BTL is bridge tied load. A bridge-tied load configuration consists of one amplifier driving one side of a load and another amplifier (with an inverted signal from the first amplifier) driving the other side of the load. This results in 2x more voltage swing across the load than you would have in a single-ended configuration where one side of the load is tied to an amplifier and the other side to ground. Twice the voltage swing across the load equates to 4x the power to the load (P = V^2/R). So, a BTL load configuration offers 4x more power to the load than a single ended configuration from the same supply voltage. Be aware, that BTL amplifiers dissipate 4x the heat of a Single-Ended amplfier under the same supply voltage and load conditions. Refer to the TPA7x1 series parts in the applications section for more on BTL. Also note that the output DC blocking capacitors are NOT required in the BTL configuration. Since the load is tied across two amplifiers with the same DC bias and the signal across the load is the difference between the amplifier outputs, the DC bias is removed. According to e2e.ti.com/support/amplifiers/audio_amplifiers/w/design_notes/1554.what-is-btl-configuration
Those particular breadboard pcbs have the very useful feature of facilitating the placement of decoupling capacitors very close to the ICs. Good Buy. Best wishes.
I have a few of the audio amplifier boards, but without the jack, and with 2 x 50W instead. The quality is very good, and fits tons of projects perfectly. I'll look forward to what you come up with, then maybe I can use my spare board for a new project. Cheers for the videos, I'm learning a lot from you that I can use at the electronics technician education I've applied for.
Julian, the aux input on that board is not an input, it's a line/headphone output! All the eBay descriptions selling that module get it wrong. I know, I've tried several.😣
I love a good postbag and yours always hit the mark. If I had the time I'd start doing them with all the stuff I get. Thanks to you putting me onto BangGood, I picked up a genuine Skyrc B6 Imax charger for $30 US.
I built this bluetooth amp project into a ceiling suspended shelf with two old pioneer car stereo speakers and three GU10 12v LED spotlights! It will eventually be suspended over my work station to add a bit of extra light and entertainment to my tinkering time. Like you I planned to run it off supercaps but had my order cancelled, at the moment I am running it off a 1200ma 12v dc power supply I had lying around but I also am going to try a 6 battery 18650 pack running at 11.1vdc to 12.3vdc which I plan to solar charge with a tiny LED solar charge converter. One problem I have with the power supply is that it is very very noisey when there is no bluetooth connection, watch your ears when you disconnect!
I've been using one of those Bluetooth amplifier modules, but without the jack input because they have input polarity protection (Schottky diode). There's another guy on youtube (can't recall the channel) who managed to wire the 2.1mm power incorrectly and the chip just blew. PS, BTL means bridge-tied load.
Many of these PCB proto-boards are not intended to be a mechanism to copy a WISHboard, but as an easy way to design/prototype/build with DIP devices. My first homebrew computer (Z80-A running ZCPR3/ZDOS- a CP/M workalike) was built on 300mm piece of phenolic stripboard with tracks cut to 3 hole intervals and kynar wire.... :)
Excellent video. I heard the Mega328 LCR/Transistor tester is really very good. A few people I work with use it mainly for the Capacitance ESR testing feature.
Hi Julian Just some month ago, I built a very similar thing as that hydrogen speaker! It even had a bamboo case too (Ikea bathroom utility stuff). Mine was intended as a "magic music box" for live action roleplay as a crazy mage/inventor, so it had to look very oldfashioned. I first planned to use the same amp as you have, but then I took a wired version & a small MP3 inside the box. It has a crankshaft and a generator, so you have to turn the crank and...oh magic...music appears! And it had an Ikea Nittio Lamp on top, for extra effects. I used 2 supercaps with a total of 5V and 10F, wich gave about 1minute runtime.....but considering that I had to power the LED plus driver, voltage regulator, amplifier and used a 8W speaker, I was happy about it. besides that, the idea was to use it primarily as a permanent cranked device, like a musicbox. Just let me know if you want some pictures or so...thanks for reading. Emilia
Oh cool! I was also thinking of Ikea for the wooden box - I'm sure I saw some wooden storage boxes last time I was there. I'm looking for a bit longer runtime than 1 minute! Hoping to match the 4 hour claim made for the Hydrogen speaker. Yeah, please send pictures - yt@256.uk
Julian Ilett The short runtime was almost only because of the light. When I unplugged it, it was already about 5min. Quite remarkable, when you consider the very small voltage range I was able to use on that 5V 10F capacitor bank. The amplifiert cut off at about 4.5V ;)
The 5V Amp I used just cuts off. I was quite surprised to be honest. It was one of these supercheap (0.90$) 2x3W Amps. The bluetooth one, idk, but when I unplug the power it "bangs" in the speakers ;) p.s. don't pin me on the 4.5V as a value, that's what I remember from measuring....I sold the box for 120$ to a guy who was totally amazed about it on my first day showing it off at an LARP event XD
Found it at alicehappy858 . Have owned one already built, gave that to a friend so he would get into electronics, and bought another diy kit. This info will be good, but, so far the unit works amazingly. Looking forward to what new info you can provide. Your videos are all I need here, and my patreon donation is paid for by these videos on the regular channel and that is fine. Very happy with your explorations. Saving Alices858 page, thanks.
Great post bag Julian. Appreciated you going into depth on the protoboards along with comments😀 Please do a video on the component tester. Might be time to upgrade. Thank you👍
From what i could see from the page of the super cap audio amp they are using maxwell D cell(350F 2.7V) caps, the "H²" has 6-9 of them, 1F at 2.7=+-1mW/h so it has +-2.1-3.15W/h of energy ideally, boost converter and minimum voltage will reduce it even more. Pretty much means than the 4 hours are very optimistic.(being very soft)
If you are going to use the amplifier at the lower end of it's voltage rating you will be lucky to get more than a watt or two into 4 volts and I doubt you will even get 1 watt into 8 ohms. Obviously the higher power to lower battery life would be. Note that some of these Blu Tooth modules have quite a high QI
I had the same idea a couple years back. I bought 18 500F/2.7v EDLC caps and built a 15v +/- 230F +/- bank. I used 2.4v Zeners to keep the caps close to balanced. While it starts my car, it really wasn't a good power well for amplifiers. I used a TDA7297 class D amp and drove two 8 inch drivers for about 30 minutes at half volume. Not too bad for what it is. But not very usable time wise. So I ended up just using recovered laptop lithium batteries.
Glad to hear this! I have a few old laptop power supplies and a decent buck converter. How many amps do the super caps charge at? EDIT: Just read up on the LTC3780. Impressive chip!
BTL was used in the earlier days as Balanced Transformer Less which, in the day was to account for the "new" technology of the time of audio amplifiers without an output transformer. It may have changed meanings now of course but that was the original meaning of BTL.
Hi Julian, I was that impressed with the component tester I ordered one, I have a couple allready, one I blew up with a charged capacitor, and the other looks like this but doesnt have anything like the functionality.
I'm not sure I you persuade the project w the speakers, I highly recommend 'mdf' wood plates. They are rather cheap, and have good audio performance. Plus ofc imo get some better speakers, you won't get to far with 2,25". Although price is important to you I'd recommend tang band 3,5" woofers. If you want more information, lmk and I'll give you more details since I build my own class d boombox currently.
BTL = bridge tie load. I'm not a high level expert, just a nominal hobbyist,,, it means that these amp chips are capable of 4 channels, or by bridging 2x2 , you get a stronger 2 channel output. Also,, I think you would be better off using a lesser power hog of an amp for your project, like the PAM8403. 5 volts , 3 watts per channel. I've messed with these, and they are pretty decent for what they are, that is,, if you don't really need the Bluetooth aspect.
bluetooth 4 is unfortunately not the latest version, there is bluetooth 5.0 by now. also if you run the unit hard, i suggest adding a small heatsink, akin to the ones you'd mount on a razzberry pie processor.
Better than chip board for the case, MDF. Easier to get good edges with a decent cutting blade, can stain and paint more easily too, with a better final finish. Laminated multi-colour sheets of MDF can look cool.
I've run the numbers for the supercapacitor powered speaker project, and they look reasonable. The specs for the TDA7492P show it draws a quiescent power of around 0.6W at 20V. It'll be less than that for lower voltages, but there will be other losses on the board. Let's say 0.5W avg over 8-20V. A couple of reasonably efficient speakers at a typical listening volume in a quiet room would require around 0.2W each on average. Let's say 0.5W for the two, allowing for inefficiency of the amp. Total 1W average, ballpark. With 8 x 700F 2.5V capacitors in series, you get a 700/ 8 = 87.5F 20V combined capacitor. By my calculation the energy released in dropping this from 20V to 8V works out at 87.5 x (20*20 - 8*8) / 7200 = 4Wh. So at an average of 1W that should last around 4 hours. This will vary considerably depending on actual board and speaker efficiency, and particularly on volume, but it sounds usable. One problem is that the available power drops rapidly as the supply voltage drops. The TDA7492P specs show around 4W per speaker at 8W as compared to 25W at 20V. So at louder volumes the distortion will increase rapidly as the supply voltage drops. It would be tempting to consider a boost converter to maintain the supply voltage to the amp as the battery voltage drops. This would also squeeze a little more out of the capacitors, but not much. Allowing the capacitors to drop down to 2V would yield a total of 4.8Wh - a 20% increase. Unfortunately the boost converter inefficiency would cancel out this benefit, and that's before taking into account that maintaining the amp supply at 20V would result in greater quiescent losses in the amp. I'll be interested to see how this all works out in practice.
The problem with super capacitors is that they store very little total capacity.. I did some rough calculations.. 2.5v 700f is about 0.5WH of total store energy.. So if u connect lets say 8 capcitors in series to get 20v total you will have only 4WH of total capacity... So that means if you draw 4W of power from ur capacitors (or play music at 4w power) you can expect les then 1 hour of working time.. Or lets say if you crank up the volume to about 10W you will drain the capacitors down in less then 15-20 min.. So thats a short time for listening music :S You can ofcourse add more capacitors to get more usable capacity but then you will need at least 16 or even more capacitors and that can get expensive realy fast and even then you would not get more than 1 hour of music time.. So yes it is doable but not on the budget :S
I had no luck with cheap Chinese PCBs because tracks would peal off when soldering - paper was the worst -. Put minimal heat in and maybe tracks will stay put.
Julian I bought 2 of these amps claiming they operated from 24 volts, I ran them for about 20 mins and then the bluetooth died. Having checked the board the voltage regulator for the 3.3v bluetooth module had gone short circuit damaging the module. Also check the inductors, they run mighty hot at 24 volt, they work fine at 12v.. I'm still awaiting a refund for the 2 that died.
The Component Tester is just the graphical Version of the Standard (textline) testers and a little bit slower. My first one, I destroyed them by testing a not unloaded capacitor. Don't know, whats going wrong with the Tester, I belive the ATMEGA has been damaged, but the Chip alone isn't able to get (I didn't found it). A second kit didn't work (got unprotected ATMEGA chip, most probably also damaged). I'm hopefully, that the last ordered kit will work better.
Just bought one of these.(bt amplifier) works perfect. Plus goes to the middle pin, in the 2.1 D.C. Jack. I could not find this info on the web. I drive mine with 19volts
Julian is that aux port on the bluetooth amp board working? I have used the same board in a project posted on my channel and the aux port although routed, only activates when a device is connected to the bluetooth module which makes it unusable.
I've traced the signal as well and it is routed where it's supposed to but I believe power to the pre-amp is controlled through a mosfet, that only get's activated when there is a BT connection. Though I'm not 100% sure on this as I haven't investigated the issue thoroughly, that's why I was asking if you gave this a test.
VoltLog That's entirely correct, the shutdown input of the amp is fed from the Bluetooth module, so bypassing this with some sort of delayed signal (to avoid a loud power on click) will allow you to use both Bluetooth and aux in. I made a video of this mod when I put the module in a bose sounddock.
Assuming those are genuine 700F 2.5V capacitors and you will be using them in the 1V to 2.5V range each will be capable of storing about 0.5Wh so 8 of them around 4Wh. So your power amplifier should be using about 1W in order to last for 4h (possible of course but it will be at low volume). My guess is that those are not 700F supercapacitors so you will have less available energy. Also if they are low quality fake ones then they will not be equal in capacity, internal impedance and self discharge so charging them fast will not realy work at all. In order to charge them in 5min you will need to push around 50W during that period (an average of above 3A). You can also compared them with the ones I sent to you that just happens to be 2.5V and 8 in series 220F and while they do not have any protection circuit since they where designed for SBMS they are high quality so they will charge and discharge in a equal way no need for protection if they start up balanced.
Julian Ilett yes the one with aux in is actually an input,I think it was the kmoon one off Amazon,but I have since removed the aux socket as the way it interferes with the Bluetooth module was very irritating.
I have a 250W (probably not really) rated stereo amplifier and im running two 3 watt and 3" to 4" speakers from it its its class D It runs from 5v to 24v (it works best at 12 to 15v with the least idle heat generated. for some reason it heats up if you run it at 24v not hot but warm) and it was only 12$ from amazon. What a deal!!! I can run a 75W RMS speaker from it easily (and even bottom it out if I play it at max volume from two 12v SLA in series!) Very easily bottom it out. AND THE BEST PART IS IT HAS NO SUB-SONIC FILTER WOOOO!! Hooray for 3hz speaker slapping!
So BTL designation means you can bridge the load and use in either mono or stereo? I share you amazement with Ebay offerings recently rec'd 10x15cm single sided copper PCB on FR4 that are only .4mm thick :-) Who could have guessed that they would endeavour to save on the epoxy/glass . I will have to mount them on 1mm backer before drilling. Looking for that now. And another 30 to 70 days for delivery!! :-(
About the bluetooth board, please tell us if its possible to improve range... mine barely reaches 2-3 meters, and its a bare boardd, not even in an enclosure, in direct LOS.
I built that exact component tester a couple of weeks ago cos I destroyed my last one by putting a charged capacitor in it :( but yeah its really nice. the screen is full colour, I guess it must be an OLED? the menu lets you change R, G and B values for the background and text to whatever combo you like. and class D amplifier modules too, I used one based on the TPA3116D2 to make a powered speaker and considering it cost about 3 quid its incredible, the finished thing sounds every bit as good as a commercial active speaker. not bluetooth tho, I put a little mp3 player with SD card slot in it.
i found an Audio Receiver Board Wireless Stereo Music Module around 5-6$ i can recommended also get Acrylic case for it too because I don't want to buy chromecast audio
I believe the AUX is only output, not input. I have the exact same board and never could reliably get this to put out sound for more than half a second whilst the board booted up.
I believe you are correct, now they could have changed it. However I have the same board, though the 50x2 not 25x2 version and in my case, the 3.5mm jack is output, not input. I'm sure @julian Ilett will confirm soon enough which way his boar's jack functions.
I have mine used to power a pair of undercabinet speakers I made and work with an Echo Dot. Sadly, the 3.5 does not seem to function as an input and I'm forced to use the bluetooth only.
Neat I might have to get one of those Bluetooth amps, if it sounds decent. Would be a cool way to drive my shops speakers Too bad about the board itself though, some of it looks like it was picked and placed by a 2 year old Do you have any device to test those super caps? I'm curious to see if their listed specs are accurate (doubt it)
This model amp is...interesting... when you turn it on you get a loud pop then a deafening beep (it doesn't remember its volume settings after a power cycle) and has lots of pops and crackles, even after doing the antenna mod. I wouldn't buy another one
Hard to call that speaker beautiful... It look like some fast made diy project made from scraps... And they ask for it 500$ I can just imagine that build cost is probably around 80-100$ if they buy components straight from Chinese factories... Because seriously its look like wooden tool box that my grandfather had and it have just hole in it with some cheap car speaker cover -_- As for project it self I would recommend thinking about making "sound bar" that you can put under tv. One time I tried making it, very slim one with 4x 6w speakers that I where in my garage but I give up after I could not find any cheap and small board that would separate low frequency sound to separate output(I wanted to use two middle speakers only for bass) Now probably there are dozens of subwoofer boards like that -_-
My kitchen is filling up with those little brown cardboard boxes from China. Get a copy of that component tester's info page before it disappears from the web.
Hi Julian, I'm enjoying the postbag moments, I've been having a far few myself recently. I think Alice has picked up a lot of sales thanks to you! Anyway, I bought the same ATmega component tester (actually from Alice), and after a bit of a hunt, found a case for it if you're interested. www.ebay.co.uk/itm/262906614530 It fits well, although there's a bit of fun building it as the pictures on the listing aren't great, and there are no instructions! I have no idea if mine does the DS18B20, I don't think it does, and the original German opensource project doesn't appear to include that function either... Hmmm... I'll have to search for that source. Maybe the Chinese box shifters have actually started to do dev work too. Would be nice if they shared it back as the original project was open source.
WTF i live in hong kong and my mail come very late, up to a month and a half. banggood take month some ebay orders takes two weeks if i'm lucky. any how i love your videos great job
you have got 666 videos! Circumstance? No! Hell power 🔯🔱👿. Julian, keep those super-duper great videos coming and use more osciloscope in videos! Thank you!
BTL is bridge tied load.
A bridge-tied load configuration consists of one amplifier driving one side of a load and another amplifier (with an inverted signal from the first amplifier) driving the other side of the load. This results in 2x more voltage swing across the load than you would have in a single-ended configuration where one side of the load is tied to an amplifier and the other side to ground. Twice the voltage swing across the load equates to 4x the power to the load (P = V^2/R). So, a BTL load configuration offers 4x more power to the load than a single ended configuration from the same supply voltage. Be aware, that BTL amplifiers dissipate 4x the heat of a Single-Ended amplfier under the same supply voltage and load conditions. Refer to the TPA7x1 series parts in the applications section for more on BTL. Also note that the output DC blocking capacitors are NOT required in the BTL configuration. Since the load is tied across two amplifiers with the same DC bias and the signal across the load is the difference between the amplifier outputs, the DC bias is removed.
According to e2e.ti.com/support/amplifiers/audio_amplifiers/w/design_notes/1554.what-is-btl-configuration
Can't wait to see the new project take shape. I think I'll build it along with you!
i ordered a TPA7492P literally like 2 days ago and now I see youve ordered one too! Ive heard really good things about them!
Those particular breadboard pcbs have the very useful feature of facilitating the placement of decoupling capacitors very close to the ICs. Good Buy. Best wishes.
Thank you Julian for keeping interest fluid with electronics. You and Big Clive are great inspirations for me!
BTL is "Bridged Tied Load, witch means that the amplifier can utilize the full voltage swing, of the power supply.
I have a few of the audio amplifier boards, but without the jack, and with 2 x 50W instead. The quality is very good, and fits tons of projects perfectly. I'll look forward to what you come up with, then maybe I can use my spare board for a new project.
Cheers for the videos, I'm learning a lot from you that I can use at the electronics technician education I've applied for.
How about inviting BigClive on Postbag #100.....Both of you reviewing new products in your trademark styles......
Julian, the aux input on that board is not an input, it's a line/headphone output! All the eBay descriptions selling that module get it wrong. I know, I've tried several.😣
... They're also very static sensitive, so watch out!
I so support this.
We need to be sure that BigClive and Julian are into doing a video together. It would be cool, but they need to make that decision.
I love a good postbag and yours always hit the mark. If I had the time I'd start doing them with all the stuff I get. Thanks to you putting me onto BangGood, I picked up a genuine Skyrc B6 Imax charger for $30 US.
I built this bluetooth amp project into a ceiling suspended shelf with two old pioneer car stereo speakers and three GU10 12v LED spotlights! It will eventually be suspended over my work station to add a bit of extra light and entertainment to my tinkering time. Like you I planned to run it off supercaps but had my order cancelled, at the moment I am running it off a 1200ma 12v dc power supply I had lying around but I also am going to try a 6 battery 18650 pack running at 11.1vdc to 12.3vdc which I plan to solar charge with a tiny LED solar charge converter. One problem I have with the power supply is that it is very very noisey when there is no bluetooth connection, watch your ears when you disconnect!
BTL == Bridge Tied Load which means that the amplifier either uses H bridged stages or more commonly, that the two channels may be bridged.
I've been using one of those Bluetooth amplifier modules, but without the jack input because they have input polarity protection (Schottky diode). There's another guy on youtube (can't recall the channel) who managed to wire the 2.1mm power incorrectly and the chip just blew. PS, BTL means bridge-tied load.
You don't need to be afraid for the LM13700, they are still "ACTIVE", means in production, by TI
www.ti.com/product/LM13700
Many of these PCB proto-boards are not intended to be a mechanism to copy a WISHboard, but as an easy way to design/prototype/build with DIP devices. My first homebrew computer (Z80-A running ZCPR3/ZDOS- a CP/M workalike) was built on 300mm piece of phenolic stripboard with tracks cut to 3 hole intervals and kynar wire.... :)
Excellent video. I heard the Mega328 LCR/Transistor tester is really very good. A few people I work with use it mainly for the Capacitance ESR testing feature.
Looking forward to what you come up with on the super capacitor stereo project. The idea is quite interesting if it works
Hi Julian
Just some month ago, I built a very similar thing as that hydrogen speaker!
It even had a bamboo case too (Ikea bathroom utility stuff). Mine was intended as a "magic music box" for live action roleplay as a crazy mage/inventor, so it had to look very oldfashioned.
I first planned to use the same amp as you have, but then I took a wired version & a small MP3 inside the box.
It has a crankshaft and a generator, so you have to turn the crank and...oh magic...music appears!
And it had an Ikea Nittio Lamp on top, for extra effects.
I used 2 supercaps with a total of 5V and 10F, wich gave about 1minute runtime.....but considering that I had to power the LED plus driver, voltage regulator, amplifier and used a 8W speaker, I was happy about it. besides that, the idea was to use it primarily as a permanent cranked device, like a musicbox.
Just let me know if you want some pictures or so...thanks for reading.
Emilia
Oh cool! I was also thinking of Ikea for the wooden box - I'm sure I saw some wooden storage boxes last time I was there. I'm looking for a bit longer runtime than 1 minute! Hoping to match the 4 hour claim made for the Hydrogen speaker.
Yeah, please send pictures - yt@256.uk
Julian Ilett
The short runtime was almost only because of the light. When I unplugged it, it was already about 5min.
Quite remarkable, when you consider the very small voltage range I was able to use on that 5V 10F capacitor bank. The amplifiert cut off at about 4.5V ;)
Does the amplifier cut off cleanly at 4.5V or does it get very distorted then cut off?
The 5V Amp I used just cuts off. I was quite surprised to be honest. It was one of these supercheap (0.90$) 2x3W Amps.
The bluetooth one, idk, but when I unplug the power it "bangs" in the speakers ;)
p.s. don't pin me on the 4.5V as a value, that's what I remember from measuring....I sold the box for 120$ to a guy who was totally amazed about it on my first day showing it off at an LARP event XD
Emilia Fairbrook mind posting pictures to an imguir or similar so we can all look at them, that project seems quite neat
Found it at alicehappy858 . Have owned one already built, gave that to a friend so he would get into electronics, and bought another diy kit. This info will be good, but, so far the unit works amazingly. Looking forward to what new info you can provide. Your videos are all I need here, and my patreon donation is paid for by these videos on the regular channel and that is fine. Very happy with your explorations. Saving Alices858 page, thanks.
Need to put a bit of plastic on the back side of mine so I do not blow it up.
Great post bag Julian. Appreciated you going into depth on the protoboards along with comments😀
Please do a video on the component tester. Might be time to upgrade.
Thank you👍
From what i could see from the page of the super cap audio amp they are using maxwell D cell(350F 2.7V) caps, the "H²" has 6-9 of them, 1F at 2.7=+-1mW/h so it has +-2.1-3.15W/h of energy ideally, boost converter and minimum voltage will reduce it even more. Pretty much means than the 4 hours are very optimistic.(being very soft)
+Julian Ilett bluetooth 4.0 is not the latest version ;)
the galaxy S8 comes with bluetooth 5.0 which is able to connect to 2 different devices
I agree on the limited ebay protoboard options. Like trying to find a very small protoboard for sensor hookups with power rails can't be found..
If you are going to use the amplifier at the lower end of it's voltage rating you will be lucky to get more than a watt or two into 4 volts and I doubt you will even get 1 watt into 8 ohms. Obviously the higher power to lower battery life would be. Note that some of these Blu Tooth modules have quite a high QI
I had the same idea a couple years back. I bought 18 500F/2.7v EDLC caps and built a 15v +/- 230F +/- bank. I used 2.4v Zeners to keep the caps close to balanced. While it starts my car, it really wasn't a good power well for amplifiers. I used a TDA7297 class D amp and drove two 8 inch drivers for about 30 minutes at half volume. Not too bad for what it is. But not very usable time wise. So I ended up just using recovered laptop lithium batteries.
That's pretty much what I'm anticipating :)
Genius!!! I am gonna order the parts next month! The quick charging is all I needed to hear.
Quick charging = lots of amps. I'm thinking laptop power supply, but may also need a LT3780 module between the laptop PSU and the capacitors.
Glad to hear this! I have a few old laptop power supplies and a decent buck converter. How many amps do the super caps charge at?
EDIT: Just read up on the LTC3780. Impressive chip!
eBay listing for the capacitors says up to 40A :)
That would really be something! I feel like I need gloves.
Postbag. I love getting things in the mail. Especially Electronics! Carry on, good Man. Fascinating.
BTL was used in the earlier days as Balanced Transformer Less which, in the day was to account for the "new" technology of the time of audio amplifiers without an output transformer. It may have changed meanings now of course but that was the original meaning of BTL.
Hi Julian, I was that impressed with the component tester I ordered one, I have a couple allready, one I blew up with a charged capacitor, and the other looks like this but doesnt have anything like the functionality.
I'm not sure I you persuade the project w the speakers, I highly recommend 'mdf' wood plates. They are rather cheap, and have good audio performance. Plus ofc imo get some better speakers, you won't get to far with 2,25". Although price is important to you I'd recommend tang band 3,5" woofers. If you want more information, lmk and I'll give you more details since I build my own class d boombox currently.
BTL = bridge tie load.
I'm not a high level expert, just a nominal hobbyist,,, it means that these amp chips are capable of 4 channels, or by bridging 2x2 , you get a stronger 2 channel output.
Also,, I think you would be better off using a lesser power hog of an amp for your project, like the PAM8403. 5 volts , 3 watts per channel. I've messed with these, and they are pretty decent for what they are, that is,, if you don't really need the Bluetooth aspect.
The boombox project looks fun! Also be interested in watching the component tester kit build, as thought of getting one myself.
Cheers.
bluetooth 4 is unfortunately not the latest version, there is bluetooth 5.0 by now. also if you run the unit hard, i suggest adding a small heatsink, akin to the ones you'd mount on a razzberry pie processor.
Good post bag! I may buy some of those breadboard pcbs and I have a assembled component test I just got identical to your kit. Good stuff.
every time I get a package I the mail I here Post Baag...
Better than chip board for the case, MDF. Easier to get good edges with a decent cutting blade, can stain and paint more easily too, with a better final finish. Laminated multi-colour sheets of MDF can look cool.
I've run the numbers for the supercapacitor powered speaker project, and they look reasonable. The specs for the TDA7492P show it draws a quiescent power of around 0.6W at 20V. It'll be less than that for lower voltages, but there will be other losses on the board. Let's say 0.5W avg over 8-20V. A couple of reasonably efficient speakers at a typical listening volume in a quiet room would require around 0.2W each on average. Let's say 0.5W for the two, allowing for inefficiency of the amp. Total 1W average, ballpark. With 8 x 700F 2.5V capacitors in series, you get a 700/ 8 = 87.5F 20V combined capacitor. By my calculation the energy released in dropping this from 20V to 8V works out at 87.5 x (20*20 - 8*8) / 7200 = 4Wh. So at an average of 1W that should last around 4 hours. This will vary considerably depending on actual board and speaker efficiency, and particularly on volume, but it sounds usable.
One problem is that the available power drops rapidly as the supply voltage drops. The TDA7492P specs show around 4W per speaker at 8W as compared to 25W at 20V. So at louder volumes the distortion will increase rapidly as the supply voltage drops. It would be tempting to consider a boost converter to maintain the supply voltage to the amp as the battery voltage drops. This would also squeeze a little more out of the capacitors, but not much. Allowing the capacitors to drop down to 2V would yield a total of 4.8Wh - a 20% increase. Unfortunately the boost converter inefficiency would cancel out this benefit, and that's before taking into account that maintaining the amp supply at 20V would result in greater quiescent losses in the amp. I'll be interested to see how this all works out in practice.
The problem with super capacitors is that they store very little total capacity.. I did some rough calculations.. 2.5v 700f is about 0.5WH of total store energy.. So if u connect lets say 8 capcitors in series to get 20v total you will have only 4WH of total capacity... So that means if you draw 4W of power from ur capacitors (or play music at 4w power) you can expect les then 1 hour of working time.. Or lets say if you crank up the volume to about 10W you will drain the capacitors down in less then 15-20 min.. So thats a short time for listening music :S You can ofcourse add more capacitors to get more usable capacity but then you will need at least 16 or even more capacitors and that can get expensive realy fast and even then you would not get more than 1 hour of music time.. So yes it is doable but not on the budget :S
I had no luck with cheap Chinese PCBs because tracks would peal off when soldering - paper was the worst -. Put minimal heat in and maybe tracks will stay put.
Julian I bought 2 of these amps claiming they operated from 24 volts, I ran them for about 20 mins and then the bluetooth died. Having checked the board the voltage regulator for the 3.3v bluetooth module had gone short circuit damaging the module. Also check the inductors, they run mighty hot at 24 volt, they work fine at 12v.. I'm still awaiting a refund for the 2 that died.
nice video, btw BTL means bridge tied load, if im not mistaken. :)
I'm going to build a Bluetooth speaker box using the amp you reviewed. Do you think a rotary encoder could be used to replace the volume buttons?
The Component Tester is just the graphical Version of the Standard (textline) testers and a little bit slower. My first one, I destroyed them by testing a not unloaded capacitor. Don't know, whats going wrong with the Tester, I belive the ATMEGA has been damaged, but the Chip alone isn't able to get (I didn't found it). A second kit didn't work (got unprotected ATMEGA chip, most probably also damaged). I'm hopefully, that the last ordered kit will work better.
Just bought one of these.(bt amplifier) works perfect. Plus goes to the middle pin, in the 2.1 D.C. Jack. I could not find this info on the web. I drive mine with 19volts
Are you going to do something special on the 100# post bag episode?
I'll be making a bold claim!
+Julian Ilett "A bold claim" - like, 'I buy tons of crap on ebay!' If so, I would be happy to confirm your claim. ;-) (PS - me, too!)
hah, I just ordered one of these TDA7492P, still waiting but will make my own powerbank powered mobile boom box :)
I have a very similar component tester and the zif socket is crap, it broken after only a few uses. I think I'll put leads on it.
Julian is that aux port on the bluetooth amp board working? I have used the same board in a project posted on my channel and the aux port although routed, only activates when a device is connected to the bluetooth module which makes it unusable.
That's odd. I've not tried it yet (no speakers), but I've traced the tracks from the aux socket through to the amplifier input pins.
I've traced the signal as well and it is routed where it's supposed to but I believe power to the pre-amp is controlled through a mosfet, that only get's activated when there is a BT connection. Though I'm not 100% sure on this as I haven't investigated the issue thoroughly, that's why I was asking if you gave this a test.
VoltLog That's entirely correct, the shutdown input of the amp is fed from the Bluetooth module, so bypassing this with some sort of delayed signal (to avoid a loud power on click) will allow you to use both Bluetooth and aux in. I made a video of this mod when I put the module in a bose sounddock.
Assuming those are genuine 700F 2.5V capacitors and you will be using them in the 1V to 2.5V range each will be capable of storing about 0.5Wh so 8 of them around 4Wh. So your power amplifier should be using about 1W in order to last for 4h (possible of course but it will be at low volume).
My guess is that those are not 700F supercapacitors so you will have less available energy. Also if they are low quality fake ones then they will not be equal in capacity, internal impedance and self discharge so charging them fast will not realy work at all.
In order to charge them in 5min you will need to push around 50W during that period (an average of above 3A).
You can also compared them with the ones I sent to you that just happens to be 2.5V and 8 in series 220F and while they do not have any protection circuit since they where designed for SBMS they are high quality so they will charge and discharge in a equal way no need for protection if they start up balanced.
BTL Bridge-tied Load? en.wikipedia.org/wiki/Bridge-tied_load
Yes, I looked at a few other data sheets and came to the same conclusion - Cheers Steve :)
Also, just out of interest, I could only find those Prototype boards on eBay.com, not eBay.co.uk not realising you'd posted the links *doh*
back in the old days it stood for balanced transformer-less
The reason to get the 50w amp is if they are claiming 50 you'll end up getting 15 rms.
Why not implementing things like V-USB into the Pic to make the laser sword thingy controllable via USB?
hi julian I've got the with and without aux in and the one with the aux in suffers from a wine when used,but when removed from the board all is well.
Does the Aux socket work as an input?
Julian Ilett yes the one with aux in is actually an input,I think it was the kmoon one off Amazon,but I have since removed the aux socket as the way it interferes with the Bluetooth module was very irritating.
I have a 250W (probably not really) rated stereo amplifier and im running two 3 watt and 3" to 4" speakers from it its
its class D
It runs from 5v to 24v (it works best at 12 to 15v with the least idle heat generated. for some reason it heats up if you run it at 24v not hot but warm)
and it was only 12$ from amazon. What a deal!!! I can run a 75W RMS speaker from it easily (and even bottom it out if I play it at max volume from two 12v SLA in series!) Very easily bottom it out.
AND THE BEST PART IS IT HAS NO SUB-SONIC FILTER WOOOO!! Hooray for 3hz speaker slapping!
So BTL designation means you can bridge the load and use in either mono or stereo?
I share you amazement with Ebay offerings recently rec'd 10x15cm single sided copper PCB on FR4 that are only .4mm thick :-) Who could have guessed that they would endeavour to save on the epoxy/glass . I will have to mount them on 1mm backer before drilling. Looking for that now. And another 30 to 70 days for delivery!! :-(
Could you do a video on how to use a component tester?
About the bluetooth board, please tell us if its possible to improve range... mine barely reaches 2-3 meters, and its a bare boardd, not even in an enclosure, in direct LOS.
love your videos i am a newby in elctrics so cool to learn
I built that exact component tester a couple of weeks ago cos I destroyed my last one by putting a charged capacitor in it :(
but yeah its really nice. the screen is full colour, I guess it must be an OLED? the menu lets you change R, G and B values for the background and text to whatever combo you like.
and class D amplifier modules too, I used one based on the TPA3116D2 to make a powered speaker and considering it cost about 3 quid its incredible, the finished thing sounds every bit as good as a commercial active speaker. not bluetooth tho, I put a little mp3 player with SD card slot in it.
I have the same amp. It seems like the AUX is only output and not input. Cant connect it to my tv...
I have brought this same pcb but it's not giving sound on audio jack and on bloototh sound is getting cut in middle middle what can be the issue
13:50 focus on some of the tracks in the middle of the board while moving your head and tell me the breadboard is moving for you too! #VOODOOMAGIC
One of the inductors on the BT amp module looks misaligned. Any damage or just bad soldering ?
Looks fine to me, just a cosmetic misalignment.
will you ever finish MUPPET? i love that thing :/
i found an Audio Receiver Board Wireless Stereo Music Module around 5-6$ i can recommended also get Acrylic case for it too because I don't want to buy chromecast audio
waiting your tda 7492 speakers project
Could you do a comparison of those testers? They look very interesting and handy. thanks
btl = bridge tied load. dont use -ve on speakers as common.
I believe the AUX is only output, not input. I have the exact same board and never could reliably get this to put out sound for more than half a second whilst the board booted up.
I believe you are correct, now they could have changed it. However I have the same board, though the 50x2 not 25x2 version and in my case, the 3.5mm jack is output, not input. I'm sure @julian Ilett will confirm soon enough which way his boar's jack functions.
I'll be disappointed if it's not an input :(
I have mine used to power a pair of undercabinet speakers I made and work with an Echo Dot. Sadly, the 3.5 does not seem to function as an input and I'm forced to use the bluetooth only.
As far as I know it's just paralleled to the bluetooth module
I assume they use the 3.5mm socket switch to disconnect the bluetooth module
i have that DIY kit. its fantastic !!!!
Lol, I bought this amplifier recently and trying to make a wooden Bluetooth Boombox with 4 18650's in Parallel with a tp4056.
Maybe you can dead bug the tac switch over top of the pic?
Neat I might have to get one of those Bluetooth amps, if it sounds decent. Would be a cool way to drive my shops speakers
Too bad about the board itself though, some of it looks like it was picked and placed by a 2 year old
Do you have any device to test those super caps? I'm curious to see if their listed specs are accurate (doubt it)
Yes, one of the inductors is a bit wonky :)
LeiserGeist these class d amplifier modules (tpa3116 or tda7xxx family) do sound quite alright in my experience!
This model amp is...interesting... when you turn it on you get a loud pop then a deafening beep (it doesn't remember its volume settings after a power cycle) and has lots of pops and crackles, even after doing the antenna mod. I wouldn't buy another one
on that Bluetooth amp im pretty sure the volume is controlled on the amp there not thru Bluetooth
How long do you wait for most of your Ebay deliveries J ?
About 3 weeks.
use 5 caps @ 2.5 volt each this is the best for this board
Isn't it great when things line up.
I save the small cardboard boxes to store finished projects I'm not using right away
Hard to call that speaker beautiful... It look like some fast made diy project made from scraps...
And they ask for it 500$ I can just imagine that build cost is probably around 80-100$ if they buy components straight from Chinese factories... Because seriously its look like wooden tool box that my grandfather had and it have just hole in it with some cheap car speaker cover -_-
As for project it self I would recommend thinking about making "sound bar" that you can put under tv.
One time I tried making it, very slim one with 4x 6w speakers that I where in my garage but I give up after I could not find any cheap and small board that would separate low frequency sound to separate output(I wanted to use two middle speakers only for bass) Now probably there are dozens of subwoofer boards like that -_-
Will there be a special for Postbag #100? Maybe a 1 hour Postbag Stream :D
Yes, Postbag 100 will be a bit special ;)
Now there's an idea.
BTL is most likely Balanced Transformer-Less. Or at least, that's what it used to be.
Technically Bluetooth 5.0 is the newest standard :P
I bet you can get something made of flattened bamboo from the dollar store :)
Those transistor testers are clones of German open source project, just for info
For proto board, you can find lot ofmodels on Adafruit : www.adafruit.com/category/124
I'd have to remove and re-solder that wonky SMD inductor.
does this mean those 500f capacitors you got awhile back are going to make an appearance (nevermind).
I've got other plans for them :)
Julian Ilett did you already do the speaker build. would love to see that.
Latest Bluetooth version is 5 not 4
BTL = BRIDGE-TIED LOAD.
My kitchen is filling up with those little brown cardboard boxes from China.
Get a copy of that component tester's info page before it disappears from the web.
Has anyone seen gerbers for similar boards to the ones that julien baught here?
Hi Julian,
I'm enjoying the postbag moments, I've been having a far few myself recently. I think Alice has picked up a lot of sales thanks to you!
Anyway, I bought the same ATmega component tester (actually from Alice), and after a bit of a hunt, found a case for it if you're interested.
www.ebay.co.uk/itm/262906614530
It fits well, although there's a bit of fun building it as the pictures on the listing aren't great, and there are no instructions!
I have no idea if mine does the DS18B20, I don't think it does, and the original German opensource project doesn't appear to include that function either... Hmmm... I'll have to search for that source. Maybe the Chinese box shifters have actually started to do dev work too. Would be nice if they shared it back as the original project was open source.
Sawaddee Krub Form Thailand
22:59 Keep hearing "Lick my face here"...
That might work on a capacitive touch screen :)
WTF
i live in hong kong and my mail come very late, up to a month and a half.
banggood take month some ebay orders takes two weeks if i'm lucky.
any how i love your videos great job
The helium and hydrogen look rubbish... who do the think they are kidding with the price. I' lol bet on yours anytime.
Blueshift sounds like bullshi... wait a second!
sorry to say but it's not an aux it's an output
Bluetooth what? en.wikipedia.org/wiki/Bridge-tied_load
where are your finger puppies? i missed them! greets from germany.
you have got 666 videos! Circumstance? No! Hell power 🔯🔱👿. Julian, keep those super-duper great videos coming and use more osciloscope in videos! Thank you!