Tascam 688 (and 644) Mixer and Scene Display Panel Demystified! 

Glad it was helpful…! What’s old is new again with some TLC. Beware if the capstan belt was melted the pinch roller may also be needing replacement. I highly recommend the rollers from Athan Corporation. Well worth the expense especially on the 8-track cassette multitrack machines. Again, glad the video was helpful and deepened the usability of the machine for you. That’s exactly why I created the video.

As far as 8-track cassette multitrack machines the 688 definitely offers the largest menu of features...more than most people need, but with the onboard sync and MIDI capabilities, and the hardware inputs, outputs, bussing and assign capabilities the mixer is the most flexible of any cassette multitrack machine. And I know the digital bussing/routing “scene display” interface can be a bit daunting, and may not work well for some operators, the hidden gem of it is its implementation means all the signal routing/bussing/assigning switching is handled by electronic switching. So there are no physical contact switches with any of those functions, which means no switches to get dirty, no contacts to corrode, etc...this generally means greater reliability and greater signal quality through the signal path. Yes, it also means if you have logic components that go belly up it can be more challenging to diagnose and repair, unless you are into logic circuitry, but I think this facet of the 644/688 goes a bit unnoticed and would contribute to better signal quality throughput from tracking to overdubbing, bouncing and mastering.

Awesome. Thanks!

Right on...that’s perfect! Thanks for watching and for the feedback...have fun with your Tascam!

I’m sure you’d figure it out, but a little demonstration can’t hurt. Good luck on your search!

I don’t do a lot with MIDI, so I’m not necessarily the best resource on that subject. The 688 Owner’s Manual goes into a pretty good overview of the MIDI functions and features starting on page 30, though it’s focused on integration with standalone sequencers since computer based DAWs were not yet commonplace. Basically the 644 and 688 have the features of an MTS-30 onboard, MIDI timecode with song and position pointer (FSK) is recorded or “striped” on track 8 (track 4 of the 644), and then the sequencer or DAW can “listen” to that timecode to keep MIDI sequences locked to the tape. There’s more to it than that, but that’s the high-level overview. Pages 30-35 of the 688 manual are worth a read because they cover not only some education on MIDI sync and what you can do with it, but specifically what the 644/688 can do and how to do. Understand you can do the same thing with any tape machine and a MIDI sync box, the 644/688 just have the features onboard, as well as the ability to receive MIDI control messages from a sequencer to control a limited number of mixer functions (change routing scenes, switch channel mutes on and off), which IS unique to the 644/688 among any other cassette multitrack machines (though not uncommon among many analog mixing consoles of the day, including a number from Tascam).

The Dual buss on the 688 and 644 is a really powerful facet of the mixing section. It is basically a 10 x 2 monitor mixer within the main mixer, but what makes it powerful is you have multiple source options, selectable per channel, and multiple output options. Each of the 10 Dual buss input channels can source either the MIC inputs, LINE inputs, TAPE tracks (Dual channels 1~8 only of course, since there are only 8 tape tracks), and the POST fader signal of the respective mixer channel. The Dual buss has its own dedicated output jacks, plus you can select the Dual buss in the monitor select switchrack, and you can also link the stereo output of the Dual buss to GRP 1-2, 3-4, 5-6 or 7-8 to record to tape. Common uses for this flexible mixer within the mixer is to use it as a cue mixer for tape tracks during overdubbing, as an additional pre fader stereo AUX send that can source either the MIC or LINE inputs, or as an additional post fader effect buss. It is also how the 688 mixer can simultaneously source 20 inputs (all 10 MIC inputs and all 10 LINE inputs)…the channel inputs can be set to one (MIC or LINE) and the respective channel Dual input can be set to the other. Hope that helps!

The 688 has 20 or more inputs that can be mixed at once, so no problem handing 5 stereo sources. But the 688 only has 8 tape tracks for recording. “Tracks” refers to the discrete tape tracks, “channels” refers to signal pathways. The 688 has 10 channels on its mixer, but each with multiple inputs that can be accessed and summed in different ways. And then there are 8 mix busses. A “buss” is a signal path that can combine signals from multiple channels…take multiple things to one common place. Like a bus. The 688 mixer has more busses than the 8 mix busses, but I’m highlighting those because we’re talking about recording and there’s one mix buss per tape track. 8 tracks, 8 mix busses. So you’d need to combine your 5 stereo sources (10 channels total) in some way to 8 channels by maybe summing two of the modules together on two of the tape tracks.

@@SweetbeatsTechStop thank you so much, this was really helpful!

Nothing simple comes to mind. You might want to try posting the question at the homerecording.com forums, there is a sub-forum there for analog equipment. There’s a member there with some experience with 688s and I have a faint memory there was a VU meter issue and maybe a solution. Is the issue just with the meter or are there audio problems with that channel?

Are you talking about with the 688? The answer is yes to both (644 and 688), but the 688 is much better suited to do what you’re talking about because it has 8 mix busses. So you would connect the 8 GROUP OUT jacks to your tape machine inputs, and connect the tape machine outputs to 8 of the line inputs.

What position is the MONO switch in? Up or Down?

@@SweetbeatsTechStop thank you for the answer. my headphone adapter was messed up. it's working well!

Hi. So let’s iron out a little terminology…tracks are tape tracks. Sources are connected to mixer input channels. So you’re first sentence where you say you assigned all your tracks to tape…am I correct you assigned all your input channels to tape tracks? If that’s correct, step 1, tell me how you assigned all your input channels to tape tracks, and how many tracks have material recorded on them. Are you confident your input channels made it to tape tracks? How did you have the GRP 1-2, 3-4, 5-6 & 7-8 faders set during tracking? How did you have the PAN controls of your input channels set and then in scene display panel how did you have each input channel assigned? If the answer to any of these is “I don’t know” then we need to go back to basics.

A big part of what can be a challenge to folks that aren’t familiar with the 688 or 644 is, first and foremost, the mixer architecture itself if you aren’t familiar operating a console that is more than relatively basic. And then the second challenge is how to access all those source and assign features. So, it’s more complex than basic, and many of those complexities are hidden in the Scene Display Panel. And this can be confusing because the tactile controls kind of make it look like a 10 x 4 console with 3 aux busses, but it’s actually a 20 x 8 console with 10 main channels, two configurable aux busses and a configurable stereo monitor buss. The other thing that’s confusing is there’s no main or dedicated “stereo L-R buss” per se…you have 8 mix busses, ganged in four pairs on the four two-channel group faders. Those groups feed the 8 tape tracks. You don’t use GRP 1-2 during tracking or overdubbing. If you’re used to a smaller format typical console, you’re looking for that master buss that you monitor. It the 688 and 644 are setup like a recording console, at least like Tascam’s iteration of a recording console, where you have input channels, groups for record bussing, and some form of monitor buss, which is like the clearing house of audio access during all stages of recording, and then you use two of the record buss groups for mixdown. This is the same as the M-50 or M-500 series consoles with their monitor mixer and 8 mix groups. So when you’re tracking you set the source of the DUAL buss for each channel to either input or tape so you can monitor inputs or tape tracks (when overdubbing) and source the monitor buss to DUAL, and then when it’s time to mixdown you set the input source for channels 1~8 to TAPE and assign to GRP 1-2 using the Scene Display Panel, and then set the monitor section to monitor GRP 1-2. So it’s DUAL buss for monitoring during tracking and GRP 1-2 during mixdown.

Hi, could you send me the service manual? Thanks!

Hi Farah, I hope you got your 688 on his feet with the new belt. Could you sent me also the service manual ? Thanks

@@Roykko You can find it online at hifiengine . Search for the 688 and it will come up.

Do you have the manual? And 644 or 688?

Yes! 688. I'm trying to run a reverb pedal through effects return 1, or alternatively to run it through aux 1, and then be able to spread out to multiple tracks @@SweetbeatsTechStop

So there’s all sorts of contradictory wording in your last message. You can’t run an external effect “through” the effect returns. Similarly, you don’t run an effect “through” an AUX send. And in either case you’re not “spreading it” to multiple “tracks” (channels?). I’m not trying to be a price by picking apart your wording. I’m highlighting stumbling blocks for me in your terminology that also may underscore misunderstandings on your part about how incorporating effects works, and my goal is to help with that and help answer your question. But I want you to do some work too, or you won’t learn. “Tracks” are tape tracks. Are you wanting to apply reverb to multiple tape tracks, or are you wanting to apply reverb to multiple mixer channels’ inputs? Your reverb box has an input, and an output. You use an AUX buss to feed the input…use the AUX 1 or 2 controls on each mixer channel you want to send to the reverb box…let’s say we use AUX 1. Turn up the AUX 1 knobs on each mixer channel to taste, you control the overall level to the reverb box with the AUX 1 master level knob, and connect the AUX 1 output jack to the reverb box input jack. If there is a mix knob in the reverb box set it to 100% effect or wet…no dry signal. Connect the output of the reverb box to EFFECT RETURN 1. Now here is were you’ll have to clarify what you are wanting to do or are trying to do before I can tell you what to do next, because the EFFECT RETURN jacks can go multiple places. You assign the return using the scene display panel. Hopefully that helps to get you started, it would you do something? Read pages 28 & 29 of the manual. Study them. Study them with your 688 in front of you so you can try the things the manual discusses.

I don’t understand your comment. The 644 and 688 have an electronic switching matrix instead of mechanical switches for source selection, input assignment and channel muting. The video isn’t about using the matrix instead of switches if you are having trouble, it’s about how to use the matrix, because there are no traditional mechanical switches to service.

Oooh, never mind. I found two presets that do all that I ever need the machine to do and that's good enough for me...

I would assume it’s broken. It’s pretty simple…turn the pitch control knob clockwise, the tape speed should increase, turn it counter-clockwise it should slow down. If it doesn’t do that something is not right. I’m assuming you’re talking about a 644 or a 688 right? You did specify.

Where’d you get your power cable?

@@billythekid3019 Ive already had it.

No, it’s proprietary. You either find a used one on an auction site or whatever, or make your own power supply and modify the interconnect since the connector on the 644 itself is pretty obscure. Not the best news, but that’s the long and the short of it. IIRC the regulated DC voltages needed are +5, +12 and -12. You can use an ATX computer power supply.

Yes, and yes.

@@SweetbeatsTechStop When new they were whisper silent. do you know how to oil a DC motor ?

They are not meant to be oiled or serviced. Maybe you should upload a short video of the noise. It’s hard to know what you are hearing without being able to hear it. It’s possible your motor needs replaced.

@@SweetbeatsTechStop I had to replace the Capstan motor with a new one. After assembling everything, it was working great but high speed had alouder than usual motor sound. The lower speed was less but still noticeable. So I opened it up again and noticed a couple of things. Firstly the capstan pin in the bushing was dry. This caused slight resistance on the belt thus putting a load on the motor. Secondly the new motor was mfg's over 20 yrs ago, and the internal lube was probably compromised. I put some PLP synthetic lubricant in the capstan pulley, pin bushing, and shaft out of the motor. PLP is the finest synthetic lubricant available, sewing machine or synthetic gear oil is too thick. It's as close to running like new possible. As long as the motor sounds hush & the same with and without the belt things are right.

Does your capstan shaft spin? Like open the cassette door, and with the machine powered up gently press on the switches that too if the cassette presses on when you load it. The capstan should spin up. Or maybe the capstan spins the whole time the 688 is powered whether a cassette is loaded or not. I can’t remember. Bottom line question is can you get the capstan shaft to spin? If no you probably need a new belt. Your symptoms read like a bad capstan belt.

@@SweetbeatsTechStop the FF and rewind works well so I guess the motor its ok, I hope. When the 688 is powered I dont think the capstan spins the whole time, I'll check what you suggested and hope for the best. Than you ~

Yes, the reeling motor is fine. But that has nothing to do with the capstan. The 688 utilizes a three-motor transport, one for reeling, one for capstan, and one for headblock assembly actuation.

There is no way to reduce the speed on the control panel. If the speed is too fast, it is the wrong motor (engine).

@@SweetbeatsTechStop Thanks. I'll keep trying to fix it.

@@k5257 where’d you get the power cable? Can’t find one anywhere

@@billythekid3019 Brought for repairs with it.

So, I had to replace the memory backup battery in my 688. The battery from the factory, as you may know, is equivalent to a 2050 lithium coin type battery but with electro-welded solder tabs on it so it is soldered directly to a PCB. What I did is I bought a 2050 battery holder, mounted that to the board with some RTV after removing the factory battery, and soldered wire leads to the terminals on the battery holder and then soldered the leads to the solder lands on the PCB where the factory battery was soldered. Done. It’s a bit tight in there as far as trying to mount the holder where it’s not obscuring any components, and if I recall the holder actually had to mount over one of the factory solder lands for the battery. So you have to actually solder your leads in and then mount the holder. Not the most perfect situation, but effective, and if ever there was need to repair things on the board in the future that were obscured by the battery holder, it’s easy enough pop the holder off and then re-adhere with a new spot of RTV. I only used a small amount of RTV by the way for that very reason. So that’s what I did. Makes it super easy to replace the battery in the future if needed because the battery just pops out of the holder like the CMOS battery on a computer motherboard. Hope that helps!

You want the 688 to chase Logic or Logic chase the 688? The 688 can operate in wither role with any suitably featured DAW, but if the DAW is going to chase the 688, then you'll need a synchronizer like a TimeLine Micro Lynx and you'll need the interface cables and a MIDI interface (if your audio interface doesn't already have a built-in MIDI interface as well).

What happens when you take the tape you supposedly recorded to on the 688 and play it back in a regular cassette deck, OR play back on the 688 and monitor via the TAPE OUT jacks. Anything?

@@SweetbeatsTechStop Hey, so that's the funny thing. On a whim I popped one of the tapes in my four track, and the test recording was there! Also, the 688 will play a regular cassette, previously recorded tape, although scrambled of course? That's the mystery- It will record, but not play that recording, but will play other recordings? It has to be in the programming/scenes/modes, etc.? But I am still trying to learn all of that- Like I followed the Manual pg 18-19 exactly several times? Thanks for you help- I'd appreciate any incites that you might have!

If the tape you recorded on the 688, that you can’t get to play back on the 688, plays back on something else, AND if a tape recorded on something else plays back on the 688, I’m reasonably confident there is nothing wrong with the record/reproduce functionality of your 688. It is something with your settings. To verify this, do what I suggested and take the tape you recorded on the 688 and play it back, but check to see if you have signal at the TAPE OUT jacks. Those jacks source straight off the playback amplifiers for each track before all the electronic source and assign switching. It’s like a direct out from each tape track. If you have signal there things are working, you just have to figure out what you need to straighten out with your settings and in order for me or anybody to help with that you’re going to have to list in exacting detail how you have things set when you are trying to monitor playback.