Interesting ' problem' with my Tascam DP-02

[TascamJimi]

Hey folks, I've come here with some really silly questions..... that have been answered and not laughed at so....going to try another one....and this is definitely a strange one...

I recently recorded an arpegiated ( sp?) guitar line that last about 4 minutes....upon playback, at about the 2 minute mark, it starts to slow and go out of tune... sounds exactly like batteries dying in a tape deck...very strange..... as a test, on another track I recorded the same pattern, just using a looper pedal instead of playing the part straight through to eliminate poor picking technique the longer I played......... it does the same thing...starts out fine... then all of a sudden it starts ' dragging' and going out of tune with itself. I know that technically this is impossible with digital..... (or is it ?. )......... but my ears are telling me otherwise.... no modulation effect on the guitar...just bone dry....so I ruled that out....and it's just a single guitar line ...not doubled or anything...
Has anyone ever experienced this ? I have a 5 track sub-mix on tracks 7/8 and they play fine, all the way through.... I can't figure this one out...

 

[Slouching Raymond]

The timing will all come from a quartz crystal, so it ought to be accurate.
I was once told that over a long time they are accurate, but can wobble about a bit.
They are actually electrical/mechanical oscillators, and may operate in more than one mode due to geometry.
The only other thing I can think of is how the sampling frequency gets divided down.
It may involve spikes instead of square waves, which may not register at times.

 

[TalismanRich]

I don't have a DP02, but I've never experienced that with any of my digital recorders (2 Yamahas, 2 Zooms, 1 Tascam interface).

Is it a gradual slowdown, or an immediate change, which might indicate a change in sample rate happening somehow?

 

[TascamJimi]

@Slouching Raymond That was interesting. Went straight over my head but.... I'm going to Google what you mention and see if I can get more information....this unit is indeed 20 years old so age might be an issue.... I just find it odd that the sub mix plays fine..... but the arpegiated part is slowing down...

@TalismanRich It's pretty abrupt... definitely noticeable... maybe over the course of a measure or two ...You can definitely hear it happening when it starts....I'm going to add another guitar part on an adjacent track , played the same way..... just too see what happens....It would totally baffle me even more if that track plays fine !!

I know it's a total long shot ( again considering my sub mix on 7/8 plays fine ) but lately it's been getting really hot in that room..... 85 + degrees.... wondering if that might be an issue...I crank the a.c.,when I start working....... but maybe the unit was struggling while actually RECORDING the part and now it's just stamped on there and it's actually not a playback issue...

This one really has me stumped... I even asked a friend to listen to the track w/o saying anything.... and he picked up on it as well.... ' Why does it sound like your batteries are dying ?' !! I sure find / have some very strange issues with home recording !! Still love every minute of it...

As always , THANK YOU for trying to help out..... This forum has helped me tremendously in getting back into recording.

 

[TalismanRich]

Can you post a short section where the timing changes? If you render to a file, is the tempo/pitch change apparent on playback?

I doubt that temperature is an issue... most electronic gear is good at normal temps. A DP02 should function perfectly fine at 85 or 90 degrees. People do onsite recordings outside in the summer all the time.