Several years ago, National Semiconductor came out with some very high performance, easy to use audio power LM amplifier ICs. I was in need of an extra amplifier so I could biamp some of my home-built electrostatic loudspeakers so I tried the LM chip. LM amplifier was chosen because of the ease of use, power output, turn-on and off thump suppression, low distortion, and built-in protection against shorts and thermal runaway.
This is woefully inadequate and leads to distortion at fairly low volume levels as the power supply sags under the load. The pendulum has swung the other way and now many audiophiles are putting proper amounts of energy storage into the power supply.
After a few people burned up some expensive speakers they came to realize what the network is for and that dead speakers sound much worse than Zobel networks, so these days most people are using the Zobel network. I have used my amp to drive electrostatic speakers, a notoriously difficult load due to the capacitive reactance, and never had ANY stability problems whatsoever. My amp was built using a schematic diagram pulled right off the NS data sheet, with the power supply added.
Maybe the tweaking mentality about manufacturer supplied schematics comes from not understanding proper construction practices. One thing that is key to getting good performance from an LM amplifier is to use proper grounding. Click here for the schematic diagram showing the star ground Usually, the housing is the most expensive part of the amp. It has to dissipate heat from the amp ICs and power transformer, it has to look acceptable, and it has to be large enough to hold everything.
The box originally housed a cell phone diversity antenna amplifier. There were a bunch of connectors going through holes in the sides of the box. I was able to use some of them, but not others, so they were filled using Bondo auto body filler. First I taped some scraps of PCB material to the inside of the box then smeared the Bondo into the hole from the outside. After the Bondo hardened, I sanded the outside surface flush with the rest of the aluminum.
It has worked out quite well and I recommend this technique to anyone who is recycling surplus enclosures. I added a few more holes where I needed them, enlarged a couple of the existing holes, then applied the finish. One of my other hobbies is restoring antique radios. I have one very special radio in my collection- a Neutrowound Super Six.
This radio must have looked like it came from outer space back in At that time most radios were plain, rectangular wood boxes. This one was is a steel box with a very unusual look provided by the nickel plated tube covers that protrude through the top, and the exotic painted finish- cracked blue over orange!
I like the finish on that radio a lot so I decided to try to duplicate it on my LM amplifier.Know Your IC seeks to demystify common Integrated Circuits and allows people to understand them to a point where they can use them in their own projects. This episode will feature the LM a popular op amp chip. We will go over the chip functions and a bit of history.
And we will teach you how to build a simple amplifier with the chip! Op-amps are perfect when you need to take a signal and have it go much higher than the original, for example doing audio amplification. Wikipedia has a great history of the op-amp and it's development. LM is made specificly for low voltage applications. Different op-amps will have different requirements, always check out the data sheet! The most interesting part about this chip i feel is the gain function. If you put a capacitor between pins 1 and 8, you can control the amount of gain the amp has.
The bypass allows you to access the input un-amplified, if you so desire.LM3886 super gainclone amplifier DIY
Our project we will be doing to demonstrate the LM is a simple audio amp. A similar design is used in "cracker box" amps. This version is completed using minimal parts, you will need: 1 LM 1 10 Ohm Resistor 1 uf Electrolytic Capicitor 1.
Once you have the parts layout the circuit, please review the circuit and the layout pictures i've included. If any parts smell like burning or are hot, disconnect the power right away! You can control the volume with the knob. Now that you have your own little amp you can easily make projects like the cracker box amp.
Using Integrated circuits can be fun and easy once you get into it! Hope you enjoyed this latest Know Your IC installment. Feel free to do you own as well, and maybe we can get a full guide together.There are many instances where a simple and reliable power amplifier is needed - rear and centre channel speakers for surround-sound, beefing up the PC speakers, etc.
This project unlike most of the others is based almost directly on the 'typical application' circuit in the National Semiconductor specification sheet. As it turns out, the typical application circuit is not bad - would I go so far as to say hi-fi in the audiophile sense? Perhaps - with caveats. It has good noise and distortion figures, and is remarkably simple to build if you have the PCB.
The sound quality is excellent!
As long as the protection circuitry is never allowed to operate, the performance is exemplary in all respects. Much as I like the idea, no-one else seemed to be interested, so the small amount of PCB real estate thus liberated was used to refine the layout and provide space for input and power connectors. Figure 1 shows the original schematic as shown when this project was originally published.
It is almost the same as in the application note redrawnpolyester bypass capacitors have been added, and the mute circuit has been disabled this function would more commonly be applied in the preamp, and is not particularly useful anyway IMHO.
Voltage gain is 27dB as shown, but this can be changed by using a different value resistor for the feedback path R3, currently 22k, between pins 3 and 9. The inductor consists of 10 turns of 0. The insulation must be scraped off each end and the wire is soldered to the ends of the resistor. The 10 Ohm and 2.
All electrolytic capacitors should be rated at 50V if at all possible, and the nF 0. To enable maximum power, it is important to get the lowest possible case to heatsink thermal resistance. This will be achieved by mounting with no insulating mica washer, but be warned that the heatsink will be at the -ve supply voltage and will have to be insulated from the chassis. For more info on reducing thermal resistance, read the article on the design of heatsinks - the same principles can be applied to ICs - even running in parallel.
I haven't tried it with this unit, but it is possible by using a low resistance in series with the outputs to balance the load. I have seen it done very badlyand the results were not pretty. The schematic for Revision-B boards is shown above.
It is almost identical, except the SIM connections have been deleted and a few component designations have been moved around. Smaller values can be used for C1 if the amp is to be used for tweeters around nF is fine. If the amp is to be used for midrange or tweeter in a biamped or triamped system, C1 may be reduced in value to nF -3dB at 72Hz.
The new PCB allows you to operate the amp as dual mono - the PCB track can be split, and each amp is powered from its own supply.The LM is a low power audio frequency amplifier which is very commonly used in small audio amplifiers.
The IC consumes very less power and hence can be operated using a 9V battery easily. It can easily drive an 8-ohm speaker with a variable gain of 20 to Volume control and gain control is also possible in this. So, if you are looking for an audio amplifier IC which can be powered using a battery for a portable application to drive an 8-ohm speaker then this IC might be the right choice for you.
For driving heavy speakers you have to use the power amplifier ICs. The LM only requires a couple of capacitors and resistors to start working. The IC is powered using the pin 6 typically 5 or 9V and the ground pin 4 is connected to the ground. The inverting pin pin 2 is normally grounded and the Non-inverting pin pin 3 is provided with the Audio signal.
This audio signal can be from a microphone or even from a 3. The 10k resistor is added in series with the audio signal to act as a volume control. You can ignore this potentiometer if you want to operate in full volume. The pin 1 and pin 8 are used to set the gain of the Amplifier. If there is nothing connected between these pins then the default gain will be 26 dB, but we can connect a 10 uF capacitor across it to get the maximum ain of the IC which is 46dB.
The pin 7 is used to connect a filtering capacitor 0. The amplified audio signal can be obtained from the pin 5 which is connected to a 8-ohm speaker through a filtering capacitor. The RC network with 0. Subscribe to stay updated with industry's latest Electronics components and news. Component Datasheet. LM Audio Amplifier Datasheet. Tags Audio Amplifier.
Get Our Weekly Newsletter! Armor IPX enclosures have a rugged tandem through-hole design which simplifies installation. High Performance 2. The 2. SMP Series Connectors. SMP series connectors are commonly used in miniaturized high-frequency coaxial modules.
EZ Connectors. EZ connectors feature a no trim braid, eliminating a time-consuming step and reducing FOD.Oct 10 The output signals of the six inverters are opposite to the input signals. The inverter can reverse the phase of the input signal by degrees. This circuit is used in analog circuits, such as audio Also known as inverter. The following is a The device requires a high signal on both A and B in order to set the input data line high; a low signal on either input will set the input data l Oct 9 Darlington transistor means there are two transistor in one package connected to increase gain at output.
TIP transistor has a lot of good features like 5A collector current, max emitter-base voltage is 5V, max collector dissipation is 65 watt, m IntroductionLM Quad differential comparator consist of four independent voltage comparators. It is a common integrated circuit and is mainly used in high-voltage digital logic gate circuits.
Single Chip 50 Watt / 8 Ohm Power Amplifier
Using LM can easily form various voltage comparator circuits and oscillator circuits. The content of comparison includes component parameters, packaging, application areas, and their circuit diagrams, etc.
I DescriptionThis blog mainly discusses and solves the following problem: How to use LM voltage comparator to make a reservoir water level gauge?
According to water level, this design performs signal processing and controls the potential of multiple voltage comparators, so the output will change DescriptionLM Quad differential comparator consist of four independent voltage comparators. IntroductionThe 74HC is an 8-bit serial-in or parallel-out shift register with a storage register and 3-state outputs.
This article introduces Toggle navigation.Post a Comment. Zynsonix Link. Given that I mostly enjoy building tube amps that could have been built in the s, this is a huge departure; we are zooming along to technology! The amplifier made use of the National Semiconductor LM, a 56 watt chip and relatively low capacitance. Likely the most popular chips are the LM and LM After reading about the various kits available, I settled on the LM from Chipamp Electronics as I liked the idea of additional capacitance in the power supply.
The Chipamp LM Stereo Kit Aside for the boards and the limited number of parts, the build would require a transformer, a box, heatsinks, heatsink mounting compound, binding posts, RCAs, switches, an IEC inlet with fuse, wire, standoffs, etc.
After roughly deciding on where each part would reside within Photoshop, I settled on a 7" x 12" x 3" aluminum box. See the rough layout below. Chassis layout created in Photoshop I prefer to fit the components into a case where there is enough room to breath, but there isn't a significant waste of space at the same time, so I generally avoid the 17" and 19" wide rack style enclosures.
Other brand options out there are AnTek and Plitron. Chassis with parts in place. For the heatsinks, I found some reasonably priced ones on ebay that had mounting holes for screws. I installed 1" aluminum standoffs on the heatsinks so I could mount them to the chassis with the fins facing the vent holes I planned to drill.
I used some generic yet very solid gold plated binding posts for the rear. The IEC inlet is mounted in a slightly odd position, but was necessary considering the small form factor. Many electronics contain high voltages that can kill, and mods, if performed improperly, can be a fire hazard.
Please keep this in mind. No comments:. Newer Post Older Post Home. Subscribe to: Post Comments Atom. Popular Posts. Rear of unit with binding posts and D panel USB input.LM noise issue. Hi i have a strange issue with my gainclone. Schematic attached here. This noise occurs when i connect it to my high pass active crossover. Connected to another source the gainclone has no issue Another discrete amp connected to the same active Xover no issue.
Can anyone help. Attached Images lm schematic. PCB layout.
In case it can help here is the PCB layout. Attached Images lm pc board. Your chance to find a solution will increase, if you post the cross-over schematic as well.
You could compare the values of Ri, Rin, Ci and Cin of the gainclone to the corresponding resistors and capacitors of the other discrete amplifier to start with. Hi, the decoupling is not located in the best position. PIN5 desperately needs decoupling. Try changing the two 10R to 4r7 or maybe even 2r7. The 22uF in the NFB is too small.
Try 47uF. I cannot see the speaker return. Hi andrew thanks for the reply will do the mods you advised. Dou you mean add additional decoupling for pin 5? There is an error in the schematic for the zobel network its correct on the PCB. Not in original circuit i've added it.
Speaker return is the green circle next to the caps the other circle is for power ground.
Know Your IC: LM386
Do you have any other suggestions. Thanks pacific for your reply i'll add it soon. Look at the length of the route from PIN5 to the decoupling cap.