Internal Speaker

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Centurion
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Re: Internal Speaker

Postby Centurion » Thu Nov 12, 2020 6:16 am

thefunkygibbon wrote:
Tue Nov 10, 2020 11:11 am
so am i understanding then that there is no way to get an 'unamplified' speaker of any sorts in the case that will be much better than the Piezo one?
I won't speak for the whole community, but from the tests I've documented that I tried, that was the case for me. I have no idea how anyone could think the un-amplified output would be suitable. Maybe it's ok for the board-only backers who use caseless setups. I just don't know and no one has chimed in with a magic speaker-only install suggestion. Mitchelln, had the idea of using the mini amplifier board and that lead me to trying a different type of amplifier, which is working well enough for me at the moment.

I'm still waiting for the smaller surface mount amp from China. Once I receive that, I plan to hook it up and see if the output is as strong as the one I currently have installed. If so, I hope to figure out a good clean way to install it as easily as possible and will document that here for anyone interested.
ZX Spectrum Next Backer №1,104 / ZX Spectrum Harlequin Rev. G owner / USA ZX Spectrum enthusiast

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Centurion
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Re: Internal Speaker

Postby Centurion » Fri Nov 20, 2020 2:39 am

Success! I have finally finished the Internal Speaker mini amplifier mod to my Next. The output was the same as the larger board version after I dialed in the potentiometer and I was able to come up with a nice, simple install. I have documented the step-by-step process on my blog for anyone who might be interested in doing this or something similar with their Next's.
LM386_Next.jpg
LM386_Next.jpg (745.76 KiB) Viewed 2539 times
I hope it's helpful. I am finished opening up my Next and don't plan on opening it again at this point!

Here's the link: http://www.drunknretro.com/2020/11/zx-s ... r-mod.html

Cheers!
ZX Spectrum Next Backer №1,104 / ZX Spectrum Harlequin Rev. G owner / USA ZX Spectrum enthusiast

thefunkygibbon
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Re: Internal Speaker

Postby thefunkygibbon » Wed Dec 16, 2020 10:26 am

cool. got any links to the bits you bought to do this?

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Centurion
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Re: Internal Speaker

Postby Centurion » Sat Dec 19, 2020 7:27 pm

thefunkygibbon wrote:
Wed Dec 16, 2020 10:26 am
cool. got any links to the bits you bought to do this?
I live in the US, so you'll probably want to source your bits based on your location. It's really just headers, wire, speaker and the LM386 board.

I included the model number for the speaker I used in the article link above and for the LM386 amplifier, eBay search "DC 5V-12V LM386 electret microphone power amplifier board gain 200 times mic amp" and you should be able to find the same board I ordered from China.

Hope that helps
ZX Spectrum Next Backer №1,104 / ZX Spectrum Harlequin Rev. G owner / USA ZX Spectrum enthusiast

thefunkygibbon
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Re: Internal Speaker

Postby thefunkygibbon » Wed Jan 06, 2021 11:59 am

great stuff. I'll investigate and buy :-) thanks for all the info

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Centurion
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Re: Internal Speaker

Postby Centurion » Fri Jan 29, 2021 11:30 pm

thefunkygibbon wrote:
Wed Jan 06, 2021 11:59 am
great stuff. I'll investigate and buy :-) thanks for all the info
No problem. If you modify it at all, I'd be curious to see what you come up with. Working great for me so far.
ZX Spectrum Next Backer №1,104 / ZX Spectrum Harlequin Rev. G owner / USA ZX Spectrum enthusiast

Zxspooks
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Re: Internal Speaker

Postby Zxspooks » Sat Sep 11, 2021 11:05 am

Hi, found these speakers online anyone know if it would be ok for the next internal?

https://www.mutant-caterpillar.co.uk/sh ... 8o2r9vjol1

Alcoholics Anonymous
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Re: Internal Speaker

Postby Alcoholics Anonymous » Mon Sep 13, 2021 4:11 am

Zxspooks wrote:
Sat Sep 11, 2021 11:05 am
Hi, found these speakers online anyone know if it would be ok for the next internal?
https://www.mutant-caterpillar.co.uk/sh ... 8o2r9vjol1
They will be ok to use but they will also be very quiet. The recommended speaker impedance is 30 ohms whereas this one is 40 ohms.

The audio out of the internal speaker circuit of the Next is actually very quiet and will need a DIY amplifier circuit to adjust to acceptable volume, a lot of which this thread is about. I think beep level may turn out to be ok because at the moment, it is still not as loud as it could be, as the audio out of the internal speaker is meant to be everything -- beep, ay, dac, pi. There is a beep-only mode for the internal speaker and for that we may try to swing the output of the beeper to extremes instead of a wide swing less than that as it is now.

An amplifier circuit should be simpler than what we have seen here so far where parts used are inexpensive amplifier modules. The KS2 machines will get an expanded J3X connector (on KS1 it is called J3) which will make it easier to build a good amplifier.

In any case, an amplifier with adjustable volume should be able to hide the difference between 40 ohm and 30 ohm speaker. I do think that some of the amplifier circuits in this thread may be using speakers less than 30 ohms which may be giving higher volumes yet.

Zxspooks
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Re: Internal Speaker

Postby Zxspooks » Mon Sep 13, 2021 7:04 pm

Thank you for your reply.


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