Empirical Labs EL-Rx User Manual

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DocDerr

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7501234 3.5

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Multi-purpose Tone Doctor…

6.5810115

5.2

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-5

14 14+

KKK

KHz

Mix

(Blend)

BAD!

and an Acoustic Musician’s Solution in the digital age

INDEX

Page Item

2 Using for the First Time 3 The Jumpers on the PC Board. 4-6 Example Settings of the DocDerr 7-8 Recall Sheet

10 Block Diagram & Section Details

12 Wiring the DocDerr 13 DocDerr Pet Tricks & Troubleshooting 13 Stereo Operation

Technology for the Artist

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Features

� Super low noise line input, or instrument preamp, with famous Empirical Labs

compression. Six digitally controlled analog sections of processing. Incredibly dense processing module available for the API 500 series format.

� Four sections of Equalization – One High Pass and 3 parametric bands. � Empirical Labs first compressor for the API 500 format. It is an aggressive

compressor that follows the EQ, tailored to acoustic instruments, and plucked attacks, but good on just about anything. A must try on vocals and bass!

� Complex compressor envelope generator. Fast, yet musically saturates at high gain

reduction. Program dependant release.

� Saturation circuitry that scrunches the highs and allows hotter levels like tape. Uses

filtering combined with germanium clip circuitry to soften loud high frequencies.

� Mix control to allow user to blend an un-compressed EQ’d signal back in with the

compressed saturated signal. When on 0, only the EQ’d signal is put out.

� Adapter is provided for free, allowing a guitar, bass, etc to be plugged straight into

the rear of your API powered rack.

� DC Coupled Input and Outputs. � Selectable single ended or differential output. Differential out adds 6dB gain. � Traditional and digitally controlled analog combined in new topology. � A “BAD!” Hard Clip Indicator lights – A “Bad” Clip LED that lets user know he is within

1dB of hard clipping. It monitors most every section for internal clipping.

� Highest quality Components. All metal film and Roederstein resistors in the audio

path - top quality components, most being high temperature military spec parts.

� NOTE: With all the processing, the DocDerr draws slightly more current than the API

500 spec, but has worked perfectly in all racks tested. Six have been tested in the API Lunchbox and other racks, without overloading the power supply.

� User modifiable elements, including the Compressor. Lots of future options!

Three year unlimited warranty. Built and calibrated in USA.

��

Specs

♦ Frequency Response is 3 Hz to 180 kHz on eq section (-3dB points). ♦

Dynamic Range - 120 dB from maximum output (.5%THD soft clipping) to

minimum output. Noise floor with Mix on 0 is typically – 91dBu.

♦ Distortion Ranges between .0006% and 12% at 1KHz, depending on mode

and settings.

♦

DC coupled Input and Outputs, - High quality audio caps used internally.

♦ Input Impedance is 120K Ohm, Instrument In Mode. 20K input impedance

in balanced Line in mode.

♦

Maximum Input before hard clipping - +22dBm, “ Line In” mode.

♦ Maximum Output - +28dBm (Mix = 0). Output impedance is 75 ohms.

Compressor Dynamics Time Constants - Attack time is about 1mS. Release

♦

.2 sec, program dependant, fixed internally.

♦ Power Consumption – 4 Watts max. 2 Watts typical with 16Volt power supplies.

♦ Shipping Weight - 1.3lbs.

Empirical Labs - Something Old, Something New

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What is the DocDerr?

It’s all about TONE. The DocDerr is a digitally controlled Preamp, EQ, Compressor and Saturator module good not only for general use, but can single handedly bring incredible tone to any source, even electrified acoustic instruments. It offers unprecedented amounts of processing and musicality in an API 500 compatible module. With a mini-computer inside (Microcontroller), one controls 4 analog EQ sections, and a new dynamic section capable of chopping brittle edges and digital transients with its compressor and saturation circuits. The DocDerr module is the first Empirical Labs compressor available in the API 500 series format, and a super-utilitarian processor.

DocDerr's Six Section Types:

1) Low Noise Preamp section, capable of unity, or 16dB of “instrument” gain.

2) A selectable High pass filter to cut annoying sub frequencies out.

3) Three bands of top performance parametric EQ.

4) A dynamic section that offers renowned Empirical Labs compression at an unprecedented price, in a 500 series format module. This aggressive compressor has a large “knee”, and is tuned to minimize nasty distortion. A live instrumentalist has access to classic compression.

5) A tape emulation type circuit that softens the high frequencies, and soft

clips, allowing more RMS level to fit in the same peak level. It’s louder!

6) A mixer that allows the user to blend the uncompressed EQ’s signal with

the compressed & saturated signal.

Using the DocDerr for the first time

The DocDerr is an incredibly deep and powerful little tone-enhancing module. Lets dive in. Operating Levels – First, before even installing the DocDerr in a rack, make sure the DocDerr has the input gain jumper set properly for your use. There are two primary ways to hook up the DocDerr:

1) As an instrument preamp with front-end gain, 2) As a line level device/processor. The INPUT GAIN Jumper allows you to select one of these modes and is located towards the middle rear of the board. If you are plugging a guitar or bass directly into it, for instance, it should be set towards the rear for INST mode. For louder balanced LINE IN level signals, it should be towards the front. See page 3 for a diagram of the Jumpers. The Factory default is LINE IN. (Not unity gain). In INSTRUMENT IN, the gain increases to 16dB of front end, high impedance amplification. Use INST jumper setting for an instrument such as your acoustic guitar with built in pickups. Install in your rack. If your rack has only XLR, use the supplied adapter cable to go from your guitar to the XLR input of your rack. The output can go directly to powered speakers or a mixer, etc. First time users should learn the EQ first. Turn the Compressor MIX knob to 0 (No compression, just EQ) and adjust the EQ controls till you get the creamy sound you want. Select the frequencies by pushing the buttons, and set boost and cut with the knobs. Holding a button for 1 sec will cycle backwards. There are 7 frequency selections for each band. When two LEDs light, you read the frequency below and between the two LEDs. If you hear thumps or low rumble, engage the HP circuit by pressing two buttons at once, the LF and the MF switches. You can cycle through the available high pass frequencies by repeatedly pressing these two buttons. Often the two main problem areas with acoustic instrument tone are low mids and high mids. Pulling out woofy frequencies between 250 – 500 can make the instrument sound brighter and fuller. If upper mids pop out, you can pull 1K – 8K with the midrange or high frequencies. Piezo or ceraminc pickups often have too much energy in the 4KHz area. The DocDerr compressor can help smooth out gain loss from EQ dips, making a case for touching up your EQ while compression is engaged. Now lets setup the compressor. Turn the MIX knob on the right to 10 (100% compressor) and adjust the INPUT Knob until you feel the sustain and evenness of our compression starts to please you. We worked very hard on this compressor to make it aggressive, yet not unpleasantly distort, as fast as it is. A live musician may want to maintain his really hard attacks by turning the mix back from 10, mixing in the dry uncompressed signal. This will let the really loud passages come thru over the compressed, sustained level. Live, you may have feedback problems with an acoustic instrument. This often limits the amount of compression one can put on. One can try to pull out the feedback frequencies with EQ, but often the player will have to ride his volume down at fade-outs. For line level situations, such as while mixing or on a synthesizer, one would move the Gain Jumper to the Line Level position (towards the front). This cuts the gain back by 16dB to 0 gain, 2

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and turns the input into a balanced amplifier, allowing the DocDerr to handle very hot signals without clipping, and the module becomes a great mix or line level tracking processor.

3 Pin Jumper Settings

________

S/N

Input Gain

U17

U12

13 U14

U19

Det HP Differential Out

U34

DocDerr R3

Empirical Labs

5/20 2011

2728

FBW

PreOut

16dB

Dif

50V

Line Inst +16 FBW 150Hz HP Dif out Single Ended

Above is a diagram pointing out the 3 user selectable jumpers, affecting audio and compressor detector. All jumpers are shipped in the left (front) position, which is factory default.

INPUT GAIN JUMPER - For direct instrument inputs, such as an acoustic guitar, one would set the INPUT GAIN Jumper to the right (NOT as shown). This provides 16 dB of single ended gain when input pin 3 is shorted to ground, as a normal guitar cable would do. This gain is usually enough to bring up electric instruments to line level, while still providing a margin of safety for certain active instruments. It will help the MIX control also, making the dry level closer to the compressed level, so sweeping between them won’t be so radical. For line level signals, keep jumper to the left (front).

DETECTOR HP JUMPER - This jumper allows the user to optionally roll off low frequencies going to the detector of the compressor. When in the right (rear) position, this filtering keeps the compressor from responding as much to the low frequencies, which often have great power, therefore sometimes getting over-compressed, subjectively speaking. However, since the compressor is so versatile, it’s usually preferable to tame the subs as well, by sending a full bandwidth (FBW) signal to the compressors detector (jumper to the left as shown).

DIFFERENTIAL OUT JUMPER – Changes output configuration. This jumper sets the XLR output pin 3 to either balanced ground, or the inverted phase of what’s on pin 2 of the output XLR. It is set to the left, differential mode, from the factory, adding 6 dB more gain. Setting the jumper to the right (towards the rear) disconnects the amplifier on pin 3, decreasing the output gain by 6dB.

Multi-Button Controls: Lastly, to get started you should learn three special button combinations. Pressing two buttons at once will cycle through the following parameters:

HP Frequency - Press LF and MF to change HP Frequency from Off, 70Hz, and 100Hz. Mid PEQ BW - Press MF and HF to change Mid band Q (bandwidth). LED indicates narrow Q. Disable Compressor - Press LF and HF to disable/enable compressor.

Disabling the compression can be done with software by pushing the LF and HF buttons simultaneously, allowing the DocDerr to behave almost as a tape-like saturation/distortion box. A Det HP jumper on the PCB can make the compressor respond less to low sub frequencies. The DocDerr is shipped in FBW (full bandwidth) mode, with the jumper towards the front, which is usually preferable, especially bass instruments. Moving the DET HP jumper to the rear position rolls off below 150Hz to the compressor detector, and can help prevent LF pumping for midrange sources like vocals and acoustic instruments. It is sometimes useful for buss compression as well. The HP EQ filter often prevents pumping also, as it filters out subs in the audio path before the compressor sees them. See P3.

The Saturator

The saturation circuit follows the compressor, and tends to catch high frequency peaks that get through, softly flattening them out. It was largely tailored to simulate the characteristics of tape saturation. Germanium semiconductors are used to more smoothly round the peaks to produce lower order harmonics. We use special filter circuits to shape how different frequencies are soft clipped. This saturator circuit is always in the path of the compressor signal. When the mix control is set to 0 (dry), the saturator and compressor are both out of the path and do not affect the output signal. The saturator will add lots of harmonics to low frequencies, and soften high frequencies. As mentioned above, pressing the LF and HF buttons will toggle the compressor off and on, allowing you to use just the germanium saturation circuit with no compression. Very tape-like!

The Mix Control

This is a clean mixing circuit that allows the user to blend the EQ’d uncompressed signal with the EQ’d, compressed and saturated signal, and has incredible phase alignment through 20KHz. This simple circuit gives the user incredible flexibility in how the compressor/saturator is used. As already mentioned, the user can sometimes put lots of compression on a signal, and mix it back under the dry signal and get a natural full sound, with dynamics, and lots of sustain. There will be a slight level drop in the middle of the Mix knob range, partially because the compressed signal sustains notes tremendously, but the uncompressed peaks are attenuated. Once you back down from 10 on the Mix, the loud sustained level will drop quickly, but you may have a very nice natural dynamic sound. Conversely, you will also notice a quick change in the loudness and sustain, when you nudge the mix control above 0. The mix control is heavily dependant on the input signal’s level. There are lots of marks on the Mix control to aid in recalling settings, especially between 8 - 10.

Wiring the DocDerr

There are two main ways to setup and wire the input of a rack with the DocDerr module installed.

1) “Instrument In” with a single ended input (usually a mono standard guitar cable) and 16dB of gain,

2) “Line In” which is lower gain and can be differential.

There is an INPUT GAIN jumper located in the middle rear of the board that can be switched between two positions, Instrument In (Inst) and Line In. This jumper changes the mode which the input amplifier works, changing it from a high impedance amplifier with gain, to a lower impedance differential input amplifier with no gain. So before installing your module, set this jumper to the proper position. Most API 500 compatible racks do NOT have a 1/4” guitar jack input, so we supply a female 1/4” jack adapter that goes to male XLR. Plugging a standard guitar cable into this adapter will work perfectly for “Instrument In” mode. The guitar cable will short the sleeve to ring, shorting the ring (pin 3 on the XLR) to ground. When the Input Gain jumper is set to the rear in “INSTRUMENT IN” mode, this will result in a very clean 16dB of high impedance gain. As shipped from factory, the output is balanced differential, and 6dB louder than the alternate single ended output setting. The single ended mode, with the jumper to the rear, has balanced impedance, which can prevent any output wiring problems (See P3). For recording you will usually use the balanced differential mode as it has 6dB more gain and will hit the recorder with a better signal. If too loud, use single ended mode. When using the differential out mode, don’t short any of the Active XLR output pins (usually Pin 3) to ground. Let the unused pin 3 “float” (stay unconnected). Separate amplifier drives each of these pins, so grounding one of them will short the associated amplifier out. So in the Dif Out mode, if you only use pin 2 on your output cable, leave pin 3 unconnected. When going to a single ended patch bay or other device, using the single ended jumper setting (jumper towards rear) will work just fine, and take some guesswork out of wiring.

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Example Settings

The DocDerr provides a new level of processing power in a single API 500 module. Originally the main target user was the live performer who traditionally has a thin, out-of-control sound from his/her guitar or other acoustic instrument. But like most Empirical Labs products, the versatility of the DocDerr makes it useful on practically any source. Also, because of the no-compromise build quality of the DocDerr, it is an excellent studio processor/preamp as well. We will start our example settings on Acoustic guitar, especially those with built in pickups.

Acoustic Guitar & Plucked Instruments – Acoustic instruments are extremely

sensitive to tone alteration. Mic selection and placement, along with a good instrument is your first resource during performing or tracking. It’s always best to try getting the source to sound right WITHOUT Processing. A good player should also be sensitive to the sound he gets off the instrument, and adjust how and where he hits the strings. However, we have stuffed enough processing into this little module that combined with the eq on the instrument, you should be able to get a first class sound, even with an instrument that has poor basic tone. If you are tracking (recording the source for the first time), the user will find endless ways to alter the tone with the DocDerr. The output level can be adjusted up or down 6dB for recording with the output jumper. Lets look at acoustic instruments with built in pickups, since they are the most common for live performances. Internal pickups are very non-ideal transducers. First they are usually partially, or

completely inside the instruments, some place your ear never is. They pick up hardly any “wood” of

an acoustic instrument. Secondly, the transducers have a frequency response all over the place, and

the best a designer can hope for is a transducer’s frequency response to compliment the instruments. Often the guitar designer will provide basic EQ for the built in transducer to help

improve the basic tone. The DocDerr’s built in EQ will enable the user to work on frequencies in a way not possible with the built in instruments tone controls. Combining both the instrument’s onboard eq with the DocDerr’s 4 section EQ gives the instrumentalist great tone shaping power. The EQ selection and the compressor was tailored for “electrified” acoustic instruments. The most common problems are midrange frequencies that pop out during different types of playing, and over dynamic instruments without sustain. The compressor fixes the over-dynamics and lack of sustain and “size”, while the EQ can do wonders for the basic tone. The player & engineer will find that often what works for a solo instrument can be disastrous on an instrument in the mix with other instruments. Low frequency Boominess, a common problem, can be fixed with a gentle bass roll off using the Low PEQ, or with the steeper high pass sections. Again, while mixing, its best to EQ the instrument “in the mix” to make it fit tonally. While soloing, there is often a tendency to thicken it up, which will translate to muddiness when combined with the bass and other instruments. The high pass filter is EXTREMELY useful to open up frequencies below 120Hz for other instruments. The 70Hz filter will leave all the fundamental frequencies of an acoustic guitar intact, but get rid of thumps and low frequency body rumbling. It is especially useful for the solo guitarist who wants a BIG sound, without rumble. The 100Hz filter is still out of the way of most fundamentals, but cuts down on the size of the guitar sound, making it useful in ensemble playing. On records, when an acoustic is part of a band, engineers will often cut higher frequencies up around 120 – 150, preventing “muddy” sounding mixes. One can use the LF parametric section alone, or combined with the HP to achieve this with the DocDerr. The tone and body of an acoustic guitar is in the 160 to 500Hz range. Too much in this range and the instrument sounds dark and “wooly”, while too little can make it thin. Sometimes it’s necessary to boost AND cut at close frequencies down here. Get used to the drop in level when you cut frequencies in this range. Sometimes cutting one mid frequency generously can fix a whole guitar tone, yet its easy to get fooled when A/Bing it with the orignal. Eq’ing with the compressor can prevent the misleading level drop. One can use the midrange with narrow Q (press MF and HF buttons to narrow this Q or bandwidth), to surgically pull 500Hz or higher frequencies out. 400 – 1KHz is often a good point to cut frequencies to brighten and fill the lows and highs. It is above most fundamental frequencies, but below the frequencies that help the instrument cut thru in a mix. Many guitars have honky midrange in the 1 – 8KHz range, especially when the player is playing hard (loud). Try pulling 6dB at 1-4KHz with the midrange EQ, wide bandwidth, and see if that makes the guitar rounder. If this sounds dull, try moving the frequency lower (1KHz?), or perhaps you need to pull a couple different points at say 1Khz and 4-8Khz. Sometimes pulling as high as 10Khz will smooth the tone without dulling. The upper midrange on acoustic instruments changes drastically depending on how the instrument is played, and even if the guitar part uses open strings, or finger fretted strings. Eq’ing an acoustic instrument with a pickup is a series of compromises. Don’t forget to use the tone controls on the instrument itself, for more eq power.

+ 9 hidden pages

Empirical Labs EL-Rx User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual