Tape Differences - 206/SM911

[fstrat76]

I was performing a test to see which tape, Scotch 206 or RMGI SM911, that I want to use to do a final mix to. I used a stereo mix from my DAW into my Tascam 42. The 42 is calibrated for RMGI SM911.

First, I set all the levels, pushing about +1 or +2 VU and I recorded the mix onto RMGI SM911.

Second, without changing the levels, I recorded the same mix onto Scotch 206.

I recorded those mixes back into the DAW so I could easily A/B.

Of course, the 206 is a +3 tape vs +6 for the SM911 so I expected to hear some differences since I was pushing the tape just a little bit. To me, the 206 sounded better, the SM911 was a little clearer. I noted that the 206 had a lot less hiss than the SM911.

I am probably missing something obvious in this test but my question is why? Why is there less hiss on the 206 than the SM911 when the machine is calibrated to SM911?

 

[miroslav]

I just did some mixes on 911...I get no hiss, it's dead quiet....my deck is also calibrated for the 911.

 

[sweetbeats]

Maybe the hiss is a bias issue. I'd try messing around with the bias. Bias and the HF record eq are kind of tied together in a way in that changes in the bias effect the HF response and vice-versa. Don't know how your response curves are coming out when you calibrate with the SM911 but that might be part of the issue with the noise.

I'm not surprised that the 206 sounds "better" and the SM911 sounds "clearer". That's tape saturation. You calibrated the deck to 250nWb/m at 0VU? And your VU peaks during tracking are at +1 to +2VU? Remember that those peaks are average peaks because the meters are averaging meters, so your actual peaks are well above that (depending on the program content). So certainly you are pushing the 206 into its maximum operating level (MOL) and therefore you are sure to get saturation distortion and other artifacts which typically sound pleasing to the ears of us tape duffers. You are further from the saturation level with the SM911 and it will certainly sound more clear compared to the 206. And the beauty of the +3 tape is that you are keeping a healthy buffer between the levels to/from tape and the peak operation of your record and reproduce amps. IOW you have the machine setup exactly how Tascam designed it to be setup (250nWb/m @ 0VU) so you know the amps are happy pushing that level of signal, but you are dropping tape on there that saturates at a lower level. Best of both worlds...you keep your amps happy and you get more analog tape artifacts.

This is a perfect example of why running +9 tape and setting a machine up for 370nWb/m or 520nWb/m or whatever doesn't get you more better "phat tape compression"! If you put a higher output tape on the machine and keep your operating level the same you are actually moving further away from saturating the tape unless you bury the meters and then you are pushing your amps. Same thing with using the +9 tape and increasing the operating level...you will likely reduce the noise floor some but now maybe 0VU is equivalent to pushing the meters into the red (depending on how you set the machine up) which means you are pushing your amps. I gaurantee that there are those out there that do this thing of using +9 or higher output tape and bury the meters and think it sounds awesome but what they are really hearing is their record/reproduce amps distorting. So if that sounds awesome to them, that's fine and I'm glad they're happy but who knows what they might think if they setup the machine for a +6 tape, and then rebiased for a +3 tape and kept their levels nominal. I'm convined there would be at least some that would say "no way...what'd you do? THAT sounds awesome!"

So kudos to you for your experiment. It presses an important point.

It would be interesting to record a tone ladder to each of the tapes you are using and then reproduce and use a true RMS meter to measure the output level of each of the tones from each of the tapes and compare the response curves. That would be a more quantifiable way to diagnose what's happening with your noise issue because the Tascam meters are not so good at high frequencies (i.e. they are not flat). They're fine IMO once you get used to their response curve because then you can just take that into account when you are calibrating, but if you assume they are flat to 20kHz then your response curves will not be quite what you think they are.

 

[fstrat76]

You calibrated the deck to 250nWb/m at 0VU? And your VU peaks during tracking are at +1 to +2VU?

That's correct, calibrated to 250nWb/m at 0VU. I can check it again. I think I used the meters to measure the bias setup for the SM911 but maybe this time I will try the LF listen method.

However, that still seems odd to me; for example, even if I rebias using the SM911 and it makes the SM911 a little quieter, wouldn't the same logic apply and that the make the 206 even quieter?

 

[miroslav]

I gaurantee that there are those out there that do this thing of using +9 or higher output tape and bury the meters and think it sounds awesome but what they are really hearing is their record/reproduce amps distorting.

Yup...if you bias "up", it's easy for the VU meters to fool you, and you end up slamming the electronics.
I usually make a few passes with the mix, adjusting the recorder's input level until I hear what I like, without really using the meters as my main guide.

I also find the 468 to be "clearer" than 911, but you can also get some "hair" out of the 911. I only like a small amount on a mix...just to glue things, rather than going for more obvious saturation.

 

[sweetbeats]

Yeah, 468 was developed as "archiving" tape with some added HF response to combat the long-term HF losses in stored tape right? Something like that? And I understand many do like it over other +6 offerings for that "clarity".

However, that still seems odd to me; for example, even if I rebias using the SM911 and it makes the SM911 a little quieter, wouldn't the same logic apply and that the make the 206 even quieter?

That's a dubious question because different tapes have different response curves and different bias requirements and the response curves change depending on the bias level applied...its a moving target. Logically, yes, if the 206 is quieter than the SM911, and you make adjustments to decrease the tape noise with the SM911 one would think that would FURTHER decrease the tape noise of the 206, but...moving target. That's why I was saying to record tone ladders to both tapes at the same level so you are comparing present "apples" to present "apples" and then measure the response coming off tape and see where you are at.

And I can't over-emphasize the role of bias here...let's say that 206 has a lower bias requirement than the SM911, which is a reasonable assumption (not a guarantee, but a reasonable assumption for the sake of argument) since it has a thinner oxide coating. If the machine is biased for SM911 and you don't rebias for the 206 then of course the tape noise is going to be diminished with the 206 because its over-biased which diminishes your HF response, including tape noise. Just a "for instance" there for you.

The answer is to be found in comparing the current responses of the tapes with a true RMS meter and also seeing what happens when you bias to the 206. You may be somewhere in between. Maybe you are slightly under-biased for the SM911 (higher HF noise level than when at an ideal bias level) and still over-biased for the 206 (diminished HF response). Point is I wouldn't go over-analyzing it until you've played with the bias level with both tapes, and, as you mentioned, maybe trying another method. I am really not fond of using the standard "XdB's overbias" that most manuals recommend after my experiments with my 388. I understand that that method is a pretty reasonable method as long as you are using the tape spec'ed by the manufacturer (like, THE tape down to brand and type) and the machine is calibrated to factory spec, but there just doesn't seem to be any better way of setting up the bias than a true feedback method like the LF modulation method where you can actually HEAR the effect of bias level on the distortion and noise...finding that point right where the noise and distortion are at their minimum. And don't forget...there is nothing that says that that point is THE POINT that is best for all source material...purposely over or under biasing could getcha some effective results...whole 'nuther topic...just promoting keeping an open mind about all this...who knows what magic is lurking in your tape machine??

Anyway, fstrat, if you dig into this let us know what you find out.

Good stuff and thanks again for the info and the questions.

 

[fstrat76]

And I can't over-emphasize the role of bias here...let's say that 206 has a lower bias requirement than the SM911, which is a reasonable assumption (not a guarantee, but a reasonable assumption for the sake of argument) since it has a thinner oxide coating. If the machine is biased for SM911 and you don't rebias for the 206 then of course the tape noise is going to be diminished with the 206 because its over-biased which diminishes your HF response, including tape noise. Just a "for instance" there for you.

Ah, well if that is a reasonable assumption, then what you say here makes perfect sense. Perhaps I am just hearing the HF rolloff on the 206 and less of the saturation. However, I know the stereo image on the 206 also "comes in" a little, if that makes sense. Maybe that's the "glue".

My understanding though is that 206 and SM911 are bias compatible, however you are right in that it might be a moving target.

I will check the bias again, and I also use the LF modulation method. Not sure I did originally on this deck, but I will next time.

I like the idea of trying a tone ladder on the tapes. I am not sure I can measure accurately though. I have a Fluke 114. It says True RMS, but I don't think it is "true" True RMS.

While I'm in there, I may try experimenting with some other tapes I have as well. I have some older NOS BASF LP35 and even older NOS BASF LGS 35. I don't think these are bias compatible with the 206/SM911 though.


As far as re-biasing, do I have to recalibrate the entire deck, or only the bias steps and thereafter?

 

[sweetbeats]

I know the stereo image on the 206 also "comes in" a little, if that makes sense. Maybe that's the "glue".

By "comes in" you mean the soundstage narrows?

And I tend to think of "glue" in this area as a mix that just fits together better...that works better...

My understanding though is that 206 and SM911 are bias compatible...

Well, um, I'm kind of surprised at that but I've got a lot to learn in interpreting the specs.

The coercivity of the two is the same at 320 oersteds...I read that coercivity is the measure of the flux required to reduce a magnetic medium to a neutral state when that medium is charged to saturation...kind of like how hard the medium holds on to its magnetic state.

The retentivity of the two is quite different; 1050 gauss for the 206 and 1450 for the SM911...I read that retentivity is the measure of flux level remaining on the medium compared to a known magnetic charge, IOW how well the medium retains the flux level to which it is exposed and in this case that would be the flux present at the record head during recording. I'm seeing this as sort of a measure of efficiency...what level of flux remains on tape after it passes a given flux level at the record head.

The Oxide thickness is pretty close...0.56mils for 206 and 0.63mils for SM911.

So where does that leave us? I dunno, but there are differences in the specifications, and its hard to imagine that they'd be totally bias compatible. Certainly they perform differently, they sound significantly different on your 42 all settings being the same...and note that the specifications charts don't cover the oxide formula itself...what it is made of...what percentages of what and so on and that in and of itself effects how the tape performs and what is required for optimum performance.

I go back to Quampex 457 and BASF/EMTEC/RMGI LPR35...this is related to my recent experiments on my 388. The manual says to set the bias amp output to 150mV for proper biasing of the tape. That was for 457. My testing resulted in a nominal setting of about 115mV for LPR35 using the LF modulation method. There's more detail in my Tascam 388 Story thread, but those are both "1mil +6" tapes. They ain't bias compatible, and from a marketing standpoint they are a much more similar pair of tapes than 206 and SM911.

I like the idea of trying a tone ladder on the tapes. I am not sure I can measure accurately though. I have a Fluke 114. It says True RMS, but I don't think it is "true" True RMS.

If it sez "true RMS" it is true RMS reading, 'nuf sed.

Looking at the manual for the 114 the catch is that it is only reasonably acurate from about 45Hz to 1kHz...that's the window of accuracy for the AC voltage section, so Fluke is saying "we don't gaurantee the accuracy outside of that frequency range." I'd say forget measuring HF tones with it. Great meter for general use though and certainly you can use it to setup and verify levels at 1kHz and get an idea of what is happening down into the LF range...see where your head bump is and all that. See if you know anybody that has something like a Fluke 83, 85 or 87 you can borrow and then you can note the deviation of your meters at high frequencies and then just use the meters after that mentally adjusting for the deviation.

While I'm in there, I may try experimenting with some other tapes I have as well. I have some older NOS BASF LP35 and even older NOS BASF LGS 35. I don't think these are bias compatible with the 206/SM911 though.

No, I wouldn't think so.

As far as re-biasing, do I have to recalibrate the entire deck, or only the bias steps and thereafter?

Assuming you are okay hitting different tape types (i.e. +0, +3, +6 etc.) with the same nominal level, or adjusting mentally what you are treating as "0" on the meters, there is no reason to recalibrate the levels of the electronics. And I figure if you have the electronics adjusted for resonably flat response with one tape type properly biased, then rebiasing to another tape type should keep you in the same response curve neighborhood save for the individual anomalies or character of the different tapes. Does that make sense?

Good stuff. Have fun!

 

[RRuskin]

I was performing a test to see which tape, Scotch 206 or RMGI SM911, that I want to use to do a final mix to. I used a stereo mix from my DAW into my Tascam 42. The 42 is calibrated for RMGI SM911.

First, I set all the levels, pushing about +1 or +2 VU and I recorded the mix onto RMGI SM911.

Second, without changing the levels, I recorded the same mix onto Scotch 206.

I recorded those mixes back into the DAW so I could easily A/B.

Of course, the 206 is a +3 tape vs +6 for the SM911 so I expected to hear some differences since I was pushing the tape just a little bit. To me, the 206 sounded better, the SM911 was a little clearer. I noted that the 206 had a lot less hiss than the SM911.

I am probably missing something obvious in this test but my question is why? Why is there less hiss on the 206 than the SM911 when the machine is calibrated to SM911?

You are slightly over biased just enough for the 206 to shave off some high-end and thereby lowering the perceived hiss level.

 

[Beck]

Some good input so far. I'll add that 3M/Scotch 206 (and 207) just happens to be an excellent tape. This is the favorite tape of Tom Scholz when tracking the first three Boston albums, so nearly everything from "More Than a Feeling" to "Amanda" was tracked to 206. As recently as 2007 in an interview Scholz calls 206, “The best sounding recording tape that's ever been used.” In another interview I believe from the '90s he went into some great detail of how he rigged a front panel bias control on his Scully 280-Series 1" 12-track to fine tune 206 for best noise and clarity. He talked about it having a sweet spot he couldn't get with any other tape. Although a sweet spot exists with every tape I guess he found 206 more to his liking. Can’t really argue with 17x multi-platinum and counting… and that’s just the debut album. SM911 is a great tape, but I’m never surprised to hear people discovering the joys of 3M 206.

 

[fstrat76]

By "comes in" you mean the soundstage narrows?

And I tend to think of "glue" in this area as a mix that just fits together better...that works better...

Well, it's hard to explain, but the 206 seems to narrow more perhaps because the highs are lopped off due to over-bias, because the mids and lows move ever so slightly to the center compared to the SM911. Maybe some of this is saturation?

Assuming you are okay hitting different tape types (i.e. +0, +3, +6 etc.) with the same nominal level, or adjusting mentally what you are treating as "0" on the meters, there is no reason to recalibrate the levels of the electronics. And I figure if you have the electronics adjusted for resonably flat response with one tape type properly biased, then rebiasing to another tape type should keep you in the same response curve neighborhood save for the individual anomalies or character of the different tapes. Does that make sense?

It makes sense. I know people talk about sticking with one type of tape, but I like to experiment to grab a particular sound and that may mean using different tape types per set of songs. I still want to try the LP35 and even the LGS 35.

That 42 is a monster and I have some limited space now. I don't have the machine where its easy to access the bottom panel to get at the controls all the time. It would be ideal to hookup the 42 so as to make it easy to adjust bias. In other words, I want to spend 5 minutes re-biasing for different tape rather than an hour or two. Guess I'll have to figure that out. But does constantly adjusting the controls put some strain on the electronics?

Interesting, as I like the Boston mixes and sound on that first album, but one album that really stood out to me recently was the Genesis "Genesis" album. I played the vinyl recently and just thought that was amazing, even though they probably did some digital things in there at that time.

But so far, the 206 sounds great and probably will sound even better when I re-bias for that sweet spot.

 

[lo.fi.love]

Just wanted to give a +1 for SM468. Compared to 911, *my* opinion is that 468 has more "presence" and clarity. I really enjoy it on my 8-track... I use it without NR and the very small amount of hiss built up over bounces can be EQed out pretty easily.

 

[sweetbeats]

Beck, the anecdotal info is invaluable.

I still remember as a teen getting turned on to Boston's first release, getting the vinyl and just blasting "More Than A Feeling". Fantastic sound...epitome of guitar driven rock.

Well, it's hard to explain, but the 206 seems to narrow more perhaps because the highs are lopped off due to over-bias, because the mids and lows move ever so slightly to the center compared to the SM911. Maybe some of this is saturation?

I really don't know. I tend to equate soundstage dimension with phase distortion...better phase alignment across the spectrum and you get a more acurate reproduction of the stereo field...certainly there's more at play. In general program material monitored off a tape deck sounds "wider" to me than when not, but tape-to-tape comparisons? Dunno. Conjecturing here, but if there is over-biasing at work here then loss of HF clarity could certainly, from an intuitive standpoint, give the perception of a more narrow soundstage...

It makes sense. I know people talk about sticking with one type of tape, but I like to experiment to grab a particular sound and that may mean using different tape types per set of songs. I still want to try the LP35 and even the LGS 35.

I can't encourage you enough to play around with different tapes, operating and tracking levels and even bias settings. Really. Again, that is one of the hidden perks of an analog tape machine in that you have a cadre of mix and match elements with infinite settings with non-linear results. Better than a bundle of "plugins" for sure.

And it would be good to setup the 42 somehow so you can get to that bottom trimmer panel. Set it on its back?

Really, when switching between tape types bias is the only thing that is critical IMO. No reason to recal to a different operating level because you can essentially do that on the fly by mentally adjusting what you treat as "0" on the VU meters...switching from +6 tape to +3 and you want to keep the same amount of headroom from the tape's MOL? -3VU is now your new "0". Done. And if you know the machine has been calibrated relatively recently then you know that the electronics are adjusted for response within spec and also that the channels are lined up. That's all that really matters and bias is the biggie when going from tape to tape. Sure, sticking to one tape is less complicated, but what fun is that??

Again, keep us posted.

Good stuff.

 

[sweetbeats]

Hey...all this talk of 206 reminded me that I have some 206...NOS 1"...two reels. cjacek was the one that spotted them awhile back and urged me to pick them up for my MM-1000 and the more I read the more glad I am that I heeded his advice. I don't remember what I paid for them but maybe like $50~60 for the pair shipped?

Thanks, Daniel!!

 

[fstrat76]

Hey...all this talk of 206 reminded me that I have some 206...NOS 1"...two reels. cjacek was the one that spotted them awhile back and urged me to pick them up for my MM-1000 and the more I read the more glad I am that I heeded his advice. I don't remember what I paid for them but maybe like $50~60 for the pair shipped?

Thanks, Daniel!!

I'd be interested to find out the differences you hear on your MM-1000.

Also, I'm a little confused about the re-bias procedure. I used an MRL 250nwb/m to initially calibrate. That's +6 that I calibrated to. So all my input and meter settings are 0VU for +6 SM911.

So after the bias adjustment, we do a Record Level adjustment and the instructions say (for SM911) "feed a -10dB (.316V) 400Hz signal to the line in and make sure the VU Meter reads 0VU".

But to do this for the Scotch 206, I should re-interpret that to be: "feed a -20dB 400Hz signal to the line in and make sure the VU Meter reads -10VU".

Correct?

 

[Beck]

So after the bias adjustment, we do a Record Level adjustment and the instructions say (for SM911) "feed a -10dB (.316V) 400Hz signal to the line in and make sure the VU Meter reads 0VU".

But to do this for the Scotch 206, I should re-interpret that to be: "feed a -20dB 400Hz signal to the line in and make sure the VU Meter reads -10VU".

Correct?

No, this is not correct. I'll be back later to shed some light on this, but I gotta run to my mom's house and fix a leaky sink drain. By the way 250 nWb/m is +3, not +6. BBL

 

[sweetbeats]

Right...250nWb/m is the equivalent of "+3". You don't want your 0VU to be the maximum operating level of the tape. SM911 is a +6 tape so your 0VU represents a 3dB buffer from the MOL of the tape.

As I said above, there is no reason to do a record level adjustment when you use the 206, unless you are stuck on having 0VU represent "+0" (reflecting the 3dB buffer from the MOL of the +3 206 tape). If you are just experimenting just treat -3VU as 0VU when running the +3 tape of the machine is setup for +6 tape. If you settle on using the 206 long term then it might be time to recal the record level.

Make sense? Has nothing to do with rebiasing.

 

[fstrat76]

Right...250nWb/m is the equivalent of "+3". You don't want your 0VU to be the maximum operating level of the tape. SM911 is a +6 tape so your 0VU represents a 3dB buffer from the MOL of the tape.

As I said above, there is no reason to do a record level adjustment when you use the 206, unless you are stuck on having 0VU represent "+0" (reflecting the 3dB buffer from the MOL of the +3 206 tape). If you are just experimenting just treat -3VU as 0VU when running the +3 tape of the machine is setup for +6 tape. If you settle on using the 206 long term then it might be time to recal the record level.

Make sense? Has nothing to do with rebiasing.

Makes sense, sort of. As Beck stated above, 250 nWb/m is +3. I got that. In the Tascam 42 manual it says use the cal tape MRL 21J205 which is 250 nWb/m. Got it. Used it. Calibrated with it.

OK, so I get that I do not have to re-adjust the record level after re-bias. And since I use the LF modulation method, I don't even need to worry about whether its +6 or +3 since I am adjusting for the lowest modulation noise by ear anyway.

But SM911 = 456 = what Tascam says to use. Those are +6. So in the maintenance procedures, all the adjustments are for setting up that type of tape, yet the 250 nWb/m cal tape is used for calibration. I guess that's where my confusion lies.

So its that 3db buffer that's the difference?

So really 0VU, with my current setup using SM911, is really outputting +3, or 3db under the tape's MOL of +6.

Yes? Or am I still in left field?

 

[sweetbeats]

No you've got it.

The standard calibration level for a given tape tends to be 3dB BELOW the tape's Maximum Operating Level (or MOL...the +3, +6, +9 rating of a tape). The MOL of a tape is the level at which the tape reaches 3% distortion.

So we set 0VU to be 3dB's below that MOL which is why the standard calibration level (0VU) for a "+6" tape is actually "+3" which is 250nWb/m.

Beck, among others, helped me to finally get that into my head.

 

[fstrat76]

No you've got it.

The standard calibration level for a given tape tends to be 3dB BELOW the tape's Maximum Operating Level (or MOL...the +3, +6, +9 rating of a tape). The MOL of a tape is the level at which the tape reaches 3% distortion.

So we set 0VU to be 3dB's below that MOL which is why the standard calibration level (0VU) for a "+6" tape is actually "+3" which is 250nWb/m.

Beck, among others, helped me to finally get that into my head.

Got it! And now I understand why it is much harder to work with +9 tapes on decks like the Tascam 38 and 42. You can really be pushing the electronics trying to calibrate and saturate for these tapes.

Now onto actually working with different tapes.

First I'm going to work with the 206. Eventually, once I get a better RMS meter (they are pretty pricey, even on fleabay), then I can then scientifically test. Maybe there's some software I can find to measure these things. I'm interested in knowing the frequency curves eventually but most importantly its how its going to sound to my ears that's the important thing.

I also want to do some ear testing with the BASF LGS35 and LP35. I'm not sure of the MOL on those. I'm guessing its +0 or +1 for the LGS35 and +3 for the LP35.

I have the coercivity numbers and such, but those charts don't show the MOL. Where can I get MOL numbers of various tapes?