Se hvad der er p Dolby demo disc. Dolby Atmos. This Dolby vs. DTS surround sound is a rather hotly debated issue. Many argue that DTS Digital Surround is capable of delivering better sound quality than its Dolby. DIY IRF6. 10 MOSFET Class A Headphone Amplifier Project. DIY Class A Headphone Amplifier. Not thrilled with how a computer soundcard drove my 3. Grado SR8. 0 headphones, I decided to build myself a desktop headphone amplifier for the office. In this instance I had plenty of voltage gain, but the sound card just runs out of gas with good headphones. This amplifier will only be suitable in setups where the input signal does not require voltage amplification such as the output of a preamplifier, mp. Dolby Headphone Test' title='Dolby Headphone Test' />This amplifier will delivery plenty of current to drive more demainding headphone types. This is a simple do it yourself DIY headphone amplifier project that is fashioned primarily after the Class A MOSFET Headphone Driver project by Greg Szekeres and to some extent Marks DIY Class A 2. SK1. 05. 8 MOSFET Amplifier Project. The amplifier concept is simple and follows a typical single ended class A circuit utilizing an active constant current source CCS in place of a passive resistor. A CCS doubles the efficiency of the circuit over that where a passive load resistor is used, bringing it to a maximum of 2. Figure 1 Basic Class A Amplifier Schematic. There are a couple of items to note. A FET follower circuit will be able to supply high current, but the voltage gain will be less than one. This amplifier will only be suitable in applications where the input signal does not require voltage amplification such as the output of an mp. Also, a simple single ended circuit like this will have no power supply ripple rejection and thus any noise in the power supply is going to go right through amplifier. For that reason, you will need to use a regulated power supply. Suitable inexpensive regulated wall wart power supplies can be purchased from Radio Shack. VDC and 7. 50m. A should be fine. The schematic for this headphone amplifier project is shown below in Figure 2. An IRF6. 10 MOSFET is used in this example, but a wide variety of FET devices can be used in its place. Ive had success with IRF5. IRF6. 10, IRF6. 11, IRF6. IRF7. 10, all of which worked well. You will want to stay away from IRF5. IRF5. 40 types commonly found in power supplies as there will be terrible roll off of the highs. Using a simple application of a common LM3. CCS set to draw 2. A. Figure 2 IRF6. Class A Headphone Amplifier Schematic. Construction DIY Class A Mosfet Headphone Amplifier. This headphone amplifier will reside primarily on my desk at work, so it needs to fit into an office environment. Fortunately I had a dead Plextor external CD ROM kicking around that would make for the perfect enclosure and blend in well on my desk. Even better yet, it already had a power switch, power adapter receptacle and RCA inputs on the back as well as a headphone jack on the front. Perfect The open hole you see on the back is where the USB header resided, but I had previously salvaged that for another project. Photograph 1 Plextor External CD ROM Enclosure. The amplifier is constructed on 1. Radio Shack 2. 76 1. I only used parts that I had on hand and you can see that I did not use any boutique parts. Plain but matched metal film resistors, 1u. F mylar input cap and 0. F polypropylene bypass cap on the output. The 0. 1u. F decoupling capacitor is also polypropylene. Some may prefer to use higher quality input and bypass caps and that should improve the sound. You can use carbon resistors, but I suggest you use metal film, particularly for the CCS due to their superior temperature stability over carbon. Photograph 2 DIY Headphone Amplifier on Protoboard. Wic Keygen. The heat sinks were salvaged from various dead components. The smaller heat sinks are about 1. Be sure to isolate the MOSFET and regulator from the heat sinks. Photograph 3 Construction of Headphone Amplifier. The headphone amplifier was first tested smoke test using a regulated power supply at very low voltage. The bias is set by varying the 1. MOSFET Source is at one half of the supply voltage Drain. You will want to check and reset the bias a few times in the first few hours as it will drift while everything settles in. The amp worked well between 1. VDC, but seemed to work best at 1. V and up. With a regulated supply there was no audible hum. That was not the case with an unregulated supply. Photograph 4 Construction of Headphone Amplifier. Next I got a chance to try out my new USB oscilloscope. It is a DSO 2. 15. MHz bandwidth and a maximum sample rate of 1. MSs. For those interested in such oscilloscopes here is a little more information about my experience with the DSO 2. USB PC Based Oscilloscope. I checked the sine wave response and as expected, the results were good across 2. Hz to 2. 0k. Hz the limits of my function generator. Below are two screen shots of the square wave response at 1. Hz and 4. 80. 0Hz. Photograph 5 1. 00. Hz Square Wave Response. Photograph 6 4. 80. Hz Square Wave Response. The top trace green is the input waveform and the bottom trace yellow is the output. My signal generator is not great and that is reflected in the quality of the input waves. If you compare the input voltage to the output voltage you will see than the gain of the circuit is about 0. As you can see in the 1. Hz trace, the square wave response is slightly tilted but stable. Tilting gradually decreases as the frequency increases and beyond about 3. Hz the square wave response is excellent up to 2. Hz which is the limit of my signal generator. Since music is comprised primarily of sine waves this is not a problem as the sine wave response was fine across the audible range. The final touches were to epoxy the CD ROM faceplate to an aluminum plate and put the enclosure back together. Since an mp. 3 player or computer will be used to control the volume, there is no potentiometer on the amplifier. The original volume control knob from the CD ROM was cut down and glued in place. Photograph 7 CD ROM Faceplate. Photograph 8 Finished Class A MOSFET Headphone Amplifier. Second Build Class A Mosfet Headphone Amplifier. UPDATE Dec 2. 01. The photos below show the second of these amplifiers that I built. This version of the Class A Mosfet Headphone Amplifier features a very high quality PCB that was made by a forum member and sent to me as a gift. Photograph 9 PCB for Class A MOSFET Headphone Amplifier. For the power supply I am using is a 2. VDC power supply from an older laptop. The 2. 0VDC is regulated to 1. VDC using a basic LM3. This makes for a ultra quiet power supply which is necessary for this amplifier circuit. Photograph 1. 0 Class A Mosfet Headphone Amp with LM3. Regulated Power Supply. The headphone amplifier was built into the enclosure from some sort of old Dolby processor 1. I had to modify slightly. Plain RCA jacks are used for input source. For the headphone output I am using a Neutrik Locking 14 phone jack. This is a very good quality 14 locking jack and I use these all the time in my builds. Photograph 1. 1 Second Finished Class A MOSFET Headphone Amplifier. Sound Class A Mosfet Headphone Amplifier. For a simple single ended amplifier design, the sound is pretty good to my ears. The amp drives my Grado SR8. I even prefer the sound compared to the built in integrated headphone amp on my NAD C1. Eye Doctor Mcp'>Eye Doctor Mcp. See the forum for more photographs and discussion about the DIY Class A MOSFET Headphone Amplifier project. Lenovo Tab 4 8 Plus review A budget tablet with Dolby Atmos Dolby Atmos technology is used in top end soundbars to bounce sound off your ceiling and deliver a spacious surround sound effect. So, it comes as a surprise to see it included in a tablet, such as the Lenovo Tab 4 8 Plus. The technology used for tablets and mobile devices, isnt as revolutionary as its soundbar counterpart, but the improved audio fidelity is still impressive. Does it sound as good as it looks, read on to see if the 2. READ NEXT Best tablet 2. Buying guide the best tablets of 2. Lenovo Tab 4 8 Plus review What you need to know. Atmos sound isnt an end to the Lenovo Tab 4 8 Plus talents, though. Its also equipped with a fingerprint reader, has an octa core CPU, 3. GB of RAM and 1. 6GB of storage, all topped with a crisp 1,2. On paper, this Android tablet seems to offer reasonably good value for money. Its nicely designed and that fingerprint reader is an unusual addition for a product this cheap, but theres strong opposition in this price bracket and below, in particular from Amazons 7in, 8in and 1. Fire HD tablets. READ NEXT Amazon Fire tablet review Cheap, cheerful, and highly commended. Lenovo Tab 4 8 Plus review Price and competition. There are multiple versions of the Tab 4 8 Plus the 1. GB Lenovo Tab 4 8 Plus, which costs 2. GB version for 5. Its available in two colours Aurora Black and Sparkling White and theres also a 4. G variant at around 2. It isnt short on competition. At this price, you can find a used or refurbished Apple i. Pad mini 2 check out e. Bay or Music. Magpie at 1. Vodafone Smart Tab N8, which comes with 4. G connectivity and for less than 2. Amazon Fire HD 1. Amazon Fire HD 8, and the 7in 5. Fire. The 8in Lenovo Yoga Tab 3 at 1. Acer Iconia A3 A4. READ NEXT Amazon Fire HD 1. Lenovo Tab 4 8 Plus review Design and build quality. The Lenovo Tab 4 8 Plus two forward facing speaker grilles are the first features that caught my attention. As mentioned above, the tablet supports Dolby Atmos through and it works wonders with the tablets audio output. Four sound profiles are available you can choose between Movie, Music, Game and Voice and you can customise the sound as well. Normally, I wouldnt bother with presets because in my experience they have little benefit. Here, however, I was pleasantly surprised, and each one had a positive effect on the listening experience. Through the modes listed above, I found that music sounded richer, movies and games benefited from a wider sound, while podcasts sounded much clearer. Bear in mind that this is still tablet class sound, so theres little bass to speak of, but for such a small device its audio output is impressive. Its not only the audio quality thats good, though. The Tab 4 8 Plus is also an elegantly designed tablet. At 7mm thick and 3. Tab 4 8 Plus is a very thin and lightweight device to carry around, its rounded edges make it comfortable to hold and its dual glass design gives it a premium look. One of its key features is its fingerprint reader, built into the power button, which sits alongside the volume rocker on the right hand side of the tablet. I found the location perfect for unlocking the device, but it isnt particularly reliable and only on rare occasions did the fingerprint reader work on the first try. Often, I had to try three times, at which point I opted to input my pin. Ive never had to faff around this much with a fingerprint reader for example, my Huawei P9 smartphone unlocks instantaneously. Dont get me wrong, having it is a definitive plus but Id want it to work more reliably than that. For connectivity, theres a USB Type C port for data transfers and power. A 3. 5mm headphone jack sits alongside it, at the top of the tablet. The tablet has dual band 8. Wi Fi and Bluetooth 4. On the left hand side, a micro. SD card slot sits under a plastic, Lenovo branded flap. If you want to take a picture, there are front 5 and rear 8 megapixel cameras and a flash on the rear to help out in low light. You can record video at 1. Image quality isnt the best, but it does suffice for the odd quick snap and Skype session. READ NEXT Amazon Fire HD 8 review The new Alexa tablet is best budget tablet in 2. Lenovo Tab 4 8 Plus review Display. The tablet has an 8in 1,2. IPS display, which gives it a 2. Tested with our colorimeter, I observed a 5. RGB gamut coverage, which is rather low. By comparison, the much cheaper Vodafone Smart Tab N8 achieved 7. RGB coverage. This means images wont look as vibrant on the Lenovo as they would on the Vodafone tablet and I wasnt too impressed with its colour accuracy either. Still with a contrast ratio of 7. READ NEXT Lenovo Yoga Tab 3 review. Lenovo Tab 4 8 Plus review Performance. The Tab 4 doesnt run stock Android but its installation of Android 7. SHAREit, an app used to send and receive files between devices, and SYNCit, which is used for synchronizing files across devices, plus the Microsoft Office apps it runs smoothly. Inside, youll find a 2. GHz octa core Cortex A5. Snapdragon 6. 25 processor and 3. GB of RAM. This provides enough horsepower to churn through intensive processes and multitasking. In the multi platform Geekbench 4 benchmark, the Tab 4 8 Plus achieves a 8. The Vodafone Smart Tab N8 only manages a score of 4. Playing basic games like Candy Crush isnt a problem, but dont expect to run more demanding titles such as Asphalt 8 smoothly. In the GFXBench Car Chase benchmark, the Tab 4 8 Plus manages to run at 3. In the less intense Manhattan 3. Lenovo Tab 4 8 Plus battery life. A non removable 4,8. Ah battery is housed inside, and this ran for 9hrs 4. Expert Reviews battery test identical to the Vodafone Smart Tab N8. Thats fine for a tablet like this, but it does lag behind the impressive 1. Lenovo Yoga Tab 3. READ NEXT Acer Iconia Tab 1. A3 A4. 0 review A great Android tablet for under 2. Lenovo Tab 4 8 Plus review Verdict. At first glance, the Lenovo Tab 4 8 Plus seemed to be a fantastic device. With an integrated fingerprint reader, two front facing Dolby Atmos speakers and splendid design, I had high hopes for it. But with a rather finicky fingerprint reader, sluggish performance in games and middling battery life its not the best way to spend your 2. If youre after a cheap tablet, the Amazon Fire HD 8 is far cheaper and offers almost as much for your money and, if you dont like the Amazon way of doing things, theres the Vodafone Smart Tab N8, which offers 4. G connectivity for a mere 1. Hardware. Processor. GHz Octa core Cortex A5. Snapdragon 6. 25. RAM3. GBScreen size. Screen resolution. Screen type. IPSFront camera. Rear camera. 8 megapixels. Flash. Yes. GPSYes. Compass. Yes. Storage free1. GBMemory card slot suppliedMicro. SD 2. 56. GBWi Fi. Bluetooth. 4. 2. NFCNAWireless data. NADimensions. 21. Weight. 30. 0g. Features. Operating system. Android 7. 1. 1. Battery size. Ah. Buying information. Warranty. One year RTBPrice SIM free inc VAT2.