Q17 - an audiophile approach to perfect sound

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#1,081
smk7 said:
It works just as well with the LM49710. The tweeter is a bit bigger. Here the Opus can be used as an equalizer ))
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Well, good to hear some positive feedback. 👍
LME49710 is a modern and one of the best audio operational amplifiers. I would call it neutral.
In a very good audio system every component is audible and will leave his audio fingerprint. Operational amplifiers do NOT sound the same and you can use them to voice your amplifier.

Regards,
Tibi
 
#1,085
I retested the working board and I see around 312mV across R12 47/1W resistor and 283mV across R10 47/1W resistor with the offset remaining stable at 22mV. I checked now the offset between the circle output pad and the DC power input ground as the other speaker output pad is floating and not connected to anything as Tibi confirmed. Hope these values are good enough and I can hear the amp now on my test speakers.

Thanks
 
#1,091
manniraj said:
Did you mean R10 and R12 right which is 47 ohm /1W right?
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My mistake as I put a 100R resistor on the R13 instead of the 10R. After replacing I get around 3.15v and 3.16v across the R10/12. R3/150R I get around 377mV and then the R13/10R around 633mV.

Edit: I am using the 610/9610 instead of the suggested FQP mosfets for the information. So not sure if the IRF devices are making the lower R13 class A bias stage of around 377mV instead of the spec ~550mV as @stef1777 posted earlier.

Thanks
 
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#1,093
Thanks Tibi, right now the above my voltages are with the input signal being shorted. But tomorrow will test with a 100R resistor across the input pins and then check all the voltages again. My only discrepancies is across R3 I am getting only 377mV whereas R13 is around 633mV still not to your spec of ~550mV. Lets see if I can get it close to your published figures and then hear the amp once tomorrow 🙂
 
#1,098
I checked the hFe values of BS250 both of them and it shows around 617-622 on the board. I am yet to remove these from the board to test the Vbe using my LCR/mosfet tester. But in the meantime ordered few more pieces of BS250.
I ran this channel today and its playing beautifully irrespective of how the difference of voltages 😉
Felt this sounds a bit different with good bold voices or if I can say more warmer especially the mid range and I am loving it.

The other channel I lost both the high powered mosfets and now ordered new set need to wait for a week or so.

Thanks
 
#1,100
tvicol said:
If you like it in mono, than you'll love it in stereo. 🙂
Hfe on mosfet is a bit high to measure. 😉 Best tool to match and test a wide range of parts is something like this https://www.elektor.com/lcr-t4-mega328-transistor-tester-esr-meter

Regards,
Tibi
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Thanks Tibi, I have something similar measuring tool but to do that I need to remove both the BS250 transistors which i am not good at 🙂
Can we test these transistors with probes/wires when soldered to the board and the amp is switched off? Or the real/actual figures can be measured only when its out of the pcb board?
 
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