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Roland System 100 (model 102) noisy on LOW and HIGH outputs
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Christian



Joined: Sep 02, 2010
Posts: 11
Location: Canada

PostPosted: Fri Feb 17, 2012 5:28 am    Post subject: Roland System 100 (model 102) noisy on LOW and HIGH outputs
Subject description: MIXER section may cause this issue?
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Hello,

On my Roland System 100-102 Expander, I hear a kind of white noise from the LOW and HIGH output jacks when I plug a cord into (even when all sliders are down to zero).

I think the source of the noise comes from the MIXER section.

Is there a way to modify the 102 in order to bypass the MIXER section and have the VCA board signal redirected directly to the output jacks?
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Christian



Joined: Sep 02, 2010
Posts: 11
Location: Canada

PostPosted: Mon Feb 20, 2012 11:42 am    Post subject: Re: Roland System 100 (model 102) noisy on LOW and HIGH outputs
Subject description: MIXER section may cause this issue?
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On my Roland System 100-102 Expander, I hear a kind of (hissing) noise from the LOW and HIGH output jacks when I plug a cord in (even when all sliders are down to zero).

Anybody can tell me if it is normal to hear that from the audio ouput?


Here is tests I did so far to track down the hissing issue on the model 102.

FIRST APPROACH : OUTPUT FROM THE VCA CHECKPOINT
If I plug a cable in the VCA Checkpoint jack, hissing is gone. This result is predictable because the circuit diagram shows that the VCA signal is routed to the VCA Checkpoint before going through the MIXER and audio output sections. But what surprises me is that the level in dB is high on the dB meter (but not loud enough to get an optimal recording).

SECOND APPROACH : CONNECTING A PLUG IN THE MIXER
And the more confusing part is that if I plug a cable in its OUTPUT and I plug a another cable in the INPUT of the MIXER and I let dangle the other end of that same cable, i.e. not connected, the hissing becomes hardly noticeable! Someone can explain what happens?

If I set the INITIAL GAIN to the maximum level, hissing comes back but not as strong whatever the approach used for the connection. Is it normal?

HYPOTHESIS
There is probably a defect either in the MIXER or pre-amplification, or maybe the jack has bad soldered point.

Any hint, please?
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