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Thread: fluxivity and MOL as a function of tape speed?

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    fluxivity and MOL as a function of tape speed?

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    So let me get this right...my mind was wanering as it often does, and I started thinking about the benefits ans detriments of 30ips vs. 15ips...am I correct in that if you hit the tape with saturation-level at 15ips, would you then be below saturation level if you switched to 30ips because there would be more oxide to absorb the same level of flux at 30ips compared to 15ips?

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    I believe so, yes!

    You also decrease audible tape hiss another 10 db, (on average), double the high frequency response and lose the bottom octave of your bass response if the heads were only designed for 15 ips. You'll also wear the heads down twice as fast along with the guide-posts...but I'm sure you knew all that already!

    Cheers!

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    Yeah...i did know about all the other stuff, just never really concretely landed on the whole headroom thing.

    Jumping to 30ips can do ugly things to your response curve if the heads weren't designed for it.

    I'm just poking around at the idea since I may be getting access to a DC capstan motor for my MM-1000 which will open the possibility of 30ips and its good (in my mind anyway) to ponder the reasons and potential in trying it out...what to test, what to listen for, that sort of thing.

    The repro head is pretty wide, though not wide enough as far as I can tell to do a good job capturing those subsonic tones at 30ips...It'll be interesting to mess around with it at some point though and who knows? I may be surprised.

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    The other thing you might want to look at is how clean or not so clean the channel amp units of the MM1000 are. I remember looking at some s/n ratio specs on the 440 series and noting that the signal to noise specs were a bit on the low side compared to mid line TASCAM recorders like the 48 which were achieving 68 to 70 db s/n ratio specs without noise reduction while the 440 specs were at least 3 db worse, which is audible and cumulative, the more tracks you have.

    So the point of all this is to be concerned that even if you went up to 30 ips, your electronics might still be adding audible hash to the sound.

    Cheers!

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    I hear you...

    Thing is, I don't think the spec sheets are apples-to-apples between, say the 48 and the MM-1000/440. I had a 440B electronics module on the bench to test it, and granted my test only took the input amp into account as I was only monitoring the input through the module, but I had it connected to my beat-up M-308B and I was using an SM-57 and monitoring via headphones...I thought I had the mic channel open to the electronics module but I didn't. I was monitoring the return. I had the input and output knobs cranked up on the electronics module because I wasn't getting anything from the mic but the problem was that I forgot to turn the GROUP channel ON on the mixer. Anyway, there wasn't any noise to speak of at all and that shcoked me because I expected there would be a ton with an untouched original 40 year old 440 module but nope...and then like a dummy I realized the GROUP channel wasn't on and when I switched it on the road noise from the road a couple hundred yards away was deafening in the cans and I was in the enclosed shop. So I'll keep that in mind but who knows what'll happen with this system at 30ips...the electronics are rated to handle like +28dBu before clipping and with tape streaming by those wide-format heads at 30ips using 499...we'll see.

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    Another advantage of faster tape speed is more precise editing. Punch ins and outs are tighter.

    I think it's unliikely the record amp will be noisier than the tape noise itself. Any good transistorised electronics from the late 60's onwards was pretty quiet compared to the analog tape noise. This is the perhaps uncomfortable truth, not about analog per se but about analog recording methods.

    How could it be that the record elecronics from a 40 year old tape machine can have better noise/distortion/dynamic range performance than the latest and best analog tape stock from 2009? Both are analog systems but the analog recording system cannot match the analog record amp that is driving it.
    BTW at 30 ips with modern tape the potential high frequency limit is probably in the hundreds of kilocycles, although in practice bcause of head limitations it will be much lower than that. But it also demonstrates just how wasteful of data bits is the analog audio tape system when using high tape speeds.

    15ips and 30ips were used partly for better editing and partly to reduce tape noise but there's a law of diminishing returns here.

    Maybe food for thought.

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    My only open reel decks are in the Tascam 22 family (a couple of 2-tracks and a 4-track), which were all made for tapes like Ampex 407 (+3).

    I can say that using a tape like Scotch 207 (also +3) sounds great at 15 IPS. Switching to 7.5 sounds bad. On the other hand, LPR35 (+6) sounds better to me at 7.5 than 15. Like at 15 IPS, the Tascam electronics distort before there is any saturation. 7.5 IPS on the LPR35 seems right.

    Just my subjective observation, but it supports what you are saying.

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    Tim, thanks...yeah I was thinking that it is a truncated thought to exclude the rest of the system when considering noise (i.e. looking only at the amp electronics)...the thing I'm finding with the Ampex stuff I have in the 440 and MM-1000 family is that the PSU's produced really clean power and I have to theorize that that can't but help with noise in the audio circuits downstream. I'm just really excited about these old electronics units.

    I have a feeling that when up and running I will mostly or entirely focus on utilizing 15ips...cheaper and I'm anticipating that I'll miss the LF bump at 30ips...all just silly daydreamy stuff right now though which is pretty much all the good this thread is!

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    I think 30 ips really has more of a rightful place in stereo mastering where you want to "bark up", to borrow a military term. And following that logic, if you were multi-tracking at 30, then you should most certainly want to master at 60!

    Cheers!

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    heheheh...that's where them 14" reels would come in handy...

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