Tascam 388 - Boosting Individual Track Input Levels for Quieter Tracks?

[babecityrecords]

Hey all (and Sweetbeats, hero of analog advice on homerecording.com)

Once again returning to humbly ask for some advice on a Tascam 388 issue.
First, Sweetbeats, I feel bad for not following up on that other static issue I had that comes and goes -- it's not bleeding on the tracks so I'm not worried about it anymore.

Onto my real issue...

Recently, I noticed Track 3 is super quiet when recording, in addition to Track 1 (which has always been quiet, normally I just use this track for a metronome). Track 1 is a different story though, that channel has always been quiet.

I tried recording some acoustic guitar yesterday on Track 3 with a bandmate over, and listening back, the guitar was barely audible with two different type of mics (RE20, SM58) inches from the strings. Tried different mics, different XLRs, mic placement -- all super quiet. So ended boosting the trim almost to the max just to get some sound, and the guitar came in, but was so ultra super bass heavy and distorted in RMX/playback, that it sounded just awful... not in a cool lo-fi way.

When in monitoring mode, like right before I hit record to test the level, the guitar/track sounds perfectly audible and fine though.. not sure what's going on with Track 3 when it's actually recording.
All other tracks besides 1 + 3 are great.

I'm wondering, I heard that when take the top panel off the tascam (how I adjusted the tension arms to fix the time monitoring screen ages ago), you can adjust two "knobs" with a small screwdriver to boost the input gain for individual tracks. I'm curious if I can boost the baseline gain level on tracks 1+3 to make them more audible, so I don't have to boost the trim when recording quieter instruments. Also hoping I can avoid taking the whole damn thing apart again (as I did when Sweetbeats walked me through lubing that bad boi up a few months back).

SO-- three baseline questions!

A) Does anyone know which knobs (pictures attached) correspond with tracks 1 + 3 gain levels?
B) Is it a bad idea to adjust these gain levels? I know things will sound a little crunchier, but as long as that's not significantly boosting the bass I think that's fine with the style of music I'm recording.
C) Is this whole plan garbanzo beans and I should do something else first before adjusting the baseline gain levels on these two quieter tracks?

THANK YOU FOR ANY HELP!!

 

[sweetbeats]

I’m not really sure, but it sounds from your description there’s not a problem with your record level, it’s your monitoring level.

What I’m interpreting from your post is you can’t hear your source really well when monitoring before or during recording, so you are boosting the mic TRIM, but when you play back the track the level was too hot and the tape is saturated.

That’s not what the TRIM control is for. Set your TRIM level by performing the loudest part of your performance, turning up the TRIM knob until the red O/L LED just starts to flicker with the peaks, then back it off a shade. The TRIM is set. Leave it alone unless you are changing the source or you’re on to the next performance and it’s a different peak level in the performance.

Typically you then raise the input fader to the shaded area, assign the channel to whatever buss or busses the signal needs to go to, and adjust the buss fader(s) so the peak LED in the PGM meter is flickering. Then depending on the material and how the machine is setup you might back the channel fader off a bit or push it. Now you’ve set your level for recording and then you set your monitor level in the MONITOR mixer. So are you saying you do all that but you run out of knob for monitor mixer channels 1 & 3 to be able to hear your source(s) in the monitor buss?

If I’m understanding correctly and your monitor level is too quiet so you are cranking the TRIM, but your signal to tape is then too hot, adjusting the record level trimmers is only going to make things worse to tape. And I wouldn’t recommend doing that anyway. Those trimmers are for calibrating the machine…lining the levels and response up across all 8 tracks so they are the same. They are not for adjusting levels during the recording or mixing process. Bad idea. That’s what your input and PGM buss faders are for. If you want to know if your machine is out of whack calibration-wise, then you need to start at the top, cal the meters, cal the input level, cal the playback level (which you can only do with an appropriate reference calibration tape), set record bias, then record level for each track using an appropriate audio bandwidth rated level meter.

If you DO go in there against my advice and tweaker with things please use a non-conductive screwdriver.

The trimmers that adjust the record level for tracks 1 & 3 are R143 and R243 on the track 1/3 amplifier PCB. It’s all there in the pic from the manual you posted. The pic tells you which card goes to which tracks, then there’s the drawing below the overhead pic of the cardbay that labels all the trimmers and test points, then the chart to the right tells you, by function, which trimmer corresponds to which function.

SO…

A. See above.
B. Yes. Bad idea.
C. Yes on the beans. See above. Walk through the level setting process using the controls of the mixer as intended. Verify if I’m understanding your problem correctly.

 

[babecityrecords]

Sweetbeats -- not sure what I'd do without you. Probably give up on the tascam entirely... appreciate your continued support and help.

So, when monitoring in tracks 1-8, all levels sounds great -- in headphones, or in my studio monitors connected through the outs.
It sounds like I have a clear signal, levels look good (not in the red but right before), but when I actually record and listen back, that's when it sounds super quiet. So that's why I cranked the trim knob to see if that helped, but it really just didn't.

When testing mics and levels in monitor mode, everything sounds good and crystal clear. When recording itself and hearing myself play or sing in studio headphone, it also sounds like I'm getting a great clear signal. But when I playback the recording, I can't hear any of the instruments at normal volume -- when I cranked the trim and did the same take I heard it super distorted and bass-y.
So all this to say, I believe the recording level is messed up? Or what could cause it to sound fine in testing/monitoring/monitor in record mode, but then have it barely audible pickup in playback when in RMX mode / not recording?

That make sense? I can also make a video if you'd like.
As always, indebted to you, thanks!

 

[sweetbeats]

Yeah that makes perfect sense…I follow you.

Okay. You ever swap record/play amp cards? That’s the next step. Swap the track 1 & 3 amp card with another one. We want to see if the problem stays on tracks 1 & 3 or if the problem “follows the card” and is now on another pair of tracks. OR the problem goes away, which could indicate oxidized card edge connectors or bad solder joints.

Have you ever even had the amp cards out? If not they will be a struggle to get out. There’s information on this forum about strategies to safely remove them the first time. Once you get them out and apply some DeoxIT D5 and exercise the connections a few times they are much easier to remove and install.

 

[babecityrecords]

Hmm interesting. OK, good idea. I've never had the amp cards out, no.
But I only got the tascam in 2016, so it could have been done in the past without my knowing.

Do you mind linking me a good thread on how to do this? I'll buy some DeoxIT D5 now.

And do you think if the amp cards have never been out I'll still be able to handle this myself?

 

[sweetbeats]

https://homerecording.com/bbs/threads/swapping-rec-play-amp-card-in-tascam-388.378798/

Try that one.

It’s totally a lay-end-user thing you can do, you just want to bone up on some techniques and be aware they can be stubborn that first time if it’s been decades since they’ve been out.

 

[babecityrecords]

OK! Will try this out over the weekend.
Maybe a dumb question but everywhere I look I can't see any pictures of what the card actually is and where to grab it from? It's visible from the top of the machine, correct?

I marked up the previous picture here. Is the red arrow pointing to what I'm removing, and I'll swap it with the card below it, with the Pink arrow?
Is that correct?

And nothing to unscrew or or remove besides the top panel, correct? I just give her the ol delicate tug per the advice from the other thread you linked to? That does seem more detailed on pulling, which I appreciate:

+1 to everything j.harv said. He's spot on. Look in the corners of the cards. If there are little holes there you can loop some wire through them to give you something more to hold on to as you rock the card from side to side. You have to be pretty firm in your application of pressure but gentle (i.e. just do everything nice and slowly). Don't be surprised if it takes some strength the first time you pull a card out if that's what it takes. For many of these machines the cards may very well have never been pulled and, well, after nearly 3 decades they think they can just stay in there. There are card guides on the sides of the card, so you can't pop it out crooked...the guides will prevent that. Just grasp the corners with your thumb and forefingers and leverage the pinky-side of your hands against the surfaces to the sides of the card so you have some controlled leverage. Just work back and forth applying that slow but firm pressure...it'll come out.

If you have the manual there is a page in the service manual section that details which card is what.

Make sure the machine is powered off and unplugged before removing any cards, and make sure all the cards are in place before reconnecting to the mains power and switching the unit on.

And so I can understand the big picture, basically we're removing the cards and swapping them to see if the issue is with the cards or the channels themselves.
Ideally, the issue is with the card and that will be easier to fix with testing and soldering? And if the issue with the channel not from the card, it's a whole other set of issues I'd need to test?

THANK YOU!

 

[sweetbeats]

Maybe a dumb question but everywhere I look I can't see any pictures of what the card actually is and where to grab it from? It's visible from the top of the machine, correct?

Yes, correct. Look at the picture from the manual you posted a couple days ago earlier in this thread. All the cards are labeled in that picture.

I marked up the previous picture here. Is the red arrow pointing to what I'm removing, and I'll swap it with the card below it, with the Pink arrow?

Is that correct?

Yes that’s it.

And nothing to unscrew or or remove besides the top panel, correct? I just give her the ol delicate tug per the advice from the other thread you linked to? That does seem more detailed on pulling, which I appreciate:

Also correct. And the action is really kind of a rocking back and forth…pinch the corners of the card between you thumb and pointer finger on each hand, put your other fingers or sides of your hands on the chassis wherever you can and use those fingers to lever up…this gives you control so when it pops free it doesn’t come ripping out of the cardbay causing potential damage; lever a little on the left, then the right, then the left, rocking back and forth until it unplugs. And if you don’t have enough strength just grabbing with the thumb and finger, you’ll see there are holes in the corner of each card. You can twist the ends of some wire in each hole to make a makeshift bale or handle of sorts so you have something more to grasp, or even just put a zip tie through each hole…even that will give you something more to hang on to.

And so I can understand the big picture, basically we're removing the cards and swapping them to see if the issue is with the cards or the channels themselves.

Right. If your issue is on the track 1 & 3 amp card, when you swap that with the track 2 & 4 amp card, your poor performing tracks will now be tracks 2 & 4…the cards are all identical. It’s the slot they are plugged into that determine what tape tracks the feed and source. It’s a troubleshooting step that helps us start to hone in on where the source of the problem is.

Ideally, the issue is with the card and that will be easier to fix with testing and soldering? And if the issue with the channel not from the card, it's a whole other set of issues I'd need to test?

Well I’m not really rooting for the problem to be in a particular place or with a particular PCB assembly…the goal is just to figure out the source of the problem. Let’s not get ahead of ourselves. We’re just going to methodically attempt to hunt down the source of the problem.

 

[babecityrecords]

You're the best! Got it and this is great. Back ASAP, likely early next week.
Thanks Sweetbeats!

 

[babecityrecords]

Hey Sweetbeats -- finally had time to try this all out today.
I put various videos in a folder here so you can hear what I'm describing, and so you can dummy proof some things I'm explaining, if you have the time.
Here's that folder, with below videos labeled in red: https://drive.google.com/drive/folders/1Ee-KTwGbNzG3lkUCIrH5HE4rhSOLff8C?usp=sharing

BASELINE
So, first, before switching the cards, I did a test of each channel at the same volume + gain to just get a baseline and make sure everything still stands the same since I booted up the 388 since a few weeks ago.
To my dismay, all channels 1-5 sound barely audible to different degrees, then channels 6, 7, and 8 sound good. Of these good channels, channels 7 + 8 sound almost crystal clear and warm (god I love this machine when it actually freaking works) and track 6 sounds audible but not amazing, little muddy.
This is new to me that all other channels 1-5 sound awful. Like inaudible awful.

I've dropped in that drive folder above a short video that shows this comparison between the good and bad channels, so you can hear how crystal clear channels 6-8 sound as opposed to how bad 1-5 sound.
That video is in the folder titled "The Good and The Bad." In this video, there's like a ten second stretch where there's like no noise, because of how bad the channels sound.

Right before recording each channel, the VU meters still look good and monitoring sounds great, as if everything is going to record perfectly. Only in playback do you realize the audio isn't sounding like how it does in monitoring / before recording. I've attached a video of what I mean, titled "Channel 1 Test / Monitor Solid".

So, for the sake of trial/error and our original plan, I still swapped Card 1/3 with card 2/4, our original idea to see if that changed anything.
Everything still sounds bad on tracks 1-5 after swapping.
But by the way, the good news is your tip to use wire and create little loops to pull out the cards worked amazing btw -- otherwise it wouldn't have budged. Thanks for that by the way ha!

SIDE NOTE / STATIC NOISE
A side thing to note -- there's this weird static-y noise happening when the machine is just on, even with no microphones plugged in. It's on for the first 30ish minutes the machine is on, then it goes away. If the machines been on for a while, and I turn it off then back on, the noise is still gone.
I've put a video of the noise at it's peak in the drive folder, labeled, "Weird Static Noise Video".
I can't tell if it's being recorded on tracks, but I assume not. It's kinda quiet unless blasting the volume or listening back to one of the bad tracks with no real audio. Sometimes it's more noticeable, sometimes it's not. If it's not going on the tracks, then it doesn't bother me thatttt much, but it's definitely annoying and a bit concerning. I'm going to bounce some tracks later today and see if it's audible on the tracks or just via the machine and my cheap studio monitors.

I don't mean to distract from the main issue at hand and get sidetracked, but I'm mentioning this in case you think this might be notable or applicable to or our main issue at hand, tracks 1-5.
And since the noise goes away after about 30 minutes of the machine being on, if I ever fix this poor beautiful machine, I can always just turn her on an hour before any sessions to not run into this issue.. so not that big of an issue, but wanted to note for you.

THE REAL TEST CONTINUED--
So, after swapping Card 1/3 with Card 2/4, and noticing tracks 1-5 still sound like garbage -- I thought that swapping two bad sounding cards won't really help us achieve sussing out a bad card... the whole idea behind your plan.

I assume you'd want me to try swapping the seemingly bad cards with the seemingly good sounding cards, so next I swapped Card 1/3 with card 6/8, since channel 8 sounds the best.

After this swap and re-recording a test on each track, tracks 1-3 are still barely audible, and tracks 6 + 8 still sound great.

Specifically, track 8 sounds best and 6 sounds good but a little below that.

I created a 25 sec video of this test playback, titled in the folder "Test 3 card swap 1-3 + 6-8."

So, safe to conclude that the bad channels aren't because of these cards, but something else... correct?
I assume this is because the good channels still sound good after swapping the cards, and the bad channels still sound bad.

Let me know what you think I should try next, thanks so much for your time, patience, guidance, and help!

 

[babecityrecords]

Hey @sweetbeats -- sorry to bug you but any ideas for next best move to identify the problem?

 

[wkrbee]

Tape path clean, tension setup right- especially back tension, Using new tape?

 

[sweetbeats]

Yeah, what tape are you using, and can you put up some pics of your R/P head under good light?

Also try testing each input channel and assigning only to the L-R STEREO buss. Do you get good signal to the STEREO OUT jacks?

You haven’t gotten a response from me partly because you have a lot going on there and it’s quickly going to consume a lot of time trying to troubleshoot and fix over the internet. There seem to be an increasing number of 388s that are sort of bleeding out with problems. It’s hard to help people with these issues because of the relative complexity of all the interconnections and circuits in a 388. It’s hard enough to follow if you have the device in front of you and can read and understand the schematics, often frustratingly impossible if neither of these are the case.

I’m not trying to be a downer and I’d like to help more but I think it’s becoming increasingly important for 388 enthusiasts to have a good tech lined up because, as I mentioned, I’m seeing more complex issues rising up.

The static-ey noise on cold start sounds like bad connections that resolve as it heats up. That type of noise is usually related to DC voltage in the signal path.

 

[babecityrecords]

Hey guys, just wanted to say thanks again for your help.
I think at this point it's time I take it into a local tech shop to fix. There could be so much wrong and I don't want to break it further in the process.
I'll keep you all posted on what the issue is, once it's fixed, to hopefully help other people in the future with the same problem.
As of now, she's just been a giant paper weight in the office. :/

 

[babecityrecords]

Taking the tascam to Protech repair shop in Maryland today -- will keep you all posted on what my issue was!