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4 track calibration demonstrated on a Tascam 244 Portastudio
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- čas přidán 31. 10. 2019
- Here are the steps I take to calibrate the audio path on a four track cassette recorder. i'm using a Tascam 244 but steps are roughly the same for any such machine...if its got digital meters it may not be possible to do that step, the variable resistors you'll find on the printed circuit boards should be labelled ot give oyu a clue of what does what, even if you don't have the service manual or schematics for the unit you are maintaining.
I calibrate in this order;-
Meters
playback levels
tape speed
record levels
Listen for wow flutter and other pitch issues which might point to a worn-out motor
So you can easily scrub to the different bits theres a label in the top left of the screen.
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TETRAKAN - Fix & Use Tape Recorders
Overviews; tear-downs; repair vlogs; techniques; tutorials; demo recordings...
...covering every cassette multitrack recorder ever made!*
*(eventually)
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I prefer to answer questions in the youtube comments where my answers can help more than one person, but if you need to share photos etc, you can message me via facebook.
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Tools and equipment I use when repairing portastudios;-
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This is so good! Thank you for taking the time to make these videos. What a fantastic resource! Keep up the good work!
Awesome video you're a saint for providing the only documentation for this stuff.
I'm gonna try that on a 244... many thanks for this vidéo ! So helpful :)
As an alternative to your frequency counter I actually used a tuner on a Zoom guitar stompbox. I bought a tape with a 440 Hz signal, so I could tune the Tascam untill I had a solid A showing up on the stompbox. This also worked for the high (double) speed changing it to 880Hz, offcourse also showing as an A, though an octave higher. I verified it afterwards with a professional wow & flutter meter, and it turned out to be spot on.
Good call, providing you can do obtain a tape which plays at a pitch recognised by a tuner. I've recorded a C or another pitch at the beginning of a song to make sure playback speed would be the same if I ever took it to another 4track, then used a tuner and the pitch control to check playback speed is the same on the second machine.
Tetrakan Supermonobloc You can buy new test tapes of which the first 2 minutes are 440 Hz, and the following 16 minutes are at 31500 Hz. They’ll cost you about €20.
Welcome back!!!
hello tetrakan, do you think there is a way to regulate the input signal level on a tascam 414 because mine have one channel (the third) that have a very high input signal compared to the others at the same potentiometer position... thnaks for your work!
Hey, there are electrolytic capacitors coupling the preamp to the jack socket and the rest of the circuit. If those leak slightly it can cause issues with levels noise distortion etc. If replacing those doesn't do the trick, very occasionally I've needed to replace the 8 pin opamp chip itself, replacements can be had for not much money.
When playing back tape to adjust the record levels, should the record function be set to Safe or 4Ch REC mode? It seems like safe mode is always quieter on these machines...
I’ve noticed that inconsistency too. I err on using safe mode, just because that is mainly how my portastudios are used - tracking mono overdubs. If I ever had a 244 which I was mainly using to track a drum kit with 4 mics recorded simultaneously before dumping the results into the digital domain (for instance) I’d make the calibration for 4ch REC mode. I figure that ultimately we’re trying to get a signal in a sweet spot between the noise floor and the point where clipping or saturation occurs, so with the dynamic range being I think something like 60dB with DBX on (citations needed?) then a couple of dB discrepancy between the two results you’d get depending how you set the unit during calibration won’t render the other setting unusable.
Thanks for uploading all these videos! I’m wondering if you know why 2 channels might not be recording on my 244? Channel 2 and 3 don’t seem to want to record at all, or at least I can’t record or playback those two. I’ve tried changing the head.
You're going to need to do so.e audio probing to figure out where the signal is cutting off. Too complex to describe in a comment but I have several videos on the subject, probably the most relevant to ypu is this one czcams.com/video/O-_fQZNG-zg/video.htmlsi=GzIncHTbCe7P2HUF
@@Tetrakan that’s very helpful, thanks a lot
Do you think i could fix a slow warble on one of my channels (ch 1 actually) by doing what you did with the variable resistors? Ive tried different tapes and cleaned the heads... i still get same subtle fluctuationon that channel and that channel only. Like a cartoon car going over rolling hills lol. Or maybe you can point me in the right direction. Thanks in advance!
J.
Sounds like the edge of the tape closest to track 1 is rubbing against something, probably the metal guides which protrude from the magnetic heads. The conbstant curling and uncurling of one edge of the tape will manifest as a change on pitch only on track 1 or 4, depending which edge is rubbing. You would resolve this by adjusting the screws which attach the heads to the transport, similat ro an azimuth adjustment as described in the service manual.
Hi , how are you? Can i Ask you which cassette should i buy for the calibration of the Tascam 244? i went to the gennlab site but there are many types and i can't figure out which one to get. Thanks
MXT-112. 3-3/4 ips 315Hz 3180+70usec 0dB is the one you want for level.calibration. it can also be used for motor speed.
Tetrakan, Do you know of anyone in the US willing to put the amount of work into calibrating a 244 as you do? Thing is, I have a 244 that I had Teac (when they were still around like 15 years ago) re bias for some NAC tape that ended up being unreliable. I'd like to have it freshly re biased for Maxell XLII's. And of course aligned electrocially. I guess I'll probably have to do it myself, as I'm not confident I can find someone who knows these machines that can do these procedures and have the correct alignment tape to do it with.l Thanks very much for the calibration video. I'm handy at doing all this on an Ampex, but 244 is a bundle of wires.
recursive delete in POrtland or mOds and sods in upstate new york might do that. As you may know i'm mostly self taught and Bias adjustments are one of the least well documented aspacts of these units. Do you know what changes were made to your 244? Because if its justb a matter of changing the frequency or amplitude of the oscillator its not that hard to do.
Hey! I have two questions:
1. Is there difference between calibrating levels with and without dbx? I have dbx off (and want to stay that way).
2. Could you provide a list with tools needed to perform calibration? Multimeters, oscilators etc. That would be helpful.
You can either calibrate with DBX on or off. I mostly record with DBX on, so I calibrate with DBX on. If you're going to record with DBX off, calibrate that way. I'll make a list as a blog stub one day, meanwhile jot down the items you see in the video.
Hello. I’m struggling to find a tech to repair/service my TEAC 144. I think I’ve diagnosed the problem using your previous vids but am not confident in my ability to repair it myself. How can I contact you regarding this?
Thanks for your very informative videos!
Adam
Unless you need to send me photos (in which case msg me on Facebook) I'd rather answer questions here where my responses might help someone else reading. I must admit I am not a fan of the 144 from a repair-persons perspective...the idler mechanism on the transport can be very difficult to get going and the electrics are very laborious to dismantle, and those issues make the model a bad choice for a newcomer's first restoration project! But ask away, I'll help if I can.
Tetrakan Supermonobloc thanks for getting back. I have a noisy transport which then basically stopped working - figured it was the idler tyres from your diagnosis videos. I have bought replacement tyres but when I opened up the back and tried to begin dismantling (following the your 244 vids hoping for similarities) I was a bit overwhelmed and so stopped after a while because I thought I’d never get it back together again correctly. By the sounds of it you’re suggesting it’s more trouble than it’s worth. That’s a shame because for the short time it was working it was good fun to record on. Drums with tape saturation is an unbeatable sound! Thanks for replying.
@@dardsdards Yeah, compared to the 244 the idler mechanism on the 144 relies on an extra rubber tire, extra belt, and two textured white plastic wheels which become smooth with use (they are sort of equivalent in their function to the brass spindle on the 244, which, being brass, doesn't suffer from the same wear issues). Teac/Tascam no longer supply spares, so while its easy enought ot replace the extra belt, probably feasible to find some sort of rubber gromit or o-ring to replace the extra tire, until someone 3d prints replacement parts for those white plastic parts then refurbishment of that model isn't viable, sorry its not better news. The 244 wont sound exactly the same due to being DBX2, but its pretty close, and speaking subjectively I greatly prefer the EQ on the 244, and they are significantly easier to work on. Here in the UK they still turn up quite regularly in spares/repairs condition for under £100, and with time and patience and the videos I've uploaded you'll be able to do the work yourself, so that is what I'd suggest you move to, good luck!
@@dardsdards TEAC service in New Jersey still repairs and calibrates old Tascam machines.
Hello, I have a problem with my Tascam 424mkI (well, more then one but this is the most serious). Basically when I record the audio seems ok but when I play back it's barely audible. I tried to clean the heads with isopropyl alcohol and it seemed to work for a while. Is it possible that it needs to be calibrated? Could the heads be damaged? and if so, could be repaired/replaced? I know it’s quite impossible to help me this way but your opinion would be very helpful
Thank you for your videos btw
Record and playback are handled by the same dual purpose magnetic head, so if you have playback on all 4 tracks, all four segments of the head work properly. It is common for the record amplifiers to need to be turned up, I think that is the most likely cause if your issues, but you should calibrate playback amplifiers first - ideally with a proper calibration tape, but you can do it roughly with any prerecorded tape; just make sure all channel meters respond in a similar way a loud passage...check Ch 1 and 2 then flip the tape over to use the same passage (the audio will be playing backwards but the peak amplitude will be the same) to set Ch 3 and 4
@@Tetrakan Man, thank you so much for your answer. I don’t know if I’ll try soon because I’m totally inexperienced and I don’t want to do any damage but at least I know that somehow it can be fixed :)
can i use a simple Mono Synth with Sine Wave VCO instead of a function generator too for calibrating?
Yeah definitely. If you’re going to calibrate meters, adjust the output of synth using the ac voltage reading on a multimeter before inserting the signal into the portastudio, but for troubleshooting circuits the voltage isn’t critical, any sine wave source will work.
@@Tetrakan thanks. i own a multimeter, oscilloscope only as VST plugin. there's a video on youtube on calibrating the 414. the guy says, the sound source frequency should be 10kHz at 1 Volts. i have about an idead what that means!
Please can you help me understand the process for calibrating tape levels? Do you have a voltage you are aiming when measured on the scope, or can you assume that if the channels are in the same ball park they can't be farr off and so you just need to balance each channel so they are consistent with each other? The manual gives the nominal output level from tape outs as -10dBV which I think would read around 0.9V peak to peak on the scope. If you were to use a tape that was recorded at 0dB on the Tascam's meter, should the scope (in theory) read 0.9Vpp?
I would say that getting mixer channels, record amplifiers, playback amplifiers and therefore tape tracks to respond in a similar way to each other is the first priority of calibration ( a bit like making a guitar In tune with itself) and making the best of the dynamic range of the system ( guitar is not only in tune with itself but also at concert pitch) is a secondary priority. I agree -10dBv == around 0.9 v peak to peak which is why I suggest ensuring the meters all respond correctly to a -10dB reference tone or equivalent before moving onto setting playback levels. However, for the calibration tape I have, when I set the playback trimpots so the tape output = 0dB, then make test recordings which played back at the same volume they were recorded at, I could tell by the extra harmonics in the sound sound and the squaring of recorded sine signals on the scope that I didn’t have the correct gain structure, and therefore the calibration tape I was using should actually read above 0dB on well calibrated meters. I guess this is because teac made one full-width tape on ferric stock for the calibration of ALL their cassette tech, so it plays back hotter in a portastudio which expects type II cassettes? I have found through experimentation that by using the top of the screen on my cheap ‘scope as the calibration point for playback amps, record and playback levels are above the noise floor and below saturation levels, and I get a good sound quality overall. Since the vintage teac test tape I have is not well documented, I might be a dab or two out from perfect specifications, but the fidelity is good. Does that answer your question?
@@Tetrakan Yes thank you mate. I spent this evening going through the process you described and I'm really happy that the meters are consistent across input, record and playback. The calibration tape I bought was a tenner on eBay with a 3k tone at 0dB and wasn't overshooting the meters so I could use the Tascam meters rather than the scope. Thanks for all your videos, it's an amazing resource.
Additional thought: do you ever need to physically strengthen the jack inputs on any of your machines? Mine are pretty wobbly and I don't know if they were just flimsy out of the factory or if they have worked loose. Makes me nervous that something's going to break if I don't take extra care. Would be interested to see if this is something you deal with.
Thanks. Wiggly Jack sockets- depends on the model. Some of the 80s ones it's part of the design, 90s ones it's usually a bad sign since the only thing holding the socket steady is the solder connections...what model do you have?
@@Tetrakan Mine is a Tascam 246. I haven’t taken it apart any further than getting the bottom of the case off, but through the gap in the chassis it looks like the whole jack socket and associated gubbins is wiggling all together.
I don’t think it’s anything to worry about. On the 246 the sockets are attached to the metal chassis using flexible clips, and those have some give to them. It’s actually an advantage because the strain of inserting and removing the jack plugs isn’t passed onto the solder joints.
Hello how are you? i would like to ask you for advice on a problem i have with the my tascam 244. i inserted a 4 track tape i had recorded on another 244 and i noticed that channel 4 is very low, barely audible. I tried to record and on channel 4 it records but always very low. I tried to raise the trimmer of the amplifier on channel 4 but even at maximum it is too low compared to the other 3 channels. do you have any idea what the cause could be?
Hello, there are two amplifiers, a nevfor recording, one for playback, have you tried turning up both, or just the playback amplifier? See my calibration playlist for details. Occasionally I have seen 244s where even after calibration of both amplifiers the signal is too low - in this case, dry solder, leaky coupling capacitors or even faulty operational amplifier chips may need to be replaced, I cover some of these topics in my electrical troubleshooting playlist.
could the head be worn out?
I don't think so. Lapping occurs on higher speed, higher tension reel to reel machines, but I have never seen lapping (erosion from friction) on a cassette recorder. It's possible for the internal coil if wire for track 4 to break, but if that was the case, track 4 would not play back at all.
@@Tetrakan yes I have proved but channel 4 always remains very low, the hand moves by one millimeter in play, but audible. in rec i see normal moviment meter signal entry in ch 4, senza problemi.
I tried a 4 track cassette of my old tascam which I know for sure works and in this new 244 thechannel 4 remains extremely low .
then excluding the cartridge (which I seem to have understood not to be the cause of the problem from what you said) how can I begin to check channel 4? what should i disassemble? thanks for the help
when I turn up the trimmer of the channel 4 play amplifier the volume increases, but not by much, could this help to understand the problem?
Hopefully you see this comment, I got a tascam 246 and it functioning except each channel receives the same signal at different db and the playback volume on two tracks are super low compared to the record db, could I adjust that on my own?
Yes. The meter sensitivity is controlled via trimpots you access via tiny holes In the top of the plastic case. The record and playback trimpots are located on the big flat board mounted behind the mixer. Normal and double speed playback level are on different trimpots. Their locations are in the service manual which is available for free download from my blog. Adjust the playback amps first, ideally using a calibration tape though a uniformly loud passage of any tape will give you a rough idea of playback volume. Adjust record volume only after meters and playback amplifiers have been set, in that order. Good luck!
@@Tetrakan Thank you very much! I'll take a look at the pdfs when I get home, thank you again !
You're welcome. I do have tear down videos on the 246, I think they cover the calibration trimpot locations? Although I don't have a video specifically on 246 calibration, only this one, it is similar enough a procedure to a 244 you can use this video as reference, good luck.
@@Tetrakan You mentioned both the slow and high speed have different playback trim pots, are each of those groups subdivided into tracks? Track one is excessively low. Also no matter what channel, if I route any channel to track 3 and/or 4 the PGM meters receive no signal, only in monitor. Anyway, I will look at the pdfs now, thank you!
If memory serves, the settings are made per track, so track 1 has 2 trimpots, one for fast and one normal speed, and so on, it’s the level coming back from the four regions of the cassette. The routing through the 4 buss faders to the VU meters may be a different issue? I seem to remember that routing occurs on two boards in the middle, and a little rca patch bay on the rear panel, not the big flat record/playback board behind the mixer…