About the RPX-35 Bus Compressor
If you're into unique audio equipment, the RPX-35 Germanium Stereo Compressor is what your studio needs!
This compressor is the perfect choice to enhance the quality of your sound with that unique vintage feel.
With high-quality components and a design designed to deliver the best in terms of compression and sound fidelity, the RPX-35 is ideal for musicians and producers looking for the distinctive timbre and warmth characteristic of germanium transistors and diodes.
This incredible Bus Compressor has numerous distinctive features, enabling it to achieve an incredible sound range.
So, let's explain in detail the entire design of this incredible equipment:
- Audio signal stage: At the input of the circuit there is a dual operational amplifier, balancing the signal electronically.
The signal then goes through a signal normalization stage (before sending this signal to the sidechain). Between the signal normalization and the sidechain path input, there is the Ratio control, which precisely defines the compression factor between the sidechain and the signal floor.
After this signal normalization stage, there is a 2N3055 transistor (which is the first post-compression gain boost and responsible for the cleanest stage of the equipment).
As soon as the signal leaves the 2N3055 transistor, we add a sound coloring circuit to the equipment, which has tantalum and electrolytic capacitors (this function is on the front panel of the equipment shown in the Clean Comp/Dirty Comp Switch).
After the coloring stage, we arrive at the germanium transistor, which is responsible for a soft saturation in the audio signal (we explain below how the saturation of the germanium transistor works in conjunction with the diodes).
Following the germanium transistor, we have the final stage composed of another operational amplifier, where it is possible to compensate for the post-compression output gain (this gain is shown on the front panel of the equipment by the MASTER knob).
And finally, the equipment's output signal is balanced by a 600:600 Greenbox audio transformer, which serves not only for balancing, but also to deliver a warm and very present tone!
- How the germanium transistor saturation/drive works in conjunction with the germanium and silicon diodes:
We spared no effort, working tirelessly day and night, to achieve excellence in terms of saturation and drive for this incredible audio compressor. We use unique and differentiated techniques that provide an unparalleled sound experience.
- So, let's understand how this saturation and drive circuit works:
We add a germanium transistor per channel; these transistors, in turn, generate around 5% harmonic distortion, creating a fantastic coloration. This harmonic distortion is enough to give color to the audio and at the same time maintain a clean sound.
Now, if you want to go further and really create a more aggressive saturation, which with higher gain levels ends up becoming a drive signal, this equipment does that too, and you just need to open the Input Drive control on the front of the equipment. It is in this context that the germanium and silicon diodes appear to act together with the germanium transistor.
In this case, we created a dedicated circuit between the diodes and the transistor, making it possible to saturate to a point where it can "ruin" the audio. And all this happens before compressing the audio signal, since the saturation diodes are in the input stage of the equipment, and still capture an additional percentage of the output where the germanium transistor is; that's right, this equipment makes this magic happen in a very peculiar way, resulting in an incomparable sound.
To make this happen, just operate the two DRIVE INPUT and INPUT GAIN knobs on the front panel of the equipment, and this way you can have a super clean or super dirty compressor.
In short: it is possible to go from a super clean sound to a velvety sound, and even beyond that to a super dirty and harsh signal!
- Compression stage (sidechain): The RPX-35's sidechain is very different, as it combines an optical compression stage plus a FET stage with two transistors. This combination allows for very precise and efficient compression, with a result that stands out from all stereo compressors ever manufactured.
In the optical stage, we have two VTL5C4 optical cells. This cell model has a perfect response time for this compressor project that we created, because together with the FET stage it will act with the ideal dynamics to provide the compression we wanted so much!
In addition, this compressor has the CURVE (Knee) function, which is selectable by a rotary selector on the front panel of the equipment. For this compression curve function, we selected different diodes to act appropriately in the circuit; such as silicon diodes, germanium diodes and a zener diode.
Also in the sidechain, there is a selector on the front panel to cut the compression's bass; allowing for even more autonomy to the sidechain stage, making smooth or more aggressive cuts when compressing audio signals with very evident bass frequencies.
In addition to all this, the compressor has ATTACK and RELEASE switches with 9 different positions for each function; a COMPRESS control that controls the signal level sent to the sidechain; and a RATIO that controls the compression factor.
In short, we have here the pinnacle of stereo compressors!
Included Items
Stereo Bus Compressor RPX-35, Greenbox external power supply, instruction manual, warranty.
Warranty: 1 year
Specifications:
General Info Section:
External Source 110/220 Volts ~ (50/60Hz)
Power Consumption +/- 15 VDC (General Circuit)
Total Consumption 85mA (approx.)
Signal Section:
THD 0.0045% @ Minimum Germanium Drive (@ 5dB / 1khZ) - to 35% @ Maximum Germanium Drive (@ 5dB / 1khZ)
Equivalent Input Noise (noise floor) -87dB @ 2dB Gain / -75dB @ Max. Gain
Out Level +15dB (max.)
Input Impedance 10k Ω
Output Impedance 600 Ω (with audio transformer model TT-6060B)
Audio Transformer (Turns Ratio) 350 Ω
Max. Attenuation -30dB approx.
dB Reduction Analog Meter
Frequency Response 5Hz to 22kHz (2.5dB Gain)
Analog Meter Gain Reduction: -30dB
Input/Output Balanced (XLR)
Power Supply Fonte Externa Greenbox (inclusa)
Dimensões 1U x 19" x 25cm (profundidade)
Peso 2,920 quilos.
DOWNLOAD MANUAL ->
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