Using dolby for playback

T

TimboW

Enthusiast
I'm trying to transfer over a pile of cassettes to CD using my Tascam 122 MkIII deck. Even though I do follow the advice of the tapes and switch the Dolby B 'on' when playing the tapes to the computer for processing and burning, I find the sound somewhat muddied. Turning it off certainly gives the sound a good deal more brightness.

Is it just my ears, or should I switch the Dolby off on playback? It's always been my understanding that as far as Dolby was concerned what got used going in had to be matched at output for faithful reproduction, right? I'm just not hearing it that way.

Thanks.......Tim
 
Adam

Adam

Audioholic Jedi
I'd say that it comes down to what you like the best. You're the one listening to it, after all. :)

It will have more brightness with Dolby B turned off because Dolby B emphasizes higher frequencies during the recording process, so unless you deemphasize those frequencies on playback - it'll sound brighter. A more in-depth explanation can be found on Wikipedia at this link.

The tapes may sound muddied because they are older and slightly worn out, or your tape playback head might be dirty or magnetized. Did you clean and demagnetize your tape deck first? If not, I'd recommend doing that - especially before you transfer the songs to computer.
 
T

TimboW

Enthusiast
okay

That sounds interesting enough.

I guess from my perspective I'd rather get the process right from an archival point of view and then adjust the sound to suit my tastes later. So am I right that technically speaking the matching Dolby from the cassette should be switched on at playback?

Sounds vary from tape to tape of course, and yes, some of these tapes are 20 - 30 years old and certainly have required a bit of tweaking via Audition. Vocals seem to fade into the background a bit and base becomes a bit muddy.

Thanks again.........Tim
 
Adam

Adam

Audioholic Jedi
So am I right that technically speaking the matching Dolby from the cassette should be switched on at playback?
That is certainly my opinion, yes.

You might be able to find some inexpensive copies of CDs of those tapes, if you were interested in that. Probably better sounding than at least some of those older tapes, and the cost might be worth the savings in time of transferring the tapes to the PC. Just a thought.
 
T

TimboW

Enthusiast
Not a hope.

Hi again Adam,
Not a hope, as far as buying them all again in CD form. I have a vast collection of cassettes and LP's to go with my burgeoning collection of a few hundred CD's, and though I have updated much of the analog material with CD's over the years, I couldn't hope to replace them all - I just couldn't afford it, as I'm talking about thousands of sources. Plus I often bought both an LP and cassette version of the same recording so I could have the convenience of the latter for the car, and I'm somewhat resistant to the idea of letting the recording companies get three bites out of me completely for the same stuff! Some of the material closer to my heart sure, that's just natural, especially as the recordings often get remastered and repackaged at a reasonable price. But most of my CD purchases are directed towards new material.

Another point to bear in mind is that a certain percentage of the analog recordings in my possession simply aren't available on CD - they were just so obscure as to never merit the attention.

As far as the process is concerned, I actually enjoy it. I'm working my way through the cassettes and will then start on the LP's. It may take a few years, but hey, everyone needs a hobby! Cassettes are actually easier to deal with from y perspective, as there are less noise issues to deal with than LP's. The dynamics aren't quite the same, and as time wears on the quality of some of the tapes deteriorate and need tweaking, but I seem to have worked out a nice setting for Audition's graphic equalizer to deal with the issues on most of the troublesome tapes - none of the presets really did the trick.

Thanks for the confirmation on Dolby use. I was 99% certain I was right, but the sound I was getting on a few tapes made me wander if I'd made erroneous presumptions through the years. Could also be that the extra brightness of switching off the dolby sucks you in because of the additional bite at the high end.

Cheers......Tim
 
Adam

Adam

Audioholic Jedi
Tim, I'm glad that you enjoy the process! More power to ya. I gotta tired of transferring CDs to my PC, and that's a lot quicker.

One word of advice - be sure to keep more than one copy of the digital transfer. I transferred my CDs to a lossless format on one hard drive, and then happened to put them on another hard drive in a lossy format (160 kbps ACC). I thought about backing up the lossless copies, but didn't - and then that hard drive went south. Ugggg. Learn from me, my friend - back it up! It's well worth the expense of the extra hard drive(s) or DVDs, IMO.

BTW, it sounds like you have quite a collection of tunes. That's fantastic.
 
TLS Guy

TLS Guy

Seriously, I have no life.
I'm trying to transfer over a pile of cassettes to CD using my Tascam 122 MkIII deck. Even though I do follow the advice of the tapes and switch the Dolby B 'on' when playing the tapes to the computer for processing and burning, I find the sound somewhat muddied. Turning it off certainly gives the sound a good deal more brightness.

Is it just my ears, or should I switch the Dolby off on playback? It's always been my understanding that as far as Dolby was concerned what got used going in had to be matched at output for faithful reproduction, right? I'm just not hearing it that way.

Thanks.......Tim
As a still active tape guy, I see you are finding the problem with tapes.

There are a number of reasons for your problem.

First clean the tape heads with pure isopropyl alcohol on Q-tips. Clean all the heads, guides, capstan and roller.

Next demagnetize the heads with a head demagnitizer. With the device on move it carefully to each of the parts of the tape path, especially the heads. Move it away from each part slowly, with it on. Do not switch it off close to any part, especially the heads, or you will magnetize them. When you do the demagnetization, make sure the deck is OFF, otherwise you may overload the playback amp and blow it.

The above measures usually help a lot.

However it is very likely you have an azimuth problem.

Tape head gaps must be aligned carefully. They have to be in perfect zenith and above all azimuth alignment. This means the gap must be perfectly vertical to the tape, in its path. If it is not there is highly significant HF loss even with VERY small fractional degrees of misalignment.

The play back head is aligned using a laboratory alignment tape. The azimuth band is a high frequency tone 10 Khz for cassette and 15 KHz for reel to reel.. They cost a fortune and I have one for just about every type of two and four track machine both reel to reel and cassette.

You adjust the head with the alignment single phase method first, to get the greatest output watching it on a very accurate amplified meter. You do this to make sure you are not on a secondary or tertiary peak. When you have found the high peak, you then do a careful alignment using the dual phase method.

The alignment is so critical that this procedure needs repeating on a fairly frequent basis.

Now here is the thing you need to understand. All but the highest of the highest end cassette machines were two head. That is to say there was an erase head and a single record playback head. A few were three head, with seperate heads for record and playback. Almost all the decent reel to reel machines were three head.

The point is that if the record and playback heads are the same, there will be no azimuth error when playing back a tape on the machine it was recorded on soon after the tape was made. However if you take that tape and play it on a different machine, the chance for azimuth error is high, unless both machines have been obsessionally maintained.

Obviously if it is a three head machine, the record and playback heads have to be kept in perfect alignment, otherwise you have huge losses. In three head cassette decks, the record and playback heads were physically in the same case as a rule, so that the record and playback heads stayed in the same azimuth alignment, even if they were both wrong.

It is now a long time since tape machines were produced, for home use at least, and tape head alignment was beyond the competence of all but a few owners, so you can pretty much take it as a given that all machines are by now out of azimuth alignment with one another. So severe high frequency loss is going to be the rule rather than the exception. The problem is compounded by Dolby codes, as those codes compound and increase the frequency response errors from azimuth misalignment.

Aligning tape machines, which include not only head alignment, but setting equalization and bias, is rapidly becoming a lost art, and art it is. I'm becoming one of an ever decreasing cadre. ATR services are doing their best to try and reverse the trend by holding frequent seminars to teach what is becoming an extinct art. They hold them at various locations around the country. Registration fee is about $2000 though.

If you click on the link in my signature, you will see some of my tape machines and turntables.
 
Last edited:
bandphan

bandphan

Banned
However it is very likely you have an azimuth problem.

Tape head gaps must be aligned carefully. They have to be in perfect zenith and above all azimuth alignment. This means the gap must be perfectly vertical to the tape, in its path. If it is not there is highly significant HF loss even with VERY small fractional degrees of misalignment.

The play back head is aligned using a laboratory alignment tape. The azimuth band is a high frequency tone 10 Khz for cassette and 15 KHz for reel to reel.. They cost a fortune and I have one for just about every type of two and four track machine both reel to reel and cassette.

You adjust the head with the alignment single phase method first, to get the greatest output watching it on a very accurate amplified meter. You do this to make sure you are not on a secondary or tertiary peak. When you have found the high peak, you then do a careful alignment using the dual phase method.

The alignment is so critical that this procedure needs repeating on a fairly frequent basis.
I find the above to be the same problem with one of my old 3 head nakamichis, if you can follow the steps TLS has outlined you should find the transfer to be much better quality.
 
TLS Guy

TLS Guy

Seriously, I have no life.
I find the above to be the same problem with one of my old 3 head nakamichis, if you can follow the steps TLS has outlined you should find the transfer to be much better quality.
Have you got your Nakamichi set up, or are you able to do it? If not, you are welcome to send it to me for thorough calibration.
 
M

markw

Audioholic Overlord
Basically, everything TLS said is spot on. What makes cassettes so "spotty" in hteir playback quality is the fact thatso many variables are involved, both physical and electrical.

Head alignment is very critical. Many tapes made on many machines were not made with the utmost care and alignment in the first place.

Correct playback depends on the alignment of the playback machine matching that of the machine it was recorded on. As long as a tape is played back on the same machine it was recorded on (and the alignment hasn't changed), odds are that alignment will be less of an issue.

In this case, a two head machine could be more "user tolerant" than a three head machine. Record and playback alignment was guaranteed to be the same. Three head machines took a bit more looking after.

If you're playing back on a different machine and it was recorded on a machine with funky head alignment, you'll have a rough go matching your current alignment to that of the original machine.

Likewise, cleaning, demagnatizing and bias'equalization play a major part in the quality, alignment is the most difficult to compensate for.

And, if you're talking pre-recorded tapes, good luck. The vast majority of these simply suck. No matter what you do, you can't make a silk purse out of a sow's ear. You stand a beter chance getting a quality end result with a home-brew from a record made (and played back on) on a well maintained machine.
 
bandphan

bandphan

Banned
Have you got your Nakamichi set up, or are you able to do it? If not, you are welcome to send it to me for thorough calibration.
I took it in with one of my dats and had the service done, but thank you for the offer. Ive got an old tcd5m sony that im gonna pull out of the storage, and if it needs specing ill pm you.
 
TLS Guy

TLS Guy

Seriously, I have no life.
In this case, a two head machine could be more "user tolerant" than a three head machine. Record and playback alignment was guaranteed to be the same. Three head machines took a bit more looking after.
As I stated three head cassette decks usually had the record and replay heads in the same case for that reason.

And, if you're talking pre-recorded tapes, good luck. The vast majority of these simply suck. No matter what you do, you can't make a silk purse out of a sow's ear. You stand a beter chance getting a quality end result with a home-brew from a record made (and played back on) on a well maintained machine.
The reason being is that these copies were made at high speed. A cassette runs at 17/8" ips and the tapes were duplicated at 15 ips, even 30 ips for a lot, I understand. So a frequency of 10KHz has to be recorded at 80Khz, at 15 ips and 160 KHz for 30 ips. That just isn't going to happen to say nothing of the tape saturation during high speed duplication.

In reel to reel things are a little better. The two tracks before RCA invented the stacked four track head are quite good. Everest did some 71/2 ips reel time copies. An American firm Barclay Crocker did some sane high speed copies at 71/2 ips with Dolby B mostly, and some dbx II. They copied masters from the major labels, especially Argo. I have good examples of all of these, in what I call my museum and it fascinates visitors.

There was much more tape activity in America than Britain. I think this was because there were no good native turntables. In 1959, if you had a Garrard 301 with either a Decca ffss, or Ortofon SPUGT in an SME arm, you had quality very close to modern CD standards, even at that early date. Once Alastair Robertson-Aikman, introduced his first SME arm, along with improvements in cartriges by DECCA and Ortofon, the turntable had it made in the shade compared to pre recorded tape. American companies made big strides in cartridge manufacture, especially Shure and Pickering. However America lacked for good native turntables and arms. If you listened now to one of those rigs connected to a Quad 22 pre amp of the era, with a couple of Quad II power amps connected to a couple of good examples of the Quad 57 speaker, you would wonder at how little progress we have actually made! The biggest improvement should be less hassle factor, however that has been put back by DRM!
 

Latest posts

newsletter

  • RBHsound.com
  • BlueJeansCable.com
  • SVS Sound Subwoofers
  • Experience the Martin Logan Montis
Top