Feedforward / look-ahead compressor

Where we discuss new analog design ideas for Pro Audio and modern spins on vintage ones.
User avatar
JR.
Posts: 3709
Joined: Sat May 24, 2008 7:21 pm
Contact:

Re: Feedforward / look-ahead compressor

Post by JR. »

raf wrote:
I wish you continued success with you compressor, but i attribute that success to the specific combination of components and design decisions you made.
I only wish it were that easy. Anyway, I wasn't talking about my products here...
There is nothing remotely easy about that...
I also didn't want to prolong a useless HW vs SW debate... This was my opinion, I could not care less how many disagree or agree. I do wish I could post without the perception that I was hocking my products though.
(Hawking?) Sorry I brought that up... I do wish you continued success.

Have you ever considered a plug-in for yours? Might be good to do one, before someone else does.

Or not....

JR
Cancel the "cancel culture", do not support mob hatred.
emrr
Posts: 573
Joined: Sun Mar 02, 2008 10:27 pm
Location: NC, USA
Contact:

Re: Feedforward / look-ahead compressor

Post by emrr »

I'm tending to agree with the point the the software designers generally are not hardware designers, and tend to have less experience with what hardware actually does, and why. So they model the surface aspects, a few of the most obvious traits they get from some testing, and can't see in any further than that. All one has to do is look at the built in dynamics models in the AU system, or many DAW's. Many examples of control descriptives that have never existed in pro audio! Names created by someone from a coding perspective, who has no knowledge of industry language and standards.
Best,

Doug Williams
Electromagnetic Radiation Recorders
User avatar
JR.
Posts: 3709
Joined: Sat May 24, 2008 7:21 pm
Contact:

Re: Feedforward / look-ahead compressor

Post by JR. »

emrr wrote:I'm tending to agree with the point the the software designers generally are not hardware designers, and tend to have less experience with what hardware actually does, and why. So they model the surface aspects, a few of the most obvious traits they get from some testing, and can't see in any further than that. All one has to do is look at the built in dynamics models in the AU system, or many DAW's. Many examples of control descriptives that have never existed in pro audio! Names created by someone from a coding perspective, who has no knowledge of industry language and standards.
I dislike stereotypes but I encountered a certain amount of that during 15 years working at Peavey where I was strictly an analog guy and often had to rely upon digital specialists from the digital group. I recall one case where a digital implementation of a dynamics function (gate-downward expander), that remarkably sounded better (smoother) than any analog gate I ever designed. I asked but never got a good understanding for how and why, and this was just one one minor function inside a cheap multi-efx unit, long obsolete now. Knowing the coder involved, I consider the fact that it sounded so good, pretty much an accident and not reflective of the software coder's chops.

I am aware of at a least a small handful of old school analog pukes who evolved into DSP. One notable engineer is Steve Dove who I have faith will get it right. Of course for every Steve Dove writing DSP code there will be 100 wet behind the ears coders without a clue. Not only are they clue-less but inconsistent. I have been ranting for almost a decade now that we don't even have a clear definition for Q in a boost/cut EQ, but that was true for analog circuits too. It's only more visible with digital control of EQs, where there is an expectation of accuracy or consistency to accompany the control precision.

In the area of loudspeaker processing there is a small handful at the cutting edge who not only work in the digital domain but have developed semi-custom platforms to support their advanced work. This is a case of a sharp engineer defining a task, and then creating the tool to accomplish that task. Digital is a very powerful tool.

Getting back on topic (sort of) dynamics processing strikes me as a rich opportunity for non-linear (digital) decision making. Much of the strategy behind dynamics processing is to conceal artifacts from short term gain changes, while realizing the benefit of the longer term gain manipulation. There are many individual techniques to accomplish this but they often involve trade-offs in complexity. In the digital domain multiple strategies can be overlaid using the same base hardware, and selectively applied using situational decision making.

Analog hardware and software (on digital hardware) are both means to accomplish an end. Many of the early classic or legacy design are mostly accidents or victims of how the gain change was effected. Some like the combination of luminescent panel with photo-resistor sound very good despite the simplicity of the approach, others not so sweet.

Digital hardware finally separates the performance of the gain element from the overall path integrity, but just like before we can not completely get away from the artifacts caused by raw gain manipulations. So the task to make it sound good has just begun.

I speak about what could be, not what is (?)... IMO digital dynamics "could" be superior... time will tell where we end up. 8-)

JR
Cancel the "cancel culture", do not support mob hatred.
emrr
Posts: 573
Joined: Sun Mar 02, 2008 10:27 pm
Location: NC, USA
Contact:

Re: Feedforward / look-ahead compressor

Post by emrr »

I agree, a nut worth cracking. Usually not yet cracked. Good point about speaker design and implementation in the digital realm, that seems to be light years ahead of dynamics control.
Best,

Doug Williams
Electromagnetic Radiation Recorders
User avatar
mediatechnology
Posts: 5466
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Feedforward / look-ahead compressor

Post by mediatechnology »

Some like the combination of luminescent panel with photo-resistor sound very good despite the simplicity of the approach
And how many coders - or cloners for that matter - understand the complex interaction of the blue/green (and more blue with increasing frequency) output of the luminescent panel coupled with the sharp sunlight yellow peak of the photo resistor? (For that matter why don't LA-4's use yellow LEDs?)

And if they model some vintage classic effects device how do we know they got a good one?
Was the 1176 model based on one they "borrowed" from a local studio one that also needed its caps replaced?
Was the Pultec used for modeling recently re-tubed?
Did the LA-3 have an EL panel that was getting a little dim?

If you've been asked by your boss to model 50 different pieces of vintage outboard gear, what do you suppose your budget is to go out and purchase fully-refurbished units?
Or rent them?
Your budget is probably close to $0.
So you beg and borrow gear to model them and call each sample representative of the entire serial number range.
emrr
Posts: 573
Joined: Sun Mar 02, 2008 10:27 pm
Location: NC, USA
Contact:

Re: Feedforward / look-ahead compressor

Post by emrr »

I get requests form software companies who want me to pass some impulses through my various vintage compressors, in exchange for copies of the software they develop.

'delete'.....
Best,

Doug Williams
Electromagnetic Radiation Recorders
User avatar
JR.
Posts: 3709
Joined: Sat May 24, 2008 7:21 pm
Contact:

Re: Feedforward / look-ahead compressor

Post by JR. »

I only warrant that classic limiters could be modeled, not that I have the secret sauce.

My original plan was to present my models as presets or beginning points while giving the end user complete control to tweak the models from there.

While I don't dispute that there are numerous subtleties involved, IMO a lot (not all) of the sound from legacy dynamics can be covered by simple models. A swiss army comp, that can cover most could get popular.

My limitation has long been the interface to manage all the variables as the technology to do this pretty well already exists. I expect a computer terminal based interface as the only way to handle that many choices.

To be merchantable it need to be both easy to get a good sound relatively quickly, while flexible enough to be more than a hollow mimic. After you dial in a legacy sound that you like, it should be simple to save and recall that for later use.

or not..... don't toss your classic gear into the trash bin just yet. 8-)

=======

FWIW I recall a project back while I was working at Peavey's AMR recording division. My boss at the time wanted to model a bunch of classic microphones so budget recording consumers could just dial up an expensive mic sound. The technology at the time (mid '80s) could just about cover rudimentary frequency response tweaks, but there is more going on and the project was dropped.

JR
Cancel the "cancel culture", do not support mob hatred.
User avatar
mediatechnology
Posts: 5466
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Feedforward / look-ahead compressor

Post by mediatechnology »

I get requests form software companies who want me to pass some impulses through my various vintage compressors, in exchange for copies of the software they develop.

'delete'.....
So their budgets are $0. :lol:
User avatar
mediatechnology
Posts: 5466
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: Feedforward / look-ahead compressor

Post by mediatechnology »

hazmo - The EMT266 Transient Limiter schematics were very interesting particularly the all-pass stages.

Why not do the all-pass as it's shown using modern op amps?

This also caught my eye:

Image
EMT 266 Transient Limiter Rectifier Block

The EMT Transient Limiter appears to be looking for the highest of four peaks" L+, L-, R+ and R-.

Reminded me of this prototype I did:

Image
Greater of Four Audio Level Detector Using a THAT1646 Picks Highest Peak Level

Image
Greater of Four Audio Level Detector, Halfwave Waveform.
User avatar
JR.
Posts: 3709
Joined: Sat May 24, 2008 7:21 pm
Contact:

Re: Feedforward / look-ahead compressor

Post by JR. »

Now this is an interesting coincidence.

http://soundforums.net/junior-varsity/4 ... #post32161

Uli just announced that they are planning to make free digital plugins for their new cheap digital console
Our roadmap includes Neve, SSL, Urei and other well-known products such as the LA-2A compressor, Lexicon reverbs, SPL De-Esser and the TC Finalizer multiband compressor etc.
ewwww :roll:

JR
Cancel the "cancel culture", do not support mob hatred.
Post Reply