Guest Posted August 28, 2020 Share Posted August 28, 2020 (edited) Hi Fellas I recently acquired a lovely minty Akai GX630D from a fellow forum member (top guy - thanks @rsc400sa) and have been putting it through its paces. One thing that's been killing me is whether to record at 3.75ips or 7.5ips. I'll be using brand new RTM SM900 and LPR90 tape, I don't intend on ever buying commercially recorded tapes. After a lot of reading online, some say don't ever record at 3.75ips, they say it sounds appalling. Whilst that might be true with some cheaply made commercial tapes, I'm finding that recordings done @ 3.75ips to actually be quite respectable, and certainly very listenable. The main difference to my ears is a far less responsive top end and a bit more tape hiss. The nerd inside of me just couldn't let go of wanting to know what the actual differences were though, so I decided to get a little more scientific about it. To do so, I downloaded an app for my computer that outputs test tones at any set frequency. I outputted this to my preamp via its built in Dac (McIntosh C2600) which provided audio to the tape deck via the Mac's analog line outs. I set a test tone at multiple frequencies and set the inputs on the Akai until it read 0dB on the VU meters. I started the tape, then flipped over to the monitor (play head) and took the measurement on the VU. Not entirely scientific I know, but the results pretty much speak for themselves.... Monitoring via headphones. Here's what I saw - 7.5ips dropoff 3.75ips dropoff 1khz 0dB -1dB 3khz -1dB -1dB 5khz -1dB -1dB 7khz -1dB -1dB 9khz -1dB -2dB 10khz -1dB -3dB 11khz -1dB -5dB 12khz -1dB -7dB 13khz -1dB -10dB 14khz -1dB -20dB 15khz -1.5dB Offscale Low 16khz -2.0dB Offscale Low So the "specs" of the device are a little misleading. They quote a frequency "response" of 40hz - 25kHz @ 7.5ips and 30hz-18Khz @ 3.75ips. I guess what they don't tell you is what that actual response is. -20+dB is not response.. Anyway what does this mean.. The regular Joe - I can't hear any difference. The critical music listener - A rolloff in the high frequencies is definitely audible at 3.75ips, but not so much that it hurts most music. High frequency synths (the reason I picked Jarre's Equinoxe) will be effected so if you really like "sharp" music, you'll notice it. Tape hiss is more evident but not really that bad, not so bad you'd really notice unless played at high volumes and even then only between the tracks or during quiet passages. The Audiophile type who argues PCM vs DSD - Knowing the response craters @ 10Khz+ will kill you. Get ready to consume tape, even if this format is for you, which it probably isn't. 7.5ips is better, but 3.75ips is not as bad as many make it out to be, some people in fact may like the "warming" effect of 3.75ips. My hearing is obviously terrible. I could barely make out the test tones above 14Khz, and it certainly wouldn't make much, if any difference to audible music at these frequencies and above. What happens between 10khz and 14khz is certainly audible and was what I could hear through my headphones, a "warming" of Jarre's synths by rolling off the highs. I'm the third guy, so I'll be recording everything @ 7.5ips. I like things to sound as they're recorded. Anyway chaps thought you might be interested. I know it's not entirely scientific but the numbers don't lie and they are consistent with what my ears are telling me. I'm going to get an external DBX unit for it which will boost treble response as well as eliminate tape hiss. Let's see how we get on after that is introduced into the chain. I hear good things about them, and they can be had very cheaply. Maybe I won't have to consume all that tape after all... Edited August 28, 2020 by Guest Link to comment Share on other sites More sharing options...
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