I tried 20k pot but no luck sir, same volume 😕
Can you suggest me preamp that will be dit for the job sir ?
Here i attach the board layout, what sould i change ?? Input cap are 475 but i cant find it so i change with 225,
Attachments
Hi,
I would try increasing the rails voltage from 18-0-18 to 32-0-32. It would give you more output power. I my LM3886 built I used 38-0-38. It is the max you can go with the LM3886. Also the output depend on the input voltage.
I would try increasing the rails voltage from 18-0-18 to 32-0-32. It would give you more output power. I my LM3886 built I used 38-0-38. It is the max you can go with the LM3886. Also the output depend on the input voltage.
It is usually safe to INCREASE the gain of a power amplifier when it has simple stability compensation.
Generally one should NOT decrease the gain. A DECREASE in gain can seriously reduce the stability margins and that could destroy your amp and/or speaker.
Swapping in a lower value for the lower leg feedback resistor will increase the gain. Don't go above 40times for gain. Instead of swapping the resistor you can add a second resistor in parallel.
If you have a 1k at present then adding a 3k3 effectively lowers the pair to 705r
or use a 2k2 to give an effective 688r
Generally one should NOT decrease the gain. A DECREASE in gain can seriously reduce the stability margins and that could destroy your amp and/or speaker.
Swapping in a lower value for the lower leg feedback resistor will increase the gain. Don't go above 40times for gain. Instead of swapping the resistor you can add a second resistor in parallel.
If you have a 1k at present then adding a 3k3 effectively lowers the pair to 705r
or use a 2k2 to give an effective 688r
Hi all,
Just finished making my subwoofer amplifier, already make the case too! Tomorrow will work for the sub filter with NE5532 from xtronic (already make sub filter with 4558 but it sounds terrible), for the power amp im using Sanken 2SA1494 & 2SC4858 for 100watt RMS at 8ohm driver, i hope it will drive my 8inch sub nicely, the power amp i got layout from videorockola. That site is amazing!
Will work center amp soon (single LM1875 maybe?)
I hope can put center amp in one case with 5.1 decoder
Im looking for 5.1 decoder layout but i cannot find them anywhere, is that mean i must buy the peoduct like YAMAHA/onkyo? That will cost hundreds of Dollars 🙁
Thats too huge for student like me
Cheers!
Bobby.
38vac mean 53vdc, i must change all my electrolytic cap, mine only 50v rated, but using 53vdc at each rail mean 106volts around the chips, max voltage lm3886 is only 80volts! Cmiiw
Will change the input cap when i get the replacement thanks for suggeesting 😀
Will do sir, will report after the change
1k parallel with 3k3 = 2150r, am i correct sir ?
Just finished making my subwoofer amplifier, already make the case too! Tomorrow will work for the sub filter with NE5532 from xtronic (already make sub filter with 4558 but it sounds terrible), for the power amp im using Sanken 2SA1494 & 2SC4858 for 100watt RMS at 8ohm driver, i hope it will drive my 8inch sub nicely, the power amp i got layout from videorockola. That site is amazing!
Will work center amp soon (single LM1875 maybe?)
I hope can put center amp in one case with 5.1 decoder
Im looking for 5.1 decoder layout but i cannot find them anywhere, is that mean i must buy the peoduct like YAMAHA/onkyo? That will cost hundreds of Dollars 🙁
Thats too huge for student like me
Cheers!
Bobby.
38vac mean 53vdc, i must change all my electrolytic cap, mine only 50v rated, but using 53vdc at each rail mean 106volts around the chips, max voltage lm3886 is only 80volts! Cmiiw
Will change the input cap when i get the replacement thanks for suggeesting 😀
Will do sir, will report after the change
1k parallel with 3k3 = 2150r, am i correct sir ?
Attachments
you need to change the batteries in your calculator.
1k||3k3 must be less than 1k
It cannot be higher than 1k
Hi all
Here's some update, i tried to increase the gain but its end with no good result, change the input cap to its writen to the layout (4,7uf non polar), decrease the input resistor from 1k to 680 ohm, & make ac voltage from 18-0-18 to 24-0-24, first i connect it (without bulb test), 2 of negative rail fuses from front amp is pop out, i change all fuse from 2A rated to 3A rated and its all good, working with higher & louder sound! But i hear hum when it idle & even when it work in low volume, will change back the resistor to 1k tomorrow, maybe its now in unstable state as AndrewT said.
(Why tomorrow its just 4 resistors you sleepyhead!, wait it took me 45-60 minutes for change only 4 resistors, its because i must disassemble all the wire, star grounding, fuse holder, psu & protector wire, then i can remove the power amp section, im using glue to some of these parts, that make it harder).
Getting no luck with xtronic sub filter, its not producing sound at all maybe cause by bad NE5532 chips that i get from my friend, just knowing all pinout is shorted after test (used chip, hard to find NE5532 here).
Now im waiting my babies for coming from another realm (5.1 decoder & some LM1875 chip), hope they dont take forever.
Best.
Bobby
Yep, im just ordered decoder called "audio gear" thats 5.1 decoder (they said), its just -+$20, cant wait! 😀
Ouch im using same formula with parallel same value resistors, my bad sir
Now im using 24vac and yeah! hear its a bit louder 😀 (dont have db meter)
Here's some update, i tried to increase the gain but its end with no good result, change the input cap to its writen to the layout (4,7uf non polar), decrease the input resistor from 1k to 680 ohm, & make ac voltage from 18-0-18 to 24-0-24, first i connect it (without bulb test), 2 of negative rail fuses from front amp is pop out, i change all fuse from 2A rated to 3A rated and its all good, working with higher & louder sound! But i hear hum when it idle & even when it work in low volume, will change back the resistor to 1k tomorrow, maybe its now in unstable state as AndrewT said.
(Why tomorrow its just 4 resistors you sleepyhead!, wait it took me 45-60 minutes for change only 4 resistors, its because i must disassemble all the wire, star grounding, fuse holder, psu & protector wire, then i can remove the power amp section, im using glue to some of these parts, that make it harder).
Getting no luck with xtronic sub filter, its not producing sound at all maybe cause by bad NE5532 chips that i get from my friend, just knowing all pinout is shorted after test (used chip, hard to find NE5532 here).
Now im waiting my babies for coming from another realm (5.1 decoder & some LM1875 chip), hope they dont take forever.
Best.
Bobby
Yep, im just ordered decoder called "audio gear" thats 5.1 decoder (they said), its just -+$20, cant wait! 😀
Ouch im using same formula with parallel same value resistors, my bad sir
Now im using 24vac and yeah! hear its a bit louder 😀 (dont have db meter)
Attachments
Last edited:
Im using fast blow, slow blow are rare here, can only get at online dealer its cost 10-20 times than fast blow, like $2,5 each when fast blow i can get 30pcs with $1
, same amperage rateHi
Just recieve the package, that contain 5.1 decoder, 4xlm1875, 2x LG 3" speaker, 1x ACR Tweeter, fan, heatsink & sack of RCA connector, will start to build my center amps, i noticed they damaging the surface of 5.1 processor SMD chips, so we can not see what chips that they use, i spot some 4558 in smd form at the board too! I wonder can i replace it with SMD NE5532, in last project my preamp are WAY BETTER using NE5532 than 4558. Wish me luck! (Finger crossed)
Best.
Bobby
Just recieve the package, that contain 5.1 decoder, 4xlm1875, 2x LG 3" speaker, 1x ACR Tweeter, fan, heatsink & sack of RCA connector, will start to build my center amps, i noticed they damaging the surface of 5.1 processor SMD chips, so we can not see what chips that they use, i spot some 4558 in smd form at the board too! I wonder can i replace it with SMD NE5532, in last project my preamp are WAY BETTER using NE5532 than 4558. Wish me luck! (Finger crossed)
Best.
Bobby
Attachments
- Status
- Not open for further replies.