim


The SP-1PRO brings the same open & dynamic signature sound as our other Designs with a tremendous amount of depth, separation & improved imaging that lets the end user choose the minimum or maximum amount of tube warmth of the bass separate from the top end of the tubes stage with 2 front panel threshold controls.

Front panel Low & High Threshold controls:

One of the strongest selling points of the SP-1PRO is the Low frequency & High Frequency Front panel Threshold pots. Adjusting the Low & High Thresh controls allows the end user to warm up a source and improve dynamics on the fly and take a recording in a studio or any application to the next level.

The Low & High Thresh controls adjust at what level the high and low frequency expander triggers. The low & high frequencies are separated, expanded then mixed back together and then sent to the tube output buffers. Whatever the tube does is a product of the level you choose to set on BOTH front panel knobs in tandem with the level of music going into the unit.

Front panel Tube mode control:

1. The Tube Mode controls give you the ability to control the effective presence of the expansion process triggered by the larger front panel Low & High Thresh pots.

2. The Tube Mode controls give you the ability to set the intensity of front panel Low & High Thresh controls to have as minor or as drastic amount of an effect on a source.

SP-1PRO Specifications:

Freq resp: 12 Hz to 30 kHz +/- .1 Db
Roll off: low = – 2 Db @ 8 Hz, high = – 2 DB @ 44 kHz
Max line level in = + 21 DBu depending on rear pot setting
Max line level out = + 19 DBu
THD thru solid state circuits = .03%
Second harmonic distortion thru tube output section = .3%
AC Power Draw: 25 watts

SP-1PRO Applications:

Recording Studios
Mastering Labs
Live PA

2014 SBS Designs SP-1PRO Now Shipping!


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