C-24 Monitor section

[darla]

McMasters wrote: So I would tend to believe that the problem is with the pot itself. Does the pot have too much resistance or is there an overly aggressive resistor in the monitor path? (ANY TECHS OUT THERE??)
Since DIGI IS STONE WALLING everybody.
McMasters-Have you spoke with Digi on this? (I'm NOT taking sides!!) I did yesterday & they were straight up with me about the problem. it's not a simple pot (I believe it digitally controlled, you can hear it "step" thru volume changes quite easily). I initially thought it might be a simple change of resistor somewhere in that section. As I understand it, an EEPROM fix is needed & is "on the way" whenever that is. I was asked to check back in a few weeks. But they are aware of it & they know we are [img]images/icons/grin.gif[/img]

[Rollerex]

Ok well it's been about a week now that Digidesign has not responded to this thread.

So digi i'll put it to ya point blank.

Do you think this monitor section is properly designed?

If not what will it take to make it work properly?


Many potential buyers read these message boards.
You lack of resoponse is a statment in itself.

I mean when it gets to the point where there is a actual name for this problem (LOS) or low output syndrome.
I think you (and me) have a problem

[McMasters]

ummmm [img]images/icons/shocked.gif[/img]

[McMasters]

If the eeprom is the problem. Hopefully it will be field programable, or field replaceable.

--- EEPROM --- Electrically Erasable Programmable Read-Only Memory

Some clues to how eeproms work:

Analog audio output level calibration
A 1000-Hz sine wave at –18dBFS (+4dBu) is generated by the analog audio outputs and then fed to the calibrated audio inputs. An output gain compensation is applied by software to make sure the grabbed signal corresponds to a –18dBFS amplitude signal in memory. This step is repeated for each of the four analog audio outputs. The values of the output gain compensation are stored in the DigiSuite card's calibration EEPROM.

The same procedure is repeated with a 600-ohm load present on the analog audio outputs. The output gain compensation values using a 600-ohm load are stored in the DigiSuite card's calibration EEPROM.

Taken from http://www.matrox.com/videoweb/suppo...udio_tests.htm

If anybody knows more about eeprom technology. Please post.





Analog audio output level calibration http://www.matrox.com/videoweb/support/ds/specifications/le_audio/le_prep_audio_t ests.htmIf anybody knows more about eeprom technology. Please post.calibration EEPROMcalibration EEPROM

[McMasters]

Just read about the 18db of headroom the 888's have.

Would it be possible to calibrate the outputs hotter? (temp fix)

Just curious. My system should be in by the end of next week. I would like to get a handle on this problem.

[AvidCS]

Control|24 Monitor Section Output Level

Some customers are experiencing lower than desired output level from Control|24's monitor section. Control|24 uses a digitally controlled analog gain circuit. This allows us to set the output "taper" of the pot to whatever we want because it's actually smoothly switching with 0.5 dB gain steps. This also allows us to maintain a matched output level with 0.1 dB matching between channels throughout the adjustment range. The gain and control taper were chosen based on empirical listening tests done during the design phase of the product. This allows the monitor pot to remain positioned within the "sweet spot" between nine and two o'clock. The levels were selected to accommodate a wide variety of powered monitors and power amplifiers at a broad range of listening levels.
The output pot levels were tested with a wide range of powered monitors and amps including Mackie 824s, Genelec 1029s and 1031s, Meyer HD-1s and Anchor monitors. Crown, Bryston, Yamaha, Hafler and JBL power amps were also tested. We chose a nominal operating level that would allow this group of products to operate within a normal range of adjustment (avoiding the need to turn their input trims way down while letting the monitor pot sit in the "sweet spot.")
Note that not all powered monitors and power amps have input level trims (the Meyer HD-1s are a good example). Most of you should have no problem with the output level of your Control|24. However, a select group of products (JBL LSR speakers are one example) cannot be driven to full level. (These speakers do not conform to the de facto level standard used by most powered monitor and amplifier manufacturers.)
In conclusion, most of you should not encounter problems with the operating level of the monitor section of your Control|24. You may have to adjust the input level controls for a power amplifier, but usually not your powered monitors (with the exception of the JBL LSR series).
If you are experiencing problems that cannot be rectified by adjusting your equipment, please contact Digidesign Customer Support. A firmware update is available that will add 10 dB of gain. (However, this update does require the unit to be returned to Digidesign.) As already mentioned, most of you should not require this at all to get good results.

Bob Langlie
Director of Customer Service
Digidesign

[PTstress]

Well at last a response.

Digi, if I read your response acurately, you are saying you set the output level of C24 based on what sounded ok to you and not based on a +4db spec as claimed in your C24 spec sheet. Your comments based on certain amps not performing are absolute drivel and somewhat insulting to those of us who can measure what the C24 actually puts out. This has no bearing on what monitors the C24 is connected to post output so please do not try to ******** us. It is a fact that the C24 puts out 19db less than an 888 regardless of anything taking place outside your board. A +4db balanced amp expects a +4db balanced signal - end of story.

It looks to me that your efforts were concentrated on the assumption that most people use powered monitors. We all know that those monitors are often a law to themselves as far as what kind of signal they expect, however that is a purchase decision for the customer. You should have the courage to admit the error rather than try and assert that only a few of us will be unhappy about this when it is clear that all C24s have been not been built according to the spec claimed.

Having said that, I am of course pleased that a solution has been found and you can be assured that I will be talking to tech support in the uk about getting things sorted.I do question wether a 10db hike is enough to achieve true +4db operation though.

For me this has been a costly exercise and it has further confirmed the need not to take a manufactures word for even the most basic claims on a spec sheet in future.

[ July 21, 2001: Message edited by: PTstress ]

[Dave Lebolt]

There is certainly no intent to be untruthful here. We stand by the point that most customers will not need to change update their units. I'll take each of your points in turn and try to respond:
<UL TYPE=SQUARE>

<LI>Control|24's monitor section was set up not just for powered monitors, but also for professional power amplifiers. The input sensitivities for most of these products consistently fall in about the same range: between 1 volt and 3 volts AC will yield full power output (driving the power amp or powered monitor to clip).

I think some of the perceptions about this issue stem from confusion about the difference between "operating level" vs. "input sensitivity."

When a manufacturer specifies the operating level for a piece of gear, they are generally talking about the "nominal" (read "normal") level for the device, not the "maximum input level before clip." "Nominal" in most cases on pro audio gear is the "+4 dBu" level standard that we are all familiar with. It represents a reference voltage level of 1.23 VAC. For example, this is what is what the "zero" level on a VU meter (not a digital peak meter) on a pro tape machine represents. However, the peak transients the input circuit will deal with on a device (or what the output circuit will supply) are often over 20 dB higher than the nominal level. Thus it is normal for professional audio equipment to handle peak levels at +24 dBu or higher (which is far closer to 10 volts than 1). The ability to accommodate these peaks represents the headroom of the device before clip.

Professional audio power amps and powered monitors generally do not use this input sensitivity standard. Instead, they can be driven to clip by what would be the nominal level on most pro audio line level devices because they generally clip their outputs at below 2 volts (which is far below the +24 dBu I described earlier). This is why most any console on the market does not offer gain above unity on the output... it would just clip the power amplifier or powered monitor following it, and you'd have to keep the level control turned way down all of the time.

The output level as supplied on the C|24s shipped up until now had been -10 dB below unity. This means that when the level control is turned fully clockwise, most power amps or monitors can be driven to full clip (putting out their full level). As we said in the original post, the output level was optimized so that at most "loud" listening levels (SPLs in the mid 90s), you could position the control at around "2 o'clock."

<LI>The post that claims that C|24s put out -19 dB should be incorrect (unless there is something additionally wrong with that unit). Consider that C|24s original silkscreened markings for the monitor level control have a "0" mark at around the 2 o'clock position. This level does not represent "full output" (the silk screening is not correct, and will be updated on future units). At maximum output (with the control turned up fully to around 5 o'clock), level should be -10 dB below the input device's level, not -19 dB.

<LI>As to the question about whether the +10 dB level change is adequate: with the addition of the firmware PROM change, the output level of the monitor section will pass unity gain (level in = level out).

<LI>It is true that the specification sheet should have been updated on the internet (or in printed materials) to reflect the newer specs. We're sorry that this has not occurred sooner. But this is one of the reasons that manufacturers place the text "Specifications subject to change without notice" on their data sheets. It's not an attempt by the manufacturer to deceive a customer, but it's a fact of life that many times as products are brought to market (and the rushing that occurs to get it all done), these materials are created prior to the final changes that occur when releasing a product to production. [/list]As we stated in the original post, most pro power amps or powered monitors can be adjusted (or left at the levels delivered from the factory) and work well with the C|24 with its original firmware. We're offering an update for all customers who have a problem, but most of you should not have the problem... For those of you who do, we'll update the unit, but we'd like you to contact Digidesign Customer Service first to make sure it's not a setup problem.

Dave Lebolt
VP, Product Strategy
Digidesign

[ July 21, 2001: Message edited by: Dave Lebolt ]

[ July 23, 2001: Message edited by: Dave Lebolt ]

[Rollerex]

Hey ,
thanks for your response in this matter.

I use a pro-control as well and it seems to have the proper amount of gain in the monitor section. I agree with PT stress that it should be unity gain. You bet I want this upgrade.

This brings up another sticky point.

Do any of you want local service for Digidesign?
I live in Los Angeles and Its long overdue here

[Monumental]

Hi there,
I recently changed from my digidesign cable harnesses to a shorter and cheaper DSUB harness for my monitors. Guess what, the monitor level on my system dropped approximately 19 db. Is the monitor section of the C24 using standard DSUB wiring? Could this be the problem?