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First LM3886 Gainclone Build - Need Guidance/Suggestions

avesbilal

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I refered to that LM3886 build link for calculations only.
Okay that is fine.

Which approach will give the most learning, building it myself or assembling a kit
Building it yourself will give you most learning, but you might not achieve desired performance from amplifier (Sound quality) in first attempt, and it is pretty hard to reach the level of Myref/Miniref as it is fine tuned by several experts.

The reason I'm looking at Lm1875 is because of fewer no. of pins as compared to Lm3886
According to me both LM3886 and LM1875 will have same complexity.

Also, for some reason I believe that I'll be able to put LM1875 together with a few trials.
If this is only for learning then go ahead.

The calculator link you shared needs total no. of watts and max peak to peak line voltages, so 185W and about 49Vdc - correct?
The link I provided we need to put in AC voltage, in your case it will be 30 VAC.


All this is with LM1875 & 15 0 15v transformer with calculations based on formulas given in the 3886 build link
If I were in your place I would go for 18-0-18 "120/150" VA transformer, as you will get higher wattage output from your amplifier which is always better.

This is just my opinion, I'm happy to stand corrected wherever needed.

Regards
Bilal
 
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novice-akki

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If I were in your place I would go for 18-0-18 "120/150" VA transformer, as you will get higher wattage output from your amplifier which is always better.

This is just my opinion, I'm happy to stand corrected wherever needed.

Regards
Bilal
Thanks for your suggestion, I read a few threads at diyaudio and in one of them our FM linuxguru recommends not going over +/- 24VDC and also from what I found at decibel dungeon. ~20W/ch from LM1875 is enough for me, as I already have a LM3886

Idea is try and follow a very simple P2P design that can be done with fairly less complexity and irrespective of the result build a next with a much better design available in form of PCB/kits.

BR,
Abhishek
 

avesbilal

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novice-akki

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The media player you are using already has a regulator on board,
Thanks for the info but just out of curiosity, how did you know?

hence you would need to Power it with 12vdc, just make a bridge rectifier and add smoothing capacitor, you are done.
Since I've a 0 12V trafo (without CT) wont the rectified supply be around ~16Vdc ?
Does this mean 16Vdc will be regulated to 12Vdc by the players on board regulator which's also the max dc voltage the player can accept?

If the above is true, can I use a 6 0 6Vac trafo as I've one from before ?

Also, please advise the most suitable trafo in this case and why it's been chosen, thanks !

BR,
Abhishek
 
Last edited:

avesbilal

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Thanks for the info but just out of curiosity, how did you know?
I can see the regulator on the board in the pic you provided, the black component in between two capacitors just beside the power input connector ( I have used such player which has similar components)


Since I've a 0 12V trafo (without CT) wont the rectified supply be around ~16Vdc ?
Does this mean 16Vdc will be regulated to 12Vdc by the players on board regulator which's also the max dc voltage the player can accept?
For finding it out if it can take 16vdc, you need to take the number of onboard regulator and check it's spects online, if it can take 16vdc you might need to add a small heatsink to this regulator (just to be safe)

Most of the time these sellers of such boards underrate the input supply voltage to be safe, however I advise you to double check before.


If the above is true, can I use a 6 0 6Vac trafo as I've one from before ?

Also, please advise the most suitable trafo in this case and why it's been chosen, thanks !
If you use 6-0-6vac transformer, you have to leave centre unused which will give you 0-12 with lesser amps.

If you can go for a different transformer then I would say go for 0-9 voltage so you get 12 vdc.



Regards
Bilal
 

novice-akki

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Yes, you are correct it has ST 78M05 in DPAK package between the two caps at dc input.

I checked the datasheet, there in the maximum input volatage rating section it says for Vo= 5 to 18V value 35 and for Vo= 20 to 24V value 40, unit V, please explain.

BR,
Abhishek
 

avesbilal

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Yes, you are correct it has ST 78M05 in DPAK package between the two caps at dc input.

I checked the datasheet, there in the maximum input volatage rating section it says for Vo= 5 to 18V value 35 and for Vo= 20 to 24V value 40, unit V, please explain.

BR,
Abhishek
You can use 16vdc directly to this board.


Regards
Bilal
 

HormusPeston

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Do you have a sound system that you use right now? If so, then read this: About 6 watts - diyAudio

Conducting the test described should furnish you with a good estimate of how much power you need. You might be surprised by the results!

Cheers,
~HP
 

novice-akki

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If you use 6-0-6vac transformer, you have to leave centre unused which will give you 0-12 with lesser amps.

Regards
Bilal
In this case, can we use half bridge/2 diodes and connect the extreme ends of 6 0 6v to half bridge rectifier.
Then the 2 ends of diode tied together will give +DC and 0/CT of transformer can be used as -DC/GND ??

maximum input volatage rating section it says for Vo= 5 to 18V value 35 and for Vo= 20 to 24V value 40, unit V, please explain.
Can someone please explain this part, especially value 35 & value 40 ?

Do you have a sound system that you use right now? If so, then read this: About 6 watts - diyAudio

Conducting the test described should furnish you with a good estimate of how much power you need. You might be surprised by the results!

Cheers,
~HP
Will read and come back with queries, if any.


Also, I made a full bridge rectifier by tying 4 diodes and adding a smoothing cap and a resistor with LED. Is there a tutorial to place/orient (lying next to each other) the 4 diodes on a PCB for aesthetic purpose, like this below ?

Capture.jpg
 
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kpsthakur

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Dec 27, 2015
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Hi,



That's a good chassis for a DIY project. You mentioned, you have purchased that LM3886 kit. good choice for a start if you are a novice.

Do you plan to have Bass/treble balance control integrated, in that case you would need a preamp. lots of designs out there.

Except from the chassis, transformer, knobs and connectors nothing else is usable from this amp, forget the power supply and ALL the capacitors.



If i were in your place, i would have rebuilt/refurbished the amp.



Good luck on your project.



Cheers!!!!

Aniket


Its sad to hear Woodstock was salvaged....a true classic crucified....it should have been restored...should have used the AUX port rather than tape player....had not much to worry..RIP
 
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