… or: is it possible to attain more than 200W from an amplifier based on LM3886 IC
Here is another project from my workbench. I was very pleasantly surprised with several amplifier projects based on chip amps, LM3886 and TDA7293. However, the main obstacle using these ICs is moderate, or should I say, lowish power output, about 60W per channel.
People persistently complain about the “poor bass” but I don’t think that the IC is the culprit. Inadequate speakers in combination with poorly designed amplifier boards are likely responsible for the LM3886 bad reputation in low frequencies. My measurements indicate otherwise: the IC is OK itself but it deserves better “working conditions”.
Obvious solution is paralleling and bridging, but, it isn’t so straightforward. Due to the lack of knowledge I have decided to use an existing design and turn it into a decent and powerfull amplifier. My choice is YISHENG LM3886 BTL Amplifier Board which implements paralleling and bridging to attain High Power High Fidelity performance.
One channel of this board is presented at the snapshot below. A lovely design, if I may say. I haven’t tried yet to reverse-engineer it. My intentions are much more modest. I want ro investigate the real world performance if this board and how to use it as a Hi-Fi amplifier.
First, I have investigated frequency response of the board and I have found out that test results are great indeed. Also, I have tested square wave response which are quite adequate.
Now, I'm testing its endurance on 200W 7.3 ohm dummy load. For time being I was able to run it at 125W constant 1KHz signal. I do really push it at the limits of thermal endurance.
Otherwise, the board is a real beauty, very well designed with wonderful layout. It is going to have from me a beautiful chassis.
More to follow...
Meanwhile, I have uploaded more photos of the amplifier board from my bench.
Please note that the board utilized four OPA2605 opamps and two pairs of transistord: 2sc2383, 2SD669, 2SC649 and 2SA1013. It appears that it is a bit more than paralleling and bridging. Let's see what it is
Here is another project from my workbench. I was very pleasantly surprised with several amplifier projects based on chip amps, LM3886 and TDA7293. However, the main obstacle using these ICs is moderate, or should I say, lowish power output, about 60W per channel.
People persistently complain about the “poor bass” but I don’t think that the IC is the culprit. Inadequate speakers in combination with poorly designed amplifier boards are likely responsible for the LM3886 bad reputation in low frequencies. My measurements indicate otherwise: the IC is OK itself but it deserves better “working conditions”.
Obvious solution is paralleling and bridging, but, it isn’t so straightforward. Due to the lack of knowledge I have decided to use an existing design and turn it into a decent and powerfull amplifier. My choice is YISHENG LM3886 BTL Amplifier Board which implements paralleling and bridging to attain High Power High Fidelity performance.
One channel of this board is presented at the snapshot below. A lovely design, if I may say. I haven’t tried yet to reverse-engineer it. My intentions are much more modest. I want ro investigate the real world performance if this board and how to use it as a Hi-Fi amplifier.
First, I have investigated frequency response of the board and I have found out that test results are great indeed. Also, I have tested square wave response which are quite adequate.
Now, I'm testing its endurance on 200W 7.3 ohm dummy load. For time being I was able to run it at 125W constant 1KHz signal. I do really push it at the limits of thermal endurance.
Otherwise, the board is a real beauty, very well designed with wonderful layout. It is going to have from me a beautiful chassis.
More to follow...
Meanwhile, I have uploaded more photos of the amplifier board from my bench.
Please note that the board utilized four OPA2605 opamps and two pairs of transistord: 2sc2383, 2SD669, 2SC649 and 2SA1013. It appears that it is a bit more than paralleling and bridging. Let's see what it is
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Maybe read this thread. This product has the same configuration and far as bridging three parallel devices. Just a bit more fancy as far as the composite driver design.
https://www.diyaudio.com/community/...site-power-amp-with-extremely-low-thd.318372/
https://www.diyaudio.com/community/...site-power-amp-with-extremely-low-thd.318372/
But ofcourse I will do that. The photo in the OP is taken from the sellers site. I plan to add more photos from my workbench. I have "finished board". I have also ordered bare boards and I will take a snapshot of the both sides too as soon as they arrive from China. They have already arrived to the customs office.
The bottom side is interesting: there are many SMD parts below, at the bottom side. Quite ellaborate. I will make a photo from the bottom side today. I took a short nap after the lunch. I will take photos as soon as I arrive to my workshop.
Thanks, but I have decided to maintain this conversation/thread clean, without unnecessary excursions towards "Done Right" threads. Thanks anyways but every single LM3886 theme becomes unnecesarily poluted with Done Right distraction.
Lets keep this separate! Thanks!
Meanwhile, I have uploaded new photos of the amplifier at my workshop.
I am going to do even more measurements including investigation of the effect of different loads and temperatures of ICs at different operating conditions.
Today, I have measured the impact of different power outputs on power supply voltage. Power supply sags at higher outputs. I also have observed how quicklly the ICs attain steady state temperatures. Interesting indeed. It appears that heat transfer could be the limiting factor on attaining higher outputs. There must be some trade-off here.
There is one difficulty with measurements of BTL amplifiers with oscilloscope. It is necessary to measure right and left chanel with refference to ground and then apply math function to add voltages of the both channels. Also, THD measurements can be tricky.
Please note at the newly uploaded photos in the OP that the board utilizes four OPA2604 opamps and two pairs of transistors: 2sc2383, 2SD669, 2SC649 and 2SA1013. It appears that it is a bit more than paralleling and bridging. Let's see what it is when I get bare boards without components soldered.
More to follow...
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At zero input current is 345mA. Onset of clipping is at 30 Vrms. This is a bit premature because power supply sags several volts and I use 24-0-24V transformer.
Here are the measurement results, numeric values are shown in the table below.:
| Input | Output | I |
| Vp-p | Vrms | mA |
| 0 | 0 | 345 |
| 200 | 5,78 | 940 |
| 300 | 8,7 | 1305 |
| 400 | 11,64 | 1669 |
| 500 | 14,58 | 2034 |
Of course, it is with 7.3 Ohm 200W dummy load.
Just one important detail more: In this particular case I have used a capacitance multiplier power supply with output of just slightly above +/-30 V and it sags at higher power demands.
I have now replaced capacitance multiplier with a linear power supply providing +/'34.5 volts. I have estimated that it will produce about 160-170 Watts into 7.3 Ohms. It is concievable that the amplifier can produce 200W into 4 Ohms. But why bother to run amplifier on its very limits. Perhaps it will be wise to run it at moderate values to have design margin when loud music demands more power and run it comfortably cool.
EDIT: and, by the way, the meassured quiescent current matches values from the technical data sheet 6X(50 ... 85 mV).
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Here we are, without load:
Before clipping: 44,.0 Vrms, Iq=591 mA
Clipping 44.8 Vrms, Iq= 512 mA
Is there any issue you would like to address regarding this matter and measurement results? I have read other posts by you elsewhere in this forum and I am sure you may offer authoritative opinions and suggestions.
Tomorrow I intend to proceed with other set of measurements regarding frequency response of this amplifier.
The LM3886 to my criteria, is not a HIFI amplifier. This amp seems to be compound. To check its audio qualities if it is better than a PA amp try these music pieces.
Go straight to Requiem of Verdi. If don't have yet your national treasure, you find on YouTube by BBC orchestra from 9:35.
If it sound clear, evoking passionate emotions try the requiem of Mozart 8:24
listen if it inspires you spiritual emotions, as it should sound celestial.
If the Verdi's is dirty, try the "Happy together " of the turtles. If the refrain sounds dirty as LM3886 stand alone does, this is not an audio amplifier.
The LM3886, every time I compound it, the sound goes back stage and the music becomes uninteresting. Most large Jazz orchestras is suitable for this test but the one I use is the Ironside theme of Quincy Jones.
Go straight to Requiem of Verdi. If don't have yet your national treasure, you find on YouTube by BBC orchestra from 9:35.
If the Verdi's is dirty, try the "Happy together " of the turtles. If the refrain sounds dirty as LM3886 stand alone does, this is not an audio amplifier.
The LM3886, every time I compound it, the sound goes back stage and the music becomes uninteresting. Most large Jazz orchestras is suitable for this test but the one I use is the Ironside theme of Quincy Jones.
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Isn't it a bit too early to approach such bold conclusions? Based on listening youtube clips?
Before even starting some subjective tests, I prefer first performing some quantitative, scientific tests.
So, let's first measure and then decide.
I wish you pleasant hollidays
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Well, meanwhile, I went ahead with measurements. I have connected output "+" and output "-" to two channels with reference to ground and have observed both values by applying "substraction". The result was a straight line at zero indicating that the values at "+" and "-" outputs are practically identical, for all intents and purposes, with infinitesimally small offset. Obviously, servo circuits did good job.
Next, I will investigate alternatives for speaker protection. I guess this design will require separate protection for "+" and "-" with reference to the common ground.
Next, I will investigate alternatives for speaker protection. I guess this design will require separate protection for "+" and "-" with reference to the common ground.
Meanwhile I have read old themes regarding paralleling/bridging LM3886. I was impressed and overwhelmed with quality of that discussions, so much so, that I have decided to conclude this theme and direct these interested into the direction of the existing knowledge presented in other places. Previous art. My respect.
Here are the relevant threads:
Rowland LM3886
About the Jeff Rowland LM3886 amplifiers
You may also search BPA200 or BPA300
Thats all I had to say about the present subject.
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Here are the relevant threads:
Rowland LM3886
About the Jeff Rowland LM3886 amplifiers
You may also search BPA200 or BPA300
Thats all I had to say about the present subject.
-----------------------------------------------------
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