Soundmirror tape info

[ralph2472]

Hello everyone.

Could somebody please tell me if it's possible to play Soundmirror paper magnetic tapes from 1950 on a standard reel to reel tape recorder?
Also, could a Thermionics Products Soundmirror tape recorder play standard tapes?
I particularly don't want to cause any damage to the tapes.
Thanks for reading this, and for any replies I might get.

Regards

Ralph.

[barretter]

I have done this and it was interesting to watch the shower of oxide being shed whilst the music kept playing! I'm not sure using a Sound Mirror tape recorder would make any difference.

[Tractorfan]

Hi,
Before you start playing them, make sure you are copying them onto another device at the same time, just in case you lose too much oxide and you don't get a second chance!
Cheers, Pete

[TIMTAPE]

Paper tape is a bit like acetate tape. It doesnt stretch. It breaks or tears. You can always splice it together again if it does break.

I think those Sound mirror machines recorded the paper tapes on a centre track, leaving the top and bottom edges unrecorded. Since this never became a common standard, to retrieve all the program, you may need to use the two centre tracks of a 4 track/4 channel machine like a Teac 3440 or similar.
But if you do, you might find a fair bit of azimuth wander (high frequency cancellation) if the two tracks are summed. This is related to the paper tape base.

Paper tapes having a relatively rough finish do generate more than normal background noise. Not much can be done about it of course.

The few paper tapes I encountered didnt have too much of a problem with oxide shed. The main problems were the brittleness of the tape base, the azimuth wander and the high background noise.

Whatever you do, play the tapes on a good quality machine, well maintained and with a clean, demagnetised tape path.

A machine with old fashioned head pressure pads may be helpful in giving better tape to head contact, giving a sound with less audible dropouts.

If the recordings are one offs and valuable to you, and you are in any doubt, go to an expert in this field such as Ted Kendall.

Cheers Tim

[ralph2472]

Thanks to everyone for the very fast replies to my post.
This has been very helpful.
I will have to be very careful because I don't know the exact content of the tapes I have, and I deffinitely do not want to damage them.
I had thought of immediate copying if I do try them out.
If I do successfuly try them, I'll let you all know the results.
Thanks again for all your help.

Regards

Ralph.

[Ted Kendall]

I'd be a tad windy about playing an original paper tape on a Soundmirror these days - the head configuration is less of a worry than the fragility of the base material and the likely state of the transport. Best, perhaps, to find some contemporary low-coercivity tape such as EMI H50 or BASF LGS (the red-backed stuff), which should give tolerable results if demonstrating the machine is your aim. If retrieving the material is important, then I am blushingly forced to agree with Tim - either farm it out or lay in large supplies of modified kit, splicing tape and bad language.

[brenellic2000]

Tim and Ted are both right... heed their advice.

The Soundmirror was a 'centre-track' machine. The tapes play surprisingly well on a standard 1/2 track - but they do need a pressure pad to maintain good head contact as the paper cups badly through absorbing moisture over the years.

Towards the end of production (1953) Thermionic Products talked of a 1/2 track option (it was by then available on the US Brush) and a factory option of 3-3/4 or 7-1/2 ips - but I doubt there are many (any) 1/2 tracks made.

Paper tape could of course be used on any machine and was quite popular for many years - it is surprisingly durable.

TP later bought out a 'plastic' backed tape so yes, a Soundmirror can play standard 1950s tape such as LGS, Scotch-Boy etc.

Good luck!
Barry

[ralph2472]

Thanks for your post Barry.

I noticed that the Soundmirror does have a large pressure pad which is about 20mm long to hold the tape tightly to the head, and was obviously put there for good reason.

Regards

Ralph.

[Nicklyons2]

Some old professional reel-reel machines were full track mono so I would think that you'll get all the 'fi' there is using such a machine. The only problems being the size of reel & the speed and the direction of travel. Do I assume to 'sound mirrors' ran in the (now) conventional LH feed RH takeup? Many 'pro' machines of early vintage didn't run as slow as 3 3/4 ips and weren't accustomed to small reels BUT one or two were; EMI Midgets, Stellavox, Nagra and Tandberg all made full track machines which specialised in small reels for portable recording and some could run at 3 3/4; further, these machines had very good transports.

[ricard]

The original BK-401 Soundmirror didn't have a conventional capstan and pinch roller setup, but the tape was simply wrapped around the rubber clad capstan. Worked well with paper tape, but tended to slip with plastic due to lower friction.

I don't know if Thermionic Products manufactured that version though, or only variants of the later BK-411 etc with joystick control and conventional capstan and pinch roller arrangement.

[ralph2472]

This model does have a capstan and pinch roller setup, and the erase head lifts up into place when recording, and is out of the way during playback; so I imagine that it is energised all the time.

Regards

Ralph.

[kalee20]

Originally Posted by ralph2472

the erase head lifts up into place when recording, and is out of the way during playback; so I imagine that it is energised all the time.

Too right - it's a permanent magnet, with pole pieces shaped to give several flux reversals as the tape passes.

[ralph2472]

Thanks for that kaylee20. I'll have to remember to keep tape away from it.

Regards

Ralph.

[TIMTAPE]

Originally Posted by Nicklyons2

Some old professional reel-reel machines were full track mono so I would think that you'll get all the 'fi' there is using such a machine.

At first glance this may seem so but in my experience, admittedly based only on a small sample of paper tapes, in trying to recover the complete width of the track, I ran into a problem. I found the azimuth setting of the tape constantly wandered around.

A bit of background. At that time, about 10 years ago, I didnt know about Soundmirror/Brush early recorders. When I was first given the tape to preview, I followed my normal practice of playing it on a Teac 3440 machine with 4 discrete channels to get a rough guide as to the track configuration. I was surprised that there was a strong signal on tracks 2 and 3 (in the centre) but nothing on tracks 1 and 4 (at the outer edges). Very unusual.

I knew that I could get a half reasonable result just playing the tape from tracks 2 and 3, where the signal was, but this was a valued one-off live recording. Besides my curiosity was aroused, so I decided to go for broke and try and replicate as closely as I could the head configuration of the original recorder for best results.
I temporarily modified the head on a standard half track machine by lowering the pole piece to read in the centre of the tape, rather than at the top edge. The result? Severe azimuth wandering. A bad drifting, swishing sound. Using the optimally wide track, it actually sounded much worse than if I just used an ordinary 1/4 track machine playing back from track 3. So in the end, that's how I transferred the tape, a live recording of a performance of "Messiah" back in 1954. Track 3 of a 1/4 track machine.

It had taken me some time to modify the playback head. What a seeming waste of time and effort, but actually a valuable learning experience!


Using a fulltrack machine you would probably get the azimuth drift problem in spades, as I did. But also you would be reading the top and bottom edges of the tape, where there is no signal recorded. You would pick up extra noise.

If I was given such a tape today I would play back the tape on the 4 track/4 channel machine, capturing tracks 2 and 3 as a stereo pair. Then I would apply to the digital copy, an "azimuth corrector" plugin to phase align the wandering tracks to each other, and sum to a single mono track for minimal noise and tape dropout.
You see, the azimuth wandering was dynamic. It wandered and changed from moment to moment. It wouldnt be humanly possible to correct for it by adjusting the tape head's azimuth screw while the tape played.

I've since wondered what caused the drifting. I guess something to do with the paper base differentially stretching and shrinking over the years, perhaps due to absorbtion of moisture, a bit like the problem film restorers have with film stock which shrinks over time.

In line with what Ted mentioned, I also had to repair a number of breaks and tears in the paper tape, using splicing tape.

Interestingly, of the various old reel to reel tapes I was given by the lady to transfer, only a couple were paper. All the rest were later recordings on acetate or polyester and recorded in standard half track mono. No such problems with them.

Anyway, apologies for the long ramble on my experience with the paper magnetic tape.

Cheers, Tim

[ralph2472]

Thanks again Tim for sharing your experiences.
I have to admit that it's all beyond my knowledge and resources.
I think I will have to consider having the tapes professionaly re-done because there may be some real historic value.
On the front of one tape box is written "Unabridged Princess Elizabeth" and also "Coronation" On the back of the box is what looks like "Kath Ferrier" and "Princess Eliz" written at the same time; but also it may have been over recorded by Robert Wilson, Now is the Hour, and Norman Wisdom. I hope it's not the Queen that's been over recorded.

Regards

Ralph.

[ralph2472]

Further to my last post, I just did a little internet research on Kath Ferrier.
She was a world famous singer, and attended a private party where the new Queen Elizabeth and Princess Margaret were presnt on 30th. April 1952. She was awarded a CBE on New Years Day 1953, and died on the 8th. October 1953 at the age of only 41.
So now, I'm really hoping that it was Norman Wisdom that was over-recorded.
I'll keep you informed.

Regards

Ralph.

[Tractorfan]

Hi,
Just curious, but I didn't realise that some tape recorders can play tracks 2&3 at the same time? All the four track decks in my experience can only select tracks 1&3 or 2&4 because of the layout of the head. Is this a feature of some decks to have four heads in the one unit? or was it modified to do so?
I've got a couple of Kathleen Ferrier 78s. "Blow The Wind Southerly" was a very famous recording of hers.
Cheers, Pete

[ralph2472]

Sorry I don't have the knowledge to answer your question Pete; but I bet TimTape can help you there.

Regards

Ralph.

[brenellic2000]

..back track to Ricard No.10!

TP only ever made the 'conventional' BK.411 type deck (BK.411 and BK.416 are TP codes) licenced from Brush. Meanwhile Brush produced various variations of that deck including 2-track and speed adjustable models which were also/further developed by Tandberg and Carad... but whether through licence from Brush (USA) or TP (UK), I know not. TP effectively took over from Brush when they abandoned tape decks, especially airfield recorders. Their history is my 'A Truvox Product' book.

Ralph - don't worry to much about the permanent magnet erase head - you have to depress the button to raise it and make 2 or three passes to wipe anything off!

Barry

[ralph2472]

That's good to know about the erase head.

Thanks.

Ralph.