80's Boombox Upgrade - adding iphone support via USB port? Power or Power + Aux in?

[HoosierBuddy]

Hey guys,

My old Fisher Boombox upgrade project is progressing. So far I've replaced the speakers and added amplifiers in each of the existing speaker boxes. The thing rocks like never before. Next up is adding support for my iphone... So currently I just plug my iphone into the aux inputs through a 3.5 mm male to RCA Male X 2 adapter. That works great except for the fact my phone runs down eventually. So, I ordered a panel mount usb connector to install thinking I could use it and a VR (to convert 24V to 5V) to plug my phone into the back of the old Fisher for recharging.

THEN...I got to thinking (dangerous) SEEMS like I could wire the usb connector to the AUX in circuit inside the box to send audio directly in via the usb cable rather than having the usb cable supply power and and my existing cable to hook to the aux jacks.

Does that sound feasible?
Are there pins in the usb cable that supply an analog audio signal from a digital source or is it some sort of digital signal which I'm not going to be able to use?
Finally, is the idea of patching into the RCA AUX connectors for the stereo between the jacks and the main board a bad one?

Phil

[Millstonemike]

I would think the iPhone is sending digitized music over the USB port (if it does at all), not analog.

The standard LM7805 type regulator in a TO-220 is good for 1.5 A max and 15 W max with a heat sink. At 1.5 amps, the regulator will exceed its maximum W rating @ ~29 W [(24 V - 5V) * 1.5 A] And it will be very inefficient when running on batteries. There are efficient DC-DC converters but they get expensive in the 1+ amp range.

Perhaps a better solution is an external battery pack designed specifically for phone charging. You could always integrate that inside the box.

[make_some_noise]

It's digital. Giant 80's ghetto-blasters are what got me into audio as a kid. Man those D batteries weren't cheap back then! Would love to see photo's of yours!

[somakmaitra]

Why don't you add a bluetooth 4.0 support it will nullify any contact issue.

[somakmaitra]

Or you can put an MP3 decoder with bluetooth

[Millstonemike]

Or you can put an MP3 decoder with bluetooth

You'll also need to drop down the voltage for either BT modules. The discrete BT/WiFI modules lists operating current of 100 mA (w/ WiFIi off). A standard regulator can do that and you won't be wasting that much battery power. The integrated BT/MP3 decoder doesn't specify a an operating current.

[HoosierBuddy]

Wow. Thanks for all the good info guys. Sounds like I'll just stick with the RCA jacks and attempt to use a USB port just for charging.

Regarding Upgrades....

When I took the Fisher 430K apart and checked the voltage through the power switch, it shows 24 vdc when plugged into AC power. The 2 amplifier boards I bought here on PE are rated for 24VDC

https://www.parts-express.com/Data/D...0-606_HR_0.jpg

but require quite a few amps, so I bought a 5 amp 24 volt external power supply and brought that into the back of the boombox via a jack into the old D-Cell battery compartment. I wired in a relay there to the boombox main power switch that closes when the Fisher gets powered on to send 24 Volts to an amp in each speaker box.

Yes...I am sending an amplified signal to each of the amplified speakers...tried a line out convertor, but it added noise...so I'm working on that still. For right now, keeping the volume knob on the stereo to about 50% or lower results in pretty good sound quality.

I bought a cheap BT card of amazon (xiny)...and mocked it up...but the sound quality was terrible. I sent it back and am going to try another one. The plan is to mount it inside the old battery compartment as well along with an adjustable power supply board set to 5 volts to power it and an external power jack for my cell phone.

Back to (sort of) one of my earlier questions:

Do you think I can solder the BT output pigtail to the connectors coming to the AUX in RCA jacks inside the Fisher? Would the AUX in still work properly with a external source if the BT unit was not paired? I'd kind of like those jacks to sill work, but be "pre-empted" by a BT signal if it's paired.

Phil

[Millstonemike]

Wow. Thanks for all the good info guys. Sounds like I'll just stick with the RCA jacks and attempt to use a USB port just for charging.

Regarding Upgrades....

When I took the Fisher 430K apart and checked the voltage through the power switch, it shows 24 vdc when plugged into AC power. The 2 amplifier boards I bought here on PE are rated for 24VDC

https://www.parts-express.com/Data/D...0-606_HR_0.jpg

but require quite a few amps, so I bought a 5 amp 24 volt external power supply and brought that into the back of the boombox via a jack into the old D-Cell battery compartment. I wired in a relay there to the boombox main power switch that closes when the Fisher gets powered on to send 24 Volts to an amp in each speaker box.

Yes...I am sending an amplified signal to each of the amplified speakers...tried a line out convertor, but it added noise...so I'm working on that still. For right now, keeping the volume knob on the stereo to about 50% or lower results in pretty good sound quality.

I bought a cheap BT card of amazon (xiny)...and mocked it up...but the sound quality was terrible. I sent it back and am going to try another one. The plan is to mount it inside the old battery compartment as well along with an adjustable power supply board set to 5 volts to power it and an external power jack for my cell phone.

Back to (sort of) one of my earlier questions:

Do you think I can solder the BT output pigtail to the connectors coming to the AUX in RCA jacks inside the Fisher? Would the AUX in still work properly with a external source if the BT unit was not paired? I'd kind of like those jacks to sill work, but be "pre-empted" by a BT signal if it's paired.

Phil

You could probably pick off the stereo signal from the Fisher's internal pre-amp just before it goes to the power amp.

Yes you can parallel the BT modules output with the "Aux" input. It might be better still if you power-off the BT module when using the aux. Why the relay?

[HoosierBuddy]

. Why the relay?

I see wires within the box that look like they might be L&R inputs to the amp. Next time I take the case off, I'll post a picture here.

Without the relay, (which I originally did not have), when the supplementary 24V power supply was plugged in, the new amps in each speaker were powered all the time...unless I unplugged the power supply from either the wall or the back of the box. So, the relay is installed now to cut power to the speaker amps when the Fisher's main power button is in the off position...if that makes sense. So, when I want to listen to the unit, I push the power button and that turns it on and the relay clicks and turns on power to the amps in each speaker.

Phil