Hello,
I have multiple ljm L15D Pro Boards. SMPS is a connexelectronic. I have a multichannel system and the speakers are active.
My Problem: The Front speakers (tweeter + midrange) both have a very high sensitivity (97dB/1w/1m). So there is a noticeable noise at the listening postiztion. The other speakers which are not so sensitive are quiet. The source Volume (4,9V DAC) is in the moment trimmed by an analog attenuater (trim poti) and the main volume is controlled digitally.
Is it possible to change the gain factor of the amp, so the noise could be lower?
PS: The noise is independant of the volume setting.
Regards
Jens
I have multiple ljm L15D Pro Boards. SMPS is a connexelectronic. I have a multichannel system and the speakers are active.
My Problem: The Front speakers (tweeter + midrange) both have a very high sensitivity (97dB/1w/1m). So there is a noticeable noise at the listening postiztion. The other speakers which are not so sensitive are quiet. The source Volume (4,9V DAC) is in the moment trimmed by an analog attenuater (trim poti) and the main volume is controlled digitally.
Is it possible to change the gain factor of the amp, so the noise could be lower?
PS: The noise is independant of the volume setting.
Regards
Jens
Hi Jens ,
See this post : LJM Gain L25-D Gain Help
gain Resistors on the L15Dpro seems to be in the same position as on the L25D
Cheers ,
Rens
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Hi Jens,
I've just finished to assemble a multichannel amplifier with 8 L15D pro boards and 2 SMPS800RE from Connex also thanks to the invaluable help of another partecipant of this forum, Fulvio.
I also have an annoying noise coming from all the drivers, but only when the 2 units are powered together. On individual basis, i.e when the two channels are powered one at time, they are totally silent and sound great! This noise disappears when the wiring connecting the two channel at the level of the star point signal ground is disconnected (0V of both SMPS output, 0V input of each board). The issue doesn’t seem chassis-related because the noise occurs even if the signal ground pathway is disconnected by the chassis, it is sufficient that the signal grounds of the two units are wired together.
How SMPS have you?
Under the usual guidance of Fulvio my next step will be to try different grounding approaches (i.e. antiparallel diodes and resistor). I also wrote to Connex looking for an advice and I'm currently waiting for a reply.
Obviously any suggestion is welcome to solve this issue
Connex answered me within a couple of hours from my message (sic!). They given me a lot of explanation and possible solutions to solve the issue of noise coming from the two PSU. They also asked me some photos of the system to find (if any) the error/s causing the noise.
Impressive support!
GiAnt
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