The LM1875 for best

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In single supply, the capacitor has 21v across. If I use higher value, the second order low cut becomes resonant. On document shown, low esr capacitor have higher distortion. I am counting on nonlinear character of MLCC capacitor to see if I can compensate inversely. By using a C meter on multimeter, I should be able to see with what ratio of elecrtoytic/MLCC I can render at 21v constant 330uF.
 
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Looking the above phase curve, the impedance is that of LCR with large Q, as it crosses without remaining 0° phase resistive. This might explain to those who don't understand why a low capacitive power supply is necessary. BTW, the 10uF on the 42V capacitor, should be 150uF for lower high frequency noise .
 

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It is possible to eliminate the capacitor, as shown above. Now, the low cut is highly resonant I must redesign the servo, the ground loop breaker is no more referenced and will inject all the noise to the input, the high frequency compensation must be different. Back to a forth round.
 

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The ground loop breaker is a big issue to have two grounds conflicting.
I looked to other amps as Krell, dadod's and Apex's CFA, they don't have any. The reason is simply cross talk between channels. So I decided also not to have ground loop breaker neither.
 

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I don't think that Modulus amplifiers BTL or PBTL are simple. DIYs who need simple can get for less than 2$ in kit form. When you consider the chassis cost and work needed, the PSU, switching 25$ or standard over 20$, one would like some more technology applied to his efforts. Yes it is more time for soldering the PCB, particularly the SMD section, but relatively to total time and money spent for the project, it is not much.
As stated on the first posts, TO220 amplifier species are on the verge of extinction, even no one would be interested to built this amp, it is left for posterity to show what could be done.
 
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The problem you or anyone potentially interested will have is executing a compact pcb layout.

Some of that difficulty could be relieved by buying kit modules for LM1875 of which you will need several to make a stereo amplifier. There are kits for the stereo version of this chip the LM1876 - for example see LM1876 60W Digital Amplifier Audio Board Dual Channel Amplifier Board for 4 8 ohm Speaker DIY/Finished Board B9 006|Amplifier| - AliExpress

You could use two kits to make a pair of bridge amplifiers with these.

The kit stereo pairs are non-inverting so you would need to use op.amps to invert the phase of one of each pair. The outputs have dc protection so you don't need to invert the wheel with separate discrete component design.
 
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I leave such possibilities to FauxFrench. As i already mentioned, I couldn't get as good sounding LM3886 in bridge as single, even with center tapped input transformer. If 4 lm1875 burn 40w /ch. at quiescent It must deliver as good sound as class A and this to 80W. This is the purpose of my amplifier.
 
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This the best layout I came upon. 42v and ground arrive at the center by twisted pair to link the heatsink by the ground to power the amps by the tabs. The 42v reach the amps by T as it conducts current on both polarities to be decoupled by Wima 10uf 50v PET capacitor which gets itls ground from the ICs. The supply feet holes of amps is oval to insert 100nf ceramic along the flat feet inserted from bellow, the 42v lead of the ceramic follows the foot up to the root of the IC.
 

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