Adding RCA inputs to a little boombox

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Electro-Voice 664
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Adding RCA inputs to a little boombox

Post by Electro-Voice 664 » Thu Feb 10, 2005 5:17 pm

I want to solder some RCA jacks into a little boombox that has no inputs.

The plan is to hear a mix through this and be able to still switch the loudness buttom in and out.

Can anyone tell me what wires I can splice into?

I was thinking if I could find the cassette feed wires and use those so I could switch the input to cassette and get the RCAs to send to the boombox amp and other circuits.

Thanks, fellow cowbellists
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jv
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Re: Adding RCA inputs to a little boombox

Post by jv » Thu Feb 10, 2005 6:03 pm

I don't know about cutting wires, but you could get one of these things:
http://www.amazon.com/exec/obidos/tg/de ... lectronics

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Re: Adding RCA inputs to a little boombox

Post by Milkmansound » Thu Feb 10, 2005 6:23 pm

or a little FM modulator if there is no tape deck.

But you could probably just hack the leads off of the tape heads and attatch RCA cables to them. If you wanna trash that thing. I do not know if it will work... but its analog signal path - should do something interesting.
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Re: Adding RCA inputs to a little boombox

Post by psychicoctopus » Thu Feb 10, 2005 6:40 pm

The CD-to-cassette adapter is your best bet.

the rest of this post is total conjecture, somebody please jump in if I'm being misleading...

if you feel like getting your hands dirty, cut the wires to the tape playback head and solder on some input jacks. Since a tape head is a coil of wire (like half of a transformer), you will have a balanced input. Solder the two wires of each tape head to pins 2 and 3 of an XLR-F connector, and connect pin 1 to the ground of the boombox circuit. If it has a metal chassis, then that's probably grounded. If the chassis is plastic, you may have trouble finding ground. Any big metal surface associated with the PCB is probably grounded, though.

Since you'll be sending in -10 or +4 dB line level, you'll need to build a pad circuit to knock the level down before it hits the repro amplifier. I don't know what level the repro amp is expecting, but it's probably on the order of a microphone signal, so a 40 dB pad might be a place to start.

I could be wrong, but isn't there a special EQ-curve imposed on playback of cassette tape recordings? This would make your line input sound like ass, regardless of the other factors. If the purpose of this modification is to check mixes, then it may be a waste of time.

Word of caution: if your boombox is AC-powered, and you aren't familiar with what a power supply looks like, then DON'T DO THIS! You could be shocked badly.
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Re: Adding RCA inputs to a little boombox

Post by Randy » Thu Feb 10, 2005 7:06 pm

psychicoctopus wrote:I could be wrong, but isn't there a special EQ-curve imposed on playback of cassette tape recordings? This would make your line input sound like ass, regardless of the other factors. If the purpose of this modification is to check mixes, then it may be a waste of time.
My guess is that this method would be a waste of time. The signal from the heads is like the signal from a guitar pickup, except it has to go through a bias tone and EQ circuit to be translated into something that can be amplified with any sort of fidelity. I would guess that a line level will be the wrong impedance and a lot more current than what the heads are looking for.

The cassette with input thing looks like a safe bet.

Otherwise, if you're feeling lucky and don't care if you blow the thing up or electrocute yourself, you could take a guess at where the amplifier section of the circuit is and patch in there. I'd buy the cassette adapter.
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Re: Adding RCA inputs to a little boombox

Post by Electro-Voice 664 » Thu Feb 10, 2005 9:11 pm

Thanks for the help. I'll dig around and look for a tape adapter.

I just wanna be able to check my mixes with the hyped bass through the plastic box.
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Re: Adding RCA inputs to a little boombox

Post by joel hamilton » Thu Feb 10, 2005 9:24 pm

I have a little sony thing that we wired up directly to a pair of TT patch points on one of our patchbays. I use it all the time. There is a picture of it on the studio G site below. We wired the thinig straight to the traces coming from the out of the radio section, and i drilled holes in the back of the case to get the cables out and to the console patch bay. Woks amazingly well. I leave the bass boost on, and the EQ totally lame like it would be anywhere, and the volume cranked up quite a bit. I can patch out of the studio send and listen to the boombox just like another monitor choice. I love that thing.
Convinces people that the mix doesnt live in my V88's or my NS10's, it actually does have tons of low end that works anywhere. They are glad to hear it on the box! We always hear people say "that is coming out of just the little boom box???" and they put their head right up to the V88's to see if I am kidding... Awesome.

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Re: Adding RCA inputs to a little boombox

Post by Electro-Voice 664 » Thu Feb 10, 2005 9:29 pm

Joel, anyone, do you know what to look for, as in what the radio traces look like?
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Re: Adding RCA inputs to a little boombox

Post by joel hamilton » Thu Feb 10, 2005 9:42 pm

They are silver, usually on a green background.. ;)

Depends on your box! In ours, the radio section of the electronics was actually a shitty little card that was connected to a main motherboard thingy via a little ribbon cable lookin jammy. Couldnt have been simpler. We could have even used the other side of the ribbon cable if we wanted, but the plug was scary, so we didnt. Have you poked around in the thing? I ripped out the broken tape transport and glued the doors shut (tried to) and then used tape over the doors. The more ghetto the thing looks the better. Clients trust you more. I swear this is true. Kick its ass a litle while you are working on it. People will believe you are a wizard more because you are making this "broke ass old boom box" sound like a million bucks!

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Re: Adding RCA inputs to a little boombox

Post by Mark Alan Miller » Thu Feb 10, 2005 9:46 pm

I've got a favorite pair of old Sharp boombox speakers (from my highschool days - 80's vintage) hooked up to a 2-watt Radio Shack mini integrated amp.
This is connected to my console's Monitorr B out. (Monitor A goes to a power amp, then to a very high-quality speaker switcher, then to 3 different pairs of bigger monitors...)
he took a duck in the face at two and hundred fifty knots.

http://www.radio-valkyrie.com/ao/aoindex.htm - download the new record (free is an option!) or get it on CD.

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