The RB 500 ME (Rubber Bands 500 Mastering Edition) is a stereo passive Pultec EQP-1A-style equalizer occupying two API 500 slots. It is the first stereo unit of this type in the 500-series format – an unusual proposition in a market where most Pultec 500-series offerings are mono only. The input is transformer-balanced via Carnhill transformers (one per channel); the output runs through Edcor transformers (one per channel) – four audio transformers in a single dual-slot module, which is what gives the unit the density and tonal weight that reviewers compare to full-sized rack processors. The filter section is entirely passive; a discrete Class A driver stage recovers the insertion loss of the passive network. ELMA switches on all frequency selections and stepped pots throughout ensure full session recall. Frequency response: 20 Hz – 20 kHz ±0.1 dB. THD+N: 0.012%. Crosstalk: 75 dB. Power consumption: 7 W.
Independent boost and cut frequency selectors in the bass band – the key mastering feature
The classic Pultec EQP-1A links the boost and cut frequency selection in the low band to a single shared switch – boosting and cutting the same frequency simultaneously produces the characteristic asymmetric curve with an accentuated fundamental and reduced mud. The RB 500 ME separates these selectors: an independent frequency switch for the boost section and an independent switch for the cut section in the low band. This means boosting 30 Hz and cutting 100 Hz simultaneously is possible, producing a bass silhouette with an extended sub-bass shelf and a thinned-out lower midrange – without the two selections blocking each other on the same switch position. Bass band: 20, 30, 60, 100, 180, 240 Hz (boost and cut up to ±20 dB). HF boost: 5, 6, 8, 10, 12, 16 kHz (up to +20 dB, Q 0.5–10). HF cut: 6, 10, 20 kHz (up to –20 dB).
Stereo operation and mix bus / mastering applications
As a stereo module in two 500-series slots, the RB 500 ME processes both channels simultaneously with matched settings – making it a ready-to-insert stereo tool on mix buses and mastering chains without the need to buy two mono units and synchronise their positions. Passive Pultec-style correction on a stereo bus behaves differently from active or digital EQ at equivalent gain settings: HF boost at 10–16 kHz adds air without hardness, low-band boost at 30–60 Hz adds body without mud, and simultaneous boost and cut on the same or nearby frequency produces curves that linear-phase digital EQs cannot replicate. Input impedance 1 kΩ (Carnhill), output impedance 600 Ω (Edcor). Headroom: 18 dB above +4 dBu.
KEY FEATURES
- Stereo passive Pultec-style equalizer (EQP-1A), dual-slot API 500
- First stereo Pultec EQ in 500-series format
- Four audio transformers: Carnhill (inputs) + Edcor (outputs)
- Discrete Class A output stage
- Independent frequency selectors for bass boost and bass cut
- BASS band: 20 / 30 / 60 / 100 / 180 / 240 Hz (boost and cut up to ±20 dB)
- HF Boost: 5 / 6 / 8 / 10 / 12 / 16 kHz (up to +20 dB, Q 0.5–10)
- HF Cut: 6 / 10 / 20 kHz (up to –20 dB)
- ELMA switches + stepped pots – full session recall
- Hard-wire bypass
- THD+N: 0.012%, crosstalk: 75 dB
TECHNICAL SPECIFICATIONS
- Type: stereo passive equalizer (Pultec EQP-1A style), dual-slot API 500
- Input transformers: Carnhill (1 per channel)
- Output transformers: Edcor (1 per channel)
- Output stage: Class A (discrete)
- Q: 0.5–10
- Correction range: ±20 dB
- BASS (boost and cut): 20 / 30 / 60 / 100 / 180 / 240 Hz
- HF Boost: 5 / 6 / 8 / 10 / 12 / 16 kHz
- HF Cut: 6 / 10 / 20 kHz
- Input impedance: 1 kΩ (Carnhill)
- Output impedance: 600 Ω (Edcor)
- Operating level: +4 dBu
- Maximum input level: +20 dBu
- Maximum output level: +22 dBu
- Headroom: 18 dB
- SNR: –99 dBA
- THD+N: 0.012%
- Crosstalk: 75 dB
- Frequency response: 20 Hz – 20 kHz ±0.1 dB
- Hard-wire bypass: yes
- Power consumption: 7 W
