Help needed connecting to Telefunken Magnetophon 96 - UK Vintage Radio Repair and Restoration Discussion Forum

biterbit · 2nd May 2018, 5:48 pm

Hi. I've recently been handed a Telefunken Magnetophon 96 reel-to-reel tape recorder and a number of tapes that were recorded on it. The good news is that all the machine's functions seem to work fine and I've played a sample tape which is remarkably clear and clean given it was made over 50 years ago.

I want to backup some of the tapes contents to computer files and have got a DIN to phono lead which will feed into my computer's audio card.

There are five sockets on the side of the machine (see photo): Micro (5-pin DIN microphone input), Phono/Radio (5-pin DIN for line inputs I guess), Synchro (5-pin DIN, not clear what its for); a 5-pin DIN marked with a small loudspeaker symbol (which, based on my translation of a German manual I found online, seems to be intended to connect headphones), and a 2/3-pin DIN marked with a larger loudspeaker and 5 Ohm symbol (I guess for attaching an external speaker).

I've connected my DIN-phono lead to the headphone socket but I've found there is a loud buzzing noise coming through the audio output which almost entirely masks the audio recording itself. I've also explored the sockets by poking a connector into each socket hole separately: but the only audio output I've found is via pin 3 on the headphone socket, along with the noise.

The noise is not just mains hum as I can hear that at a low level through the sockets when the machine is plugged into the mains; the much louder buzzing starts only when the machine is switched on (with or without the tape playing).

I looked through the sticky thread on tape transfer and saw the warning about some machines having a current on the outputs. I tested the sockets with a multimeter and could only find a current (about 6V DC) on one of the pins of the microphone socket.

I'm now at a bit of a loss as to what to do now. The recordings sound great through the machine's own loudspeaker (albeit with some spool motor noise in the background) but I'd rather take a direct line output to record from if possible.

Does anyone have any suggestion as to what is going on here: is this some quirky output format that I can fix with a different lead configuration, or does it indicate a fault with the machine's electronics that might mean recording from the speaker?

Many thanks for any help you can offer.

TonyDuell · 2nd May 2018, 6:52 pm

My guess is that the Radio/Phono socket is line level inputs _and_ outputs. See if you can find the signal on pins 3 and 5 of that socket.

'Syncho' may be for a slide projector or cine film synchroniser. I doubt it's of any use here.

ben · 4th May 2018, 9:23 am

I would agree with Tony re: Radio/Phono socket.

I have one of these machines somewhere and I vaguely recall hooking it up that way.

biterbit · 4th May 2018, 4:49 pm

Thanks for the suggestions. I did find an output signal on the Radio/Phono socket but it has the same background noise as elsewhere. As far as I can tell I can't attach an audio file to the post to illustrate the effect, but I found that the noise is present on the screening of the socket as well as on some (but not all) of the individual output pins across the different sockets. Unfortunately the output pins without the noise seem to have no signal.

ben · 4th May 2018, 8:20 pm

Might have to use the loudspeaker output with a resistor of a few ohms in series.

jamesperrett · 4th May 2018, 11:37 pm

I'm wondering if this is a ground loop. I don't know what sort of audio card you have but, if it is a basic card with no balanced inputs, you may need to try an isolation transformer in line with the audio output.

biterbit · 6th May 2018, 11:26 am

I'm using an E-MU 0404 PCI card which has 2 line level, unbalanced analog inputs. I'm intrigued by the audio isolation transformer idea. Looking online I see commercial units at about £100 and small components on eBay for a couple of pounds. I don't understand the electrical properties I'm looking for but a few pounds investment would be reasonable to see if it fixes the problem - but £100 is far too much.

Is a low-cost DIY approach to test out the effect feasible or do I need to be investing large sums even to find out?

AndiiT · 6th May 2018, 12:17 pm

Hi, is the screen connected to pin 2 of your audio lead intact? If not you will experience hum issues, additionally do you know if the cable on your connecting lead is of the screened type - it should be but there have been occasions when unscreened cable is used on some leads.

You may have to experiment a bit with some series resistors to reduce the level of signal going in to the PC's sound card.
It's unusual to find any hiss/hum (due to a fault) on the line level sockets that can't be heard when playing back through the machines internal speaker.

Using an audio isolating transformer is a bit "overkill" IMO and as you have already seen can be expensive.

Ben's suggestion of using the speaker output via a series resistor/attenuation network should suffice although the signal fed in to the PC's sound card would be dependent on the settings of the machine's volume and tone controls as well as any software based level adjustments on the PC.

Regards

Andrew

biterbit · 6th May 2018, 1:44 pm

Thanks for the suggestions. I'll do some more testing to eliminate possible problems with the leads. It does seem odd that the audio is fine through the internal speaker but no good elsewhere.

Maarten · 6th May 2018, 11:12 pm

Try using a laptop operating from the battery (not connected to mains or anything else) and see whether this affects teh noise.

jamesperrett · 6th May 2018, 11:42 pm

Quote:

Originally Posted by biterbit

Is a low-cost DIY approach to test out the effect feasible or do I need to be investing large sums even to find out?

A cheap one will certainly tell you if a transformer will solve the problem - and may well be good enough for the task in hand. Ground loops are very common with computer audio which is why balanced inputs and outputs are now so prevalent on many audio interfaces.

The ART DTI box is often recommended as a ready made solution for ground loop problems but is probably too sophisticated for this application.

https://www.soundonsound.com/reviews/art-dti

julie_m · 7th May 2018, 8:00 am

Most laptops don't have line-in connections anymore.

biterbit · 8th May 2018, 5:14 pm

Thanks for all the great suggestions. I experimented today with routing the line outputs to the microphone socket of a laptop. The same noise was apparent until the moment I took the laptop off mains power - then it disappeared. So the 'ground loop' suggestion was spot on. Running on battery power the laptop was able to pick up a very clear and clean signal with just a faint AC hum in the background which I can filter out without affecting the recording.

My plan is now to use a battery-powered laptop to offload the tapes I have to audio files as everything else on the machine seems to be working fine.

Thanks for your help everyone.

2nd May 2018, 5:48 pm	#1
biterbit Diode Join Date: Apr 2018 Location: St Albans, Hertfordshire, UK. Posts: 5	Help needed connecting to Telefunken Magnetophon 96 Hi. I've recently been handed a Telefunken Magnetophon 96 reel-to-reel tape recorder and a number of tapes that were recorded on it. The good news is that all the machine's functions seem to work fine and I've played a sample tape which is remarkably clear and clean given it was made over 50 years ago. I want to backup some of the tapes contents to computer files and have got a DIN to phono lead which will feed into my computer's audio card. There are five sockets on the side of the machine (see photo): Micro (5-pin DIN microphone input), Phono/Radio (5-pin DIN for line inputs I guess), Synchro (5-pin DIN, not clear what its for); a 5-pin DIN marked with a small loudspeaker symbol (which, based on my translation of a German manual I found online, seems to be intended to connect headphones), and a 2/3-pin DIN marked with a larger loudspeaker and 5 Ohm symbol (I guess for attaching an external speaker). I've connected my DIN-phono lead to the headphone socket but I've found there is a loud buzzing noise coming through the audio output which almost entirely masks the audio recording itself. I've also explored the sockets by poking a connector into each socket hole separately: but the only audio output I've found is via pin 3 on the headphone socket, along with the noise. The noise is not just mains hum as I can hear that at a low level through the sockets when the machine is plugged into the mains; the much louder buzzing starts only when the machine is switched on (with or without the tape playing). I looked through the sticky thread on tape transfer and saw the warning about some machines having a current on the outputs. I tested the sockets with a multimeter and could only find a current (about 6V DC) on one of the pins of the microphone socket. I'm now at a bit of a loss as to what to do now. The recordings sound great through the machine's own loudspeaker (albeit with some spool motor noise in the background) but I'd rather take a direct line output to record from if possible. Does anyone have any suggestion as to what is going on here: is this some quirky output format that I can fix with a different lead configuration, or does it indicate a fault with the machine's electronics that might mean recording from the speaker? Many thanks for any help you can offer. Attached Thumbnails

2nd May 2018, 6:52 pm	#2
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Help needed connecting to Telefunken Magnetophon 96 My guess is that the Radio/Phono socket is line level inputs _and_ outputs. See if you can find the signal on pins 3 and 5 of that socket. 'Syncho' may be for a slide projector or cine film synchroniser. I doubt it's of any use here.

4th May 2018, 9:23 am	#3
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Help needed connecting to Telefunken Magnetophon 96 I would agree with Tony re: Radio/Phono socket. I have one of these machines somewhere and I vaguely recall hooking it up that way. __________________ Regards, Ben.

4th May 2018, 4:49 pm	#4
biterbit Diode Join Date: Apr 2018 Location: St Albans, Hertfordshire, UK. Posts: 5	Re: Help needed connecting to Telefunken Magnetophon 96 Thanks for the suggestions. I did find an output signal on the Radio/Phono socket but it has the same background noise as elsewhere. As far as I can tell I can't attach an audio file to the post to illustrate the effect, but I found that the noise is present on the screening of the socket as well as on some (but not all) of the individual output pins across the different sockets. Unfortunately the output pins without the noise seem to have no signal.

4th May 2018, 8:20 pm	#5
ben Dekatron Join Date: Aug 2006 Location: Madrid, Spain / Wirral, UK Posts: 7,498	Re: Help needed connecting to Telefunken Magnetophon 96 Might have to use the loudspeaker output with a resistor of a few ohms in series. __________________ Regards, Ben.

4th May 2018, 11:37 pm	#6
jamesperrett Octode Join Date: May 2007 Location: Liss, Hampshire, UK. Posts: 1,873	Re: Help needed connecting to Telefunken Magnetophon 96 I'm wondering if this is a ground loop. I don't know what sort of audio card you have but, if it is a basic card with no balanced inputs, you may need to try an isolation transformer in line with the audio output.

6th May 2018, 11:26 am	#7
biterbit Diode Join Date: Apr 2018 Location: St Albans, Hertfordshire, UK. Posts: 5	Re: Help needed connecting to Telefunken Magnetophon 96 I'm using an E-MU 0404 PCI card which has 2 line level, unbalanced analog inputs. I'm intrigued by the audio isolation transformer idea. Looking online I see commercial units at about £100 and small components on eBay for a couple of pounds. I don't understand the electrical properties I'm looking for but a few pounds investment would be reasonable to see if it fixes the problem - but £100 is far too much. Is a low-cost DIY approach to test out the effect feasible or do I need to be investing large sums even to find out?

6th May 2018, 12:17 pm	#8
AndiiT Octode Join Date: Aug 2005 Location: Saltburn-East, Cleveland, UK. Posts: 1,786	Re: Help needed connecting to Telefunken Magnetophon 96 Hi, is the screen connected to pin 2 of your audio lead intact? If not you will experience hum issues, additionally do you know if the cable on your connecting lead is of the screened type - it should be but there have been occasions when unscreened cable is used on some leads. You may have to experiment a bit with some series resistors to reduce the level of signal going in to the PC's sound card. It's unusual to find any hiss/hum (due to a fault) on the line level sockets that can't be heard when playing back through the machines internal speaker. Using an audio isolating transformer is a bit "overkill" IMO and as you have already seen can be expensive. Ben's suggestion of using the speaker output via a series resistor/attenuation network should suffice although the signal fed in to the PC's sound card would be dependent on the settings of the machine's volume and tone controls as well as any software based level adjustments on the PC. Regards Andrew

6th May 2018, 1:44 pm	#9
biterbit Diode Join Date: Apr 2018 Location: St Albans, Hertfordshire, UK. Posts: 5	Re: Help needed connecting to Telefunken Magnetophon 96 Thanks for the suggestions. I'll do some more testing to eliminate possible problems with the leads. It does seem odd that the audio is fine through the internal speaker but no good elsewhere.

6th May 2018, 11:12 pm	#10
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,199	Re: Help needed connecting to Telefunken Magnetophon 96 Try using a laptop operating from the battery (not connected to mains or anything else) and see whether this affects teh noise.

7th May 2018, 8:00 am	#12
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Help needed connecting to Telefunken Magnetophon 96 Most laptops don't have line-in connections anymore. __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

8th May 2018, 5:14 pm	#13
biterbit Diode Join Date: Apr 2018 Location: St Albans, Hertfordshire, UK. Posts: 5	Re: Help needed connecting to Telefunken Magnetophon 96 Thanks for all the great suggestions. I experimented today with routing the line outputs to the microphone socket of a laptop. The same noise was apparent until the moment I took the laptop off mains power - then it disappeared. So the 'ground loop' suggestion was spot on. Running on battery power the laptop was able to pick up a very clear and clean signal with just a faint AC hum in the background which I can filter out without affecting the recording. My plan is now to use a battery-powered laptop to offload the tapes I have to audio files as everything else on the machine seems to be working fine. Thanks for your help everyone.