JFET Auto-Biasing

[puretube]

So has anyone else figured out how to auto-bias JFETs for use in Fetzer Valve type circuits? By auto-biasing I mean leveling the playing field for all JFETs by using simple fixed value parts, thus eliminating the need for transistor sorting, trimmers, or additional active devices. I'm thinking that from a manufacturing standpoint this would save an enormous amount of time and money.

Yes.
After some disappointments,
something ("SPB") did work out well...
(like mentioned here and here...).

[tca]

I don't get the point of this thread at all.

+1

[merlinb]

I don't get the point of this thread at all.

+1

+2

The OP seems to be waiting for us to tell him if his circuit already exists, except he won't tell us what it is. I'm not sure why. Maybe he wants to patent it. But what use is that?  Are SAMSUNG waiting in the wings to pounce on the idea and produce a million boutique pedals?

Actually it doesn't sound so much like a new circuit as simply a fortuitous combination of resistor values that happens to cover the spread in different FETs... Or maybe two FETs, one acting as a dummy stage, with cross-coupled self bias?

[Thecomedian]

by patent law: if the "solution" is "obvious", it cannot be patented, or it can be fought. If a bunch of other people were to say "X will do this", he could destroy their patent holding.

It sounded almost like someone fishing for the idea instead of knowing how to do it themselves, but I can afford to give them the benefit of the doubt and just discuss it, less produce it.

[deadastronaut]

mu amp..

ive patented it..

[aethertransit]

So has anyone else figured out how to auto-bias JFETs for use in Fetzer Valve type circuits? By auto-biasing I mean leveling the playing field for all JFETs by using simple fixed value parts, thus eliminating the need for transistor sorting, trimmers, or additional active devices. I'm thinking that from a manufacturing standpoint this would save an enormous amount of time and money.

Yes.
After some disappointments,
something ("SPB") did work out well...
(like mentioned here and here...).

Nice! So three parts including the input and output caps, that's impressive. 

[aethertransit]

I don't get the point of this thread at all.

+1

+2

The OP seems to be waiting for us to tell him if his circuit already exists, except he won't tell us what it is. I'm not sure why. Maybe he wants to patent it. But what use is that?  Are SAMSUNG waiting in the wings to pounce on the idea and produce a million boutique pedals?

Actually it doesn't sound so much like a new circuit as simply a fortuitous combination of resistor values that happens to cover the spread in different FETs... Or maybe two FETs, one acting as a dummy stage, with cross-coupled self bias?

Wow Merlin, I never expected you to be so judgmental, especially after all the crap I've seen you deal with on the forums. I'm not interested in patenting decades old audio technology, just sharing it with people who will actually appreciate it. And as long as the Randall Smiths of the world are lurking around out there, it would be foolish not to be somewhat careful. Just ask Mikey Soldano.

[puretube]

So has anyone else figured out how to auto-bias JFETs for use in Fetzer Valve type circuits? By auto-biasing I mean leveling the playing field for all JFETs by using simple fixed value parts, thus eliminating the need for transistor sorting, trimmers, or additional active devices. I'm thinking that from a manufacturing standpoint this would save an enormous amount of time and money.

Yes.
After some disappointments,
something ("SPB") did work out well...
(like mentioned here and here...).

Nice! So three parts including the input and output caps, that's impressive. 

compare, and get the idea...  

[aethertransit]

by patent law: if the "solution" is "obvious", it cannot be patented, or it can be fought. If a bunch of other people were to say "X will do this", he could destroy their patent holding.

It sounded almost like someone fishing for the idea instead of knowing how to do it themselves, but I can afford to give them the benefit of the doubt and just discuss it, less produce it.

Who's fishing exactly?

[aethertransit]

So has anyone else figured out how to auto-bias JFETs for use in Fetzer Valve type circuits? By auto-biasing I mean leveling the playing field for all JFETs by using simple fixed value parts, thus eliminating the need for transistor sorting, trimmers, or additional active devices. I'm thinking that from a manufacturing standpoint this would save an enormous amount of time and money.

Yes.
After some disappointments,
something ("SPB") did work out well...
(like mentioned here and here...).

Nice! So three parts including the input and output caps, that's impressive. 

compare, and get the idea...  

I get it now, very nice! Were you able to keep the drain and source resistor values low as well? For instance if I want to construct a Fender stage I can use the 1.5K/22uF source combo and then determine the fixed value for the drain. I try to limit the gain of each stage to keep things smooth and prevent blocking distortion. On a side note, I see that Martin Soulsonic was part of that conversation. What ever happened to him?

[nocentelli]

my original question was if anyone ELSE had figured this out yet...

I HAVE, I HAVE!!!

[midwayfair]

mu amp..

One of the few real answers on this thread.  ...

Seriously, OP, posting "I've discovered something that's of great interest to a lot of audio electronics people but I'm not going to show any schematics or provide any specifics" while having a low post count and providing no other credentials is (a) teasing, (b) a little suspicious and (c) a little pointless. If you don't have a legal reason for not telling people how it's done (like if you had a contract with the people you told to shove it), why tell anyone at all?

I'm going to go with "I don't see the point of this thread" as well.

Edit: also, the law is not in your favor if you created intellectual property on the job. They may have the rights to it regardless of your giving them your OK to use it.

[Gus]

I posted something at this forum in the past.
There was an 80's? Fender amp with a Jfet preamp that I based my post on.

There are a few circuits you could use.
 
However when one parameter varies in a jfet what happens with the other parameters?

You did not post the design constraints the circuit needs to work in.  Number of parts active and passive, power supply voltage(s), jfet(s) used, input and output resistance, etc.

Auto bias has been done in audio power amps.  Servo circuits and control theory have been around for some time.

[tca]

I posted something at this forum in the past.

Let me put it down for you Gus   http://www.diystompboxes.com/smfforum/index.php?topic=93817.0

Nice reading and very, very, instructive!

Cheers.

[aethertransit]

mu amp..

One of the few real answers on this thread.  ...

Seriously, OP, posting "I've discovered something that's of great interest to a lot of audio electronics people but I'm not going to show any schematics or provide any specifics" while having a low post count and providing no other credentials is (a) teasing, (b) a little suspicious and (c) a little pointless. If you don't have a legal reason for not telling people how it's done (like if you had a contract with the people you told to shove it), why tell anyone at all?

I'm going to go with "I don't see the point of this thread" as well.

Edit: also, the law is not in your favor if you created intellectual property on the job. They may have the rights to it regardless of your giving them your OK to use it.

I'm sorry but am I not allowed to start a conversation on this forum? And where does it say that I'm obligated to immediately post schematics of anything? You obviously don't work in this industry, and apparently you don't have anything intelligent to add to the conversation either.

[midwayfair]

EDIT: Forget it.

[drolo]

*getting some popcorn and sit back to enjoy the show*

[ggedamed]

[...]
I'm sorry but am I not allowed to start a conversation on this forum?
[...]

A conversation should have at least a topic.

[...]
You obviously don't work in this industry, and apparently you don't have anything intelligent to add to the conversation either.
[...]

You didn't add anything intelligent to your own conversation, so why would anyone else?
And who gives a rat's ass about working in the industry? The name of this forum is DIYStompboxes.com.

[merlinb]

I'm not interested in patenting decades old audio technology, just sharing it with people who will actually appreciate it.

But..you...haven't actually shared anything

So has anyone else figured out how to auto-bias JFETs for use in Fetzer Valve type circuits?

Yes, Mictester has. He's invented everything ever.

[aethertransit]

I'm not interested in patenting decades old audio technology, just sharing it with people who will actually appreciate it.

But..you...haven't actually shared anything

So has anyone else figured out how to auto-bias JFETs for use in Fetzer Valve type circuits?

Yes, Mictester has. He's invented everything ever.

Shouldn't you be writing a book about how to make friends in online forums right about now? I'm sorry you're butt-hurt that I don't feel obligated to blindly give out information before having a conversation about it first.