variable harmonic drive discussion

Help Support GroupDIY:

pucho812

Well-known member
Joined
Oct 4, 2004
Messages
13,103
Location
third stone from the sun
As you guys know I along with the other member of the tech team installed a SSL duality this past week. unfortunately there are no schematics that came with the console.  Not surprised there as ssl has a different idea when it comes to servicing a board these days. Not a bad thing at all. But I am curious about there variable harmonic drive circuit and how they are mimicking harmonic valve distortion.

what it is: it's part of the mic pre  that emulates the characteristics of a classic valve front end but with option to taylor the harmonic mix(put that goes btween 2nd and 3rd order harmonics) when the preamp is overdriven via the Drive Control.

I would think they are just clipping an op ap or 2 but that would sound gross where as this sounds interesting. any ideas?


found a patent for solid state emulation of valves/vacuum tubes. maybe we can think some ideas here?
 

Attachments

  • 5636284_Solid_state_emulation_of_vacuum.pdf
    284 KB · Views: 267

tv

Well-known member
Joined
Feb 22, 2006
Messages
1,459
Hey, trace the circuit - or post the gutshots for other forumites ...
 

JohnRoberts

Well-known member
Staff member
GDIY Supporter
Moderator
Joined
Nov 30, 2006
Messages
23,283
Location
Hickory, MS
If you look at that patent in the references cited section, you will notice 13 other earlier patents listed.  At least two of those earlier patents are from Jack Sondermeyer a very experienced engineer I knew at Peavey. 

From a glance at the patent you cited it looks like they are playing with artificially raising the output impedance and some diode clipping tricks. I don't care enough to look at the specific claims, but you might look at all the patents referenced for a broader view of the state of the art. Not to mention new work done since then, if any.

I am uncomfortable with adding what is essentially an effect to a premium audio path, but that may be what it takes to sell an analog path these days. It shouldn't sound worse than dumb asses clipping their mic pre's like they do now.

JR

PS: Perhaps ironically Sondermeyer was the senior engineer on peavey's (AMR) well regarded VMP tube mic preamp, and that was very clean. While it did clip like a tube since it was one.  8)

 

topcat

Well-known member
Joined
Jun 4, 2010
Messages
227
Location
Oxford
I think the David Mates "Red Lion" (RED LION 49 LIMITED TRADING AS SOLID STATE LOGIC) patents might add to the fun here....in particular

Cheers

Tim



 

Attachments

  • 11_508_399_Amplifying_an_audio_signal[1].pdf
    93.6 KB · Views: 127

JohnRoberts

Well-known member
Staff member
GDIY Supporter
Moderator
Joined
Nov 30, 2006
Messages
23,283
Location
Hickory, MS
That Mates patent claim #1 is a little broad,  "using a nonlinear component in a feedback path..".

That patent would make pretty much every non-linear feedback path an infringement...  The only reason guitar fuzz tone doesn't infringe is because it isn't used in combination with a microphone input.

JR
 

pucho812

Well-known member
Joined
Oct 4, 2004
Messages
13,103
Location
third stone from the sun
JohnRoberts said:
If you look at that patent in the references cited section, you will notice 13 other earlier patents listed.  At least two of those earlier patents are from Jack Sondermeyer a very experienced engineer I knew at Peavey. 

From a glance at the patent you cited it looks like they are playing with artificially raising the output impedance and some diode clipping tricks. I don't care enough to look at the specific claims, but you might look at all the patents referenced for a broader view of the state of the art. Not to mention new work done since then, if any.

I am uncomfortable with adding what is essentially an effect to a premium audio path, but that may be what it takes to sell an analog path these days. It shouldn't sound worse than dumb asses clipping their mic pre's like they do now.

JR

PS: Perhaps ironically Sondermeyer was the senior engineer on peavey's (AMR) well regarded VMP tube mic preamp, and that was very clean. While it did clip like a tube since it was one.  8)


John I agree in the fact that you are adding effect to the signal in the audio path.  and yes that sells audio now days. Funny how we spend so much time recreating things from before. Like in DAW systems how they waste so much time trying to recreate the sound tape or other such nonsense.
 

JohnRoberts

Well-known member
Staff member
GDIY Supporter
Moderator
Joined
Nov 30, 2006
Messages
23,283
Location
Hickory, MS
The customer is always right, even when he's silly...

There is a vague logic to it, but that's the nicest thing I can say.

JR
 

topcat

Well-known member
Joined
Jun 4, 2010
Messages
227
Location
Oxford
JohnRoberts said:
The customer is always right, even when he's silly...

There is a vague logic to it, but that's the nicest thing I can say.

JR

Too True JR

It's OK when people listen to equipment but when it's driven by fashion or marketing it's not so easy to be nice.

When an addenoidal radio show talent demands a specific mic and preamp with "curvebending magic" to sound """"great""" I'm tempted to note that McDonalds are hiring

TC
 

Joechris

Well-known member
Joined
Jun 3, 2004
Messages
320
Location
Norway
There was a old thread on the topic here:
http://www.groupdiy.com/index.php?topic=18681.0
In my opinion harmonics and distortion today is just as serious tools as eq and compression,
so to call this fashion or marketing seems a bit unfair to me.
 

topcat

Well-known member
Joined
Jun 4, 2010
Messages
227
Location
Oxford
Joechris said:
There was a old thread on the topic here:
http://www.groupdiy.com/index.php?topic=18681.0
In my opinion harmonics and distortion today is just as serious tools as eq and compression,
so to call this fashion or marketing seems a bit unfair to me.

Thanks for pointing out the old topic joechris.
Distortion and harmonics are indeed serious creative tools in the right hands...
I work in the broadcasting industry and have lost count of the number of demands for 'must have' processing products from talent, producers and creatives, without which the company will loose audience/revenue/key talent and in all bar one case the product quickly became obsolete when the next big thing came along.
Perhaps fashion is too strong a word but I remember the wholesale abandonment of 70's transistor mic preamps, opto-compressors, Neve consoles and dynamics ( i could have been a wealthy man if I'd kept all the Neve kit that was ripped out in the 80's :-( )etc....etc...
Oh yes the one case was a French multiband compressor limiter that add's an edgy grainyness and audible testosterone.

 

barclaycon

Well-known member
Joined
Jan 17, 2007
Messages
696
Location
London, England
First of all, I'd really like to know if the SSL harmonic distortion thing really works. Have you had chance to listen to it?
I recall a few decades ago that they tried to emulate the sound of a Pultec in one of their EQ designs. Not very successfully in my opinion.

Harmonic distortion is a sound tool like any other effect.
A lot of what mixers try to do with compression is add harmonic distortion in order to enhance the sound (not just level control!) And 'aural exciters' - again, adding distortion.
One of the best harmonic distortion boxes I have encountered was made by Summit and just had a control in the middle of a panel marked 'warmth'. It was a valve design. Summit seem to be one of the few companies that successfully worked out what was good about valve distortion, and also how to apply it. Great EQ's and compressors. (I think it was the same guy who started Crane Song).

Anyway. A box that creates variable harmonic distortion - odd, even etc. and maybe even variable slew rate, would be a great DIY project!
 

pucho812

Well-known member
Joined
Oct 4, 2004
Messages
13,103
Location
third stone from the sun
barclaycon said:
First of all, I'd really like to know if the SSL harmonic distortion thing really works. Have you had chance to listen to it?
I recall a few decades ago that they tried to emulate the sound of a Pultec in one of their EQ designs. Not very successfully in my opinion.

Harmonic distortion is a sound tool like any other effect.
A lot of what mixers try to do with compression is add harmonic distortion in order to enhance the sound (not just level control!) And 'aural exciters' - again, adding distortion.
One of the best harmonic distortion boxes I have encountered was made by Summit and just had a control in the middle of a panel marked 'warmth'. It was a valve design. Summit seem to be one of the few companies that successfully worked out what was good about valve distortion, and also how to apply it. Great EQ's and compressors. (I think it was the same guy who started Crane Song).

Anyway. A box that creates variable harmonic distortion - odd, even etc. and maybe even variable slew rate, would be a great DIY project!


it works. it does alter the sound and  I would imagine it is very useful depending on the project.
 

JohnRoberts

Well-known member
Staff member
GDIY Supporter
Moderator
Joined
Nov 30, 2006
Messages
23,283
Location
Hickory, MS
Joechris said:
There was a old thread on the topic here:
http://www.groupdiy.com/index.php?topic=18681.0
In my opinion harmonics and distortion today is just as serious tools as eq and compression,
so to call this fashion or marketing seems a bit unfair to me.

I am not disputing the use of distortion as a useful studio effect, only questioning the merit of putting it in a reference audio path.

This is not an always-in effect like some products that add coloration in the primary path, since I presume below clipping the path is linear and clean.

I will not argue that hard solid state clipping is ever good, so this should easily beat that.

I am just a little surprised to see this inside a console... As if i needed more evidence that I'm getting old. 

JR
 

mr coffee

Well-known member
Joined
Aug 1, 2005
Messages
145
Location
North Carolina, USA
Pucho, John, and all,

I expect the additional circuitry is minimal if it’s added to every channel.

I’ve never seen or heard an SSL console, but I assume there is a compressor for each channel; if not, this probably ain’t even close and I'm making an a** of myself here, but here goes...

As a guy who enjoys designing electronics for electric guitar and is always exploring new ways to make pleasant-sounding distortion, I’ve been around the block a few times in the generate-harmonics-on-purpose area), so I have a "maybe" guess.

My guess is that SSL is just taking the output of a precision half-wave rectifier, going to one end of the pot (labeled 2nd order) and another output from the full-wave rectifier, going to the other end of the pot (labeled 3rd order) and then passing the signal from the wiper through a pair of back-to-back diodes (to make it not distort the signal in a band around zero-crossing on both positive and negative excursions of the waveform), run that through a resistive attenuator referenced to the control signal for the channel VCA, and voila, you have a harmonic generator because the amplitude modulation applied to the VCA control port turns it into a de facto 2-quadrant multiplier which decreases the gain ever so slightly above a certain threshold on just one half of the waveform (for 2nd order harmonic generation) or on both waveform halves (for 3rd order harmonic generation). The exponential response of the Control port can be partly "logged out" by the level of current the diodes run at, but it probably doesn't matter when you are trying to generate distortion.

If you think about it, you have to have a precision rectifier to drive the VCA for the compressor circuit anyway, so that circuitry is already present in each channel. You are only adding a handful of components to add this effect or “feature.”

I’ve used a variation (less slight gain variation in the VCA) to get a valve-ish overdrive sound for years in custom FX boxes. Warms up a bass or guitar like pushing speakers a bit harder at low settings and gets more like soft clipping distortion at higher settings. Think more like a Bassmun than a Marshill.

A high quality VCA is probably too pricey for most stompbucks manufacturers, but for custom electronics designs where a higher price is acceptable to get “MY TONE”,  it’s workable. And in a console where you've got most all the parts just sitting there and musicians bitching because "Digital sounds too sterile man. Music sounded better when we recorded on an old Studer..." ::), it makes perfect sense.

mr coffee
 

Michael Tibes

Well-known member
Joined
Jun 5, 2004
Messages
797
Location
Berlin, Germany
I have no idea whether that's got anything to do with the SSL circuit, but I'd totally like to hear how it would sound what you sketched. Should be a great diy project!

Michael
 

Latest posts

Top