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Old 15th Oct 2019, 12:39 pm   #21
stitch1
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

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Originally Posted by Herald1360 View Post
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Originally Posted by cheerfulcharlie View Post
Just stick a single mains wall socket in there which has USB sockets.
You can then directly wire the socket to the mains switch and all your modern stuff will connect to the USBs.

https://www.screwfix.com/p/lap-1-gan...er-white/8812f

They are normally rated about 2 amps across the both which should more than enough to drive the Bluetooth
Deffo say "in there" and suggests wiring to the mains switch (on the pot....)

Specifies a single socket which would fit inside, too.
Seems to be a simple solution and there's a USB only option. What would be the drawback, size?

https://www.screwfix.com/p/lap-usb-c...e/151CC?tc=QT7

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Old 15th Oct 2019, 1:19 pm   #22
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

To go back to the start, I found that my pantry transmitter was becoming more and more unusable due to RF rubbish from SMPSs. Putting a class x capacitor inside a 13A plug and trying it in different sockets helped immensely and has made it possible to use it again. It didn't help for LW, though.

A bluetooth receiver would use the full potential frequency response of the amplifier so would sound a lot better than using a pantry transmitter, and be an interesting modification, but it might be worth trying to see whether a capacitor in a plug helps with the interference problem with other sets. Just be careful of the small charge held in cap if you unplug it!
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Old 15th Oct 2019, 1:55 pm   #23
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

What temperature do you get inside a DAC90?
You might want to check the temperature range that the Bluetooth device can stand.

I would just stick a zener at the bottom of the heater chain and then smooth the resulting asymetric squarewave that results, making sure it was powerful enough to stand the switch-on surge.
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Old 15th Oct 2019, 2:45 pm   #24
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

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What temperature do you get inside a DAC90?
You might want to check the temperature range that the Bluetooth device can stand.

I would just stick a zener at the bottom of the heater chain and then smooth the resulting asymetric squarewave that results, making sure it was powerful enough to stand the switch-on surge.
There is a problem with that approach, in that the "asymetric squarewave" actually reverses polarity at its lower point. In fact, it will try to discharge any smoothing capacitor placed across the zener.
Also the zener must be substantial enough to withstand the full heater current.
Your circuit would still require a series rectifying diode before the smoothing cap. to overcome the "square wave " problem i.e. to stop the cap. partially discharging back into the circuit during part of the cycle.

The point you make about the ambient temperature is very valid, and certainly should be a consideration in a DAC90a. Tony.
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Old 15th Oct 2019, 6:01 pm   #25
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

This was my suggestion. Might need some protection from failure of bulbs and bypass resistor (put the assembly in a bag to catch the contents?).

Pauls suggestion is much the same except a series resistor/capacitor is used as a capacitor dropper but that would also need protection as a change in load would result in over voltage.
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Old 15th Oct 2019, 6:13 pm   #26
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

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There is a problem with that approach, in that the "asymetric squarewave" actually reverses polarity at its lower point. In fact, it will try to discharge any smoothing capacitor placed across the zener.
Yes, but it doesn't matter much, it just adds to the ripple slightly. You do not need another diode - well so long as the capacitor can stand the worst case start-up situation of being unlucky with the first cycle - something to check. I think the reverse aspect will be somewhat compensated by the fact that it is a square wave.
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Old 15th Oct 2019, 6:20 pm   #27
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

There are lots of possible solutions. I think Nick is experienced enough to know he needs to experiment.

Keep it simple I say
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Old 15th Oct 2019, 6:40 pm   #28
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

Opps - yes you are right boxdoctor, you do need a diode.
My brain is working too slowly these days - the heater chain acts like a constant current feed so the voltages doesn't really matter.
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Old 16th Oct 2019, 9:57 am   #29
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

No problem GMB. . I am of an age where senior moments occur, and your comment had me wondering for a while whether I had got it wrong ! Tony.
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Old 16th Oct 2019, 10:50 am   #30
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Default Re: Don't shoot me... but ideas wanted about Bluetooth adaptation of DAC90A

I'd try a pantry transmitter anyway first - that way you can have 'live' radio [news/weather forecasts] FM/DAB/Net ... anything, streaming into all your sets .... not just the DAC90A .... and it leaves it 'totally original' too.

Mind you - one problem with the DAC 'occasional consolettes' is the directional nature of the internal aerial ...... not to mention energy consumption and associated heat!

The one big advantage of Nicks proposals is that of 'remote control' i.e. he can alter programme material and volume etc. without leaving his chair!
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