Digitizing old reel-to-reel tapes

[Telfon]

I have about 20 old 7" reels of 1/4" 4-track tape that my father recorded back in the 50's and 60's on a Sony Tapecorder 262-SL. My goal is only to digitize the audio of the tapes into the computer so I can locate the parts of sentimental value for our family and send copies to family members. Most of the recordings are conversations, recorded church services and stuff recorded off of the AM radio.

I have gotten the old deck running but the playback is very muddy. I've cleaned and demagnetized the heads but I think a lot of the problem is in the old electronics, switches and vacuum tubes. The transport mechanics seem solid.

I'm wondering if I can just grab the signal right off of the tape head itself and sample it into the computer. Would a microphone input on the computer be sensitive enough? I know it has to be a dynamic mic input as a condenser mic would basically just erase the tape. My research online seems to indicated that I need to pass it through an NAB equalizer but I'm hoping I can just do that digitally on the computer.

I've checked into having it done professionally but the cost is way more than I can justify for some old family recordings. It would cost less to just buy a 70's era reel-to-reel deck off of eBay but I'd end up using it once and having no need for it again. I'm trying to do this quick and easy and 10 minutes with an old microphone cable and a soldering iron is both. I just don't want to damage anything in the process so I thought I'd ask some advice of the experts here.

Thanks in advance for your help,

-- Paul

 

[MarcelvdG]

Have you checked whether the tape gets pressed to the head sufficiently?

I don't know the answer to your question, but computer microphone inputs are usually rather poor noise-wise, at least those on standard computer soundcards.

 

[AuroraB]

You will most probably need a preamp, and with the apporpriate correction circuit. I seriuosly doubt that just sending it to a mic input will work well.
Have you tried cleaning switches etc....?

However - googling 'tape head preamplifier' or 'tape head amplifier' could probably reveal som simple op-amp circuits that can be made on a piece of vero board.....

 

[Telfon]

There are felt pads that hold the tape against the head. I'll apply a very light pressure to it and listen if the playback improves. I think it is all good however.

I do have a higher-end audio card with digital in/out and full 6 channel analog audio. I know that isn't a guarantee the tape input is any good however.

How about a phonograph input on a receiver? I know the eq would be wrong but I can fix that as long as I have a decent sample. I'm not trying to get the ultimate transfer, just something intelligible without excessive noise that can't be removed with digital filters.

 

[MarcelvdG]

Frankly, I haven't a clue what impedance your playback head has or what kind of load impedance it is meant for, so I also don't know what kind of other amplifier comes close in noise matching or load impedance.

What I can say is that when I used to play with old tape recorders in the 1980's, the most common reasons for very dull sound were dirty heads and insufficient pressure on the felt pads.

Other possibilities are incorrect azimuth (playback head not exactly at the same angle as the recording head), worn-out heads, tape partly de-magnetizing itself after long storage or simply inadequate recording tape speed. For studio quality recordings, 15 in/s was the usual speed, for good-quality home recordings, it was 7.5 in/s, for not so good home recordings, 3.75 in/s. Anything below that is likely to sound quite dull even if the tape recorder and tape are in perfect working order.

Why do you think it is due to the electronics?

 

[dchisholm]

Frankly, I haven't a clue what impedance your playback head has or what kind of load impedance it is meant for . . .

You can connect pretty much any amplifier, and perhaps even get an improvement over the performance you now have, but without some knowledge of the tape head's electrical characteristics you're shooting in the dark. The tape head is a transducer not completely unlike a loudspeaker. You can throw any loudspeaker into any enclosure and get it to make noise, but the sound is more likely to be pleasing if you consider the Thiele-Small parameters in your design decisions.

What I can say is that when I used to play with old tape recorders in the 1980's, the most common reasons for very dull sound were dirty heads and insufficient pressure on the felt pads.

Other possibilities are incorrect azimuth (playback head not exactly at the same angle as the recording head), worn-out heads, tape partly de-magnetizing itself after long storage . . .

I'll bet there was at least as much thought and effort put into the tape deck's mechanical design as its electrical design. In the half century or so since that machine was built, and much of that time inactive (which begs the question of the conditions it was stored under), a lot of things can happen that are essentially mechanical in nature. Heads become misaligned due to thermal expansion/contraction cycles in their mountings. Rubber-like parts lose their elasticity, or entirely disintegrate. Springs lose their temper. Felt pressure pads harden and don't conform to the shape of the head, or fall apart and don't apply adequate pressure. It's possible for hobbyists to correct these types of mechanical deterioration in many (but not all) cases.

(Be careful about aligning tape heads! Tapes recorded on a machine with poor head alignment can sometimes play well on the machine where they were recorded - but ONLY on that machine. "Correcting" the head alignment on that machine may make the tapes unusable. )

You have already been advised to clean switches and potentiometers. I don't care whether you want to classify this as "mechanical" or "electrical" maintenance - it's a straightforward, inexpensive task that sometimes yields significant improvements.

The recording tape itself may have deteriorated. The classic culprit is stray magnetic fields - from power transformers, motors in appliances, nearby loudspeakers, etc. Some plastic tape-base materials lose elasticity over time and require extra pressure to achieve good contact with the tape heads. Some brands and formulations of tapes are notorious for shedding the oxide recording particles over time. In some cases this wasn't discovered until it was decades too late to save the recorded program content. Unfortunately there's very little that us mere mortals, who lack access to exotic and expensive signal processing facilities, can do to recover program content from deteriorated tape.

Why do you think it is due to the electronics?

In my mind, this is the most significant question. With a few notable exceptions (which I'll mention in a moment) the electronics don't wear out. Restoring your tape recorder's electronics to near-new performance may take no more time or money than creating a new electronics chain. Remember, you only need to get a couple stages of playback amp up and running - Sony circuit designers already worked out all the details of tape head interfacing, gain, playback equalization, etc!

I don't know that model (Tapecorder 262-SL) - are the electronics vacuum tube or solid-state? My first-hand experience includes a couple of TC-250's and TC-355's from the late 60's and early 70's, and they were transistorized units. Does your deck provide line-level outputs, or only a built-in speaker amplifier?

Considering nothing more than the age of your consumer electronic product, the electrolytic capacitors are prime candidates for replacement. A leaky electrolytic used for interstage coupling will upset biasing and frequency response of the overall unit, which might be described as a distorted or "muddy" sound. (Most home entertainment gear from that era used coupling capacitors between every amplifier stage, rather than DC coupling with capacitors only at input and output as we do today.)

Vacuum tube electronics didn't use as many electrolytic capacitors. Outside the power supply, look for them as cathode bypass capacitors rather than interstage coupling - though the paper-and-foil capacitors sometimes used between tube stages may also become leaky over time and should be replaced. Of course, the vacuum tubes themselves should be checked on a tube tester if you can find one. As a pragmatic matter it may be easier to simply replace very common tube types (e.g., 12AU7, 6AQ5, etc) than to find a tester for the ones you have. If you can get an annotated schematic for the unit and the tube voltages are pretty much in line with the published values, I wouldn't worry about replacing tubes.

Dale

 

[stellavox]

Paul,

From the info you've provided, if you're listening to the tapes on the machine they were recorded on, perhaps the machine is working correctly and its "quality" (including the original microphone) is the issue.

Simple "stupid" question - depending on how the tape is threaded, could you be actually playing the "back" of the tape? I've done this a number of times by mistake - if so the highs will be substantially reduced. If "playing with" the pressure pads does help the highs, then optimize them, finish your dubbing session and scrap the deck.

Next suggestion would be to try and borrow another tape deck.

You can connect the head to the the phonograph input of a receiver (electrically, a "typical" tape head "looks like" a "typical" magnetic cartridge). In fact I'd try that if you want to take the time. You should get enough output from the head to get a decent signal out of the receiver AND although the fixed playback equalization is incorrect, if the receiver has tone controls, you may be able to adjust them to get "acceptable" quality for dubbing. If the original tonal balance on the tape is the problem, then inserting an equalizer in the signal path (tape in/out?) may also help.

Good luck and let us know how it turns out!

Charles

 

[Telfon]

Pressing the felt pads to the head did improve the sound considerably. I didn't want to keep them pressed on too hard but it improved more and more the harder I pressed.

So where can I get proper felt pads to replace the ones that are there? Is there a special type of felt?

If the spring has lost some of it's tension, what can I do to improve it?

Thank you a bunch to everyone for your help. You assistance has been great.

The unit has both tubes and transistors by the way. It must have been built during the transition phase when tubes were on the way out and transistors were coming in.

-- Paul

 

[dimitri_dimitri]

You could use the round felt pads destined to protect table surfaces. Not the heavy duty ones for chair legs!!
Trip to the local craft store should take care of that
If you dont' feel like taking a trip, you could also try to use a bandaid (some are softer than others). I'm sure you get the idea

 

[lcsaszar]

The reason of inadequate tape pressure to the head is frequently the inadequate braking of the supply reel. There should be the belt (if there is any), spring and felt checked. It must not free running, unlike at the cassette decks where the tape is pressed to the head by the built-in felt pad in the cassette. There is no felt pressing the tape to the head at better quality reel to reel tape decks. Pressure is provided by properly adjusted tape tension. I would recommend to check this first.