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MCI JH600 Series Frequently Asked Questions

MCI JH600 Series consoles are all in-line consoles, which means the number of input modules are the actual number of line returns. There are three models: JH618, which is capable of holding 18 input modules, either mono or stereo, that are used primarily in broadcast situations (i.e. radio or television stations), JH636, capable of holding up to 36 mono or stereo modules (stereo modules do not have mic pre-amps), and JH652, which has 52 input modules (26 modules to the left, 26 to the right, and a master section for both in the center; the patchbay was internally mounted in the frame and contained patch points for all 52 inputs, plus the master section, etc.).

JH600 Series meter options:  There are two types of metering on either the JH636 or the JH652.  Standard VU meters with VU ballistics or 100 segment light meters that are vacuum florescent (not lightbulbs). The LM meters read either peak ballistics or DC level for the automated faders.  Peak reading meters are usually 12db above VU meters reading at 0. The JH618 series only came with VU meters. A phase meter was an option on all three variations of the JH600 series.

JH600 Series fader packs included:
  1. Non-automated mono fader, with a Waters or P&G fader and an illuminated mute switch.

  2. Automated fader (AF), used with JH50 (tape-based automation).

  3. Group Only fader (GO), which allows you to have 4 VCA groups, group muting, and solo.

Retrofit automation systems, either Optifile or other systems, require VCA automation fader packs, so either GO or AF fader packs are required. Note that each of the three fader packs has a different wiring harness that goes to the motherboard of each module.

There are three different types of input modules. Consoles built in 1979-'80 had the first series 0112 modules. The early '80s (approx. '81-'82) consoles had 0136 modules. Both of these have a rectangular button at the bottom of each input module that says VCA (black button with white letters). This button switches the VCA of the module between the rotary fader and the linear monitor fader. The last version are the 4030 modules, which have a black rectangular button with white letters that say REV, as well as two black cone buttons that say BUS and VCA, and the stereo pan pot is center detented, as are some EQ level pots.

The 0112 modules came standard with three-band EQ (low-band is +/- 14 db from 30 Hz to 250 Hz, mid-band is +/- 14db from 180 Hz to 10 khz, high-band is +/- 14 db from 4.6 kHz to 16 kHz, as well as a high pass and low pass filter, and an in/out switch, and can be switched between the channel and the monitor section of the input module). The 0136 and 4030 modules both came standard from the factory with the same EQ specifications as above, however, there were two other EQ options available on these modules. One is the Quasi-parametric (low-band is +/- 14db from 30 Hz to 250 Hz, with a peak or shelf characteristic and two position selectable Q, mid-band is +/- 14 db from 180 Hz to 10 kHz, with a variable Q from .3 to 3, high-band is +/- 14 db at 4.6 kHz to 16 kHz, with a two position Q selection, and a peak or shelf switch). The other is the highly sought-after TROISI EQ modules that were available second sourced and have three-band EQ (low-band is 12 db to +15 db from 31 Hz to 1 kHz, with a peak or shelf switch, mid-band is 12 db to +15 db from 62 Hz to 8000 Hz, with variable Q concentric shaft on the frequency, high-band is 12 db to +15 db from 500 Hz to 16,000 Hz, with the Q select concentric with the frequency select pot, a peak or shelf switch, and fixed high and low pass filters, as well as a variable filter 31 Hz to 16,000 kHz). The easy way to determine whether an EQ is standard or parametric is that there are three green knobs on the mid EQ section vs. two green knobs on the standard EQ.

In reference to interchangeability between 0112s, 0136s and 4030s (with standard or either of the two parametric options): all three modules are interchangeable with each other in either of the JH618 frames or the JH636 frames. There were slight circuit changes between the 0112, and the 0136 modules, but nothing drastic. The difference between the 4030 input modules and the other two is that there's an additional op amp that has to do with the channel summing. If you have a console with a mixture of 0136, 0112, and 4030 modules, its best to have the majority of one type placed in the 1-24 section of the console. There is between 3 to 6 db of gain on the ACN circuit on the 4030 modules, so if you were bussing signals between different modules the gain would be slightly different.

Normally the MCI JH600 Series consoles had differential active balanced input and output circuits (no transformer coupling). The mic pre-amplifiers were differential active balanced, also stock from the factory. There are several second source manufacturers who make plug-in mic pre's, one of which is the John Hardy Company based in Illinois. Several mic pres are transformer balanced using several different brands of transformers.

There were various other options on the JH600 Series consoles, one of which relates to the standard number of tie lines, optional 6 send meters, phase meter, and the expensive option from the factory of mic patching, which allowed you to switch microphone lines directly from the patch bay of the console without having to go into the studio to re-patch microphone lines. The only other significant option was phantom power (+48 Volts) needed for condenser microphones.

All JH600 Series consoles interface to the outside world via 30 pin male tuchel connectors (female tuchels are panel mounted on the frame of the console)

With regards to upgrading short loaded MCI JH636 consoles on consoles using non-automated faders, its just a matter of adding these items.

  1. An input module, either 0112, 0136, or 4030, standard EQ or parametric.

  2. A Non-automated, AF, or GO fader pack.

  3. If required, a fader harness that connects the actual fader pack to the motherboard where the module plugs in. If non-auto faders are not available, GO faders can be modified to work in a non-automated console. The fader packs wont look physically the same, but can be made to function correctly. Standard (unmodified) GO fader packs will only work on originally GO configured consoles shipped from the factory.

With regards to automated JH600 consoles, each automated console has a processor board and one digitizer board per 16 channels.  In other words, a 32-input console that has 2 digitizer boards will not accept any more AF packs without adding a third digitizer board, which will handle up to 16 channels. This could be channels 33, 34, 35, 36, plus up to 12 auto-fader packs used for wild VCA faders or VCA returns. On a console with only 32 modules currently and no third digitizer board, the only two options are a non-auto fader pack with a non-auto fader pack harness, or a GO fader pack modified to work as a non-auto fader, as well as a GO fader harness.