M70 & M90 with hardwired bluetooth module mod.

trippy1313

trippy1313

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JOE! I might have figured out that ground loop issue!!!

Do you have the module ground wire connected???

If so, DISCONNECT IT!!! The module appears to ground just fine through the RCA plugs. The ground wire appears to make the loop.

At least that's what I'm noticing. Also, this way, I only notice a very very low buzz, that goes away if your connections are really clean.

I've been playing with a bunch of different ways to connect before I instal. On my 15v boxes, I'm testing using a 12v regulator I picked up at RadioShack for $2.

http://www.radioshack.com/radioshack-12v-fixed-voltage-regulator-7812/2761771.html

With this you have to solder the module ground to this regulator, but doesn't need an input ground, as it still has it from the RCA's. Only need input+/ouput+.
 
blu_fuz

blu_fuz

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^ You are exactly right, this module will ground through the audio jack so the module will work if you only run the +positive to it.


Now keeping the -negative wire disconnected to the module, I can still hear the interference in the audio.



What I want to try is ground the module, but DO NOT solder line-in to the -negative audio input on the boombox board only solder the +positive audio input to the +positive line-in. Maybe that will keep the noise out.
 
trippy1313

trippy1313

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blu_fuz said:
^ You are exactly right, this module will ground through the audio jack so the module will work if you only run the +positive to it.


Now keeping the -negative wire disconnected to the module, I can still hear the interference in the audio.



What I want to try is ground the module, but DO NOT solder line-in to the -negative audio input on the boombox board only solder the +positive audio input to the +positive line-in. Maybe that will keep the noise out.
Click to expand...
That is definitely worth a try. Ive been using that one I opened up for testing. Maybe I'll try the same thing, I only get a low pitch buzz on my 931, I'll see if I can try that too.
 
trippy1313

trippy1313

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Well I tried that. I'm not sure why but on the 931, it made it way worse. I shoulda recorded it, but made it sound like a short, sounded like I was going to blow the amp. Not sure why or if it'll be different on the M70.
maybe I did it wrong, it's at work so I'll look at it Monday.
 
stosoorok

stosoorok

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I have one question, why do you guys spend so much money on BT mods when you can get BT receiver ~2$ and dc-dc converter ~2$?

BT audio receiver: http://www.aliexpress.com/item/USB-Wireless-Bluetooth-3-5mm-Music-Audio-Car-Handsfree-Receiver-Adapter/32305873494.html?ws_ab_test=201526_5,201527_1_71_72_73_74_75,201409_3

DC-DC step down converter: http://www.aliexpress.com/item/DC-DC-Auto-Boost-Buck-adjustable-step-down-Converter-XL6009-Module-Solar-Voltage/2036629248.html?ws_ab_test=201526_5,201527_1_71_72_73_74_75,201409_3
 
O

Okelly

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^ I believe it's about keeping the integrity of the box but updating to be used with today's technology. I personally would love to have all my boxes setup with Bluetooth and have them look factory because I don't see myself making tons of cassettes of new music just to use the box. The phone I carry on my pocket has unlimited music.
 
trippy1313

trippy1313

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stosoorok said:
I have one question, why do you guys spend so much money on BT mods when you can get BT receiver ~2$ and dc-dc converter ~2$?

BT audio receiver: http://www.aliexpress.com/item/USB-Wireless-Bluetooth-3-5mm-Music-Audio-Car-Handsfree-Receiver-Adapter/32305873494.html?ws_ab_test=201526_5,201527_1_71_72_73_74_75,201409_3

DC-DC step down converter: http://www.aliexpress.com/item/DC-DC-Auto-Boost-Buck-adjustable-step-down-Converter-XL6009-Module-Solar-Voltage/2036629248.html?ws_ab_test=201526_5,201527_1_71_72_73_74_75,201409_3
Click to expand...
I've thought of doing something like this, but then blu_fuz found a module with a range of over 100ft.

Well worth it. I was using a normal one with a range of 30ft max, it's fine inside, but completely useless outside.
 
stosoorok

stosoorok

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trippy1313 said:
I've thought of doing something like this, but then blu_fuz found a module with a range of over 100ft.

Well worth it. I was using a normal one with a range of 30ft max, it's fine inside, but completely useless outside.
Click to expand...
Okay sounds good, I have to test this 2$ receivers range. Btw, you can add a small wifi antenna with pigtail to this cheap receiver! (soldering skills needed of course)

Antenna with pigtail: http://www.aliexpress.com/item/1-2dBi-Dual-Band-WiFi-RP-SMA-Antenna-1-U-fl-Cable-for-Bulkhead-Pigtail-Extension/32278857905.html?ws_ab_test=201526_5,201527_1_71_72_73_74_75,201409_3
 
blu_fuz

blu_fuz

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Did another BT home stereo mod tonight. Super easy and nice clean audio with no feedback.


image.jpg
 
trippy1313

trippy1313

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No feedback is good. Anything different about this setup? Other than different device of course?

I'm curious if it's a matter of the overall ground quality throughout the device itself.
 
blu_fuz

blu_fuz

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I'm also not soldering the rca cables to the board, just plugging them into the aux-in rca jacks.
 
Cpl-Chronic

Cpl-Chronic

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OK. This might be a long shot but try using shielding foil or metal box to protect the BT module from the RF being thrown around inside the cabinet. I had to magnetically shield the areas around the pre-amp controls on Vintage Man's Prosonic LED MOD. The PWM regualtors would create RF spikes, at each LED & would shunt across the controls introducing static & noise. I shielded those areas with ground & the noise went away. I'm wondering if the BT modules don't shield themselves to RF interference because of FCC rules or something...

Worth a try. You have to use copper foil or a metal box that is grounded to effectively shunt any RF before it reaches the module since you've buried it inside a 30 year old box that has a real transformer & rectifier, vs all silicon power regulation...controls & circuits that are not shielded well, etc. put a metal enclosure of some kind around the module & then ground the metal enclosure to the ground screw of the blaster. BAM!! Should work if that is the culprit.
 
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