Hi
measured direct on the +V -GND -V terminals at the amp board.i add 3300µF on each rial.is not better 100Hz ripple with 188mV -before 220mv...so more caps = ripple gets down
.....i will have a closer looka t my space in my mock up /housing
maybe rabbitz your are interesting to add some more caps ?...and report back about the changes = SQ
pic 1 +V
piv 2 -V
chris
measured direct on the +V -GND -V terminals at the amp board.i add 3300µF on each rial.is not better 100Hz ripple with 188mV -before 220mv...so more caps = ripple gets down
.....i will have a closer looka t my space in my mock up /housingmaybe rabbitz your are interesting to add some more caps ?...and report back about the changes = SQ
pic 1 +V
piv 2 -V
chris
Attachments
Chris
I now use a supply with 50VA 18-0-18 and 2/4700uF caps (first pic). I can try the supply I use on the LM4780 which is 120VA 18-0-18 and 2/10000uF caps (second pic).
I'll have a listen over the next few days and see if there is a difference.
You are certainly getting into this. I just build and then listen and if it sounds good all is well. If not, it gets binned.
I now use a supply with 50VA 18-0-18 and 2/4700uF caps (first pic). I can try the supply I use on the LM4780 which is 120VA 18-0-18 and 2/10000uF caps (second pic).
I'll have a listen over the next few days and see if there is a difference.
You are certainly getting into this. I just build and then listen and if it sounds good all is well. If not, it gets binned.
Attachments
yesterday i want to order the chips over the TI shop.
20 pcs -- with delivery 6,99 and TAX 18,55 !!! i should pay 84 euro !!!
sorry guys thats not acceptable !
over digikey i have 20psc about 52 euro - deliver cost not inluded but normally 20% = 64 euro !
chris
Today arrived TAX 11,60 +52 parts = 64 euro for 20pcs
Wow, that is definitely to much for my small purse.
It seems quite a challenge to get original LM1875 for a fair price. sad.
interesting too should be what happened if you add caps at the V+ - 0 - -V Terminals
That's how mine was originally built as there was additional caps near the amp boards as I was using an umbilical cord between the power supply case and amp case. I thought it was causing the pop at power down so was removed. AFAIR there didn't seem to be a difference in sound quality with or without.
I tried the two power supplies today.
50VA 18-0-18 4700uF: An up front presentation with a bit of excitement and bite with a strong bottom end which is I feel is bloated. Seems to have more sibilance than other amps I have.
120VA 18-018 10000uF: Loses some excitement, but smoother and the bottom end appears to be better controlled but less strong. Sibilance is still the same.
Tried with two different pre amps but both are LM4562 based. A passive pre was also tried and that lacked control. Speaker was a small SB26STAC/NE123W 2-way.
I then tried my crappy LM4780 which was much better overall and then a P19 which was better again. Even threw a TPA3116D2 into the mix and faired better than the LM1875 on sibilance.
I've had a look at a few more PCBs on ebay but they seem to be a bit iffy. I do have 2 chips left so might try Beginner's Gainclone or a ESP P72.
50VA 18-0-18 4700uF: An up front presentation with a bit of excitement and bite with a strong bottom end which is I feel is bloated. Seems to have more sibilance than other amps I have.
120VA 18-018 10000uF: Loses some excitement, but smoother and the bottom end appears to be better controlled but less strong. Sibilance is still the same.
Tried with two different pre amps but both are LM4562 based. A passive pre was also tried and that lacked control. Speaker was a small SB26STAC/NE123W 2-way.
I then tried my crappy LM4780 which was much better overall and then a P19 which was better again. Even threw a TPA3116D2 into the mix and faired better than the LM1875 on sibilance.
I've had a look at a few more PCBs on ebay but they seem to be a bit iffy. I do have 2 chips left so might try Beginner's Gainclone or a ESP P72.
Hi Rabbitz
thanks for your time and do these tests.
SB26STAC/NE123W 2-way.
thats fine for compare sessions
120VA 18-018 10000uF: Loses some excitement, but smoother and the bottom end appears to be better controlled but less strong. Sibilance is still the same.
loses some excitements,.... for me its important to have the vocals and instruments not thrown to the listening position...this give me the advantage of better "holographic" overview, for the deepness too.
i have no preamp - after testing directly my DAC (Gustard A20) an my power amp years ago i sell my recovered Accuphase C200V. now i play my DAC´s directly in the power amps.
I then tried my crappy LM4780 which was much better overall and then a P19 which was better again. Even threw a TPA3116D2 into the mix and faired better than the LM1875 on sibilance.
i do not have an other chip amp to compare. P19 is the LM3886?
Single Chip 50W Stereo Amplifier
with my 3116D2 dual chip i am not so happy. the TPA3255 amp (fake amp) is now my best one!..myLM1875 is not sooo far away (actually i add a 220n +R10 zobel at the speakers terminal)
I've had a look at a few more PCBs on ebay but they seem to be a bit iffy. I do have 2 chips left so might try Beginner's Gainclone or a ESP P72.
72 is a LM1875 project...P72 is what ?
thanks rabbitz
chris
thanks for your time and do these tests.
SB26STAC/NE123W 2-way.
thats fine for compare sessions
120VA 18-018 10000uF: Loses some excitement, but smoother and the bottom end appears to be better controlled but less strong. Sibilance is still the same.
loses some excitements,.... for me its important to have the vocals and instruments not thrown to the listening position...this give me the advantage of better "holographic" overview, for the deepness too.
i have no preamp - after testing directly my DAC (Gustard A20) an my power amp years ago i sell my recovered Accuphase C200V. now i play my DAC´s directly in the power amps.
I then tried my crappy LM4780 which was much better overall and then a P19 which was better again. Even threw a TPA3116D2 into the mix and faired better than the LM1875 on sibilance.
i do not have an other chip amp to compare. P19 is the LM3886?
Single Chip 50W Stereo Amplifier
with my 3116D2 dual chip i am not so happy. the TPA3255 amp (fake amp) is now my best one!
..myLM1875 is not sooo far away (actually i add a 220n +R10 zobel at the speakers terminal)I've had a look at a few more PCBs on ebay but they seem to be a bit iffy. I do have 2 chips left so might try Beginner's Gainclone or a ESP P72.
72 is a LM1875 project...P72 is what ?
thanks rabbitz
chris
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Yes, the P19 is LM3886. I also have a Neurochrome 3886DR.
I tried several TPA3116 and the only one I liked was the blue/black designed by Danzz (see pic). All the rest had issues such as hiss, noise or failed.
P72 is ESP Project 72. There are several dual PCBs on ebay like the one in the pic but not ideal.
I tried several TPA3116 and the only one I liked was the blue/black designed by Danzz (see pic). All the rest had issues such as hiss, noise or failed.
P72 is ESP Project 72. There are several dual PCBs on ebay like the one in the pic but not ideal.
Attachments
Hi
the red 10µ 16V electrolytic cap is definitively junk! - this is maybe the reason of bloated/strange bass.
from 10 Hz up to 100 Hz i have a lower gain (look at the scope Voltage)and at 10Hz the signal is really strange. at the pdf file you can see the ESR + ESL measurements --> this cap is junk!!
generally i see at 10-400hz a phase shift which changed from14khz to 19 khz to the other direction.
a sane cap looks fine
last pic at 10hz
chris
the red 10µ 16V electrolytic cap is definitively junk! - this is maybe the reason of bloated/strange bass.
from 10 Hz up to 100 Hz i have a lower gain (look at the scope Voltage)and at 10Hz the signal is really strange. at the pdf file you can see the ESR + ESL measurements --> this cap is junk!!
generally i see at 10-400hz a phase shift which changed from14khz to 19 khz to the other direction.
a sane cap looks fine
last pic at 10hz
chris
Attachments
Chris, I guess it is the capacitor in the string from the inverting input of the LM1875 and to signal ground? If so, would you have a bi-polar Nichicon or Elna capacitor to replace it with? This capacitor risks being reverse biased and that may disturb your low bass.
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I found it worse with the passive pre with a 50K pot. Really bloated and lacked control. The active pre amps (Zout 100R) were much better and controlled.
I think the red input cap is a fake Elna. I used a film in this location but didn't try a Nichicon ES.
hi FF
No i mean the input red cap. but maybe your are right too - the feedback cap is a 47µF fake nichicon gold....whatever
actually i made other 2 boards - amp 2, with a 4,7µ wima + ES 22µ in the FB + a hugh cap(1000µ) at the rail....see pics..i soldered because the terminals are junk. the 2 new chip by digikey are fine...shortcut test sucessfully done .
i want to check a complete different setup against the original parts.
chris
Attachments
...with and without extra zobel 220nF + 10R
Good morning again
with this amp1 (bad caps) i did a frequency response with 8 R both channels and 100mVrm input - with extra zobel or not. i expected the same effect as at class D but it isn't really- sound wise yes..little bit better....but with this kit parts i will not investigate more time.
in the low area- bass - i lost 7 db! i comment the phase shift - just in a small area 5k-8 kHz i have no phase shift between input and output signal...
next will be the new boards amp 2
chris
Good morning again
with this amp1 (bad caps) i did a frequency response with 8 R both channels and 100mVrm input - with extra zobel or not. i expected the same effect as at class D but it isn't really- sound wise yes..little bit better....but with this kit parts i will not investigate more time.
in the low area- bass - i lost 7 db! i comment the phase shift - just in a small area 5k-8 kHz i have no phase shift between input and output signal...
next will be the new boards amp 2
chris
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amp 1 gets an upgrade...
Good Evening
i changed my mind and use the amp1 kit and solder the bad caps out and solder nichicon green ES 10µF as input cap and a 100µ as NFB cap. additionally i solder all other in/out because of the fiddly terminals. lets see tomorrow and the next days if i am finished with the second side and some hours "burn in"
chris
Good Evening
i changed my mind and use the amp1 kit and solder the bad caps out and solder nichicon green ES 10µF as input cap and a 100µ as NFB cap. additionally i solder all other in/out because of the fiddly terminals. lets see tomorrow and the next days if i am finished with the second side and some hours "burn in"
chris
