Bought a XY LM3886 Kit. - Page 16 - diyAudio
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Old 1st April 2012, 02:40 PM   #151
AndrewT is offline AndrewT  Scotland
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Audio and Safety are quite different.
Solve them differently.

Trying to combine them in your head is likely to confuse.
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Old 1st April 2012, 04:38 PM   #152
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Hi Pemo:

I really like your amplifier. I have few questions:

What is the PCB by the AC power inlet, top right corner in the picture?

What is the PCB by the volume pot, top left corner in the picture?

What kind of heatsinks are those?. Where did you get them from?.

I see that you used the XY LM3886 PCB's unmodified, they look exactly as the ones in the pictures posted by sellers at eBay, I guess you purchased them already assembled, how do they sound?.

Talking about my nickname here, I guess you like it because you know what it means... I have many mexican friends here in the US, all very good people, my best friend who is like my brother is from Oaxaca.

Take care...
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Old 1st April 2012, 04:40 PM   #153
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Pemo:

One more question:

That small transformer, is it to power the speaker protection board only?

Thanks again...
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Old 2nd April 2012, 03:58 AM   #154
Pemo is offline Pemo  Mexico
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[QUOTE=Aguilabrava;2968828]Hi Pemo:

I really like your amplifier. I have few questions:

What is the PCB by the AC power inlet, top right corner in the picture?

-> This is a micro USB DAC that I found on eBay.


It uses a PCM2704 decoder, and claims to have low Jitter. I only connect the amp to my computer.

What is the PCB by the volume pot, top left corner in the picture?

-> This is a Mini Pre-amp, that also found on eBay.


It uses an NE5532, and a very nice stepper pot. Don't use it, I'll remove it soon.


What kind of heatsinks are those?. Where did you get them from?.

-> Those are HP computer heatpipe heatsinks. I found them on a computer surplus store downtown Mexico City. I just removed the fans. They are REALLY EFFICENT. Right now the temperature in Mexico City is 24°C, and the temp of the heatsinks (and chips, there is a slight temp difference between the chip and heatsink of 1 or 2 °C) after a whole sunday playing music is 34°C.

I see that you used the XY LM3886 PCB's unmodified, they look exactly as the ones in the pictures posted by sellers at eBay, I guess you purchased them already assembled, how do they sound?.

-> Yes, they are unmodified. The amp sounds fantastic. Detailed, no hum at all, deep and powerful bass (I'm using a passive 12" subwoofer), cristal clear highs and very detailed (but soft) mids.

Talking about my nickname here, I guess you like it because you know what it means... I have many mexican friends here in the US, all very good people, my best friend who is like my brother is from Oaxaca.

Take care...

-> Now you have a friend in Mexico also.

RGDS
Pemo
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Old 2nd April 2012, 04:02 AM   #155
Pemo is offline Pemo  Mexico
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Quote:
Originally Posted by Aguilabrava View Post
Pemo:

One more question:

That small transformer, is it to power the speaker protection board only?

Thanks again...
There are TWO transformers (one on top of the other), One to power the pre-amp, the other to power the speaker protection board (that by the way, it really makes a difference)

RGDS

Pemo
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Old 2nd April 2012, 04:13 AM   #156
Pemo is offline Pemo  Mexico
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Default Photos of the pre-amp and usb dac boards

Here are some photos of the Mini USB PCM2704 DAC, and pre-amp that I use in this amp.
PCM2704BOARD.jpg

ne5532 preamp.jpg

RGDS

Pemo
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Old 2nd April 2012, 03:48 PM   #157
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Default Finally, I powered the amp....

AndrewT and Pacificblue:

I finally powered the amp yesterday. I installed everything on top of the old desktop computer. I used the 3 amp fuse, ON/OFF switch, pilot light, and the amp with a one LEFT and RIGHT input only. I connected a pair of speakers and an iPod with a 3.5mm to RCA stereo cable. I didn't use the speaker protection board because the seller indicated that it would work with 15 volts AC and anything over would damage it, I measured 16 volts coming out of the two additional secondaries in the toroidal, so I decided not to use it for now.

The sound is good, clean, even though all the wires inside are a mess, I don't hear any hum or any noises when powering ON and OFF. I left the R//L in the speaker lines as it is shown in the pictures.

The only problem is that the sound is not loud enough, it feels like something is chocking the amplifier, I have a little amp that I bought at eBay, a SMSL SA-S3 that uses a Tripath TA2021B chip, it fits in the palm of my hand and it sounds louder than this LM3886... It also sounds super clean.

Can you guys please help me figure out what is causing this problem?.

The amps heatsinks get hot, not too much, but it seems like if they were really working at their best, but for some reason the power doesn't reach the speakers.

I've just read the reply from Pemo, he used these boards unmodified and says his amp sounds fantastic, I upgraded all components using the best I could find and afford, and again, the sound is clear, but very low...

Thank you.
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Old 2nd April 2012, 03:52 PM   #158
AndrewT is offline AndrewT  Scotland
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What testing did you do before adding the speakers?

output offset
output noise
sinewave input voltage and corresponding output voltage.

What is the output voltage of your source?
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Old 2nd April 2012, 08:06 PM   #159
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AndrewT and Pacificblue:

Problem solved.

What was causing the huge lack of power was the volume pot, I had it wrong. After I posted here I did some research and realized I had the connection from the inputs, the ones going to the inputs in the amp and the grounds in the pot all wrong.

I desoldered them and resoldered according to what I found out and now this amplifier sounds beautiful, no noise, no hum, no distortion of any kind, just clean, well balanced sound coming from the speakers, and yes, very loud. Great bass, great treble, I am very happy, thank you very much to both of you, without your help this would've never been possible.

The only concern is that now the two heatsinks get so hot that I can't touch them with my finger for more than two seconds top, but I have had the amp playing music for longer than an hour, volume all the way up, and it is working fine.

The Thiele resistor//capacitor seems to be working perfect, again the sound coming from the B&W DM-220 speakers I'm using with it is just amazing. Obviously, in this case, theory and practice don't go absolutely together, I see no reason to replace any component.

Now, I will have to find the right enclosure to fit everything inside nicely and a better way to run the wires, I will post pictures later on today or tomorrow, I'm happy with the sound, in my opinion it couldn't sound better, but when I look at the wire mess I get a little disappointed.

Anyhow, THANK YOU VERY MUCH in capital letters to ANDREWT and PACIFICBLUE!!!
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Old 3rd April 2012, 04:24 AM   #160
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good to "hear"! looking forward to seeing it tucked away in a case! Also looks like I need to order a couple parts.
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