What exactly is the ultimate goal? If it's to maintain all functions of the amp - quite likely including on vintage pieces an RIAA phono equalizer/pre-amp stage, as well as a superfluous amount of input selection / tone controls / speaker switching VU/level meters, I suspect it won't be as simple as that.
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If you use an old component, you have all the power supply, fusing, filter cap location, rectiifer and input / outputs. You may also get VAS stage regulation and Phono stage regulation as in the SX-780. Here I got an excellent tuner as well.
A little ( easy ) mods to the main board and you have 120db of ripple rejection
The amp can be switched to Mosfet with little difficulty.
The Thing also looks better then any new box I could buy
A little ( easy ) mods to the main board and you have 120db of ripple rejection
The amp can be switched to Mosfet with little difficulty.
The Thing also looks better then any new box I could buy
Let's consider the sx780. It has +/-40VDC rails. You're at the limit of the lm3886 and the heatsink is really small, especially considering the high rails. Ok for 8R maybe, certainly not for 4R use. Maybe with a pair of ucd180 or similar. The power diodes are crap (2A rated) so you've got to change them too. The output relays are probably in dire need of replacement too.
Not impossible but certainly a bit involved.
Not impossible but certainly a bit involved.
940, A single LM3886 is unlikely to outperform sx780 w/mosfets instead of STK chip
the U shaped heatsink hardly gets warm after an hour of playing at 20w so it is okay. for 4 ohm loads it is small but then you need multiple 3886's if you go that route.
780 is also able to drive fets to rails using 42v on the regulated supply as the main supply drops to 35v under load. 22000 uf/ 50v filter caps also fit nicely in there.
6A bridge easily replaces main Diodes
the U shaped heatsink hardly gets warm after an hour of playing at 20w so it is okay. for 4 ohm loads it is small but then you need multiple 3886's if you go that route.
780 is also able to drive fets to rails using 42v on the regulated supply as the main supply drops to 35v under load. 22000 uf/ 50v filter caps also fit nicely in there.
6A bridge easily replaces main Diodes
The best way to modify a vintage amp into chip amp would be by incorporating a class D board..
But this thread is for chip amps... (Ive been told earlier above !)
Anyway I was thinking to start with LM3886 but I understood it has stability issues and I will have to use another one
For the moment I will make smaller project with TPA3116D2 and in the mean time
I will be searching to find another Vintage amp for this..modification
But this thread is for chip amps... (Ive been told earlier above !)
Anyway I was thinking to start with LM3886 but I understood it has stability issues and I will have to use another one
For the moment I will make smaller project with TPA3116D2 and in the mean time
I will be searching to find another Vintage amp for this..modification
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