Barely Any Treble

[Ink N. Face]

I know that this is similar to another thread right below this one, but I don't think it's quite the same thing (I don't know much about analogue recording, so I wouldn't be surprised if I was wrong.). I want to get my Akai 4000DS sounding as good as possible, so I ran a CD I made with 40 Hz, 100Hz, 1kHz, 10kHz, 14kHz tones on it through a mixer plugged into my tape recorder. One at a time, I played the tone and set my tape recorder to record at 0 dB, then I hit record.

When I played back the tape, the 100Hz tone was one dB louder than I had recorded it at, but the 40Hz tone was 4.5 dB quieter, the 1kHz just the same, the 10kHz 8dB quieter, and the 14kHz 15dB quieter. Plus, similar to the other thread I mentioned, all the frequencies but the 100Hz tone have flutter, just a little bit if it's close to 100Hz, but progressively more the further it gets from 100Hz (The 14kHz tone has quite a bit.). On second thought, I think that might just be mixer or tape noise because the recorded signal is so quiet. I'd like everything to be at zero. Is that even possible with such a low end machine?

Is this possibly because of the tape? It is a Maxell that looks pretty old and has been recorded over tons of times by me, I'm sure tons before I got it. If it's not just the tape, does anyone know how I could fix the problem? The machine specifications say the tape records up to 20kHz at 7 1/2" (the speed I use), but I've got a feeling that it wouldn't even pick up that high at all.

In the manual, it says how to do something to adjust frequency response, but I can't find any place on the tape recorder that matches the picture. I think my heads are pretty clean. I can post a picture of them if that will help. Thanks in advance for everyone's help.

[jjones1700]

I'm just guessing here, since I can't see the machine itself. I'd venture to guess it's either an alignment issue or dirty heads. Using a worn out tape might have something to do with it. The falloff on the high end makes me suspicious though. I'll let the pros chime in on this though.

[Tim Gillett]

Even when adjusted perfectly the machine will probably not handle those tones at 0db VU, specially the ones above 1khz. When we do a frequency response check on such a machine we normally record the tones at -10db or even -20db. That's standard procedure.
Record the tones at the lower levels and even if it's not perfect it will be a lot flatter than what you got.

Cheers Tim

[Beck]

Rule number 1:

Test your machine with a brand new tape. Only then will you have an accurate picture of where your machine is alignment wise.

Your 4000DS should have a frequency response of 30 Hz to 22 kHz +/- 3 dB @ 7.5 ips, reference 0 VU. This means that with 1 kHz spot on @ 0, no frequency should drop below 3 dB or above 3 dB upon playback. As Tim pointed out the response will be even better when measured at -10 or -20 VU.

Your highs are falling way to low. It could be the tape and/or alignment, including too high a bias setting for the tape. And of course dirty heads, which JJones already mentioned.

Get a new tape and start from there. Maxell is good stuff, so you can buy new-old-stock (NOS) with no worries as long as it's sealed in the box so you know for sure it hasn't been used. And clean those tape heads with a cotton swab and at least 91% Isopropyl alcohol, available at your local Walgreen’s or other pharmacy.

Tapes to look for:
Maxell UD 35-90
Maxell XLI 35-90
Quantegy 407
RMGI LPR35

[Ink N. Face]

Thanks for everyone's help. I'll get some new tape pretty soon. I looked at the heads under a light and they are a lot dirtier than I thought, so that probably has a lot to do with it. But mainly jus on the outer edges, which I'm guessing isn't where the actual erasing/recording/playback takes place, but I figured that that will push the tape away from the heads a bit. Am I right about this?

Also, is there a more abrasive way to clean heads that won't damage them? Q-Tips and alchohol aren't working well enough.

[sweetbeats]

I looked at the heads under a light and they are a lot dirtier than I thought, so that probably has a lot to do with it. But mainly jus on the outer edges, which I'm guessing isn't where the actual erasing/recording/playback takes place, but I figured that that will push the tape away from the heads a bit. Am I right about this?

Yes and no...the record path on those outer tracks goes out close to the edge...that dirt is a problem for sure.

Also, is there a more abrasive way to clean heads that won't damage them? Q-Tips and alchohol aren't working well enough.

1. Try 100% cotton makeup remover pads from your local pharmacy/department store...the kind that look kinda quilty. They will allow you to get into the nooks better, hold more cleaning agent and you can apply more pressure and elbow grease. Don't use anything more abrasive than a cotton pad or swab!
2. Are you using at least 91% isopropyl alcohol? 50% and/or 70% are not recommended and naturally less effective. You may also want to try good quality denatured alcohol. Might work better in this situation if 91%+ iso alcohol doesn't do the trick. Denatured alcohol is a good option and even preferred by some.