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#21 |
diyAudio Member
Join Date: Sep 2003
Location: Liège
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If you have lm1875 in stock, why not. I'm genuinely curious to see how you will manage the composite things. That's something I've recognized above my own skills.
Good luck with the project.
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All that is excessive is insignificant. Talleyrand |
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#22 |
diyAudio Member
Join Date: Dec 2017
Location: The mountains, calm and quiet.
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#23 | |
diyAudio Member
Join Date: Jan 2017
Location: Vienna
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Quote:
Yes 00940... i read a lot and with this "project" you will not learn much by me ![]() chris |
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#24 |
diyAudio Member
Join Date: Jan 2017
Location: Vienna
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Hi
to be clear which supply voltage we should have for 4 R load i did a test again. to get 3Amps aout we need at 4,459R a Voltage rms about 13,37V at the resistor. i use 25V supply but with the with 450mVrms i get this current limiter. switch on_off_ on off --> i show this in the LM1875 kit thread. i go dwon with the supply 20V - this is the max off Voltage of the chip to do not go into the limiter. and here are the results: pic 1 +/- 20V supply 500mVrms in (G=27dB) 11,2 Vrms at the load of 4,459R -- clipping pic 2 +/- 20V supply 480mVrms in (G=27dB) 10,6 Vrms at the load of 4,459R -- clipping pic 3 +/- 20V supply 460mVrms in (G=27dB) 10,2 Vrms at the load of 4,459R -- no clipping - this give us a current of 2,287Amps continuous pic 4 +/- 15V supply 460mVrms in (G=27dB) 9,3 Vrms at the load of 4,459R -- clipping - supply voltage too low pic 5 +/- 18V supply 460mVrms in (G=27dB) 10,1 Vrms at the load of 4,459R -- clipping - supply voltage too low - closed to 20V supply but not enough this give us a current of 2,265Amps continuous pic 6 is the test enviroment - idle - no signal so we should calculate per chip at 4R with 2,2 continuous? chris Last edited by chermann; 14th December 2019 at 04:52 PM. |
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#25 |
diyAudio Member
Join Date: Jan 2017
Location: Vienna
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here is a summarize of that test
if you look at pic 3 and pic 5 you can see that the formula - look at the Vpp Vout = Vsupply - 10V is correct!!! |
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#26 |
diyAudio Member
Join Date: Dec 2017
Location: The mountains, calm and quiet.
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Good work as usual, Chris. The current limit kicks in at 2.3Arms corresponding to 3.25Apeak. I assumed use to 3Apeak in the initial estimations so that wasn't completely wrong.
Was this an Amazon chip or a genuine TI chip? |
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#27 | |
diyAudio Member
Join Date: Jan 2017
Location: Vienna
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Quote:
![]() if i did no mistake at my workbench.... ![]() original TI chip...to confirm this test i will do this test with my amp boards = amp 1_2 the nichicon UES board.... |
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#28 |
diyAudio Member
Join Date: Jan 2017
Location: Vienna
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Hi FF
according to post 9 If we limit the supply voltage to +/-25V such that we can expect output signal clipping at 20V, the output power calculations become: SE-coupling: 25W in 8 Ohm. SE-coupling: 50W in 4 Ohm. BTL-coupling: 100W in 8 Ohm. BTL-coupling: 133W in 6 Ohm. BTL-coupling: 200W in 4 Ohm. Still respectable values. what about the Transformer ratings? 2x15VAC - 160VA-200VA -230VA for both channels chris |
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#29 | |
diyAudio Member
Join Date: Dec 2015
Location: south east asia
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Quote:
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#30 |
diyAudio Member
Join Date: Dec 2015
Location: south east asia
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here is a first approach for composite .
Last edited by kokoriantz; 14th December 2019 at 09:16 PM. |
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