Peva at Bose suggested I post this. He is sending it up to the engineers for further investigation.

I plugged in my new PAS/B1 system directly into my Kurzweil PC2 for a test drive. Beautiful, even sound. Love it.

Tried the remote while playing a fairly delicate piano patch and got what sounded a lot like a dirty pot. (volume control) primarily on the channels and a bit on the master. Called Bose and they sent a new power unit the next day. Best service anywhere, anytime!

Replaced the power unit, remote and cord. Ran the PC2 demo "Fandango" and the stepped sound was gone. I thought the problem was solved. Ran the piano demo (Flaxen Hair) and the stepped sound was back. Put the original power unit back and the same results. I was testing the PAS originally with a piano score I was working on which was similar inlevel to the PC2 piano demo.

Conclusion: A lighter, more delicate sound will produce a stepped or zippered effect when increasing the volume on the remote, especially on the channel control. (Sort of like a bad edit of a MIDI volume message.)

My guess is that the PAS software does some kind of attenuation of the signal to evaluate the level (but I know squat about that kind of stuff - so I am guessing). If the level is strong, no problem, but a weaker level will (or should) produce the "offending" sound.

This should not be much of a problem unless you want to change levels in performance, and then, only if you are at the critical weaker signal level.

Anyone with a PC2 or a light sounding patch or instrument may want to verify this. Again, it is not enough to warrant a return of the power unit (I wish I knew that before Bose went to the trouble and expense). But hopefully, it is something that can be addressed in a future software update.

As always, your comments are most welcome.

MM
Original Post
quote:
Originally posted by Oldghm:
MM,

Click on "FIND" and type in "lag or latency" to see if what you are hearing is the same as discussed in that thread.

Oldghm


Thanks, Oldghm. Does indeen sound like the lag reported earlier. But only on low levels. A strong signal will not reporduce the problem, or maybe it is less noticable.

I'm surprised they sent me a new power unit so quickly. Frankly, I can (and do) accept it as an expected performance issue. I even asked that question specifically, but was told that they never heard of it. Hmmmm.... My guess is that maybe they didn't,or it is one of those things that the guy who answered the call wasn't familiar with it.

Oh well... the replacement power unit is on its way back home and I don't love my PAS any less for the wear Smile

Thanks again for the info.
Michael,

Thanks for the heads up. I'll try and reproduce it here at home today. I've never experienced this but we're always learning.

Can you post your remote settings (including the trim level)? I'm going to try and recreate the thing you're describing for myself. I play guitar so I can play with a very light touch and/or use the guitar's volume control to try to mimic what you're doing on the piano.

Steve
Michael is correct, there are two design related issues that come into play here. The reason why nearly nobody knows about is, is that rarely ever anyone notices it.

1) The remote has a certain amount of latency. It takes a moment from the time you turn a knob until the setting actually takes effect. The exact time depends on the circumstances, but it's always less than one tenth of a second which is indeed barely (if at all) noticable.

2) The Channel 1 and 2 Volume controls produce a very slight "zipper" noise when they change between different volume setting. That noise does not affect the tone controls or the master volume. The technical reasons for that are complicated, but I'm happy to explain it, if someone is interested.
Anyway, the "zipper" noise only occurs when you actually operate the control, so it doesn't occur while playing unless you play and adjust at the same time. If you need to do that (e.g. for a fade-out) and the zipper is audible and objectionable, you could maybe use the volume control on your instrument or the master volume on the remote.

Again, most people never notice these issues in the first place and if they do, it's rarely a problem of any sort.

Hope that helps
Hilmar
Thanks Steve & Hilmar.

For Steve: My settings were pretty basic. 12:00 for the trim; 12:00 for the master and ran the channel up to about 10:00. But the setting don't seem to matter. It'll do it at most settings whenever the channel is adjusted up or down.

To Hilmar: Perhaps I listen too critically to everything. Can't really help that Smile Earlier in my career I tuned pianos for extra $$$ (still tune my 7' Yamaha and several pianos I gig on). Also worked with/under some extremely critical ears and learned to tune into every little nuance. As a composer, conductor and sound dedsigner, I also am require tohear everything, however small. It is our curse as musicians and as the PAS system is so clean, it allows you to hear such subtle variances.

As previously stated, I readily accept and understand that the PAS architecture creates the zipper effect. Some of the early MIDI software programs were also similarly cursed, but you learn to work with it.

What surprises me is that the phone tech support crew at Bose actually sent me a replacement base and remote! Very appreciated, but totally unnecessary and a waste of time, energy and resources. EXCEPT - if this brings the matter to the attention of the tech support team, then perhaps it was worth sending the base unit out this one time. Maybe it'll be the last? Smile

Anyway, I am happy to 'lend you my ears. I come to praise the PAS, not to bury it' (to paraphrase Shakespeare).
Here goes then, don’t say I didn’t warn you Smile

Nearly all controls (presets, tone, master volume, system controller, etc. are done in software using Digital Signal Processor). The notable exception are the Channel 1/2 volume controls. That’s because 1 and 2 do have an insert loop. The insert loop sits after the trim (so it provides good solid line level) but before the signal processor (so you can apply presets and tone etc.). Now if you connect something with a lot of gain to the insert loop it would be possible to overdrive the input of the signal processor even though the trim is perfectly fine. To deal with that, we added another (hardware) volume control after the insert loop but before the signal processor. That’s the channel volume. But since the knobs sit physically on the remote, we had to use a programmable volume control chip instead of an ordinary pot.

The particular chip we are using changes volume in roughly 1 dB steps. Whenever it switches, puts a small discontinuity in the audio waveform and that’s the “zipper noise” that you are hearing. There are other chips that smooth out the step or switch only while the audio is small, so there isn’t any audible zipper. However, these chips tend to be a little noisier (while not switching) and we opted for having the cleanest possible signal for “normal” operation at the expense of slight zippering when operating the volume control.

Welcome to the wonderful world of engineering trade-offs Wink

Hope that helps

Hilmar
quote:
Originally posted by Hilmar-at-Bose:
Welcome to the wonderful world of engineering trade-offs Wink


As my shop teacher used to say, "You do something to gain something to lose something."

As racers say, "If it broke, it wasn't strong enough. If it didn't break, it was too heavy."

As the software people say, "Good. Fast. Cheap. Pick any two."

Thanks, Hilmar. This is good to know.

Mike

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