Patented Infinite Shape Feature (ISF) in Blackstar amps

[Steve A.]

This fully interactive control allows you to infinitely adjust the response of the tone control network between any of the traditional voicings. In this way you can design your own sound and truly find the sound in your head.

Getting The Sound In Your Head

ISF works in conjunction with the Bass, Middle and Treble controls to give you access to infinite new sound possibilities.

HT-5RH ISF Details - Blackstar Amplification

So does anybody here know if this control adjusts the value of the slope resistor? A lot of the amp builders here have been using that trick for many years. (One way to do that is to add a 33k resistor in series with a 100k pot wired up as a variable resistor which gives you a range of ~33k to 133k.)

Thanks!

Steve Ahola

[exclamationmark]

I actually have a Blackstar... and by "infinite new tone possibilities" they mean about two. That aside, I don't actually know how it works. I'd assume it's some sort of slope control or mid-shift control. I'm somewhat partial to the James tone stack with a mid-shift control. Shifting the centre point around (or making it wider, steeper and so on) seems to give the illusion of 'infinite tone shaping' abilities.

Although I'd be slightly disappointed if the patent office actually granted them the ability to monopolize the use of a potentiometer in place of a resistor... Never stopped Randall Smith though, haha.

[tboy]

Marshall used a variable slope resistor in at least one amp - the JCM800 Model 2000. The knob was labelled "sweep" and the range was 10k - 110k.

[Bruce / Mission Amps]

Hmmm... where did it say it was patented? I briefly looked over the site and didn't spot it...
If not patented (who'd pay to bust it if it was anyhow)... I was under the impression that it was illegal to claim a patent if there is none.

It does say "patented applied for"... which means nothing good or bad.
It means they released it thinking they can own it, unless someone at the patent office is alerted or spots the preexisting artwork... etc. I don't think it is the patent office's duty to discovery much though, is it?
U.S. Patents are a joke anyhow unless you have BIG bucks to fight or defend.

[imaradiostar]

I spent some time simulating various iterations of their design, trying to figure it out. I don't think I ever came up with the real deal. In the end I concluded I'd rather just stick with one design. You mileage may vary, of course.

jamie

[teemuk]

Yes, patent has been applied for it and in fact any patent search engine that can search British patents will find the application document, which the reveals technical details of the circuit. The amps use the circuit depicted in the patent document but the pedals use a different kind of a circuit, which is an active one. No, it's not a variable "slope resistor".

[Steve A.]

Hmmm... where did it say it was patented?

It uses the word "patented" on the product description pages for the amps that use the feature.

Yes, patent has been applied for it and in fact any patent search engine that can search British patents will find the application document, which the reveals technical details of the circuit.

Can you post the number of the patent application? Or is that one of those things that if you told me you'd have to kill me?

Thanks!

Steve Ahola

[teemuk]

http://www.sewatt.com/files/sewatt/GB2446188A.pdf

[Steve A.]

http://www.sewatt.com/files/sewatt/GB2446188A.pdf

Thanks- that is a very interesting circuit!

Steve

P.S. I am surprised that you can view and download files from sewatt.com without becoming a member and logging on (since you need to do that to even view the forums). Sometimes I think it must be easier to hack into the Pentagon than to enter the sewatt.com (along with the sibling sites including ppwatt.com).

[J M Fahey]

Well, in fact they vary *two* slope resistors at the same time, the low shelving and the high shelving one.
Nice, and probably works well, but not *that* patentable.
As has been said above, *anybody* knows that varying parts values (including resistors) changes Tone Control characteristics, and the method of doing so, either with pots or switched resistors "should be self evident to anybody normally versed in the art" , which is a condition stated by the Patent Office. (not the exact words but something very close which means that).
Would be similar to somebody asking a patent on fitting trimmer resistors to tube cathodes, to fine tune bias, and claiming "I deserve a Patent because I don´t know anybody doing so and can´t find a prior Patent on this subject" ... which may very well be true, of course.
I´m not criticizing the idea itself, which I find interesting and probably useful, but the patentability issue.

*Real* Electronics Guru Don Lancaster has some strong ideas about Patents and their problems.
If you have some spare time, browse the links shown in:
"Guru's Lair: Patent Avoidance Library"

If you have a lot of spare time, browse the rest of his site, very interesting.

[Steve A.]

Well, in fact they vary *two* slope resistors at the same time, the low shelving and the high shelving one.
Nice, and probably works well, but not *that* patentable.

When I look at some of the other patents granted for guitar amps (like a fixed bias/cathode bias switch- or most of R. Smith's patents) I don't find the Blackstar one to be that objectionable. As I recall most of R. Smith's patents included sample values (probably different from what was used in the actual amps but they would get you in the ballpark)- is that no longer required, or just for the patents in the UK?

Steve

[J M Fahey]

Hi steve a
Please let me be more precise, I´m afraid I was not.
If we define "patentable" as something that those hardworking Public workers there can grant, well, there´s a lot of "Patentable" stuff.
Their basic "patentability" test for them is whether it was previously patented or not; not much more than that.
As Don Lancaster explains, the problem is not so much getting a piece of paper stating that such and such thing is patented in your name, but being able to defend it in Court.
And it can be challenged, not by proving it was already patented (which in theory you are protected against) but simply by showing that *somebody* published it earlier, in a Trade Journal, a Magazine article "somewhere" , *maybe* in some Forum such as ours.
Please trake a look at:
http://www.tinaja.com/glib/bustpat.pdf

[R.G.]

It's funny. There are things I'd be embarrassed to say I held a patent on. I guess I'm just too hard on myself that way.

I did find that there was a patent issued on the idea of using a variable voltage, variable resistance output on a voltage regulator to fake a dying battery for pedals. It's not mine.

It was applied for six months after I published the scheme at geofex.

Silly me. I was taught that to be patentable, any invention had to be NOT obvious to one skilled in the art.

[J M Fahey]

Well, that patent, if granted, dies a violent death the very second anybody, not even you, refers to your Geofex article.

[diagrammatiks]

the isf is stupid.