cgecastro 05-18-2015 08:22 AM Test tape for Akai

Hello, A lot of doubts and a lot more of doubts I want to calibrate the playback level of my GX-220D (not that i need to by i have a little OCD), for this Akai recomends a test tape with a 250Hz tone at 7 1/2 ips, then adjusting the line out level to 1.228V rms (+4dbu) and after this adjust the meters to 0 VU.

This is all pretty straight forward, the problems are: What is the refference flux I should use? 185 nWb/m or 250 nWb/m I cannot find tape with this frequency, i found from supplier www.pievox.de 185 nWb/m 700Hz Ampex (dolby) standard and 250 nWb/m 1000Hz NAB or IEC They recomended 250 nWb/m NAB, and i would like to know what do i have to do to make a successfull calibration. Can I use a 1000Hz tape insted of a 250Hz one what standard eq should I use. If I get the 250nWb tape and want to calibrate for 185 nWb do I run the output 3db hotter at 1.734V rms and adjust the VU meter to +3dB? Or am i getting all this wrong!? They also recomend for the recording adjustment to use FUJI S-100 tape but i cannot find info on this tape anywhere

Sorry for the incoherent layout of ideas i'm not a native english speaker

johns82 05-18-2015 04:22 PM OK they say that but in your service manual what are the specs on the tape? If the deck is old the Pivox tape will only get you at the reference level, nothing more. I would recommend MRL 250 nWb at 1 kHz. Set up for .775 volt on the output with a 0 VU this will be 3 dB hot at 0. If you don't want that like you figure + 3dB on the meters and cheek the output for .775 volts at 0 dB. This will get you 185 nWb at 0 VU.

cgecastro 05-19-2015 12:21 AM There are no specs for the tApe on the service manual. The only refererence to a specific tape is for the recording calibration after playback reference to use fuji S-100 also the deck has a button labeled S.R.T. Wich stands for Super Range Tape and was manufactured. circa 1971

johns82 05-19-2015 05:14 AM Well changing the calibration as far as the calibration tape used is not a problem. As long as the specs given are meet the deck should perform. The specs I posted are a industry “standard” so it should be fine. The SRT switch is a equalization switch that simply boost the lower frequencies to match the record EQ for tapes more sensitive in high frequencies. The type of tape used to calibrate the record circuits is dependent on the type available, forget the Fuji tape unless you have a mountain of NOS laying around. I would calibrate the record to whatever tape you have abundant or New Stock like LPR 35. We can cover that later though but decide what tape you will do most of your recording with and stick to it. First is getting the calibration tape.

johns82 05-19-2015 05:17 AM Do you have a model/part number for that calibration tape? I might be able to cross reference it from my service manuals for other decks I have. Never mind, I just looked at the service manual. No part number at all. Well I guess we are left to our own devices! I also noted this deck has an amp so I would assume we are talking about you using this with a home stereo or other form of amplification. Use the RCA out for the calibration methods I described.

cgecastro 05-19-2015 08:56 AM The gx-220D has no amp, only the gx-220 has the amp. All the tape I have blank is 5 NOS reels of Capitol High Performance tape 2400 ft 0,5 mil Ref: CMP638A / C530-2410 http://www.tapeheads.net/picture.php...pictureid=2602

johns82 05-19-2015 05:31 PM Sorry about the mistake, was in a rush to get out the door! Do you have more then one? A lot of work to calibrate a deck for one tape. Case in example I set up my Teac A 6300 for Scotch 207 because I had a crap load of it, and it's a good tape. But just one oh no! I also set up the EQ switch for Scotch Classic and the bias on the split so I can use a mountain of that. But calibration for one tape will not be beneficial to do as more tape will become needed and you'll go thru that tape in no time.

cgecastro 05-19-2015 07:01 PM I think i have at least 5 reels of the capitol tape dont know if it suffers from SSS On a sidnote, discovered that the Fuji S-100 = akai 100L and that drives of that eea where mostly calibrated to Scotch 101, but what baffles me id why the 250Hz test frequency

johns82 05-19-2015 07:36 PM Yes that's almost as strange as Teac using 400 Hz or the old Ampex 700 Hz. The one thing I did notice since learning to calibrate deck is the benefit of the lower frequencies. These are not affected by the EQ play back adjustment. When a 1 kHz tone is used to set the play back calibration you adjust the EQ then you might have to go back and touch up the level adjustment and then the EQ again. Five tapes doesn't seem like an large amount for a calibration, but once you know how it's a simple matter of touching up for another formula. The tape you have doesn't suffer from SSS though and some of those tapes sound good. Being 1/2 mill you should keep the record level down to avoid print thru. I have some BASF tapes on seven inch reels that is 2400' but are 3/4 mill base. Some would assume it wouldn't take a hot signal but is capable of 6 dB without distortion or saturation. Shame I have five unopened and went to 10 1/2 inch decks. I really like them for seven inch decks, get a lot of time for the smaller reels. Thing is it takes so damn long to fill a 1 mill 10 1/2“ tape!

cgecastro 05-21-2015 04:56 AM I don't intend to record nothing right know, I just want to have a properly calibrated playback section

johns82 05-21-2015 05:22 AM Well that's simple. Most of your tapes you have are probably recorded using 185 nWb so that should be the base of calibration. I think your deck would be best suited for a 200 nWb setup, best of both worlds. I would get a MRL tape as it has the multi frequency tones and this will get your playback EQ set up. The difference on the playback level will be negligible and only affect the meter level in all reality. the output will be a little lower but not enough to loose any sleep over. Page 8 of this publication on there sight gives the info needed.http://home.comcast.net/~mrltapes/choo&u.pdf It looks as though 200 nWb at 1 kHz will get about 1 1/4 dB hot over 185/700. This amount's to no worries.

cgecastro 05-21-2015 05:08 PM Playback eq? Is it adjustable? Probably not on this machine. How do I find out? Or do you mean some kind of outboard eq?

dutch_frank 05-21-2015 11:22 PM No, both playback eq and recording eq are not adjustable on this machine. You can adjust the playback level, the VU meter readout, the recording level and the bias. Only the huge GX-400D has adjustable playback and recording eq. Akai kept it simple…

johns82 05-22-2015 05:52 AM Wow guess I should have looked a little closer on the service manual! Thanks Frank for catching that! Then the circuitry is closer to my 250 D, I figured out how to make it adjustable but it ain't worth the effort. Sorry cgecastro for the mistake! Hell I have a pivox tape for the 185 nWb @ 700 Hz, pm me and we'll get it to you for a minimal charge. Since it looks as though your not adjustable on EQ and I don't need this tape anymore it should do nicely!