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LACHAPELL AUDIO 983S
LACHAPELL AUDIO 983S
2 Channel tube mic pre and instrument preamp
MSRP: $2250

This two channel tube preamp brings LaChapell Audio quality to a single rack space. The Model 983S is a high quality tube preamplifier that integrates many of the key features that distinguish LaChapell Audio gear in a package developed for personal and professional studios as well as live sound applications.

In addition to the low profile single rack space design, the 983S has an ultra-low output impedance for unparalleled sound transfer across long cable runs such as are common in theaters and remote systems. You will find many of the features you expect from a piece of LaChapell Audio gear, including: Input and Output knobs to dial in the perfect balance of warmth and definition for any application.

LaChapell Audio 983S two channel tube mic pre rack unit front image
  • Two channels
  • Dual Drive INPUT and OUTPUT knobs
  • Gain LEDs
  • Ultra low output impedance
  • Independent HPF and LPF
  • Hi-Z input
Lachapell Audio dual drive icon
Dual Drive Knobs

The Dual Drive knobs on the 983S mic pre provide an incredible array of tonal options. The input knob drives the input to the first vacuum tube and the second knob drives the input to the output tube. Together, you can dial in sounds from pristine to warm and harmonically rich.

Lachapell audio pad icon
Pad switch for more tonal options

The pad switch not only provides a -20dB gain reduction for high input sources, it also works with the Dual Drive knobs to create color and headroom options. Engage the pad and dial in warm tones with lots of headroom.

lachapell audio hi-z input icon
Autoswitching front panel Hi-Z input

The front panel Hi-Z input allows you to plug a bass or other instrument directly into the 983S. As an instrument front end, the 983S allows for natural tube compression and harmonics to any input source.

lachapell audio best in class icon
Best In Class Performance

Everything in the 983S mic pre is designed to be best in class. Every component, transformer, wire and tube has been meticulously selected for performance and longevity.

Lachapell audio HPF icon
High and Low Pass Filters

Independent High and Low Pass Filters maximize control over your recorded or live signal.

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Extremely low output impedance

The ultra low output impedance of the 982S mic pre means you can run long cables from the stage to front of house or from studio room to studio room.

983S SPECIFICATIONS
INTERNAL GAIN0 to >72dB
THD+N0.10% (minimum)
FREQUENCY RESPONSE10Hz to 50KHz
MAX OUTPUT (1% THD+N)+26dBu
TYPICAL EIN-121dBu
INPUT IMPEDANCE1.5KΩ
TUBE COMPLIMENT1 x 12AX7 / ECC83
Lachapell Audio 983s two channel rack mount tube microphone preamp (mic preamplifier) Example 1

CLEAN GAIN, HIGH HEADROOM

With the Dual Drive knobs set at INPUT around 25% and the OUTPUT around 75% with the PAD off, you will get a very clean and pristine sound. The distortion is very low with no added harmonics and there is a ton of headroom. This is a great starting position for those wanting a clean tube sound regardless of the microphone type.

Lachapell Audio 983s two channel rack mount tube microphone preamp (mic preamplifier) Example 2

TUBE HARMONICS AND COMPRESSION

With the Dual Drive knobs set to INPUT 75% and OUTPUT 25% with the PAD off, you will get tube harmonics and natural tube compression.  This is a  great place to start when using ribbon or dynamic mics that need a little harmonic color.

Lachapell Audio 983s two channel rack mount tube microphone preamp (mic preamplifier) Example 3

HEADROOM AND WARMTH

The 983S provides great sonic versatility. With the -20 dB pad engaged and the INPUT set to around 50% you will hear a rich roundness and warmth. With these settings the mid-range will move forward and the input headroom is increased as well.

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FREQUENTLY ASKED QUESTIONS

983S

Extra venting isn’t required but it is recommended, especially in warmer environments such as outside venues in the sun.

Yes. But we recommend using the -20 db pad or be comfortable with only rotating the input knob to about 9 o’clock max. With high output mics it is a good idea to start with the input knob at 9 o’clock and the use the output control to achieve line level. From there you can play with coloration and harmonics. Be aware that with high output mics, the preamp is already starting with a very large signal. It is not going to require much INPUT gain to generate harmonics and even distortion. But, then again, that might be what you’re after!

All LaChapell Audio products feature a 2 year warranty on parts and labor for issues relating to manufacturing. The tubes have a 6 month warranty. Please see the Digital Audio Labs Warranty page for more information.

The 583 and 983 are the same preamplifier and use one 12AX7 per channel.

TIP: When selecting different tubes for different sounds, use the -20 pad technique mentioned earlier. Engaging the pad and using Input gain to compensate will feature the 12AX7’s character and allow you to hear the differences between tubes much more than if the input transformer was part of the signal.

Yes. The manual will provide guidelines in this regard. The 2-bay 583’s (583E and the original 583S) have square openings that are intentionally designed to allow users access to the 12AX7 and replace with other like tubes for additional flexibility. Generally speaking, it’s the input tubes (the 12AX7s or 12DW7s) that would be replaced if you are looking to alter the sound of the amplifier. The 992’s output tubes require a critical balancing step so, for that reason we don’t recommend messing with these. In any case, if there’s ever a question related to swapping out tubes PLEASE give us a call.

LaChapell Audio has been incredibly fortunate in having a great user base. We’ve had folks like Brad Paisley, Hans Zimmer, Phil Keggy, Depeche Mode and other personally choose our preamps over others for critical productions. Many studios in Nashville, LA and the rest of the world rely on LaChapell Audio to track the sound they want.

The 983 & 583 preamps currently use the Cinemag CMMI-10PCA microphone input transformer and a Jensen JT-11-DM line output transformer. The Hi-Z input on the 983/583 amps is transformer-less.

First, it provides for the basic need to attenuate the input signal for “hot” or loud sources. For example, there are some microphones out there that generate such a large signal that a pad is required in order to prevent unwanted distortion.

The second reason is for sonic shaping. All LaChapell Audio preamps place the -20dB pad function in such a way that, when engaged, the gain contribution from the input transformer is effectively eliminated. When that loss of gain is made up by dialing in INPUT gain, the user has essentially traded transformer gain with vacuum tube gain. As a result, the distortion is different, the frequency response is different, etc. User who use this this technique express hearing more “air” and “depth” to the sound. It’s not always preferred but it demonstrates the preamps sonic flexibility. A couple areas where this technique is routinely used are drum overheads and stereo piano overheads.

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