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LJM Audio

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ljm_ljm

Member
Joined 2006
adiaz said:
Can anyone tell me what is the sound quality of the L15D?

Normally the class D sound worse treble.

What would you advise me?, Build a class AB amplifier with mosfet or buy ljm L15D Class D.

to amplify studio monitors.
Thank you.
Click to expand...

I'm using L15DX2 as my home amplifier.
Use the computer as a source of sound, PMC FB1 + as speakers.
Its performance is very good.

If you like class AB. A simple small amplifier L6 is very good,
 
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audionootje

Member
Joined 2011
L-15D mounting 4019H & D669 on heatsink

Hi Everyone,

Nearly finished soldering the L-15D modules, but I'm a bit confused about how to mount the 4019H and D669 to the heatsink. The confusion started when looking at pictures of the L-15D Pro on ebay, where it was clearly stated that insulation should be used. Is this needed for the L-15D as well? Or can they be just mounted to the heatsink directly?
 
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audionootje

Member
Joined 2011
Can anyone help me answering my previous question. I know it must be a stupid newby question, but I cannot figure it out. I've looked at the IRF documentation on the 4019H and at the reference design document for IRAUDAMP7D, but could not find any information regarding the insulation. I'm an audio hobbyist looking for help.

Thanks in advance.

Arnoud
 
M

MrSlim

Member
Joined 2009
audionootje said:
Can anyone help me answering my previous question. I know it must be a stupid newby question, but I cannot figure it out. I've looked at the IRF documentation on the 4019H and at the reference design document for IRAUDAMP7D, but could not find any information regarding the insulation. I'm an audio hobbyist looking for help.

Thanks in advance.

Arnoud
Click to expand...


I purchased a pair of completed L15D's and they did not have insulating pads on the devices, so you are probably fine without. Notoriously, they also did not have any heat sink compound, which I made sure to add before firing them up.
 
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alkasar

Member
Joined 2009
audionootje said:
Can anyone help me answering my previous question. I know it must be a stupid newby question, but I cannot figure it out. I've looked at the IRF documentation on the 4019H and at the reference design document for IRAUDAMP7D, but could not find any information regarding the insulation. I'm an audio hobbyist looking for help.

Thanks in advance.

Arnoud
Click to expand...
Depends on the package. Does your 4019H have a metal back ? if yes, an insulation is needed.
Seems to me that IRFI4019H is in an insulated package, so no need for insulation pad.
2012-11-05_1329.png


However, I would definitively put thermal paste !


edit: oops, response crossed MrSlim ;)
 
S

skipt

Member
Joined 2012
L7 Amp

I too have bought the kit and have reversed engineered the schematic. I'd like to compare mine with others. What is the verdict on sharing?

I'm using the L7 to replace a blown power amp in a Janis Interphase 1A subwoofer amp. I'm almost ready to power up. I'd like to cross check my schematic before doing so. I plan to power up slowly using a variac, but am not sure what to look for on the output mosfet voltages. i.e. if they were bipolars, I know I can watch for the Vbe's to come up to 0.7. Any tips?
 
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audionootje

Member
Joined 2011
ZhurayYuk said:
How this L15D performs on low power levels 5-10W ?
Click to expand...

I'm not sure how much power i'm using whilst listening to my music, but I doubt I ever reach 5 - 10 Watt RMS :)

It sounds pretty good on my Dynaudio Audience72SE. When compared to a lyngdorf TDAI 2200 it lacks a little refinement (harsher highs), but for the money i think it is unbelievable. There is a little white noise when you put your ear close to the tweeter. According to the specs it should be dead silent. The amps are connected to a connexelectronic SMPS 800RE powersupply and they get their signal from a Emotiva XDA-1 DAC. This is all rather subjective. Will post more factual information later.
 
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pet007

Member
Joined 2012
Hi, right now I'm testing L15D amp, I have to say, it sounds very good at low volume levels, I am satisfied :)
Anyway the output inductor is quite hot, is it normal ? My idle current consumption are -50mA and +30mA (+/-55V). I have L15D kit (and all components) from eBay zoe_tsang shop. Inductor is square type OFC? 14A / 0.012Ohm. Thanks.
 
D

daol

Member
Joined 2004
Hello, I bought to Along1986 the kit L15D ver3 last year (two boards) and I have the same problem with the two boards: the positive supply voltage rises gradually from +52 to +72 volts vots and negative supply down from - 52 volts to -38 volts, thereby raising the temperature of the resistance of 3K3 which feeds the zener 5V6 on positive supply.
I built the two boards and I guess I made a mistake when placing components, LJM, can you send me the schematic and component mask? can it happen by self oscillation?

Test condition:
Power supply: +/-52 volts, linear
Input: no signal, open.
Output: 10 ohms load and without load.
Blue Led: ON
Signal at output: ~400Khz, 400 mV p-p


Sorry for my bad English.


Regards,


Daniel.
 
Last edited:
nigelwright7557

nigelwright7557

Member
Joined 2008
murtonpikesystems.co.uk
daol said:
Hello, I bought the kit to Along1986 L15D ver3 last year (two boards) and I have the same problem with the two boards: the positive supply voltage rises gradually from +52 to +72 volts vots and negative supply down from - 52 volts to -38 volts, thereby raising the temperature of the resistance of 3K3 which feeds the zener 5V6 on positive supply.

Daniel.
Click to expand...

This sounds like bus pumping. It is most prone when applying a sine wave especially low frequency.
When inputting normal music it should be fine.
 
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