DP-32 Screws Up Apps (and Theremin) When Turned On

[Craig Smith]

I have a 1st gen DP-32, (MIDI & CD) updated to V1.13, and I'd like to record sound sounds using my iPad (or iPhone) and a few different Apps. But every time I turn on the DP-32 the iPad (or iPhone) just goes completely erratic, the touch screen doesn't work as it should, it'll change apps, open my email, play dozens of notes at the same time, switch programs and several other things.
Also, I've never been able to record my theremin because as soon as I turn on the DP-32 it also starts acting completely erratic and impossible to play (insert theremin jokes here).

EDIT: I was able to get the iPad to not freak out when the DP-32 was turned on by using an iRig MIDI interface and using a MIDI keyboard controller. Everything works great. BUT, as soon as an audio cable from the iPad headphone output or the iRig audio (1/4") is plugged into the DP-32, then it goes nuts again.

Any help would be appreciated, it's driving me nuts.
Thanks!

 

[Mark Richards]

To better understand:
How are you taking the audio out from your iPad/iPhone and bringing it into the DP-32?

 

[Craig Smith]

With my iPad I use the headphone output, and connect to the DP-32 inputs with a 3.5 stereo plug (iPad headphone jack) and the Left and Right 1/4" plugs into the DP-32 inputs.
With the iPhone, (has no headphone jack) I use the 1/4" audio outputs of the iRig Pro Duo I/O.

 

[-mjk-]

Are all the devices on the same electrical mains circuit? Are they even on the same power strip?

 

[Craig Smith]

The iPad and iRig are both using battery power. There was no difference when the iPad was plugged in.
I've tried the DP-32 with a different electrical output all by itself and one with a power strip with other devices. No difference.

 

[Max Relic]

Does the issue happen also when switching on the devices in reverse order (i.e. first the DP-32, then iPad/iPhone...) ?

 

[Craig Smith]

Thanks for the suggestion, for some reason, I never thought to try that.
So I did.
The iPad is more stable, and even playable when the DP-32 is turned on first, but as soon as it's plugged in to the DP-32 to record, it gets erratic.

 

[-mjk-]

My guess is that somehow the cable is not right. It may be shorting the signal to ground.

 

[Max Relic]

Touchscreens work thanks to capacitance so the described issue could be related to strong static electricity field, high frequency interference along the audio connection between devices, bad electrical insulation in the Tascam power supply (likely bad capacitors) or something that eluded user attention so far.

@-mjk-, the audio cable can be easily checked, unplug the Tascam side and short the jack contacts repeatedly to induce (the supposed) iPad/iPhone fault.

P.S: I'm not sure if it's some kind of joke, anyway this case of Poltergeist possession is fascinating

 

[Phil Tipping]

My 2c is a small amount of mains 'leakage' from the Tascam power supply. If none of the other devices are grounded, a possible cure may be to add a ground somewhere, either plug something else (which had a ground connection to the mains) into the Tascam, e.g. a spare input, or a physical piece of wire from the chassis to mains earth.
These external PSUs are renowned for this. I find if I have nothing else plugged in to my DP-32, except power, I can feel a very small tingling if I lightly brush the back of my hand across the chassis. Some other gear behaves the same way, and they are all driven from PSUs with no earth connection. As soon as I connect something else which is earthed, this tingling disappears.

 

[-mjk-]

@Phil Tipping you should put a multimeter on that and measure the voltage. I would be very interested to see that!

 

[Phil Tipping]

Just done it... 110v ! This was with a cheapo multi-meter; don't know what the input impedance is.
Plugging in a jack cable from an earthed device to one of the inputs knocks it down to 0v. The Tascam machine doesn't even need to be turned on.
As mentioned, other devices can behave the same; some PSUs are better (even perfect), some are worse.
The 'back of the hand' trick is my goto technique for identifying this problem, but if you do find it works for you, be prepared to be ridiculed by those who can't detect it

 

[Max Relic]

@Phil Tipping I hope you will be replacing that PSU soon. At least is what I would do, as sensitive to AC dispersion as I am.

 

[-mjk-]

@Phil Tipping, Whoa, I would replace that PS ASAP! You guys use "manly power" in the UK too (as Pete Malendrone used to say). Might be a good idea to run a star ground with a direct wire to each piece of gear.

 

[Phil Tipping]

I tried another PSU and it gave the same results; both are genuine Tascam parts.
Agreed the voltage looks scary, but according to this info from Panasonic, it seems to be near the expected value for the UK; great term MJ btw
They also answer the question "Are these electrical 'tingles' dangerous?" with
"Whilst they are alarming, the appliance is not faulty"
If you've got a multi-meter handy, it would be interesting to see if you get any reading. I put mine between the exposed metal sleeve of one of the stereo output sockets to the chassis of a device which is known to be earthed. You don't need to power-on the Tascam machine, just the PSU.
It would also be interesting if earthing solves/reduces @Craig Smith's original problem.

 

[Craig Smith]

Thanks Phil. I do not have a multi meter.
I have tried a ground wire on the DP-32 using the GROUND connector, and I've tried connecting it to just about everything I can find in the room with no results.
I've tried uploading a video to the Attach files, to show what's happening, but even at 640 x 360 14.4 MB I get a message saying "The upload file is too large for the server to process".

 

[Phil Tipping]

Thanks for the update Craig; it was worth a shot but I'm out of ideas for now.
Re. video, we usually recommend uploading it somewhere else and just posting a link to it.

 

[-mjk-]

The diagram shows why you get a 1/2 of mains voltage measurement: the audio ground is tied to the negative side of the bridge rectifier though a cap.

Are these electrical 'tingles' dangerous?
No. The 'tingles' or mild electric shocks are not unlike the static electricity zaps you receive when getting out of a car in dry weather or walking on nylon carpets then touching a metal door handle. Whilst they are alarming, the appliance is not faulty.

I bet if one were to bring a DP-32SD in the bathroom, plug it in to the mains, and touched the outer sleeve of an RCA jack with wet feet on a tile floor, one might have a different opinion!

Static shocks are momentary discharge spikes and not continuous current. I'm not sure that I agree with this illustration or the conclusion that it's not potentially "dangerous" as I see no current limiting except by the bridge rectifier. I know it's Panasonic, but still.

 

[Phil Tipping]

I don't think it matters as the current is so small. As they say "It's volts that jolts, but mils that kills".
Have you tried a multi-meter on any of your 'floating' gear?
Seems it's also common on some laptops with double-insulated PSUs:

Touch current and Surface devices - Microsoft Support

Learn about what touch current is and how it relates to Surface devices and charging.

support.microsoft.com

Notebook “Tingle” Sensation: What's Going On? | Dell

Several weeks ago, a user from notebookforums.com reported concern about voltage. That post prompted other stories from folks like Engadget and

www.dell.com

https://pcsupport.lenovo.com/gb/en/products/monitors-and-projectors/lcd-monitors/lenovo-li2264d-lcd-monitor/solutions/ht505170

 

[Old No7]

I bet if one were to bring a DP-32SD in the bathroom, plug it in to the mains, and touched the outer sleeve of an RCA jack with wet feet on a tile floor, one might have a different opinion!

Interesting thread.

Thankfully, the above quote is not a Best Practice for studio quality results with the DPs....

Although, we once DID put a Leslie Speaker into a tiled bathroom to record it -- it was wild, weird, or wonderful depending on where we put the mic.

Old No7