Recording from DAB - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

mhennessy · 23rd Mar 2021, 11:10 am

I agree it would be nice if we could find some service data for the Stella machine - I've only had a very quick look, so something might well exist. Looking at the schematics of the Philips EL3549 you mention, the only difference between radio and phono inputs is sensitivity - there doesn't appear to be any EQ for the phono input (as it's expecting a ceramic cartridge, of course).

I'm ignoring impedance because it's irrelevant to this discussion, but basically TS1 appears to be configured with shunt feedback, so the its base is (nominally at least, as it depends on the position of R4) a virtual earth. Therefore input resistors (R1 and R2) are setting both the input impedance and relative gain. R1 is 18k, and that's the radio input, and R2 is 1M for the phono input. All makes sense, but as I say, not applicable here - the Pure won't care if it's driving 18k or 1M, or indeed 1k or infinity

So it's a question of audio level. The radio input is likely too sensitive at 3mV, although I assume this is with the record level set to max, and it will be able to handle signals that are considerably larger - but impossible to quantify from the schematics alone (it depends on the rails and the position of R4). The phono input is a much better bet, at 150mV sensitivity. The output level from the Pure isn't specified, sadly, but it's likely in the 500mV region, I'd guess.

I agree that the mic input is best ignored, as it's too sensitive. An attenuator could be built in advance of it, but I can't immediately seen any benefit compared to using the phono input.

But first, we need to find out how that 3.5mm to DIN lead is wired

paulsherwin · 23rd Mar 2021, 11:18 am

At a guess, the adapter is wired to connect a 5 pin DIN wired for output to a 3.5mm jack. The OP is using this the 'wrong way round' which is going to produce some very strange effects, as the signal somehow makes its way through the internal circuitry of the recorder.

reeltoreelrob · 24th Mar 2021, 6:40 pm

Hi ,
Thanks for all of the replies and suggestions, it has given me something to think about, I think I will start with the lead maybe the adapter is not wired for what I am using for.
I have attached a pic of the lead setup I am using.
Thanks again
Rob.

jamesperrett · 25th Mar 2021, 12:32 am

If that's a 5 pin DIN lead then it might be worth buying one with 4 phono plugs on it so that you can potentially use all the pins on the DIN connector. I'd just touch the ends of the phono plugs to see which ones gave the biggest buzz (or biggest deflection on the level indicator) to find which pins are input pins.

If that's a 3 pin DIN lead then you should only connect one of the phono plugs.

simpsons · 25th Mar 2021, 10:47 am

Mhennessy and Paulsherwin are on the right track and James an option but I wonder if we should go back a step.

1. When using the Grundig Yacht Boy to play the DAB radio does the Yacht Boy volume control work?

2. When playing through the Tape Recorder, does its volume control work?

Out of interest, the photo you show illustrates a phono lead to DIN "Socket" from which the 5 pin DIN lead is plugged into. If so and 2 above is no to both I think then the phono lead adapter is wired for audio out. You may have in the kit one which is wired otherwise. Only you can tell.

Fun and games eh?

Chris

reeltoreelrob · 26th Mar 2021, 8:08 pm

Hi all,
Another big thank you for your comments ideas and help, the long and short of it was that it was the adapter plug not wired for what I am using it for. I have made another lead and it works a treat, I think it does need a resistor in line though as suggested on here.
Thanks again.
Rob.

mhennessy · 26th Mar 2021, 8:12 pm

Glad you got it working, but it would be really useful if you could tell us know how the faulty combination was wired.

Apart from solving the mystery for those us us who put a lot of time and thought into this for you, it will really help others in the future when they run into something similar

reeltoreelrob · 27th Mar 2021, 8:40 pm

Hi all,
It was a school boy error really, I had an 5 pin din to 5 pin din lead, the adapters were to convert the lead to phono to phono lead. I cut one of the din plugs off, did a buzz test as suggested and then soldered onto 3.5mm and joined the 2 tips so I get both channels into mono.
Thanks again for the help

23rd Mar 2021, 11:10 am	#21
mhennessy Dekatron Join Date: Jul 2007 Location: Evesham, Worcestershire, UK. Posts: 4,244	Re: Recording from DAB I agree it would be nice if we could find some service data for the Stella machine - I've only had a very quick look, so something might well exist. Looking at the schematics of the Philips EL3549 you mention, the only difference between radio and phono inputs is sensitivity - there doesn't appear to be any EQ for the phono input (as it's expecting a ceramic cartridge, of course). I'm ignoring impedance because it's irrelevant to this discussion, but basically TS1 appears to be configured with shunt feedback, so the its base is (nominally at least, as it depends on the position of R4) a virtual earth. Therefore input resistors (R1 and R2) are setting both the input impedance and relative gain. R1 is 18k, and that's the radio input, and R2 is 1M for the phono input. All makes sense, but as I say, not applicable here - the Pure won't care if it's driving 18k or 1M, or indeed 1k or infinity So it's a question of audio level. The radio input is likely too sensitive at 3mV, although I assume this is with the record level set to max, and it will be able to handle signals that are considerably larger - but impossible to quantify from the schematics alone (it depends on the rails and the position of R4). The phono input is a much better bet, at 150mV sensitivity. The output level from the Pure isn't specified, sadly, but it's likely in the 500mV region, I'd guess. I agree that the mic input is best ignored, as it's too sensitive. An attenuator could be built in advance of it, but I can't immediately seen any benefit compared to using the phono input. But first, we need to find out how that 3.5mm to DIN lead is wired

23rd Mar 2021, 11:18 am	#22
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,966	Re: Recording from DAB At a guess, the adapter is wired to connect a 5 pin DIN wired for output to a 3.5mm jack. The OP is using this the 'wrong way round' which is going to produce some very strange effects, as the signal somehow makes its way through the internal circuitry of the recorder.

24th Mar 2021, 6:40 pm	#23
reeltoreelrob Pentode Join Date: Nov 2010 Location: Birmingham, West Midlands, UK. Posts: 202	Re: Recording from DAB Hi , Thanks for all of the replies and suggestions, it has given me something to think about, I think I will start with the lead maybe the adapter is not wired for what I am using for. I have attached a pic of the lead setup I am using. Thanks again Rob. Attached Thumbnails

25th Mar 2021, 12:32 am	#24
jamesperrett Octode Join Date: May 2007 Location: Liss, Hampshire, UK. Posts: 1,875	Re: Recording from DAB If that's a 5 pin DIN lead then it might be worth buying one with 4 phono plugs on it so that you can potentially use all the pins on the DIN connector. I'd just touch the ends of the phono plugs to see which ones gave the biggest buzz (or biggest deflection on the level indicator) to find which pins are input pins. If that's a 3 pin DIN lead then you should only connect one of the phono plugs.

25th Mar 2021, 10:47 am	#25
simpsons Octode Join Date: Feb 2007 Location: Harrow, London, UK. Posts: 1,493	Re: Recording from DAB Mhennessy and Paulsherwin are on the right track and James an option but I wonder if we should go back a step. 1. When using the Grundig Yacht Boy to play the DAB radio does the Yacht Boy volume control work? 2. When playing through the Tape Recorder, does its volume control work? Out of interest, the photo you show illustrates a phono lead to DIN "Socket" from which the 5 pin DIN lead is plugged into. If so and 2 above is no to both I think then the phono lead adapter is wired for audio out. You may have in the kit one which is wired otherwise. Only you can tell. Fun and games eh? Chris

26th Mar 2021, 8:08 pm	#26
reeltoreelrob Pentode Join Date: Nov 2010 Location: Birmingham, West Midlands, UK. Posts: 202	Re: Recording from DAB Hi all, Another big thank you for your comments ideas and help, the long and short of it was that it was the adapter plug not wired for what I am using it for. I have made another lead and it works a treat, I think it does need a resistor in line though as suggested on here. Thanks again. Rob.

26th Mar 2021, 8:12 pm	#27
mhennessy Dekatron Join Date: Jul 2007 Location: Evesham, Worcestershire, UK. Posts: 4,244	Re: Recording from DAB Glad you got it working, but it would be really useful if you could tell us know how the faulty combination was wired. Apart from solving the mystery for those us us who put a lot of time and thought into this for you, it will really help others in the future when they run into something similar

27th Mar 2021, 8:40 pm	#28
reeltoreelrob Pentode Join Date: Nov 2010 Location: Birmingham, West Midlands, UK. Posts: 202	Re: Recording from DAB Hi all, It was a school boy error really, I had an 5 pin din to 5 pin din lead, the adapters were to convert the lead to phono to phono lead. I cut one of the din plugs off, did a buzz test as suggested and then soldered onto 3.5mm and joined the 2 tips so I get both channels into mono. Thanks again for the help