Schematic etiquette

[dennyg]

A friend of mine loaned me a Dr Z EGZ 50 head and was interested in having me draw up the schematic for him as he'd struggled to find it online - as I did.  Also noticed that Doug doesn't list Dr Z among his vast library. I assume some designers like to keep their schematics 'secret' - but I did draw up the schematic including voltages for my friend, and took a few high-res gut shots.  I thought some of you guys might be interested but didn't want to post on the forum without understanding proper etiquette with regard to sharing that type of info.  I could use some enlightenment on the topic.   

[tubenit]

I'll offer my personal thoughts.  IF it is a current production amp and IF one cannot google up the schematic then I would NOT post it publically.


I might consider sharing with a friend in confidence IF that friend requested to see it. And I would do that by email.


IIRC,  I think all of Doug's schematic library were already public with many of the amps out of production.


Others may have a different viewpoint.   With respect, Tubenit

[p2pAmps]

A schematic is like a recipe (if it is an exact copy) and could be considered intellectual property which could enter into a legal issue (Maybe).  You might contact DR Z and just ask how they feel about it before you make a move. 

My 2 Cents

[MFowler]

I'm building a backup EZG50 for a very active country player locally, I've been maintaining his EZG50 for the past 3 years.


It has some issues I resolved but a backup amp is a good idea.  Doc sold me a blemished EZG50 head cab years ago but after a discussion he decided not to sell me the chassis.  I documented the amp on my bench but a schematic would be nice for me as well.


Mark

[tubeswell]

FWIW Mike Zaite has already released a few of his schematics (in various posts a few years back over at the TAG site. You need to go over there to find out what.) He's usually pretty good about sharing if you ask him.

[kagliostro]

+ 1 for Tubeswell

if you do a search on the web you can find some Dr Z amp schematics and also some layout

Franco

[MFowler]

Doc gave me the board layout to post on TAG of the original Formula amp and I posted on this forum a few months back.


Mark

[tubeswell]

I'm building a backup EZG50 for a very active country player locally, I've been maintaining his EZG50 for the past 3 years.


It has some issues I resolved but a backup amp is a good idea.  Doc sold me a blemished EZG50 head cab years ago but after a discussion he decided not to sell me the chassis.  I documented the amp on my bench but a schematic would be nice for me as well.


Mark

Based on your layout sketch, here's my schematic sketch. I used my imagination to fill in some blanks, so it could be wrong in a few places.

[DummyLoad]

anything that you create and publish is yours if you reserve copyrights. circuitry does not matter unless some or all of the circuit are patented. if you copy (cut and paste) any portion, then you are in copyright violation. otherwise you are free to publish what you create.


--pete

[shooter]

you are free to publish what you create.

If you wake up and paint an exact copy of one of my works, a lawyer might disagree with you

[PRR]

> anything that you create and publish is yours if you reserve copyrights

It is yours and copyrighted upon creation. Copyright notice only gives small ammo when you sue an infringer; not legally necessary.

Copyright is generally applicable to semi-mechanical copies. If I look at your schematic, and draw my own, that copy is my own creation. Xerox is clearly copyright infringement. Photography is fun for the lawyers-- a photo can be near exact or very arty interpretation.

Copying painted artwork rarely falls into copyright suit. Few copycats can copy so exactly that their lawyer can't argue "creative input". The few who copy good usually get in trouble under the Fraud laws, when they sell their "genuine Shooter" to an unsuspecting buyer and the forgery is noticed later. And since such deals are done through dealers, the copycat may not be known or punished (or may say he didn't know the dealer was going to sell it false pretenses).

Opening an amp and drawing the schematic by inspection is quite legal.

Amp makers can *try* to protect trade secrets by potting in tar etc. But reverse-engineering is BIG business (in other fields).

That schematic in Reply #7 sure looks 98% cut-pasted Fender building blocks though not drawn by Fender (and probably tubeswell's own original drawing and copyright).

[DummyLoad]

you are free to publish what you create.

If you wake up and paint an exact copy of one of my works, a lawyer might disagree with you

that is humanly impossible: invalidates your statement. i can paint a copy of any artwork so desired and it is mine.


--pete

[MFowler]

I'm building a backup EZG50 for a very active country player locally, I've been maintaining his EZG50 for the past 3 years.


It has some issues I resolved but a backup amp is a good idea.  Doc sold me a blemished EZG50 head cab years ago but after a discussion he decided not to sell me the chassis.  I documented the amp on my bench but a schematic would be nice for me as well.


Mark

Based on your layout sketch, here's my schematic sketch. I used my imagination to fill in some blanks, so it could be wrong in a few places.

Thanks Pete I will print it out and take a closer look.

[MFowler]

32-32 can caps x 2
OT 5k5
Choke 155R
100uf/500v F&T caps x 2
50k bias pot
3A fuse
Droppers: choke 155R; 4k7; 22k; 10k
B+1 443vdc
B+2 389vdc
B+3 294vdc
B+4 271vdc


Plates 440vdc
Screens 439vdc

[shooter]

i can paint a copy of any artwork so desired and it is mine.

I totally agree, where I get hung up is when you sell it as a Pete original.  I know in todays world it's all semantics.  I nailed a Georgia Okeefe, On the back, I put Her name, the name of her work, then painted by dave.  On my amp designs, I typically document in "History" something like Bogner, PRR, Gibson.

I guess I'm more concerned about ethics than legality

[jjasilli]

I'm a lawyer but I have no professional expertise re intellectual property; i.e. copyright & patent law.  It's a specialty area of the law.


As a practical matter, sometimes there's just plain intimidation.  An individual or small business may not want to get involved in a legal battle with a bigger foe who claims a legal right.


Here's a helpful article:  https://www.legalzoom.com/articles/how-to-copyright-technical-drawings


My legal spider senses lead me to guess that a schematic of a circuit is not protected by copyright laws, nor does it need to be.  Rather the circuit may be protected by patent law, if a patent is filed.  The distinction is that, e.g., an architectural drawing or blueprint, in and of itself, is an artistic expression subject to copyright protection, even if the structure it depicts is never built.  OTOH, an el. circuit is a physical invention, which can be protected by patent law.  To do so there must be a working prototype, and a technical drawing depicting it.  The technical drawing is filed with the Patent Office (not the physical invention itself).  I suspect that such a technical drawing has no copyright protection; the circuit may have patent protection.  Patent protection stops others from copying the circuit, selling or distributing it, without permission.  The inventor does not care about the drawing, but rather about the physical invention.  Its technical drawing is publicly on file at the Patent Office for the whole world to see.


Roughly speaking, amp circuits from their inception in the 1920's or so have not been patented and are in the public domain.  Occasionally a builder files a patent for an amp circuit.  If a patent is granted, it is not clear that the patent would survive a legal challenge.

[tubenit]

jjasilli,

THANK you for weighing in on this!  I value the information and your perspective.  It is appreciated.

With respect, Tubenit

[PRR]

> guess that a schematic of a circuit is not protected by copyright laws, nor does it need to be.  Rather the circuit may be protected by patent law

Patents:

Patents are rare in guitar amps but there are several notorious ones. Fender patented several tremolo schemes. Peavey has some for euphonious distortions. Harley himself holds many. One guy holds a patent for very specific value oil caps in a circuit.

It is not possible to determine by examining the circuit if an amplifier used patents. (Some makers have noted patent dates on labels.) However your drawing can include patent details because that is the point of the patent system: the inventor exposes his invention in return for a limited commercial monopoly. You can build your own copy of a patented invention for study; you can't sell it. You can draw your own copy of a patented invention, or even copy the patent paper.

Copyright:

The schematic on paper is copyright just like a cartoon. I can cut Dilbert out of the paper and hang it on my door (I paid for the paper and Scott Adams got his part-penny). I should not Xerox (or scan/print) a Dilbert I did not buy.
<infringement, me bad

If I take pen/ink (or MSPaint, or PSpice) and draw a Dilbert cartoon based on one of Scott's cartoons, with my own personal differences, that becomes mine, copyright me. (However I can not sell it as an Adams Dilbert- that is both fraud and trademark bad.)
< bad art, mine, not infringement

I assume computer images, simply copied (what computers do best) are copy infringement just like a Xerox.

You can create your own schematic by examining an amplifier. If you did not sign an NDA, the amp maker has little cause of action against you doing whatever you want.

[jjasilli]

Patents are rare in guitar amps
Yes, patents are rare for amplifiers, radio's, etc. generally.  Why?  Because no one applied for them.  Many manufactures, RCA & GE for example, freely published tube data and circuit designs into the public domain.  I guess their reasons were to spread the knowledge base so they could sell more tubes and components; and to sell finished products, amps & radios, etc., which the ordinary consumer could buy with confidence that a local repairman could fix and maintain these products.  (One more recent and notable contrarian is Apple Computer who went "proprietary" with hardware & software.)

Back to schematics, I'm thinking the Dilbert example, while illustrative for copyright, might not apply to a schematic of a circuit.  Because, unlike Dilbert a circuit schematic is not an artistic expression.  I agree that one may not copy and sell the technical drawing of a patented invention.  But I'm thinking that this is intrinsic to the patent, and not to copyright law. 

I guess if an artist decided to make a painting or drawing using circuit symbols he could claim a copyright to that.  But there's no valid claim to a patent, because there's no invention of a functioning el. circuit.

When there is a claim to a functioning circuit, then this falls squarely into the area of patent, and not copyright.  IOW, you can't copyright something that should be patented, or patent something that should be copyrighted.  If there is an intellectual property attorney on the Forum, please chime in!

Because all the important amp & radio circuits are in the public domain, I have a hard time believing that someone could get a valid patent in this area.  Heck, probably everyone on this Forum has modded a circuit -- changed a component value; used a different type of cap or resistor.  The rub is that if someone applies for a patent -- claiming that this change is novel or a sufficient improvement to the prior product -- the Patent Office "in its wisdom" might issue a patent.  The validity of the patent remains subject to challenge; but it's expensive and time consuming to mount a challenge.

[DummyLoad]

r. smith, CEO of messy boobie has the patent on "simul-class" P-P finals. also filed and got a patent on triode/pentode mode switch in guitar amps. 


Patented Multi-Watt™ Channel Assignable Power Amp featuring MESA’s proprietary Dyna-Watt™ technology providing three power levels and two wiring configurations (Pentode/Triode) via independent 35/25/10 Watt Power Switches:


the latter patent is total bullS#!t.


many of the amplifier circuits we use today were patented by western electric, rca, marconi, etc., & they have long since expired. oh, and UL was patented by hafler et-al in 1955, but was actually invented and patented by by alan blumlein in 1937. he is also named on the patent for the long-tail pair, patented in 1936. he is also the father of stereophonic sound (binaural sound), patented in 1937.


https://en.wikipedia.org/wiki/Alan_Blumlein


--pete

[jjasilli]

Interesting that there were patents on some early, seminal circuits, but they have expired. 


If someone does hold a patent, or taken copyright steps, it shifts the burden of proof in a legal dispute.  Normally the claimant has the burden of proof.  But for a claim of patent or copyright infringement the burden shifts to the accused to prove that the patent or copyright should be declared invalid.  Even if the accused wins there will significant time, effort and money spent for legal & expert fees.  If the accused loses the case he will have to pay over all his profits to the claimant, and be forever barred from future violations. This expands on the intimidation factor mentioned above.

[PRR]

> patents are rare for amplifiers, radios, etc. generally.

Patent infringement played a huge part of early electronics history.

Remember that Bell Telephone claimed a defacto monopoly and cascaded profit by haranguing judges into broad interpretation of some pretty poor patents (and egregiously delayed another to take-up when the first expired). That inspired many inventors.

Everybody and their dog patented some radio trick. Some went unenforced, others were brutally enforced. And the upshot is that in WWI, the US government found that they could NOT do radio without infringing multiple patents (or invoking its Public Need, which it did). So after WWI, the gov said that if you wanted government work, you had to put your patents in a "pool". The original excuse for RCA was to be the office to pool the patents (RCA grew bigger britches later, under Sarnoff).

Licenses were issued broadly but not universally. The oldest WE licenses were separate for "pro" and "domestic", and you sometimes find such language on old tube boxes; also at least one old Fender paper. The custom of making the same tube under two numbers (6J5 1620) also relates to payment and rights.

Patents play a large part in modern electronics (*not* g-amps/pedals). A good Patent Portfolio is essential. If you step on someone else's toes, you trade some patent rights and call it even. OTOH there are patent sharks who hold key ideas in obscurity until everybody is doing it, then jump out and sue for millions.

A patent can be broad or VERY specific. There is no broad patent on the Steel Plow, which opened the agricultural wealth of North America. But there are thousands of detail "improvement" patents. And you could still (maybe) get a Patent on, say, using a #9 bronze screw in the bottom hole of the plowshare. The PO does not require proof that this is an improvement. (Indeed it may not be unless combined with some other invention.) Likewise they have granted patents on specific values of oil caps in an amplifier. (Easier to evade than to fight.)

http://www.muzique.com/clones.htm

> alan blumlein ... father of stereophonic sound (binaural sound), patented in 1937.

Prior Art

[PRR]

As for Copyright....

"Creation" does not require "creativity".

Note that the telephone book is copyright. There is case law. There is no creativity in an alphabetized list of names in a town. There is a lot of tedious labor in the creation of such a list. The courts protect the phonebook from wholesale copying.

The consensus seems to be that a circuit schematic should not "significantly resemble" the original. Don't copy, RE-draw! Tubeswell seems to have worked from a layout by someone else, so it would be odd if his drawing came out as much of a "copy". His hop-overs are huge. There are several points where I would draw it different (put the reverb chain in-line instead of stacked; likewise the power supply). The topology may be the same but the drawing probably is not. (Tho if Dr Z uses the same software and has the same style of layout, it might be.)

http://www.muzique.com/clones.htm

And as you say, and as Bell Tel proved for decades: the most tenacious lawyers can wear-down a judge, especially in technical matters that judges are not experienced in.

[shooter]

A patent can be broad or VERY specific

I heard, but haven't confirmed, there is a Company with 5 guys holds 80% of all current genetic strains of cloned marijuana in the USA

might be a growing Business

[tubeswell]

32-32 can caps x 2
OT 5k5
Choke 155R
100uf/500v F&T caps x 2
50k bias pot
3A fuse
Droppers: choke 155R; 4k7; 22k; 10k
B+1 443vdc
B+2 389vdc
B+3 294vdc
B+4 271vdc


Plates 440vdc
Screens 439vdc

Thanks Mark


2nd attempt (based on what I think you mean't LoL)

[MFowler]

Thanks Pete.


The 100uf/500v caps are wired in series with 220k balance resistors for total 50uf/1000v high for the GZ34 but that's how it is done.


The two 32-32uf can caps are used for the rest of the tone board B+


Mark

[mresistor]

I'm sure you meant 50uf for the series capacitance.

[bnwitt]

Are those chassis pics from a German website?

[MFowler]

I'm sure you meant 50uf for the series capacitance.

Yes thank you I edited my post

[MFowler]

Are those chassis pics from a German website?

Yes Berry but I'm in a local EZG50 regularly and that's where the crude layout came from.

[dennyg]

Based on the above dialogue, particularly of note that this amp is basically a well-built version of a twin reverb plus a parallel triode mixer final stage  (which I think is unique but never owned a fender of any type), attached is hand-drawn schematic with voltages from an EZG50.  Pre-amp only - the PA is a standard circuit.  The discussion has been an informative and entertaining thread.  One other relevant note - a friend of mine played my TOS over the holidays and fell in love with it and  asked me to build one for him.  I recon if Jeff wanted he could request sharing in the profits, only that I'm building it for cost of parts so ain't none to share. 

[kagliostro]

Not very much, but may be a bit more readable



Franco

[shooter]

I'm building it for cost of parts so ain't none to share.

that's my best "defense" against suits, I have no money, I made no money, go squeeze a turnip

[DummyLoad]

in a nutshell:
1) B+ for reverb driver is not fed from G2 PS tap - has it's own RC tap
2) B+ for reverb recovery and mixer amp have their own PS RC tap.
3) B+ for preamp stage has it's own B+ tap.
4) add MV between mixing amp and LTPI.

so, a PS tweaked twin or super without the tremolo (6 PS taps total). IMO, that is how fender should have done things with the PS rail from the get-go.

--pete

[PRR]

> plus a parallel triode mixer

No, not parallel. Yes, two tubes in one bottle, and two cathodes on one cathode R-C. But they do two different things. Part 1 is reverb recovery. Part two is mixer recovery. Sharing a common cathode network here, two sequential stages, "can" be bad (but saves a dime). If Fender ever did it like this, he probably had large loss in the reverb side of the mixer (ISTR a 50K pot here for trem-roach).

Pete sees other fine details. I cling to my claim it is 98% Fender "inspired" (copied). A few changes such as Fender and EVERYBODY else did from time to time. If DrZ has special magic, it is parts selection, build quality, speaker choice, and chassis color.

[MFowler]

An old Tone Quest Report show why Dr Z uses a different chassis. He used to work on CAT scans at Cleveland VA Hospital he told me.


 In medical electronics, the FDA is very concerned about ground leakage. You can’t scan someone who might be hooked up to life support equipment and risk shocking them, so ground current has to be very, very low. One way we got around that is by using chromate-converted aluminum. Aluminum is already a very good conductor, but the chromate conversion raises conductivity almost to the level of copper without the cost of a copper chassis. The higher conductivity allows for better grounding, better earthling, and when I did this with my amps they were clearly very lively and bouncy with that chassis.
 

[tubeswell]

... chromate-converted aluminum. Aluminum is already a very good conductor, but the chromate conversion raises conductivity almost to the level of copper without the cost of a copper chassis. The higher conductivity allows for better grounding, ...

Good information. Thanks Mark.

[kagliostro]

Aluminum is already a very good conductor, but the chromate conversion raises conductivity almost to the level of copper without the cost of a copper chassis.

If I remember correctly, the galvanic process to chromate aluminium isn't so easy, so, before to give it the chromium bath, it has a bath on copper that cover the aluminiun with a very, very thin layer

I think this thing can contribute to the low resistance of such a chassis

Franco

[PRR]

> chromate conversion raises conductivity almost to the level of copper

If you think it works, that works for you.

It is only on the surface. It can't raise the bulk conductivity much.

The classic chromate is now essentially illegal (toxic baths). May be special-cased for medical scanners, not amp chassis.

I remember copper plated steel chassis. Very classy. Did resist rust a bit better. Solderable.

[drew]

From the Dr Z website:

The seed of the amp came from a new 6L6 output transformer designed for Z Amps by Ken Fischer. The output transformer has a very unique impedance not used by other American amp makers. This is one of the key factors to the EZG-50s sound.

Marketing twaddle or ... ?

[MFowler]

I have the correct OT for EZG50 and used a Mercury PT a friend had of which he had no more use for so I bought that. Voltages will be spot on with that.


Mark

[MFowler]

The type of pots used in the EZG50 were mostly incorrectly assumed as Audio by most.


I had to remove the pots to clean up the chassis pot grounding so I took a photo so show all but one is Linear taper.


Pre Volume A1M
Post Vol      B1M
Treble        B250k
Mid            B10K
Bass          B250k
Dwell         B100k
Mix            B250k


Mark

[pdf64]

I've noted the feedback resistor as being 820 rather than 27k.

[tubeswell]

Further schematic tidy up revision from various sources - mainly Mark and Pete (pdf64). Should be just about there I reckon

[MFowler]

Correct the NFB resistor is 820R

[PRR]

> Correct the NFB resistor is 820R

The ratio of the *two* NFB resistors is usually 4 to 40.

The 820:47 pair is ratio 16 or 20, plausible.

A 27K would likely be worked with a few-K resistor to ground. This is probably the 5K used with a Presence pot. (Since you can't buy 47 Ohm pots easily, and the cap value would be huge.)

[tubeswell]

Yeah I think the 27k got on my 1st quickly cobbled iteration because I uploaded a grouped component for 'Output and NFb loop' from my 'macros' library where I have a 27k/1k5 NFB loop initially, but forgot to change the '27k' label before I published.