IC Circuits or diodes or whatever.... that will imitate tubes

[Single Coil]

Let's say you have a Fender Bassman Amp that uses 6L6 tubes, and you want to use the amps circuitry as is but you want to design circuitry that imitates the function of the 6L6 tubes. Or Marshall amp that uses EL34's or EL84 tubes.

Is anybody doing anything like this...designing real tube alternatives? I really don't know what the function of a tube is in a tube amps circuit, but if I did know and was smart enough, that is where I would focus my endeavors. I wouldn't simply look for ways to replace tube amp circuitry, I would look for a way to preserve tube amp circuitry and just figure out a way to replace the tubes.

I guess that the problem with making tubes besides that fact that they're way outdated technology but the mercury and heavy metals used in manufacturing tubes is the real problem otherwise we'd have a host of boutique tube makers in the US along with the pleathora to pedal makers. Hence, we need environmentally friendly and tonally acceptable tube alternatives.

If I can solve this riddle, I can be a rich man. I need some help getting started....

[tiges_ tendres]

If I can solve this riddle, I can be a rich man. I need some help getting started....

if you read here a little more, you'll find why people love tubes so much.  Best of luck with that whole getting rich thing!   


http://www.runoffgroove.com  THE website for tube sims.



P.S  The transistor, developed as an alternative to the tube was invented in 1947.  Again, good luck with that getting rich thing.

[JimRayden]

...and then, Man created... [drum roll]... transistors.

Transistor is quite well known as a copier of tubes' main function - amplification. Transistors are also very much cheaper and many times smaller and also don't include mercury nor heavy metals. This little device is environmentally very friendly and tonally quite acceptable tube alternative.

...and the answer to your prays... comes from the labs of ROG... the engineers of silicon, the masters of Field Effect....

Fender Princeton: http://www.runoffgroove.com/professor.html
Marshall 18W: http://www.runoffgroove.com/eighteen.html



---------
Jimbo

[R.G.]

I guess we just have to post this from time to time as new crops of beginners come in.

(1) Tubes have a number of practical disadvantages, such as high cost, large size, high power use, fragility, and so on. This has been recognized since before there was any alternative to tubes.
(2) People have been trying to replace tubes ever since before this was possible. Tubes HAVE been replaced everywhere there was an acceptable alternative, since the first transistors became available.
(3) One could logically conclude that since people still put up with the practical problems with tubes for guitar amps and certain special hifi amps, there logically must be some part of the tube sound that cannot be replicated by other means.
(4) One could further logically conclude that since tubes are not obsolete in these few applications, it is not possible  to satisfactorily replace them. The existance of a fragile, power hungry, big, costly item in certain niches pretty mudh proves that.

And this chain of reasoning has proven true.

There is no generally acceptable way to replace the sound of tubes with anything else known.

It has been accepted since at least the 1970's that the guy who could replace tubes in guitar amps could become rich and famous. Many have tried, even claimed that they did. But the tubes are still here. What does that tell you?

And finally: JFETs are not tubes. JFET emulations of tubes can be nice sounding things, but they are not "just like tubes" and they don't sound just like tubes. Enjoy FET emulations for what they are, not for the tube sound they may approach in certain circumstances, but don't in general have.

Welcome to the effects world, and dig in, do some reading (OK, a lot of reading) and get building!

[Single Coil]

LOL. Thank you all for the encouragement to read, build, and get rich.

Perhaps the reading you have suggested will answer my main question. The tube alternative replace the entire tube amp circuit. I'm suggesting keeping the circuit and replacing only the tube. i'm sure that this is not a novel idea, but I haven't seen it discussed directly. Simply take out the 6L6 tubes and plug in a tube replacement...does ROG and the others talk specifically about that task? Can a transister be plugged in directly where the tube has been removed from. apparently it very likely has but hasn't sounded as good as the tubes, eh? Of course not! Thank for at least entertaining my post.

Thank you.

I won't be quitting my day job anytime soon.

[R.G.]

I'm suggesting keeping the circuit and replacing only the tube. i'm sure that this is not a novel idea, but I haven't seen it discussed directly.
Simply take out the 6L6 tubes and plug in a tube replacement...

There have been some attempts. For instance, some of the Marshall Valvestate amps kind of almost try to do this.

I have toyed with the idea of  replacing a power tube with a power MOSFET; i.e. replace a 6L6 with an IRF820 or similar, keeping the power transformer. However, I don't expect that would really sound all that tube-y.

does ROG and the others talk specifically about that task?

Maybe. Mostly the circuits at ROG replace the intent of the tube with JFETs in similar tone-EQ'd circuits. It's an OK sound, but if it were the equivalent of a tube in tone, there would be no more tubes, they'd already all be JFETs. Right?

Can a transister be plugged in directly where the tube has been removed from.

In some cases, yes. See "MOSFET Follies" at GEO - http://www.geofex.com. But this is a very, very limited replacement application.

apparently it very likely has but hasn't sounded as good as the tubes, eh?

Not yet, and people have been trying for the last forty years. But someday...

[petemoore]

  I believe the 'getting rich' has occurred, replacing tubes with transistors.
  Early transistor amps could be sold as 'amps', many who bought them still don't know SS from Tube, when asked "Is that a transistor or tube amp" they say 'I don't know'
  The ability to markup an SS amp...well manufacturing them can be a much less expensive undertaking. I believe Fender, MArshall, Ampeg, Peavey...and probably ALL other major amp Mfr's jumped on the 'markup the SS amp price' bandwagon, [because they had to to compete mostly I theorize], pumping out less and less expensive ways to manufacture using less and less human techniques...the money was probably good for all of them, but all of them...'playin' poker' [competing against one another] probably found out that after a while the 'mark-up-ability' in turn became less and less as greater numbers of low prices alternatives produced by the competition forced 'less markup' in order to sell them.
  Like RG Says, ever since those 'less than desirable in many respects' tubes were first built, people wanted alternatives, produced *alternatives, time wins...there may never be a REAL substitute for tubes...even as dangerous they are to work with, fragile, undependable, expensive...those who love tubes...like me...still buy *tubes !!! [and...I HAVE tried SS, Digital, and .. nope..just SS and digital as alternate to *tubes]
  "And, 'sounds *Just Like a tube amp'...[not]...well, maybe under certain, very specific conditions, or 'in a certain way'. Throw a FF in front, and all that "Works Just LIke a Tube' text or claims can be thrown out into the wind.

[burnt fingers]

Sorry but Line6 is already beat you to it.  They've mastered the whole tube amp modeling thing and are getting rich off it. 

[JimRayden]

It has been accepted since at least the 1970's that the guy who could replace tubes in guitar amps could become rich and famous. Many have tried, even claimed that they did. But the tubes are still here. What does that tell you?

Besides, isn't that the goo what 99 percent of guitar industry is swimming in? At least the distortion part of guitar sound. ALL of them try, very few get close, close to none of them succeed.

And finally: JFETs are not tubes. JFET emulations of tubes can be nice sounding things, but they are not "just like tubes" and they don't sound just like tubes. Enjoy FET emulations for what they are, not for the tube sound they may approach in certain circumstances, but don't in general have.

JFETs were referred to because he was looking for a direct drop-in replacement for tubes. And JFETs are the closest. Although tonally as satisfactory as any other transistor circuits (not enough for tube fans), this is the only attempt at directly copying a tube circuit into a stompbox.

As the tube amp circuits were designed around power-hungry glass containers that act "funny" when driven too hard, it's quite complicated to get the same results without the vacuum, heater filament or heavy metals.

So, Mr. Coil, if you could talk Mother Nature into bending some of her Laws for you, you might succeed "getting rich".

-------------
Jimbo

[spudulike]

Using the search function I found this

http://www.diystompboxes.com/smfforum/index.php?topic=25368.0

with significant contribution from the owner of Bluetoneamps who is marketing  a FET tube-sounding amp.

www.bluetoneamps.com

I think a lot of your assumptions are coveredin the topic.

[Single Coil]

Sorry but Line6 is already beat you to it.  They've mastered the whole tube amp modeling thing and are getting rich off it. 

Ratts! :Smack: I knew someone was going to beat me to it...I'm too slow. Oh, Well.

Spudulike, thank you for the links....I'll check them out.

[Single Coil]

So, Mr. Coil, if you could talk Mother Nature into bending some of her Laws for you, you might succeed "getting rich".

I'll see what I can do.

You are very informative and encouraging. If I do "find" the solution, I'll be sure to reward those of you who have encouragingly responded to my thread.

Cheers!

[Connoisseur of Distortion]

actually, i see this as being a very reasonable, possible idea.

what i picture is a discrete (or not... w/e) circuit, built on a stack of perfboards (or pcbs... w/e) epoxied into a canister with a male tube connector on the bottom. do i understand this properly?

looking at the work done by LXH2, you could probably create something that responds very much like a tube... their marshall simulator is very impressive, i'll say.

your problems, though, are pretty dire. first, you'll need parts that can handle the hellish voltage of a tube. this alone makes your build a frickin' mess, because it now has 300 or so volts... and good luck finding a cost-effective tranny/opamp that will handle 300 odd volts! also, you will want some HV caps, and these tend to take up some serious space... not to mention some noteworthy money.

the advantages? killer headroom, cheaper parts, longer lasting parts (i think... most SS lasts hella longer), CONSISTENCY, etc.

if you're up to it, do share your notes. i'd be interested to see how it all works out.

(i have faith in SS) 

[reverberation66]

yeah, I'd say go for it if that's your particular fancy, in reference to non-tube tube replacements.  I don't think it's gonna make you a rich man however.  Part of the reason for making solid state amps in the first place was the accompanying circuitry was cheaper.  If you would make essentially a tube amp with tube alternatives it would be as expensive as a tube amp.  Why not just make a tube amp?  But I like to be encouraging, I certainly like to explore weird audio ideas just for the sake of seeing what will happen so like I say go for it.  But there's a reason they still make tubes and tube amps even though there are cheaper alternatives with far more options and features...

[R.G.]

Sure - go for it.

Let me get you started.

Of all of the solid state devices, the JFET is closest to at least one tube - the pentode. But ordinary JFETs won't stand the high voltage.

So use a JFET you select as being as tube-y as you can find, then use a high voltage MOSFET to cascode the tube. The MOSFET is connected with its source to the JFET's drain, and its gate held at some fixed voltage above the JFET's gate. 12V is convenient, and gives room for the compliance of the JFET source and the JFET's drain movement. A zener is convenient for this. The MOSFET is then working at the same current as the JFET, but its high voltage drain holds off the ... well, high voltage. Suitable devices for the MOSFET are  the ZVN0540A devices. These are TO-92 packaged MOSFETs that will support 400V on the drain, can conduct 90ma, and dissipate 700mW. You should be able to replace a signal pentode with that. If you could figure out a way to amplify the whole JFET triode region from only a few volts above 0 up to several hundred, you could do a convincing simulation of a triode.

I've hacked at that a bit, but never got anything that sounded like a 12AX7.

If you could get a current buffered JFET that would do up to a couple of hundred ma, then the same setup above, a cascoded JFET, would work for simulating a power pentode. Some of the high voltage TO-220 power MOSFETs would work for that. The problem here is the low current rating on most JFETs. I don't know of any that do more than 50ma. Maybe you could do something with paralleled matched high current JFETs. A more likely scenario is a current buffer. You watch the voltage across a sampling resistor on the source of the JFET and force that amount of current to be let through a much smaller resistor controlled by a high current device and the "watching" circuit.

Might work out. I'll go sim it out.

But I bet it won't replace tubes...

[R.G.]

Hmmm... the current multiplier does work - in simspace at least.

I guess now all's I gotta do is multiply that JFET triode region out to about 200V from 1V and I got it licked. 

[Connoisseur of Distortion]

wow, RG. some guy brings up a topic, and you walk in and answer it?    will it work in 'the real world'?

1V to 200V... 

if only we had some sort of device that could use a relatively small current to control a significantly larger current... 

[aron]

Those JFET designs that are based around "amp circuits" don't sound like the real thing. They may sound good, but they are not like using tubes. The first real honest to goodness full circuit "emulation" of an amp AFAIK (from my time) came from Jack Orman. He was the first to put it all together - right in front of us, full blown 3 band EQ, voltage dividers, JFET stages, the works and it sounded great. I still have mine in the box. After that it was fairly easy to apply the principle of applying JFETs to standard amp circuits. Since then, Joe Davisson has been doing amazing things with transistors as well. Pritchard amps are supposed to be tube emulations as well. Of course Line 6 does it a totally different way as well. Yeah, if someone had a drop in replacement for tubes and it sounded better and cheaper, that would be amazing.

[burnt fingers]

Take a look at this.  I think if mesa couldn't make it work well enough to continue it you may have a long road.
http://www.jt30.com/jt30page/micKqanda/What-is-a-Fetron.html
http://www.mesaboogie.com/manuals/Mark%20I%20Maint-Repair.pdf

[Peter Snowberg]

Electro-Harmonix is producing RoHS compliant tubes.