I would suggest as a first build to use one chip per channel. and experiment later with bridge setups.
Speaker impedance for BR100 lm3886 should be no lower than 8 ohms. This should provide 100W RMS.
with +-28V rails (22 0 22 transformer)
a bridge setup will need 220VA per channel or 500VA single supply.
Lots of info and reading on this website including BPA300:
Shine7 Audio DIY Page
This thread was started as a discussion on which setup to use.
tk2050 sure board or 2 x lm3886.
Combining lm38xx chips in bridging or parralel modes and their gains to single chips are a whole different discussion. Some people say this sounds better than single chips.
All and all the facts point to biggest difference is more power. And what type of speakers you are using.
A 4 or 6 ohm speaker will have more volume in parralel mode.
A 6 or 8 ohm speaker will have more volume in bridge mode.
I use Polk Audio Monitors series two ithink, |I have the picture of them in 2 or 3 page they're 8ohm speakers
btw is this good for bridged amp?
or bit too much?
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Sendler, you've made no mention of an unregulated linear supply in your tests... have you not tried it? Most people feel unregulated sounds much less restricted than a regulated supply. Also, is the current capability of your regulated supply anywhere near 9.7A? That could make a big difference as well.
I use Polk Audio Monitors series two ithink, |I have the picture of them in 2 or 3 page they're 8ohm speakers
btw is this good for bridged amp?
Should work into your 8ohm loads.
but remember you wil basically double the cost of everything.
double the VA rating on toroidal
toroidal rails must be 22 0 22 instead of 25 0 25
40000uF per rail in place of 20000uF per rail (the powersupply in your picture looks like it has 20000uF)
You will need 4 x lm3886 ,and either use a balanced input or have one lm3886 in inverting and the other in non inverting format.
And all honesty 50 -100W is not that much louder at all and you will probably be very happy with 50W. I am.
I couldnt find the db rating of your speakers but the ones i use are 92db and i find that 50W is more than enough.
unregulated
I used the power supply unregulated for years before adding the regulators on in front of the big caps. This is not really a regulated supply as the regulator is not closely coupled to the amp. It is more of an active filter with the regulator sensing the 40,000uf of tank caps. It makes a slight improvement along the lines of changing diodes. You should try it. The transformers are rated 3 amps, the regulators are 3 amps each leg so there are no bottle necks and the linear supply is actually as big as the the SMPS. 168VA per channel after throwing away 4v at the regulators for a total of 336VA vs 350VA for the MeanWell. The linear supply actually has an unfair advantage in this test as it is dual mono back to the switch. Running two Sure 2X100 modules dual mono and bi amping with short speaker cables obviously sounds much better for many reasons than the single module that was compared here.
I used the power supply unregulated for years before adding the regulators on in front of the big caps. This is not really a regulated supply as the regulator is not closely coupled to the amp. It is more of an active filter with the regulator sensing the 40,000uf of tank caps. It makes a slight improvement along the lines of changing diodes. You should try it. The transformers are rated 3 amps, the regulators are 3 amps each leg so there are no bottle necks and the linear supply is actually as big as the the SMPS. 168VA per channel after throwing away 4v at the regulators for a total of 336VA vs 350VA for the MeanWell. The linear supply actually has an unfair advantage in this test as it is dual mono back to the switch. Running two Sure 2X100 modules dual mono and bi amping with short speaker cables obviously sounds much better for many reasons than the single module that was compared here.
Is there any difference in the above two approaches? i.e. is one approach better than the other?
The LM3886 bridge application note AN1192 suggests using an inverted and a non inverted configuration to bridge. But I do not see any PCBs around that approach. Most people are looking at BPA using DRV134. Is it because they are using 6 LM3886 instead of just 2?
I am building a 3+3 channel amp. Each channel will have 2 LM3886 in bridge configuration. So looking for the best approach to bridge.
DRV134 adds to complexity and real estate issues considering that there are 6 amps to be bridged. I am wondering if there is any sonic benefit of taking that approach.
using the inverted half channel results in a low impedance input to the bridged power amp.
This low impedance and the different topology between the two halves makes it difficult to know how to design the amp for best performance. The source must also be able to drive that low impedance.
It is far better to set up the bridged power amp as a pair of non-inverted amplifiers and drive them with a balanced impedance signal from the source.
If you don't have a balanced impedance source then you must fit an unbalanced to balanced adaptor. The drv134 and lots of other circuits are that necessary adpator.
The adaptor can be fitted at the source (better location) or at the receiver (second best).
How did you arrive at the decision to fit 12 chipamps in one chassis?
Are all the speakers in one chassis?
I'll bet not. The speakers are probably spread around the room. It would be better to locate each power amp beside it's speaker, not in a central location with long speaker cables going to all the speakers.
This low impedance and the different topology between the two halves makes it difficult to know how to design the amp for best performance. The source must also be able to drive that low impedance.
It is far better to set up the bridged power amp as a pair of non-inverted amplifiers and drive them with a balanced impedance signal from the source.
If you don't have a balanced impedance source then you must fit an unbalanced to balanced adaptor. The drv134 and lots of other circuits are that necessary adpator.
The adaptor can be fitted at the source (better location) or at the receiver (second best).
How did you arrive at the decision to fit 12 chipamps in one chassis?
Are all the speakers in one chassis?
I'll bet not. The speakers are probably spread around the room. It would be better to locate each power amp beside it's speaker, not in a central location with long speaker cables going to all the speakers.
Thanks Andrew,
I have not decided on the chassis yet. Actually It will be a 8 ch amp (each channel having 2 LM3886s).
2 channel using PA100 (parallel config) and 6 channels having BR100 - Bridge configuration.
This is for the Linkwitz Orion DIY speaker, which I am planning to build next. It is a quad-amped active speaker.
Of the two speaker units each one has
2 tweeter drivers in parallel resulting in 2.5-3ohms. - This will be driven by 2 LM3886's in parallel configuration (PA100)
1 midrange and 2 woofers of 8 ohm each - each of these 3 speakers will be driven by 2 LM3886's in bridge configuration (BR100).
Two tweeters should be driven by two independant amplifiers, Do not parallel the tweeters and thus need to complicate the chipamps by paralleling them as well.
Similarly for two woofers. Use independant amps for each woofer.
That comes to 5 chipamps. Is 68W of maximum power into each of the 5 drivers sufficient for balanced peak SPL capability from the Orion drivers?
One 5channel amp dedicated to each Orion is far more likely to sound better than 12 or 16chipamps in a common chassis.
Personally I would build stereo amplifiers.
One stereo amp to the tweeter pair. One stereo amp to the woofer pair.
One monoblock to the Mid driver.
Total amp requirement for the 10driver Orions: 4 stereo amps and 2 monoblocks.
Similarly for two woofers. Use independant amps for each woofer.
That comes to 5 chipamps. Is 68W of maximum power into each of the 5 drivers sufficient for balanced peak SPL capability from the Orion drivers?
One 5channel amp dedicated to each Orion is far more likely to sound better than 12 or 16chipamps in a common chassis.
Personally I would build stereo amplifiers.
One stereo amp to the tweeter pair. One stereo amp to the woofer pair.
One monoblock to the Mid driver.
Total amp requirement for the 10driver Orions: 4 stereo amps and 2 monoblocks.
Hi Andrews
Very valuable inputs. I don't want to hijack this thread and have started my own thread here. Please visit.
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