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DIY-project with LM3886

post #1 of 27
Thread Starter 
Hi there!
I wanna built a solid amplifier with the LM3886.
It´s obvious I need a well dimensioned PS but
for what reason should I take one transformer for each channel?
I often read about this but really don´t see the point.
And what´s going on if the voltages of the transformers are slightly different? I actually don´t wanna build additional regulation.
Thanks a lot!
post #2 of 27
Check out this site for answers


and here

post #3 of 27
Thread Starter 
Hi there!
Thanks a lot for the links!
I knew I wasn´t quite right in this forum but it just sounded like somebody´s there who´s got enough knowledge to help.
I´m more experienced with TV´s so I sometimes don´t understand special circuits of hifi and also think they´re a little exaggerated.
So I asked before building.

post #4 of 27
See the attached Gif File, email me for futher info
post #5 of 27
Sorry forgot the Schemattic and board foil pattern. This pattern is the one i used and it works great. I have found this Chip is Ideal for a 30 Watt @8 Ohm & 60 Watt & 4 ohm. This requires a bouit a 150 Watt transformer. the DC Voltage should be + & - 25 - 30 Volts. The Chip will operate at Higher voltages but since my minimum criterioun for a loudspeaker amp is twice the power into 4 ohms than into 8 Ohms. This allows the Ability to Drive Complex Loads with out Current Limiting.
post #6 of 27
**** i gess i can only upload one Gif at a time so hears tthe Foil pattern at Twice the Required size use another Photo edit program to correct the size i used MS word. the Dim are in the small print on tthe foil Pattern . Also the Image is from the Foil side as was ihe Parts placement Image i posted at first.
post #7 of 27
Thread Starter 

DIY-project with LM3886

Thanks a lot for the schem and PCB.
I already had a schematic and a PCB from a real good german magazine for electronic stuff.
My only concern was if one transformer is enough.
From your description and from my thoughts as well and I think one solid transformer should do.
Really interested about the result.
Did you built this by the way?
And did you do something about tone control etcpp.?

post #8 of 27
Yes i Built this with some Modifications.(TONE CONTROL'S, ISENT THIS HIGH END DIY AUDIO?): jUST KIDDING.

i built mine using Dual mono Construction (2) Plitron 160 watt troidial transformers.(tested prototype with 56 watt split bobbin type sounded ok. But replacing with plitrons Boy what a DIFFERENCE. everything improved including the soundstage that i did not expect.. IT is upon a 6" X 6" Ground plained Teflon Board. A c Channel runs down the center to serve as Heat transfers to the Top of the Aluminium Cabinet. Way Cool Will try and get Photo's.

The power supply is also no compromize using Kevins ULTRAREGULATOR and (4) more LM-3886's as the power opamp for this. The logick hear is as long as the Regulator has the Same Bandwith as the Audio Circuitry All should be good sonicily since the sound Qualities of the Amp and the Power sypply are similar by virtue of The semmitry Created by using the Same drvices in Both power and Gain Circuits. on the Input to the SUPPER REGLATOR are (4) 25,000uF Low ESR 105 deg. electrolytics. Following The ULTRAREGULATOR are Three levels of Bypassing A 1.0uf Wimi Polypropylene Box type, Augmented with 0.1uF POLYSTYRENE.

So as you might Gather i expected Great results but since i have not heard these Chips this would be a good project to test them out. And i was not Dissipointed Eassly outperfors Sonicly a couple of GAINCARD clones i compaired it to.

This Amp is now my OFFICIAL Computor Amp. Evean for Headphones. Ya Know MR Apahreared 20 Watts really Kicks But bith Gradios talk abut Dynamics. Strangly enough the Bandwidth and slew rate of the LM-3886 is not Bad for a power opamp Better than one Burr Brown Type i am thinging of. OH dont forget those ALPS BLACK BEAUTIES.

post #9 of 27
The attached gif is a photo fr the Auctual board as dipicted in the Above Gif files.
post #10 of 27
Thread Starter 

any suggestions for preamp

Thanks again for all the information.
Because you actually built this I´m really interested which preamp or tone controls you realized with that amp.
I´m just too lazy and don´t have the money to experiment too much around so
Do you have a circuit of your preamp/tonecontrol you could send?
Or any suggestions or projects on webpages for something that would match the LM3886?
I intended to build something very straight (few parts,small); just tone control and about 4 inputs and a headphoneamp which is done.
The fewer the parts the better.
Thanks for any advices!

post #11 of 27
I have not used tone Controlls with this Amp Nor a preamp Because the gain of the Circuit showen can be raised to not need a preamp. Just hang a Volume control on the input. If i were to use tone controls i would put them in the Feedback loop of the LM-38886 so as to not make the signal to go through more parts. But since My SB line card has tone controls i can use them if needed. A headphone jack can be installed by using one with switched contacts to disconect the speakers when the Phones are inserted. thats what i did. I do have tone Controls and voilume Controls on file but after several attemps at uploading that failed i give up email me. but i Must Caution I have not built the tone control circuits since i dont like electronic Volume, Bass and treble Controls.
post #12 of 27
Thread Starter 
Thanks for the fast answer (vroom).
After thinking about it I should just finish the amp and see how that thing sounds.
It was my intention to keep it simple and straight but sometimes you have to compense bad recordings a little.So.
I thought a little control would help but probably I´ll leave it.
It´s the same with the headphone amplifier I built.
It´s the one form Earle Eaton.It´s wonderful but when you´ve got a strange recording it sounds too aggressive too trebly or whatever.
Maybe send you mail if I get inspired too do more about the amp.
Thanks again and greetings
post #13 of 27
I have noticed this same quality in all Good Amps. But the Effect of Highlighting the bad artifacts in poor recordings rather than just reproduce what is thair is what Poor quality amps Do. A highly accurate Amp and Transducers will allow you to hear well into the Mix and in that mix is at times some nasty things you may not like to hear, This quality is the ability to capture Detail. Now a bad Amp or Tranducers that are prone to Ring will Increce the apparent Level of those nasties and put them right in your face rather than just reproduce them in the Correct perportion. Alot of High End Amps and transducers Roll off the Highs or delete the Detail so as to present both Bad as well as good recondings in an equaly Sterle and Striped-down presentation, This is done so No one will be offended by any sound that comes out, thay just roll off all the Hights on everything so that all recordings sound the same.
post #14 of 27
joensd: Did you ever Build this amp what did it sound like?
post #15 of 27
Thread Starter 
Hi ppl!
Now I actually have all the parts I need but didn´t start with the circuit itself.Still woffling about the case, cause I didn´t want to buy one.Also still unsure about the cooling cause I got only two heatsinks with about 7-8K/W and I don´t know if it´s enough if I link them with the case.
I took a finished PCB from ELV cause it was damned cheap.
A toroidal trannie with 220VA and 18V secondary which will hopefully cool with 8Ohms and with 4Ohms as well.
I´ll give report about the finished amp and if you´re interested I can send out the specific circuit I used.
What are you doing by the way. Are you only building stuff you need yourself or are you experimenting alot and just doing it for fun (for your ears)?
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