ICOM IC7300 et HEIL PR781

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ICOM IC7300 et HEIL PR781

Message  F5PBG le Jeu 28 Juil - 0:57

Vous trouverez de nombreux avis toujours subjectifs concernant les microphones à placer sur l' IC7300.
Alors en voici un de plus... Le mien... Personnellement, je ne connais pas de microphone dans la gamme de
prix du HEIL PR781 qui donne une modulation aussi fidèle. Pour moi, les MCxxx, MDxxx sont à côté des
résultats du PR781 des microphones très classiques.

Contrairement aux postes de la marque Yeasu tels que le FT2000, FT950, FTdx1200, FTdx3000, FTdx5000,
le PR781 nécessite une adaptation entre le microphone et l' IC7300.

Alors voici le retour d'expérience de NZ4J :
My settings are PURELY SUBJECTIVE.

In comes the Behringer XENYX 502 (cheap, but works)...

The 502  is set for lowered low frequency output for the Heil PR781. In order to avoid the typical behaviors of running the 7300 input gain at max (potential distortions, which, by the way may be nil if the mic gain is all digital), I have added a $40 Behringer XENYX502 between the mic and rig. It requires some cable construction to adapt the Heil Cable to the XLR input and a 1/4" mono plug with good shielded audio/mic cable for connecting to the 7300.

Parts required:
Original Heil Cable (XLR to 8 pin ICOM w/PTT 1/4" female at the Rig End)
New Male XLR connector
New Male 1/4" Mono plug
About 3 Feet of shielded Mic cable (mine was 2 cond +Ground/Shield) surplus

1. Cut the Heil Cable near the rig end such that you preserve the wiring from the 1/4" Female Connctor (PTT).
Using t he 8-Pin connector and the remaining (short) wires from the Heil Cable, identify the wires and connections by comparing to connector wiring drawings in IC-7300 manual. They are pretty straight forward. Identification of the wire colors (Heil Cable to 8-Pin) for the MIC wires is essential when building the NEW 1/4" Male to 8-PIN MIC cable.

2. Add the NEW XLR Male Connector to the end of the Heil Cable going to the PR781.

3. Using NEW Mic cable, wire to the pins on 8-Pin connector and the Mono 1/4" plug.

Note that the bypass CAP is not contained in the 8-PIN connector end of the Heil Cable. It appears to be on the other end (Mic End XLR Connector).

I have performed some initial on air evaluations (need to do some more) with the following settings as a result of those QSOs...

Behringer XENYX502
    Input Gain is about 0 db
    Eq High (12 Khz) is 0.0
    Eq Low  (8 0 Hz) is about -8
    Level is set to about -6 db

The mono output is taken from Main Out L
    Main Mix is set to about +6 db

I am sure you can do the math for all the stage gains and find other settings that are acceptable/equivalent.

The 7300 monitor (in the ear) audio sounds clean. The audio scope waveform on the 7300 is unremarkable.
The Behringer XENYX302 Phones output is also clean sounding.

Note that the Main Mix Audio Level LEDs which indicate Main Out output levels are almost always indicating less than or equal to -20 db. Anything higher appears to over-drive the input to the 7300 and produces distortion.

IC-7300 Rig settings (YMMV):

Mic Gain  is 30%
Compression is OFF  (more testing needed here)
TX Bass is 0    (the 502 is the main control for filtering)
TX Treble is 0
TBW Wide  (have not tried narrower TBWs.)

Again, since there are "duplicated" settings between the 7300 and the 502, you can find equivalent performance with different settings.

The Behringer XENYX502 is only employed when using the PR781.

NOTE: The settings on the 7300 are "middle of the road" and are deliberately "close to the desired settings" that give good performance with a Heil Proset iC headset and almost "close to the desired settings" for an ICOM SM-20 with the mic Base Response (on base of MIC) set Low Cut = ON.

More testing is needed, of course.


et voici quelques photographies :

La petite table de mixage Behringer Xenys 502 ne vaut qu'une trentaine d'euros :

Il ne vous restera plus qu'à réaliser une connectique d'adaptation de la prise de l' IC7300 vers la pédale PTT et vers la table de mixage.

Un enregistrement audio devrait me parvenir dans les jours à venir. Il faudra revenir parcourir ce sujet...

A bientôt,
Ludovic - http://inforadio.free.fr

Date d'inscription : 08/06/2008


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