Hi,
Newbee in power amp design and construction.
I recently got interested in constructing myself a power amplifier.
My plan is to build an 8-way power amplifier based on the LM3886 chip, to actively drive a pair of speakers, not as a professional, merely as a hobby, for fun, for the beauty of building it myself.
I have absolutely no idea about the different power amp designs and their merits. There are many different PCB kits sold on the internet, including on ebay. Some are very cheap, some are way more expensive.
How to choose wisely for this plethora of kits, and simultaneously only spend the necessary money?
I do have plans of an obviously well designed power amp, but do not have the necessary skill to create a PCB myself, nor the necessary knowledge to pin point the exact replicate of it on a catalogue.
I have some basic skills in soldering and am not afraid to tackle a power amp project, but am reluctant to pay overpriced products, especially if it may result in some waste (due to my bad skills).
This may seem as a bottle in the sea, I just do not know where to search.
Regards,
Newbee in power amp design and construction.
I recently got interested in constructing myself a power amplifier.
My plan is to build an 8-way power amplifier based on the LM3886 chip, to actively drive a pair of speakers, not as a professional, merely as a hobby, for fun, for the beauty of building it myself.
I have absolutely no idea about the different power amp designs and their merits. There are many different PCB kits sold on the internet, including on ebay. Some are very cheap, some are way more expensive.
How to choose wisely for this plethora of kits, and simultaneously only spend the necessary money?
I do have plans of an obviously well designed power amp, but do not have the necessary skill to create a PCB myself, nor the necessary knowledge to pin point the exact replicate of it on a catalogue.
I have some basic skills in soldering and am not afraid to tackle a power amp project, but am reluctant to pay overpriced products, especially if it may result in some waste (due to my bad skills).
This may seem as a bottle in the sea, I just do not know where to search.
Regards,
Hi bidibidi,
I do not know if it is the best or cheapest but it is certainly one of the smallest pcb's for a 3886 chip amp and if you want to build an 8 channel amp then it will be worth a look.
Go to "search" and look for a member called "Digi01"; he has detailed information about the pcb and psu for his 3886 design.
I do not know if it is the best or cheapest but it is certainly one of the smallest pcb's for a 3886 chip amp and if you want to build an 8 channel amp then it will be worth a look.
Go to "search" and look for a member called "Digi01"; he has detailed information about the pcb and psu for his 3886 design.
Many thanks for your reply.
A question of a newbie:
IGC stands for Inverted GainClone.
Why is the inverting necessary, and what would it be if there were no inverting?
Regards,
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I have used several of these LM3886 chip amp "modules". They are available on Ebay from several sellers. I would avoid the versions that have other things on the PCB, like power supply or protection circuits. This one keeps it pretty simple, so there is not much to mess up!
Dual Mano LM3886 Mini Amplifier Finished PCB 68W X 2 - eBay (item 300525755209 end time Mar-14-11 18:52:51 PDT)
In case someone is reading this in the future, when the auction has been removed, just look for one like this:
-Charlie
Dual Mano LM3886 Mini Amplifier Finished PCB 68W X 2 - eBay (item 300525755209 end time Mar-14-11 18:52:51 PDT)
In case someone is reading this in the future, when the auction has been removed, just look for one like this:
-Charlie
Ok, thank you. Would you have any opinion on how it compares to other power amps?
The title says dual mano (mono?), but there is only one power amp chip on the picture, I guess two boards are supplied. Not sure about the tolerance of components used, it is not mentioned.
By the way, this particular PCB seems very popular as many sellers on ebay propose it, sometimes under a specific brand name.
Again, question of a newbie: using the same power amp chip, what makes one power amp design better than the other?
One may reply that I should do my homework, but have no idea where to start.
Regards,
There's no need to be so doom and gloom. The guy is just getting going.
These are fine, yes you get TWO of them. I have bought lots of them from various sellers. All were fine. Sure, sure you can't verify the components, etc. They come assembled, so the newbie can cut to the chase and get something working. Then he can take it to the next level.
How many posts on these forums are something like "I can't get my chip amp project working... waaaaah!". Get the assembled one and don't worry.
Here's another tip - there are sellers who sell two of these chip amp boards plus a separate power supply board. These are also good if you are starting out. For instance: LM3886 High End Power Amp Refer Gaincard New - eBay (item 120474005627 end time Feb-18-11 10:20:35 PST) Notice it says "fully assembled and tested"...
-Charlie
Ok, all comments are well understood.
Again, I will have to apologize for my ignorance: for an 8-channel amp, how many power supply regulators do I need? Is there any obstacle to feed all channels with one power supply regulator?
Please correct me if I am wrong: I guess that the number of power supply regulator depends on the number of power transformers.
So, the same question for the power transformer: ideally, how many is best? One power transformer for 2 channels? Or for 3 channels? Or for 4 channels?
I am here not only considering budget, but also the stability, noise, balance, and any other parameter which may affect sound in an active 2-speaker configuration (4 channels per speaker).
I realize it is many questions, I am again kindly soliciting your comments.
Regards,
Again, I will have to apologize for my ignorance: for an 8-channel amp, how many power supply regulators do I need? Is there any obstacle to feed all channels with one power supply regulator?
Please correct me if I am wrong: I guess that the number of power supply regulator depends on the number of power transformers.
So, the same question for the power transformer: ideally, how many is best? One power transformer for 2 channels? Or for 3 channels? Or for 4 channels?
I am here not only considering budget, but also the stability, noise, balance, and any other parameter which may affect sound in an active 2-speaker configuration (4 channels per speaker).
I realize it is many questions, I am again kindly soliciting your comments.
Regards,
It is possible to have:
a single power supply for all 8 channels
two or more power supplies, each supplying some subset of the channels
For each power supply, you need as a minimum:
1. a transformer of appropriate secondary AC voltage and current/power rating
2. a bridge rectifier or set of diodes to convert the transformer's secondary AC waveform to "pulsed DC"
3. Smoothing caps (large electrolytic capacitors) to smooth out the ripple in the "pulsed DC"
How many of these power supplies is a choice, and it depends on what you have available and how complicated you want to get with the design. You may find that you cannot purchase a single transformer in your area that is sufficient for all 8 channels, so you may need to think about how to proceed from there.
There are several things to think about when designing your power supply/supplies. There is a good overview for beginners here:
Elliott Sound Products - Linear Power Supply Design
Some additional higher complexity design tips can be found here:
Solid State Power Amplifier Supply Part 1
You will need to correctly size the voltage rating, capacitance, and ripple current rating of your capacitors. The transformer must have the correct secondary voltage and current capability. The rectifier must be able to handle the current demand of the amp at peak load with some headroom.
If you go for the power supply board from Ebay that I linked to, you should not expect the highest possible quality components, but they will likely be fine for two or even four of the LM3886 chip amps.
-Charlie
Brian Bell (ChipAmp.com) was one of the first to make/sell LM3886 kits. He has been around forever, thousands in the field, loads of support, and a solid design.
DIY Chip Amplifier Kits, PCB's, Components and Information.
DIY Chip Amplifier Kits, PCB's, Components and Information.
There's a wonderful attitude to lifelong learning.
A new hobby and the expectation of investing some time in that new hobby.
Welcome on board and enjoy the results of your endeavors.
Hi
Andrew T is correct on this one as I found out to my cost.
The boards are good and work - the components however are questionable.
Andrew
Ok, well understood.
Getting directly the fully populated board removes half the fun anyway.
I intended to purchase electronic parts from reputed suppliers such Digikey, Mouser or Conrad (in Switzerland). Soldering is fun too.
Now that you mentioned it, I was wondering if the part specifications are provided with the naked board, or should I guess on my own?
Also, even if the specs are given, what would be the knowledge required to confirm that these are good enough, or to replace them with objective/measurable better performance?
... again, I am asking newbie questions. Please apologize in advance.
Regards,
So you get 2 amps for 30 US$. That is ~22 €. A LM3886 costs ~5 € here, so for 12 € you get two assembled boards, with all parts. The work is more or less for free then. Sooner or later those Chinese will go broke.
Interesting, he claims 20 days for shipping to Germany and further down it says he does not ship to Germany. Why would that be?
Funny, he does not ship to China either although he is located there.
Interesting, he claims 20 days for shipping to Germany and further down it says he does not ship to Germany. Why would that be?
Funny, he does not ship to China either although he is located there.
In real estate they have a saying that the three most important aspects of a property are 'location, location and location'. For chip amps, these three most important things are 'layout, layout and layout'. Most of the single chip designs copy National's datasheet so the schematics are the same. The expertise of the designer can be seen in how he/she handles grounding, decoupling, placement of critical components and routing of tracks. Secondary is the choice of components - caps and resistors. If those turn out to be the lowest possible quality, its a great tweak to upgrade them. Changing sub-optimal layout though isn't for the faint-hearted.
Regulators aren't needed in the supply for chip amps - just rectifiers and smoothing caps. Plus snubbers across the rectifiers for lower EMI.
Go for the biggest transformer size you can comfortably fit into your case. Make sure it has at least two separate secondary windings and not a single centre-tapped one. Big transformers perform better in terms of regulation - the voltage sags less under load. Custom toroidals aren't particularly expensive to have made, you can specify multiple pairs of secondaries if you want to implement isolated supplies. There's also another advantage to having just the one trafo - less noise coming across from the mains owing to reduced overall capacitance between the primary and secondary sides.
The choice between inverting and non-inverting largely depends on what's upstream from the chip amp. Inverting chip amps have lower input impedance so might come with an on-board opamp buffer. Bob Cordell's chosen this route for his design - running the chip amp inverting gives lower distortion. If you're of the school that fewer parts will sound better, choose non-inverting because then there's no need for that extra buffer. Ultimately though, choose based on excellence of overall design (i.e. layout) rather than detailed circuit configuration.
pacificblue said:
The economics in China are rather different from those in Germany. For a start the LM3886 retails here on Taobao for 2-3€. Those builders will be paying less in quantity. Their overheads are way lower too. So, no - no danger of them going broke just yet.
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Yes, I have been to China and have seen the prices to be usually a third of ours. I have seen products that cost less than the world market price of their raw materials. So, how can that be in a rather globalised economy without someone losing money?
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