I teach highschool physics, and want to connect my smartphone (LG V20) to a Chladni plate (vibrating plate for studying interference patterns in sound in solids).

I have successfully done this by connecting a standard 3.5mm male-to-male lead to the phone, and crocodile clips on the other end, connected by 4mm leads to a vibration generator with the Chladni plate attached. This works, and I can play tones and even music through the Chladni plate, and see interference patterns start to form.

However the amplitude is far below what I need. I have a signal generator with amplifier which works well, and provides a peak output of around 6V; the speaker cable sending the same signal provides around 0.4V.

I therefore need a signal amplifier, ideally that inputs and outputs on 3.5mm or 4mm, and outputs with a variable setting up to around 20x. I know almost nothing about electronics, and the school doesn't have a tech lab, but I do have an old Marshall G10 Mk2 (10W guitar amplifier) . I would like some advice on how to cannibalize this speaker/amp to achieve my aims.

I did already connect these, attaining an appropriate voltage, but the quality was very poor - a lot of hissing and apparently poor connections. I'm unsure if this is to be expected, or a sign of a problem with the amplifier. The speaker in the Marshall is broken, but may be fixable.

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    \$\begingroup\$ Giving a specific price here probably triggered all of the close votes, but I think this question could reasonably be edited to ask about how to determine what specs are important and what type of product is needed. That is, assuming you do need help with those aspects and not just help finding a product and seller. \$\endgroup\$ – Justin May 21 at 17:55
  • \$\begingroup\$ I agree with @Justin! Also, since you're actually describing an audio amplifier: Get an audio amplifier! Chances are your school has one lying around, anyway, maybe in the shape of a CD player, cassette recorder, TV, just anything that has connectors for external speakers. \$\endgroup\$ – Marcus Müller May 21 at 17:59
  • \$\begingroup\$ Sparkfun or adafruit has some op amp devboards that could be used as amplifiiers \$\endgroup\$ – Voltage Spike May 21 at 18:26
  • \$\begingroup\$ More likely the plate’s coil resistance is much lower than a speaker, so you may need just a current amplifier or buffer. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 21 at 18:54
  • \$\begingroup\$ Thanks for the comments everybody. Sorry that I didn't read the rules fully enough to realise I was breaking one of them. I'm very inexpert in electronics, I can describe it well enough for GCSE Physics but not much more! I'll edit the question as recommended. Also, I've just been given an old guitar amp and speaker - when I get time I intend to cannibalise it, and may well be back here to ask more specific questions as to how. \$\endgroup\$ – cosmogoblin May 22 at 19:18

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