Stam Audio 25609+ Stereo or Dual Mono Compression & Limiting

The ultimate mixbuss and drumbuss compressor. The iconic 33609 and 2500 finally merged into a single unit.

When we asked our clients what their all-time favorite mix buss and drum buss compressor was, two units came up on top; the vintage Neve 33609 and the original API 2500. So, we took the best of both and fused them into one new unit: the 25609. The sonic results are nothing short of amazing!

The 25609 retains the side chain of the 33609, as well as its Carnhill input and interstage transformers while replacing the BA-440 op-amps with the 2520’s as well as the Carnhill output transformers with two US-Made steel AP2503 replicas. This resulted in an extremely punchy and mid-forward compressor, without losing the beautiful time constants, side-chain character and huge low end of the 33609

The circuit

On the input and side chain you will find the same circuit as the the “Metal Knob” compressor, the 33609 utilized a diode-bridge based topology, and spawned several revisions since its inception in 1969. Our 25609 strictly follows the original schematic with quality stepped controls that allow for easy recall of settings and, when used for mastering duties provided a higher degree of precision.

The 25609 offers transparent compression with its lowest 1.5:1 ratio setting, or can be slammed up to 6:1 to get as much attitude as you desire. Its uses are not limited to the master bus. The original was commonly used on drums, vocals, pianos, and other acoustic instruments due to its ability to tame even the most complex source, and the 25609 replicates this perfectly with the added punch that the API 2500 is known for.

Super Slow Attack MOD

The 25609 was designed to overcome the original 33609 limitations. By adding some critical new features this unit is far more versatile in the modern studio workflow. A major complaint was it was too fast with a fixed attacked time of 5ms it was excellent on subtle mixbus duties but was never optimal for heavier or modern music, so we added our famous Super Slow MOD with an attack time of 20ms making it ideal for drums, rock music and heavy bass mixbus duties. Another shortcoming was that it was too slow to use on more percussive sources. To overcome this limitation, we added a fast attack time of 2ms to handle loud sources such as snares and kicks which is the same found on the current 33609 “N” revision

Enhanced Functionality

The 25609 also comes with a three-position side chain high pass filter as well as a transparent mix blend control. Just like the original it offers a transparent compression with its lowest 1.5:1 ratio setting or can be slammed up to 6:1 to get as much attitude as you desire. Its uses are not limited to the master bus. The original was commonly used on drums, vocals, pianos, and other acoustic instruments due to its ability to tame even the most complex source, and the SA-609 MK3 replicates this perfectly. High quality stepped controls allow for easy recall of settings and, when used for mastering duties provided a higher degree of precision. Overall compression is displayed by the front panel with vu meters. Each compression channel has threshold, release, makeup-gain, and ratio controls. The makeup-gain circuit is great for adding a little more grit and warmth to any source and can be used even if no compression is required. Each channel is also equipped with a brick-wall limiter that has threshold and recovery controls, which is placed after the compression circuit. If you wish, the limiter can be bypassed completely for applications where limiting is not necessary. For complete flexibility, the SA-609 MK3 can be used in linked stereo mode, or the channels can be separated for use as a dual mono compressor. Dual mono mode is ideal for a mix that has a lot of dynamics between the right and left channels.

Overall compression is displayed by the front panel with vu meters. Each compression channel has threshold, release, makeup-gain, and ratio controls. The makeup-gain circuit is great for adding a little more grit and warmth to any source, and can be used even if no compression is required. Each channel is also equipped with a brick-wall limiter that has threshold and recovery controls, which is placed after the compression circuit. If you wish, the limiter can be bypassed completely for applications where limiting is not necessary.

For complete flexibility, the 25609 can be used in linked stereo mode, or the channels can be separated for use as a dual mono compressor. Dual mono mode is ideal for a mix that has a lot of dynamics between the right and left channels.

Technical Specs

• Carnhill input transformers
• Carnhill interstage transformers
• US-made otuput transformers
• 33609 side-chain circuit
• 2500 Class A/B amplifier with 2520 op-amps
• Vishay Capacitors
• Precision Metal Film resistors
• Ratios: 1.5:1, 2:1, 3:1, 4:1, 6
• Attack Time: 5 ms (compressor), slow 20 ms, fast 2 ms
• High-pass filter
• Release times : 100 ms – 400 ms, 800 ms, 1.5 s, Auto 1 (100 ms to 2 seconds) and Auto 2 (50 ms to 5 seconds)
• Premium Vishay/Phillips capacitors
• Sifam Knobs
• Less than 0.5% THD
• Dry-Wet blend control
• XLR Inputs
• XLR Outputs
• Voltage switch selector (115V or 230V)
• Internal toroidal transformer
• Hand-made in Chile
• 2-year warranty