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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment.

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Old 8th Nov 2021, 10:11 am   #1
Test Desk
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Default Dansette Apollo to Bluetooth.

Hello knowledgeable people. I have a single valve Dansette which was an eBay purchase. I can't say the model as the label has worn off. It was sold as restored and works fine. I would like to modify it to connect to a BT speaker but it doesn't have a headphone jack.
Any suggestions please?

Dave
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Old 8th Nov 2021, 10:41 am   #2
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Smile Re: Autochanger to Bluetooth

Hi,
The valve will, most likely, be a UL84. So don't expect hi-fi sound or loudness.
The chassis will be connected to one side of the mains, so be very aware of that.
Bluetooth will be handy as there won't be any physical connection to the source.
I think the power supply unit must be contained within the cabinet to maintain isolation from the outside world.
Cheers, Pete.
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Old 8th Nov 2021, 11:23 am   #3
Edward Huggins
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Default Re: Autochanger to Bluetooth

Most Dansettes used a mains-isolated chassis. We really need a photo of yours so as to advise you further. If you can't Post a photo, is the single valve in yours marked as a EL84 or UL84 or UL41?
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Old 9th Nov 2021, 10:16 am   #4
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Default Re: Autochanger to Bluetooth

Here it is. I'll open up and check the valve if necessary. I mainly bought it to play my 7" singles and to smell the inside ( takes me right back! )!
Obviously the sound isn't great, but what I expected, hence the Bluetooth question.
Thanks
Dave
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Old 9th Nov 2021, 2:21 pm   #5
Edward Huggins
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Default Re: Autochanger to Bluetooth

Well now that we can see it, this is a Dansette "Apollo" from 1969 - and there are certainly no valves in this! Why ever did you say there were?
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Old 10th Nov 2021, 9:08 am   #6
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Default Re: Autochanger to Bluetooth

Quote:
Originally Posted by Test Desk View Post
Here it is. I'll open up and check the valve if necessary. I mainly bought it to play my 7" singles and to smell the inside ( takes me right back! )!
Obviously the sound isn't great, but what I expected, hence the Bluetooth question.
Thanks
Dave
looks in great condition and a nice late 60s clean design
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Old 10th Nov 2021, 3:35 pm   #7
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Default Re: Autochanger to Bluetooth

Looks fantastic, a nice purchase. I've never built a BT transmitter but I've put plenty of BT receivers in sets. As a general principle, if you buy a BT transmitter module you can power this from the set transformer (if there is one) or off the mains switch directly using a small encapsulated 240v to 9v transformer. The BT transmitter should be ok with a headphone level signal - a crystal cartridge should be fine, a ceramic you should get away with if your Bluetooth speaker has decent gain.
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Old 10th Nov 2021, 10:04 pm   #8
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Default Re: Autochanger to Bluetooth

Thanks, I'm pleased with it's condition too. And, much to my surprise, Edward is correct. The amp is transistor! I can only say the bloke who sold it to me said it was a valve amp and he was such a nice guy, I'm inclined to think he made a genuine mistake. As he was fairly local, I collected from his house. I was amazed at his music collection which covered a whole wall, and even more amazed by his players. He had everything from manual decks, tape players, CD players, a music centre and (ta dah!) a juke box!!! and a very understanding wife too.
So I have a nice solid state record player with no headphones socket, so how do I connect a Bluetooth transmitter? I imagine a fitted headphones socket is derived from the pre-amp stage after equalization, so I suppose I needed circuit diagram and some guidance. Is it doable by a retired Telecoms engineer?
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Old 10th Nov 2021, 10:41 pm   #9
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Default Re: Autochanger to Bluetooth

It's doable with a bit of research and experimentation. Try one of those transmitter/receivers from eBay (no affiliation with seller, just a module I use) which are rechargeable and see how you get on. Once you do that you can decide whether to stick with an external BT transmitter or whether you want to power the BT module from the record player itself.

https://www.ebay.co.uk/itm/2-in-1-US...-127635-2958-0

The obvious first place to start would be the output from the cartridge itself.
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Old 11th Nov 2021, 9:03 am   #10
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Default Re: Autochanger to Bluetooth

If the cartridge is ceramic it expects to see a high impedance load (1-2Meg). A modern BT transmitter input is likely to be much lower, 20k seems typical, so frequency response is likely to be affected. It would probably be better to take a feed from the amplifier, but without a circuit I can't advise.
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Old 11th Nov 2021, 10:03 am   #11
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Default Re: Autochanger to Bluetooth

I've searched for a circuit, but from memory this was a very basic single chip design used by Rank Bush Murphy (RBM) in many other units at the time. This was the DRP10 model and badged as a "Dansette".
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Old 11th Nov 2021, 4:34 pm   #12
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Default Re: Autochanger to Bluetooth

Paul/Edward

In the absence of a circuit, would something like this work as a broadly universal solution? Input impedance is matched to cartridge and gain/input sensitivity can be adjusted easily. The transistor circuit is "borrowed" from another thread (credit to David) - I know very little about transistors so there may some tweaking to do, and it's all very theoretical, but I can't see any reason why it shouldn't work. Feel free to modify as appropriate.

Gabriel
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Old 11th Nov 2021, 5:04 pm   #13
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Default Re: Autochanger to Bluetooth

Thank you all for your input but does the suggested circuit circuit include RIAA equalization? I note you mention impedance matching but without equalization, the music is going to sound very thin isn't it?
I was considering buying a discrete Phono stage modified to match the BT impedance (which I would need help with!) but I'll have a crack at construction if that will work.
Dave
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Old 11th Nov 2021, 6:11 pm   #14
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Default Re: Autochanger to Bluetooth

ceramic or Crystal cartridges don't need EQ, so you wont need RIAA preamps.

The PSU shown is to me not what I'd build, for the miniscule extra cost use either an encapsulated bridge rectifier or 4 diodes in a bridge for FW rectifiaction. This will give the transformer a much easier life, and also the reservoir capacitor from stress, and the benefit of lower ripple and thus hum, although after the Voltage reg its unlikely to be an issue.
As its transistorised, I'd be inclined to pinch the volts after the record players own psu and smoothing assuming the module isnt too heavy on current.
Now here's an idea, why not wire in a switch at the rear and use a potential divider across the output of the amplifier if there's no preamp to tap off?
Solid state and if this an IC amp it will be silicon, is usually quite ok with a higher resistance load than that designed for, and quite possibly will be fine left O/C so I'd be happy to use something ike a 10k in total resistive divider fed via a DC blocking capacitor off the speaker output. Using a switch to select the internal speaker or BT card inside.
It should work.
Before all that though, It's worth trying taking off the signal from the cartridge,it mightwork.
If you find you need a separate step up to match the BT device, then I'd not use the discrete transistor solution. I'd build a simple op amp, TL071 or NE5534 or any similar audio op amp available for peanuts. You can easily set its input resistance to suit the ceramic or crystal cartridge and also thegain is set by the feedback resistors so that can be fine tuned to suit. Use a bit of power from the dansettes own PSU, if you're worried about hum from a less than smooth supply then by all means insert a simple Voltage regulator in the supply. The Op amp will run on anything up to about 30V on a single rail.
Long post but I hope i overed a few options.
Andy.
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Old 11th Nov 2021, 6:14 pm   #15
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Default Re: Autochanger to Bluetooth

Just thought, a decentlypower rated 8 ohm (or whatever the nominal speaker impedance is) resistor instead of the players speeaker, and a coupling capacitor off the hot end of that fed via a potentiometer to the BTmodule could also work ok. Simples.

A.
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Old 11th Nov 2021, 6:48 pm   #16
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Default Re: Autochanger to Bluetooth

Just a small correction on my post. It's Paul's circuit, not David. I don't know where David came from

Original post here.
https://www.vintage-radio.net/forum/...d.php?t=121557

KR
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Old 13th Nov 2021, 8:04 am   #17
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Default Re: Autochanger to Bluetooth

So Dave, have you attempted anything yet?
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Old 13th Nov 2021, 10:53 am   #18
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Default Re: Autochanger to Bluetooth

No I haven't tried anything yet as I've been studying the options presented here, for which I am grateful and I promise there will be an update forthcoming.
I am one of those retired people who are so busy I wondered how I ever had managed to work a full time job, let alone have hobbies!
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Old 13th Nov 2021, 11:06 am   #19
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Default Re: Autochanger to Bluetooth

Quote:
Originally Posted by bikerhifinut View Post
Just thought, a decentlypower rated 8 ohm (or whatever the nominal speaker impedance is) resistor instead of the players speeaker, and a coupling capacitor off the hot end of that fed via a potentiometer to the BTmodule could also work ok. Simples.

A.
Hi. I was thinking along the lines of your solution before I consulted this community but had no idea how to achieve it. Could you suggest some values for the components please?

Dave
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Old 14th Nov 2021, 8:30 am   #20
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Default Re: Autochanger to Bluetooth

If Andy doesn't reply, I would try a 50w resistor instead of speaker. It will need to be either 4w or 8w depending on what the speaker impedance is.

Capacitor 1kv 10nf (0.01uf). Value not critical , anything up to 0.1uf will do

Potentiometer 100k linear
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