Source of 200ohm speakers?
Source of 200ohm speakers?
Does anyone know of a source for the 200ohm speakers like those used in the Issue 1 and 2 Spectrums? The newer (Issue 3 and later) 40ohm speakers are easy to find as new versions, but seemingly less so for the 200ohm.
I'm Chris, a Brit in Germany (Chr$ on the QL forum). https:\\QXL.WIN < QL related collection.
Re: Source of 200ohm speakers?
200 ohm sounds more like a piezo than a speaker, googling "200 ohm piezo" throws up quite a few answers.
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Re: Source of 200ohm speakers?
I would suggest upgrading the circuit to the issue 6A board standard, then you can use a 40Ω speaker.
Mark
Mark
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ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: Source of 200ohm speakers?
It certainly looks like a speaker in that it has a coil/magnet and membrane. It's just one that I'm fixing up to sell, so an entirely new circuit is probably overkill, and perhaps a non-beeping Spectrum might actually appeal to people that like to shoot-things-up in the dead of the night or whatever (you can't actually turn the speaker off normally of course).
Electronically, is it viable/what would happen if I used a 40ohm speaker with a resistor added to bring it up to about 200 ohm resistance?
Electronically, is it viable/what would happen if I used a 40ohm speaker with a resistor added to bring it up to about 200 ohm resistance?
I'm Chris, a Brit in Germany (Chr$ on the QL forum). https:\\QXL.WIN < QL related collection.
Re: Source of 200ohm speakers?
Hi,
In case of 40ohm speaker, the resistor will pull up the ZTX450 main currant and will destroy it by overheated.
You had to make a serial pod made with five 40ohm speakers…
Or add a 150 ohm resistor.
Wiring diagram:
In case of 40ohm speaker, the resistor will pull up the ZTX450 main currant and will destroy it by overheated.
You had to make a serial pod made with five 40ohm speakers…
Or add a 150 ohm resistor.
Wiring diagram:
Xavier ...on the Facebook groupe : "Zx81 France"(fr)
- 1024MAK
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Re: Source of 200ohm speakers?
The reason that Sinclair changed the circuit (which occurred from the issue 3 board, but the schematic is wrong) is because the sound output was too low (too quiet).
If you use a less sensitive speaker, such as a 40Ω one, and then wire a resistor in series with it, you will only end up making it even less loud! In fact with a 160Ω resistor, more power will be wasted in the resistor than used in the speaker!
Changing to the later circuit just involves removing diode D10 and replacing it with a transistor and some patch wires.
Mark
If you use a less sensitive speaker, such as a 40Ω one, and then wire a resistor in series with it, you will only end up making it even less loud! In fact with a 160Ω resistor, more power will be wasted in the resistor than used in the speaker!
Changing to the later circuit just involves removing diode D10 and replacing it with a transistor and some patch wires.
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: Source of 200ohm speakers?
Oh yes, so it does! I only need to pinch the 9v from somewhere. I'll give that a go then.
I'm Chris, a Brit in Germany (Chr$ on the QL forum). https:\\QXL.WIN < QL related collection.
- 1024MAK
- Posts: 5153
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: Source of 200ohm speakers?
Xav, the issue two circuit does not use a transistor: And the speaker is a higher resistance type.
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: Source of 200ohm speakers?
So we cannot have a DOLBY 5.0 standard on the Spectrum.
it's really sad...
Xavier ...on the Facebook groupe : "Zx81 France"(fr)
Re: Source of 200ohm speakers?
Sorted. Half neatly done - but it doesn't matter as it's hidden by the heat sink. I stole a TR7 from a parts only Issue 6 board.
Thanks Mark and Xav for your comments.
Thanks Mark and Xav for your comments.
I'm Chris, a Brit in Germany (Chr$ on the QL forum). https:\\QXL.WIN < QL related collection.