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LJM Audio

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Philfr

Member
Joined 2012
Hi,
Thank's for reply..
Just for info, I use 20/0/20 volts with the LM3875, and it's works well.
When you said : " the product R1 and a capacitance. 15 pf. It with R1 LPF filter."
That mean that resistor R1 have a capacitance of 15pF ?
Phil.
 
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ljm_ljm

Member
Joined 2006
Max Woof said:
Hi,
I am thinking to use 2 toroidal transformers, 34 volt 400VA each to drive 4 ohm speakers. From what I understand this should give me 48 volt rails, suggested for 4 ohm speakers. What do you think- is it a little too much or what ?
Click to expand...

AC34-0-34 No problem.

Stereo as long as 200 va can satisfy the.

L15D Can work in very well 4 OHM.
 

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ljm_ljm

Member
Joined 2006
Philfr said:
Hi,
I don't understand..
Can you explain with more words ?
You would said that LM3886 have 15pF capacitance at input pin 10, and LM3875 have 0 pF capacitance at input pin 7 ?
Thank's.
Phil.
Click to expand...

First of all,
LM3886,LM3875 Both the parameters of the chip is not the same. So the details of the circuit can't use the same circuit diagram.

In addition to the input filter. LM3886 boot quiet time delay function.

So we can't put the two chips. Together.

They're different in many places.
 
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2channel

Member
Joined 2005
"Pro" model

I was about to purchase an L15D, then I noticed there is a "Pro" model which appears to have two switching Mosfets and speaker protection.

Does this protection eliminate turn off/on thumps? How much dc is required on the output to trip the relay? Is there any difference in performance between this model and the standard L15D?

I am using this amp to power a tweeter, so if the protection is not 100% then I will buy the standard model and get a protection circuit.

Thanks
 
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ljm_ljm

Member
Joined 2006
2channel said:
I was about to purchase an L15D, then I noticed there is a "Pro" model which appears to have two switching Mosfets and speaker protection.

Does this protection eliminate turn off/on thumps? How much dc is required on the output to trip the relay? Is there any difference in performance between this model and the standard L15D?

I am using this amp to power a tweeter, so if the protection is not 100% then I will buy the standard model and get a protection circuit.

Thanks
Click to expand...


L15D-PRO adds relay. But it uses a DC power supply to the relay. So it will not instantly shut down when power off . Due to the large -capacity electrolytic capacitors will persist for some time to provide voltage. Although I expect L15D-PRO will be better. However, the final results of the test yes. L15D distortion smaller. I guess the reason is the shorter of the copper on the board. Packaged together transistor . If you do not bother . L15D plus separate AC power protection would be better .
Although their differences are small .
 
joetekubi

joetekubi

Member
Joined 2011
Hi folks - first post here.

I got 2 of the 2092 L-15D boards and hooked them up to a SMPS that delivers +-48VDC.
Got everything connected - the led on the L-15 boards does not come on, and there is no sound on the output. For grins, here's a picture of the build.

An externally hosted image should be here but it was not working when we last tested it.


The PS with no connections, measures 0 VDC, and connected to the L-15 boards, it measures +30VDC and -18VDC. Here's the power supply:

An externally hosted image should be here but it was not working when we last tested it.


I've got some electronics experience, but not sure how to proceed. Any tips?
Thanks in advance!
 
joetekubi

joetekubi

Member
Joined 2011

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doctordata

doctordata

Member
Joined 2010
Wrong power supply

joetekubi said:
Sorry, my Google Drive images won't load -
Here is the power supply, I think it's a good one:
Amazon.com: Genssi 48V DC 7.3A 350W Regulated Switching Power Supply: Electronics

And I didn't mention that I have a star ground - every ground in the box goes to one point. Could that be a problem?

Here's another try for the pic of my build:
An externally hosted image should be here but it was not working when we last tested it.
Click to expand...

Seems like you bought the wrong power supply :Ouch:
The L15D needs dual rail voltage , -48V ground +48V
This is a single rail voltage power supply , only + 48V DC

Sorry , Cheers

Rens
 
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drahcir

Member
Joined 2013
joetekubi said:
Sorry, my Google Drive images won't load -
Here is the power supply, I think it's a good one:
Amazon.com: Genssi 48V DC 7.3A 350W Regulated Switching Power Supply: Electronics

And I didn't mention that I have a star ground - every ground in the box goes to one point. Could that be a problem?

Here's another try for the pic of my build:
An externally hosted image should be here but it was not working when we last tested it.
Click to expand...


looks like its a dual rail (+/-) from the picture posted in amazon but its kinda low in voltage. btw I also tested that amp using SMPS and i didn't like the sound, soundstage is so narrow/thin and the low end disappear so i switch back to linear PSU
 
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