Hi, I'm making this thread as a build in progress and asking thread, since I want this amp to be as "hifi" as possible with this budget.
I'm building a LJM L15DSMD bi amp for my 2 B&W floor standing speakers. These speakers are rated at 200W 8R each, so I chose to use 4 boards, to keep boards cool and distortion low.
I bought a 50V +/- 500W SMPS from China and 2 protection boards.
I want a fuse before the SMPS. 500W/230V=2,17A. How big should I chose the fuse then? Would I need fuses AFTER the SMPS to protect it from amp board failure?
The enclosure I bought was for a TI amp, so I had to stack the LJM board. Would this introduce problems? I will be stacking 2 left and 2 right. I twisted the input wires for each board, and then twisted them again. Is this to reduce wire inductance or noise? Should I even twist them again?
I will add the 500W SMPS in the middle. Should I be worried about any noise issues. "Keep stuff far away from other stuff". Still waiting for the SMPS
I'm building a LJM L15DSMD bi amp for my 2 B&W floor standing speakers. These speakers are rated at 200W 8R each, so I chose to use 4 boards, to keep boards cool and distortion low.
I bought a 50V +/- 500W SMPS from China and 2 protection boards.
I want a fuse before the SMPS. 500W/230V=2,17A. How big should I chose the fuse then? Would I need fuses AFTER the SMPS to protect it from amp board failure?
The enclosure I bought was for a TI amp, so I had to stack the LJM board. Would this introduce problems? I will be stacking 2 left and 2 right. I twisted the input wires for each board, and then twisted them again. Is this to reduce wire inductance or noise? Should I even twist them again?
I will add the 500W SMPS in the middle. Should I be worried about any noise issues. "Keep stuff far away from other stuff". Still waiting for the SMPS
3.15A fast? in any case, it will blow in gross overload only (short). Everything else is job for smps
Stacked amps... ok, as long as cooling is enough, so check that
Stacked amps... ok, as long as cooling is enough, so check that
I'm not so worried about the heat. If that even becomes a problem, I will add a fan. Also. I got a thermal camera, so I can keep an eye out. Was more afraid of noise? 3,15 is 1A more than my calculations? I have no clue what the inrush current is on a switchmode....
Got some more parts today. Still waiting for that SMPS....
Finally done. I really like the sound and power of this amp! I measure no bus pumping at all.
Ive got a slight hiss from tweeters and hum from woofers. Is it the boards themselves or can anyone spot anything in my wiring? Ive been very careful not having wires touching.
Ive got a slight hiss from tweeters and hum from woofers. Is it the boards themselves or can anyone spot anything in my wiring? Ive been very careful not having wires touching.
Just curious, do I see speaker protection boards AND a delay board? I think the speaker protection boards might have the delay built in already. Doubling up on delay?
Maybe you see the 5V relay board in the middle? It just flicks on the amplifier, when my TV turns on. (USB)
Hope someone has some tips and pointers to the hiss/hum issue.
Hope someone has some tips and pointers to the hiss/hum issue.
It looks like a ABS plastic cabinet? If correct, then that could be an issue.
You should also twist the speaker cables. Right now they act like antennas. You have a quite big loop between positive and negative
You should also twist the speaker cables. Right now they act like antennas. You have a quite big loop between positive and negative
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But there is nothing electric anywhere near the amplifier. I thought plastic cases only were trouble with surrounding noisy appliances.
My BMC 2 HD DAC runs off a switchmode and so does the apt-x module plugged into it. I tried removing both psu's and disconnecting the input RCA's. Made no difference at all. Not even a tiny bit. Noise must be coming from inside. Both speakers have the same hiss. My experience with TI chip boards was too high gain, but these L15DSMD dosnt seem to have a very large gain. If I lower that, Im going to have trouble reaching high volumes with my BMC2 as preamp. So I dont wish to do that. Will try to twist those wires after the DC protection boards and see if it makes a difference.
My experience is that noise is lowered when putting electronics in a metal box. Just putting on the lid will give you less noise. We are not talking much, but definatly audible.
Tried removing the input connectors from the amp boards. Made no difference at all :-(
Tried running speaker protectors from separet power supply. Still hiss.
Tried connecting speakers directly to amp boards with no dc protection. Still same hiss.
Must be coming froom PSU or boards themselves?
Tried connecting speakers directly to amp boards with no dc protection. Still same hiss.
Must be coming froom PSU or boards themselves?
Star Ground
You're not using a star ground and "daisy chained" the supply rails from the upper amplifier to the bottom ones . Using a star ground point near the SMPS could solve your hum problem . The IRS2092 is a bit noisy , but at around 1 m from your tweeter the noise must be inaudible , depending on your speaker sensitivity .
If you decide to convert to star ground , make sure your negative speaker connection , now connected to the "-"out of the L15D is also connected to the star ground .
Cheers ,
Rens
You're not using a star ground and "daisy chained" the supply rails from the upper amplifier to the bottom ones . Using a star ground point near the SMPS could solve your hum problem . The IRS2092 is a bit noisy , but at around 1 m from your tweeter the noise must be inaudible , depending on your speaker sensitivity .
If you decide to convert to star ground , make sure your negative speaker connection , now connected to the "-"out of the L15D is also connected to the star ground .
Cheers ,
Rens
So I should twist + and - wires, without the GND, and then make a star point and run individual wires to each amp and speaker GND?
The humming is very low. But compared to the hiss, I can't live with the humming 🙂
BTW. If I remove, ALL input wires. The hum dissapears. If I only remove inputs on either left or right, hum stays. Cant figure out why.
Should I maybe change to shielded wire and "daisy chain" the inputs?
Shielded wire . vs. twisted wires is a different discussion , don't think it will make a difference . Don't understand what you mean with "daisy chained inputs" attached a picture of my 5 channel L15d amp ,running without Hum and no audible noise 1 M from very efficient Tannoy speakers for 5 years now . bottom left you can see how I made a star ground with bolds and nuts on a plastic cutting board (black wires ). each amp has its own dual rail supply ( Blue and Red wires ) and all speaker negative connections go directly to the star ground .The inputs are well separated from the outputs and power supply ( Right top of picture I used shielded wire , but twisted is OK )
I didn't even twist my speaker wires and supply wires , they are very close to a 3 mm grounded aluminium bottom plate .
I my setup a Sony DVD player is on top of the amp and I have no problems with interference .
Cheers ,
Rens
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