Файл: Eventide_H8000FW_UM.pdf

Sample Rate Conversion (SRC)

In general you need to make sure that any digital inputs are synchronized to the system sampling rate.

If for any reason you cannot synchronize the AES/EBU 1-4 (1-8 on H8000) or S/P DIF 1/2 digital inputs to the system sampling rate, use sample rate conversion (SRC). The sample rate

conversion pages are the "bottom" menu pages under clock in the SETUP area. By turning SRC Mode on for the appropriate digital input, the H8000FW will adjust the input sampling rate to match the system sampling rate. The sample rate before conversion is displayed in the Input SR x/x field. In this example, our internal clock rate is 48kHz. The SRCs are converting these 44.1kHz inputs to 48kHz.

The sample rate conversion algorithm is of a high quality and its presence is normally undetectable without the use of expensive test equipment. Nevertheless, the true audiophile will try to synchronize the input devices to the H8000FW without using sample rate conversion in order to achieve the best possible results.

Note that sample rate conversion is only available on the above inputs – other digital inputs need to be locked if they are used.

Word Clock Termination

Any cable has a characteristic impedance that should be matched to both the signal source and destination impedance for best results with high speed sharp edged signals such as Word Clock. This becomes more important with longer cables.

Most Word Clock signals are generated with 50 Ohm source impedance, whereas the BNC cables used to connect to them may have 50 or 75 Ohm impedances – clearly the former are to be preferred.

So, we have covered the source and the cable – what about the destination ? If we only have a single destination it is easy – the destination must also be 50 Ohm – this is ensured by the use of termination. An input will be either terminated meaning its impedance is set to 50 Ohm, or un-terminated meaning it has a high impedance that will not load the cable.

With multiple destinations only the one at the end of the cable needs to be terminated – intermediate destinations need not and should not be terminated, as long as the “stub length” of the cable to them is short. These should be connected by the use of a BNC

“T” connector or splitter attached directly to their inputs so as to 88

ensure the shortest possible stub length. Using multiple terminations is wrong, both because twice 50 Ohm in parallel gives 25 Ohms (wrong !) and also because it increases loading on the source.

H8000 and H8000A are shipped with termination in place meaning that they can be used at one end of a Word Clock cable without changes. To use them in the middle of a chain the termination should be disconnected by removing the black jumper on the motherboard directly behind the Word Clock connector.

H8000FW has no internal termination and can be used in the middle of a Word Clock cable without change. To use it at the end of a chain, external 50 Ohm termination must be applied. To do this, you will need a BNC T piece as shown above and a 50 Ohm terminator as shown on the right. These may be supplied with the H8000FW or obtained from one of many suppliers. Connect the T piece to the Word Clock input, the cable end to one side and the terminator to the other.

WORD LENGTH (BITS)

Input Word Length

As mentioned in the introduction to this section, the H8000 assumes that the signals at the digital inputs are all 24-bit. Things work out regardless of the actual word length of the input signals because, for example, the 16 bits in a 16 bit signal correspond to the 16 "most significant" bits in a 24 bit signal. The 8 "least significant" bits are left "blank," to be filled in by subsequent processing.

If, however, the device sending the H8000 digital signals supports the protocol, you can see the word length at the inputs to the H8000. Go to the format menu page in the SETUP area. The fields on the left display the input word length (16 bits, 24 bits, and two unlocked signals in this case). The H8000 user can display and change these settings on Digital channels 1-8,

while H8000A and H8000FW can only show channels 1-4.

If the input bits are unknown as in the case of an S/P DIF input, the field reads, quite logically, "unknown." If a digital input is unlocked (not valid or not connected), the field will read "**."

89

Output Word Length

The indicated output word length can be set on the right-hand side of the format menu page in the SETUP area. Your choices for output bits are: 16, 20, or 24.

Unless a special "dithering" preset is in use, this setting will not indicate the actual output word length, but may be useful for external equipment. S/PDIF outputs do not support this word length indication.

Bypassing and Muting

Sometimes you’ll find it necessary to bypass the H8000FW using the BYPASS key. A number of bypassing options exist in the

LEVELS area. There are two "levels" of bypass, system and machine. System refers to the H8000FW as a whole, whereas machine refers to each DSP.

System Bypass

The three options that exist for system bypass are:

rly bypass Uses relays to "hardwire" each input to its corresponding output, i.e., analog input 1 is connected to analog output 1, digital input 3 is connected to digital output 3, etc. This may well NOT be the same as the current routed configuration. For example, if Analog in 1 is routed to Digital out 3, this will differ from the connection when bypassed. Be aware of the following:

When the H8000FW is powered down, it is in rly bypass state.

Because relay bypass directly connects the unit following the H8000FW to that preceding it, the resulting impedance changes can cause a click or change in output level.

Because the 1/4" analog inputs have no corresponding 1/4" analog outputs, rly bypass effectively mutes those analog inputs that are mated with 1/4" plugs.

ADAT, AES11-17 and FIREWIRE are not bypassed in this state.

90

dsp bypass Makes each output of each DSP the same as its corresponding input. For example, DSP A’s output 2 will be the same as DSP A’s input 2, DSP B’s output 4 will be the same as DSP B’s input 4, etc. The routing configuration still applies.

same as setting all the OUTx Wet/Dry parameters on the [dsp A] and [dsp B] menu pages in the LEVELS area to 0%, except that the output levels cannot be changed.

If ADAT, AES11-17 etc are connected to external inputs, they will not be affected.

mute Mutes all the main outputs. If ADAT, AES11-17 etc are connected to external inputs, they will not be affected.

Put the H8000FW into system bypass mode either by placing the cursor over the system field and pressing SELECT or by pressing the BYPASS key. Once the H8000FW is in system bypass mode, the Bypass Status LEDs blink, and the bypass A and bypass B fields are no longer available.

To get the H8000FW out of system bypass mode, either place the cursor over the system field and press SELECT or press the BYPASS key.

See Remote Controlling the Bypass Functions on page 110.

Machine Bypass

The two options that exist for machine bypass are:

dsp bypass Makes each output of the bypassed DSP the same as its corresponding input. The routing configuration still applies.

This is the same as setting all the OUTx Wet/Dry parameters on the [dsp x] menu page in the LEVELS area to 0%, except that the output levels cannot be changed.

mute Mutes the outputs of the bypassed DSP. The routing configuration still applies.

Put the H8000FW into machine bypass mode by SELECTing either the bypass A field or the bypass B field. The corresponding Bypass Status LED will light when a DSP is bypassed.

To "un"-bypass a DSP, press its bypass x field again. Its corresponding Bypass Status LED will grow dark . . .

See Remote Controlling the Bypass Functions on page 110.

91

External Controllers

External controllers are inputs to the H8000FW that allow the modification of parameters from a source outside the H8000FW. These include the foot pedal jacks 1 and 2, the relay jack, and MIDI. In addition to changing parameters such as delay times, pitch shift, LFO rate, etc., in programs, the external controllers can be used to modulate "box" level parameters, such as input levels, Wet/Dry mix, and even screen contrast. (Why you would want to modulate screen contrast is not obvious, but it's nice to know you can!)

See:

Setting Up the External Controllers on page 92.

External Modulation and Trigger Menu Pages on page 96.

Remote Controlling Parameters on page 111.

In addition, external controllers can be used to advance through programs.

See Loading a Program Remotely on page 123.

Here we will discuss the "global" setup of these external controllers.

SETTING UP THE EXTERNAL CONTROLLERS

Foot Pedals 1 and 2

Each foot pedal jack accepts a stereo ("tip-ring- sleeve") 1/4" connector (see diagram below). Between the ring and sleeve is a fixed 5 volts provided by the H8000FW. The foot pedal that

is hooked up to the jack and returned between the

tip and the sleeve alters that voltage. The pedals menu page in the SETUP area allows you to

calibrate the foot pedal jacks for the particular foot pedals you are using. The "top" menu page calibrates jack 1, and the "bottom" menu page

calibrates jack 2 (just press the pedals SOFT KEY to toggle between the two). The horizontal bar graph at the top of the menu page represents the current foot pedal position relative to the calibration.

To calibrate your pedal, highlight the Calibrate parameter with the cursor and press the SELECT key. Rock your foot pedal through its full range of motion, from full minimum ("heel") to full maximum ("toe"), and then press any key. The

92

heel and toe parameters will jump to reflect their new, calibrated values. You’re done. Now, when you use that foot pedal to modulate parameters, the minimum foot pedal position will correspond to no modulation and the maximum foot pedal position will correspond to maximum modulation. If you want the opposite to occur (maximum foot pedal

position corresponding with no modulation and minimum foot pedal position corresponding with maximum modulation), simply calibrate the pedal as discussed above and then swap the heel and toe values.

Pedals to be used with the H8000 should ideally have a resistance of about 10K.

MIDI Setup

In the H8000FW, MIDI can be used:

with programs that explicitly call for MIDI signals. For example, some programs in the H8000FW act like synthesizers that a MIDI keyboard can play.

with programs that explicitly call for some sort of "external" controller. For example, the program "External Detune" calls for an external signal to adjust the amount of detune that is applied to an audio signal. You can direct a MIDI controller to do the adjusting.

To remote control any parameter in the H8000FW (including input and output levels).

To change programs via MIDI program change messages.

See Loading5 a Program Via a MIDI Program Change Message on page 124.

To advance to the next program or select the previous program.

See Triggering5 the Next or Previous Program to Load on page 127.

To synchronise the H8000FW's tempo generator to an external source by using MIDIclock.

See System Tempo on page 132.

To synchronize external equipment to the H8000FW's tempo.

There are several MIDI "global" parameters that bear on how all of the above uses of MIDI function. These parameters are found on the midi menu page in the SETUP area (you may

have to press the SETUP key a few times to find it). The midi menu page is "stacked"; the "top" menu page is shown to the right. Let’s look at each parameter in turn, shall we?

MIDI If set to disabled, all received MIDI commands are ignored. However, MIDI output messages, including parameter changes, program load, bank change, and the various dump commands, are still enabled. Set this parameter to enabled if you want to receive MIDI messages.

93