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Author Topic: Tape format's / Tape Machines's bandwidth  (Read 7372 times)

Offline GY888

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Tape format's / Tape Machines's bandwidth
« on: August 27, 2007, 10:29:27 PM »
I'm new here in this forum, but after the Magico's at CES show using the Tape Machine, I have to take a study about it.  The sound was stunning, I believe, they wouldn't have had a good show without it.

So, what is the bandwidth on this tape machines ??  For example, SACD = 100 kHz and CD = 22 kHz

Offline docb

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Re: Tape format's / Tape Machines's bandwidth
« Reply #1 on: August 28, 2007, 09:48:50 AM »
Unfortunately I don't have published measurements as I have been redoing my lab setup and I'm without some of the necessary gear for a detailed test at the moment. With the Flux Magnetics extended response head (which is designed to give bottom end response at 30ips of -3dB at 20Hz) I would say the max would be maybe 20Hz to 30kHz at 15 ips. 30Hz-30kHz is the advertised response of a stock RS1500. It has heads that are compromised in length to better accommodate 7.5 ips playback as well as 15 ips playback.


The Flux Magnetics extended response playback head - on the left - should get quite a bit lower because the bands are much longer on the extended response head than on the stock head - right - to better optimize it for 15ips playback. It will of course still play 7.5ips as well.

These figures would apply pretty well to most tape machines of similar vintage, like the Otari MX-5050. Older machines like the tube output Ampex decks have heads with more limited top end. An old 300 or a consumer type 900 series machine with stock heads might only get to 12K or 15K on top.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline GY888

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Re: Tape format's / Tape Machines's bandwidth
« Reply #2 on: August 28, 2007, 06:27:42 PM »
Unfortunately I don't have published measurements as I have been redoing my lab setup and I'm without some of the necessary gear for a detailed test at the moment. With the Flux Magnetics extended response head (which is designed to give bottom end response at 30ips of -3dB at 20Hz) I would say the max would be maybe 20Hz to 30kHz at 15 ips. 30Hz-30kHz is the advertised response of a stock RS1500. It has heads that are compromised in length to better accommodate 7.5 ips playback as well as 15 ips playback...........These figures would apply pretty well to most tape machines of similar vintage, like the Otari MX-5050. Older machines like the tube output Ampex decks have heads with more limited top end. An old 300 or a consumer type 900 series machine with stock heads might only get to 12K or 15K on top.
So would say that the best case scenario would around 35kHz (-3dB) ??   How about its dynamic range, dB ??

Offline docb

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Re: Tape format's / Tape Machines's bandwidth
« Reply #3 on: August 28, 2007, 10:55:12 PM »
Assuming that the tape machine and its electronics are in proper operating condition, the dynamic range is determined by the tape formulation used. The dynamic range is defined as the Maximum Output Level/Bias Noise (MOL/BN). We are using RMGI SM 468 tape for Tape Project albums. RMGI SM 468 is rated at 74.5dB dynamic range for 15 ips at a head gap of 3um and 320 nWb/m reference level, using IEC 94 A-weighted bias noise index. Here's a link to a PDF of the spec:

http://www.rmgi-usa.com/pdf/RMGI_SM_468.pdf
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline mikel

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Re: Tape format's / Tape Machines's bandwidth
« Reply #4 on: August 29, 2007, 07:18:25 AM »
as a tape newbie i have been 'google'ing' up a storm attempting to learn about all this 'tape' stuff. it's like an onion; there is always another layer.

i did come across an interesting article regarding bandwidth of particular pro audio tape machines that may be helpful....here is a link.

http://www.endino.com/graphs/

it may be old news.....but maybe not.
Mike Lavigne

Offline scully280

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Re: Tape format's / Tape Machines's bandwidth
« Reply #5 on: August 29, 2007, 08:06:29 AM »
Not very old news, but it is a very convenient site that kind of pulls a number of things together.  The low end has always been a problem, and it's not clear to me whether it's more of a problem on the play side or the record side.  That might not seem like it matters much because it's just there and you can't do much about it, but my guess is that it's really hard on guys who in the mastering business as they get tapes recorded on all kinds of different machines.  That's why I'm glad for the spacing of the frequencies of the low tones on the Tape Project test tape.  With the Tape Project tape and the slightly different tones on the MRL test tape we'll be better able to characterize our tape deck's various low end responses.  This brings to mind a question for docb.  Does the tape path change in the Tape Project's RS-1500's alter the tape to head geometry enough to have an effect on low-frequency response, or is low-end response more strongly correlated to the width of the reproduce head pole pieces?

Thanks,
Rich
Richard Lane
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Offline docb

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Re: Tape format's / Tape Machines's bandwidth
« Reply #6 on: August 29, 2007, 11:15:21 AM »
I'm working on setting up a couple of machines, one with each kind of head, later this week, and I'll try to give you something concrete in terms of numbers. My subjective experience is that even if there is some  compromise on the low end because of a slightly different wrap over the head (although actually I don't think there is much of a change) it is more than offset by the overall improvements to the sound in terms of resolution and stability.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline scully280

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Re: Tape format's / Tape Machines's bandwidth
« Reply #7 on: August 29, 2007, 08:44:44 PM »
docb, I appreciate the information.  I'm wondering if the revised tape wrap's main benefit is reducing scrape flutter.  By the way if anybody wants to hear scrape flutter just record a 10KHz sine wave and A/B input to tape output.  The pure tone turns to grungy fuzz.   Scrape flutter is hard to quantify because it's a random frequency modulation of a pure tone that's caused by friction of the tape over the entire tape path.  Some older decks had small rollers in between heads in an attempt to isolate the tape over both the record and play head, and some of these designs were somewhat successful.  I'm guessing that scrape flutter also smears high frequency transients that will tend to dull the sound and reduce image focus.  Doc, have you done any before and after on just pure tones on your path mods?
Richard Lane
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Offline Danny Kaey

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Re: Tape format's / Tape Machines's bandwidth
« Reply #8 on: August 31, 2007, 08:56:55 PM »
according to Tim d.P., his custom electronics outfitted Technics 1500 has the following specs:

15ips 80db s/n relative to max. operating level w/ 911; 15-36k +1, -3db (40k -4db)
3 3/4ips 4-20k +1, -3db

this is all based on stock heads of course...

D.

If all goes as planned, we will have 2 rooms w/ Technics machines @ RMAF: Dan @ EAR; Zu w/ my personal
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Offline docb

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Re: Tape format's / Tape Machines's bandwidth
« Reply #9 on: September 01, 2007, 02:06:00 PM »
Quote
I'm wondering if the revised tape wrap's main benefit is reducing scrape flutter.

The mod is indeed intended to reduce scrape flutter. But I wouldn't say that this is done by attempting to revise the tape wrap. The head wrap may happen to change a wee bit because of the removal of the fixed tape guides, but the main thrust of the change is to reduce friction by removing the fixed guides on the headblock and sleeving the remaining fixed guides with Teflon, then dialing in the guide alignment as tightly as possible. Our comparisons have been done with music, but I have not run sine waves and listened. It was actually quite a bit more obvious an improvement than I thought it would be with a music source.
Dan "Doc B." Schmalle
President for Life, Bottlehead Corp.
Managing Director - retired, The Tape Project

Offline sue22corc

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ampex 960
« Reply #10 on: July 01, 2008, 09:16:59 AM »
We have a working Ampex model 960 4 track recorder and player.  Any advice on how much this thing is worth and where I could sell it without getting ripped off?  Also have a box of recordings previous owner made (Miles Davis and such).  Thoughts?
Sue