OTA-Overdrive with genuine Germanium-Sound [130311-I] | Elektor Magazine

The publication part of the project is not equal to the entire book, but a larger "extended literature". For the "Elektor Electronic Magazine", there is indeed a lot to read about this aspect.

Therefore, the description of this article also explains-why and how-to benefit from the "leakage current of germanium-semiconductor components", which is often told only because of an unnecessary interference and error trouble, and this is falling into a certain special It is the physical factor for real use, directly from the generation of the preferred sound effects and through control of OTA-Currents. If you need support, just email me to jo2030_aeht_gmx_dot_net (English or German-reply will take some time, but every email will be delivered).

The circuit of the direct JFET buffer has been modified (two PNPs have been deleted, and the value of its Gain-Pot has been changed) because of an error in the dependence of Ubat. This is fixed.

The first released circuit can work, but the gain adjustment will vary with the audible value of the battery voltage, and the unit that is started earlier will require some modification.

If you are just printing the photo, the modification is easy to update, so nothing will be lost anyway.

Need to modify the battery usage (constant Ubat = Ext-Supply not required):

1. Completely remove Q1 and Q2 and connect the collector to the position of the transmitter

2. Bridge position of R35 and R36

3. Replace LD1 with jumper (bridge)

4. Connect the cathode of LM385 to GND

5. Change the value of R32, R33 to 10 kOhms (PT2-2 kOhms, may be changed to 10 kOhms)

6. Change the value of R34 and R37 to 560 ohms

7. Change the value of R31 from 6.8 kOhm to 22 kOhm

In order to get a better frequency response, I recommend changing C2 to a value higher than 1µF (it is better to use NP-Elko or "Samsung Hi-Qual Cercap" 4.7µF).

Multi-effect rack modules, as well as instrumentation amplifiers and floating diodes, are coming soon.

If you do not cool it down during the process, do not solder the Point-Contact-Diodes to the PCB as tightly as shown in the project Figure 2, because due to the micromechanics, this may fundamentally change the Diode- The data of Data (thermally effective) moves directly to the Point-Contacts inside the part.

Use wet cotton textiles at room temperature or similar temperature, but do not use ice cubes, etc., and do not use any air cushion before that.

Leave at least 5-10 mm in length on the diode pins on each side to optimize the cooling of the entire device when soldering.

You can also use crimping pins for this operation (as shown in the picture with the MD276 diode).

All this is preliminary and still in an experimental state. My simulation software says that all of this is ok, but it has not been tested yet!

The contribution contains a complete folder for downloading the entire update and more photos (will be changed soon!)-if you find any errors, please contribute to me too!

As stated in the project title, the real "real germanium sound" is generally considered to be very critical, but this means that it must be guaranteed by the working principle of the provided equipment and how to produce effects from the previously used components. Users can also get support from the administrator/instructor for this project here (please also refer to the text-I bought it under GE's antique and dusty shop, I bought a lot of GE-diodes from several companies for this project The supplier’s product may provide possible support for the selected/matched pair, as well as (maybe later provided) a prepared complete kit), and then achieve success on the performance equipment, which is for everyone who wants People who play electric guitars are very useful.

The project carried out a "more in-depth description" of the distortion effect, once again carried out a complete explanation of the actual use of OTA, and then provided some historical information and background of germanium parts, as well as some short stories or anecdotes.

In this way, this means not only articles and some explanations as technical publications, but also means to restore the interest of users, after all, to be satisfied with useful products that are practical and easy to implement, which also means real innovation. However, it cannot be a high-tech device, so it can be restored to the real "70s retro unit state" and continue to be used at certain times during this period.

Therefore, I want all readers to know that this project may have been published in the early 1970s, so this kind of thing came a bit late-or not? -The popular CA3080A-OTA was developed by RCA between 1967 and 1969!

(If you are interested in the amazing facts of this very developed and earlier industrial IC device, and are interested in this interesting background, then here is a link to Donald Tillman’s excellent website in the United States, which also has A lot of other very useful information in music electronics:

http://www.till.com/blog/archives/2005/06/last_of_the_ota.html

Like I think, this website is associated with a "must visit" for all guitar players!

)

The project described here shows all the ways to build an interesting and useful electric guitar overdrive device, one of which can be built on a weekend, the youngest electronic beginners can also easily complete it, and they are also ready to move forward like a guitar player And start.

For the first actual setup of the unit, the help of parents may then be needed to adapt them to the previously recommended and displayed PCBs, and then the text and all plans are processed step by step to make the final product achieve the desired performance. construction.

To start the project directly from here, the user only needs to know how the various parts of the schematic look like, and then glue them together to solder the single-sided printed board.

As the last addition to this project, I have tested the maximum possible conditions of all components on the breadboard and in the simulation program, and tested them under different conditions, and also performed some on different Spice models of the IC With changes, all the setting parameters of electronic components have been optimized to obtain the most commonly used units, which can ensure that they work as expected.

If the parts are fixed together, as shown in the layout diagram and schematic diagram, there will be no damage, so if all values ​​and positions are placed correctly and then connected to key parts, etc., it is vital. battery.

In order to enable the device to operate for the first time using only prints and some plugs, a jumper from the JP3-Pin1 jumper to the following terminals is required (a low-current LED LD1 for driving ota can be directly installed on the print on!). JP3-Pin3, but please be careful not to connect JP3-Pin2 in the middle, except for the cable shield of the foot switch.

The possible switches on JP1 and JP2 are only optional, if needed, and basically not needed at the first startup, so this situation can also be completely avoided.

In order to be finally fixed in the box, a switch for changing the diode path/sound is also provided. The plan shows the whole and the required configuration of the whole.

A pair of "anti-parallel diodes" are used to produce an overload effect, which is used as the main audio voltage generator to act on the sound product, and the modified guitar signal (Figure 1-VF1) is converted into different characteristics, flat Waveform (VF2) and interlayer are also called this effect, called "signal distortion".

If this effect is correctly achieved in a special way, the sound produced by the device will become very musical rather than disturbingly discordant, usually due to undesirable Any electronic device is caused by distortion. Most of these electronic devices are malfunctions, poor sound, scratching speakers, etc. Therefore, this effect is actually a different audio source.

In the context of the diode as the audio source, it seems electrically easier to perform this conversion with a "current source"-which is delivered by the OTA here-rather than ultimately using an operational amplifier for conversion. In any case, it will act as a working "voltage source", so it may cause more conflicts with the diodes and affect them. In the worst case, they will completely overwhelm their characteristics, so they may reject the preferred sound .

Based on these facts of the technology used, by driving a controlled current into the diode, the OTA can achieve functional coordination with the diode (the influence of the leakage current of the diode and its use are also widely considered!). . As the third component, it must be in the output component chain. This is a very high impedance JFET for the final required output voltage coupling.

Figure 1: Two diodes convert the sine wave of a guitar into different waveforms

At first glance, I don’t know much about getting it to work, but roughly speaking, there are many other things to say and know, because these settings have more reservations, backgrounds and possibilities in terms of the above distortion function. Therefore, the first description here should only be the basic nature of the subject and such main functional devices.

For the project, this is a difficult problem. If you look at most of the quotations for a few distortion and overload units, they usually come with an implemented and often needed signal output tone control chain. Normally, the user will A favorite position of all the controls is put together to achieve the best parameter structure. Each time it depends on the frequency range of the electric guitar used, so it is always independent. Therefore, compared to useful volume control, the required functions on the spectrum sometimes become more important, because part of the volume is also partially controlled by an external amplifier.

However, one version of this speeding project will be implemented without any tone control, and for the startup company, there are mainly three versions, all of which require the same PCB space:

Variant A-1: ​​All buffers implemented as JFETs (2SK30A-Y is preferred, can be changed to selected 2SK30A-GR, J112, BF245 or similar buffers), and there is no pitch control. There is only one used operational amplifier in the signal chain. If you are willing to do this, you should also pay attention to be able to control the frequency on a separate external device.

Variant A-2: Same as above, but with TLC272 op amp buffer (or TL072) to improve the availability of parts, as most TO-92 JFETs are becoming more and more rare, and sometimes may be completely obsolete.

Variant A-3: Both OTAs have subsequent op amp buffers, and the position is changed from "volume control" to the "tone control" used now, but ultimately has a JFET at the output of the device. This is the preferred method. For the first version of the first demonstration, there is no strict amplification part here, so users should perform this operation through an external device as needed.

Full description of all parts of this machine and most background

The final unit of the project on the PCB is not only some practical learning object, and then discard it, or even no longer use it, so it ultimately means to get a good sounding device for long-term daily use and bring a lot of fun.

Out of these interests, the project only describes the performance of a few but optimized electronic parts, and the PCB is prepared as a ready-made hand-sent Eagle-File, which can fit most existing "Stompbox- Flight-Case"-Like my first prototype, it was previously built in a simple bread box. In this case, it still depends on the use of friends and has been working to this day.

(In addition, and only provided according to user requirements, the layout of the PCB has been specially edited, and hand-made "teardrops" are optional on most soldering points to achieve true retrograde assembly and better electrical conditions. Monitor, as if the PCB was made on the basis of tape using the old layout technology of the early 70s, or simply painted with a glue stick.)

For users, this style means first of all to provide the best things and be challenged by innovation anyway. Regardless of the facts, both beginners and outdated Oldcrow face challenges in electronic products.

As a necessary supplement to the project background, this also benefits from the user's personal investment work, and then also benefits from some externally introduced and useful knowledge of the thing, which is collected on the components of each part and what knowledge is really needed The understanding of the structure of this equipment is not only as an electronic unit, but also almost as a musical instrument, combined with an electric guitar, so it is not only only required gears such as cables or other accessories, but also etc.

According to my personal experience, it’s hard to say for the basic equipment so required. With the help of my tutor and many other teachers, sometimes there is a little disadvantage when I am young, so I must always accept that such a performance chain is lacking. This is essential for these things, and then it is actually the fact that there is no money to buy this sometimes very expensive device, and it sounds great. Because of this, I was lucky at the time to be able to teach me how to do things and how to do things in my own words-in today's short words: DIY!

Therefore, another goal of the project is to solve those who will certainly not have enough money to buy high-quality electric guitars for start-ups, and the rights at that time, and now it really needs good guitar effects to play, because in the end, the guitar and The effector only provides a single music unit, and only when they work together and sometimes the user performs some well-performed and well-learned exercises, can it remain interesting. Power amplifier.

Picture 1: WN5457-1959-selected germanium-mostly do not look for high-quality germanium...

As the first major breakthrough of the project, this also means the challenge of the above-mentioned title and the sometimes very high price of such units (it should be said to be rough, the real uniqueness is becoming unique, and in each Under the circumstances, they are almost priceless!), so the used germanium parts have only recently been used since the 1970s, where they expect hundreds of euros or dollars, but then they can also do the job well.

It’s usually not easy to tell where the standard is on this information, or the difference is truly unique, so perhaps these prices are paid only for obtaining such high-quality audio equipment. In terms of classic sound and user satisfaction, but After all, we will still only use boiling water to make coffee-so to speak-when we look at the contents, every time there is a problem to taste what we see, that is, electronic germanium parts often contain some kind of garbage. Exterior.

Therefore, if the customer is first fixed on the device, then it is important to search for it with the special name of the known manufacturer, and then he can guarantee that he is satisfied with the product and can also guarantee the payment of the price.

Therefore, the word and slogan "germanium" is only a fact of internally used materials and technologies on the one hand, and on the other hand, it is necessary to start more rough machining, so you still need to choose, and maybe some other processing procedures. what is it then? Finally, it is also related to the name and quality/capability of the entire trademark or brand. At this point, the variability of DIY equipment is very large, and equipment owners can invest their personal qualities, efforts and capabilities here, which are also very important for the final product.  

A good example of these backgrounds is-for example-C. Chapman’s carefully prepared project "Elektor-Formant-Synthesizer", which can also be done in several ways (made by DIY, but also as a ready-made kit, There are also very good and pre-selected parts), which means that you can get acceptable results here, but it is also possible to get better results, and I have encountered a great instrument with very high sound quality and sound quality The ability to approach the legendary Moog-Synthys is even better. On the other hand, I also saw some formants, their sound is really bad, and the overall performance is also very bad. This is always right. It depends on only doing some work with them and preparing for the future. Get ready. Musical instruments are not only some electronic devices...but based on this fact, a rough DIY definitely does not mean less work with the same performance.

Therefore, it’s also important not to say that all these commercial devices may be counterfeit in some way (so please don’t get me wrong, but later in this project publication, I will tell a short story about An interesting thing that may be laughed at), it will make wrong promises when providing it, and make customers feel scared, but in the possibility of equipped with sound equipment, DIY projects can bring many benefits, motivation and First-hand knowledge, and save a lot of money in this way.

For decades, this has been known on Electronics-DIY, and here are some additions to this project. In fact, coupled with some kind of real innovation, stand up here to verify!

Focusing on the main functions of Overdrive-Effect, the circuit provided by this project provides some other functions in the form of a universal combination, capable of making good sound-producing equipment according to the characteristics of germanium, and can easily switch to the possibly very unique Silicon-on the other hand, equipment.

Maybe, if you ask about this scene every time and provide conclusive evidence, what you are saying now is that in one case, it is impossible to obtain really good germanium sound and excellent silicon sound, but just follow it here. What comes out of this is innovation, so the buttons are described in detail later in this publication!

As the second and major blow to this structure, the project uses OTA-IC as the core function of the generated sound effects. This is also a challenge to all commonly used Electronic-DIY`ers, among which these "operating transconductance amplifiers" are When many people in the electronics field need to be universal, there are still some difficult things, and there are few devices that they like very much. Therefore, the purpose is sometimes strange and sometimes incomprehensible, but I have to say that this may also come, because there is no useful OTA at all!

Since the early 1970s, the semiconductor industry has been developing rough operational amplifiers, but until today, thousands of operational amplifiers are still being developed, but in terms of quantity, all OTAs developed in history can be counted on with your fingers. Therefore, for decades, only a few useful parts can explain!

Figure 2: Simplified OTA diagram written by Eugene Zumchak, with internal IC functions

(As a normal knowledge of this situation, it should be realized that there is no industrial IC-OTA on the market, and it can provide a current of more than 2 mA at the output end!

I can’t tell the reason, but it’s a fact, and I can’t say it anymore, but if one wants to get a higher current value from the OTA than the above value, then all this can only guide a possible discrete solution (if needed Or need somewhere).

Perhaps because of these facts, what you are saying now is that this project may be just another helpless attempt to regain the deliciousness of old gum, but this is definitely not a fact, because it really comes as a new thing The unknown, or better yet, like this, the optimized and unknown possibilities, the special exhaustion of some semiconductor characteristics.

Here, you will also get the fact that the effect unit is highly dependent on temperature, which means that at around room temperature or above room temperature, this may just be a working unit that meets the requirements. If it doesn’t sound very good, Then play "Too Cold". Therefore, assuming that within a few hours in spring or autumn, the leakage of these parts can easily double in this fact, and then the entire winter may not work at all under the expected sound!

These are all physical properties of germanium and can be measured. I will add some data to these sentences later in this publication, but please forgive me. Now I clicked them because it means a lot of work. But I Will be updated.

Coupled with the ability to control the current on the OTA (actually only on this device), these facts are really surprising!

Figure 3: A discrete implementation of OTA-Overdrive-Cell, in which all used semiconductors are circled (for a more detailed description, please refer to this article)

By the way, that is to say, I have always wanted to know that I didn’t have this idea before. According to the current working principle, I need to use a small amount of electronic parts and OTA to complete the whole work. And here, I have always been interested in music electronics especially Analog synthesizer circuits are of particular interest.

Taking analog synthesizer (as a musical instrument) as the theme, there are OTA components everywhere in the synthesizer. Among them, voltage control circuits (such as VCO and VCF) require OTA, and circuit changes are often mentioned, using the cascade of "OTA units" Chain to achieve some audio functions, such as Filter-IC and so on.

Then there is the question about this idea, why not also perform the overload or distortion effect function on this OTA unit at the same time? So could this be useful?

(In Figure 3, you can see the simplified main OTA arrangement of Overdrive-Project, which includes four basic current mirrors-CM-equipped with some transistors, a differential input amplifier-dito, a very important clipping diode, And JFET output buffer.)

For startups with this idea, I can't believe that one or another famous Guitar-Stompboxes manufacturer (such as Electro Harmonix, Ibanez, Boss, etc.) does not exist. As a standard Overdrive-Effect, and implemented into the suitcase amplifier.

Therefore, when I started using this technology a few years ago, on such a distortion device with an OTA unit, I wanted to search on the Internet, and I found a lot of overload, distortion and blur boxes, and a lot of good people and www. adresses, the whole theme has a tip, and there are great life scenes around, but there is nothing new in new ideas, and it has been a well-known repetition for many years-every time I use an IC as an operational amplifier! (!! I got some good information from Don Tillman, about there should be some Gibson-Amp, and CA3094-OTA for the distortion mechanism, but as far as I know, these are also related to the Darlington-diode buffer , Which in turn means the use of effects. Although all possible advantages are not mentioned here, I have not found any of these Gibson schematics on the Internet until today. I am very happy to get some of them-if you know them , Please give me some donations!)

In addition, there are many practices on distortion circuits on the Internet, all of which have in common are the use of operational amplifiers. Almost at any time, clipping devices are configured as part of the signal correction and feedback loop, and extend from the output to the negative of the IC. Input, usually need compensation capacitor.

But I couldn't find any such configuration, so I used OTA directly. Then I googled "OTA, blur and distortion", but there was nothing...

I want to know a little bit, and then think of the fact that OTA may be the wrong thing, it may be that the available current is insufficient, OTA can only achieve a current of 2 mA at most, and an operational amplifier can provide 20-50 mA or more. Existing circuits, they get less, so this may not be a problem. To this day, I still don't have any reasonable answer to tell you!

This led all the initial ideas to the process of some tests using the rare metal tank CA3080A equipment. Then, I tried some experiments with higher drive currents on the clipping components. Here I also tried the hand-made and discrete implementations of SIL6-OTA, as well as a separate and very peculiar version, using SOT-23 and 1 respectively. : 1 Zetex-Lat-Sat transistor. Similar to the configuration of the circuit shown in Figure 3.

        Title item picture

Figure 2: The first OTA overload version, implementing Quad-OP, paired AA118 diodes and discrete SIL-06 OTA module

Then, about two years ago, the core functions were tested with several optimized units, and the parts required by the manufacturer were also provided with good usability, and then the main functional blocks divided into almost three parts were used to achieve the final The schematic diagram, the middle is in general, the said OTA-Cell is sitting, which will be described in detail below in this publication.

During this period, CA3080 and some other OTAs have been completely outdated, or are only very expensive in auction bids, and direct followers of DIL08-Packages CA3080-E, few NTE996. All these facts are put together-it is unacceptable and must be solved with something useful, and in the end don't spend too much money!

Therefore, the schematic has been changed again, and until today, the whole thing has to be implemented using National Semiconductor's LM13700 (the current name is manufactured by Texas Instruments), or as an alternative, using NJM13600 from Japan's JRC OTA is almost the same , And very useful, sometimes it gets better.

Although there are some voices on the Internet telling us, all these amplifiers can not provide the same audio performance as RCA or later from Harris to later Intersil's old CA3080A-Originals.

Therefore, it is difficult to say whether it has been tested or not, but the first obvious difference is the CA3080 chip, which is realized by an enhanced Darlington circuit, which is a direct component of the current source. They were not manufactured until 1999. Since the beginning of 1967, some old machines have adopted the very precise Chip-Process, which was previously carried out by RCA and was developed in the late 70s (only five minutes!) National-Chips. Using (only...) standard Wilson current mirrors. These ICs were also told that they were only designed to entertain and train certain students to create some chips in a certain possible competition, and were almost exclusively used to test new design software for consumer electronics at the wafer level.

See Mr. Don Sauer's very interesting "LM13600 / LM13700-Story" in his very popular Internet publication at:

http://www.idea2ic.com/LM13700.html

(Through this link, you can find a lot of information about IC development in the example of LM13600/700, but in this case there will always be some interesting consequences, and almost only low-level products are available, I tend to plan this The second version of the project and use another alternative solution, maybe not using those chips!)

The facts mentioned here are leading people to assume that the IC product is being developed quickly and hastily. Based on these facts and the above situation, people also know that some expensive semiconductor materials (pure silicon) are saved in the manufacturing process. Therefore, the overall transparency of sound performance may be slightly insufficient for ICs, mostly in a rapid transition state, with higher The current level may be in a pulsed state, but it is still unknown in the end, and then it is fully tested in various ways.

Therefore, judging from the playground of some professors, these ICs seem to be a kind of real CAD design, all interests are focused on science... And considering this and the appearance between the lines, I personally prefer the project unit It is implemented on JRC's NJM13600 (available from www.profusionplc.com at a reasonable price, the price is less than 1 euro!).

On the other hand, the real advantage of LM13700/NJM13600 is that they are dual versions and are designed for stereo use, so they could easily enhance the overload function and provide some necessary functions, which will be introduced later. In this publication.

Perhaps at first glance at the entire device, things seem difficult, complicated and the circuit is too large, especially for beginners, but after some practice and participation, one can easily get used to all parts of the device. "Step by step" work. Therefore, one of the goals of the project is to provide a practical tool for DIY-Guitar-User, which can be fixed in a few hours and can also handle the impressive "on-stage" used equipment . All of this is carried out to the product in a continuous manner, and it is possible to gradually learn about the previously used technology and all its background knowledge in a step-by-step manner (personal and required manner). End rough things by hearing all these things.

The parts used are almost standard electronic products, which still exist in the rapidly changing semiconductor market. Here, the continuous manufacturing process and the good availability of useful germanium devices are preparing such units as realizable, truly Another reason for the enhanced DIY-this project has enough room for expansion, and can also be used for self-made ideas and future experiments that users may conduct. Perhaps you can also find some new sounds in effects by modifying the schematic diagram!

I'm here to introduce you to a ready-made project, but it still describes a smart unit, and in the background I also keep a lot of ideas for enhancement, and I will describe some of them later (subject to change). This also means the following fact: everyone can see that all OTA-ICs seem to be obsolete in the next few years, and what will happen to the known production line of LM13700N at present.

Therefore, if they want to cancel the DIL16-Packages devices on these OTAs now, it will be a matter of time when they can use SO16´ers, because the industry only accounts for one million dollars in the economy and each cycle of the economy. A production line of commercial interest for the manufactured parts, so when these rules are cancelled product by product, we can continue to wait.

Today’s production, here only runs in the "as is" way, not in the "maybe" or "maybe" way. Therefore, if there are not enough orders, they will completely stop each production line, just like in the simulation synthesis The pain points of music devices are widely seen in companies, so no one can find a really good alternative, so by the way, they all tell us that digital music machines will always be the future, but in terms of this fact, I’m here to tell You, this is only part of the emergency exit, not (!!), so for the fast-growing DIY scene, it can help you tide over the difficulties, and learn more here. Users prefer DIL at any time Equipment, SMD parts without IC!

Therefore, I intend to provide some kind of actual project similar to a lifeguard for this case, and carry out follow-up projects on discrete OTA technology, but I need to keep this content temporarily, or keep it in the background for a longer time, etc. Wait, what will happen to the semiconductor market in the next few months/years.

It can be said that, unfortunately, perhaps all innovations will end in failure, and may not be realized all the way, and if LM741 is also brought out of the world market due to insufficient production, what will happen?

As an optional addition to the project, you can also follow a useful option, or better to say, the exact matching of semiconductors for this type of use, but it will not plunge the entire project into heavy laboratory activities because it can be completed The small amount of electronic parts added for this work is very accurate. These parts are prepared for the breadboard and can almost be performed by a good standard DVM.

The first important fact to start a project for DIY beginners here is that it is strictly forbidden to use any problematic SMD on this type of unit, and the entire assembly can be easily soldered together and can be on an optional socket Use DIL-IC.

Therefore, this unit has an advantage because it is also called "Vintage" with the actual TL072 and will continue (only possible) with the second version, which I will update in a few days to use in Cerdip-Packages The possible availability of some real "Vintage by 1982-TL074CJ-Black Top Opamps" (instead of using low noise 2SK30A-Y / -GR JFET buffers). This is coming soon!

Roughly speaking, the parts described here and used in the project will definitely be outdated. As mentioned above, it is very sad to see in the past few years (since 2005) that the popular CA3080 and especially the CA3280-OTA , And other high-priority synthesizer integrated circuits, and where the entire electronic music community is really hit by the semiconductor industry.

Due to the impact of these rules on the semiconductor market, there will be a second release version of this unit in the future (!! rough, only if there is enough feedback on the first one) to fully prepare for SMD. Before that, I There will be a full update, but here is the first setting, starting with a valuable and small budget unit available, as you can see here. Another reason for implementing this super-speed drive unit as an SMD version is that in the production process with through-holes, the PCB-Space on the double-sided printing plate is almost cheap. This is an attractive factor, so the only The single-sided version has a certain peculiarity, and even better, let us rarely say before that. Due to the mass production of PCBs today, this is a difficult reality, but very realistic!

1.) In the known standard size of 100 x 160 mm, cut twice from a purchased low-cost single-sided European card to get three cutable units (for all three variants, the size is 52 x 100 mm). This means that the project is well-prepared for the family concept and the kitchen production (and possible work sharing) of the entire guitar group. If you have no choice, each member will almost have a unique unit. The germanium clipping diode is preferred because it means that the rough tone of each unit will be different.

The smaller version of the device has only some parts and can be easily interrupted and tested on Expo-Strip-PCB (Vero-Board, breadboard) to try out all the parts, or just for tutorials. On the lowest version, you need 1 OTA (maybe CA3080, LM3080, NTE996), 2 diodes and an N-channel JFET.

2.) Variable and programmable input preamplifier, with good Lin-CMOS-OPAMP-Texas Instruments (TI) programmable TLC271, universal adaptive possibility for various pickups or other signal sources, but It can also be easily interchanged. It is recommended to use high-performance and high-speed Excalibur-OPAMP, TLE2037 (= Burr-Brown OPA627 equivalent, TLE2037C/SO-08 about €3,00 in element14/Farnell) in the input part by using DIL08-SMD-Adaptors . My non-commercial and only private component store with TLE2037A equipment can send a request via e-mail to support highly motivated readers of this publication!

3.) The entire signal chain can achieve low power consumption, with three JFET buffers, suitable for 9-volt batteries, but also suitable for 12-volt or 15-volt power supplies, and may be planned to be used as an internal synthesizer-effects module rack version . For 2SK30A-GR JFET, I can also give you some tips, you can get them here-there are several (German) distributors still offering them.

4.) There are four interactive main control potentiometers, which can easily switch the effect between silicon or germanium characteristics. The entire circuit environment provides enough possibilities to adjust all experimental changes or dynamic characteristics required in the future. This is also important and necessary, because different germanium diodes may be very different.

5.) The first accumulative overspeed capability when the input stage is amplified = the possible limit of the preamplifier on the enhancement (the triangle wave that the OTA will enter is limited to a sine wave!). If the user knows how to set up and change functions, he can easily modify all parts of the circuit as needed for special purposes. This possible mode can only be switched to the schematic with other unimplemented and not shown additional switches! Therefore, the resistance R10 must be reduced to another value of 1 kOhms -10 kOhms, and then the diode needs to be disabled and replaced with a resistor of, for example, 2 k Ohms.

Figure 4: Sharp/edge clipping caused by directly overloading the OTA input

6.) An additional and simple "absolute value converter", therefore a boostable Output-VCA, used for additional dynamic level control, depending on the intensity of the user's Guitar-Strike. It is also planned to change this part to ABV's operational amplifier solution to improve future enhancements in the implementation on SMD-PCB-Layout. This may also be the possibility of implementing enhanced Compressor / Noise-Gate Stage on the controls of the RMS converter. This means great possibilities for enhancement.

7.) Really unique and simple control from symmetrical to asymmetrical clipping function, fully selectable soft/hard characteristics of the effect, and volume level correction by using stereo dual potentiometers, where the user does not have to always change the characteristics The level of the external Poweramp can be re-controlled.

Figure 5: Symmetrical soft clamp when the guitar signal is overloaded

This is a very useful and very basic control, and the use of the pedal can also be enhanced by changing and optimizing one of the foot pedals as a foot control element.

Figure 6: Asymmetric hard clamp when the guitar signal is overloaded

8.) Through the "high leakage current germanium and silicon components" and additional selection and matching diodes, the real effect is obtained to obtain a truly real and musically smooth semiconductor overload sound, so there is no unexplainable effect never understood Magic in the black box background. Therefore, the user knows what he can really get from things and what he can get from things.

Let me say it again here: Proactive device users can request support via email from a non-commercial and only private component store (with matching germanium and silicon devices)! The instructions for selecting these components are as follows.

9.) There are really implemented "old design" on almost all components, including TO-92-JFET, DIL package and PCB layout, with round wires and software-generated shield wiring (copper-dumping).

10.) All parts are ready for future enhancements, and will always develop projects for users (not only products), and learn by listening and doing, which ultimately means overall fun, and for electronic beginners If there is no educational pressure, let me say that the first thing you need to do before is to be interested...

Right here, you can start the stage of soldering these things together, so please take a look at the main circuit of the device, and then take a look at the layout plan and let some suppliers provide parts.

If you want to use the recommended PCB, you don't need to think about it, but if you decide to build your own structure on Vero-Board, don't shield the OTA-Section too much, as this may greatly attenuate the sound to a large extent. The frequency range depends on the parasitic capacitance!

If you wish to additionally shield the object and have the advantage of blocking RF, you can apply shielding until the resistor named R10/R13 keeps the input of the OTA-IC almost unshielded. It is important to tell me that all PCB versions that I release without using SMD will have the small drawback of being more sensitive to RF induction, because its PCB wires are larger and longer (act like an antenna). If you are confused about this, the first solution to this problem is to set the value of the OTA's input divider resistor down, from 220 ohms to 150 ohms, and then set the amplification factor of IC 4. , Respectively increase the value of R6 (for example, from 22k to 39k, or from 51k to 82k)!

I hope this is not necessary anyway, but LM13700 IC may be different, and NJM13600 may also be different.

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