Hi,
Has anyone tried the basic bridge/parallel circuit for LM3886 as shown in Figure 17 at http://www.national.com/an/AN/AN-1192.pdf (page 15). I need at least 175W RMS of clean power for a sub. I intend to use 4 ICs or maybe 6 for a 4 ohm 12" driver.
What should be the supply voltage?
Thanks in advance,
Goldy
Has anyone tried the basic bridge/parallel circuit for LM3886 as shown in Figure 17 at http://www.national.com/an/AN/AN-1192.pdf (page 15). I need at least 175W RMS of clean power for a sub. I intend to use 4 ICs or maybe 6 for a 4 ohm 12" driver.
What should be the supply voltage?
Thanks in advance,
Goldy
Go here :
http://www.diyaudio.com/forums/showthread.php?s=&threadid=11133&highlight=bridgeclone
(where I used Zobel & snubbers & plenty more tricks...)
Arne K
http://www.diyaudio.com/forums/showthread.php?s=&threadid=11133&highlight=bridgeclone
(where I used Zobel & snubbers & plenty more tricks...)
Arne K
For a bridge-parallel design (with 4 amps) the equivalent load that each amp sees is equal to the real load impedance, or 4 ohms. For a 4 ohm load, the "sweet spot" in power supply voltage is about +/- 28V. Go any lower, and the power output decreases. Go any higher, and the power dissipation increases too high.I need at least 175W RMS of clean power for a sub. I intend to use 4 ICs or maybe 6 for a 4 ohm 12" driver.
What should be the supply voltage?
How much offset is safe?
Hi,
I intend to use only a pot at non inverting input to reduce the offset. But as I read in other threads, it will not reduce it beyond a point. How much of offset voltage is safe if I use 0.22 ohm at the output of each LM3886? The number of chips per side of the speaker is 3 (total of 6). The supply is 28-0-28.
Thanks in advance,
Goldy
Hi,
I intend to use only a pot at non inverting input to reduce the offset. But as I read in other threads, it will not reduce it beyond a point. How much of offset voltage is safe if I use 0.22 ohm at the output of each LM3886? The number of chips per side of the speaker is 3 (total of 6). The supply is 28-0-28.
Thanks in advance,
Goldy
I built mine without servo, and just to share what i learned:
1. Resistor matching is important. Be friendly with the store owner and they will let you spend a day in the store selecting your resistors.
2. Chips has 'internal offset', so build a few to select the ones with the least offset.
My sub amp has dc offset of about 200mV (I didnt observe rule #2) But for a 200-watter, I dont really care. There is more than enough power to dispense and my sub can take that.
1. Resistor matching is important. Be friendly with the store owner and they will let you spend a day in the store selecting your resistors.
2. Chips has 'internal offset', so build a few to select the ones with the least offset.
My sub amp has dc offset of about 200mV (I didnt observe rule #2) But for a 200-watter, I dont really care. There is more than enough power to dispense and my sub can take that.
I agree with skyraider"s two points.
I used trim pot on the non inverted inputs.
I built 20 indepentent modules. I picked 16 modules with the closest dc offset,then I broke that group into four group all with dc matched as close as possible. I ended up with four nearly matched parallel groups. I used two parallel groups(8 modules in total) with a drv134,to make two monoblocks. The dc offset in .0003 on one and .0001 on the other.
One thing I would add make sure all connection are proper and solid or you will get hiss.
I used trim pot on the non inverted inputs.
I built 20 indepentent modules. I picked 16 modules with the closest dc offset,then I broke that group into four group all with dc matched as close as possible. I ended up with four nearly matched parallel groups. I used two parallel groups(8 modules in total) with a drv134,to make two monoblocks. The dc offset in .0003 on one and .0001 on the other.
One thing I would add make sure all connection are proper and solid or you will get hiss.
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