TASCAM 414 - random vocal popping/clicking, only on tape playback

[judeseda]

I have been learning and using an old TASCAM 414 mkII unit I got from a friend for about a month now. I've been surprised by its quality and fidelity save for one persistant issue.
There's this medium-pitched popping/clicking sound pervading my vocal tracks. Its features are so:

*This does not occur when recording acoustic guitar with the same mic/input/settings, only happens on vocals
*The pops are not audible in monitoring input, only when listening back to tape directly or with tape cue. I have no idea if it's occured or will occur until I listen to my finished recordings
*The pops are linked to the vocal delivery and phrasing, perhaps responding to some sort of plosive element
*I have learned to on-command trigger these pops by smacking my lips near the mic - the plosive sound while monitoring is barely audible but the resultant pop on tape is very loud, it has an almost-electronic quality to it
*Using a new section of tape does nothing, cleaning the heads does nothing, using a pop filter does nothing, EQing does nothing, this is all analogue.
*The pops are baked onto tape and make it to my DAW when I send the track into my interface

I cannot get it to stop - all my vocal takes are partially unusable - has anyone had this problem or an idea of how to fix it?
Cheers

 

[Jack Saturn]

Can you upload an audio sample of this somewhere so we can have a listen?

 

[judeseda]

Great point! Uploaded a little clip of an isolated vocal track which had some especially bad pops.
Example clip audio

 

[Jack Saturn]

Checked out the audio file. To confirm, this problem was already occurring when you acquired the machine from your friend? I've worked on a lot of Tascam 414 units and I've never heard anything specifically like this, but my hunch is that there is some component that is being repeatedly "woken up" by certain plosive sounds, as you've mentioned.

A few questions:

What is your vocal chain?

Does this issue occur on all tracks?

If you can, try recording a vocal to another device through the same vocal chain, then feed it to the 414 as a line level signal. I'm curious if the popping still happens in that scenario.

 

[Jimnield]

Have you degaussed the heads? Its worth a try and they should be done anyway.
Can you run the vocal mic through a compressor prior to recording?
It might be the dynamics of the vocal causing the noise reduction (dbx?) to freak out.
I had this issue once using a tascam portastudio in a caravan, it was hypersensitive to any electromagnetism. Once indoors, degaussed and properly earthed it was fine.

 

[judeseda]

Checked out the audio file. To confirm, this problem was already occurring when you acquired the machine from your friend? I've worked on a lot of Tascam 414 units and I've never heard anything specifically like this, but my hunch is that there is some component that is being repeatedly "woken up" by certain plosive sounds, as you've mentioned.

A few questions:

What is your vocal chain?

Does this issue occur on all tracks?

If you can, try recording a vocal to another device through the same vocal chain, then feed it to the 414 as a line level signal. I'm curious if the popping still happens in that scenario.

Thanks for your reply,

Yes, this has occured essentially the entire time I've used the machine, which is about 2 months. It was sitting in a box in storage with the other owner before that.

My chain is
Neumann condenser mic -> XLR/XLR -> Behringer MIC200 -> XLR/TRS -> TASCAM 414 Line in
It does occur on all tracks, and again, when I recorded this same song with guitar + vocals in a combined take on the same track, this did not occur.

I'll attempt what you said about sending it in as a line level signal and see if that changes anything.

 

[judeseda]

Have you degaussed the heads? Its worth a try and they should be done anyway.
Can you run the vocal mic through a compressor prior to recording?
It might be the dynamics of the vocal causing the noise reduction (dbx?) to freak out.
I had this issue once using a tascam portastudio in a caravan, it was hypersensitive to any electromagnetism. Once indoors, degaussed and properly earthed it was fine.

I have not degaussed but am aware that this is something that can cause problems to old tape machines. Definitely would want to try this as a static/electromagnetic response seems to me a very logical culprit considering where in the signal the popping synthesises.

I'm not sure what device I should use to degauss. I did a quick search about demag wands and it doesn't look like they'll be easy to source. I live in Australia so getting things shipped from overseas often takes at least a month.

Know any other ways to source demagnetisers?

I'll also attempt running thru compressor to ease out those peaks. Will a guitar pedal type compressor work fine? I don't have the means for bigger units or anything like that.

 

[Jack Saturn]

You may have stumbled on another possibility toward the end of your last reply — if the signal is peaking, and thus popping/clipping/distorting to tape, it's possible that this might be something that is only audible in playback but not while tracking.

If you try compressing the signal on the way in — or even just hitting the tape slightly quieter — and the problem is still present, here are some other thoughts to consider:

I'm assuming you're recording vocals and guitar with that same signal chain?

If so, another thing to try: record a take that begins with guitar and then switch (within the same take) to vocals. Let us know if the problem isn't present during the guitar portion but is during the voice. I'd like to rule out that there isn't some kind of grounding issue.

If you have any other cables to test in place of the XLR-to-TRS one, that would also rule out that there is an issue with that cable (related to grounding or something else). Of the entire signal chain, if some part of it is causing the problem, that seems the most likely.

 

[Mark Richards]

Demagging and head cleaning are both standard maintenance requirements that help assure high fidelity recordings. Magnetized heads and dirty heads have the potential over time, as the magnetization and oxide shed builds up, to reduce or erase high frequencies. Magnetized or dirty heads don't cause pops and tics. Tapehead demagnetizers like this are relatively easy to find at pro-audio dealers (like Sweetwater here in the US) if not comfortable sourcing from places like Amazon.

Making assumptions/jumping to conclusions (e.g. vox v acoustic guitar) is not a wise place to start your trouble shooting. There are numerous mechanical and electrical possibilities as the source of the pops/tics.

To troubleshoot effectively, you need a systematic process of elimination, and that requires starting with the simplest signal chain to confirm if in fact it's the recorder itself.

If it were me, before diving down rabbit holes, I'd start troubleshooting by assuring the portastudio is set to its standard out of the box factory configuration (i.e. all adjustable controls and menu options set off or to neutral), and nothing is plugged in except the power supply.

The second important thing is to use a new, store-bought virgin cassette tape of the type for which the portastudio was specifically designed.

From that point, make a blank (no signal) test recording, on all tracks, with nothing in the signal chain, and observe the result.

Next plug a standard dynamic mic into the mic input; make a test recording of each track, with the signal peaking at -3VU from a distance of about 12 inches from the microphone (eliminates proximity effect; and minimizes chance for a transient that's too quick to hear in real time while recording).

Repeat with the condenser mic (assuming the portastudio can power it).

Repeat with a steady-tone signal on the line inputs, one track at a time. Observe the result
This rules in or out: the recorder/player, the cassette tape, and the cassette shell.

If the portastudio fails, then the information obtained will help guide further diagnosis of the portastudio's mechanical connections and electrical circuits.

If the portastudio passes, move on to each of the outboard gear units, one at time.