Tascam 388 - bias & calibration issues

dustblow

New member
I hope we all sort this out one last time :) I've read almost everything here, on the tape-op gearslutz and other sites about calibrating the 388. But even with 10+ hours reading and noting, and official manual in my hands I can't get right some things... Let's start with that I bought LPR35 tape which looks like its +6dB tape and 250-specs. Unit is cleaned and degaussed.


I did test repro/playback with 400hz at -10dB / 0,316V RMS) and fader set to gray area (7-8) so the meter was reading ZERO. I played it back and had results like +/- 1dB in all channels except channel one (but later on that). Some are -1, some are +1, etc. Is that OK? Some of you here suggest that it should be -3dB after playback, but why? This is my first question. I want to record loudest possible to avoid excessive noise. Background noise is unacceptable and seeing some YouTube video on recording, my 388 is MUCH noiser that exampled I heard...

2. I'm alittle bit confused about biasing 388. I;ve read a lot about it here, and it seems that tape is not needed for that process. Turns out to be super simple then - it must be a fixed value for specific type of tape, right? Just put the 12,5k signal and measure between test points and set "given" value. Does anybody know these values for different tapes - in my case, the LPR35? :wtf: Here's the manual that is not helping me with it too - it says, on the 1-5-3 "connect DV voltmeter between TP01 and TP11 (TP02-TP12, TP03-TP13 etc) to obtain minimum reading on the meter". now STOP. I've tried to do it like million times and found out that counterclokwise turning bias pot = bias is constant raising... and clockwise turning bias pot = bias rising!!! So the "minimum" reading as the manual suggests is a value when bias is not near zero (not possible to do), it's just some value when it does not raise. In my case, the four points were between 0,25-0,31V. Ahh.. that manual.. not well written! Note it for your further calibration. WIll save you some time. BUT then in 1-5-4 "recording bias adjustments" it says that I should do 150mv between TPG (ground) and TP2. OKay I see that point on each channel, so 8 measurements can be made. But with the recording on, or off I get 0,00V on the test points. I have even tried to set meter to DC but no way.. still ZERO. What I'm doing wrong, is it another Tascam manual mistake? Should I play a calibration tape here (not mentioned in the manual)?



And the last thing, maybe simple but important:

3. The recording/playback. I'm a bit confused here. I put the mics on the XLRs, set all the faders to the gray area, set the trim to a nice (0 and up) values,EQ flat, arm channels 1-2, 3-4, 5-6, 7-8 + even/odd pan, arm all 8 tracks and record. Then rewind,m unarm tracks and press play. It's a lot of noise. What I'm doing wrong? I think I did one time playback that it was super loud and not noisy but I can't reall what I've done and can't repeat that again.. Should I use L/R switches somehwere or switch to RMX from MIC on each channels? What is the correct procedure?


Ufff..

Greg
 
Sit tight, Greg. I’ll respond in detail as soon as I can. Others feel free to chime in in the meantime. Folks, Greg reached out to me initially by PM and I asked him to post a new thread which he did and it looks like he’s doing his best to utilize the manual and just wants to do right by his machine. Let’s help him out! :)

Stay tuned.
 
Sit tight, Greg. I’ll respond in detail as soon as I can. Others feel free to chime in in the meantime. Folks, Greg reached out to me initially by PM and I asked him to post a new thread which he did and it looks like he’s doing his best to utilize the manual and just wants to do right by his machine. Let’s help him out! :)

Stay tuned.

Thanks sweetbeats! I forgot to intruduce myself and say Hi, sorry about that...! I'm quite in a hurry to set up 388 because the recording will take place in 4 weeks from now. If I (or we all!) make all those steps right to calibrate it I can even write a manual how to properly bias, setup and calibrate 388 with no special tools, only computer & multimeter. That will help a lot of people I think..
 
Thanks sweetbeats! I forgot to intruduce myself and say Hi, sorry about that...! I'm quite in a hurry to set up 388 because the recording will take place in 4 weeks from now. If I (or we all!) make all those steps right to calibrate it I can even write a manual how to properly bias, setup and calibrate 388 with no special tools, only computer & multimeter. That will help a lot of people I think..
Man these abandoned threads kill me. I'm currently learning about Biasing so I can do my machine now that Maxell 35 90 is drying up, and i'll be swapping between my stock of that and RTM LPR35 as I make the transition. So I need to get it down so I can set it up for the LPR.

Reading through this and the manual and long term i'd love to learn how to run through the whole maintenance section and all the equipment i'd actually need in the computer age (I imagine I could use my laptop as a signal generator etc) but before that i'd love to just get across biasing.

My main question for now is;
- I understand that to bias, you connect an AC Voltmeter between test points TP2 & TP G on the REC / PLAY cards under the top lid for each channel group (1,5 - 2, 6 etc). You adjust the bias pots to read150 mV from this test point. This is in Record mode. So from that, it reads as if you dont actually have the tape running, but you obviously would. Am I right to say you have the deck recording, but there's no test tone being recorded in, it's just the tape recording zero input?

- by this measure, is there any listing of mV for different tape formulations? I imagine 150mV would be for 457 or maxell 35 90

- would I be better to do a record / play / adjust with a 12.5hz test tone?

Also, looking at getting this multimeter to measure the mV for the tape. Goes down to 60mV and autoranges up to 600 so should do it, right?

 
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