doubleroger
Well-known member
Hi all.
I have a Roland JC160. It's been on my bench for two years, feeding DC to its speakers. Yesterday I finally found the culprit, an open resistor. It is now taped to the wall of shame.
I thought it was all over, I could have a little party, I had to find a way to celebrate!! Quick let's get something to drink!
So I plugged my Rhodes into it and played. :'(
There was this little buzzsaw noise that I had forgotten about (well two years is long isn't it?).
Now that I finally put the cover back on it, I'm gonna have to take it off again, to get rid of that, as it makes any recording impossible, and the amp quite worthless.
OK, now that my little introductive story (cute wasn't it?) is told, let's get to the problem:
You can hear the noise in question and find the schematics here .
The schematics are a little hard to read but they are the only ones I found that related to my amp (sn:651870), so not really the right ones, but the amp boards were those ones, with the right transistors. There are lots of different versions of these amps, it seems... I'm not sure I have the right schematic for the effect board.
The sound is taken with a DI on the speaker output of Amp Channel number 2. It is supposedly the "effect channel amp" on JC-120s and JC-160s. My Rhodes is plugged into Input channel number 2, wich is the only input channel that can have effects. (input ch 1 is for a totally dry sound).
The JC160 frontpannel has a switch between "normal" (both amp channels amplify the same dry signal), "chorus" or "vibrato" (ch1 is dry amp, ch2 is the effect amp channel).
There is NO problem in "normal" mode. The sound is clean in both channels.
There is that noise with both "chorus" or "vibrato" settings.
The noise is only in the speakers of amp ch2 (wet). Amp ch1(dry) stays perfectly clean all the time.
The noise seems to get modulated by the effect (the soundfile has a vibrato, for example).
The noise only appears above a certain threshold.
Now what is (or not) funny is that if I plug my rhodes into Input Ch1 (the dry input channel), and turn on the chorus/vibrato, it feeds the usual hiss to the speakers (through the "effect channel" ch2 amp ). That is normal. But if I play into input Ch1 now, I don't get the vibrato (that is normal too), but I get the exact same modulated white noise I had before in amp ch2, like there was a leak somewhere...
Any pointers (or readable schematics) are welcome, there are so many informations that I need some of your analytic minds to help me
I have a Roland JC160. It's been on my bench for two years, feeding DC to its speakers. Yesterday I finally found the culprit, an open resistor. It is now taped to the wall of shame.
I thought it was all over, I could have a little party, I had to find a way to celebrate!! Quick let's get something to drink!
So I plugged my Rhodes into it and played. :'(
There was this little buzzsaw noise that I had forgotten about (well two years is long isn't it?).
Now that I finally put the cover back on it, I'm gonna have to take it off again, to get rid of that, as it makes any recording impossible, and the amp quite worthless.
OK, now that my little introductive story (cute wasn't it?) is told, let's get to the problem:
You can hear the noise in question and find the schematics here .
The schematics are a little hard to read but they are the only ones I found that related to my amp (sn:651870), so not really the right ones, but the amp boards were those ones, with the right transistors. There are lots of different versions of these amps, it seems... I'm not sure I have the right schematic for the effect board.
The sound is taken with a DI on the speaker output of Amp Channel number 2. It is supposedly the "effect channel amp" on JC-120s and JC-160s. My Rhodes is plugged into Input channel number 2, wich is the only input channel that can have effects. (input ch 1 is for a totally dry sound).
The JC160 frontpannel has a switch between "normal" (both amp channels amplify the same dry signal), "chorus" or "vibrato" (ch1 is dry amp, ch2 is the effect amp channel).
There is NO problem in "normal" mode. The sound is clean in both channels.
There is that noise with both "chorus" or "vibrato" settings.
The noise is only in the speakers of amp ch2 (wet). Amp ch1(dry) stays perfectly clean all the time.
The noise seems to get modulated by the effect (the soundfile has a vibrato, for example).
The noise only appears above a certain threshold.
Now what is (or not) funny is that if I plug my rhodes into Input Ch1 (the dry input channel), and turn on the chorus/vibrato, it feeds the usual hiss to the speakers (through the "effect channel" ch2 amp ). That is normal. But if I play into input Ch1 now, I don't get the vibrato (that is normal too), but I get the exact same modulated white noise I had before in amp ch2, like there was a leak somewhere...
Any pointers (or readable schematics) are welcome, there are so many informations that I need some of your analytic minds to help me