But there was AC. The music! Even if AC is derived from DC, it's still AC. And were there no output transformers?
I could be wrong, but the tweeter has a capacitor in series with it and an inductor in parallel with it. And the woofer has an inductor in series with it and a capacitor in parallel with it. And the woofer has rising impedance with frequency, so...
You'd have to verify this with someone who knows more than me. I've never used this configuration but I've seen it plenty of times.
I remember those radios. They typically had a "vibrator" which produced a rapid make and break pattern that was fed to a step up transformer. And the tube output circuits most definitely had a transformer.
It's 6dB/octave when the series crossover consists of just one capacitor and one inductor. rayma's link is very illustrative.
Exactly, but jimmyjoe, make sure you google the correct 'vibrator'!
The Vibrator Power Supply - Part One
Learning all the time!
Here's some interesting information on how to troubleshoot a vibrator: Vibrator Power Supplies
Here's some interesting information on how to troubleshoot a vibrator: Vibrator Power Supplies
Some places subscribe to the electron flow theory. I view current flow from the ground upThe one closest to ground potential.
Can't it follow along with the music, which doesn't rightly have a DC component, and where one was present through recording and reproduction it was filtered out.
Yes, I googled the correct "vibrator". But the radios I'm talking about had no vibrator (my Dad called them "buzzers). They were direct input 12VDC, and had no out put transformers. Here's a link to the only site that I could come up with that makes any sense; it lists tubes for old car radios. There's a blurb at the top, but I don't really understand all of it. Maybe you can get more out of it than I can.
12 Volt Car Radio Tubes jj
12 Volt Car Radio Tubes jj
" .... Can't it follow along with the music, ...."
Well, evidently it can. See Audio Output
But I still don't understand what causes the current reversal. In the primary power plant, there are magnets in a rotating field. The current has no choice but to reverse. Perhaps you don't subscribe to electron theory, but I do. It's the way I was taught all my life.
I can understand current reversal in a balanced push-pull amplifier, but what causes current reversal in a Class A single-ended amplifier?
I guess what I'm asking (another stupid question!) is .... where is the mechanism creating the crossing axis? (I hope that's an acceptable way to say it.)
Damn. I was gonna get out, and now I got myself in deeper than ever. jj
Well, evidently it can. See Audio Output
But I still don't understand what causes the current reversal. In the primary power plant, there are magnets in a rotating field. The current has no choice but to reverse. Perhaps you don't subscribe to electron theory, but I do. It's the way I was taught all my life.
I can understand current reversal in a balanced push-pull amplifier, but what causes current reversal in a Class A single-ended amplifier?
I guess what I'm asking (another stupid question!) is .... where is the mechanism creating the crossing axis? (I hope that's an acceptable way to say it.)
Damn. I was gonna get out, and now I got myself in deeper than ever. jj
I don't think the way we view current flowing should become tangled into a discussion of AC. Flux is about change.
The common (ground) terminal in a conventional single ended capacitor coupled stage acts as 0VAC. Consideration of its relative Voltage becomes irrelevant as the DC component is blocked by the capacitor.
The common (ground) terminal in a conventional single ended capacitor coupled stage acts as 0VAC. Consideration of its relative Voltage becomes irrelevant as the DC component is blocked by the capacitor.
The blurb clearly states that special tubes were eventually produced that could work off 12V DC directly, unlike ordinary tubes which required the higher anode voltage supplied by a vibrator.
If you look at the attachment, the voltage at the collector of the transistor (equivalent to the anode of a valve) varies in amplitude between 0V and +24V with a 'crossing point' of +12V.
The output transformer blocks the DC components of this voltage and passes only its sinusoidal variation, i.e. the amplified AC signal, on to the loudspeaker.
Attachments
I'm learning so much that if I don't watch out, pretty soon I'll actually know something!
And your explanation is, as always, both clear and greatly appreciated. jj
I know about the 12 volt tubes. They came later. But they still had an output transformer. In fact the early transistorized amplifiers had output transformers.
I used to take all this stuff apart as a kid. I've looked inside some of those tube car radios. I've seen the 12 volt tubes. I've also seen the vibrators and hooked them up. They are sure loud for use in an audio product.
I built a quick and dirty amplifier from a Craig "Powerplay" 8 track. It did have a pretty powerful power amplifier section. It was a push/pull output with input and output transformers, and 2N3055 outputs. I gutted everything but the output stage, put a feedback loop around the whole thing, and added RCA jacks. It had low voltage gain and low input impedance, so it was more of a power booster. If you drove it with a typical aftermarket car radio of the era (very low power OTL) it provided a lot more power. And in college I ran it off 18 volts and drove it from the output of a Panasonic all in one (turntable, 8 track, and radio) unit. It really improved the performance of that unit, which only had a couple watts output and a very grainy "transistor" sound. It was quite euphonic, which kind of masked the awful sound of early transistorized circuits (especially the early "chip amps" which were a special type of terrible).
I have another question, but this one is not so theoretical. Have a chance to buy a cabin, but the cabin is completely off-grid. I can take kerosene lanterns for light, but you can't run a stereo off kerosene. I can take 12V batteries up with me, but I don't know ANYTHING about 12v stereo, not auto sound and not any other 12V systems either. Where should I be looking? What should I be looking for? All I need is something to drive some cheap speakers while I relax. Would prefer not to use a gas-driven generator because of the noise. Thanks. jj
The essential thing (unless you are going to set up a solar charging station) is to preserve battery life by drawing as little current as possible from your battery.
To that end, I would go for a low power 12V amp. There are lots of kits and modules out there e.g. Velleman 2 x 5W Amplifier for MP3 Players Minikit MK190
It's surprising how loud just one watt can be when using high sensitivity speakers!
How sensitive (dB/W/m) are the speakers you intend to use?
To that end, I would go for a low power 12V amp. There are lots of kits and modules out there e.g. Velleman 2 x 5W Amplifier for MP3 Players Minikit MK190
It's surprising how loud just one watt can be when using high sensitivity speakers!
How sensitive (dB/W/m) are the speakers you intend to use?
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