Bought a XY LM3886 Kit.

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R

redjr

Member
Joined 2011
Kaplaars said:
Interesting threat guys, thanks for sharing knowledge. I bought the XY-PCB’s as well and recently completed it. I’ve red the threat through and was actually quite surprised to observe that people were struggling with potential groundloops which made them to cut traces. I found it a bit more logical to first build the kit, test it in a controlled environment and assess how it performs. It have to say that it actually performs already quite well without any of the suggested modifications. I have not experienced any hum, or hiss with and without connected cables. On the oscilloscope can no oscillations or ringing, even when injecting square waves, be noticed. Of course, a proper layout is essential and for example using a toroidal transformer could possibly already help a lot to prevent coupling of the magnetic field into your audio signal. In addition, I clearly remembered; thou shalt twist wires ;-). Since it already performed properly, I have not used shielded cables, or COAX for the interconnects. What I really like about these PCB’s, next to their simplicity and low price, is that the PCB that harbours the PSU capacitors, has two solder points below that enables one to connect the circuit ground with the chassis. I have not used a resistor to limit the ground loop current, although I have added the chassis to the safety GND as well.

However, although performing well, I have added some extra bits. To prevent interference from my amateur radio transmitter :-D, I decoupled both (V+ and V-) supply lines with a 100 nf cap. In addition I have added the 220 pF filter cap across the 22k Ohm resistor as suggested here, so high frequencies are filtered off. Although the LM3886 chip harbours some protection circuits as well, I have added a DC protection circuit. I am thinking of adding a Zobel/Thiele network; athough my speakers are not that complex, it can’t do harm.

I am really surprised with how well it performs. It is unbelievable how good such a simple amplifier can sound. In this case the less is more philosophy really applies. My goal is getting maximum results with the least amount of money possible. Even the power button is salvaged from an old, broken Sony tc-k15 cassette deck that fitted quite nice with the cabinet.

Well pictures say more than words:

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


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Kaplaars,

Do you have a BOM for the XY LM3886 and PSU PCBs you used for this amp that you wouldn't mind sharing? I've got a couple of the kits on order, but would like to know what component selection you used so I can order the right parts ahead of time.

Thanks,
Rick
 
Kaplaars

Kaplaars

Member
Joined 2010
Hi Rick,

Unfortunatelly I have not got a BOM file. I had most components already in stock, so I have not got ordering codes either.

However, if I recall it right I have used per LM3886 PCB:

3x 100 uF, 50V BC components
1x 22 uF, 63V BC components
1x 2.2 uF Wima MKS2 63V (other amplifier 1x 1.0 uF Philips MKT 63V, just to compare).
1x FUKUSHIMA Japan Noninductive Resistor 5W/0.1ohm (seller advises 0.15 ohm, but 0.10 will do just fine)
1x LM3886TF (insulated version)
R2, 3R, R5 22K ohm, 0.5W metal film, Vitrohm
R4, R6 1K ohm, 0.5W metal film, Vitrohm
3x 2.54 molex connectors

Optional:
1x 220pF Wima FKP (attached in parallel with R5 below)
2x 100nF to decouple the power leads (I have added them in parallel with the two 100uF caps below)

PSU:
4x 4700 uF, 63V Rubycon (you could use more capacitance per capacitor but that is not really necesairy; the LM3886 has a very reasonable PSRR)
2x LED
2x 4.7k ohm, 0.5W (LED series resistor)
6x 100nF, 63V Epcos MKT (blue ones) and 63V ERO (green ones) MKT
1x diode bridge KBU1006G 10A, 800V
1x 300VA, 2x 22VAC Amplimo toroidal transformer (78015)
2x connector, 3P, 7.5mm spacing

Optional:
bleeder resistors
1x custom made aluminum heatsink for the diode bridge

And of course some other bits for the VU-meter driver, low voltage power board, speaker protection, a ferrite clamp for the mains leads etc.
 
Kaplaars

Kaplaars

Member
Joined 2010
By the way, (sorry I can not edit the previous post anymore) I have tweaked the amplifiers again for a little bit :). Although I liked the white and green LED's, I wanted the amplifiers to become be more similar to each other. Since I really like the high end Marantz stuff from the 70's (Esotec series... :drool:, very rare and thus too expensive for this poor student :D) I used them as inspiration. These amplifiers commonly have blue VU's. However, I did not manage to find the right LED's; most blue LEDs are often much too bright and have an annoying appearance. But... luckily I have found LEDs that were just right for the job! This resulted into:

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


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

redjr

Member
Joined 2011
Kaplaars said:
Hi Rick,

Unfortunatelly I have not got a BOM file. I had most components already in stock, so I have not got ordering codes either.

However, if I recall it right I have used per LM3886 PCB:

3x 100 uF, 50V BC components
1x 22 uF, 63V BC components
1x 2.2 uF Wima MKS2 63V (other amplifier 1x 1.0 uF Philips MKT 63V, just to compare).
1x FUKUSHIMA Japan Noninductive Resistor 5W/0.1ohm (seller advises 0.15 ohm, but 0.10 will do just fine)
1x LM3886TF (insulated version)
R2, 3R, R5 22K ohm, 0.5W metal film, Vitrohm
R4, R6 1K ohm, 0.5W metal film, Vitrohm
3x 2.54 molex connectors

Optional:
1x 220pF Wima FKP (attached in parallel with R5 below)
2x 100nF to decouple the power leads (I have added them in parallel with the two 100uF caps below)

PSU:
4x 4700 uF, 63V Rubycon (you could use more capacitance per capacitor but that is not really necesairy; the LM3886 has a very reasonable PSRR)
2x LED
2x 4.7k ohm, 0.5W (LED series resistor)
6x 100nF, 63V Epcos MKT (blue ones) and 63V ERO (green ones) MKT
1x diode bridge KBU1006G 10A, 800V
1x 300VA, 2x 22VAC Amplimo toroidal transformer (78015)
2x connector, 3P, 7.5mm spacing

Optional:
bleeder resistors
1x custom made aluminum heatsink for the diode bridge

And of course some other bits for the VU-meter driver, low voltage power board, speaker protection, a ferrite clamp for the mains leads etc.
Click to expand...

That's perfect Kaplaars. I wasn't expecting a 'real' BOM, but this parts list is great. I've a got a couple different VU meters ordered, so will have some options when I finally put everything in an enclosure. :) I like your idea of mounting the PCBs on the heatsink/plate too. Helps maximize the interior space. I also liked the speaker protection PCB you used where it connects directly to the banana jacks. I found those on eBay and ordered some for future builds.

Rick
 
Kaplaars

Kaplaars

Member
Joined 2010
redjr said:
That's perfect Kaplaars. I wasn't expecting a 'real' BOM, but this parts list is great. I've a got a couple different VU meters ordered, so will have some options when I finally put everything in an enclosure. :) I like your idea of mounting the PCBs on the heatsink/plate too. Helps maximize the interior space. I also liked the speaker protection PCB you used where it connects directly to the banana jacks. I found those on eBay and ordered some for future builds.

Rick
Click to expand...

You are welcome Rick, glad I could help and am very curious to your build :)
 
R

redjr

Member
Joined 2011
Kaplaars said:
Haha, thank you Gideon :).

Since it is vacation - yay! - and I have received most parts to complete another LM3886 amplifier, I have started with completing LM3886 No. 2.

The design will be highly similar to No. 1, but some details will be different. For example, I have attached the LM PCBs directly to the heatsink, which I think is more convenient.

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


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


The PSU PCB is populated and fully functional.

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The next step will be drilling some holes in the cabinet.
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Michael,

I assume that is thermal paste (white) between the aluminum plates you're using and the enclosure sides? Or, is some sort of epoxy you used as well as the 4 machine bolts to secure it? I'm slowing gathering everything I need for my next LM3886 build. :)

Rick
 
Kaplaars

Kaplaars

Member
Joined 2010
Hi Rick,

I have used thermal paste (Amasan T12, industrial grade) only. The plates are bolted to the chassis plates with six M3 bolts each side. These bolts fitted really nice into the sleeve that the side plates already had. Therefore one can not see the bolts outside the chassis :).

Regards,
Michael
 
K

korpberget

Member
Joined 2016
Kaplaars said:
Hi Rick,

I have used thermal paste (Amasan T12, industrial grade) only. The plates are bolted to the chassis plates with six M3 bolts each side. These bolts fitted really nice into the sleeve that the side plates already had. Therefore one can not see the bolts outside the chassis :).

Regards,
Michael
Click to expand...

Damn fine finish both inside and outside! Love the big blue meters!
 
K

korpberget

Member
Joined 2016
I have ordered an xy kit myself. PCBs only. The plan is to put it in an Akai ac3500 chassis with a dab+ radio module and some other stuff. Lots of space in that cabinet.
Have to make a new silverfront for it, witch means learning how to etch aluminum. Exciting!
LM3886 are bougth at Elfa Distrelec. Should be the real deal. Even thou my Yuanjing is working perfect with the chines 3886's.
 
jvhb

jvhb

Member
Joined 2013
audioberg.dk/
Anyone building an LM3886 amp, should first read Neurochrome's (Tom Christiansen) excellent guide:

Taming the LM3886 Chip Amplifier

It clears up a lot of confusion/misinformation, and clearly shows the value of the Zobel-Thiele network, as well as the importance of decoupling and other important issues. Some of it is quite technical, but the main points are simple enough to understand.

And then consider making a donation for his efforts, or just purchase his 3886 pcb.. :)
 
K

korpberget

Member
Joined 2016
Well its getting there!
Connected all the dots now and the XY just went pop and buzzzz. He he.
Reconnected the cut traces for signal ground and it was fine.
Will cut them again as soon as the amp is in a chassis with proper ground.
Guess a separate ground cable must go from the point of cut traces?
Anyway - it sounds great! Turned the volume to max whit no input signal - no noise. Got <0,6 mv dc on output.
Gonna compare it to the Juanjing gainclone when everything is in place.
 
K

korpberget

Member
Joined 2016
Whoops there it is.
Hooked up with a Cambridge Azur 640C and Tandberg studio monitors.
The bass is deep and rich, the mids and highs are crystal clear, almost too bright at the top with controls at zero. (A mather of taste I guess)
I use a passive volume/tone control LG-147C from chinaaudio. No noice no hiss no hum.
Very pleased with the modded XY.
 
Berlusconi

Berlusconi

Member
Joined 2019
Hello dear friends ,
Quite recently, there was a limited number of LM3886T at Reichelt. I didn't want to miss the opportunity, I've purchased four pieces without hesitation. I was quick enough - they've sold them all in few days.
Yesterday the parcel with four new shiny ICs has arrived. Please, look at the snapshot below. Aren't they handsome?
I'm looking forward to build this fine amplifier again.
Have a pleasant day :cool:

Photo-001.png
 
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