Why would there be degradation bouncing tracks on DP-008EX?

[LAMATL]

Curious to know why, being digital, I can't bounce up to eight tracks to two stereo tracks -- once, twice, or even three times -- without noticeable sonic degradation? I thought that was the whole idea of recording digitally? Along these same lines, more than once I've read the suggestion that it's preferable to export the individual tracks and mix them down externally on a computer to avoid degradation. What's the difference? Bit rate? Something else? I'm not far enough along to test this for myself but it seems, in principle, to be a warning carried over from the portastudio cassette days and not relevant to the current generation of products. Am I wrong?

 

[Phil Tipping]

There should be nothing noticeable. What sort of degradation do you get, and are you altering the gain or using any FX or EQ in the bounce? I did a 19 x bounce experiment on a dp32sd at 20m45s in this video - just a simple bounce with no level changes, FX or EQ, and couldn't hear any difference.

 

[Emma Boyd]

I've been having the same issue. Even when I bounce just two tracks together, there's a significant drop in volume. Very confusing.

 

[dctdct]

For this device, the BOUNCE function is similar to the MIXDOWN function. The playback LEVEL settings of the source track as well as the MASTER LEVEL will have an impact on the final bounce track recording level (see also manual page 25). Depending on your source and bounce track level settings the bounce result will vary in volume.

There should be nothing noticeable .../... I did a 19 x bounce experiment on a dp32sd at 20m45s in this video - just a simple bounce with no level changes, FX or EQ, and couldn't hear any difference.

Will have to double check your video, @Phil Tipping , how you keep exactly the same overall level on the bigger portastudio series.

 

[Phil Tipping]

Yes you're right, there are 2 levels to consider. On the DP-24/32, you can see the playback level of the source track and the recording level of the destination track so it's easy to line them up by eye.
The 'gotcha' with the 24/32 is the drop in level when bouncing from mono to mono - the bounce bus is stereo and the machine only uses one side for the mono destination, so you either have to pan the source fully to one side, or increase the level to compensate.
Either way, my point was that there should be no 'sonic degradation' as mentioned by the OP, so maybe there was an effect somewhere in the path?

 

[Emma Boyd]

That's good to know that both the track levels and master levels will affect the volume. The last time I bounced tracks, I experimented for quite some time and although I didn't notice any discernible degradation in quality, I'd say the volume dropped by about half so I eventually gave up. I must go back and have another go. Thanks for your video, Phil.

 

[Emma Boyd]

Yes you're right, there are 2 levels to consider. On the DP-24/32, you can see the playback level of the source track and the recording level of the destination track so it's easy to line them up by eye.
The 'gotcha' with the 24/32 is the drop in level when bouncing from mono to mono - the bounce bus is stereo and the machine only uses one side for the mono destination, so you either have to pan the source fully to one side, or increase the level to compensate.
Either way, my point was that there should be no 'sonic degradation' as mentioned by the OP, so maybe there was an effect somewhere in the path?

I've experimented further with bouncing tracks on the DP 008EX. This time I was mindful of the track volumes as well as the master volume which has helped the issue to an extent, so thank you for that.

However, I'm noticing that when a source track is panned at all to the right, I can barely hear it on the destination track (it sounds faint and tinny even when the volume of the source track is near max). I'm wondering if this is a result of what you describe above i.e. the stereo bounce bus vs mono tracks? Is there any way to bounce mono tracks together whilst retaining the desired left and right panning? Or is my only option to pan both source tracks all the way to the left? Thanks.

 

[dctdct]

I had a second look at the block diagram and I might have seen the source of confusion also in our Pocketstudio (as mentioned already above by @Phil Tipping for the Portastudio mixing down single mono tracks).
Let me depict what my knowledge is by today: Keeping FX aside, if you use BOUNCE instead of MIXDOWN for a set of tracks (1 to 8) particularly the target track(s) are diffent. The LEVEL, PAN and REVERB are the same controls and react equally. What is different: In the bounce case you mixdown to one or two of the multitracks (1...8); in the second case you allocate the mastertrack (and overwrite the old one, if present).
Coming from your source track, after the LEVEL and PAN controls, the odd tracks 1,3,5,7 are summed into the L channel of the stereo bus; the even ones 2,4,6,8 into the R channel. (If you used the REVERB control, this will next be added into both channels). Next is the stereo MASTER LEVEL control. The L+R output from there will go back into the activated L and/or R target track.
If you pan something out to one side, you will indeed reduce the overall stereo volume by 50 % if there is only this one track in the mix fed to the stereo sum. I did a short test with Tr1= synth rythm and Tr2=synth lead. To keep them separated I panned Tr1 completely to L and Tr2 to R for the bounce target Tr7+8. This worked as expected but the mix didn't sound very natural. Next I bounced both 45° L+R with the PAN control and this gave musically a far better mix then the hard panned one. Could this also be a part of your problem?

 

[Emma Boyd]

A few interesting points there, dctdct. Thank you for all your thoughts there.

When I'm bouncing tracks, I never pan the source tracks more than 45 degrees left or right - in fact it's usually just a touch to the left or right, so I don't think that can be the problem. What is standing out for me from your description however is:

A) the fact that the even tracks go into the R channel and odd ones go into the L channel (I did not know that!)
and B) that I only ever try to bounce two tracks into one track (not into two), so essentially I'm going from mono to mono.

I think the key to my problem lies somewhere within these two points. If I understand correctly, keeping the even source tracks panned somewhere to the right and keeping the odd source tracks panned somewhere to the left when bouncing down will help with the degradation and bouncing down to two tracks instead of one with also help with the issue?

 

[Mark Richards]

....the odd tracks 1,3,5,7 are summed into the L channel of the stereo bus; the even ones 2,4,6,8 into the R channel.

If I understand correctly, keeping the even source tracks panned somewhere to the right and keeping the odd source tracks panned somewhere to the left when bouncing down will help with the degradation and bouncing down to two tracks instead of one with also help with the issue?

Initial Tracking
When recording initially, the DP-008EX Input "A" ASSIGN defaults to the Odd Tracks, and Input "B" ASSIGN defaults to the Even Tracks. These Input "A" and "B" ASSIGNs can be changed as needed, and only apply to the initial tracking. (OM pages 15 & 44).

In General for a Stereo Bounce and Stereo Mixdown
(Note: Unlike most other MTR systems, the DP-008EX can bounce all 8 tracks simultaneously - OM Section 7, page 51)

• Once you've recorded your tracks (up to 8 for a stereo Bounce or stereo Mixdown with a DP-008EX), the source (recorded) Track Pan Knob and Level Knob, along with judicious use of EQ and FX, are used to achieve a balanced stereo mix.

• This is true for both a two track stereo Bounce and for the Mixdown (which is always 2 track stereo).

• At the Center position (as Phil pointed out), the source Track recorded signal is distributed equally. As the Pan Knob is adjusted left or right, the volume level of the Pan signal increases by up to 3 dB on one side of the stereo field and decreases by up to 3 dB on the other side of the stereo field, thus altering the position of the signal's left/right image in the sound stage. That's a 6dB differential full left to full right, which is a halving (or doubling, depending on perspective) of the signal voltage.

• A source recorded Track panned full left or full right in a stereo Bounce or Mixdown will always be about 3dB louder than when the Track is panned to the Center, independent of the Track Level Knob setting and the Master Level Knob setting. This is normal and expected.

In General for a Mono Bounce

As I recall, with portastudios,

• When Bouncing multiple previously recorded source Tracks to a single mono Track, all source Track Pan Knobs should be set full left (to take advantage of the 3dB gain and place focus on the source Track Level Knob to establish relative levels).

• A previously recorded source Track Panned Center in a mono Bounce will provide a signal, and it will always be 3dB lower on the Bounce Track independent of the source Track's Level Knob.

• A previously recorded source Track panned full right in a mono Bounce will NOT be bounced because "full right" turns the signal off and there's no signal to be sent to the Bounce Track.

• Portastudios can make use of the Right side of a previously recorded source Track's Pan Signal in a mono Bounce, so long as the Pan Knob is NOT set full Right (which turns off the signal).
  • In doing so, the right of Center setting of the source Track Pan Knob impacts the source Track's volume level going to the Bounce Track, independent of the source Track's Level Knob.
  • A source Track panned partially right of Center in a mono Bounce will be lower still in volume level than a Center setting, independent of the Track's Level Knob.
  • The same is true in the opposite direction for the source Track Pan Knob set partially to the Left.

This is why best practice suggests panning the source recorded Tracks full left when performing a mono bounce.

 

[Emma Boyd]

That's so helpful, Mark. I've had a lot more success bouncing tracks over the weekend in this new knowledge! Thanks.

 

[dctdct]

Initial Tracking
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• At the Center position (as Phil pointed out), the source Track recorded signal is distributed equally. As the Pan Knob is adjusted left or right, the volume level of the Pan signal increases by up to 3 dB on one side of the stereo field and decreases by up to 3 dB on the other side of the stereo field, thus altering the position of the signal's left/right image in the sound stage. That's a 6dB differential full left to full right, which is a halving (or doubling, depending on perspective) of the signal voltage.

• A source recorded Track panned full left or full right in a stereo Bounce or Mixdown will always be about 3dB louder than when the Track is panned to the Center, independent of the Track Level Knob setting and the Master Level Knob setting. This is normal and expected.

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Thank you for this detailed information. Because I didn't found it in the manual nor in the schematics, I'm very curious where this 3 dB difference comes from. Can you enlighten me please?

 

[-mjk-]

Basically if the signal is split (divided) by 2 paths the level will drop. Panning to the right or left puts the full signal on that bus.