Tape Restoration Help

[roxie2401]

Hi - First, let me say that I am new to DC6, but so far, WOW!

My first project is to preserve/restore my reel-to-reel tape library, and boy, do I need some suggestions.

My theory, so far, is that "disk" content (78's, etc.) is that the intelligence is still on the disk, although mask by clicks, pops, etc., but the material is still "in the grooves."

But, what I'm beginning to suspect is that with tape, the intelligence is deteriorating or literally falling off the tape.

When I play some tapes that were recorded back in the early 60's, I find two things - (1) tape hiss and (2) very "boomy" or low end but no highs.

The tape hiss, I think the EZ Clean filter will correct but I'm at a loss as to high to restore the high frequencies that seem to have disappeared over the years - its like the magnetic particles that made up the high end are missing.

Do I attenuate the lows?

Anyone who can help me get started, or who has experience with DC 6 and tape restoration, or who perhaps has some preset filter combinations - I would love to hear from.

Is the intelligence indeed missing from the tape? Is my theory correct?

Help Wanted!

[Craig Maier]

Before talking about the software aspects of things, I am suspicious about the condition of your tape player. All of my old reel to reel tapes from that period of time still retain much of their top end. However, I have encountered problems when the playback head on my tape deck has worn out. Literally, the playback tape head gap becomes much wider than it should be due to wear and then the high frequencies literally disappear, leaving behind mostly a very boomy sounding bass.

So, how do you confirm whether or not this is the problem? There are two ways:

1. Take the machine to an expert and have the person attempt to evaluate and calibrate the machine.

2. Take one of your old tapes which play poorly and play it on a different machine and compare the sound of the top end (highs). You may have to find a friend who has a reel to reel machine in order to do this.

I recommend doing all of these things first; it is important to start out with the best signal possible before commencing the restortion process.

Once you confirm that your machine is in good working order, then we can provide some more hints about restoration, etc. Let us know how you make out with this initial aspect of things.

[roxie2401]

Craig,

Thanks for the quick reply.

I am using an Ampex ATR-700 - which was a broadcast machine. I just had it completely serviced by "New Jersey Factory Service" - they are a TEAC/TASCAM service facility and since this machine is really a TEAC with an Ampex label - it was the right place. They did all the normal stuff - torque, tension, electronics, heads, etc. So, it was back in factory specs a few weeks ago. That's the good news - what it cost - well, ........

Anyway, I think we can start with the machine being as close to good as possible.

[Dan McDonald]

My open reel tapes from the late 60s and early 70s still sound about as good as they did then also. I think our tolerance for noise is lower because of CDs. We used to expect hiss with tapes, some rumble from lps, etc. now we hear it and want to get rid of it, but back then it usually wasn't a big deal, so make sure the highs were there in the first place. I think, even if you're sure your machine is good, try out the tape on a different machine.

Also, what is the speed they are recorded at? 3&3/4 ips on an early 60s machine is not going to sound very good, even on a really good open reel. Also, mono or stereo makes a difference - what were they recorded with (mono or stereo) and how are you playing them back?

Dan

[Craig Maier]

To really be sure that the machine is ok, do the following test:

Obtain a blank reel to reel tape (virgin if possible). Record a snippet of a very high quality CD onto that tape. Play it back and listen to be sure that the highs are all there. You never know if the service place did all the right things.

If that all checks out ok, then we need to somehow figure out if the recordings were made with the proper EQ. Electrical era 78's used a turnover curve, but no Rolloff. If these records were originally recorded onto tape with a standard RIAA phono equalization preamplifier, then the top end will be chopped off. So, do you know what kind of preamplifier was used? Were the records from the electrical era or the acoustical era?

If the records were from the acoustical era (up to around 1925) no EQ is required. If this is the situation, then you need to apply the "Reverse RIAA Phono Equalization Curve" found as one of the presets under the paragraphic EQ. If these records are from the Electrical era (circa 1925 on forward) then you need to apply the "Reverse RIAA w xxx Hz 78 Turnover" curve with the assumption that a standard RIAA preamp was used to record them (a pretty good assumption). Since you probably do not know the brands of the various records, I would tend to use the standard "Reverse RIAA w 500 Hz 78 Turnover" curve, as this was the most common one in use.

By doing this as the first step in the restoration process and establishing the proper EQ, the boomy bass should be reduced and the highs should become in better balance with the rest of the signal. Once this is done, then you are ready to go to the noise reduction phase of the project.

Let us know how this phase works out.

[Geebster]

Also, were the tapes recorded on said machine? If not the fault may lie in the original recording machine; or the alignment of the heads between the two recorders.

The original tapes won't sound any better than the equipment it was originally recorded on.

I, too, have tons of reel tapes that I made from time to time from the 60s-80's and they still sound good.

Lastly, were the tapes subjected to any storage problems (e.g. hot attic, wet basement) or were in contact with electro-magnetic fields?

GB

[Geebster]

To really be sure that the machine is ok, do the following test:

Obtain a blank reel to reel tape (virgin if possible). Record a snippet of a very high quality CD onto that tape. Play it back and listen to be sure that the highs are all there. You never know if the service place did all the right things.

Excellent point. Take it from somebody who has been there. I took one of my reel decks to a supposed "factory authorized" dealer about 10 or so years ago, and when I got it back it was so out of adjustment that it took a lot of work to get it working properly again. Qualified tech's will provide the testing/servicing means and data if asked. Hacks will balk if you ask the same thing.

Finding a good audio tech is about as difficult as finding a good car mechanic.

GB

[roxie2401]

Dan,

The tapes were orignally recoreded on a full track Magnecord machine at 7-1/2ips. They were done in a radio station environment (output from mix console and not off-air receiver). I still have some of the LPs and the highs are present on the vinyl, but not on the tapes. Also, the announce (voice) has very low end - that's why I suspect the tapes have begun to deteriorate and loose the highs.

I will look for another R-R machine and try the tapes there. Also, the Ampex machine is switchable between 1/2 track and 1/4 track - but I'm thinking that shouldn't make too much difference on something that was recorded full track originally.

But, how should I begin using DC6 on these tapes? Hiss, I can live with - its the extreme absence of highs (or excessive low end) that is most bothersome.

Thank both of you for the quick replies. Hopefully, there are some DC 6 tools that will help, too.

[Geebster]

By doing this as the first step in the restoration process and establishing the proper EQ, the boomy bass should be reduced and the highs should become in better balance with the rest of the signal. Once this is done, then you are ready to go to the noise reduction phase of the project.

Let us know how this phase works out.

The above paragragh is your starting point. If you need further assistance pages 262-267 (in the DC 6 manual) has some good info about tape recording and restoration.

GB

[roxie2401]

Craig,

Thanks for the info on the EQ.

Now, some more clearification on my part - much of what I'm trying to restore are tapes of radio broadcasts (done from the studio mix console) so they include "music" but also announce/talk. So, it is the entire program content that I am trying to restore.

So, do your comments about the EQ apply and the RIAA curves? Would not what was coming out of the mix console into the tape recorder be correct EQ for everything? Or, am I going to have to EQ the LPs and the voice separately?

Basically, it is everything on the tape that sounds pretty "muddy", not just the LPs but the entire broadcast. (The good news, at least, is that this was not recorded "off the air" but in the same audio chain as was going to the transmitter (before it hit the FM pre-emphasis equipment, etc.)

[Craig Maier]

Somehow, I had thought that these recordings were of 78's not LP's. If they are of LP's, the EQ is probably correct. I was only suspicious of the EQ if they were 78's, because a lot of people played 78's through phono pre-amps designed for LP's only. And no, you would not want to apply any reverse EQ on the announcers voice; that would completely throw off the tonal balance of the show.

If these tapes are that dull, the first thing that I would consider doing is some pre-emphasis, even before attempting to de-click or de-hiss them. There are two presets found under the paragraphic EQ to try:

1. 25 uSec Pre-Emphasis

2. 3 KHz Boost with 12 dB Shelf

Try both and then use the one that sounds best on the material. Keep in mind that the hiss level as well as the highs will also increase, but that is ok. If neither of those presets improves the highs, then there is something dramatically wrong with the recordings in all likelyhood. Perhaps the Magnecord that made the tapes was out of calibration or had a faulty record head and nobody realized it at the time. It is very unusual for tapes to loose their top end over time unless they are subjected to extremely high levels of magnetic fields for protracted periods of time.

After you choose the best pre-emphasis preset, then you are ready to use the EZ Clean filter. I would recommend using that one first, since you are a newbie and it is easy to use and produces pretty good results with a minimum amount of experience with the software. Let us know how you make out.

[Craig Maier]

Flipped tape?

Here is another possible explaination for the lack of highs on your tape. Several times, I have encountered single track reel to reel tapes which somehow or another became flipped. What I mean by that is that the oxide side of the tape was facing the outside of the reel rather than the inside. When played like this, there is only bass, no highs and the playback head amplifier hiss is quite prominent. If this is the case, it is easy to correct. Just fast forward the tape with a 180 degree twist in the tape somewhere along the tape pathway and then rewind the tape again.

Just a thought.

[roxie2401]

Craig - That's sort of like "green side up" on sod!

No, the oxide side is definitely against the playback head, with the shinny side on the outside.

I'm going to work with the pre-emphasis issues and get back to you with the results.

I'll also go look for another r-r machine to see if its a head alignment issue - I used to have a Wollensak machine with adjustable heads - little knob to raise or lower the head position - too bad I sold it.

I'll let you know the results - but, thank you and the others today so much for the "getting started" help. The forum is great!

[Craig Maier]

Quoting roxie:

"Craig - That's sort of like "green side up" on sod!"

----------------------------------------------------

Well, not exactly. There were tape formulations (especially pro-grades) in which both sides of the tape were dull in texture and very similar in color. On those tapes, it was not always easy to determine which side had the ferrous oxide. I think that this was done to improved the friction between the capstan and the pinch roller to reduce the possibility of tape slippage.

And, there were also tapes in which both sides were very glossy. I believe that some tapes oxide sides were "burnished" to reduce tape head wear and improve tape to tape head contact thereby improving performance.

[roxie2401]

The above paragragh is your starting point. If you need further assistance pages 262-267 (in the DC 6 manual) has some good info about tape recording and restoration.

GB

GB - this will sound dumb, but where do I get the manual? Is it on-line? I purchased DC6 last year as a download - was that a mistake in that I didn't get the manual?

I think it was around the end of 2005 and a "special" promotion as "download only."