Tascam M-___ Story...

  • Thread starter Thread starter sweetbeats
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I wish I could remember to take a clear picture of the colors on my M3X00s. I'm color blind, so I don't use the color for reference, but I do have more than 2x the number of channels I need and plenty of spare knobs.

Sadly, they don't look the same as the ones on your mixer.. I'd be happy to share though :)
 
RFR said:
I dunno. Get it working first and then worry about color coding?

:D
But at the same time I understand. I have 4 vintage turntables I'm working on, and while I'm waiting on parts, my head's all wrapped up in the cosmetics.

I 'was' all picky about the knob colors on my console while I was working on it. But now that I'm using it daily, I could care less. :)
Click to expand...

You're right on all counts...I'm sure it won't matter when it starts actually getting used, but I really enjoy making it "right"...its part of my process...and yes the biggest cause at the moment is I'm waiting for parts. :D
 
sr71rules said:
I wish I could remember to take a clear picture of the colors on my M3X00s. I'm color blind, so I don't use the color for reference, but I do have more than 2x the number of channels I need and plenty of spare knobs.

Sadly, they don't look the same as the ones on your mixer.. I'd be happy to share though :)
Click to expand...

That's a really nice though...thank you.

You are unfortunately correct though they are entirely different knobs.

I think I've decided what I'm going to do...I'm just going to make the color scheme the same as on the M-500 and M-300 mixers and pretty much every other period mixing section. If Teac had gotten this thing to market that's what they would have done. The input trims would be red, the AUX buss controls would be green...the EQ knobs would be orange (but I'm going to alternate putty and orange), and the monitor section would be orange also...pan controls are always putty. The M-__ is unique in that it has pots for the PGM group masters as opposed to sliders, so I'm just going to stick with what the M-__ came to me with on those controls which were red...which makes sense since they are master summing controls...I'm only going to do that for the first 8 modules though, because the PGM master controls on 9-12 correspond with the AUX masters...so I'll make those green. I'll have to do some reconfiguring of the color scheme for the buttons. But this was a moment of clarity...the ideation "why don't I just do what they would have done?" Now to tally up how many of what color knob caps I need and start hunting.
 
My big DDA uses different colors for the knobs and different colored caps, makes for plenty of combinations! I don't know, does Tascam, sorry, did Tascam make different colors for the bodies? Or are they all putty? Red for input seems fairly common.
 
For this era and style of knobs there is only the light brown knob body color. There is also a dark brown version but as far as I know those were all spline shaft type knobs vs the light brown which are D shaft type.
 
It's settled...the knob cap color issue. I pilfered around in spares and reconfigured a couple modules, both the switch caps and the knob caps...I'm just going with how I think Teac would have done it if the M-__ had made it to their product lineup...and I think it looks better and is more functional. I think part of why it is more functional is because it's just what I'm used to seeing after looking at M-300 and M-500 mixers long enough...trims are red, auxes are green...eq and monitor orange, pans putty...Now to get ahold of what I need parts-wise to do all the modules...im in the middle of some dealings and once the dust settles from that I can take a tally of what I still need.

Here's a pic of the new configuration...the two reconfigured modules are the pair on the right in the picture:

IMG_7117.webp
 
So I *think* in order to do the color scheme change i need the following knob caps:

• 12 large red; I have 14
• 14 small red; I have 12
• 4 large green; I have 13
• 12 small green; I have 27
• 48 large orange; I think I have 44

So I need to track down 4 large orange caps and 2 small red ones.
 
If you end up finding a source, please let me know SB.... I need a tan cap for the 234 someday.....
 
Okay! Just bought a Teac Model 2A mixer for cheap off craigslist...it, among other bits has 6 of the large orange caps. So all that's left is the 2 small red caps.
 
I'm guessing the red capped knobs from a 388 aren't the same right? I have some of those.
 
Annnnnd just got an acceptance on an offer I made for the rest of the small red knob caps I need, so that's everything...I can execute the color-scheme change. :guitar:
 
Well.. that was fast :)

You're not far away from opening your own Tascam parts depot at this rate...
 
Well I was just fortunate to be able jump on some great deals on local offerings (Teac Model 5A and 2A mixers), on eBay listings for a part-out on a Tascam M-50, and scavenge from my own M-500 spoils (I have all the modules from an M-512). Between all that and a few random spare color caps I already had I've got what's needed for the job!
 
Finally did something of actual substance on the M-__...I think I've avoided working on it because the power supply and noise floor issues have just sucked the enthusiasm out of me for working on it. It's hard when there are persistent problems that don't make sense, and are seemingly impossible to resolve. So in the meantime I repaired/refurbished a couple M-106 mixers, a 388, and a Boss RCL-10 comp/limiter.

I got my Mouser order last week. In addition to power supply parts, it included parts to complete what's needed for opamp swaps, and new tighter tolerance lower noise parts for opamp feedback loops. I'll get to the last two categories later...first is to try and get the power supply to perform well...I'm basically shotgunning all the components in the +/-15V supply...about halfway done...will finish up and test in a few days.

IMG_7263.webp
 
So, among other things, I spent some time on the M-__ this eve...while watching the election.

I finished installing all the new components in the +/-15V supply...and tested it. It's weird. When I scope the waveforms off the + and - outputs of the bridge rectifier, they are different...like significantly. Whatever AC ripple is there should be the same between the two outputs, only 180 degrees out of phase. Well, the waveform for one side wanders up and down on the scope display, and the other sits still but is lower amplitude. I'm wondering if it is something funny with the scope I'm using...it's a borrowed 20MHz scope because my Tek 455 scope has gone wacky. The borrowed scope is a generic brand...anyway, the ripple is less than 10mV...and that drops to about 1.2mV at the power supply outputs. It's pretty clean. And stable. And the DC amplitudes are correct. So I think I'm going to just call it good on that part.

Then I decided to finish the Control Module (i.e. master module). What I'm doing is replacing the carbon film resistors and ceramic capacitors originally installed in the feedback loops of select opamps with metal film resistors and new XR7 caps. This will probably make no difference, but the metal film resistors have a lower thermal noise coefficient (they are quieter), and the new XR7 caps could potentially afford a better sound quality. I'm only doing this in the feedback loops because that's where it is mich more likely to be an impact, if one is even evident...and I'm only doing it in mix critical opamp circuits. So I got that done for the Control Module...

IMG_7355.webp

And then I decided to put the Control Module back together. It's been apart forever because I thought it was the source of the intermittent noise issue I'd always had...turned out that was from the glitchy internal power connector on the motherboard in the mixer frame. I rectified that. I'm still dealing with a high noise floor issue (or maybe not...more on that in a bit...), but I know that noise floor issue isn't in the Control Module. Anyway, I decided I wanted to get it all out back together since I am considering it "done"...it's been recapped, had numerous repairs executed and modifications to improve sketchy wiring or connections, modified to eliminate some scary proto-jank, cosmetically refurbished, had select opamps upgraded and some opamp feedback loop components upgraded. So I put it back together with the new knob & switch cap color scheme...it's nice to see it back together again:

IMG_7356.webp

Powered it up and everything seems to work just fine. It's noisy though...but I know it comes from upstream of the Control Module...and maybe it's not as noisy as I think. The M-__ utilizes the same dual 386 opamp headphone circuit found in a number of other Teac/Tascam units and it's just a noisy design. So I'm not sure if what I'm hearing is headphone amp related or a real problem...and I'm thinking I might just be experiencing normal noise levels but have things cranked up way louder than I ever would during normal tracking/mixing processes. I need to do some objective noise floor tests. And I still need to draw up a schematic for the output level boosting circuit to determine if I still have work to do on the power supply that powers that circuitry. And then last but not least there are some select opamp upgrades and feedback loop component upgrades I want to do on the I/O modules.

Progress I suppose.
 
Did some initial testing to get a baseline for the noise floor of the mixer last night. Also made some more progress with getting the knob and switch caps converted to the new color scheme. 9 of the 12 modules are completed...I'm still waiting on arrival of some additional parts to do the other three. Here it is with 8 of the modules installed:

IMG_7360.webp

IMG_7361.webp

I really like how it looks much better than either how it was when I originally took possession of it, or the first color scheme to which I changed it. I think this new one just makes more sense to my brain because it follows the same scheme as so many other Tascam mixers: red for inputs, orange for EQ and monitor buss, green for AUX busses, etc. Notice the knobs at the very top of the strip...the 5 on the left are red and the 3 on the right are green. Those are the "BUSS MASTER" pots. For modules installed in the first 8 slots of the frame those pots control the level sum of PGM groups 1-8 respectively. For modules installed in slots 9-12 those pots control the level sum of AUX busses 1-4 respectively. It doesn't matter what module is installed in any given slot...the function of that control is determined by the slot into which the module is installed. It would make sense for each module's color scheme to be identical to the next, but I wanted some visual differentiation to the scheme for those modules that I will normally install in slots 9-12, and to have those particular modules' BUSS MASTER pots be green instead of red since green is the color for the AUX busses and normally the AUX masters are green on other Tascam consoles. I am also using slightly different fader caps on modules 9-12...they have a white center stripe instead of orange as on modules 1-8...just another minor visual differentiation at the bottom of the module to compliment the one at the top. I could have done that to any of the 12 modules, but each module is hand labeled by number. It doesn't matter where they get installed, but simply because they are numbered 1-12 that's how I want to install them in the frame in that order. So the three right-most modules are module #s 10, 11 and 12. The 5 on the left are actually module #s 3, 4, 5, 6 and 7. I'm using those modules for my noise testing because they are unmodified. Modules 1 & 2 already have opamp upgrades as does module #8, and module #9 is currently partially disassembled because I'm studying it in order to draw up the schematic for the BUSS OUT level boost circuit. Anyway...more than you wanted to know.

So as far as the noise floor testing, there's more to do, but so far I've determined it's a relatively noisy mixer. Here's what I know so far as far as broadband noise measured using my Fluke 85 DMM:

Test conditions:

• 8 of 12 I/O modules installed
• 8 modules sourced to the MIC input
• 150R resistors strapped across pins 2 and 3 of the MIC jacks (to load the mic preamp)
• MIC trims at maximum
• EQ bypassed
• PAN controls set to center
• channel faders at unity
• stereo master fader at unity
• Fluke 85 DMM connected to STEREO R output jack and set to AC volts

Under the above conditions the DMM displays 0.4mV which is a signal to noise ratio of -58dBV.

If I set the PAN controls to hard R the DMM displays 0.6mV which is a -54dBV noise floor.

If I mute 7 of the 8 modules (PAN returned to center position) the DMM displays 0mV to 0.1mV...I'll call that -70dBV.

So, not so good. I've got some additional testing to do maybe this eve to narrow down if the noise starts up in the head amp or is further down in the signal path...or a combination. I dunno...it may just be a noisy mixer...there is quite a path signal has to traverse...to get to the channel fader signal from that mic jack goes through 4 different PCBs, goes through some relatively complex analog switching transistor arrays (because of the programmable global remote source switching features)...we'll see. My goal at this point is to try and nail down if it is noisy just because it's inerrant in the design but the design is technically correct, or if it is inerrant in the design because there is a design flaw, OR if there is some type of global failure.
 
Could very well be that something is still not right but to put it into perspective, my old Fostex 812 mixer had a SN ration of 53dB weighted (out of the factory) when all 12 MIC inputs are used.

I know that after 20+ years it had drifted off spec considerably because I replaced it with a Tascam M1516 which claims 55dB weighted out of the factory when all 16 MIC inputs are used.... and it sounded dead quiet compared to the Fostex.
 
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