Hey folks, after watchin a number of videos from mr @michael beeny I pulled the trigger on L12-2 and received version 4.2 of this board.
I am a little confused about how things are supposed to be grounded. Can someone please help me check if the following wiring scheme is correct?
Option 1:
I am a little confused about how things are supposed to be grounded. Can someone please help me check if the following wiring scheme is correct?
Option 1:
- connect the speaker protect grnd to amps
- connect amp grounds to PSU
Attachments
Last edited:
Here are the parts I am using:
Speaker Protect:
https://www.aliexpress.com/item/32865569447.html
Soft Start:
https://www.aliexpress.com/item/32844604900.html
Speaker Protect:
https://www.aliexpress.com/item/32865569447.html
Soft Start:
https://www.aliexpress.com/item/32844604900.html
Attachments
I tested both option 1 and 2. Sadly I hear a persistent hum in the speakers. I posted more details here Post in thread 'L12-2 CFP Output amp 120W*2 8R' https://www.diyaudio.com/community/threads/l12-2-cfp-output-amp-120w-2-8r.196089/post-7904016
Can someone please guide me
Can someone please guide me
Speaker ground should be connected to the rectifier board ground terminal
Amp ground should be connected to the same terminal
Amp ground should be connected to the same terminal
If the hum is still here, try to completely disconnect one amp board, disconnect cable from the amp input, and short the input on the amp board by short (15-25mm) piece of wire
If hum still, check one by one rectifier diodes
If hum still, check one by one rectifier diodes
This i
Basically:
Amp ground to PSU ground
Speaker ground to PSU ground
Sadly I still get hum.
This is the option 2 as I posted above.
Basically:
Amp ground to PSU ground
Speaker ground to PSU ground
Sadly I still get hum.
The issue occurs as soon as I connect a source to BOTH RCA inputs. With source turned off or on I get the hum. It doesn't seem to amplify, just there like an annoying itch.
I have tried to:
I have tried to:
- Float the signal ground for one rca = no change
- Adding capictor in series to signal ground=no effect
- Testing each amp individually I get no hum
- After Removing the RCA input I get no hum
- After Removing one RCA I get no hum
I have been using the same dac, topping d50s with audiolab and also ljm mx50se - had no issues with it at all.
Chalky mentioned this in the other post:
Chalky mentioned this in the other post:
Update
I have fitted 2.2uf capacitor (audiophiler mkp, 400vdc) to both RCA input signals. The buzzing is slightly reduced but it's still there, albeit 80% of before.
With the system turned off I get infinite resistance across both RCA inputs after I installed the caps.
With the system turned on and no music playing at source.. I get a DC reading of
4.6mv at both the amp signal terminals. This is after the capictor has been put inline at RCA input.
Speaker terminals have a DC reading of:
DC -52mv and DC -45mv
The buzz is still there:
Summary of what i have so far tried:
I have fitted 2.2uf capacitor (audiophiler mkp, 400vdc) to both RCA input signals. The buzzing is slightly reduced but it's still there, albeit 80% of before.
With the system turned off I get infinite resistance across both RCA inputs after I installed the caps.
With the system turned on and no music playing at source.. I get a DC reading of
4.6mv at both the amp signal terminals. This is after the capictor has been put inline at RCA input.
Speaker terminals have a DC reading of:
DC -52mv and DC -45mv
The buzz is still there:
Summary of what i have so far tried:
- different input source
- different RCA cables
- different PSU
- twisted cables
- only 1 amp connected (no hum)
- only 1 RCA connected (no hum)
- no RCA connected (no hum)
- source off, both RCA connected (hum)
- source on, both RCA connected (hum)
- DC blocking capacitor on RCA (hum)
- NO DC blocking capacitor on RCA (hum)
- 2 alternative star grounds (details above)
Cap in series with the input creating low pass filter.
It just blocks 50hz.
I tested V4 modules with no hum issues with Yulong DA8 mk2 DAC, and both linear and switch mode PSU, the only a difference, that I didn’t connected either protection modules… those should not to cause hum, but keeping in mind a facts, about stability of LJM’s devices, I can assume anything about them.
Hi dakku: I would take the "negative" loudspeaker connections back to the main PSU negative. The protection board only requires the negative side of the speaker to be used as a reference sensor relative to the "positive" LS side. The wire can be quite thin as there will be no current flow. The relays then just interrupt the LS positive side which is all you need.
