Simple LM3886 Amplifier

[lifewater]

@linuxguru if possible you can help out lifewater with your myref pcb's , given you supply a whole kit, and also advice on the power supply he will be pleased..




Regards
saheb11123

Thank you very much brother. I have interacted with Linuxguru and have received some quote and advice from him.
Saheb, I was planning to ask Linuxguru to make a group buy of a low cost (1000-1500) per channel amp kit with LM3886, I know that for the quoted price it would be a plain vanilla setup but wont it inspire newbies to take their first steps in the DIY direction. A ready made kit is available from diyaudiokart costing @650 /- per channel without the heat sink,BUT pre-assembled so the satisfaction quotient is OUT. What do you think ??

Have a great weekend,

Lifewater

 

[linuxguru]

Thank you very much brother. I have interacted with Linuxguru and have received some quote and advice from him.
Saheb, I was planning to ask Linuxguru to make a group buy of a low cost (1000-1500) per channel amp kit with LM3886, I know that for the quoted price it would be a plain vanilla setup but wont it inspire newbies to take their first steps in the DIY direction. A ready made kit is available from diyaudiokart costing @650 /- per channel without the heat sink,BUT pre-assembled so the satisfaction quotient is OUT. What do you think ??

The MiniRef 1875 will make it to your price point comfortably (with good professional grade parts, but not boutique parts) for two channels with all parts on the PCB.

The minor catches:

1) The few MiniRef 1875 boards that I have on hand were supplied by PreSapian from Seoul, and I did not have them fabricated locally. This is not a major problem, since I was the one who designed the layout and have the Gerbers in case I need additional boards to be fabricated locally.

2) I'm not sure that the MiniRef 1875 is a project that can be recommended for newbies. It is more complicated than basic gainclones, but the payoff from that is much better audible sonics when implemented with reasonable care and careful parts selection.

3) The audible sonics are best with premium parts in the entire signal path, film/foil caps, fast-soft rectifiers, premium electrolytics (including a few Black Gates), non-magnetic and non-inductive resistors, etc. However, once boutique parts are introduced, it's no longer a low-cost newbie project, but more suited for an serious DIYer/audiophile.

It's probably best for me just to offer bare boards, and let the individual builders self-source components to their liking/budget. It will work fine even with cheap components, but will sound much better with premium components.

Edit: The MiniRef 3886 board is similar, but is more finicky about stability - I'd recommend it only for experienced DIYers. Both have exactly the same mounting dimensions, so it's possible in principle to interchange the two if needed.

 

[saheb11123]

@linuxguru
Can you provide vanilla LM1875 boards, then I would also be interested, I didn't go with the myref gainclones because of the same problems you described.

Like lifewater said vanilla boards welcome.
Though it is much to ask from you but please bear with us.

 

[lifewater]

The MiniRef 1875 will make it to your price point comfortably (with good professional grade parts, but not boutique parts) for two channels with all parts on the PCB.

The minor catches:

1) The few MiniRef 1875 boards that I have on hand were supplied by PreSapian from Seoul, and I did not have them fabricated locally. This is not a major problem, since I was the one who designed the layout and have the Gerbers in case I need additional boards to be fabricated locally.

2) I'm not sure that the MiniRef 1875 is a project that can be recommended for newbies. It is more complicated than basic gainclones, but the payoff from that is much better audible sonics when implemented with reasonable care and careful parts selection.

3) The audible sonics are best with premium parts in the entire signal path, film/foil caps, fast-soft rectifiers, premium electrolytics (including a few Black Gates), non-magnetic and non-inductive resistors, etc. However, once boutique parts are introduced, it's no longer a low-cost newbie project, but more suited for an serious DIYer/audiophile.

It's probably best for me just to offer bare boards, and let the individual builders self-source components to their liking/budget. It will work fine even with cheap components, but will sound much better with premium components.

Edit: The MiniRef 3886 board is similar, but is more finicky about stability - I'd recommend it only for experienced DIYers. Both have exactly the same mounting dimensions, so it's possible in principle to interchange the two if needed.

Thanks for your reply linuxguru, personally I have no preferences to output power, but some of us might like to have a setup with high output power i.e. LM3886 but the main requirement is LOW COST AND LOW PARTS COUNT So now we have :-

1.) Plain vanilla LM1875 boards and
2.) Plain vanilla LM3886 boards,

This board is available from ebay .in PCB FOR LM3886 68W RMS Amplifier IC 10QTY | eBay but seems like crap. So linuxguru, like saheb said we might be asking too much from you... but please bear with us. Maybe we can start a groupbuy for items 1 & 2.

@linuxguru
Can you provide vanilla LM1875 boards, then I would also be interested, I didn't go with the myref gainclones because of the same problems you described.

Like lifewater said vanilla boards welcome.
Though it is much to ask from you but please bear with us.

Sure Saheb, have requested Linuxguru the same and can we start a groupbuy ?

Regards,

Lifewater

 

[saheb11123]

Actually I ordered two boards from the ebay guy. They are well, I don't know what to say.


Currently I have been using lm3886 vanilla board as my current setup, but asking linuxguru for some other options as well.

 

[linuxguru]

I did buy a couple of EBay 2x NE5532 + 2x LM3886 boards long ago, but they required major modifications to make the sound passable. Their main selling point was that they were inexpensive.

The MyRef & MiniRef are successful attempts to get much better audible sonics from chipamps - both these approaches are nested feedback topologies, which give much better audible sonics and lower distortion, at the cost of higher complexity and cost (say 2x over a bare gainclone, other things being equal).

The problem with doing a basic gainclone board is that there isn't much by way of cost savings on the board alone, since the dimensions are driven by the size of the largest components - input DC blocking caps, PSU filter caps, bridge rectifier, Zobel network, etc., so the board ends up being almost the same size or maybe even larger than something like the MiniRef, which shares some of the large components across 2 channels.

Hence, the economics of basic gainclones is loaded towards off-the-shelf boards and modules, either local or Chinese. The tradeoff is lower measured and audible performance. That Ebay (India) bare board linked to earlier is pretty good value at Rs.440 (shipped) for 10, or Rs.44 each. I don't think it's possible to do better on price - about the only things that can be improved upon are in component selection and minor mods.

 

[lifewater]

Actually I ordered two boards from the ebay guy. They are well, I don't know what to say.


Currently I have been using lm3886 vanilla board as my current setup, but asking linuxguru for some other options as well.

Hi Saheb, I dont mean to say the Mr. Raju, the person selling the boards is bad nor is his service, but quality of the boards leave much to be desired. BTW are you using the same boards ??

I did buy a couple of EBay 2x NE5532 + 2x LM3886 boards long ago, but they required major modifications to make the sound passable. Their main selling point was that they were inexpensive.

The MyRef & MiniRef are successful attempts to get much better audible sonics from chipamps - both these approaches are nested feedback topologies, which give much better audible sonics and lower distortion, at the cost of higher complexity and cost (say 2x over a bare gainclone, other things being equal).

The problem with doing a basic gainclone board is that there isn't much by way of cost savings on the board alone, since the dimensions are driven by the size of the largest components - input DC blocking caps, PSU filter caps, bridge rectifier, Zobel network, etc., so the board ends up being almost the same size or maybe even larger than something like the MiniRef, which shares some of the large components across 2 channels.

Hence, the economics of basic gainclones is loaded towards off-the-shelf boards and modules, either local or Chinese. The tradeoff is lower measured and audible performance. That Ebay (India) bare board linked to earlier is pretty good value at Rs.440 (shipped) for 10, or Rs.44 each. I don't think it's possible to do better on price - about the only things that can be improved upon are in component selection and minor mods.

Linuxguru, OK lets take the board available on ebay as the basis, what mods would you suggest to get the best out of them. Sorry if I am asking too much, I hope you understand that I am doing this to goad a few among us to take at least baby steps in DIY.

Regards,

Lifewater

 

[saheb11123]

Hi Saheb, I dont mean to say the Mr. Raju, the person selling the boards is bad nor is his service, but quality of the boards leave much to be desired. BTW are you using the same boards ??



Linuxguru, OK lets take the board available on ebay as the basis, what mods would you suggest to get the best out of them. Sorry if I am asking too much, I hope you understand that I am doing this to goad a few among us to take at least baby steps in DIY.

Regards,

Lifewater

I am not using the ebay boards, they are lying with me.
Im using a much simpler design my one of my friends which I have posted earlier in this thread (at the begining).


@linuxguru can a lm3386 be run of two 12V smps , if yes, then what will be output power of the same?

 

[linuxguru]

@linuxguru can a lm3386 be run of two 12V smps , if yes, then what will be output power of the same?

I haven't run them with rails as low as +/- 12V, but the datasheet says it should work down to +/- 10V.

At +/- 12V, it should be possible to get an output voltage amplitude of say 10 V peak into 8 ohms, which translates to output power of ~6.25W RMS. Not much, but audible. For those kind of rail voltages and power levels, the TDA2030/2040/2050 and LM1875 are much better choices.

 

[linuxguru]

Linuxguru, OK lets take the board available on ebay as the basis, what mods would you suggest to get the best out of them. Sorry if I am asking too much, I hope you understand that I am doing this to goad a few among us to take at least baby steps in DIY.

I've only used the Chinese EBay board with 2x NE5532 and 2x LM3886 years ago, and I won't recommend wasting time on it - I did that when I didn't know better.

I haven't used the EBay (India) board you linked to, but assuming that it has been verified to be error-free and functional, it shouldn't be too difficult to choose a reasonable upgraded parts list by trial and error. He 's selling sets of 10 boards, so that gives a lot of scope for comparative experimentation.

I'd suggest that you buy a set and start experimenting. For starters, use reasonable-quality electrolytics like Panasonic FC, film caps from any of Epcos, Wima, ERO, Evox/Rifa, Panasonic, etc., and 1% metal-film resistors for most locations. Pay particular attention to the input DC blocking cap - use a metallized polypropylene (MKP) of the largest value/voltage that will fit in the space available.

 

[sashijoseph]

The ebay India boards are an Elektor design(Jul-Aug 1998) and for a plain vanilla NIGC look to be quite decent.

Component selection,like Linuxguru suggests,should be the key to make it sing better.

I too had bought a pair but haven't gotten around building them...

 

[lifewater]

I've only used the Chinese EBay board with 2x NE5532 and 2x LM3886 years ago, and I won't recommend wasting time on it - I did that when I didn't know better.

I haven't used the EBay (India) board you linked to, but assuming that it has been verified to be error-free and functional, it shouldn't be too difficult to choose a reasonable upgraded parts list by trial and error. He 's selling sets of 10 boards, so that gives a lot of scope for comparative experimentation.

I'd suggest that you buy a set and start experimenting. For starters, use reasonable-quality electrolytics like Panasonic FC, film caps from any of Epcos, Wima, ERO, Evox/Rifa, Panasonic, etc., and 1% metal-film resistors for most locations. Pay particular attention to the input DC blocking cap - use a metallized polypropylene (MKP) of the largest value/voltage that will fit in the space available.

Thanks linuxguru, how large should the input DC blocking cap be ? I am using 2.2 uf.

Regards,

Lifewater

 

[saheb11123]

10uf can also be used, which will result in better bass depth.
Which brand of cap are you using?

 

[lifewater]

10uf can also be used, which will result in better bass depth.
Which brand of cap are you using?

Hi Saheb I am using Solen brand.

Regards

 

[linuxguru]

1 to 2.2uF is fine, and Solen is a good MKP capacitor for input coupling.

 

[lifewater]

1 to 2.2uF is fine, and Solen is a good MKP capacitor for input coupling.

Thanks Linuxguru, I personally felt 10uf was way too much BTW I have some 4.7 uf MKP also, but did not try these out.

 

[saheb11123]

Thanks Linuxguru, I personally felt 10uf was way too much BTW I have some 4.7 uf MKP also, but did not try these out.

Where did you source these mkp's of solen?
And what other 4.7uf did you have, i mean brand?
I need to purchase two three, can you direct me? Can you sell me some?

 

[saheb11123]

@linuxguru
What input dc blocking caps can I use which is good yet can be sourced from india?
Im always on a budget (student payroll) so want a cheap solution which is good.

 

[linuxguru]

Apart from imported MKP caps that are available from time to time, your best bet is probably fan/motor-start capacitors, which range from a few uF to 10s of uF. A typical useful value for crossovers is Epcos 5 uF, while smaller values like 1.8uF are also used in fractional HP motors and industrial automation. These weren't intended for audio, but are usually well made with copper connectors, etc., so they can be used in audio if you have the space.

 

[saheb11123]

You mean to say there are bulky?
And what about sourcing?