A&H QU info leaked a day early

[Robert Lofgren]

Re: A&H QU info leaked a day early

There are a couple off the shelf IC chipsets to make ic mic preamps with digital gain control... not heavy lifting or very expensive.

JR

Are you thinking of digital pots or actual opamps with i2c/spi control? Do you have any good ic examples in mind?

 

[Scott Bolt]

Re: A&H QU info leaked a day early

Here's my take on the GEQ/PEQ conundrum:

I prefer to use PEQ on my aux output/monitor sends. Most onboard PEQ is four band, sometimes five. Some of the 4 band setups only have fixed Q/shelving options on the LF and HF. As a result, I still will haul a 3-space rack with Sabine GraphiQ's, giving me 6 aux mix control. Yes, I'm still hauling a (small) rack. But having 12 filters/channel, selectable between dynamic and parametric gives me control far beyond the built-in offerings on the under $10K digital consoles. It also gives me limiting, delay, compression (which I almost never use) and variable Q graphic as well as allowing me to leave a couple of filters in FBX mode to catch the inadvertent monitor scream when the acoustic guitar player bends over to move the set list or adjust their Baggs and reflects monitor into their vocal mic.

Doesn't it kind of defeat the purpose of making an "all-in-one" digital mixer if you start filling your rack back up with all your analog stuff again?

One of the most appealing features of these new digital mixers is eliminating the need for lots of outboard gear (at least it is for me).

For what I would look for in a mixer, it would be important for the channel eq (and internal insert eq) to be powerful and flexible in a digital mixer. I think products which have a less powerful eq will be at a disadvantage in this market.

 

[Warrick Moore]

Re: A&H QU info leaked a day early

 

[Per Søvik]

Re: A&H QU info leaked a day early

Doesn't it kind of defeat the purpose of making an "all-in-one" digital mixer if you start filling your rack back up with all your analog stuff again?
<snip>

That was my thinking as well untill I actually got a digital mixer that replaced all the outboard stuff I had, but I didn't have all the outboard stuff that I wanted. Since the mixer eliminates about two outboard racks, I can have the equivalent of four outboard racks by just carrying two outboard racks (that I already have) ~:-D~:grin:

 

[Scott Bolt]

Re: A&H QU info leaked a day early

That was my thinking as well untill I actually got a digital mixer that replaced all the outboard stuff I had, but I didn't have all the outboard stuff that I wanted. Since the mixer eliminates about two outboard racks, I can have the equivalent of four outboard racks by just carrying two outboard racks (that I already have) ~:-D~:grin:

We all get GAS once in a while

My knees are not getting any younger and right now, my instrument rack is the heaviest piece of gear I own. Less is really starting to look like "more" ..... at least to my knees

 

[John Roberts]

Re: A&H QU info leaked a day early

Are you thinking of digital pots or actual opamps with i2c/spi control? Do you have any good ic examples in mind?

TI, and THAT Corp have chips/chip sets that accept serial control, I don't have the part numbers memorized but they are easy enough to find. By now there may be others.

JR

PS: I have also looked at DPOTs Which is similar technology to what they use inside the dedicated preamp chip sets. They have worked out some of the details to use them effectively that you would learn the hard way rolling your own.

 

[Scott Bolt]

Re: A&H QU info leaked a day early

TI, and THAT Corp have chips/chip sets that accept serial control, I don't have the part numbers memorized but they are easy enough to find. By now there may be others.

JR

PS: I have also looked at DPOTs Which is similar technology to what they use inside the dedicated preamp chip sets. They have worked out some of the details to use them effectively that you would learn the hard way rolling your own.

I was not aware until you mentioned in another post that there are actually off-the-shelf IC's for preamps already. I was aware that the preamp circuit is not that profound even when you use discrete circuitry like in my MixWiz.

There is really nothing fancy in there, and the MixWiz preamps sound pretty darned good for the $2.00 worth of parts per channel of discrete through hole parts it has in it

I think that there are likely many more parts of the mixer that have vastly greater effect on the overall sound of the mixer than the preamps, but for some reason, marketing has latched on to the preamp circuit as the "special sauce". Weird.

On the digital consoles, I think that the A/D and D/A IC's that are off-the-shelf are also pretty good, and pretty standard. That pretty much leaves the DSP algorithms and central processing firmware as a differentiator with respect to sound quality.

 

[John Roberts]

Re: A&H QU info leaked a day early

I was not aware until you mentioned in another post that there are actually off-the-shelf IC's for preamps already. I was aware that the preamp circuit is not that profound even when you use discrete circuitry like in my MixWiz.

There is really nothing fancy in there, and the MixWiz preamps sound pretty darned good for the $2.00 worth of parts per channel of discrete through hole parts it has in it

I think that there are likely many more parts of the mixer that have vastly greater effect on the overall sound of the mixer than the preamps, but for some reason, marketing has latched on to the preamp circuit as the "special sauce". Weird.

On the digital consoles, I think that the A/D and D/A IC's that are off-the-shelf are also pretty good, and pretty standard. That pretty much leaves the DSP algorithms and central processing firmware as a differentiator with respect to sound quality.

Kind of like WMD and Iraq, advertisers brag about mic preamps because customers want to believe that they are different so such advertising gains traction with the audience and wins sales. I guess I object a little to characterizing mic preamps as easy, because I was doing it when it wasn't, but now it is mostly cookbook designs purchased off the shelf. As they approach perfection, the only way to make them different is to make them less linear.

I actually wrote an article on the subject of console design back in 1980. On my judgement then and still the important considerations were Mic preamps, EQ and sum buses. Mic preamps and all are easier/better thanks to improved IC performance. Control laws, EQ voicing, human factors engineering will always matter in the margin.

JR

 

[Scott Bolt]

Re: A&H QU info leaked a day early

Kind of like WMD and Iraq, advertisers brag about mic preamps because customers want to believe that they are different so such advertising gains traction with the audience and wins sales. I guess I object a little to characterizing mic preamps as easy, because I was doing it when it wasn't, but now it is mostly cookbook designs purchased off the shelf. As they approach perfection, the only way to make them different is to make them less linear.

I actually wrote an article on the subject of console design back in 1980. On my judgement then and still the important considerations were Mic preamps, EQ and sum buses. Mic preamps and all are easier/better thanks to improved IC performance. Control laws, EQ voicing, human factors engineering will always matter in the margin.

JR

Hey John,

Do you know if the preamp IC's have built in load dump and ESD protection?

I agree. This is similar to op amps. If you had to design the analog external circuit, it would require some serious know how. Just setting up bias resistors and feedback/filtering isn't hard at all (especially with an app note to aid you).

I would expect pretty much all new digital mixers to have decent preamps. The rest of the guts seems to be pretty software and VHDL centric. The real IP is going to be the firmware IMHO.

 

[John Roberts]

Re: A&H QU info leaked a day early

Hey John,

Do you know if the preamp IC's have built in load dump and ESD protection?

Not sure what you mean by load dump (input caps?), but yes, all modern ICs have serious input/output pin protection for ESD, while careful handling is still best practices. THAT engineers have written one or more AES papers about the "extra" input protection circuitry requirements for large phantom voltage DC blocking input caps charged to 50V and shorted to ground. The amps of transient current are beyond what internal IC clamps can handle.

I agree. This is similar to op amps. If you had to design the analog external circuit, it would require some serious know how. Just setting up bias resistors and feedback/filtering isn't hard at all (especially with an app note to aid you).

I would expect pretty much all new digital mixers to have decent preamps. The rest of the guts seems to be pretty software and VHDL centric. The real IP is going to be the firmware IMHO.

I've watched this closely for as long as there was a digital console industry. The technology available today is far better and cheaper than it was. They are still consoles so design execution and details matter.

JR

PS: I had a conversation with one of the THAT chip design engineers about a different IC of theirs that I was asking about a semi-custom slightly different version. The simpler IC had more silicon dedicated to pin protection than to the actual working circuitry. Customers don't understand chips failing just because they were handled.

 

[Scott Bolt]

Re: A&H QU info leaked a day early

Not sure what you mean by load dump (input caps?), but yes, all modern ICs have serious input/output pin protection for ESD, while careful handling is still best practices. THAT engineers have written one or more AES papers about the "extra" input protection circuitry requirements for large phantom voltage DC blocking input caps charged to 50V and shorted to ground. The amps of transient current are beyond what internal IC clamps can handle.

I've watched this closely for as long as there was a digital console industry. The technology available today is far better and cheaper than it was. They are still consoles so design execution and details matter.

JR

PS: I had a conversation with one of the THAT chip design engineers about a different IC of theirs that I was asking about a semi-custom slightly different version. The simpler IC had more silicon dedicated to pin protection than to the actual working circuitry. Customers don't understand chips failing just because they were handled.

Thanks for the reply John,

Load dump is a longer transient designed to drain off a voltage offset presented by an isolated device being connected to the circuit. I work in automotive, so this is really an issue. A car traveling through dry air on rubber tires can create quite a capacitive charge. All the electronics within the vehicle reference the chassis ground, so it doesn't matter that the chassis ground is actually +100V from earth ground ..... until you connect a piece of diagnostic gear (which I design) that is plugged into a wall earth ground. These transients tend to be lower voltage, but much higher energy. They also tend to wreak havoc with your ground for a few milliseconds.

ESD is typically using the human body model of capacitance .... so really just the energy that you can store on your body while wearing rubber shoes These transients are faster and very high voltage.

Sometimes the handling of chips can cause issues because the chips are not hooked up in circuit and presents quite a few unusual discharge cases that aren't really possible (or likely) when in circuit.

Our lab has a discharge plate when you enter, wrist grounding straps, and connections to every table for work on circuits .... all to keep this from happening as we build very expensive prototypes. It is a great time saver since trying to figure out that you broke a chip while handling a board really stinks

On the Qu16, it looks to me like it is a much better option for many people than the Expression si because of the integrated ability to record and playback directly from USB built in. The Expression Si requires a MADI card that is not included and appears to run around 1K.