JLM 60Watt Power AMP Kit

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Joe Malone
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Post by Joe Malone »

JLM 60Watt Power Amp kits Now Available

http://www.jlmaudio.com/JLM%20AMP.htm
Joe :-)
JLM Audio
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greenmanhumming
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Post by greenmanhumming »

cool! I had looked in the pulldown kits menu, and its not there so I thought it wasnt available yet.

I'll email you to get a shipping cost...

chrisp
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Post by chrisp »

I've been running my powered monitors for a little while now, and I can only find praise for these amp cards. They're typical JLM: pristine sound, well designed, grunt (I just patch -10dbv signals into the +4dbu inputs and still get more than acceptable SPLs out of them) and you can trick them out for all sorts of interesting things.


But truly fawesome sound: match them to good monitors and you're in heaven.
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

martthie_08
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Location: Stuttgart, Germany

Post by martthie_08 »

great to see that this kit is available!! A few quick questions:

How much VA would a single PSU trafo need to have for a stereo version of this Power Amp?

Is the PSU filtering onboard, trafo / diode bridge offboard?

Will the IC need a heatsink (or be bolted to the case)?

thanks, Marten

greenmanhumming
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Post by greenmanhumming »

I have similar questions.

I will be running each AMP separately off its own transformer, what VA transformer should I use for just one AMP? If 160VA will run 2 will 80VA run one or is it not that simple?

How much heatsinking does the kit require, and how does it attach to the heatsink? Can I use a plain aluminium sheet as a heatsink, and if so what area should it have?

could I have such a heatsink sheet screwed to the outside of a wooden speaker cab such that only one side is exposed to the air, and would that much increase the area needed? (i don't want heatsink fins on the outside of my cab if i can avoid it.)

does the kit include the vol pot and LED or do i need to order those separately?

what is the exact size of the PCB?

I'm planning an order locally of the external parts to coincide with arrival of the kits from australia so all info appreciated.

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Post by Joe Malone »

I've been running my powered monitors for a little while now, and I can only find praise for these amp cards. They're typical JLM: pristine sound, well designed, grunt (I just patch -10dbv signals into the +4dbu inputs and still get more than acceptable SPLs out of them) and you can trick them out for all sorts of interesting things.

But truly fawesome sound: match them to good monitors and you're in heaven.

:D :D 8)
How much VA would a single PSU trafo need to have for a stereo version of this Power Amp?
A 160VA is fine for 2 channels and 80VA for 1 channel.
Is the PSU filtering onboard, trafo / diode bridge offboard?
Yes the PCB has 8 x 1000uF caps on the PCB giving 4000uF of low ESR caps per +/-rail on board. So using 2 AMP kits on one transformer will give you 8000uF per +/-rail on board.

You can use one external 10A to 35A bridge rectifier to run a few AMP kits.
Will the IC need a heatsink (or be bolted to the case)?
Yes a 75mm length of most 100mm wide extruded heatsinks is enough for one amp kit. A aluminium panel can be used by itself but it is hard to predict its thermal ability. The LM3886TF is fully overtemp protected so it is safe to try to see if it shuts down due to lack of heatsinking. If using a aluminium flat panel for the back of a speaker enclosure make it as thick as possible (3 to 10mm) and the whole back of the speaker cabinet to get maximum area if it is a small speaker. The LM3886TF is also fully plastic encapsulated so no electrical isolation is needed. A small amount of thermal paste between the LM3886 and the heatsink can improve the heat transfer to the heatsink.
Joe :-)
JLM Audio
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Post by Joe Malone »

how does it attach to the heatsink?
Kit comes with a 3mm x 10mm bolt, lock washer and nut which is all that is need to hold the whole kit to the heatsink by the LM3886TF mounting hole. The PCB also has 2 mounting holes so the whole kit can be bolted to a aluminium angle bracket first if needed.
could I have such a heatsink sheet screwed to the outside of a wooden speaker cab such that only one side is exposed to the air?
Yes
does the kit include the vol pot and LED or do i need to order those separately?
Kit has red 3mm led but volume pot is not included. A normal dual 10kA log pot will control the volume of a stereo pair of amp kits.
what is the exact size of the PCB?
3" (76.2mm) x 1.5" (38.1mm)
Joe :-)
JLM Audio
Capturing Audio without Injury

greenmanhumming
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Post by greenmanhumming »

so this heatsink would do for a single AMP? or not quite?

93mm x 100mm x14mm fins
http://cpc.farnell.com/jsp/search/produ ... ku=SC01139


but this one should be OK?

120mm x 100mm x37mm fins
http://cpc.farnell.com/jsp/search/produ ... ku=SC01141

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Post by Joe Malone »

Both types will be fine for a single amp
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Smasha
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Post by Smasha »

I'd love to make those monitors but I'm dumb as doggy doo.


I'm gonna save and get the stuff and stress about it later.


What's that big round thing in the middle Chrisp?

Wow just had a look.

You get all the stuff including led in the kit-awesome.

I've been using an old Pioneer contempo mini hifi as monitors odear.


Stop laughing at me. :lol:

chrisp
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Post by chrisp »

Smasha wrote:What's that big round thing in the middle Chrisp?
Its a toriodal (= doughnut shaped) power transformer - it converts the mains power to a lower AC voltage, which is then passed through a bridge rectifier to make a DC voltage. As per Joe's diagram, this has two separate 25V outputs (its sold as 25-0-25), so there are four output wires: A0V, A25V, B0V and B25V. A0V and B25V go to the bridge rectifier AC inputs, and A25V and B0V are joined together to form what is called a centre tap - these two joined wires become 0V for the circuit and are connected to the PCB pin 4th from the right (0v, between MUTE and VOL-).
Smasha wrote:I'd love to make those monitors but I'm dumb as doggy doo.
Well, we're all here to help.

I think I spent close to $900 in making the pair of them, but for that I get the sound of $2000 speakers being driven by a $2000 amp, so I reckon its been worthwhile.

I find I'm starting to get used to them now. Rather than these sounding brilliant, I'm starting to think they're normal, and that other people have boomy, blurred sounding speakers. Sigh. Is there rehab for speaker snobs?
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

Smasha
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Post by Smasha »

Thanks ChrisP!

I think I will save and get the Jarrah cabs so I can look at them with Aussie pride hehe.

Did you use the boxes from decibelhifi?

chrisp
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Post by chrisp »

Yep - Brian's great.
Chris P
---------------------------------------------------------
I do lots of things. I believe eclectic skills are best.

Smasha
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Joined: Fri Jan 04, 2008 11:55 pm

Post by Smasha »

Gonna have to wait a while for these.

:cry: :cry: :cry: :cry: :cry:


I wish I was a rich businessman bastard!

Smasha
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Post by Smasha »

Sorry all.

My mood swings. :oops:

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