HowTo Wire Radio Speakers to Audio-In on TV-VCR Combo

Okay searching the web I just learned the speaker wires transmit power and not a 1:1 audio signal as I ignorantly presumed. Forum discussions say I must use an amplifier inline i.e. AM radio speaker wires --> amplifier --> TV-VCR Audio In.

I don't really understand how power can become audio when amplified but if that's all that it is I know I am using an older table top AM-FM radio which will need to have an amplifier to record the radio's audio using the TV-VCR.

So what might be your recommendation for the least expensive amplifier? I'll be calling Radio Shack to learn what may be learned. Thanks for your time...

The speaker wires carry an audio signal (an AC voltage) to a low impedance speaker (probably about 8 Ohms). The speaker impedance (similar to, but more complex than resistance) presents a load on the voltage, producing a current flow in the speaker wires. The product of the voltage and current is power.

Your forum discussion group is, in my experience, wrong on this one

You should discard this idea. Further study, if wanted, will explain the conditions much better.

No external amplifier is needed.

Your recorder's audio input has a very high impedance, which means the signal audio voltage will drive it easily.

If your AM radio uses an audio output transformer, find the connections from it to the speaker, and see if both wires go directly to the speaker. If they don't then one of them is probably connected to the systems "common" somewhere. Connect it to the shell of your male RCA jack. If one is not connected to common, connect it to the shell of your male RCA jack.

Connect one end of a low power, 100,000 Ohm resistor (radio shack?) to the other speaker wire. Connect the other end of the resistor to the center pin of the RCA jack.

Turn the radio volume down low, and plug the RCA jack into the audio input of your recorder. While recording, turn the radio volume up to a usable level.

Doesn't your radio have a headphone jack? I would try an adapter to rca then low volume on the radio. Since the line input level is 1 volt P-P you should be able to adjust the volume low enough to get a decent recording with a little trial and error recording.

I forgot to confirm the white speaker wire comes off the board and goes directly to one of two speakers wired together (in series?).

//Speakers

This is an older table top AM-FM radio in a nice wood cabinet and has no headphone jack. Given instruction I would have no problem rewiring the existing speakers to a headphone jack if that is plausible or I could use a cheap contemporary radio with a headphone jack. If neccessary I could rationalize spending twenty bucks at Target for a cheap radio. All I want to do is record the late night radio program to tape for playback the next day and hope for a decent result that is "listenable."

Rewiring speakers to a headphone jack does not sound consistent with Don's earleir comments however. I'd like to hear Don weigh in again as his earlier response certainly implies an expertise which may direct me to the optimal solution. I do know how to solder well. I just don't know jack about the theory and application of electronics.

I can't tell if the transformer shown is a power transformer or an audio output transformer. If you can't trace the wire by eye, or check it with an Ohmmeter....... Hmmm!

Do you have a Volt/Ohmmeter? If yes, then first measure for voltage (AC and DC) between the outer shell of the audio input jack, and each of the radio speaker wires. If there is no voltage, then measure for resistance between the same points. If there is no voltage and no continuity (n low resistance) then it doesn't matter which wire goes where.

Otherwise..... Do you have a soldering iron?

Have soldering iron and good at soldering but no meters. What does the large obstructive metal shield wrapped around the transformer imply? Load the SpeakerWire.jpg and ObliqueView.jpg links above. Any inference regarding the determination of transformer type which may be deduced? Your comments regarding my reply to a headphone hack as suggested by Meat Plow? Doesn't sound plausible or consistent with what I've learned from your earlier comments. Jees, this topic deserves to be blogged for posterity!

Ok. Won't need soldering iron then.

That there is a honking big get-hot transistor mounted on it, needing to shed it's heat to the surroundings.

No, I can't see enough detail to be sure. If you can't see if the speaker wires are connected to it (or that the AC power is wired to it via the power switch), let's ignore it.

Actually, if you could put in a jack that opens the path to the speakers when a plug is inserted, that would be ok and you might like it because the speakers would be off while you are recording. Or just add a jack in parallel with the speakers, but the speakers will be on while you record.

A jack is optional hardware. However, see below.

Since we have no schematic, no meter, and don't know how the amplifier output interfaces the speakers, and don't know whether the radio or recorder is AC/DC, there is a safety hazard in going further with the simple plan.

Instead, go to radio shack and buy their el-cheapo 8 Ohms to 1000 Ohms audio transformer. Connect the 8 Ohm connections to the speaker wires (with or without a jack), and connect the 1000 Ohm transformer wires to the RCA plug for connection to the recorder. That is not only safe, but the quality of the sound may be a bit better.

Before you blow your power transistor on that classic radio I would go to Walmart and buy this nice radio that does what you need for under $50.

or spend twenty dollars and do it like below with what you have and $20 of add-on stuff.

Use a microphone mounted on front of the radio speaker plugged into this amplifier below.

Then use the cord with plugs below on the amplifiers earphone jack output into the line input rca input of the VCR.

I like George and his radio mannerism, over lunch I would ask him, do you buy all this creative thinking?

Good Luck,

• * * Christopher

Temecula CA.USA

I'll try to get to Radio Shack tommorrow but I'm trying the mic through amp tonight suggested by christopher.

I happen to have a little teeny amp which is a 9V knock-off of a Fender Mini Twin guitar amp. Wierd though, tried to power the amp with a 9V transformer I found that powers cheap computer speakers The 9V transformer gets frying pan hot and the amp just hums. Can't get no sound through the mic.

Then used 9V battery for testing and I get sound from the radio through the mic but I'm still not getting the sound from the amp to record on the VCR using Line 1. I know the amp is passing the sound through as I can get in with headphones.

Can use the TV-VCR combo to record a movie for example on Ch 3 just fine to the VCR so I know the TV-VCR recorder works and I playback sound and picture.

The 1/8" to RCA cable used to patch amp to TV-VCR was found around the house and came from Radio Shack and is in like new condition. Tried both Audio In on TV interfaces but still no joy. Could it be something as stupid as uisng Line 2 instead of Line 1 on TV-VCR? Don't know until tomorrow... What does Line 1 and Line 2 imply anyway?

I got the mic and the amp all worked out and use headphones to confirm the amp is picking up the audio from the mic for output. Can't get the damn TV-VCR to record despite the correct 1/8" to RCA cord to Audio Input on the TV-VCR. Tried both quick record mode and timed record mode neither want to record the Audio In when TV-VCR is set to Line 1 or Line 2. Out of options for now but appreciate the great idea...

My own advise leaves me one possible conclusion. I think the VCR needs a input signal of around 3v p-p and the amplifier audio out is down around < 1 volt to drive a speaker or earphone. Any thing recorded on the VCR would me very quiet.

If my workbench was not so cluttered with my disassembled Theremin project I would set up and test a couple of ideas. My theremin audio can output 3 volts p-p.

• * * Christopher

Temecula CA.USA

They say at least some VCRs won't record audio unless there is a video signal.

I have no direct experience with this, and have no idea how wide spread it is, but this seems more likely a culprit than anything else.

Michael

Just a thought - Are you sure a VCR will record audio without the presence of video?

Duh. As it turns out I called the company supporting BrokSonic TV-VCR combo later this morning and they told me recording would in fact be mute without a video channel. So this project has crashed and burned for the moment and I have to try to cobble together other equipment. Thanks so much for your time and efforts...

Well, its true for the BrokSonic...

As it turns out I called the company supporting BrokSonic TV-VCR combo later this morning and they told me recording would in fact be mute without a video signal. So this project has crashed and burned for the moment and I have to try to cobble together other equipment. Thanks so much for your time and efforts...

Michael Black wrote:

Actually, the problem that I found was **playback**. Without any video, the AGC of the TV set muted the audio. When I hit the VCR's Menu button to throw some text onto the screen, I could then hear the audio. With my black & white TV, I didn't need to do this.

If you had 2 VCRs (or *something* that can put out video on an RCA jack), you could plug that into the Video input that pairs with the audio input you are using. My VCRs actually have 2 sets of external inputs (L1 & L2; channels 001 & 002).