JLM 60Watt Power AMP Kit

YouTube · Post by **Joe Malone** » Mon Mar 26, 2007 7:43 pm

Simple 60watt into 8 or 4ohm with low THD amp with balanced input.

More info here
http://www.jlmaudio.com/shop/index.php? ... oductId=18

PCB Measures 3" (76.2mm) x 1.5" (38.1mm).
Mounting holes 2.02" (51.31mm) apart and are in 0.49” (12.45mm) from edge and down 0.51” (12.95mm).
Allow 1” (25.4mm) above PCB height and at least 0.2” (5.08mm) under PCB

Barney · Post by **Barney** » Mon Mar 26, 2007 8:38 pm

I think i just found a way to power a second set of monitors

Lowfreq · Post by **Lowfreq** » Tue Mar 27, 2007 5:45 am

Awesome!!!!!!

That tiny little sucker is 60w??

ChrioN · Post by **ChrioN** » Sat Mar 31, 2007 11:30 am

I smell gainclone

YouTube · Post by **Joe Malone** » Sat Mar 31, 2007 12:12 pm

I think i just found a way to power a second set of monitors

Yes that what it is for as well as driving 20+ headphones etc.

It is just a LM3886TF which is fully insulated all over so requires no mica insulation kit. But the trick is in the circuit as it allows for balanced input and volume control with no extra IC's and keeps the LM3886 stable in all conditions. The LM3886 oscillates below the gain of 10 so the normal way to balance a LM3886 works fine until you unplug the input and then it goes supersonic oscillation at full power which tweeters don't like.

The number $2000+ Amps I have seen with the LM3886 chip in them these days is huge.

That tiny little sucker is 60w??

Yes and at low THD. Also you can wire a pair of AMP modules bridged and get 120watt by lowering the transformer to 2 x 18vac.

I smell gainclone

What is a gainclone?

ChrioN · Post by **ChrioN** » Thu Apr 05, 2007 5:54 pm

Joe Malone wrote: What is a gainclone?

Google it. Its a clone of this expensive sucker: http://www.sakurasystems.com/products/47amp.html

usekgb · Post by **usekgb** » Fri Apr 20, 2007 8:41 am

Have you though of doing an amp with the LM4780? It is basically two LM3886's in the same package. A couple cool things you can do:

1. Stereo amp on a single chip.
2. Balanced bridged amp on a single chip for 8ohm loads and higher.
3. Balanced bridged amp on two chips for loads under 4ohms by running both chips in parallel mode, and bridging two chips.

Cheers,
Zach

heath · Post by **heath** » Thu May 03, 2007 11:34 am

Joe Malone wrote:
The number $2000+ Amps I have seen with the LM3886 chip in them these days is huge.

So, quality wise, this would not be out of place pushing a pricey set of speakers for some high quality sound, yes? I see plenty of chip amps getting around these days, all with good figures/specs.

My DIY bug has moved from pre's and things to speakers and amps, it's infecting every part of my studio!

Oh, and it's my first post!

heath.

chrisp · Post by **chrisp** » Thu May 03, 2007 4:54 pm

(1) What the heat issue like? Do I need to bolt it to the Eiffel tower or anything?

(2) What the transformer current rating? How about the bridge rectifier?

YouTube · Post by **Joe Malone** » Thu May 03, 2007 9:51 pm

Have you thought of doing an amp with the LM4780?

Yes it is a good chip but not as easy to get as the LM3886 and also more difficult to heatsink well enough to keep the thermal protection from cutting in earlier than 2 x LM3886 just due to the surface area in contact with the heatsink. But would be great for a compact active monitor.

So, quality wise, this would not be out of place pushing a pricey set of speakers for some high quality sound, yes? I see plenty of chip amps getting around these days, all with good figures/specs.

The LM3886 amp is good and would take a lot more $ to get a small percentage better. Still the largest percent of error is in speakers themselves.

What the heat issue like? Do I need to bolt it to the Eiffel tower or anything?

No the amp runs in AB mode so it can get away with medium size heatsink but always use as much as you fit easily into the given area. A 300mm length to radial fin heatsink will look after 2 amps running fairly hard all day.

What the transformer current rating? How about the bridge rectifier?

A 160VA will do 2 amplifiers running as a stereo pair or if you are the overkill type then use 300VA. We use 35A 400v bridge rectifiers just because they are only about $5 and if you short anything the fuse will blow before the rectifiers.

heath · Post by **heath** » Thu May 03, 2007 11:46 pm

Sounds great Joe!

Now it's time for a kit, with the big trannies too. Overkill is rarely enough.

heath.

chrisp · Post by **chrisp** » Fri May 04, 2007 8:41 am

Thanks for the reply, Mr Malone sir.

Do you want the community here to put up its "top 5" wish list in order? FWIW, mine would be

(1) Opto compressor
(2) EQ
(3) Simple zener regulator
(4) This beast
(5) Micro champ

heath · Post by **heath** » Fri May 04, 2007 9:11 am

Joining the conga line...

1. HAL Kit (I need volume control and speaker switching)
2. EQ
3. Micro Champ
4. Amp
5. Opto Compressor

heath.

just.sounds · Post by **just.sounds** » Sun May 20, 2007 9:50 pm

1. SONTEC!!
2. BAN
3. Champ
4. HAL
5. FET compressor

And I think I will be ordereing all of them!

The thing is this is the one of the few company's that will let you check.
"under the hood". So you know exactly what you buy. And that looks very nice i might add!

Greetings

chrisp · Post by **chrisp** » Fri May 25, 2007 8:27 am

Joe / Matt

I'm sketching a powered monitor idea. Mute/volume will be handled remotely.

The mute terminals can just be left unconnected, but I'm not sure what to do with the volume terminals. Should I just bridge them, or place a small value resistor there. Signal in will be 0dbVU = +4dbu.

How are these boards coming along?