The first tape recorder Tonschreiber 1939

[reel-to-reel-man]

Originally Posted by paulsherwin

I know you may think this is heresy, but if you digitize the recording you can easily manipulate the speed. I would expect the quality to be best if you play back at slower than the correct speed then speed it up.

Amazing machine.

Paul

Very true, in fact that was the idea, though I am experimenting with different machines to get different results, my Telefunken M-5 is very similar in design, it also has a full track head, I plugged it in and tried to play a tape, silence followed with smoke

The Telefunken had been powered up about 5 months ago, and had been used regularly, just goes to show the temperamental of early electronics.

[James B]

If you digitally record the tapes at a high sample rate like 96k, you could then match them to the correct speed digitally by listening for any mains hum on the tapes. If you generate a 50Hz tone or a multiple of it, and varispeed the recording until the recording and tone tune up, you should have it at the correct speed. Then just resample it at best quality to 44.1k.

[reel-to-reel-man]

That’s very true though the recorder would have only had a response up to 5KHz, above that really is white noise, the EMI RD4/4 has a top response of 18KHz with the heads on it now, so that will be adequate to get the best out of the recording what was done, as for the mains hum, there isn’t any, the recorder was designed to run on 25Hz to 60Hz which makes me think the input frequency was not important and was cleaned off the tapes pretty quickly if there recorder could record that low in the first place. I have taken the video clip sound and resample it using a band stop amplifier, the results are very muffled but once I have gone though all the tapes, if I find anything interesting I will post it, so far its experimental speeches testing the recorder at various speeds and some music.

[reel-to-reel-man]

Oops! had an accident whilst spooling the tape off, I got a little ahead of myself thinking that I had fixed the tape and was at the time winding it back a little too quickly, the tape broke. No tape was lost thankfully, though it did make a mess.
http://www.vintagerecorders.co.uk/seb/radio/ton/32.jpg

[reel-to-reel-man]

Need some help on this machine, I am looking for info on the rotary head on the left hand side of this machine, all I know is that it can be motor driven, its connected to the Tonhöhe (Tone Control) and it has 4 heads. I am suspecting it may have something to do with this machine being the first of its kind with AC bias, is it possible that this head created the AC?

[mickjjo]

I don't know if you have found this site but it looks useful:-

http://www.xs4all.nl/~aobauer/tonschreiber_b.htm

There is a description of the rotating heads on page 2 of this 22 page pdf manual:-

http://www.xs4all.nl/~aobauer/Tonschreiber%20b.pdf

It seems when playing back recordings of high speed morse the tape could be slowed down and the rotating heads were used to increase the pitch of the sound , clever stuff!

Regards, Mick.

[reel-to-reel-man]

You are a star! I have been looking for the diagram, and its at the bottom of that PDF! I owe you one!

What an interesting idea, to change the pitch of the tape without changing the speed, effectively stretching the time rather than the pitch, and I thought that was a recent toy.

Thank you ever so much for your help.

[Michael Maurice]

I'm a little perplexed!

I undserstood that AC biasing was discovered when a German officer was recording something off the radio, (probrably a Hitler speech) the recorder beinbg close to a transmitter and the record head picking up the higher frequency transmissions which acted as a bias.

If you look at the diagram on Page 22, you will see some semiconductor diodes in a bridge arrangement. I didn't think they had such diodes before 1950. They cant all be metal rectifiers.

The other thing is that the circuit notes (the typed notes not the handwriting) are in english. If this was a pre war or even during the war German millitary machine, it is highly unlikely that the diagrams would have been printed in English.

[reel-to-reel-man]

Well the English part I know about, during the war, these recorders where captured, some went to England and some went to America, on one of the tapes I got (Which are either in English or blank) there is speech telling how to set up the recorder. These recorders where stripped down and analysed, the documents you see may well have been classified information by the Americans or British for many years (I did find these exact papers for sale in America as military declassified information). So the recorder is German, you may notice in the pictures on the first page, all of the English is stuck on labels, the papers you see are basically what the British and Americans found out. The British development went into EMI and brought out the EBI BTR-1, the Americans developed the Ampex 100.

The diode you have me on, I have found early reference to the diode back in 1926 (1904 for the valve one), have a look on page 14 (7B), I have never seen a diode like that before, if you look at the picture below, the red things are the diodes, massive!


http://www.vintagerecorders.co.uk/seb/radio/ton/20.jpg


Some snippets off the internet

-----

1939 and Walter Weber’s rediscovery and application of high-frequency AC biasing, which had been known since the 1920s, giving the 1941 Magnetophons a bandwidth of 10 kHz.


-----

What I do not follow is who invented AC biasing (If the idea was around in the 1029’s), and does this recorder have it? I see these is an oscillator in there but it seems to drive the capstan motor,


I have read else where that the AC bias came in by 1941 but only on the radio models, the military ones didn’t have it,

[James B]

Ah yes! Re the rotating heads, I remember from resent research that the BBC Radiophonic Workshop used a system with that head design for pitch-shifting!

[reel-to-reel-man]

your not going to believe this, its almost impossible to find these machines for sale, but I have been lucky to find a second one! And I brought it !!!!

I have not got a picture of the amp yet, the recorder is not as in nice condition as the other and was over half the price, fortunately it came with more tapes in tins!


http://www.vintagerecorders.co.uk/seb/radio/ton/33.jpg

[ben]

sounds like these decks couldn't have fallen into better hands! Glad to see that history is being preserved. good luck with them!

[Welsh Anorak]

Hi
Re the diodes - was the symbol we know today used in wartime? I imagine the circuit diagram is later than the machine and probably made from examining a captured one in detail - that would explain the Engish notes and abbreviations - wouldn't K be capacitor in German?
The whole circuit looks very advanced for its time, especially the use of solid-state (i.e. metal) rectifiers and the unusual valves.
Good luck!
Glyn

[Hermit6345]

Hi Glyn,

My edition of "Wireless Its Principles and Practice" by R W Hutchinson re-printed in 1941 certainly uses the current symbol for a diode. Guess this is off topic now though.

Ian

[reel-to-reel-man]

To Welsh Anorak'

I have a friend who collects old radio gear, he has had some of the pictures of me for this machine for his web page, it can be seen here

http://home.online.no/~perchri/kwea.htm

I do not know if the gentleman will know more about the diodes but I have asked him, he defiantly sounded very knowledgeable.


The diagram as mentioned before its believed to be what the British redrew in their efforts to understand the machine, I have not come across any German ones yet, though the whole machine is in German.

To Hermit6345,

The diagram is thought to be from 1944 as far as I can work out, all the tapes from this recorder had been wiped in 1944 as well for British tests, these recorders range from 1939 to 1944 in their build of this model though this one is thought to be an early one due to the serial number being so low (484)

[reel-to-reel-man]

Originally Posted by ben

sounds like these decks couldn't have fallen into better hands! Glad to see that history is being preserved. good luck with them!

Cheers Ben! I hope to get both these machines up and running though the second one will take a lot of work.

[DOFFERY]

AC bias goes back to 1921 re. Carpenter & Carlson US patent 1640881 & was finally developed by H.J.Von Braunmuhl & H. Weber German patent 743411 in 1940. Poulson had much earlier recognised the use of pre magnetisation to the medium but it was confined to DC applied to the earlier steel & wire mediums. Weber was the main architect of AC bias which put the Germans well ahead of the Allies during the second world war. Hence all we devoted fans of reel to reel have a great deal to thank Carlson & later Weber for the pleasure it has & still affords us. Why the Carlson patent was never implemented remains a mystery.

Doffery

[reel-to-reel-man]

My friend refers to the Diodes as "copper oxid-dull dioder" used in the wehrmacht equipment dated 1939 and on to 1948, then the semiconductors range came out, looks as if the diode existed much earlier than we thought but not as we know it.

On the AC bias, mentioned earlier that it was discovered in 1920 then rediscovered about 1940, this recorder though does not have AC biasing by the looks of it and it seems the first recorders to use the AC Biasing was the AEG Magnetophon K2 from 1941.

This is interesting stuff!

[mikloscs]

Hi,
Those red things or thing look like selenium diode or rectifier to me.
Miklos

[batterymaker1]

Originally Posted by reel-to-reel-man

your not going to believe this, its almost impossible to find these machines for sale, but I have been lucky to find a second one! And I brought it !!!!

Better buy a lottery ticket--you may be on a roll of good luck!

Beautiful instrument, btw. I like the arrangement of the capacitors and resistors on the phenolic boards. Looks fairly easy to service.