I tend to agree with the manufacturer on this one. Think of it from their perspective. There are a lot of companies that just build copies of equipment using cheaper components and less rigorous manufacturing *cough* behringer *cough*

Think of it this way, if you spent tons of money and time building the best headphone amp in the world and someone got a hold of your schematics and started building knock-offs, how would that make you feel?

I don't think it's that common for companies to give out their schematics, code, or build process, is it? I could be wrong.

In electronics a schematic is the only thing you have to protect your unique design other than a patent which can be very difficult to get for electronic circuit designs.
In many cases common circuit designs are built up from design cookbooks, electronic handbooks and spec application manuals and aren't that unique or proprietary. But if the designer comes up with a unique way of achieving a certain circuit and it has market value in a product that sells because of it's unique design, the designer will always protect that "recipe" from prying eyes. Potting circuit boards is the best way of protecting a design or preventing reverse engineering. Hmmm......alien ship guidance circuits anyone?!
It's really no different than intellectual property in software coding or trying to pirate or hack software stuff. If you want to design electronic circuits learn how to do it and create your own designs! Parrots and copycats are not very well liked....if it's a troubleshooting issue and the warranty has expired dig out a scope and meter and fix it. Most audio gear in general is pretty simple to sketch out and trace if the components and board is exposed to the light of day.

Typical yes, but how ethical is it? I think that it is this "its a secret, hush hush, don't look behind that door" kind of business attitude that is the downfall of the professional gear market, and one reason why cheap knockoffs typically win. See, there are two possible idealistic outcomes to this situation as I see it.

1. They send me a schematic and I look it over, I say "ok, this is a superior/unique product, I can see that there was some thought that went into its design and I feel justified having given my money to you.
2. They refuse to reveal their work to me even though I gave them money. I am somewhat offended and out of spite I trace the circuit and draw up a schematic and find that it is a API 3124 knockoff with less power filtering, certain parts of the design removed, and modern day cheapo parts and opamps used. Basically, a sham. And I realize exactly why they didn't want to show me their schematic in the first place, they stole the design and showed no intuition of their own other than cost saving.

Now these are extreme cases of course and not every case falls into these two categories, but as I see it, sound is sound. If you've got nothing to hide then don't hide it? Basically, what they are saying is that I should buy their product simply because of what they've told me about it through marketing.

The entire professional gear market is full of this. For example, I think that most modern day boutique guitar amps are shams, they are modern day Marshall clones with choke input power filtering and increased bass response and they charge upwards of 3-4k for this design. Unique yes, useful maybe, worth 4k? Don't think so. Now the Soldano SLO on the other hand, that amp was ahead of its time, and the schematic shows it. There are SLO knockoff clones available for much much cheaper, but the way I feel is that the SLO is completely worth every penny asked for because the engineering was ahead of its time, and I will buy into that. Got off topic a bit, but if I am using a piece of gear which I paid for I think that I should have at least a basic understanding of the circuit layout and what it is doing to my sound. Corporate wise anyway, I would feel differently if I were buying a small business product.

If you've already bought the gear and are happily using it....why do you want the schematic?
They have no obligation to supply you with anything. It's not your product or warranty.
Especially if your talking about high powered amplifiers with tubes etc. There may be safety issues and liability that have a part in the product unknown to the user.
i.e "No User Serviceable Parts Contained Inside"
If you really have to know what components or the circuit design and it's not potted or hidden from view just figure it out yourself if you are so inclined.

I agree with those who say we don't have any right to a schematic. However, I definitely prefer to deal with companies that are very transparent about their design. Basically they are saying that there is no real mystery about the circuit they are building - they can just build it better than anyone else.

BobRogers, post: 372567 wrote: I definitely prefer o deal with companies that are very transparent about their design. Basically they are saying that there is no real mystery about the circuit they are building - they can just build it better than anyone else.

Well said.

I don't think it's an ethical issue at all. The company is protecting itself. Let your ears be the judge.

As a guy who spend a great deal of time staring at schematics, I think a schematic only tells a bit of the story. The schematic gives the design intent, not the actual finished unit.

People will always be able to copy the gear. The schematic will certainly help give that fake copy a jump start, but it will not help in the manufacturing methods. Which more often are what define the properties of the product. How you assemble the unit is critical to the units specs. This is why so many cheap knocks off, never equal the real thing.

Anyway..... should a company try to protect its intellectual property? Of course they should.

However as a repair guy, I would appreciate a copy. Maybe I have to buy it, maybe I don't. But if you make it available to me as a repair center, It make you product stay viable longer.

Most companies have no problem issuing a repair center a schematic.

From a business standpoint, this has always been a proprietary issue.
Many times in electronics it is merely a clever use of components and there interconnection within a more common design circuit that constitutes that unique proprietary design. Sometimes this is what gives the companies product it's unique edge or niche in the industry. Because electronics is so well understood, engineer's will approach the basic circuitry from a different perspective or from a different direction. They will derive interesting and sometimes eloquent results by combining elaborate blocks of control or stability making the design function better than the basic circuit. Sometimes using higher tolerance expensive components achieve a finer design or regulation or in the case of audio better sound characteristics. This all takes time and expense to build and test. Some circuit designs when they work and provide exceptional results become very prized possessions under lock and key. The design stands on its own merits because of review and use by other professionals in that field using the device in question. And don't think competitors don't go out and buy one and try to find out what they did to achieve those results...they do!
So I think you can understand why some companies are either very reluctant or in many cases will never release any schematics or drawings of their product to the public and in some cases to anyone.
This is not because they are shady or not being transparent. The name and reputation is all the transparency you should need because in electronics it either works as advertized or someone will call your bluff. Companies who have been in the business a long time have nothing to gain by deceit or circuit stealing. It is the company with a poor reputation and inexpensive knock off products that are the ones to be leery of.

Guitarfreak, post: 372553 wrote: I have recently emailed a corporation company, which I will not name, and asked for a copy of the circuit schematic for a piece of equipment that I purchased from them. They emailed back and refused to send one to me because, and this is verbatim "Schematics for all of our products are proprietary and we do not release them to the public." I was rather put off by this, especially because I had purchased the product from them already, but either way it shouldn't really matter.

Curious to hear your thoughts on the matter.

Guitarfreak:
I don't think there's any harm whatsoever in you listing the product or company your talking about. That information isn't proprietary....except to you. By you not revealing what company or product your talking about only places you in a skeptical position.
In revealing the product or company you will find many people on here better understanding why that particular company's reluctance to share the information with you!
It will also stimulate further discussion on the nature of your interest in that particular products quality and shared open knowledge from other members.
That is the more transparent approach on your part and places you in a position of more open honest interest rather than any hidden agenda or deception on your part.
Just thought I would mention that....

djmukilteo, post: 372690 wrote: Guitarfreak:
I don't think there's any harm whatsoever in you listing the product or company your talking about. That information isn't proprietary....except to you. By you not revealing what company or product your talking about only places you in a skeptical position.
In revealing the product or company you will find many people on here better understanding why that particular company's reluctance to share the information with you!
It will also stimulate further discussion on the nature of your interest in that particular products quality and shared open knowledge from other members.
That is the more transparent approach on your part and places you in a position of more open honest interest rather than any hidden agenda or deception on your part.
Just thought I would mention that....

I don't know where you are coming from with this, but I am not one to publicly bash another's work, as I would hope others would not do the same to mine. I hold my ground about not mentioning said company as I am not in poor or bitter standing with them and even if I were, it is not my place to speak out about them in the first place. I am referring to the concept at work, not the company utilizing it. If anyone would like to have deeper conversation about my particular situation, then they can reach me via PM and I will explain there.

Thanks
-Jake

Guitarfreak, post: 372697 wrote: I don't know where you are coming from with this, but I am not one to publicly bash another's work, as I would hope others would not do the same to mine. I hold my ground about not mentioning said company as I am not in poor or bitter standing with them and even if I were, it is not my place to speak out about them in the first place. I am referring to the concept at work, not the company utilizing it. If anyone would like to have deeper conversation about my particular situation, then they can reach me via PM and I will explain there.

Thanks
-Jake

GF:
I know where I'm coming from and I wasn't trying to cast some doubt on your intentions.
You said nothing about bashing the mystery product or company in your original post and neither did I.
That's the whole problem with your post in the first place.
Whenever someone wants schematics for some electronic circuit that is out in the marketplace whether it's old or new, it immediately suggests that the person looking for this information appears to be looking for something.
It's not a normal thing to request. Maybe you just don't understand that. You appear to be someone trying to gain information with some motive. If you were looking for repair schematics of an old piece of equipment and they were never published or available then a search or forum request would be totally appropriate. If it's a newer product and people know of it then perhaps there are people who have looked into that product and know something that would satisfy your curiosity or interest. But then without the name it's pretty hard to understand any of it. I mean even repair centers are not allowed to release schematics or repair manuals to the general public and there's a reason for that.
This is a money making thing and the longer you can keep the hounds at bay the longer you will last in the marketplace....simple business strategy....
It's not some conspiracy or design deception....which I think is what you're probably curious about.
When you state you won't list the product or company what is it you hope to gain by making it a mystery?
You have no liability in revealing public companies on a public forum or who your talking about?
You don't even have a right or responsibility to protect any of us from their name!
Not that I care....it's your discussion....but the whole way in which you've approach this appears to be that of a fiddler or hacker who is trying to gain insight into some product that you probably don't have any rights to. So all I was trying to point out is your indignation with not revealing any names just makes you look even more suspect....
I hope you understand I'm not attacking you...I'm pretty sure your intentions are legit and over the time we've had conversations here I just feel you may be somewhat naive to the corporate attitude of product protection and then of course the motivation behind your apparent attitude to the access rights to a particular companies schematics.
I hope you weren't offended....

I am trying to learn about preamp design so that I can either a. Fix the tonal issues that I have with this one, or start from scratch with a new design that would better suit my needs. I am quite used to modifying effects pedals to suit my own needs as schematics of popular effects units are abundant. Mic preamp designs seem to be an art shrouded in mystery potentially barring curious people like myself from learning that which we desire to learn about. Just an observation.

They are not that complicated, what are you trying to do?

Link555, post: 372703 wrote: They are not that complicated, what are you trying to do?

Dont know really. I know what I dont like about the preamps that I am using and I feel that if I had a schematic to look at I would be able to find out the source of what I do not like about it. That, or I would know that I would have to break from the design to achieve what I want tonally. Its a PreSonus FireBox. The unit is fine and of surprising sound quality for its price point, but I want to learn how to make it better or design something better.

well usually those types of units use a single chip pre amp solution. I am not sure the presonus does, but If I had to guess....
anyway that makes it hard to mod whats in the chip, you can however play with feedback based filters to affect the frequency response of the amplifier. But remember for every gain there is a loss. A good preamp design takes lots of listening.... How is your stability theory? Do you know your poles and zeros's?

GF: I think it's unlikely that you will find the source of what you don't like about sound of a pre-amp by looking at a schematic. As Link pointed out, the basic architecture of most pre-amps is pretty standard for their type (valve, transistor, IC etc), and it's often the intricate detail that makes the sound different. These details include the interaction between the elements of the circuit (schematic) and their implementation in components, wire and PCB, and the implementation is not represented on a schematic.

It's perfectly reasonable for a manufacturer to be protective about his schematics, especially those of current products. Those that have got out into the public domain may be there despite the best efforts of the manufacturer to guard them. Even those of us that acquire circuit and maintenance details of products under NDA (Non-Disclosure Agreement) do not necessarily have access to the internal details of certain ranges of products, particularly those that have only a return-to-factory repair clause.

I appreciate the advice. I am a bit short on project applicable cash right now, but in the near future I would like to build a decent quality preamp design that I could tweak a bit to my desires, as well as an external power supply with which to power it with. Any advice or direction?

I found this design schematic from a website and it looks pretty interesting. It is supposed to be a symmetric amplifier with asymmetric shaping post gain. Cool idea? Possible to make the asymmetric aspect switchable?

http://www.sonelec-musique.com/images/electronique_preampli_micro_005b.gif

I also want to get some advice on transformer input designs, I think that would be a step forward for me.

Thats a single supply amplifier.... x 2...... Are you looking to make a op-amp based mic pre with XFMR input or are you trying to mod an existing design?

Link555, post: 372751 wrote: Are you looking to make a op-amp based mic pre with XFMR input or are you trying to mod an existing design?

Specifics are not known to me yet. What I do know is that I have an assortment of microphones and I feel that my preamp is not doing them justice. What I hear is not what I think I should be hearing. I would like to build something from scratch parts that will make my dynamic microphones sound like they were meant to.

GF:
I'm sure you've done this already, but if not Google DIY Preamps and go to FiveFishStudio or SeventhCircle Audio.
Most modern solid state mic preamps are based around Op-Amps. There are tube based preamp circuits and a few "discrete" transistor preamp designs. Adding input and output transformers to the front end and rear end of these preamp circuits adds inductive balance, warmth and harmonic distortion which many people consider creates smooth tonal quality. The cheapest of these designs are the Op-Amp varieties.

You can go to Texas Instruments (Burr Brown), National, Analog Devices, Signetics, Linear Circuits etc.
The basic Op-Amp mic preamp design looks something like this:
[[url=http://[/URL]="http://www.zen22142…"]Op-Amp Microphone Preamp[/]="http://www.zen22142…"]Op-Amp Microphone Preamp[/]

There are literally thousands of different project preamps out there and the parts from Mouser or Digikey can be fairly cheap....it all depends on how serious you are and your budget....
You will need a dual output power supply for any op-amp preamp design the most common is a +15V/-15V DC regulated supply. Power supplies can also be highly regulated and designed to provide quality supply voltages and low noise for high quality preamps.
Audio transformers can be found online as well and Jensen has a website for their high quality audio transformers with impedance tables and prices.
The 500 series racks are all the rage and popular these days because these give you a high quality power supply rack unit (which you need no matter what you do) and then you can either buy or build different flavor preamp modules, compressors, EQ and even A/D/A modules and plug them in as your needs and budget allow.
The rack units go for around $500 and a typical preamp module can run as low as $400 up to $1000's.
Considering the Presonus or really any of the major interfaces, while these are all good quality low noise mic preamps they are still just op-amp based mass manufactured consumer vanilla solid state modules. They tend to be right in the middle of the specs with no design extravagants which is not needed for lower cost (pro)consumer grade audio devices.
Absolutely nothing wrong with them they work well and they do the job all day long.
I think you would have better luck adding a new preamp ahead of the Presonus interface rather than digging around inside and trying to mod some channels. Of course if that's what you want to do and risk losing the entire use of the Presonus that's your decision....just be aware things can fry, mistakes can be made and you might not like the results anyway and then you find yourself out looking for a new $1500 interface.
So....I hope this helps with your quest....I know you have that passion for this stuff, which I admire in people like yourself so I hope you weren't offended with my comments earlier. I wasn't trying to put you down or discourage you in any way....I really only wanted to help out and understand what you were thinking!
Sometimes being blunt, up front and coming right out and being clear is much quicker to the point and avoids confusion.
Now that we all know why and what you were pursuing it makes much more sense and is easier to discuss the real issue which is looking for that sound in your head you want on your recordings. LOL
And your not alone....we all have that problem....hopefully it will never go away!

Ok when your ready give me a PM I can let you know what stuff I found out the hard way ;)

For sure I have searched DIY preamp designs, but there is no guarantee of good sound so I was sort of hoping the good gentlemen of a forum such as this would point me in the direction of something somewhat audibly impressive. I really want to buy a Seventh audio or comparable preamp, but they are a little bit pricy for me right now and I wouldn't feel right modifying them, being vintage clones and all. I would rather build something from scratch and really put some time into it so that I could call it my own.

As for the power supply, if I were to make a fixed voltage power supply, wouldn't I just be looking at a transformer and a couple of pi filters? Is there more to it than that? I want clean power for my preamp. With such a sparse and open design such as a mic pre, the DC 'food' for the preamp could become much more 'tonal' than in other more loaded and compressed designs like a Tubescreamer pedal.

Simple stuff first what are your specs? What are you trying to achieve with your design. what type of circuit? What is the Gain, the noise floor? The harmonic distortion? Discreet? Fet? xfmr's?

etc.....
make some choices, then ask for help.

Guitarfreak, post: 372769 wrote: For sure I have searched DIY preamp designs, but there is no guarantee of good sound so I was sort of hoping the good gentlemen of a forum such as this would point me in the direction of something somewhat audibly impressive. I really want to buy a Seventh audio or comparable preamp, but they are a little bit pricy for me right now and I wouldn't feel right modifying them, being vintage clones and all. I would rather build something from scratch and really put some time into it so that I could call it my own.

As for the power supply, if I were to make a fixed voltage power supply, wouldn't I just be looking at a transformer and a couple of pi filters? Is there more to it than that? I want clean power for my preamp. With such a sparse and open design such as a mic pre, the DC 'food' for the preamp could become much more 'tonal' than in other more loaded and compressed designs like a Tubescreamer pedal.

Well unless you want to get busy studying advanced linear electronics with an eye toward audio bandwidths then the basic circuit I linked you to....it's only going to get you the basic circuit. $10 for a breadboard and parts and a $10 12V unregulated wall wart will certainly suffice. Your options for tone might be pretty slim and vague...changing caps, resistors or adding a transformer in the path but the basic design is just like your guitar circuits....they are what they are...there's nothing complicated about what works or how they work.
The more exotic you get the more expensive the parts become and the larger the circuit....transformers, board design, power supplies etc. Then there is the whole topic of test equipment, scopes, distortion analyzers, frequency generators/counters etc. in order to actually understand and "see" what you are changing and then making some subtle determination if this is actually something that's a good thing or a bad thing....electronic design is just as much math and calculations as it is experimentation. So having the proper lab tools is really essential....you can't always trust your ears, but if that's what you want to use as your reference tool.....that's fine.
If your truly interested in creating your own color in a preamp design or you just want to build your own preamp, your best route is to buy a decent bench/lab power supply, dual differential voltage +/-, variable voltage adjustment (0-40VDC is fine...anything above that gets a bit pricey) a circuit breadboard for easy changing of components and wiring, (use sockets for the opamp IC's) and start building preamp circuits using different vendor opamps which are specifically designed for low noise linear amplification from the different companies I listed earlier.
Get the hookup and application datasheets, get the pinout info and read through the application data, buy good quality components and then try them with each of your mics. You could try and stay under $100 maybe but the further you go the closer you will realize the price of certain manufactured or DIY preamp kits come down to a reasonable cost and you save yourself from trying to reinvent the wheel....which is what this is!
Also go pick up a good electronics cookbook from the library on Opamp audio circuit design....you will find plenty of information and discussion of audio circuits with important design parameters and elaborate/exotic designs that will last you a lifetime.....