Yep, it's definitely the bluetooth. Tried the amp without bluetooth and it works perfectly, tried the bluetooth on something else and I get the same problem.
Now I have limited knowledge on the subject, but I'd love to learn. Would you mind telling me what the problem actually is and why this will solve it?
It's pretty much like that the BT module puts lot of noise onto the audio-outputs and the power-supply lines. By the LC-Filter at the power-input of the BT-module you restrict the path back into the power lines, so noise is blocked. The values for the LC worked for me, i testes different caps empirical. ESR is one of the keys here. Having only one GND connection from/to the BT module makes sure your connection isn't looped and acts as an antenna for the BT module which will conduct into. So you'll have i.e.:
VCC/Power/+
GND
AudioL
AudioR
but not:
VCC/Power/+
GND
AudioL
GND
AudioR
Its a good idea to connect the GND at the amps audio-input.
Forgive me if this is a stupid question, but if the signal does not have a ground, how can it work?
To clarify what I did: I have a headphone where you can plug in aux cables. I connected a 9V battery with + and GND to the module. Then from the module I connected L + R signal with a 10K resistor each to each other (for mono) to one of the aux inputs. The GND from that signal then went back to signal GND on the bluetooth module.
This gave the noise as I experienced it in the full setup with amp etc. as well.
I tried cutting out the signal GND there but as expected then there was just no signal going. Do you want me to connect that GND straight to the battery GND or something?
I will try and check out the LC components, but as is I have a hard time grasping the GND problem.
To clarify what I did: I have a headphone where you can plug in aux cables. I connected a 9V battery with + and GND to the module. Then from the module I connected L + R signal with a 10K resistor each to each other (for mono) to one of the aux inputs. The GND from that signal then went back to signal GND on the bluetooth module.
This gave the noise as I experienced it in the full setup with amp etc. as well.
I tried cutting out the signal GND there but as expected then there was just no signal going. Do you want me to connect that GND straight to the battery GND or something?
I will try and check out the LC components, but as is I have a hard time grasping the GND problem.
To clarify. A single ground is used when the amp and bluetooth device is on the same battery since signal ground and power ground is effectively the same there should be only one ground connection. When you have a separate battery there obviously should be a signal ground.
Did you forget the resistor to ground in your summing network?
This is how it should look:
I'm still trying to figure output why you're making life hard on yourself though. Test the bluetooth module without a summing network at all. Just test each channel separately. If you can't get it to work that way, well therein lies your problem then and you can stop trying.
I did in fact not include a resistor to ground! I will update that, since I used 10k resistors should I use 100k on the gnd? I should note though that I used the same setup without gnd resistor via aux and it worked fine. What is the function of this resistor? Preventing ground loop?
You're right also about first trying stereo output though, I'll try that out first
You're right also about first trying stereo output though, I'll try that out first
Okay, this is getting weirder and weirder to me.
So I'm using this Bluetooth module Bluetooth 4 0 Audio Receiver Board Wireless Stereo Sound Module for Car Phone PC | eBay
You can connect via either Bluetooth or aux via this module.
I did not connect it in mono mode, to get a minimal working example.
I got a volume knob wired in between the signal out of the module and the signal in of the amp. I'm quite certain I wired that one correctly, with the output on the middle terminal and input and GND on either side.
First off: connecting via bluetooth. Bad crackling interference sounding sound. Just plain bad. Strange thing: it is much more present when turning the volume knob all the way up. Increasing the volume via my phone does not at all affect the amount of noise.
Then I connected my phone via the aux input of the Bluetooth module. Clear as a whistle! Turning the volume knob all the way up does not give rise to any noise.
Then I took my girlfriends phone and connected it via Bluetooth, in the beginning there was some noise but now it is actually clear. There is no noise.
This would then suggest to me that it is my phone's Bluetooth that is acting up. However, as I'm writing this I'm listening to my Bose Mobile SoundLink via Bluetooth from my phone, without any problems.
If anyone has an idea what it could be that causes this, I would be very grateful. Am I just really unlucky to have two bluetooth devices that don't seem to work with each other?
So I'm using this Bluetooth module Bluetooth 4 0 Audio Receiver Board Wireless Stereo Sound Module for Car Phone PC | eBay
You can connect via either Bluetooth or aux via this module.
I did not connect it in mono mode, to get a minimal working example.
I got a volume knob wired in between the signal out of the module and the signal in of the amp. I'm quite certain I wired that one correctly, with the output on the middle terminal and input and GND on either side.
First off: connecting via bluetooth. Bad crackling interference sounding sound. Just plain bad. Strange thing: it is much more present when turning the volume knob all the way up. Increasing the volume via my phone does not at all affect the amount of noise.
Then I connected my phone via the aux input of the Bluetooth module. Clear as a whistle! Turning the volume knob all the way up does not give rise to any noise.
Then I took my girlfriends phone and connected it via Bluetooth, in the beginning there was some noise but now it is actually clear. There is no noise.
This would then suggest to me that it is my phone's Bluetooth that is acting up. However, as I'm writing this I'm listening to my Bose Mobile SoundLink via Bluetooth from my phone, without any problems.
If anyone has an idea what it could be that causes this, I would be very grateful. Am I just really unlucky to have two bluetooth devices that don't seem to work with each other?
Just found out that putting my thumb on the module's antenna dramatically decreases the amount of noise.
You can compare the noise with the noise you hear when you have a speaker turned on and the aux plug is close to your phone's headphone jack but not yet plugged in. I suspect it is related.
You can compare the noise with the noise you hear when you have a speaker turned on and the aux plug is close to your phone's headphone jack but not yet plugged in. I suspect it is related.
I've got a question about the 9-ply 12mm birch plywood. I've been on the hunt for this, but as I'm in the U.S. and we somehow still don't use the metric system, I've been seeing a lot of 1/2 inch plywood (which is 12.7mm) and 0.45 inch plywood (which is 11.43mm).
Will either of these be ok or do I need to find 12mm exactly?
Will either of these be ok or do I need to find 12mm exactly?
If you go to the lumber yard and measure the ply you will likely find that the "1/2" is only nominally 1/2". The actual thickness is closer to 12mm so go with that.
Also, ask the nearby lumber yards for "baltic birch". It has a lot more plies and is much nicer to work with than the birch ply you will find at Home Depot or Lowes. Another alternative is the brand Apply Ply. It may be available in your area.
Also look out for Arauco branded ply, it's from Chile made from radiata pine, it's good quality ply that is easy to work with, it is not as good as baltic birch but it's also not as expensive.
Also if the sheet is straight and does not show any voids AND does not have thin veneer as the outer sheets, then 5-ply is also perfectly fine. Actually if these three conditions are fulfilled than it doesn't really matter what the timber is, especially the thin veneer part, it's almost impossible to get clean cuts.
And what Aterren said about thicknesses, if the actual measurement of any ply matches the nominated size then it is only by accident.
Also if the sheet is straight and does not show any voids AND does not have thin veneer as the outer sheets, then 5-ply is also perfectly fine. Actually if these three conditions are fulfilled than it doesn't really matter what the timber is, especially the thin veneer part, it's almost impossible to get clean cuts.
And what Aterren said about thicknesses, if the actual measurement of any ply matches the nominated size then it is only by accident.
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Sourcing crossover components
I am getting ready to order my crossover components. As a reminder, I'm using HP10Ws and PHT407Ns and my block diagram is attached.
Do these components look alright?
For the inductors, is 0.10 Ohm considered "low-DCR"?
For the resistors, the recommended value was 4 ohm, but would these 3.9 ohm ones be ok?
Inductors: 0.3 mH, 14 ga., 0.10 Ohm dcr.
(Inductor Link)
Capacitors: 1.5 uF, 5% tolerance, 630V, dissipation factor < 0.001@1kHz, Metallized Polypropylene Film
(Capacitor Link)
Resistors: 3.9 Ohm, 10W, 10% tolerance
(Resistor Link)
I am getting ready to order my crossover components. As a reminder, I'm using HP10Ws and PHT407Ns and my block diagram is attached.
Do these components look alright?
For the inductors, is 0.10 Ohm considered "low-DCR"?
For the resistors, the recommended value was 4 ohm, but would these 3.9 ohm ones be ok?
Inductors: 0.3 mH, 14 ga., 0.10 Ohm dcr.
(Inductor Link)
Capacitors: 1.5 uF, 5% tolerance, 630V, dissipation factor < 0.001@1kHz, Metallized Polypropylene Film
(Capacitor Link)
Resistors: 3.9 Ohm, 10W, 10% tolerance
(Resistor Link)
Attachments
Your values look good, but they seem a bit overkill to me. Don't take my word for it though
Little update to my situation: an even better way of combatting the noise instead of putting my thumb on the antenna, putting a well-placed piece of aluminium foil on the bottom of the module. Not exactly underneath the antenna but a bit to the side, weirdly enough. The people I know with some background on the subject are quite baffled by it.
Little update to my situation: an even better way of combatting the noise instead of putting my thumb on the antenna, putting a well-placed piece of aluminium foil on the bottom of the module. Not exactly underneath the antenna but a bit to the side, weirdly enough. The people I know with some background on the subject are quite baffled by it.
Boominator Build for a Bicycle
Hi everyone, I stumbled across this thread after doing a lot of research on building a portable speaker system that is attached to a bicycle. I like the design of the boominator, and was thinking of switching the square design into an inverted "U" to fit across the back racks of a touring bicycle, and reducing the speaker set to 2 drivers and 2 tweeters.
The boominator has 10" drivers opposite of each other in the design, with the magnet ends right up against each other, but in my design change, it wouldn't make sense to have these inner speakers (as they would be pointing inward at each other).
My question is, with this design, does the drivers being right next to each other have an additive or synergistic effect? Please keep in mind that I have very little audio expertise, so I may have a lot of followup questions on your replies.
Hi everyone, I stumbled across this thread after doing a lot of research on building a portable speaker system that is attached to a bicycle. I like the design of the boominator, and was thinking of switching the square design into an inverted "U" to fit across the back racks of a touring bicycle, and reducing the speaker set to 2 drivers and 2 tweeters.
The boominator has 10" drivers opposite of each other in the design, with the magnet ends right up against each other, but in my design change, it wouldn't make sense to have these inner speakers (as they would be pointing inward at each other).
My question is, with this design, does the drivers being right next to each other have an additive or synergistic effect? Please keep in mind that I have very little audio expertise, so I may have a lot of followup questions on your replies.
Maybe start a new thread, because this thread is only about the Boominator, and it's not what you want on a bicycle.