Can a diode amplify sound? - Page 1
Forum section: electronics / projects

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: December 11, 2019, 01:46:25 pm
content: can I use a diode to amplify sound? like by driving the cathode?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 11, 2019, 01:50:39 pm
content: Any unspecified diode type? Sure, a tunnel diode can.Tim

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 11, 2019, 02:26:50 pm
content: Wait, 6Х2П (6H2P) or 6Н2П (6N2P)?A diode is not an amplifier. At best, heater power might be varied to control plate current, but this is far too slow to be useful at audio frequencies (and if the plate voltage and current ratings are too low relative to heater power, it might not end up having any power gain at all).6K2P ~= EF93 ~= 6BA6, is that right? I mean, it can be used, but the remote cutoff grid won't do any favors for distortion. RF tubes do tend to be microphonic, YMMV.Tim

author: mcovington
author_rank: Regular Contributor
timestamp: December 11, 2019, 03:29:44 pm
content: Diode tubes do not amplify. I am not sure how you envision using it as an amplifier.I seem to recall that some semiconductor diodes have been used in a roundabout way as (poor) amplifiers by taking advantage of nonlinearity in their characteristics, typically at frequencies too high for other amplifiers available at the time. (Someone mentioned tunnel diodes.) Tubes don't work that way.

author: Yansi
author_rank: Super Contributor
timestamp: December 11, 2019, 06:15:56 pm
content: You troll or what?Where did you even get that idea?

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: December 11, 2019, 06:59:17 pm
content: Quote from: ELS122 on December 11, 2019, 06:14:03 pmIf you explain in detail how that is supposed to work I would be very happy.

author: SiliconWizard
author_rank: Super Contributor
timestamp: December 11, 2019, 07:02:19 pm
content: Quote from: T3sl4co1l on December 11, 2019, 01:50:39 pmYes. A Gunn diode as well.For other types of diodes, I don't see how.

author: Yansi
author_rank: Super Contributor
timestamp: December 11, 2019, 07:07:38 pm
content: Every component with a bit of negative resistance on its VI curve can be used to amplify signal, if I am not mistaken. Tunnel and Gunn diodes are two of them.

author: Gyro
author_rank: Super Contributor
timestamp: December 11, 2019, 07:43:50 pm
content: ... but in terms of the thread title of amplifying sound, or at least an audio signal. Not a hope.

author: emece67
author_rank: Frequent Contributor
timestamp: December 11, 2019, 09:01:04 pm
content: .

author: bson
author_rank: Unknown
timestamp: December 11, 2019, 11:15:02 pm
content: For most diodes, only in the sense that a detector is an amplifier...

author: mcovington
author_rank: Regular Contributor
timestamp: December 12, 2019, 01:30:07 am
content: Why would you expect that circuit to amplify? It looks like what you would get if you misread the schematic of an amplifier for a filament triode tube and simply put the cathode in place of a grid.

author: Berni
author_rank: Super Contributor
timestamp: December 12, 2019, 05:47:23 am
content: The problem with your amplifier is that any current pulled down from the output also flows back into the input. Since a diode is a 2 terminal device there is nowhere else that it can go.Your grid and cathode are basically the same terminal in your diode (heater is not a terminal because the cathode is solid and not a grid). What gives the triode tube its amplification abilities is that the grid and emitter are two separate terminals. When current flows trough a triode it mostly flows between the cathode and plate, very little current makes it to the grid where the input is connected. Its the cathode that is intruding the extra current into the circuit in order to provide more current into the output and amplify power. If your cathode and grid are the same terminal then all the current must come from the input and hence all the power comes from there.

author: ejeffrey
author_rank: Super Contributor
timestamp: December 12, 2019, 06:30:43 am
content: Quote from: ELS122 on December 12, 2019, 05:21:19 amPositively charged relative to what? This sounds like confusion about "absolute" voltage which doesn't mean anything. All that matters is the voltage difference between the cathode and anode. The cathode is always emitting electrons. If the anode is more positive than the cathode it will attract those thermally emitted electrons, if not it won't. i.e., it will rectify the signal. However, it won't add any extra energy. If you try to bias the anode as you do in a triode, it will then just capture all of the cathode current regardless of small variations in the cathode voltage.

author: strawberry
author_rank: Super Contributor
timestamp: December 12, 2019, 08:57:04 am
content: does he mean diode as triode with direct heated cathode and cathode plate as a grid?

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: December 12, 2019, 11:32:40 am
content: Quote from: strawberry on December 12, 2019, 08:57:04 amcould be, but that would be a pretty awfull triode i assume, since... well... how should the cathode tube that encapsules the heater regulate the flow of electrons, if those pesky little beasts don't even get out of the cathode tube?despite the cathode material emitting the most electrons being on the outside of the cathode tube...so we would have a "grid" that is emitting electrons. "grid" current would definitely flow - which won't be a huge problem since the cathode used as the grid will be much tougher than a thin grid, but that thing wouldn't be controllable in a normal way at all.And we would have a grid made of solid sheet metal. no electrons from the "cathode" (=heater) could pass to the anode, besides from the few that go outside the cathode tube where the heater enters.but those wouldn't be very regulated from the potential of the cathode at all I assume, but a little bit of influencing coule be possible.But - I am intrigued now and would love to try this idea at home. maybe this weekend...

author: Gyro
author_rank: Super Contributor
timestamp: December 12, 2019, 10:22:24 pm
content: Quote from: ELS122 on December 12, 2019, 09:31:35 pmThe diode has no gain so cannot theoretically amplify anything.

author: Yansi
author_rank: Super Contributor
timestamp: December 12, 2019, 10:24:31 pm
content: Here you are, a parametric audio amplifier using varactors... and some other interesting stuff. This is what I]d call a diode amplifier.Courtesy of DL3PB,http://pa1b-qrp.blogspot.com/2012/02/parasaki.html?m=1

author: daqq
author_rank: Super Contributor
timestamp: December 13, 2019, 10:46:14 am
content: In short: No.In long: It might be able to hack together some awful solution with a uselessly small gain.

author: iMo
author_rank: Super Contributor
timestamp: December 13, 2019, 10:56:49 am
content: Quote from: Yansi on December 12, 2019, 10:24:31 pmTD718 is a tunnel diode, afaik..You may use a traveling wave tube as well then

author: Gyro
author_rank: Super Contributor
timestamp: December 13, 2019, 11:39:17 am
content: Yes, TD718 is a Tunnel diode (in addition to the varactors and the demodulator diode).It does seem to be cheating just a little bit to use a Tunnel diode oscillator as an RF exciter for the Varactor diode bridge though. A single transistor stage is going to win in all respects in this case.Cute circuit though!P.S. can you count a TWT as a diode?

author: Yansi
author_rank: Super Contributor
timestamp: December 13, 2019, 11:42:00 am
content: Quote from: imo on December 13, 2019, 10:56:49 amyou know, the tunnel diode is not used for amplification there. It is a pumping wave oscillator for the parametric amplifier.