My first try for LM3886TF

[pra3718]

Should I keep Power supply pattern is similar to TDA2050
1 Nos 24-0-24 3Amp
4 Nos 6Amp Diod
4 Nos 4700 mfd 25V ( 2Nos for (+), 2Nos for (-) )
What is the difference between single bridge rectifier with basic center taped transformer & dual bridge rectifier with two transformer (snubber). Dual bridge boost some power to lm3386 ?

Can I use 12" 4 Ohms Driver, with this amp for subwoofer (provided 35V (+-) approx.)
Or Should I stick with my old 4 Ohms 8" 40 Watts Max X 2 Nos but this time I would use it IN-SERIES.

All capacitors should be 25V or 50V

I have seen some schematic where zobel or output inductor (ESP) is not advised.

I have seen some schematic where feedbak cap 22uf is optional.

I am going to use LM3886TF for Subwoofer, any special advise

Which schematic would be best for me.

I wish not to use any preamp or buffer then what should be my standard gain ? (my source signal is weak) I think I have LM3886TF i.e. enough power to drive subwoofer. Looking for clean bass.

I saw first time LM3886TF in my life. I did not find any metal part in back-side which touch the heat-sink & transfer heat to the heat-sink.

[AndrewT]

24+24Vac is probably not suitable for driving 4ohm speaker from a chipamp.
Check the datasheet for design details.
a centre tapped transformer (24-0-24) cannot be used with a dual rectifier arrangement with the remote power zero volts.
You need a dual secondary (0-24, 0-24) for a dual rectifier.
The single rectifier can be used with either the centre tapped or the dual secondary.

The TF version has built in insulation that increases the thermal resistance of the chip to sink interface. This increases the temperature of the chip and may make it unsuitable for high power duty use. Depending on your speaker sensitivity and how you like to play your system the TF may overheat and force the protection systems to intermittently cut the signal or clip (current limit) the output. A 4ohm speaker load and the 24Vac transformer will each add to this problem.

4 Ohms Driver,.......... (provided 35V (+-) approx.)

look at the datasheet for a 70Vdc supply and 4r0 loading. A 4ohm speaker is much worse. National conveniently don't give details for reactive load limits, they show resistive load limits instead.

[pjp]

pra, transformers are usually specified in AC RMS volts. You can't use a 25V capacitor with a 24V transformer.
24V AC RMS will give you 34V DC.

[pra3718]

@AndrewT : I understood for 24-0-24 & dual rectifier not possible that require 0-24, 0-24 but I want to know advantage/disadvantage for both versions. Now understood advantage/disadvantage for TF versions. 4ohm speakers is not advisable for 3886, I will try 8ohm.

@pjp : As I understood for 3886 project 50V capacitor I should use.

Yet, I don't have sufficient information to build this 3886 project.

Waiting for ... Regards & Thanks.

[AndrewT]

Originally Posted by pra3718

Yet, I don't have sufficient information to build this 3886 project.

download the datasheet and the application notes.

[sangram]

Look at the parallel amplifier application diagram in the LM3886 datasheet. It will operate 4 ohm speakers properly with 35 volt rails. I use one such amp to drive my Dynaudio BM6 monitors, and it delivers all the volume I need without activating protection, or overheating. You will need 2 chips for each active channel, and have to match the resistors by hand. A 27V supply for a single chip driving a 4 ohm load will be suitable if you have only one chip per channel.

There's a post here which outlines in great detail the differences between single and dual rectifiers, but it's buried inside another thread. Basically it's about ground currents and their return path to the transformer, I don't remember the 'verdict.

Anyhow, having built with both CT and dual secondaries/rectifiers, I think there is very little difference and a single bridge and a CT transformer work just as well, provided you take adequate care in the construction, use reasonably capable hook-up wire, and manage the ground arrangements well

I don't use a zobel. I use short lengths of high-quality speaker cable. I would not advise it to be removed for your first build. Once you get comfortable building them you can decide to remove them and experiment.

Do not remove Ci. You will likely get higher offset, and the sonic gains are probably not worth it for subwoofer application.

It would not be wise to have gain more than 30dB. The standard is 26dB (x20), I've seen PDs kit using a x33 gain (22K/680) and that is probably the most I would use. Higher gain setups may result in too much noise.

The heat transfer surface is what you see, it's just a sheet of plastic. Apply thermal compound on the back (the side with no lettering) and torque it on to a heatsink. It'll survive.

[pra3718]

Thank you Sangram.

[pra3718]

@Sangram : With very big efforts I arranged LM3886 & Build. In first attempt I build it right-way. I observed there is no POP (power ON/OFF sound). And sound is good, better than tda2050. As you advised "A 27V supply for a single chip driving a 4 ohm load will be suitable if you have only one chip per channel." I used 18-0-18 2 Amp transformer supply & it should deliver 25 (+-) approx. This time I got quality bass/punch, But not more powerfull again I will have to increase GAIN = 66 to achive the loudness. Expert says LM3886+25(+-)+4Ohm load should deliver 68 Watts. Is it important input signal strength i.e. 0.775 Watts.

Do you remember : "If you like a lot of thump and punch, then> you need to look at a way to get a more powerful sub and> pump it up till your pants flap in the port exhaust."

"Pant flapping bass is only> possible with huge and powerful subs (think >600 watts> and >24" cone area), not with a 22 watt amp and a> 6" or 8" driver."

Still I should not expect LM3886 will do the job ! Is that right ? It is not advisable but If I try for 24-0-24 transformer (35 (+-)) with 4ohms load, LM3886 / speaker would damage ?

[pra3718]

I used attached schematic.

[AndrewT]

No input filters
No output filters/loading
DC coupled.

You like living dangerously!