The aim of this stage is just to buffer the signal and remove the DC level. Gain reduction - Prior to reaching the opamp the signal travels through a transistor boosting stage where the signal level is increased dramatically, the gain in this stage is so high in fact that it drives the signal into soft clipping before it even reaches the distortion part of the circuit! This equalization enhance the bass and treble of the signal and is used in hard rock, other pedals like the Tube Screamer have a completely different approach boosting the mids creating a mid-hump. The source DS-1 pedal is quite rough in distortion, with the mod reducing gain but gaining smoothness, control and presence of your guitar tone. This distortion stage is followed by a passive tone filter and level control. These are the key elements: In consequence, by replacing R9 for a 1K resistor, the signal gets boosted just 7 times (17dB), so any typical guitar input signal of 100mVpp after the transistor booster stage has a level of 100mVpp x 7 = 0.7Vpp a low level that will not clip the op-amp stage. Replacing only one of the clipping diodes (D5 for instance) by a red LED yields more headroom and at the same time serves my second purpose of having asymmetrical clipping. 6.1 Voltage Gain Calculation. The output buffer has exactly the same circuit as the input buffer, its task is to keep a low output impedance for better signal integrity in the guitar-pedals-amp chain. Ill update the article with your changes. One of the things [], [] I have to confess that it has only be used a few times, just because lately I am using my modified DS-1, BOSS OD-3 or Tim Pierce Overdrive. b. Boss DS-1 Mods by PremerGuitar.Build your Own DS-1 Distortion.Marshall JCM & Octave Fuzz Mods by pedalheaven.Boss DS-1 A Detailed Take by GoodSpeed64.OpAmp Filter Examplesby University Las Vegas Nevada. El resalte se produce a los 800Hz, que para m es el mejor punto para conseguir un tono agradable y capaz de ser odo en una mezcla en el contexto de una banda. The result was so similar that you describe in your mod. (LogOut/ Vf es lo que provoca el clipping, y cuanto ms alto es Vf, ms alta puede ser la seal antes de que empiece a limitar. It is versatile; almost clean at lower gain setting with a serious edge at high gain (slight hiss is noticeable at higher gain settings). The original Boss DS-1 circuithas a JFET Bypass Switch Circuit to enable/disable the effect using a simple cheap momentary push button. It is versatile; almost clean at lower gain setting with a serious edge at high gain (slight hiss is noticeable at higher gain settings). Tone / Level Stage. Si sois buenos guitarristas, grabad una demo y subidla a youtube. Coloca un compresor delante y un ecualizador despus que resalte los 100Hz y conseguirs el verdadero sonido del rock and roll. The shopping list opposite details the electronic components you will need to complete this modification. The cut-off points of both filters are calculated so that their interweaving effect create a frequency scoop/notch. Me gustara saber si la gente disfruta (o no) de mis mods. This mod should not affect the function of bypass/drive, just tone and gain. You will also want to leave C5 unchanged in this case.R13 dictates both the gain increase of the opamp and the frequency cutoff at maximum drive settings. 6.2 Op-Amp Gain Frequency Response. Marshall JCM & Octave Fuzz Mods by pedalheaven. 4.2 Input Stage Frequency Response.5. This model is not very loud with a transparent drive. C1,C3 47nC2,C8,C9 0.47uC4 250pC5 68nC7 100pC10 0.01uC11 0.022uC12 0.1uC13 0.047uC14 1uC15 47uFC23 100uFD1 1N4004D4,D5,D8 D1N4148Q1,Q2,Q3 2SC2240R1,R22 1KR2,R7 470KR3,R8,R18,R21,R24,R25 10KR4,R5,R10,R11,R23 100KR9 22R13 4.7KR14,R15 2.2KR16,R17 6.8KR39 47KR19,R20 1MU1 NJM3404A ( or equivalent M5223AL, BA728N)VR1,VR2 100KBVR3 20KBJ1,J2 6.35mm Jacks. This is a non-linear circuit, the best way to analyze the behavior is in the time-domain, as is shown in the figure in 6.1. section. Para reducir la distorsin, he hecho estos cambios: Para el resalte de medios, cambi varios componentes de la seccin de tono. The resistor divider (R24, R25) generates +4.5 volts to be used as a virtual ground (bias voltage). Simulando el circuito en LTSpice, encontr el punto en el que se resaltan los medios de la seal sin perder la capacidad de controlar el tono (aunque esta capacidad se ve algo reducida respecto al DS-1 original). R2 is just a moderate high-value resistor that biases the base of the transistor to 4.5V. The first half of the NJM2904L dual op-amp is a simple buffer, it won't add (or remove) anything to the guitar signal. The cap C7 will also reduce harmonics at very high frequencies, softening a bit the distortion and reducing oscillation problems. For reducing distortion, I have made these two changes: For the mid boost thing, I changed several components of the tone stack. In 1994 the op-amp was replaced by the Rohm BA728N. Also since the bass frequencies dont get amplified quite as much at this initial stage it helps to keep the distortion tighter across its range. This stage applies some frequency filtering and signal boosting before the op-amp stage. var addy5230ce14d5603ba6bd88484b4b0c40a7 = 'info' + '@'; Normalmente los pedales basados en hard clipping, mucha distorsin y una curva de frecuencias mid-scooped (frecuencias medias rebajadas) son denominados distorsin, y aquellos basados en soft clipping y con resalte de medios son llamados overdrive. It kind of swells into either mode when I switch. Vf is what causes the clipping, and the higher Vf is, the higher the signal can be before it starts to clip. When an op-amp input is driven beyond the rails, bad things happen. All the potentiometers, jacks and battery are wired and hand soldered which is quite labor intensive. No me disgustaba tal cual, pero ese tipo de distorsin no es para m, francamente.El BOSS DS-1 est basado en el clsico hard clipping simtrico, dos diodos a la salida de un operacional, y la seccin de tono tiende a dar una respuesta mid scooped, as que debe ser considerado como un pedal de distorsin. Hard clipping seems to have usually a more dynamic overall response to the guitar touch than soft clipping, although it depends on the circuit design. The advantage of using an LED as a clipping diode (other than its unique forward voltage) is that the LED will illuminate as the signal clips. Es naranja y se llama distortion, as que en este caso es fcil de clasificar. Engineer working for a big company and amateur musician. This first model had some inconveniences like momentary LED and the need for an external power supply. Greatings from Argentina. Con un valor de 22 Ohms, la salida es tan alta que la seal a la salida del operacional es limitada por los diodos prcticamente siempre. Como resumen, stos son los componentes reemplazados: Para C12, 82nF no es un valor muy comn, pero puedes poner 47nF y 33nF en paralelo para tener 80nF, suficiente dada la tolerances habitual de los condensadores. At the beginning of the stage, there is an RC network (C5-R10) that creates a high pass filter with a cut frequency of 23Hz (fc=1/2RC). I liked as it was, but that kind of distortion is not for me, frankly. The Boss DS-1 is a distortion guitar pedal released in 1978 by Boss. Change), You are commenting using your Facebook account. Its really all about what you want the maximum setting on the drive control to do. 470K is a high input impedance to avoid loading guitar pickups and tone sucking, although the rule of thumb is to interface the guitar to an input impedance that is 1 M minimum. By lessening the effect of R7 and C4, the low-freq cutoff from C3 is moved down and the high-freq cutoff from C4 is moved up. Thanks for reading, all feedback is appreciated. The Operational Amplifier block is the heart of the circuit, it is build using a variable non invertingop-ampamplifier with two diodes to do the clip/distortion action and some passive RC filters ( passband = low pass + high pass) to set the clipping and the frequency at which it occurs. The board has plenty of space to put the two capacitors in that position. 1994 Second Release using the Rohm BA728N op-amp (Made in Japan). Al simular su circuito conseguimos una curva muy similar pero ms suave, menos pronunciada en los 800Hz, y tambin aparentemente ms atenuada en las altas frecuencias: Probad esto si la modificacin suena muy nasal, o si obtenis algo de fritanga en el amplificador. I wanted to experiment those concepts with a BOSS DS-1 pedal I purchased broken and then fixed. Use a capacitor tester if possible to get a close value. The Boss DS-1 has been around since 1978 and remains to this day one of the top selling guitar pedals ever. It was the first distortion pedal made by Boss with a distinctive hard-clipping sound perfect for high gain rock and metal still keeping the character of the original guitar. In the image above you can see the difference between using an R9 of 22 (default) or using the 1K resistor. Simulating your changes gives a different frequency response curve, with a bump at 800Hz but less prominent, smoother. Con la ganancia al mximo, revela su verdadero espritu de distorsin. It controls it by allowing highs through the feedback loop. This transistor overdrives the signal from the early stages of the pedal and will condition the behavior of the whole effect. )This is a place to experiment and see what you like best. This is not an intentional filter, just a cap is needed to couple the previous transistor gain stage and a moderate-high value resistor is needed to bias the + pin of the op-amp at virtual ground (+4.5V). For mass production true bypass switches are difficult to mount and not cheap, some big pedal circuit manufacturers (like Boss) prefer to use complex but cheap JFET bypass circuits that also can carry other benefits like keeping always the input/output buffer in the signal chain (if desired). You need JavaScript enabled to view it. at the notch the loss is about -20db (500Hz) but there is no problem with this because in the previous stage after the diode clipping the signal has a 1.4Vpp amplitude, with -12dB loss the resulting signal will be 350mVpp (1.4Vpp/4times) which is fine for an output level and won't distort the input stage of the next pedal on the chain or the guitar amplifier. Output signal after the Transistor Booster Stage in red color 9Vpp (clipped). The R1 input series will protect the base of the transistor from surge currents (electrostatic discharges from the guitar jack tip). When either D4 or D5 are conducting, the impedance at R14 - C10 junction is greatly reduced. Thanks for reading, all feedback is appreciated This email address is being protected from spambots. The purpose of this filter is just to remove the DC levels from the final output signal. Q2's collector is biased around +5.8V, and when going into saturation, without D8, U1 pin 3 would be driven to -1.3V. The D4 & D5 diodes load the R14 - C10 network and drastically alter the cutoff freq. The second half of the NJM2904L is a non-inverting amplifier that will boost the signal up to 22.3 times (26.5 dBs) following the formula: Gvop-amp max = 1 + ( VR1)/( R13) = 1 +(100K/4.7K) = 22.3 (26.5dB), Gvop-amp min = 1 + ( 0 )/( R13 ) = 1+(0K/4.7K) = 1 (0dB). Mejora mucho el sonido final. Perhaps even add a switch to toggle between silicon diodes and LEDs, or between symmetric to asymmetric. Pero algunos de los overdrives ms famosos, conocidos por ser transparentes, limpios o dinmicos estn basados en hard clipping (cortar la seal en los extremos mediante diodos puestos a tierra a la salida de un operacional). Si sois ricos, enviadme un Klon Centaur para compararlo con mi DS-1 modificado. Bass notes are less clipped, so the distortion is frequency selective (similar to what happens in the Tube Screamer, but in that case, the freq limit is 720 instead of 72Hz). I have prefered to keep it as simple as posible, but the change in tone and behavior is drastical. Boss DS-1 Distortion Sound Signature.10. It is important to mention that by the time this diode is conducting, the opamp is already clipping. ste es, por cierto, uno de los cambios del famoso Keeley Ultra Mod. The circuit presented here is adapted to be used with a 3PDT switch, simplifying the circuit for DIY. Thanks for the contribution and for sharing it! At the beginning of the stage, there is an RC network (C. high-value resistor that biases the input of the op-amp to 4.5V. when the tone control is set to the middle position. If you want to read more about the switching circuit operation, check the TubeScreamer pedal explanation, this part of the circuit is exactly the same: TubeScreamer JFET Switch Operation. No se de qu ao es tu pedal, pero si es posterior a 2005 creo, lleva la R40 a la salida del operacional que lo convierte en un Class-A. The 3PDT drives the guitar signal either through the effect circuitry, or straight input-to-output, the guitar signal does not even touch the input of the effect. There is an obvious RC network (R14 & C10) with C10 in parallel with D4 and D5 clipping devices. (LogOut/ BOSS DS-1 is based on classical symmetrical hard clipping, two diodes at the output of an operational, and the tone stack tends to mid scoop the response curve, so it should be considered a distortion pedal. This modification works incredibly well when used with Single Coil and P90 type pickups. Sorry for my english. Los diodos LED tienen una Vf (corriente directa) ms alta que los diodos bipolares comunes. The diode D1 is protection against reverse polarity connections, in case the player connects a wrong power adapter. The idea is to raise the signal levels so the next stage can work with acceptable levels although as we can see later, the signal is maybe too boosted after this stage. Frequencies at 7.2Hz are attenuated -3dB with a roll-off or 6dB/oct. Es pasiva, y tiende a atenuar los medios. At max distortion, harmonics over 72Hz get the full gain of the distortion stage, and everything below it gets progressively less gain and distortion. var addy_text8e175d3400a34f83f6a4e52838e1faa7 = 'info' + '@' + 'electrosmash' + '.' + 'com';document.getElementById('cloak8e175d3400a34f83f6a4e52838e1faa7').innerHTML += ''+addy_text8e175d3400a34f83f6a4e52838e1faa7+'<\/a>'; e-mail us at This email address is being protected from spambots. Read the last page of the M5223A datasheet for more information. Also, C5 & R10 reduce harmonics below 23Hz at the limit of the audio spectrum that will help either way to reduce oscillation. The. Yo en alguno he cambiado el operacional por un TLC2272 adaptando patillaje, y quitando esa resistencia. var path = 'hr' + 'ef' + '='; but thats where I am at. The design idea is simple: The Input and Output Buffers will isolate the circuit, keeping the signal path clean and tone-sucking free. El soft clipping limita la seal ms gradualmente aportando ese sonido ms suave que generalmente asociamos con la distorsin de vlvulas. Think of Klon Centaur, for example (mid boosted, by the way). The last change was in 2006 when the New Japan Radio NJM2904L opamp was introduced. LED diodes have a Vf higher than common bipolar diodes. Soft clipping limits the signal more gradually, giving that soft, characteristic valve-like distortion sound. A stereo guitar input jack could be used as an on-off switch, connecting the battery (-) pin to ground when the guitar jack is plugged. In an Emitter Follower the input impedance can be calculated as, If you want a further explanation of how to make all the numeric calculations, check the, The frequency response of this input buffer is dominated by the high pass filter created by C, This stage applies some frequency filtering and signal boosting before the op-amp stage. Dallas Rangemaster Treble Booster Analysis, Time Manipulator - Arduino Delay/Echo/Reverb, Tube Screamer Input Impedance Calculation. var addy8e175d3400a34f83f6a4e52838e1faa7 = 'info' + '@'; The Boss DS-1 uses a passive Big Muff Pi style tone control, which scoops the mids and attenuates the lows or highs, depending on which way you turn the knob. The Transistor Boosting Stage has a huge amount of gain, it amplifies the incoming signal 56 times (35dB). Maybe I have too many []. Espero que disfrutis esta modificacin, por favor hacedme llegar cualquier mejora o error que podis encontrar. This is the reason why a lot of mods like the'Vintage Ripper', the 'Fat Mod for DS-1' or the 'Huevos Grandes' increase the size of R9 from 22 to 1K, this makes the voltage gain of the Transistor Booster Stage to decrease from the default 35dB(56 times) to a more moderate value of 17dB (7 times). The idea is to raise the signal levels so the next stage can work with acceptable levels although as we can see later, the signal is maybe, The transistor stage is a Common Emitter amplifier, the approx. The design idea is simple: The Input and Output Buffers will isolate the circuit, keeping the signal path clean and tone-sucking free. transistor booster will pre-amplify the signal and all the distortion is produced using a variable op-amp gain circuit with diodes shorting the output to ground, producing hard clipping. 1- Boss DS-1 Circuit Versions.2. This email address is being protected from spambots. If this flat frequency response is undesirable then reducing the modification values of C11 and R17 (as well as experimenting with C12 and R16 which make up the low pass filter) will shift the scoop frequency at the mid position of the tone control. The frequency response of the Tone control looks similar to the, There is an overall -12dB (4 times) loss and. I think this is why people say that increasing R9 "flattens the frequency response". With a value of 22 Ohms, the output is so high that the signal at the output of the operational is almost always clipped. Mod done, very happy with the result. The previous TA7136AP integrated circuit was at the end of its stock life, so the whole circuit design was modified (re-labeled as DS1-A) to accommodate a standard easy to find and replace dual op-amp.This model is not very loud with a transparent drive. On the high frequencies by the low-pass filter formed by R14 and C10 will attenuate harmonics over 7.2Khz, this is better explained in the section below. As a summary, these are the replacements: For C12, 82nF is not a very common value, but you can put 47nF and 33nF in parallel to get 80nF, enough given the usual tolerances of capacitors. The transistor stage is a Common Emitter amplifier, the approx. Hard clipping, theoretically limits drastically the signal when it reaches a certain level, so it creates those high harmonics that give it its character. El hard clipping parece tener una respuesta general ms dinmica al toque de la guitarra que el soft clipping, aunque depende mucho del diseo del circuito. Maybe something was previously wrong or you have touched some other component inadvertedly. Output Buffer.9. The emitter feedback reduces the distortion. DS-1 tone stack is based on the Big Muff tone stack. The Boss DS-1 together with the TubeScreamer and the ProCo Rat cover almost all the spectrum of tastes for vintage classic rock/hard rock guitar distortion. The clipping stage defines the distortion signature sound, it is built using 2 back to back diodes that shunt the signal to AC ground (4.5V), this kind of clipping technique gives a hard-clipping sound also used in the MXR Micro-amp or the RAT opposed to the , With the 26.5 dB of gain, the audio signal will be bigger than the V, The image above shows the waveform after the clipping diodes, it exhibits a clear squared shape limited between +0.7V and -0.7V which is the V. Capacitor C7 (100pF) reduces the high harsh harmonics at the very top of the audio spectrum. Es una simplificacin, ya que la curva de respuesta del pedal depende del conjunto del circuito, pero os aseguro que el resultado es bastante aceptable. It is orange and is called Distortion, so in this case it was easy. I do the mod whit some changes because I dont found somes components. By simulating the circuit with LTSpice, I found the spot where the signal is mid boosted without loosing the ability to control the tone (although it is somewhat reduced compared to the original DS-1 design). 4.1 Input Impedance Calculation. Like the Input Stage, this unity gain buffer is implemented with a plain Emitter Follower with a 10K emitter resistor R21, biased from the 4.5V source with R19 in parallel with R20 (1M//1M=500K). A 3PDT switch. In total there are 5 capacitors, 3 resistors, 2 diodes, and 1 LED (make that 2 LEDs if you want to change the existing indicator LED like we did)Asides from these components you will also need a soldering iron, solder, and some tweezers or similar tool capable of prying the old components from the PCB. var prefix = 'ma' + 'il' + 'to'; Made in Japan, with a distinguishable silver screw. fcmax = 1/(2C8R13) = 1/(2*3.14*0.47u*4.7K) = 72Hz, fcmin = 1/(2C8(R13+VR1)) = 1/(2*3.14*0.47u*104.7K) = 3Hz. From now on, all the models are commonly called post '94. As you can se, only six components have been replaced. Para C11 y C12, cualquier tipo vale, pero los valores son muy importantes (comprobadlos si es posible). Extending this through the chassis provides us a visual indicator of how much clipping is going on. The first part of this stage are 2 consecutive high pass filters: The basic idea behind this filters is to remove the excess of bass before the (next) distortion stage, a guitar signal with too much bass harmonics could make the distortion slow, dumped or muddy. The 2SC2240 is a cheap high-gain transistor, a simple unity gain buffer does not have high requirements for the transistor. The components replaced in the tone stack are C11, C12, R15 and R16. The value of C5 has been increased as a result of this to couple the transistor stage to the opamp gain stage. Look also for some of the replaced components touching some other component. The minimum gain is 0dB and can go up to 26.5dB depending on the position of the distortion potentiometer, this amount of gain is not massive (the Tube Screamer has 41dB, the Proco Rat has 67dB) but the fact that the previous stage has a gain of 35dB makes that the resulting signal is completely clipped. PPD: JAVIER from Argentina made some changes to this mod, he used a 47nF for C12 and a 15K for R15, getting very similar results. 3. Somewhere between 2.2K and 4.7K would provide the best results. Cheap, easy to find and perfect for mods. By reducing the values of C11 and R17 we drastically shift the cut off for the tone controls high pass filter, creating a flatter response in the neutral setting. While this is generally a good idea as distorting low frequencies can make the distortion slow or muddy, we felt that dropping the cut off frequencies for these filters slightly (by increasing the values of C2 and C3) would add some extra body to the distortion, while not compromising its aggression. Reducing the value of feedback resistor R7 helps to tame this initial amplification, allowing the pedal to be more responsive at lower distortion settings and less like a fuzz with the drive maxed out. The capacitor C1 isolates the guitar from any pedal dangerous DC level and filters the inaudible low-frequency signals with a cut frequency of 7.2Hz (fc=1/2C. Therefore D8 has nothing to do with asymmetrical clipping or any kind of guitar signal modification. Increasing this resistor will reduce the maximum opamp gain while attenuating less gain for lower frequencies.