Inverse riaa schematic

Inverse riaa schematic. Block diagrams describe a system by vis The multiplicative inverse of a negative number must also be a negative number. They use various symbols to represent different components and conn It is easy to find the inverse of a matrix in MATLAB. 1dB to 0. Dec 14, 2022 · The Inverse RIAA network and buffer in the spice simulation are of special interest as they can be used with any RIAA preamp to test for compliance with RIAA equalization. The diagram contains a schematic drawing of every piece contained in the carburetor and labels it u. If any member has a collection of Transistor based RIAA schematics they can throw up. The values on a Bode plot (done with a PC based DSO) of the response were within 0. As a general rule, peach season begins early when the weathe A relay symbol is an image used to denote an electrically operated switch in a schematic diagram. May 11, 2016 · The schematic shows the parts used in the PEC for the RIAA equalization, so I replaced the RIAA-associated PEC parts with individual precision components, but it still sounded bass-heavy. A simple example from primary m When it comes to optimizing the performance and safety of your Kohler engine, proper wiring is of utmost importance. Riaa deviation stayed like before, straight line at the begining sound was little Jun 9, 2015 · It is still passive, it still sits between the two gain stages, but the values have been changed and it has shed one component. One of the primary advantages of using sc RV plumbing systems can be complex, and when issues arise, it can be challenging to pinpoint the root cause. Conversely, if the low-pass filter is tuned to a frequency lower than 2122Hz, we get a highs cut . (It's recommended for inverse RIAA that C27 and C28, 100 pF also be fitted to provide additional ultrasonic rolloff. Summary Jan 1, 2021 · Looking at available options for Inverse RIAA Filters, Jim Hagerman's iRIAA2 looks like it fits the bill. but instead new build started with CPH3910 on universal PCB , with Iskra and Wima polypropilenes . The 75 uSec pole is formed by C2 and R3, the first stage runs without negative feedback (except for the DC servo feeding the current source). One of the primary benefits of electrical schematics i When it comes to troubleshooting electrical systems, having a clear understanding of how the system works is crucial. It is important that the RIAA equalizer response is accurate across the audio band (20 Hz to 20 kHz) and also well behaved beyond that. The circuit here if used with quality components implements a filter very close to the ideal RIAA response. valves. 2 dBV from 20 Hz to past 30 kHz (yes I know the RIAA standard doesn't go that high, but I can test for that response). But the LTspice simulation and the perfboarded circuit both failed to show a proper Figure 4. Nonetheless, peaches can be ready as soon as May or as late as September. Circuit specifications. Whether you’re a seasoned RVer or a newbie, being able to interpre Creating circuit schematics is a crucial step in the process of designing electronic circuits. Unlike traditional networks, the iRIAA Filter includes a correctly placed upper 3. In the days before all the sophisticated equipment we now have, all that was required to test a preamp was a suitable square wave generator. The nice thing is that the Audio Precision then sources a 1V signal that is passively attenuated. Just in case somebody is every looking for a very simple RIAA transistor circuit. Below is the RIAA Calculator Excel spread sheet. It's a contributed design, and is as close to a true reverse RIAA EQ iRIAA2 Inverse Filter 3 Description The inverse RIAA Filter is an accurate reference for testing modern phonostages. I have covered the topic of split RIAA equalization before, but it cannot hurt to look for new approaches. Apr 24,2024. As a general rule, peach season begins early when the weathe A Briggs and Stratton carburetor diagram can be used to overhaul the carburetor. The results are nothing less than spectacular. John Kennedy. These vehicles provide a comfortable and convenient way to explore new places while enjoying the comforts of Schematics diagrams are an essential tool in the field of electrical engineering. The goal being to confirm that the complementary de-emphasis portion of the circuit results in overall flat frequency response. Schematic_Inverse-RIAA_2024-04-24. pdf. These vehicles provide all the comforts of home while allowing indi Electric bikes, or e-bikes, have gained immense popularity in recent years for their eco-friendly and efficient transportation capabilities. The reduced level of ultrasonic information at its output will sometimes result in lower perceived distortion Jul 14, 2023 · 1. If you wanted to build your own inverse RIAA equaliser, see Project 80. By definition, the product of a number and its multiplicative inverse is (positive) 1, which cannot Wiring schematics are crucial documents that provide a visual representation of electrical circuits and systems. An exponential function written as f(x) = 4^x is read as “four to the x power. When faced with a malfunctioning Whirlp RVs, or recreational vehicles, are a popular choice for those who love to travel and explore the great outdoors. The total dynamic range is actually greater than 40 dB as the high frequency rolloff between 20 Hz and 20 kHz with your RIAA amplifier, the response above ~50 kHz should gently drop off at 20 dB/decade as shown with the dashed green line in Fig. Figure 4. You get spikes out of the IRN (looks really weird on a scope) which after passing through the RIAA preamp, restores them back to a square wave. To compare to this. Mar 13, 2021 · An Accurate Inverse RIAA Network. The site includes variety of industrial schematics. The law of demand illustrates this inve Wiring schematics are crucial documents that provide a visual representation of electrical circuits and systems. Aug 27, 2022 · Just two non-inverting opamps with RIAA filter network sandwiched in between. 3 Passive RIAA(f) 1-step-solution type (A ub) Fig. RIAA equalization is a specification for the recording and playback of phonograph records, established by the Recording Industry Association of America (RIAA). 8 RIAA Networks 229 Fig. By being aware of these Kawasaki wiring schematics play a crucial role in the electrical systems of Kawasaki motorcycles and other vehicles. 7dB at 20kHz versus the ideal response, and LTspice simulation showed that as well. 20dB higher signal level at 20kHz than at 1kHz. According to Beer’s law, a larger amount of light being transmitted through the sample corresponds to a smal The integral of arctan is x times the inverse tangent of x, minus one-half of the natural logarithm of one plus x squared, plus the constant expressed as C. Input the matrix, then use MATLAB’s built-in inv() command to get the inverse. Presented here is a simple Inverse RIAA Network, or IRN, that allows testing to be quickly and effectively done. It is within 0,1dB of the curve. . If you need a 200 gallon capacitor and have a 200 1% on the high side, it's 202 gallons. If the circuit is driven from an inverse RIAA network, the overall response should be flat. For this repost, we decided to merge the two articles in one single page. Imagine looking at this in a mirror placed above the top of the graph; that, of course, is the inverse RIAA curve. 5 nF Feb 14, 2004 · inverse RIAA->RIAA , transfer f. The opposite of an inverse relationship is a direct relationship. This calculation applies to an RIAA impedance network that converts unequalized signal current into equalized output voltage. about all May 3, 2023 · For more details about this network see my article “The MC100 A High-Quality Moving Coil RIAA Preamplifier” (audioXpress, March 2014) Figure 9 shows the preamplifier’s accuracy with this inverse RIAA network connected at its input. 1% resistors and 1% capacitors), using the ideal values of the schematic diagram (see Resources). Output level is switchable between -40dB and -60dB Jul 3, 2021 · Once components have been committed to a prototype PCB however, testing is required. 63. Figure 4 shows the RIAA playback curve. 0. g. A counterexample, in geometry as in other areas of mathematics and logic, is an example that one uses to prove that a particular statement is false. Read on to find out how this circuit has a RIAA accuracy of less than +/- 0. Inverse riaa . It measured -0. 025 dB from 1 Hz to 100 kHz! This is the schematic for the passive RIAA filter. In this article, we have compiled the ultimate collection of resources When it comes to mathematical functions, understanding their domains is crucial for solving equations and analyzing their behavior. 3dB deviation from calculated, at all frequencies. To arrive at this answer, it is simply a matter of using the formula given for finding the derivative of the inverse tangent fun The basic examples of network topologies used in local area networks include bus, ring, star, tree and mesh topologies. The "Laplace"-thingie is the inverse RIAA input signal. Figure 5 shows the resulting frequency response of the circuit, which is also given in tabular form in Listing 2. It was much better with flat eq and even better if I added some bass. These visual representations of electrical circuits provide engineers, technicians, and hobbyists with a In the world of electronics, circuit schematic design plays a crucial role in the overall process of printed circuit board (PCB) layout and manufacturing. This article starts as a history lesson that merges into an explanation of why this RIAA equalization still matters today. Pay attention on the correction factor of 1/10, this should be a shift up to 20dB at 0Hz, so the correcting factor here is 10. Attachments. Once the circuit schemati Whirlpool appliances are known for their durability and performance. These schematics are essential for troubleshootin Schematic diagrams show detailed drawings and information of the individual parts that a system or machine consist of and how they interact. Any obvious hack / mods improvements to this design. The output is taken directly at the output of the phono preamps to eliminate any influence from succeeding stages. This circuit does the level conversion, impedance matching and inverse RIAA filtering. Apr 19, 2019 · I've been using the ARTA software package as well, and checked the inverse RIAA unit against the calculated RIAA values, at 15 frequencies, 20Hz to 20kHz, using an M-Audio Audiophile 2496 soundcard. One is called the recording curve (dotted blue line) and one is the playback curve. Provisions for input switching and recording are shown and can be adapted to meet your needs. Open MATLAB, and put the cursor in the console RVs are a popular choice for those seeking adventure on the open road. May 7, 2010 · Yes, 600 Ohm oscillators are common here too (despite the fact that 600 Ohm lines disappeared fifteen years ago), but you then have to worry about the response flatness of a Wien bridge oscillator, and unless the two components in the variable arm track perfectly, there will be 0. Oct 31, 2018 · Next, I measured the accuracy of the preamplifier’s RIAA curve. Finally it has more sense to me! It would be awesome if you could post some graphs, pictures, circuits etc. These articles were originally published in audioXpress, October 2003 and January 2010. Why was it changed? Apr 24, 2024 · Inverse RIAA Network Schematic. 5751 phono. Input impedance: > 10 kohm Output impedance 470 ohms Nominal input signal level: 500 mV Nominal output signal level: 2. 2n capacitor value on the schematic, not the two 3. Nov 13, 2019 · This approach to RIAA equalization results in a high-quality phono preamp featuring the high-transconductance 5842 tubes. The current produces a proportional voltage across the operating resistor R3. VI 500 mV 2. Jun 10, 2024 · The iRIAA Filter is a two-channel passive inverse RIAA response filter for use in testing phono preamplifiers. It's got the added benefit of bringing a higher input signal down to cartridge level. Indeed, those are precisely the modification I have done. That’s why these passive solutions are the ideal choice for high voltage gain stages like e. 25V. This LTSpice simulation of the Muffsy Phono Preamp uses LT1792 and LT1037 that are quite similar to the OPA2134/LM4562 combo. They provide a visual representation of a circuit or system, making it easier for engineers to und When it comes to designing a PCB board schematic, there are several common mistakes that can lead to costly errors and delays in the manufacturing process. A circuit schematic is a diagram that represents the connections and components of a In the world of industrial automation, electrical schematics play a crucial role in ensuring smooth and efficient operations. jpg. diy-audio-engineering. One such function that often raises questions ab In the world of electronics, circuit schematic design plays a crucial role in the overall process of printed circuit board (PCB) layout and manufacturing. A circuit schematic is a diagram that represents the connections and components of a When it comes to electronics, circuit schematic design plays a crucial role in ensuring the functionality and reliability of electronic devices. 384 views. 18us (50kHz) corner in its transfer function. : sound wasn't verified. There are some excellent published designs (I used one from AA), and building one up with 0. This motivated me to try the SL10 RIAA too. ” Its inverse logarithm function is wr If you’ve ever tried to understand the inner workings of your whirlpool appliance, you may have come across a whirlpool schematic. Nov 6, 2003 · I need to drive an amplifier circuit from a pre-emphasized voltage source. Block diagrams describe a system by vis An inverse relationship in economics is a relationship in which an increase in one variable corresponds with a decrease in another variable. Download(29) Download Gerbers. This circuit uses 6DJ8 tubes in a two stage RIAA phono preamplifier followed by a one stage line preamplifier with a volume control input. This is where schematics diagrams come into play. I used a inverse-RIAA network to fine tune the transfer function, trying a few capacitors of the same value, untill I got it right. Convert mph to kph by taking the mph and multip In most states, peak peach season is in July. Sep 1, 2024 · The inverse RIAA circuit is supposed to be pretty accurate. Once you have calculated your RIAA values, you are strongly encouraged to check your design out using a spice model – I use LTSpice, but any Spice simulator will work. of RIAA preamplifiers based on the inverting topology shown in Figure 2(b). Using mathematical nota The abbreviation “kph” means the number of kilometers traveled in an hour, whereas “mph” is the number of miles traveled in an hour. A 200 Hz square wave first passing through a high accuracy Inverse RIAA Network, and then feeding the RIAA 1 inputs. When breaking up the required inverse RIAA curve into two, we usually combine the first two time constants, 3180µs and 318µs, into one shelving network and the last time constant, 75µs into a single low-pass filter. I have an accurate inverse RIAA network, which was constructed with high-accuracy components (0. a reverse RIAA network and an Thus, the inverse RIAA equalization must impose a countervailing low-pass filter at 2122Hz. Dec 9, 2019 · While the exact year is fuzzy, we accept that as the year that the Recording Industry Association of America (RIAA) established the RIAA curve standardization for records and record players. Listing 1 is the input text file to my SPICE simulator. Mar 4, 2017 · Feeding your signal through an inverse RIAA equalizer, and then through a phono stage, will create a flat output at all frequencies. Aug 17, 2015 · If you want to test quickly phono schematics in LTSpice use inverse RIAA circuit (oh I see Rod recommend it too ). This circuit can accurately follow the standard RIAA response curve since the absolute value of its gain can be less than unity. It's already been stated that P06 has a small low frequency boost, and that can be seen in the following graph. Simplified schematic of the Neumann SE66 recording equaliser in the VG66 disc recording electronics system In the SE66, the inverse RIAA characteristic is accomplished by the interaction of capacitors C1 and C2 with the other circuit impedances and op-amp gain. (One notable Feb 14, 2004 · Hi av-trouvaille, Thanks for posting the schematic. Dec 8, 2008 · 6DJ8 Tube RIAA Phono and Line Preamplifier Schematic. Two or more physical quantities may have an inverse relationship or a direct relationship. goodluck ••• Jun 21, 2007 · now this is something! I tried to cut with that "inverse RIAA curve" and the sound was terrible. 5% or better tolerance components (I used 0. Electrical wiring schematics, also known as circuit diagrams or electrical diagrams, are visual re For any number, including fractions, the additive inverse of that number is what you add to it to equal zero. 8. Published:2009/7/6 5:49:00 Author:May | From:SeekIC. Dec 27, 2012 · The following link is a great source of info about RIAA designs. With a worst case 4mV offset on an SA5532 op-amp, this amounts to an output offset of about 2. These diagrams serve as a roadmap for technicians and enthusias Schematic circuit diagrams play a crucial role in the field of electronics. While experimenting with it, I found that if I used the LP equalization setting on the input switch instead of the RIAA one and adjusted the loudness control Jun 25, 2014 · 3. 2 – you can read a bit about why this should be the case here: Inverse RIAA Network Jan 27, 2014 · I built the Hagtech inverse RIAA network from the schematic on the website; I used the 6. This includes inverting and current input stages. Jul 6, 2009 · INVERSE_RIAA_RESPONSE_GENERATOR. connected to adjustable DC supply, several working points were checked. If this inverse RIAA equalizer is sufficiently accurate, it can be used to measure the accuracy of your phono stage. This is because ln(x) is the inverse function of e(x), which means that applying the function f(x) = e^x reverses the effect of the function f(x) = ln(x) In most states, peak peach season is in July. A house circuit diagram, also known a The integral of arctan is x times the inverse tangent of x, minus one-half of the natural logarithm of one plus x squared, plus the constant expressed as C. Some of them are pretty old but could be easily adapted and brought back to date using the modern component base. These two-wheeled wonders are powered b The value of e^ln(x) is x. Now this one is a real gem: Jun 22, 2012 · RIAA Preamp Build (Part 1) Well, someone asked me to design a low-noise stereo preamp for RIAA, (record phono input Equalization), so Challenge Accepted! I made a preliminary design effort using a Mu-Follower type layout for dead-quiet PSRR and low noise, and also chose a low-voltage Jun 29, 2012 · Back in the predigital day, we used a simple passive Inverse RIAA stage, which had the side effect of causing enough loss that we could test with a conventional oscillator (actually the oscillator half of a distortion analyzer) and with hand chosen parts in that stage and carefully calibrated measuring equipment honestly spec a properly Jun 16, 2021 · RIAA implementation is not difficult, but does require close-tolerance parts. Nov 28, 2015 · Inverting RIAA Network (Series-Parallel) Application . 9 KB · Views: 1,037 For those of you who want to simulate the accuracy of the calculated (and corrected) RIAA equalization network. 1dB from 20Hz to 10kHz. Why an inverse RIAA? Well, one can cut the turntable, tonearm, cartridge and other variables out of the equation, drop a standard line input to phono levels and as a result get more useful performance data. Jul 26, 2015 · THE RIAA CURVE . com RIAA Equalization 3 RIAA Equalization Table 1 shows the RIAA equalization response while Figure 1 displays the same graphically. Since last month we have a APx555B and there you can load an excel list. Lipshitz showed that designing an active RIAA correctly was not a trifling task, while Baxandall demonstrated that through correct simplifying assumptions and the use of the active/passive topology, very accurate RIAA was possible without recourse to long equations. 3. When it comes to understanding the electrical systems in our homes, one crucial aspect that often goes unnoticed is the house circuit diagram. It provides the inverse transfer function of the RIAA response and level shifting so that a line level signal is converted into exactly what a phonostage input expects. A good way to test the conformance of a RIAA is to drive the IRN with a square wave. If the low-pass filter is tuned to a frequency higher than 2122Hz, we get a highs boost. In theory, passing a signal though both in series should give a flat response. It simulated well in the LTSpice and sounded good too. Once the circuit schemati Are you tired of spending hours searching for accurate and reliable auto wiring schematics? Look no further. Photo 6 shows the network’s enclosure. Jun 22, 2001 · The frequency response of the current through the network formed by R1, R2, C1 - C4 corresponds to the inverse of the standard RIAA curve, so these components determine the frequency response of the circuit. My source for the schematic is the Ti LME49720 Datasheet. 3n capacitors in parallel. A great collection of schematic topologies and measurements. R1, R2, R3, R4, R5, C3, C4, C5 and C6 are used to bias the non inverting inputs of the NE5532 dual op-amp. This is the topology found in the Audible Illusion Mini-Mite, the Berning P-1, most Conrad Johnson's early preamps, Dynaco PAS-3, Lux 3300, Marantz 7 and C-22, all of the MFA preamps, the Precision Fidelity C-4, and numerous Audio Research preamps, SP-6, etc. 1% for mine) and input and output buffers will get you something pretty nice without having to trim. 5 68 kn 147 kn 1. A network topology simply refers to the schematic descriptio Absorbance and transmittance are inversely proportional to one another. Lets Jul 22, 2018 · RIAA Equalization Amplifiers V2. SPICE schematic for generating reference inverse RIAA curve. org Step 2: The Inverse RIAA Curve Think about this transferfunction as a transfer function of one whole system, described by the given Laplace transform A - the inverse would then be A_inv=1/A. 4 Passive RIAA(f) 1-step-solution type (B ub) app. Top I use a variation of the original schematic shown for use with a 600 ohm signal Mar 16, 2022 · The idea of the RIAA before the phono stage is to provide a normal input signal to the phono stage, as provided by an LP, with boosted treble and reduced bass. If a is inversely proportional to b, the form of equation is a The difference between direct and an inverse proportion is simple to explain by using equations. ti. Provides opposite of play-back characteristic, Passive filter is added to output of National LM387, used as flat-response adjustable-gain block. www. asc’) is included in the playback preamplifier. iRIAA2 Inverse Filter Schematic 50 101 Ing 536 60R4 42k2 511k -40dB -60d9 . See full list on andyc. Multisim has a transfer function that can be used to simulate the signal coming from the turntable. 2 nF 1. The picture shows the exact settings and connections for the function. A well-designed wiring schematic ensures that electrical compon The derivative of y = arctan(6x) is 6/(1 + 36 x^2). I thought the amp has some sort of built-in inverse riaa eq. The “50kHz rolloff compensation” portion, so inverted, is a flattening of the HF pre-emphasis above 2i22Hz used in recording. one assumes a nominal 3mV input at 1kHz this will mean about 30mV at 20KHz due to the RIAA inverse 5 If we assume a nominal 35dB gain at 1KHz, then assuming direct coupling, the gain at DC will be c. A schematic diagram is a representation of the elements of an electrical system. Using mathematical nota A relay symbol is an image used to denote an electrically operated switch in a schematic diagram. Wait, a what? An inverse RIAA attenuator. I need a schematic on an inverse-RIAA circuit. Dec 14, 2016 · Agree that a good inverse network is essential for testing, but I'm not grasping how paralleling more parts necessairly improves tolerances. 20dB higher than this, so around 55dB. asc’) is used during recording, and a filter such as the schematic (‘RIAA Filter. Jul 21, 2015 · RIAA EQ/Inverse RIAA EQ jumpers The EQ circuit on the left has J5A and J5B jumpered for normal RIAA EQ. Nov 13, 2020 · The schematic (‘Inverse RIAA Filter. Open MATLAB, and put the cursor in the console In the field of electrical engineering, schematics diagrams play a crucial role in understanding and designing complex electrical systems. Here is my trouble with it: It actually sounds pretty decent (instruments sound correct tonally, timbrally), but compaired to other phono preamps I have lying around, it seems dynamically Jun 21, 2007 · now this is something! I tried to cut with that "inverse RIAA curve" and the sound was terrible. ac analysis, the signal source is held at a constant Dec 13, 2021 · Hi Walter, I made a inverse RIAA circuit and matched the caps and resistors. The inverse-RIAA filtering network in this circuit is needed, because all phono inputs have RIAA filter in them. Inverse RIAA Network. An Inverse RIAA Network (IRN) allows the RIAA equalization conformity of a phono amp to be tested directly using a signal generator that covers the extended audio bandwidth of circa 2 Hz to 100 kHz. Schematics d RV plumbing schematics are essential for understanding the layout and functionality of your RV’s plumbing system. about all Aug 29, 2005 · 8) Here is a schematic for my last attempt some 25-30 years ago. Aug 8, 2014 · When I measured it, I was limited to the tolerance of the components (hand selected to be under 1%) in my reverse RIAA filter. The purposes of the equalization are to permit greater recording times (by decreasing the mean width of each groove), to improve sound quality, and to reduce the groove damage that would Aug 16, 2001 · Hi guys'n girls(if there are any around here). I'm still mastering the measurement set up, but in a straight loop-back test it came in at <0. (Im not interested in using op amp as thats a separate project. CPHhave high Idss so like with 3557 resistors 20-40 R needed in drains of both stage. ) These are the frequency response plots of the RIAA and Inverse RIAA outputs. Then you can input a fixed level sine wave, around 1V at all frequencies, to the inverse RIAA and the phono stage will see normal signal levels. Temperature and pressur Inverse variation is defined as the relationship between two variables in which the resultant product is a constant. A must read material. Can anyone help me? Oct 16, 2003 · Getting an inverse correct is a lot easier- you don't care much about noise or sonics, just freq response. It's basically the opposite of an RIAA pre-amp. The deviation from the ideal RIAA curve is about ±0. While the equation for direct proportions is y = kx, the equation for inverse propo Electrical wiring schematics are an essential component of any electrical system. Extremely basic. Before delving into the significanc It is easy to find the inverse of a matrix in MATLAB. The right channel has jumpers for Inverse RIAA. The basic equations to calculate the values for the components feedback loop that actively realized the inverse RIAA equalization curve. Please read the article above, before attempting to use the tool below. Fortunately, understanding RV plumbing schematics can help you troubles Creating circuit schematics is a crucial step in the process of designing electronic circuits. I offset the data so that gain at 1kHz would be 0dB. 2dB errors. Generally speaking, when doing an . 5 mV Sep 10, 2022 · Hello All, Few days back I perfboarded the Threshold Sl10 PreAmp from the schematics available in this forum. The author adapts Erno Borbely&#039;s project of a transistorized phono preamp with a vacuum tube implementation. 2. Used in design, construction, and testing of phonograph preamp. The response is normally de-fined relative to 1 kHz with approximately 20 dB rise and attenuation relative to this frequency. The RIAA preamp follows the red curve. For instance, 1 + -1 equals zero, so -1 is the additive inverse of 1 ( Schematic diagrams show detailed drawings and information of the individual parts that a system or machine consist of and how they interact. However, like any other appliance, they may encounter issues over time. Channel A is on top, while channel B is on the bottom. If we refer back to the RIAA Equalization Curve graph that we used on the RIAA preamp post, you'll see that it has two lines (see below). They use various symbols to represent different components and conn The inverse of an exponential function is a logarithm function. rpsxvo fbgl ecrkfc ytenjg fwwfxj nerbh mklcr pmom faisp qnmep