For the sake of discussion, pertaining to the 388 specifically, I'm reposting a bit from a thread where Cory/"Sweetbeats" wrote
about what would be necessary to run high bias tape on that particular deck.
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Bias, +3, +6,...+9 "hotter" tape, tape compression, cleaner vs warmer...etc.etc..as it applies to the 388
Just thinking out loud here with hypotheticals, and trying to get the facts straight as far as what would be required for running high bias modern tape on the 388.
Thin 1800 foot tape would be out because of the higher output and print through issues, so a thicker backing would be needed.
Thicker, stiffer tape would be harder on the motors and heads. However, 456 is used by many on their 388 without issue. How much thicker and stiffer is high performance tape like GP9? Any high bias 1/4" formulas known for their supple transport travel?
Also, would the stock cards be adjustable enough to handle the signal? Are the 388’s electronics capable of being set to accept the levels and biasing for such high performance tape?
These things I ponder:
456 is used by many on their 388 without issue. Is it the same thickness and stiffness as high performance tape like GP9?
GP9 is about 0.2mil thicker (456 = 1.93mil total, GP9 2.13mil)
Would the stock cards be adjustable enough to handle the signal? Are the 388’s electronics capable of being set to accept the levels and biasing for such high performance tape?
sweetbeats of homerecording said:
Ultimately you'd have to try it out, but here is what I am pretty sure you will find:
* That the bias amps are either not robust enough to pump the bias level, or at the very least you'd need to mod the bias cards to allow more current which is what is necessary in the likes of the 58 and MS16 systems...not sure about later decks. I would be really surprised if the 388 bias amps had enough headroom to bias "+9" tape, and if they do there is always the question as to whether or not you are going to damage something by running it at that constantly. Think of a car...yeah the tach in my old Subaru says I can wind the engine up to over 6,000rpm, but we all know if I drove it around like that all the time it would most certainly (and I believe drastically) reduce the life of the engine.
* Even if you could get the bias issue resolved (assuming there IS one), I betcha the R/P amps would be stretched before being able to take advantage of the headroom on +9 tape. I bet it would work, but there may be sonic artifacts that leave you going "was this worth it?" Remember, program peaks, especially on things like percussion, are WAYYY over the nominal level...that's why you see the peak LED's flickering and the VU needle is hardly pushing 0...those peak LED's typically light at +10 or +12. Now let's say you cal the deck using a 355nWb/m standard, now those same peaks will be at around +13~+15 maybe? That's getting up there. Not sure at what level the 388 R/P amps clip. The amps in my Ampex MM-1000 aren't rated to clip until +28 or +29 and I'm pretty sure the 388 amps aren't up in that range. If the goal is to get tape saturation then you want to leave enough headroom in the setup so you stay far away from overdriving the electronics.
YMMVyadayadablahblah.
I realize you are just thinking "out-loud" so I don't want to sound like I'm over-reacting to your musings, but the reality is that whatever discussions we have had on this forum over using +9 tape on any number of 1/2" 8-track decks from Tascam would certainly be more acute with the 388 since it is a transport very explicitly designed for "1.0mil" +6 tape. I just don't see the benefit of "going-there".
Somebody tell me if I've got it wrong...the only substantial reason to use "hotter" tape is to increase headroom to create greater sonic distance between the program level on tape and the noise floor...right? Tape formulations on +9 tapes may elicit a different or specific "flavor" but the whole hoo-hah about higher and higher output tapes is NOT because the tape in and of itself is "hotter" or "phatter" or "louder" or "dripping with tape 'compression'" or whatever...its just simply this:
The higher the tape rating (the consumer +3, +6, +9 figure), the more signal the tape can handle before presenting a industry standard distortion rating of 3%.
This means that the recorded material can be tracked "hotter" on that tape than a lower output level tape and still be "clean" and since the tape noise does not increase with a "hotter" tape you've just gained more distance between your program material and the tape noise.
So if low noise is an issue (i.e. tape hiss), then maybe +9 or greater tape is the solution. If you want crunchy-yummy tape distortion on a 388 then maybe 407 is the answer...print-through is an issue on thinner tape. 407 is a 1.0mil +3 tape which means you'll be able to drive the tape into distortion (hopefully nice yummy third-order harmonic distortion) while being more kind to your R/P amps AND while keeping print-through from being as much of an issue. YES you are closer to the tape noise floor but my guess is that if you (not YOU specifically , shed, but whoever is reading this) are wanting to push/saturate the tape you aren't tracking solo acoustic guitar...it is probably something with drums and electric instruments and I challenge you to hear the tape noise on properly biased 407 as the cymbals rage and the guitars crunch. Yes there are all levels of dynamics and tones in the music style I'm hinting at but I'm just trying make a point with that example.
No matter what, ANY machine and tape selection is going to be a process of compromises but if you are clear on what you are going for it should be obvious what tape to use and how to use the machine within its scope, and for most stuff I'm thinking LPR35/457 is ideal for the 388 and if it was high energy stuff I might even try using a LOWER output tape like 407.
Am I discouraging you from trying? I hope not. You might love the result and if that's the case more power to you...I'm just trying to make the point that the desired performance or result from the machine may be achieved in a much better way that seems backwards by being mindful of the tape selection and understanding what the numbers really mean. You might try GP9 and compare to to 407 and like the latter better because the deck itself isn't running at "7,000rpm" or even "5,000rpm" and the results you hear are the tape being pushed rather than the electronics.
Am I knocking folks who mod their decks to properly bias and drive higher output tape? Certainly not! I just know after going through all kinds of thoughts about "I wonder if..." and "I wonder what..." I came to realize that most of the time it wasn't worth the hassle when I considered all the unknown variables and when I came to understand the drivers behind the super-high output tapes, and when I came to understand what the numbers mean and how to use operating level to my advantage.
Know and understand your goal and the purpose behind it. Then choose the path to get there.
I'll use evm1024 (homerecording member) as an example...he's modding/modded the bias circuit on his Tascam 58 R/P cards to properly bias super-high output tape. This is a known solution to a known issue with those amp cards when using +9 tape...the bias amps can handle it but the (Ethan, correct me if I'm wrong here) feedback loop in the stock bias trimmer circuit provides for a trim window that, at best, just barely biases +9 tapes. In most cases it doesn't quite get there. The mod adjusts that window by raising the ceiling on the feedback loop so that the bias level trimmer can dial in more gain. This also means that that "window" may now be to high for lower output tapes because the low end of the trim range may now not be low enough, sending too much bias to low-output tapes. That's the compromise. But outside of that we know (by field-tested results and educated analysis that people like Ethan possess) that the bias amps are safe to produce that level on a routine basis. And WHY did he do it? Ethan has a focus on tracking acoustic instrumentation...classical compositions...he likes pipe organs too. These are sensitive sources that often leave tape noise exposed and can be problematic with nosie reduction. Higher output tape is the natural solution. The bottom line is that he's got a specific need to use hgher output tape and is educated and experienced in the area of electronics to be able to design the circuit level solutions.
Getting off the box now. And I CERTAINLY hope this doesn't feel like I'm lecturing you, shedshrine...What I'm saying is (hopefully) for the good of the order and I'm just sharing things that have come to settle in my mind as a result of the same kinds of thoughts and questions you are pondering and posting. So thanks for the question. I feel it is a really, really good and important topic.
Fantastic response and info Cory, and much appreciated. That clears up a big gap in my knowledge, and I’m sure helped out many others. I can remember Daniel "Cjacek" (homerecording) touting the thrills and joys of 407 all along, and I still went ahead and grabbed 15 reels of 457 upon Quantegy’s demise, because, hey man, it was the “hotter” tape.

Now I finally realize, in the case of the Tascam 388, it’s all about pushing +3 tape for maximizing tape compression, if that’s what you’re after, while minimizing any stress the 388’s electronics (or messing up the dbx tracking with obscene levels if it's on), and that
hotter tape just means a higher level clean signal before saturation/distortion. Big "aha!" moment..Many thanks!
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