Hi Andrew, this is Pemo again.
Would you please tell me if this C32 + R42 is a Zobel in this design?
Is the Thiele missing?
What is this LM318 for?
Best regards
View attachment LM3886 �声�.pdf
Would you please tell me if this C32 + R42 is a Zobel in this design?
Is the Thiele missing?
What is this LM318 for?
Best regards
View attachment LM3886 �声�.pdf
670 mA into 8 Ohm corresponds to 3,6 W. From that power level upward it is likely that the sound quality will suffer with that inductor. That is more power than you usually need continuously, but with 40 V rails the amp can deliver 20 times as much.
Andrews advice to wind your own is the easiest, cheapest and fastest solution, if you find that the sound quality decreases at higher volume. If you want to replace the inductor with a commercial one, look for ferrite types and make sure the saturation current is 7 A or more.
Luxurious space for the amp. It will need some holes for air circulation, especially if you put the heatsink size in relation to your highish rail voltage. The isolated LM package limits the heatsinking capabilities, too. Should the amp run into thermal protection, consider replacing the LMs with the non-isolated package and reducing the rail voltage.
Andrews advice to wind your own is the easiest, cheapest and fastest solution, if you find that the sound quality decreases at higher volume. If you want to replace the inductor with a commercial one, look for ferrite types and make sure the saturation current is 7 A or more.
Luxurious space for the amp. It will need some holes for air circulation, especially if you put the heatsink size in relation to your highish rail voltage. The isolated LM package limits the heatsinking capabilities, too. Should the amp run into thermal protection, consider replacing the LMs with the non-isolated package and reducing the rail voltage.
Hi Pemo,
Your answers are here: http://www.diyaudio.com/forums/chip-amps/54571-my-audiophile-lm3886-approach.html
You can also ask in that thread, whether that seller has permission to sell that design or parts of it.
Your answers are here: http://www.diyaudio.com/forums/chip-amps/54571-my-audiophile-lm3886-approach.html
You can also ask in that thread, whether that seller has permission to sell that design or parts of it.
Diam. 8 mm
15 turns
1.5 mm copper
= 0.7 uH
Diam. 6.5 mm
13 turns
1.5 mm copper
= 0.45 uH
Diam. 13 mm
15 turns
1.5 mm copper
= 1.48 uH
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Hi Pacificblue:
I was checking the electronics component catalog online, the closer match to the 1.5uH inductor is a API Delevan with 5.2 Amps of current saturation, 11 mOhms of DC resistance. They do not show any axial inductors with 7 amps of current saturation, this one seems to be the biggest one in that respect. The part number is API Delevan 2474R-03L, it is available at www.digikey.com . Please let me know if this would work.
If not, I will have to test the amp as it is right now, if the quality of sound is not good, I'll try AndrewT's solution. I just don't feel like playing with copper wire, I'm afraid is not going to come up the right way...
Regarding the heatsinks, do you think those in the picture are not big enough?.
Thank you again.
In theory, yes. In practice you will have to test it, because the high Q factor could lead to ringing.
Omitting the resistor and the parallel inductor will not have audible effects. Those components only protect the amplifier from overload, when you connect capacitive loads.
Andrew's solution will not have audible effects either. It is proven practice to do it like that, and you can't make much wrong there.
The solution with the core inductor will have audible effects, when the core runs into saturation, and it could have audible effects due to the Q factor, but that remains to be tested.
The bigger issue will be the isolated LM package that has a higher thermal resistance than the non-isolated version. Even for 8 Ohm loads your rail voltage is quite high and you can expect ~40 W of worst case power dissipation. Even if the heatsinks are big enough, the amp may not be able to transfer the heat to the heatsinks.
The heatsinks themselves will work well outside of a case, where you can expect 20-25 °C ambient temperature. Depending on your listening habits they may or may not work inside of a case. Inside of a case the temperatures will be higher, that is why you should at least make some holes or connect the heatsinks thermally to the case, so that the case itself helps with heatsinking.
AndrewT:
I have a question regarding the GRD's in the amplifier. In the PSU, in the DC side I have three connections, +V GRD -V. From what I have been reading, I only connect the +V and -V to each amplifier, then run 2 wires from them to the star point of the ground where they will meet the cable coming from the PSU GRD terminal. Is this correct?. Then, from the Output speaker terminals attached to the chassis, I run one wire from each terminal to that same star spot.
The safety GRD, the one that comes from the wall's mains goes to the chassis at a different location, it doesn't join the rest of grounds that will form the star, right?.
The purple shield wire from the transformer gets attached to the chassis at a different location, no star ground spot, no safety ground from wall's mains.
Please let me know if this is correct.
I have a question regarding the GRD's in the amplifier. In the PSU, in the DC side I have three connections, +V GRD -V. From what I have been reading, I only connect the +V and -V to each amplifier, then run 2 wires from them to the star point of the ground where they will meet the cable coming from the PSU GRD terminal. Is this correct?. Then, from the Output speaker terminals attached to the chassis, I run one wire from each terminal to that same star spot.
The safety GRD, the one that comes from the wall's mains goes to the chassis at a different location, it doesn't join the rest of grounds that will form the star, right?.
The purple shield wire from the transformer gets attached to the chassis at a different location, no star ground spot, no safety ground from wall's mains.
Please let me know if this is correct.
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...
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...
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
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.
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.
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!!!
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!!!
good to "hear"! looking forward to seeing it tucked away in a case! Also looks like I need to order a couple parts.