amplifying this circuit to normal audio amplifier levels? - Page 1
Forum section: electronics / beginners

author: dentaku
author_rank: Frequent Contributor
timestamp: June 02, 2014, 09:19:06 pm
content: What would be the least parts heavy way to amplify the output of this circuit to a reasonable level that you could plug into an audio amplifierlike around 2 Vpp?

author: kaindub
author_rank: Regular Contributor
timestamp: June 03, 2014, 02:12:31 am
content: Low power - fet amp (fet, capacitor, 2 resistors)Op amp - non inverting (op amp, 2 resistors, capacitor. Additional 2 resistors and a capacitor if you only have a single sided supply)Robert

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 03, 2014, 02:52:24 am
content: What is the source of that waveform? If it is being generated/synthesized, why is it such a low level?What kind of power do you have already available? (i.e. what is powering the source of that waveform)?What exactly is the destination? What is the destination impedance?Does it REALLY need 2V peak-to-peak? Ordinary "consumer line-level" is 0.7V.What are the requirements for quality/fidelity (distortion, etc.)? Is this just a "noisemaker"? (i.e. siren, etc.)What is the waveform? Sine? Saw? Triangle?. Clearly, the envelope is triangle, but we can't see the waveform in your illustration.

author: dentaku
author_rank: Frequent Contributor
timestamp: June 03, 2014, 03:44:42 pm
content: Quote from: Richard Crowley on June 03, 2014, 02:52:24 amThe source of the waveform? It's just the output of that circuit. I changed the values of some of the components from the circuit W2AEW built in this video about measuring unknown inductors.https://www.youtube.com/watch?feature=player_detailpage&v=74fz9iwZ_sM#t=454Quote from: Richard Crowley on June 03, 2014, 02:52:24 amI'm just planning to use two 9V batteries to power it.I'm not sure about the destination or impedance. I'm just hoping to plug it into something that will allow me to hear it like the mic input of my old computer.Quote from: Richard Crowley on June 03, 2014, 02:52:24 amThat's true. I'm fine with something around 1V. It's not terribly important as long as it doesn't clip and distort.Quote from: Richard Crowley on June 03, 2014, 02:52:24 amYup, it's pretty much just an experimental noise maker. Think of it as a voice from a drum machine or something. It's receives a pulse at it's input and puts out a DING sound.Quote from: Richard Crowley on June 03, 2014, 02:52:24 amIt's a sine like you can see in W2AEW's video. It's a ringing tank circuit.I'm attaching a .wav file of the output of the simulation.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 03, 2014, 04:33:52 pm
content: Quote from: dentaku on June 03, 2014, 03:44:42 pm"That circuit" shows a "black box" signal generator. That is not a complete circuit diagram.QuoteThat video is about radio frequencies. (2.x MHz) Several orders of magnitude too high for anybody (even bats or insects) to hear.You will never hear that signal no matter how much you amplify it. What frequency does YOUR circuit output?QuoteThen you're not doing it right. With a power source of 18V you should be able to easily generate a 2 volt signal directly.QuoteYou should be able to take the signal you have right now and feed it into the MICROPHONE input of your computer.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 03, 2014, 05:01:31 pm
content: Change C1 ~= C2 and adjust the calculation accordingly.Also, if you're just looking for zero crossings, use a comparator. No need for audio frequencies then.Note that the circuit shown merely goes "thud" if the capacitor or inductor have more than 0.5 ohms or so ESR or DCR (enter real numbers for these parameters and see how it simulates).Tim

author: dentaku
author_rank: Frequent Contributor
timestamp: June 03, 2014, 06:24:35 pm
content: Quote from: Richard Crowley on June 03, 2014, 04:33:52 pmI know that he was working in the MHz range. I'm just wondering if it's one of those things that you can simulate in software but iscompletely impossible in real lifewith the component values I chose at the frequencies I would like?As you can hear from the .wav attachment in my previous post, it's well within audio range.LTSpice tells me it's ringing at 2.32861KHz.Again, it's just an experiment. I've never used an inductor in anything and just liked the waveform I saw in the video and wondered if it would be possible to use it (modified for lower frequencies) to make interesting sounds.The "black box" is just putting out a 2Hz square wave that goes from 0V to 4.5V. On every rising edge it triggers a "bing" sound.

author: dentaku
author_rank: Frequent Contributor
timestamp: June 03, 2014, 07:03:24 pm
content: Quote from: T3sl4co1l on June 03, 2014, 05:01:31 pmYeah you're right. I just simulated it with both capacitors at 100uF and the levels are well within useable audio levels.I just choserealcomponents from the list in LTSpice instead of just generic C and L and using real capacitors models still works but when I change the inductor to a real named model with included Peak Current, Series Resistance and Parallel Resistance numbers I just get little tick sounds instead of a ding.What I'm guessing from reading your answer is that in real life this won't work?The image I'm attaching shows the simulation using an inductor with realistic values and the one of the right uses the generic unknown un-named 47uF inductor model.One goes tick and the other goes ding.

author: dentaku
author_rank: Frequent Contributor
timestamp: June 03, 2014, 07:04:13 pm
content: Quote from: dentaku on June 03, 2014, 06:24:35 pm

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 03, 2014, 07:23:10 pm
content: Oops, I wrote "audio frequency" when I meant to say "audio level"...Anyway, yet more good reasons why these things are done with op-amps. (BTW, also check out the peak current through the source. Got a power amplifier that can do that?)So you're looking at synth sounds, like bells? Plenty of circuits out there -- give 'em a look!Tim

author: dentaku
author_rank: Frequent Contributor
timestamp: June 03, 2014, 10:11:07 pm
content: Quote from: T3sl4co1l on June 03, 2014, 07:23:10 pmI was just curious if it was practical in real life.If I plot current of the PULSE source at 4.5V I get these spikes that go from +/-200AIs that what you mean by "peak current through the source"?At 0.1V it spikes to around 4.5A.Any time I see stuff that oscillates I always wonder if it could be used somehow to make sounds... like any synth geek would.