mp3 playback module

eggie

Member
Thanks neil - that helps me a lot. I will try assembling a circuit tomorrow to get it working.

Taken your advice and re-read the whole of the thread - embarrased now - should have done that first as I had forgotten some of the postings and not realised what I was missing. That will teach me to try to go from memory!
 
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Grogster

Senior Member
Sorry for the late post guys - I understand a couple of you have been PM'ing me about this module, but I have been very busy installing, and did not check in for a while...

If you have not soldered those tiny little SMD resistors before, I don't suggest you start with the modules you have! :D

You can buy SMD practice kits from most electronic hobby shops - just a useless PCB and some SMD devices so you can practice your soldering.

I agree with the other comments though - use serial, it is well within the range of most PICAXE chips(even an 08M running at 8MHz), and the commands are very simple.

You can connect the module pins directly to the PICAXE - they are 5v tolerant.
There is no need for any RS232/TTL level corrector between the device and the PICAXE.
All input pins on the MP3 module have internal pull-ups to the device's supply rail, which is 3.3v or so.
 

eggie

Member
Help................................

I seem to have destroyed the sound output of both units I bought. The first I connected to LM386 amplifiers but I forgot the decoupling capacitors and so I think something went wrong there, but not sure what. The second I connected up to headphones to avoid the same situation. It worked for a while but now has stopped - but I have no idea why. I think I can control the unit as the Busy LED responds to the commands from the Picaxe but I cannot get any sound on the headphones.

Are the headphones causing the problem?

As I plugged the headphones into the socket there is the risk that I grounded one or both of the outputs - would that cause the damage?

Has anyone had any similar problems???

Any suggestions would be greatly appreciated.

Thanks.

Eggie
 

hippy

Technical Support
Staff member
It does unfortunately seem like you have blown the outputs.

I'm not sure how missing decoupling capacitors on the LM386's could have caused that and it may have been some other reason. If you connected headphones between the module output pins and 0V that could well have blown it.

Looking at the PCB tracking, the two outputs, pins 17 and 18, seem to go through C17 and C18 and then direct to the main chip.



The datasheet describes the pins in that area of chip as 'headphone output' and that seems to match track to pin numbering, but I don't know how literally 'headphone' is meant to be taken.

I had thought that U4 were probably an op-amp for buffering PWM output, but it seems not. It actually now looks like an I2C Eeprom to me but I can't read any engraving on it. If it is Eeprom then I wonder what it holds ?

Without a full circuit of the module or reverse engineering it all it is hard to say.

Best bet is probably to put it down to experience and order another set of modules.
 

eggie

Member
Many thanks for your comments Hippy.

I have just ordered three more units but I am worried that as I do not know what has gone wrong, I do not know how to avoid destroying these new modules. I note that the outputs are already protected by capacitors - My thoughts now are that these may act as decoupling capacitors in any case. Are these likely to have protected the unit from stray voltages? You suggest that the problem I have with the output being destroyed is possibly down to something else but do you have any ideas as to what could have possibly caused this?? I am at a total loss.

Additionally, sorry if this sounds stupid, but can you offer any suggestions on how to connect this unit up to some headphones. I only dabble in computing and electronics in my spare time so my knowledge is a bit thin (they do say that a little knowledge is a bad thing but I am trying to change that!). Untimately I am intending to connect the unit up to two LM386 amplifiers and a pair of speakers but in the meantime headphones will be sufficient until I get the module fully working. Do I need the input resistance of the LM386 whether I use headphones or speakers in any case?

I am using a 9V battery to drive both the MP3 module and the LM386's, with 3No AA batteries for the Picaxe and a common earth.
 

hippy

Technical Support
Staff member
The most likely cause of damage would be over current through the pins or voltage error, conecting through a too low resistance to 0V ( headphones, or shorting to 0V while inserting headphones ), or connecting to an amplifier circuit which pulled the pin too high or negative. A simple miswiring, or a volume control error so it shorts to 0V as turns, could be the cause.

I don't have any particular recommendations, I simply took the outputs into a TV input, and that should work for any amplifier. Without knowing the chip can drive headphones direct I would assume not and always use an amplifier.
 

julianE

Senior Member
while waiting for my amplifier chips to arrive i have had a pair of sony headphones attached to the module audio output, been working for over a week without any issues, plenty loud too. i just have it attached using alligator clips.

btw, wonderful find on the module. there is a bit of noise between tracks and guitar is a bit 'brittle' sounding but i'm splitting hairs.
 

1968neil

Senior Member
there is a bit of noise between tracks and guitar is a bit 'brittle' sounding but i'm splitting hairs.
ive got one hooked up to the AUX input on a hifi and the sound quality is as good as any mp3 player ive seen.

I would assume that the outputs are "Line" level and not intended to be loaded directly with a low impedance load like a speaker, i would imagine the brittle sound you experience is due to the load ?

I also made up a small piece of veroboard with a header, this also contained a 3.5mm headphone socket. This plugs straight into a breadboard and then i use a 3.5mm stereo cable to two phono plugs straight into the aux socket on the hifi.
This save any slip ups when connecting it up.
 

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julianE

Senior Member
This module is a lot of fun but i was curious if there are ones that will play FLAC (Free Lossless Audio Codec) files. I've converted a lot of my music collection to FLAC and it would be nice if I could find a module that can play them. I realize I'm reaching for the moon but maybe someone on the forum would know.
 

julianE

Senior Member
I found a board that will play just about any format including FLAC, not sure how difficult it will be to interface to a picaxe.
It's based on a VS1053 chip and available from sparkfun.

http://www.sparkfun.com/products/8954

I plan on ordering it soon and I'm sure will need help from the forum experts.
 

hippy

Technical Support
Staff member
Correct me if I'm wrong but my understanding is that the VS1053 is only a stream decoder so something needs to pump raw MP3 etc data into it at the required rate. It seems highly unlikely that any PICAXE would have the oomph to achieve that by itself.
 

julianE

Senior Member
Hippy, as always, you are right, the VS1053 will not work with the picaxe as is. I was looking around on the VLSI site and they have many evaluation boards that might be able to do the heavy lifting, some come with SD cards on board, I'm guessing you can load your music files on the SD card and use the Picaxe to control the board.

http://www.vlsi.fi/en/support/evaluationboards.html

I bet the boards are super expensive, one had a price of 200.
 

Grogster

Senior Member
Well, the dinky wee 380 board would be hard to beat at $10 - even if you have to sacrifice to old MP3. :D

Personally, I can't hear any noticeable difference in an MP3 ripped at 320kbps and the original CD. Perhaps it's just me, but...

It is certainly true that lots of high-frequencies are lost at the lower bit-rates.

According to what I read once about MP3 encoding, the encoder gives priority to the vocals first, the low frequencies 2nd, and the high-frequencies 3rd. So this means that with lower bitrates, MP3 will chop the high's.

However, with 320 bitrate, they all seem to be there, and with today's hard-drive capacities, there really is no reason NOT to rip at 320.
 

julianE

Senior Member
The little board is extremely good for $10. What I hope to make is a substitute for my Logitech Squeezbox which i'm very happy with except for having to have a music server running on a PC. It would be nice to have a little picaxe based box with a memory card full of music and no need for a PC.
I can't tell a difference between a cheap wine or an expensive bottle, to me the cheap one almost always tastes better but i can tell a difference between different audio sources. digital has made everything convenient but seldom better, i still prefer analog audio and film but I do listen to digital audio and shoot a lot of digital pictures all due to the convenience factor.

i am almost finished with building a little system around the board Haku found, maybe i'll listen to it tonight while developing a roll of film

cheers.
 

julianE

Senior Member
I poked around the sparkfun site and found a module that uses VLSI VS1053 and looks to me like it can be controlled with a picaxe, probably with the more avanced ones since it needs,

•Serial: Full duplex, 8N1, 38.4K baud

I think the 18M2 should be ablet to work at that speed

here is the link to the module,

http://www.sparkfun.com/products/9715

not a bad price but strangely enough the little board that Haku found has some features, like the abilty to play even more files, that best the fancy sparkfun module.
 

hippy

Technical Support
Staff member
I expect most modules are comparable with the MD-Fly module but I did note "Firmware update 2.23: compatible with 192kbps audio" while the MD-Fly can handle 320kbps.

I'm not sure how any $10 or so module compares soundwise with a dedicated streamer which costs maybe 20 times more and at least some of that cost is likely to be in better audio circuitry, larger DAC and anti-aliasing. Ideally one wants to skip analogue completely and feed digital straight into the amp.

I expect most modules will be good, the MD-Fly absolutely brilliant given its cost, with a lot more having to be paid if you want audiophile quality or higher capabilities.

I haven't done anything recently with my modules and that's the over-Christmas project.
 
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julianE

Senior Member
I am starting to think that the TDB380 uses the VLSI chip, I was looking about the Tenda website and if you look at the download section under MP3 decoders they specify VS1003 and VS1053 the chips that i was looking at on the sparkfun site.

http://www.tendaelectronics.com/?action=text|tenda|128|en|429|429

I also looked at the VS1053 and the surrounding circuitry and it looks similar to the big chip on the TDB380 board. This little module is looking better every minute, I knew it sounded nice but it's really looking like a screaming bargain now. I think i'll order a few more.

Other then the fact that it's only format is MP3 I think this might be close to an audiophile product, maybe a little better voltage regulator and better power supply filtering might help but those are minor tweaks.
 

Grogster

Senior Member
Coupled to a decent HiFi op-amp like the LM833, the 380 module performs EXTREMELY well through most stereos. As-is, the audio output level of about 200mV is not enough to drive a modern amp's AUX sockets, and although you can get the volume by winding up the amplifier's wick a bit more, it does make background noise and DAC processor noise more audible.

Attached is my experimenter's board - allows buttons or serial control, and has on-board stereo pre-amp - literally. :D
 

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julianE

Senior Member
that is one fancy experimenter board. i don't have the resources to make anything so fine. i'm using a kiwi board for the picaxe and a small radio shack board for the module.
i looked around for the LM833 kit that you are using but i can't find it being sold by any US seller. i do have the chip and will take your advice and make a little 10db gain preamp. looking at your board it does not look like you are using a dual power supply for the op amp, or are there provisons being made on the preamp board?
 

hippy

Technical Support
Staff member
I am starting to think that the TDB380 uses the VLSI chip
From one of the sleuthing efforts and posted links/image earlier there was a photo of the module with the chip on it which hadn't had the engraving scrubbed off. That showed it to be an AU6850B, made by Shanghai Mountain View Silicon Technology Co Ltd.

http://www.mvsilicon.com
 

Grogster

Senior Member
Further to my above post, you don't specifically need that pre-amp that I am using.
ANY low-noise HiFi preamp where you can set the gain to about 10dB would suffice.

It is probably a good idea, to get a HiFi stereo pre-amp kit from your local supplier rather then trying to track down the Jaycar one overseas - this is just the one that I used.

The LM833 is used in many pre-amp designs, but generally, those designs call for a split-rail power supply. I like the Jaycar one, as it only needs a single supply.
 

julianE

Senior Member
Outstanding sleuthing on the main chip. Plenty of info about the chip,

AU6850B/C520B/C522
AU6850
USB Host/SD MP3 Decoder (Cost-effective Version)
» 1.8V/3.3V Power supply, LQFP64 Package
» Embedded 8051-compatiable MCU and 32KB embedded OTP
» USB2.0 full-speed host controller
» SD/MMC card reader controller
» MPEG 1/2/2.5 layer-III decoder, 32~320kbps, VBR
» Embedded audio DAC and EQ control
» Embedded IR decoder

I wish the rest of the functions were available on the module, EQ control might be nice and the IR decoder would be welcome. i have my little project using the IR abilities of the picaxe so that's not a big deal.
 

julianE

Senior Member
The LM833 is used in many pre-amp designs, but generally, those designs call for a split-rail power supply. I like the Jaycar one, as it only needs a single supply.
I too have heard good things about the LM833 and have about 10 of them in my stock. I also have some Burr Brown Op Amps but not sure where I put them.
How does the Jaycar simulate a dual power supply, I'm assuming they just have 2 large value capacitors in series and they tap the center for ground.

On another topic, I did notice on the datasheet that the AU6850B chip is rated for 3.3 Volts but everything I read on this post talks about the regulator on the module being a 5V unit. I have not measured it yet but if by bypassing the regulator the module can run on 2 battery cells that would make things easier for making a portable player. I have some amplifier modules that i ordered from Sure electronics that run on 4 volts or lower.
 

Grogster

Senior Member
Blowing the room apart tonight using this module and 833 setup...
The Jaycar kit biases the op-amp to half-supply via two 10k resistors to deck, with a 100uF decoupler cap.
Using the pre-amp, I can detect NO decoder noise during quiet bits.

The on-board LM317 regulator on the module is set for 3v3, so the chip and core run at 3v3.

The inputs are 5v tolerant though, which is nice, as you can then connect them directly to the PICAXE. :)
 

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fritz42_male

Senior Member
Hey Grogster, FYI that board is available in from Jaycar regardless of country.

How much would you charge me for that board you mounted all the stuff on and where did you get the switches?
 

Grogster

Senior Member
Good news on the PCB shipping - I was not sure if Jaycar shipped outside of AUS/NZ as mentioned...

I got the switches from Jaycar, also the headers and RCA PCB sockets.

Blank board was NZ$10 plus etching/drilling/lacquer.

I could sell you a board for NZ$15.
This is etched, lacquered and cut to size, but you would have to drill it.
You would have to buy and build the pre-amp kit, and supply the switches and RCA sockets.

I can also supply the board drilled for an extra $5 to cover time, so NZ$20 etched, lacquered, drilled.

I would have to check shipping rates, but to Australia would not be much - the board is light.

This offer is open to all here if anyone is interested.
 

julianE

Senior Member
There are two Velleman pre-amp kits available in the US that might work as well:

http://www.vellemanusa.com/us/enu/product/view/?id=350491

http://www.vellemanusa.com/us/enu/product/view/?id=350492

I think the second one might be similar to the Jaycar kit but I can't find info on which chip it's using. Zooming in on the picture shows a TI logo but I can't make out the rest.
First one uses a TL072 a ubiquitous old school chip. I think a ton of mixing consoles use that chip. an old design but a good one. the good thing is, op-amps are easy to swap so one can pick and choose.

The second kit, i think uses the same chip, i actually have that kit. The kit is not suitable for the MP3 module, it's an RIAA amp, meant for turntable cartridges.
 

Jeff Haas

Senior Member
Julian, you mean that you could drop in a different opamp into the socket and the circuit should work OK? Such as the 833 in the Jaycar kit, if you liked the specs better? Interesting.
 

julianE

Senior Member
Julian, you mean that you could drop in a different opamp into the socket and the circuit should work OK? Such as the 833 in the Jaycar kit, if you liked the specs better? Interesting.
Yes, if you look at the pin out of the LM833 and the TL072 they are identical. most Op-Amps have a standard pin out. You can upgrade circuits as better devices are made. As in everything in life just because something is new and looks better on paper does not mean it is so in real life. yes MP3 is so much more convenient then vinyl records but to my ears it's not better. i do enjoy listening to mp3's but there is that something extra that vinyl brings. the best explanation i have heard is this. a cartridge on a turntable acts like an instrument itself. if you think about it, it's a mechanical system that is in effect being strummed by the grooves in the record, so what you are hearing is a musical performance by a musical instrument. the musicians of old, had the option of hearing their performance on original master tapes but they all say that a magical transformation happens once the master tape is transfered to vinyl. there was a lot of art in mastering a record.

sorry to go so far off topic. :)
 
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