L15D Build

doors666 · Jul 9, 2012

I finally pulled the plug on the LJM's L15D amp. The original thread for this is here - IRS2092 (IRAUDAMP7S) + IRFI4019 - diyAudio.

I purchased it from this link - 300W IRS2092 IRFI4019H IRAUDAMP7S Amplifier kit L15D | eBay.

I havent received the kit yet. I am starting this thread so that I can document the entire process and maybe it will be helpful to some one else wishing to build their first amp. I still need to procure the following items:

1. Soft start. (is this really necessary if I am using speaker protection circuit.
2. Speaker protection circuit.
3. Transformer.
4. Power supply
6. Power supply capacitors.
7. RCA, binding posts, IEC socket, power switch etc.
8. Cables for power, cables for signal.
9. good quality solder, flux.
10. cabinet.

The amp runs on +-45 to +-60 VDC. The recommended voltage is +-50V. I plan to probably run it on some 52-53V, this will give me slightly more power without impacting distortion much. I plan to use 4 ohm speaker (thats the lowest they go). 53V will give me 300w, while 50V will give me 250w into 4 ohms. 8 ohms will be half of that.

Trafo - 39-0-39. This will give me (38-1.4)*1.414=53.16VDC. Please correct my calculations if its wrong. dont want to end up with the wrong trafo.

for 53VDC supply, 63V caps should be fine right?

More to come later...

sachu888 · Jul 9, 2012

Hi Vikas,
Thanks for starting this thread.IRS class D and Tripath amps are on my radar.I need them for my second set up.I have started collecting Gerber files for that.I am sure you will enjoy this amp as reviews are very positive.This will nicely match with your B1 or SSP.

Regards,
Sachin

sound1 · Jul 9, 2012

doors666 said:
1. Soft start. (is this really necessary if I am using speaker protection circuit.

I think this is required if you are putting big caps in power supply to prevent your house fuses from blowing off. I am using 30,000uf without any issues, lights will slightly dim when I switch on the amp that is all.

doors666 said:
for 53VDC supply, 63V caps should be fine right?

From where are you buying the caps??

kaushik · Jul 9, 2012

Can i do 5pair of kit : distribution@actuals , yes to promote DIY

i order kits, i pay all
all people pay locally
no risk no paypal needed for all

Any one joining this list ?

1. ...
2. ....

May be be others can join.
respected forum members provide other elements EI/toroids
PSU boards

doors666 · Jul 9, 2012

sachu888 said:
Hi Vikas,
Thanks for starting this thread.IRS class D and Tripath amps are on my radar.I need them for my second set up.I have started collecting Gerber files for that.I am sure you will enjoy this amp as reviews are very positive.This will nicely match with your B1 or SSP.

Regards,
Sachin

B1 will handle the amp end. ssp will handle the source. ldr in between. I would like to also get a tube pre one day (of course diy) and give it a shot. any recommended cheap builds known for their good sq?

sound1 said:
I think this is required if you are putting big caps in power supply to prevent your house fuses from blowing off. I am using 30,000uf without any issues, lights will slightly dim when I switch on the amp that is all.

From where are you buying the caps??

I thought thats due to torroidal inrush current rather than the caps.
I havent decided yet where to get the caps from. How much capacitance do i need for this build? The amp is very efficient, so shouldnt be that much.

kaushik said:
Can i do 5pair of kit : distribution@actuals , yes to promote DIY

i order kits, i pay all

all people pay locally

no risk no paypal needed for all

Any one joining this list ?

1. ...
2. ....

May be be others can join.
respected forum members provide other elements EI/toroids
PSU boards

Thats a good idea. maybe we can also identify some parts that will improve the performance over a period of time.
The input impedance of this dude is only some 3.3k. Way less than ideal, so a buffer/preamp is going to be needed. The members should join the ssp gb.

omishra · Jul 9, 2012

These are PWM based amps will not need bigger caps just 10000F per rail per channel with do. Bigger than this will add ripple current and less help for output noise reduction due to PS ripple. Still I suggest for for bigger transformer with at least VA 1.25 times both channel wattage. Above 500VA you must have soft-start to stop tripping of mains.

doors666 · Jul 9, 2012

omishra said:
These are PWM based amps will not need bigger caps just 10000F per rail per channel with do. Bigger than this will add ripple current and less help for output noise reduction due to PS ripple. Still I suggest for for bigger transformer with at least VA 1.25 times both channel wattage. Above 500VA you must have soft-start to stop tripping of mains.

I am planning to use a 400VA trafo for this.
That means 2*10,000 mfd caps right.
My sub already caused that problem and I got the mcb changed to 15A, so that might not be an issue. So I guess I will just go with the speaker protection circuitry and later take a call on soft start if I see issues. sub gives a nice thump also while starting, I guess its due to lack of spkr protection in the amp.

kaushik · Jul 9, 2012

@doors can you make a list of items after arrive at reqd ratings from all discussions , lets estimate cost and effort

quad · Jul 9, 2012

Great. Looking forward to your project, and the pics.

Soft Start is good to have, as Om said. You can use a CL-90 or similar
NTC to prevent fuse blowing due to inrush.

I think 35-0-35 transformer should be ok.
For safety, you can go with 10000uf, 80V - they are about Rs 100 each here in Hyd.

Check out the Bora OMNI protection circuit.
http://bas.elitesecurity.org/omni.html

doors666 · Jul 9, 2012

kaushik said:
@doors can you make a list of items after arrive at reqd ratings from all discussions , lets estimate cost and effort

sure, will do that.

quad said:
Great. Looking forward to your project, and the pics.

Soft Start is good to have, as Om said. You can use a CL-90 or similar
NTC to prevent fuse blowing due to inrush.

I think 35-0-35 transformer should be ok.
For safety, you can go with 10000uf, 80V - they are about Rs 100 each here in Hyd.

Check out the Bora OMNI protection circuit.
http://bas.elitesecurity.org/omni.html

I saw some other people using thermistors in diya.

So far I am planning to go slightly higher than the recommended 50vdc, probably some 53vdc. Range is about 45-60v.

Which 80v caps are these?

sound1 · Jul 9, 2012

doors666 said:
I thought thats due to torroidal inrush current rather than the caps.
I havent decided yet where to get the caps from. How much capacitance do i need for this build? The amp is very efficient, so shouldnt be that much.

I stand corrected

And even I am looking for 2x 10,000uf (80V) caps. This looks interesting (and expensive) Nichicon Capacitor Series KG

PS: FWIW, the power supply of my Class D amp uses 35-0-35 400VA toroid with (Nichicon) caps adding up to 28,200uf (6 x 4,700 uf).

murali_n · Jul 9, 2012

Hi all,

Are not these cost effective?

Panasonic_Capacitor_Analog Metric - DIY Audio Kit :yahoo: :licklips:

N.Murali

doors666 · Jul 10, 2012

How important are the psu caps. these are not in the signal path, so wont some decent brand be fine without any need for going exotic.
Are there any good caps available on SP road.

omishra · Jul 10, 2012

doors666 said:
How important are the psu caps. these are not in the signal path, so wont some decent brand be fine without any need for going exotic.
Are there any good caps available on SP road.

Okay, so these are from Guru's mouth Elliott Sound Products - Linear Power Supply Design

Read and I hope it will help you on this topic.

murali_n · Jul 10, 2012

Hi doors,

Samwha brand may be cheaper at Rs.200/- per 10000uf capacitor.

N.Murali

mbhangui · Jul 10, 2012

quad said:
Soft Start is good to have, as Om said. You can use a CL-90 or similar
NTC to prevent fuse blowing due to inrush.

How does one connect the CL-90 termistor? Does one connect the CL-90 in series to the primary or in the secondary.

t.antony · Jul 10, 2012

doors666 said:
...
Are there any good caps available on SP road.

You can get nichicon, nippon, elna caps from cee pee electronics (next to vishal)
Try Pooja for Chemicon, elna capacitors
Keltron caps are available in Keltronix (before amar radio corporation)

omishra · Jul 10, 2012

mbhangui said:
How does one connect the CL-90 termistor? Does one connect the CL-90 in series to the primary or in the secondary.

In series of primary, it shows high resistance initially and drops after surges is over.

sound1 · Jul 10, 2012

doors666 said:
How important are the psu caps. these are not in the signal path, so wont some decent brand be fine without any need for going exotic.
Are there any good caps available on SP road.

Here is an impressive article on power supply design. According to the author, caps are important.
Solid State Power Amplifier Supply Part 1

L15D Build

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