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[Lee Buckalew]

Quote:

One adapts to this y setting the manual preamp gain controls so that the channel strip gain control can cover any reasonable eventuality.

This type of approach to gain will work well for the same player from song to song such as compensating for patch changes from a keyboard, etc. but it is not a good idea for different players, different instruments and different singers from week to week or service to service as it means that your S/N ratio will be very compromised quite quickly.
Same type of reason we don't just leave mic pads on all the time in case it may be needed at some point.

His,
Lee Buckalew
Pro Sound Adice, Inc.

[George S Dougherty]

Lee Buckalew wrote on Thu, 22 April 2010 15:30

This type of approach to gain will work well for the same player from song to song such as compensating for patch changes from a keyboard, etc. but it is not a good idea for different players, different instruments and different singers from week to week or service to service as it means that your S/N ratio will be very compromised quite quickly. Same type of reason we don't just leave mic pads on all the time in case it may be needed at some point. His, Lee Buckalew Pro Sound Adice, Inc.

The SAC community has found this typically isn't really a problem.  The preamps being used are of a good enough quality that you have decent headroom without introducing noise.  There are some types of sources that will vary from person to person and instrument to instrument (active vs passive bass pickups into a DI most notably), but it's not that big a headache.

I shoot for -18-16db on the meters as an average input level and the standard gain positions I have for vocals, drum mics, guitar mics, various DI's, etc. typically get me within 10db of what I need.  On vocal channels I run quieter vocalists with 4-8db of digital gain.

It really comes down to budget.  Would I like to have fully recallable preamps?  Sure I would.  Can I live without them?  I do every week.  Our church shares with another church and I reset half the gain settings every Sunday (onstage even, I have to walk back and forth!)

SAC has made digital mixing a possibility in my and many other cases.  Sharing SAC between two congregations and having to recall a few gain settings is far better than any other option we had within our budget range.

Give me a $3-4K option that will allow for:
Control by FOH and Monitor engineers with dedicated solo busses for each.
Multi-zone FOH output
At least 8 stereo and 8 mono monitor mixes,
4-5 band parametric EQ plus low and high cut on the EQ (yes, I use both cuts on a cajon port mic),
Gate and Compression on any channel with hi-low side-chain filtering and alternate channel keying (reverse gate is a handy plus)
Simple channel labelling
8 Matrix Outputs sub-mixing all inputs
Support for widely available studio quality plugins
Remote control from multiple low-cost devices for remote mixing and personal monitor mixing (yes, I've setup the console for a last minute emergency from 100 miles away over VNC)
Allows for modular use as a small portable 8-channel mixer or larger 24+ channel concert venue desk with the same channel and routing features
Has preamps that sound noticably better than those in an LS9 or M7CL
and has recallable preamps

Until my budget expands a hundred fold or something like that is available on the market, I'm happy to live without recallable preamps to get the rest of the features on that list.

I rolled into a church last week for a concert, strung no cables across the sanctuary and mixed FOH sitting on the back of a padded chair in the middle of the congregation instead of against the back wall in an enclosed sound booth.  The non-recallable preamps worked well enough for me.  Recalled the band's previous session, did a line-check and reset gains.  Made a few minor tweaks to monitor mixes and we were ready to go 10 minutes after I plugged in the last mic cable.

I'm taking the same software license, same mix session and a different 24-channel hardware configuration (~$500 worth of additional gear) in a backpack and small 6U rack case to Siberia next month.

Those are just a few of the things I love about SAC.  If you couldn't tell.  

[Lee Buckalew]

George,
I agree with you to some extent but it is not a set it and forget it proposition.
I am talking about needing to pay attention to things like;
The bass player this week plays direct out to a DI via a bass with a passive pick up, next week the player plays through an amp with an active direct out built into the head outputting peaks of +15 or more.  I really need to adjust the preamp for this wide of a discrepancy.
The same thing often happens with changing out keyboards and some other items (this week there is a trumpet on the mic that last week miced a violin).

I am aware that, within reason, this can be a great benefit for a digital system, but it does not answer all needs to actually adjust the analogue preamp input stage and maintain some semblance of proper gain structure.  I don't want to give people who may not know better the idea that they won't need to adjust their pre's.

I routinely mix on everything from small Allen & Heath's and Midas Venice to Midas Heritage in analogue and Yamaha 01v96v2 to Euphonix S5 Fusion in digital.  With a number of hybrids (like the SSL Duality) in between.  Gain structure is still important.  I can't make up for signal to noise ratio problems later in the chain but, you are correct, with pre's that are quiet enough (this varies by application) you can maintain quite a large amount of headroom.  In fact, most recording engineers will tell you that you should not allow your digital peak level to exceed somewhere between -6 and -9 dbfs (some will say to leave even more room than that) in order to avoid intersample clipping.

His,
Lee Buckalew
Pro Sound Advice, Inc.

[Brad Weber]

I think things may be getting confusing for some people.  For one thing, we are talking two different gains, the analog gain/trim is before the A/D conversion and digital gain is after the A/D.  While the digital gain may be able to compensate for general level issues, it cannot fix problems that occur in the analog domain.  Adjusting the digital gain is not a solution if you are clipping the analog input or the A/D input or if the analog signal is noisy, in effect the damage is already done.

Also, because we are discussing analog and digital signals I think we need to be careful about the numbers used.  For example, George noted running -18 to -16 dB on the meters while Lee noted that some people recommend keeping the peak digital levels below -6 to -9dBFS.  So how much headroom does that indicate George has?  If he was referencing peak dBu levels he might have 23 to 36 dB of headroom (assuming +16dBu to +24dBu maximum analog input levels).  If George was referencing peak dBFS then he might have just 7 to 10dB of headroom.  And if he was referencing some type of average or time weighted dBFS levels he might have little or no headroom.  That's a pretty wide range of what the levels actually represent.  The point is that without referencing what dB are being discussed, and in the case of metering the meter ballistics, and having an idea of how those relate, then the numbers have little meaning.

In Frank's application I envision two specific concerns with not having recallable analog gain/trim for the preamps.  One is sort of what Lee referenced, that of varying or unknown input levels.  Do you have rehearsals where everyone who might speak or perform is involved?  Or might you have situations where there are unknown or surprise sources?  I think of things like the last minute guest pastor or the congregation member family ranging from the shy, sweet little girl to the outgoing, booming Dad all taking turns reading scripture.  Presetting levels for regular, practiced sources is one thing, presetting them for an unknown is another.

The second concern has to do with the comment regarding the school using the system between service related uses.  If they make any changes to the preamp input gains those changes will not be tracked or compensated by the SAC presets or system.  It seems like both you and they will have to chart and verify the preamp analog level settings just as you would for the gain/trim settings on an analog console.  You might even find it useful to 'zero out' the preamps between uses.

[Arnold B. Krueger]

Lee Buckalew wrote on Thu, 22 April 2010 22:30

Quote: One adapts to this y setting the manual preamp gain controls so that the channel strip gain control can cover any reasonable eventuality. This type of approach to gain will work well for the same player from song to song such as compensating for patch changes from a keyboard, etc. but it is not a good idea for different players, different instruments and different singers from week to week or service to service as it means that your S/N ratio will be very compromised quite quickly. Same type of reason we don't just leave mic pads on all the time in case it may be needed at some point.

Given all of the consoles in use that work this way and are used sucessfully with multiple players and keyboards, it is safe to say that many concerns are related to some being hyper-cautious.

For example, I work with 2 pianists that have significantly different touches - good for about 8 dB gain variation between them.  Even worse, I work with 3 bass players that need more like 15 dB gain change from loudest to softest.

If you actually look at the gain staging through a modern digital console, the real-world compromises in SNR due to changes in digital gain are minimal.

I've been hearing people raise concerns for years about SNR loss due to gain changes in the digital domain. If you actually do the math or better yet do the work, this usually seems to turn out to be more concern than actual compromise.

The biggest problem I see is the extra confusion that may be caused by having two gain controls that address pretty much the same need. OK, you have to think this one out. Once you do, no sweat.

[Lee Buckalew]

Arnold,
I am not talking about signal in the digital domain.
As long as you are starting off with a 24 bit system (or better) then being cautious once in the digital domain is not too much of a problem.

At the analogue preamp, that is a different story.  I have some keyboards that I have to pad by 40dB compared to others.  You really don't want your analogue mic pre's (and they are all analogue mic pre's unless you are running digital mics) to be set with 40dB to 50dB of headroom.  You will end up with noise.

To reiterate Brad's comment, you also can not turn down the digital gain staging and stop analogue mic pre clipping.  This has to be done at the analogue pre-amp.

Again, not trying to say this is a bad idea but it is not a set it and forget it scenario.  As long as there are rehearsals where you can get your analogue pre levels set, you are pretty safe.  If there are not, and if you have unknown players/singers or others who use the system during the week then this may not be the best idea.

My church never rehearses with the sound crew for Sunday services.  It's always cold.  There are often last minute player changes.  Also, we load in and out every week, a really good chance to have knobs get changed accidentally.
This would not be a good candidate for leaving analogue pre's set and utilizing only digital gain.

His,
Lee Buckalew
Pro Sound Advice, Inc.

[Arnold B. Krueger]

Lee Buckalew wrote on Fri, 23 April 2010 14:43

Arnold, I am not talking about signal in the digital domain. As long as you are starting off with a 24 bit system (or better) then being cautious once in the digital domain is not too much of a problem.

I understand that.

Quote:

At the analogue preamp, that is a different story.

Different yes, but the question is whether or not that difference causes audible problems.

Quote:

I have some keyboards that I have to pad by 40dB compared to others.

Is it odd situations like this (which we both know are exceptional and easily managable by other means) that are the sole basis of the iron rule that you have tried to establish here?

Quote:

You really don't want your analogue mic pre's (and they are all analogue mic pre's unless you are running digital mics) to be set with 40dB to 50dB of headroom.  You will end up with noise.

Basiczlly what you're saying is that if you decide to unplug a line-level source and plug in a mic-level source into the same input jack, then adjusting the gain in a later stage could cause audible noise.  I agree, except that I can't imagine why even a marginally-knowlegable technical person would do such a thing.

Fool that I am, I *never* plug line level sources into mic inputs without some kind of in-line level matching.  Usually the level-matching facility is right next to the mic input jack in the form of a line level input jack. And vice-versa.

Wouldn't you say that plugging a line level source into the mic input on a DM2000 or a ADA 8000 would be complete and utter folly, a classic newbie gaff, given that there is a line level input jack right next to the mic jack?

I think that the example given above can be easily dismissed if we presume that the tech staff has minimal competence and knows what to plug where.

[Lee Buckalew]

Quote:

Basiczlly what you're saying is that if you decide to unplug a line-level source and plug in a mic-level source into the same input jack, then adjusting the gain in a later stage could cause audible noise. I agree, except that I can't imagine why even a marginally-knowlegable technical person would do such a thing. Fool that I am, I *never* plug line level sources into mic inputs without some kind of in-line level matching. Usually the level-matching facility is right next to the mic input jack in the form of a line level input jack. And vice-versa. Wouldn't you say that plugging a line level source into the mic input on a DM2000 or a ADA 8000 would be complete and utter folly, a classic newbie gaff, given that there is a line level input jack right next to the mic jack? I think that the example given above can be easily dismissed if we presume that the tech staff has minimal competence and knows what to plug where.

Arnold,
This is exactly the point here.  The original comment had to do with utilizing presets/scenes.  The response was, you could not, in this situation, recall your analogue preamp trims.  It's really quite simple and you agreed with that.  In fact, you can't recall your analogue pre-amp trims unless you have mic pre's that allow for full remote control.  The fact that you state that you would make these adjustments when they are required makes the point that these adjustments are required at times.  Exactly what a few of us were trying to point out.  

I fail to see how being sarcastic and belittling about this by stating "...why even a marginally-knowlegable technical person would do such a thing" could be considered helpful on this page.  I would never assume that a church had tech's that understood anything about mic level vs. line level signals.  Most do not.  Most also do not understand why it's not a good idea to start with a previous eq setting and make adjustments from there for a new singer, speaker, guitar player, etc.  
Your comment regarding gain on a DM2000 is really agreeing with what you are arguing against.  There is one input (XLR) and a trim control for each channel.  In addition there is a pad.  Neither of these can be recalled via scenes or presets but must be manually adjusted when required.
Your comment about knowing what to plug where is really quite funny.  I would estimate that at least 8 out of 10 churches that I consult with or provide training services for have at least one STEREO unbalanced sound source plugged through a dual RCA to 1/4" TRS adapter and connected to their console via a single BALANCED 1/4" TRS input.  They don't know why it sounds funny.  They don't know that one is stereo and one is balanced and they don't know the difference.  Likewise many have a balanced 1/4" TRS output linked to a computer sound cards 1/8" input.  Also wrong, also causing sound problems.  I could go on.
This is not a fault of the volunteers (most have willing hearts and want to do their best) and I mean no offense by it, it is the result of a lack of understanding on the part of church leadership. I don't know any worship leaders who would just pick folks out of the congregation and assign them to play various instruments and expect good results but, that is pretty much what happens for most technical media areas in most churches.  It is looked at as something that most anyone can do that does not really take study or training.  There are some (technically) very good volunteer teams but it is the exception not the norm.
I'll get off my soapbox now.

A large part of the function of this board is to assume that many will not necessarily know these things and to provide some additional insight into questions to ask, potential problems to consider before they occur, etc.  That is all some of us were trying to do here.

Sorry if this comes across too strongly.

His,
Lee Buckalew
Pro Sound Advice, Inc.

[Mac Kerr]

Brad Weber wrote on Fri, 23 April 2010 08:36

The second concern has to do with the comment regarding the school using the system between service related uses.  If they make any changes to the preamp input gains those changes will not be tracked or compensated by the SAC presets or system.  It seems like both you and they will have to chart and verify the preamp analog level settings just as you would for the gain/trim settings on an analog console.  You might even find it useful to 'zero out' the preamps between uses.

This is further complicated by the fact that the OP stated in his first post that the mic pres may be "next to" the sound booth. If they are in a different room it will be difficult to see how they are currently set, and also difficult to adjust them in a hurry. When the laptop interface is used from the floor, the actual mic pres will be even harder to reach.

There are plenty of mic pres that allow remote control, but not at the price point of the ADA8000.

Mac

[Arnold B. Krueger]

Lee Buckalew wrote on Fri, 23 April 2010 19:23

Quote: Basiczlly what you're saying is that if you decide to unplug a line-level source and plug in a mic-level source into the same input jack, then adjusting the gain in a later stage could cause audible noise. I agree, except that I can't imagine why even a marginally-knowlegable technical person would do such a thing. Fool that I am, I *never* plug line level sources into mic inputs without some kind of in-line level matching. Usually the level-matching facility is right next to the mic input jack in the form of a line level input jack. And vice-versa. Wouldn't you say that plugging a line level source into the mic input on a DM2000 or a ADA 8000 would be complete and utter folly, a classic newbie gaff, given that there is a line level input jack right next to the mic jack? I think that the example given above can be easily dismissed if we presume that the tech staff has minimal competence and knows what to plug where. This is exactly the point here.  The original comment had to do with utilizing presets/scenes.  The response was, you could not, in this situation, recall your analogue preamp trims.

Text searching of the entire thread seems to show that the prhases:

"Recall your analog preamp trims" or "recall your analogue preamp trims" or "preamp trims" does not exist in this thread except as you just said it immediately above. Its not in the OP or any following discussion prior to that.

So Lee, it would appear that you are arguing with yourself.

Furthermore, you're not responding to the established fact that there are large numbers of digital consoles that have no means at all for recalling their analog trims or pads. In short, you are criticzing SAC for a feature that is not present in a vast number of existing digital consoles that have been used for years without difficulties of the type that you predict.

I'm not addressing an argument that you are having with yourself Lee, I'm addressing a claim that you made which is quoted below:

"This type of approach to gain will work well for the same player from song to song such as compensating for patch changes from a keyboard, etc. but it is not a good idea for different players, different instruments and different singers  does not appear in this thread.

In fact the type of approach SAC and that a vast number of existing digital consoles that lack recallable trims uses will work well even when there are different players, different instruments, and different singers.

In order to make a counter argument Lee, you've had to resort to: not different singers, not different players, and not different instrucments, but rather a rather significant technical screw-up where a line level signal is connected to a mic input in place of a microphone signal when there was a change in players, instruments, or singers.

Note that we're not addressing a major system configuration change, but rather the normal give-and-take during a performance where a mic is handed from one musican to another, or a normal instrument player change.  

Quote:

It's really quite simple and you agreed with that.  In fact, you can't recall your analogue pre-amp trims unless you have mic pre's that allow for full remote control.

Right, and the absemce of mic preamps with full digital control is very common, SAC or not.  With your requirements one wonders how *anybody* ever made consoles from the 01V through the DM2000 ever work for live sound!

Quote:

The fact that you state that you would make these adjustments when they are required makes the point that these adjustments are required at times.  Exactly what a few of us were trying to point out.

The only time one needs to adjust preamp trims is when there are some pretty dramatic changes to the hardware configuration. These are not what you find when you have different singers,  different players, and different instruments. They are things that happen when you reconfigure the system pretty significantly.

Quote:

I fail to see how being sarcastic and belittling about this by stating "...why even a marginally-knowlegable technical person would do such a thing" could be considered helpful on this page.

I fail to understand why extreme examples that represent bad practice would be required to support a reasonable set of expectations for a digital console.

Quote:

I would never assume that a church had tech's that understood anything about mic level vs. line level signals.

I think that is a pretty exceptional claim. I'm sure there there are churches in that sort of dire situation, but I don't think it is the rule. Sure there churches that have to call for professional tech support every time a cable is plugged or unplugged. However, churches like that aren't or shouldn't be adjusting trims on mic preamps, either.

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Most do not.

That is an unsupported global presumption unless you have some pretty detailed field surveys to back it up.

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Most also do not understand why it's not a good idea to start with a previous eq setting and make adjustments from there for a new singer, speaker, guitar player, etc.

Yet another unsupported global assumption.

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Your comment regarding gain on a DM2000 is really agreeing with what you are arguing against.  There is one input (XLR) and a trim control for each channel.

Then Yamaha's doc is wrong. It says that there is both an XLR and a 1/4" input on the back panel for every mic channel. (page 45 in dm2000v2e1.pdf) IME they handle a normal range of line and mic input signals without audible distortion or noise.

Quote:

In addition there is a pad.  Neither of these can be recalled via scenes or presets but must be manually adjusted when required.

Right, and for a reasonable  set of variations among instruments, singers, and players, and even in more extreme situations, the digital input channel attenuators which can be recalled via scenes and presets, are sufficient.

<snip off-topic discussion of how some churches hook up stereo sources>

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