The SSL Alpha Channel not only provides a combination of mic preamp, filter, EQ, dynamics, and A/D conversion to provide an affordable analog channel strip with SSL signature sonics, it offers DAW-friendly features that go far beyond those of standard channel strips
To the casual observer, one would think that the Alpha Channel is just another rackmount channel strip with preamp, EQ, and compressor/limiter (though coming from SSL, that’s still pretty extraordinary). However, it’s actually much more than that. Not only does it give you a professional-level SSL channel, but it also functions as a versatile front-end for your DAW, with a quite a few very useful tricks up its sleeve, including zero-latency analog monitoring and the ability to record two mono channels; one at nominal level, the other clean at 12dB down as a safety backup for moments of distortion in an otherwise great take. It can also treat mic sources with SSL’s Variable Harmonic Distortion (VHD) for analog character, along with EQ, and compression, plus additional processing via its insert. Or, if you want a clean signal going in, you can use the Alpha Channel as a mix processor in both series and parallel. Alpha Channel offers the most affordable and versatile entry to SSL sonics and innovation.
Solid State Logic Alpha Channel—Just the Facts
- Professional ultra-clean mic preamp with Hi-Z impedance switch
- VHD (Variable Harmonic Drive) circuit for added analog character
- Front-panel Combi XLR mic/line/instrument input
- 1/4" jack instrument autosensing with passive DI type impedance detection and level matching
- High-pass filter with selectable 40Hz, 80Hz, or 120Hz cutoff
- DC Sidechain Link outputs (RCA)
- Built-in professional quality analog to digital conversion
- 1/4" analog out and S/PDIF I/O
- Auto sample-rate sensing and self-adjustment
- Three-band SSL parametric EQ with mid-frequency Q control and dual LF curves
- Intelligent auto limiting that maximizes recording headroom and avoids DAC clipping
SSL Alpha Channel—Under the Hood
The Alpha Channel sports a sophisticated and versatile collection of features particularly at its price point. It features a high-quality VHD mic pre (like those found in the flagship Duality console) with switchable impedance for instrument or line sources. Along with Variable Harmonic Distortion (VHD) for dialing in second and third-order harmonics (tube/tape), it has all the usual suspects in a channel strip line-up, including phantom power, phase reverse, an Insert for additional processing, a 3-band EQ featuring the classic SSL channel-strip EQ sound with selectable Bell curve for the low frequencies, high-pass filter with 40/80/120Hz cutoff frequency selection, switched “lite” limiter to prevent digital clipping, high-quality analog to digital converter, and an S/PDIF digital output.
Alpha Channel DAW applications
Analog recording and monitoring
The Alpha channel provides a feature which allows one output for the recording send and another for monitoring, enabling zero-latency monitoring by simultaneously using the Line Output and Insert Send jacks. This provides the added advantage of hearing the signal before it’s recorded. For comfort effects during vocals, the Alpha Channel’s converters are bypassed.
The Alpha Channel will presume it’s the master sync source unless an S/PDIF signal is connected to its S/PDIF input. If presented with a clocked S/PDIF signal the Alpha Channel will automatically slave to this clock source.
If the Alpha Channel receives a sync reference it will lock to the incoming sync frequency (range 32Khz-108Khz) and its sync output will follow the input sync’s reference frequency.
Using the S/PDIF output to record two signals
The Alpha Channel’s S/PDIF output can be used beyond simply passing a stereo output signal. Its left output channel carries the same signal (after A/D conversion) as the analog output. If you select the left channel of the S/PDIF input on the audio interface in your DAW you’ll record exactly what you are hearing.
However, and this is where it gets interesting, if you select the right input on your audio interface, the signal that comes from the Alpha Channel is taken pre-insert, post filters. This means it will have no EQ, insert, or limiter. More significantly, it’s a slightly cleaner, unprocessed signal that’s also -12db below the left channel.
PAD Recording Tip: Audio luminary George Massenburg, producer, engineer, and inventor of parametric EQ, does not like to record vocals with compression. Compressors can increase noise, emphasize certain frequencies, add artifacts, etc. His preference for recording vocals is to split a mic signal into two identical preamps (he deals with the impedance loading the mic later on) with one set -15dB lower. Since each channel sees the same microphone, there’s no difference in sound between the channels. This way, you can track a vocalist with a wildly dynamic range without compression or worrying about spoiling a great take when riding faders (which can’t be done with digital control surfaces). Or, if the singer gets up close on the mic and belts (or screams) distorting the 0dB output channel, you just comp in the -15dB safety track, normalized levels, and Bob’s your uncle.
As you can see, the Alpha channel enables you to use Massenburg’s vocal recording technique with a single preamp, no impedance issues. However, if you’d like to record with compression, you can do so with the built-in limiter to avoid peaks or use the Alpha Channel’s insert.
Using Alpha Channel VHD (Variable Harmonic Distortion)
The ability to add harmonic distortion to taste is made possible by SSL’s Variable Harmonic Drive (VHD) circuit. As you increase the input gain, the Variable Harmonic Drive circuit introduces either 2nd- or 3rd-order harmonic distortion. At lower gain settings it adds gentle tube-style warmth or a touch of transistor edge—great for sounds you want forward in a mix without having to take up headroom using EQ. As the gain is increased, distortion becomes more extreme until at high-gain settings it delivers fierce trashy transistor grunge.
The VHD circuit is integral to the preamp, but usually only becomes noticeable when the knob is in the last quarter of its travel. This allows the pre-amp to be used in the normal manner (without distortion!) for most of its range and the distortion characteristics to be brought into play at higher gain settings.
The level of the incoming signal will also have an effect on the VHD circuit, as will the Pad button, which offers 20db of gain reduction for loud signals. The second knob in the input section labeled 0-11 changes the character of the distortion from 2nd-order harmonics to 3rd-order harmonics. This will only have an effect at high gain settings.
The VHD control has a far more noticeable effect at higher gain settings. As such, the input gain should be used in combination with the VHD control to affect the amount of distortion being added to the input signal. In case you get carried away, the Pad button will glow red when the input stage is starting to overload; the VHD circuit is designed with this as part of normal operation, though it should be avoided for a cleaner signal.
An overdriven preamp will have an effect on the gain of all subsequent units in a signal chain. Therefore, you may need to reduce output gain interface correctly with other equipment. You may find that the output gain will need to be taken down to interface correctly with other equipment, or you could engage the Lite Limit here to stop the A/D converters overloading if using the digital output.
The Alpha Channel lets you sum a processed signal with an unprocessed one, which as you may already know is called parallel processing. It allows you to apply extreme processing but still retain the dynamic and character of the original signal. The Alpha Channel provides an easy way to achieve parallel processing right in the box, without having to set up an aux send/return. If the Sum button is depressed while using a compressor in the send/return loop, the unprocessed signal will be added to the compressed. The output gain of the compressor can then be used to balance the two.
Any two or more Alpha Channels have the ability to be linked together. The two phono connections above the S/PDIF sockets labeled “Link” provide access to the side-chain of the Lite Limit circuit. By simply connecting a phono cable between two Alpha Channels via the link jacks, the Lite Limit on each unit will work in conjunction with each other. Multiple units can have their side-chains linked in this manner.
The SSL Alpha Channel is the most affordable way to add SSL console sonics and features to your DAW. Order yours today. For more information, call or chat online with your PAD Studio Specialist today.
- Power: IEC320 3-pin connector, 100 – 240 VAC, 50 – 60Hz
- Microphone: Balanced, 3-pin XLR-F, Z-in = 1k ohm (10k ohm for Hi-Z)
- Instrument: Un-balanced, 1/4" mono jack, Z-in = 1M ohm
- Output: Balanced, 1/4" stereo jack, Z-out = 40 ohm
- Insert send: Balanced, 1/4" stereo jack, Z-out = 40 ohm
- Insert return: Balanced, 1/4" stereo jack, Z-in = 10k ohm
- Link (2 of): RCA phono, limiter sidechain control voltage (DC.)
- SPDIF in: RCA phono, 1V pk-pk, Z-in = 75 ohm, SPDIF format (ADC will lock to this signal if present)
- SPDIF out: RCA phono, 1V pk-pk, Z-out = 75 ohm, SPDIF 24-bit format (Synchronized to SPDIF In, else free-runs at 44.1kHz)
- Mic gain to output: 20dB min, 76 dB max
- Instrument gain to output: 26dB min, 82dB max
- Pad Attenuation: 20dB
Input impedance (ohms):
- Mic: 1k/10k
- Instrument: 1M
- Equivalent Ein: Mic, Z-in = 10R: -130.5dBU; Mic, Z-in =150R: -127.5dBU
- Dynamic Range: Mic Gain Min: 105dB un-weighted; Mic Gain Max: 76dB un-weighted
- Common Mode Rejection: 70dB from 50Hz to 10KHz with 1Vp-p Common Mode
- Max Common Mode In: 5V p-p
- Mic To Out: +/- 0.2 dB from 10Hz to 70KHz
- -3dB (LF): 6Hz
- -3dB (HF): 250kHz
Mic Amp Distortion - A Typical Specification
- Output Level: THD Knob CCW THD Knob CW
+5 dBU 0.03% 0.1%
+10 dBU 0.05% 0.3%
+15 dBU 0.06% 0.5%
+20 dBU 0.09% 2%
+24 dBU 0.15% 5%
Maximum analog output
- +24.3dBU (10k)
- LF Shelf Gain Range: +/- 19dB
- LF Bell Gain Range: +/- 15dB
- Shelf Freq Range: 40 - 600Hz
- Bell Freq Range: 35 - 500Hz
- Bell Q: 1.4
- Gain range: +/- 17dB
- range: 300 – 5.2kHz
- Q Range: 0.7 - 1.9
- Shelf gain range: +/- 19dB
- Shelf freq. range: 1.5kHz – 22kHz
EQ Dynamic Range: 100dBU
- Threshold: - 3dBFS
- Ratio: 6, over-easy
- Headroom: 12dB min, 14dB typical
- Attack Time: 50uSec
- Release Time: 200mSec
- Limiting Distortion: 5% max
- Non-Limiting Distortion: 0.001 %
- Limiter Switch Out: 24dBU, unity gain to output
- Limiter Switch In: 12dBU, +12dB gain to output
- Send: 150 ohm
- Return: 10k ohm
- ADC Type: 24-bit, 192KHz CS5361 ADC
Sampling rate (locks to user supplied SPDIF in):
- Range: 32kHz to 108kHz
- No SPDIF In: Defaults to 44.1kHz
- SPDIF In: 200 mV p-p IN min; 5V p-p IN max
- SPDIF Out: 1V p-p (level); 60 ohm (impedance)
ADC Performance Measured From Insert Return:
Dynamic Range, 20k Hz measurement bandwidth
- Fs= 32K: 110.5dB, A-wgt
- Fs= 48K: 110dB, A-wgt
- Fs= 96k: 109dB, A-wgt
ADC Distortion, 1kHz test tone:
Level Distortion in 20k meas bw
-0.5dBFS 0.0006 %
-10dBFS 0.0015 %
-20dBFS 0.004 %
-30dBFS 0.013 %
-40dBFS 0.04 %
ADC Freq. Response
- Fs = 48k: +/- 0.1 dB, 20Hz – 20kHz
- Fs = 96k: +/- 0.1 dB, 20Hz – 40kHz
- Phantom Power: 47.5V typical
- Output Gain Range: +/- 19.5dB
- Height: 1-1/4" / 44.5mm (1 RU)
- Width: 19" / 482mm with rack ears; 17-1/4" / 438mm casing only
- Depth 9" / 230mm (casing only)
- Weight: 7 lb. / 3.0kg
- Power: < 20 Watts