docx

100W Guitar Amplifier

  • 1星
  • 日期: 2015-12-20
  • 大小: 117.27KB
  • 所需积分:1分
  • 下载次数:0
  • favicon收藏
  • rep举报
  • 分享
  • free评论
标签: 100WGuitarAmplifier

100W Guitar Amplifier

文档内容节选

100W Guitar Amplifier Rod Elliott ESP Updated 04 Jan 2002Introduction Note  This project is superseded by a which has several useful additions  PCBs are available but only for the new ampGuitar amplifiers are always an interesting challenge The tone controls gain and overload characteristics are very individual and the ideal combination varies from one guitarist to the next and from one guitar to the next There is no amp that satisfies everyones requirements and this offering is not expected to......

100W Guitar Amplifier Rod Elliott (ESP) Updated 04 Jan 2002Introduction Note:  This project is superseded by a , which has several useful additions.  PCBs are available (but only for the new amp).Guitar amplifiers are always an interesting challenge. The tone controls, gain and overload characteristics are very individual, and the ideal combination varies from one guitarist to the next, and from one guitar to the next. There is no amp that satisfies everyone's requirements, and this offering is not expected to be an exception.One major difference however, is that if you build it yourself, you can modify things to suit your own needs, experimentation is the key to this circuit, which is presented in basic form, with every expectation that builders will modify just about everything.The amp is rated at 100W into a 4 Ohms load, as this is typical of a "combo" type amp with two 8 Ohm speakers in parallel. Alternatively, you can run the amp into a "quad" box (4 x 8 Ohm speakers in series parallel - see Figure 5) and will get about 60 Watts. For the really adventurous, 2 quad boxes and the amp head will provide 100W, but will be much louder than the twin. This is a common combination for guitarists, but it does make it hard for the sound guy to bring everything else up to the same level. The Pre-Amplifier The preamp circuit is shown in Figure 1, and has a few interesting characteristics that separate it from the "normal" - assuming that there is such a thing. This is a very basic design (this is deliberate), and is easy to build on Veroboard or similar. The gain structure is designed to provide a huge amount of gain, which is ideal for those guitarists who like to get that fully distorted "fat" sound.However, with a couple of simple changes, the preamp can be tamed to suit just about any style of playing. Likewise, the tone controls can be modified to suit anything from an electrified violin to a bass guitar - you might even find that for anything other than bass, they have a suitable range to cover most possibilities, and even a few bassists will find that they can get the punchy sound they want, without the low-end "waffle" that many bass players dislike. Figure 1 - Guitar Pre-AmplifierFrom Figure 1, you can see that the preamp uses a dual opamp as its only amplification. As shown, with a typical guitar input, it is possible to get a very fat overdrive sound, by winding up the volume, and then setting the master for a suitable level. The overall frequency response is deliberately limited to prevent extreme low-end waffle, and to cut the extreme highs to help reduce noise - not that it helps all that much, because with all that gain, noise is always going to be a problem.Note: The schematic has been modified slightly to improve the tone control performance (04 Jan 2002). A new schematic is now on line - the differences are relatively minor, but make the component values for the tone controls a bit cheaper (smaller value caps, and higher value pots). The power amp has been heavily revised, and the new version is also available.If a really quiet amp is desired, you should substitute a 5532 dual opamp. These are more expensive (and harder to get), but will offer a substantial noise reduction. If you don't need all the gain that is available, simply increase the value of the first 4k7 resistor - for even less noise and gain, increase the second 4k7 as well.If the bright switch is too bright (too much treble), increase the 1k resistor to tame it down again. Reduce the value to get more bite. The tone control arrangement shown will give zero output if all controls are set to minimum - this is unlikely to be a common requirement in use, but be aware of it when testing.The diode network at the output is designed to allow the preamp to generate a "soft" clipping characteristic when the volume is turned up. Because of the diode clipping, the power amp needs to have an input sensitivity of about 750mV for full output, otherwise it will not be possible to get full power even with the Master gain control at the maximum setting.Make sure that the input connectors are isolated from the chassis. The earth isolation components in the power supply help to prevent hum (especially when the amp is connected to other mains powered equipment).UPDATES: I have had quite a few enquiries about the input connection setup. This is almost an industry standard, and is quite the opposite of what you might think it means. The same basic idea is used on Fender amps, as well as many others. The Hi input is used for normal (relatively low output) guitar pickups, and is "Hi" gain. Lo is 6dB less gain, and is intended for high output pickups so the first amplifier stage does not distort. The switching jack on the Hi input means that when a guitar is connected to the Lo input, it forms a voltage divider because the other input is shorted to earth. I hope this clears up any confusion (it will probably create more!).I have also had several enquiries about the tone controls, one being that they don't do anything. If the preamp does not work properly, it is because it has been wired incorrectly - period! I know the circuit works, and it works very well, so please don't send e-mails claiming that it does not do what is claimed. For some reason, this project generates more e-mail than just about any other, and in all cases where I have had complaints, wiring errors have eventually been found.The golden rule here is to check the wiring, then keep on checking it until you find the error, since I can assure you that if it does not work there is at least one mistake, and probably more.Power Amplifier The power amp is based on the 60 Watt amp previously published (Project 03), but it has increased gain to match the preamp. It has also been modified to give a bit of extra punch - not to the standard of a valve amp, but somewhat better than the average transistor amplifier. Other modifications include the short circuit protection - the two little groups of components next to the bias diodes.Should the output be shorted, much more than the normal 7V peak will appear across the 1 Ohm resistors. This will turn on the appropriate transistor, cutting the base drive to the output stage. The effect is not particularly nice, but will save the output from instant destruction in the event of a short. Given the nature of stage work, a short circuit is something that will happen, it is only a matter of time. The circuit is designed not to operate under any normal conditions, but will limit the output current to about 8.5 Amps. Figure 2 - Power AmplifierAt the input end, there is provision for an an auxiliary output, and an input. The latter is switched by the jack, so you can use the "Out" and "In" connections for an external effects unit. Alternatively, the input jack can be used to connect an external preamp to the power amp, disconnecting the preamp.The speaker and line out connections allow up to two 8 Ohm speaker cabinets (giving 4 Ohms), and a line level output for connection to a direct injection (DI) box. The level is about 1.3V (or +5dBm) at full undistorted output - change the 560 Ohm resistor to modify the level if desired.The two 1 Ohm resistors must be rated at 10 Watts (they will still get quite hot, so mount them well away from other components). These can be mounted to the heatsink with small brackets if you want to keep them a bit cooler - remember to ensure that the heatsink can handle the extra heat input, as these two will add about 10 Watts of additional heat energy. The four 0.1 Ohm resistors should be 5W types. The amp is otherwise quite conventional. Use the parallel arrangement as shown, anything less will cause the transistors to be operated outside their safe operating area, which will result in the eventual failure of the output stage.Make sure that the two bias diodes are mounted well clear of anything that gets hot - including the heatsink. These diodes are the two in series. All diodes should be 1N4001 (or 1N400? - anything in the 1N400x range is fine). A heatsink is not needed for any of the driver transistors.The life of a guitar amp is a hard one, and I suggest that you use the largest heatsink you can afford, since it is very common to have elevated temperatures on stage (mainly due to all the lighting), and this reduces the safety margin that normally applies for domestic equipment. The heatsink should be rated at 0.5 degree C/Watt to allow for worst case long term operation at up to 40 degrees C (this is not uncommon on stage).Make sure that the speaker connectors are isolated from the chassis, to keep the integrity of the earth isolation components in the power supply.Power Supply WARNING - Do not attempt construction of the power supply if you do not know how to wire mains equipment. The power supply is again nice and simple, and does not even use traditional regulators for the preamp. A pair of zeners is sufficient to get the voltage we need, because the current is only quite low. The power transformer should be a toroidal for best performance, but a convention tranny will do if you cannot get the toroidal. Figure 3 - Power SupplyThe transformer rating should be 150VA minimum - there is no maximum, but the larger sizes start to get seriously expensive. Anything over 250VA is overkill, and will provide no benefit. The slow-blow fuse is needed if a toroidal transformer is used, because these have a much higher "inrush" current at power-on than a conventional transformer. Note that the 5 Amp rating is for operation from 220 to 240 Volt mains - you will need an 8 or 10 Amp fuse here for operation at 115 Volts.Use good quality electrolytics, since they will also be subjected to the higher than normal temperatures of stage work. The bridge rectifier should be a 35 Amp chassis mount type (mounted on the chassis with thermal compound). Use 1 Watt zener diodes, and make sure that the zener supply resistors (680 Ohm, also 1 Watt) are kept away from other components, as they will get quite warm in operation.The earth isolation components are designed to prevent hum from interconnected equipment, and provide safety for the guitarist (did I just hear 3,000 drummers saying "Why ??"). The 10 Ohm resistor stops any earth loop problems (the major cause of hum), and the 100nF capacitor bypasses radio frequencies. The bridge rectifier should be rated at at least 5A, and is designed to conduct fault currents. Should a major fault occur (such as the transformer breaking down between primary and secondary), the internal diodes will become short circuited (due to the overload). This type of fault is extremely rare, but it is better to be prepared than not.Another alternative is to use a pair of high current diodes in parallel (but facing in opposite directions). This will work well, but will probably cost as much (or even more) than the bridge.Fuses should be as specified - do not be tempted to use a higher rating (e.g. aluminium foil, a nail, or anything else that is not a fuse). Don't laugh, I have seen all of the above used in desperation. The result is that far more damage is done to the equipment than should have been the case, and there is always the added risk of electrocution, fire, or both.Electrical Safety Once mains wiring is completed, use heatshrink tubing to ensure that all connections are insulated. Exposed mains wiring is hazardous to your health, and can reduce life expectancy to a matter of a few seconds !Also, make sure that the mains lead is securely fastened, in a manner acceptable to local regulations. Ensure that the earth lead is longer than the active and neutral, and has some slack. This guarantees that it will be the last lead to break should the mains lead become detached from its restraint. The mains earth connection should use a separate bolt (do not use a component mounting bolt or screw), and must be very secure. Use washers, a lock washer and two nuts (the second is a locknut) to stop vibration from loosening the connection.Speaker Boxes The two suggested boxes are shown (in basic form only - you will need to work out the woodworking details yourself). The first (Figure 4) is a standard 2 speaker cabinet, and I strongly recommend using the open-back box, as this is the preferred option for most guitarists. Two 8 Ohm speakers are wired in parallel (giving 4 Ohms), and it is expected that with 12" speakers (300mm) this combination will be quite loud enough. Try to get speakers that are rated at at least 100W each - this safety margin is a requirement for guitar, since the amp will be overdriven for much of the time and this produces up to double the rated output of the amp.The details of finish, handles (and the actual dimensions) of the boxes I shall leave to the builder, but I will make a few comments:Tops and bottoms are shown as being inside the side panels. This does not really matter, since all corners should be reinforced with 25mm square (1") timber. All joints should be glued and screwed. Pre-drill the screw holes to prevent the end grain of the MDF from splitting. Use a router if available to round off all the edges and corners, and use corner protectors. Vinyl is still the most robust covering for stage gear, but carpet can be used if you prefer. Use strong handles, as the boxes will be quite heavy when completed. Side "pocket" handles are best for the quad, but a strap handle can be used for the twin. The baffle of the twin, and the top section of the quad are angled. This projects the sound towards the guitarist, and is better than propping the front edge on a brick or similar. The baffle is shown recessed. This is to allow for a grille frame, which should fit neatly inside the recess and be fastened with Velcro or grille mounting clips. Speakers should not be held in place with wood screws - use bolts, washers and nuts, or "T-nuts". Wood screws will eventually loosen, and the speakers will rattle.Generally, one thing to avoid is vented boxes - they just don't sound right for guitar. Naturally, if you like the sound of vented boxes, then go for it - guitar amps are probably one of the most personal amps in the world, and there is no right or wrong combination, as long as you get the sound you want. Figure 4 - Suggested Twin Speaker Box And WiringThe second example (Figure 5) is the classic "quad" box, and uses 4 x 8 Ohm speakers in series/parallel. This gives an impedance of 8 Ohms, so two quad boxes can be used if you really want the amp to be that loud. You might be able to get 4 Ohm speakers, in which case the series/parallel connection will give you a 4 Ohm box, so only one is needed. I suggest that the quad box also be open-backed, but this is not essential. One of the most popular guitar amps around uses closed back quads, and they sound pretty good to me. Figure 5 - Suggested Quad Speaker Box And WiringFor the speaker boxes, I recommend MDF (Medium Density Fibreboard). This is a much better material to work with than chipboard, and is also stronger. Chipboard has been used (and still is) by many manufacturers because of its one redeeming feature - it is cheap. MDF will cost quite a bit more, but the end result is worth the expense - a better finish, and a stronger box. Don't be tempted to use anything thinner than 19mm (3/4"), or the cabinet will resonate too much, and will also lack strength.Many manufacturers use a thin (typically about 6mm) fibre board at the back of open backed cabinets to provide some protection for the drivers, and a lead storage area. Don't ! Make the rear protection panel(s) from 19mm MDF too, since this will prevent the unwanted resonances from the thin material typically used.Speakers should also be fairly efficient if possible (> 90dB W/m), since a 3dB reduction in efficiency will result in the same SPL (Sound Pressure Level) output as an amp with half the power and 3dB more efficient speakers. Check out the local dealers for musical instrument speakers - do not use hi-fi speakers, or you will surely be disappointed - they are not designed for musical instrument applications, and usually sound awful.Also avoid loudspeakers with aluminium dome dust caps - they sound utterly disgusting when a guitar amp is overdriven, with a hard top-end that radiates at frequencies that are discordant. Any harmonic above the seventh is discordant (out of tune), and an overdriven guitar amp is one of the few instrument combinations that can create such high harmonics. As a result, most guitar speakers are designed to roll off the top end above about 7kHz or so to avoid this problem. An aluminium dome does the opposite, and radiates wildly at the upper frequencies. This is both unpredictable and unpleasant.Anecdote:  Some years ago, I was asked by a well known Australian guitarist if I could fly to Melbourne (from Sydney - about 1000 km) to solve this awful problem in the studio. It didn't matter how they miked the guitar amp, it still sounded terrible on the recording. It turned out that the aluminium dust cap was radiating so strongly at somewhere between 5kHz and 12kHz that it destroyed the sound, giving a most unappetising metallic edge to the music. The remedy was to carefully cut away the dust cap, and glue a piece of thin felt in its place. About an hour later (after the glue had dried), the result was that the recording engineer and guitarist alike were stunned at the difference - the sound was as smooth as silk (well, you know what I mean) and all the nastiness was gone.Most of the established guitar amp manufacturers use speakers specially made for them by one of a few specialist loudspeaker builders, and they are normally hard to get. Try music shops (or repair shops) to see if they have speakers that might be suitable. The second-hand market might be another good place to look - you might even be able to get a complete speaker box for a reasonable price, which saves having to do the woodwork !Effects As shown, the amp has no effects at all, but does have an effects send and receive (via the two input jacks). Internal tremolo and reverb can be added, and suitable circuits are available on the project pages. These are designed as "stand alone" effects, but can be integrated easily, using the effects loop already provided.100W Guitar Amplifier (Part 2) Rod Elliott (ESP) Page Created 28 Jan 2002Introduction The article showed the schematics and wiring of the 100W guitar amp.  Here are some pictures of the prototype, so you can see what the various bits look like.  Just as a refresher, the internal wiring diagram is shown - you will be able to see how this all goes together in the photos. Figure 1B - Internal WiringThe connections shown are virtually identical to those used in my prototype.  Noise is extremely low, and probably could have been lower if I had made the amp a little bigger.  All connectors must be fully insulated types, so there is no connection to chassis.  This is very important ! The photos below give you some idea what the final unit looks like.  Mine is really small, but I suggest that you make yours bigger.  The one I made will never have to put up with life on the road, so the metalwork (and cabinet) are cobbled together with whatever I could find in my workshop.  It's still very sturdy, but I know from experience just how sturdy a "live performance" amp needs to be.  If it will be damaged by 120kg of other gear sitting on top of it, in a truck, and on a bumpy road (all at the same time), then it probably won't survive. Make sure that your cabinet does not interfere with air flow around the heatsink.  Leaving it sticking out the back (as I did) is probably not ideal, but it must get proper ventilation.  The heatsink does not need to be as big as the one I used, but since there is no such thing as a heatsink that is too big, make sure you don't skimp on this very important component.The preamp (with the shield removed) and power amp are shown in more detail in the lower two photos.The photos of the outside are not as clear as they could be - black on black is always a pain to get good resolution. Note the shielding for the preamp.  Shield the inputs with sheet metal or some scrap unetched PCB material, and a similar shield over the preamp helps prevent noise pickup.  These are important for lowest noise level and to ensure stability.  The preamp has an enormous amount of gain, and internal feedback is highly undesirable.  Make certain that the shield does not create a hum loop!  If you use PCB material, it can be held in place with pieces of tinned copper wire joined to the ground bus for the pots.  Only one point of the shield should be in electrical contact with the bus - I used an engraving tool to make a separate copper "land" for the second (mechanical only) connection. The power amp mounts using a couple of pieces of steel as clamps for the transistors.  No other mounting is needed, and the amp is extremely solidly mounted by this method.  The only steel stock I had on hand was rusty - you can see the pitting in the image.  This does not affect anything, but it does look a little grotty (again, I was in a hurry ). Note that the PCBs you see in the photos are the prototypes.  The final boards are similar, but do look slightly different, as I changed some of the locations and made some other mods (these are incorporated in the prototypes by cut tracks and jumpers). For those who may not wish to build the amp and preamp boards, fully built and tested power amp modules are available (PCBs only - excludes hardware, pots, jacks, heatsink and power supply).  These will be supplied with sufficient documentation to make final wiring and assembly a breeze. The preamp is simple, and pre-wired versions of that are not available. The entire amp as you see it here was built (and documented) in two weekends (allowing time for mowing and other similarly exciting activities), so it can hardly be considered an arduous task to build one.  The case was made from MDF (in this instance Melamine coated, but only because I have a whole pile of the stuff).  The vinyl is stuck on with PVA wood glue, but (again for longevity and strength) I suggest that you use contact adhesive - the staples that you can see on the inside were to make sure that it didn't move while I did the next bit.  If you are more patient than I (or if you use contact adhesive), staples are not needed.  I would have used speaker carpet, but didn't have enough left. The actual details of the chassis I leave to the reader - I certainly don't recommend the method I used.  One relatively simple way to do it is to use a 2RU rack case, and install that in an MDF sleeve.  The sleeve can be covered with vinyl or carpet - both look good and wear well.
更多简介内容

推荐帖子

BQ24610芯片使用问题汇总
本帖最后由 qwqwqw2088 于 2020-5-18 09:50 编辑 BQ24610芯片在插入适配器后,芯片IC就很烫? A:BQ24610芯片在插入适配器后,芯片IC就很烫,没有接入电池,PG的灯亮了,其他引脚的信号都没来得及测量就关电源了,因为芯片太烫了,请问是什么原因,外围电路跟推荐的电路基本一致,是layout布局的问题,还是其他问题,请各位帮忙解答一下  
qwqwqw2088 【模拟与混合信号】
CC2630 TIMAC协议栈低功耗问题
项目功能: 采集5s数据发送——休眠5s——采集5s数据发送,循环往复 平台: CC2630 协议栈:timac_1_05_02_43299   问题描述:  在休眠5s的过程中,整体电流在7,8ma,只比数据发送低1ma,这是不科学的。验证没有event在跑的时候   是可以到3,400ua的电流消耗的(主要是板子上的传感器功耗)。   看了TI的
fish001 【无线连接】
今日10点开播:TI最新低成本 C2000™特性解读,快速上手精细电源与电机控制!
在不断发展的汽车和工业电源转换市场中,设计人员正在寻求能够帮助他们应对两个关键设计挑战的创新:如何轻松扩展实时控制资源?以及如何构建和维护长期的平台解决方案?   观看直播:(上班没空看直播?戳下面观看链接、填表,会后就会收到回放视频、PPT、问答整理等相关资料。) >>点此观看(直播间今日9:30开放)TI最新C2000实时控制器剖析直播:在功率变换应用中实现高性能的成本优化型
nmg 【微控制器 MCU】
在TI.com购买 MSP430开发板的流程说明
本帖写给参与6月2日  >>3小时实战+剖析 TI工程师手把手 带你全面入门MSP430 培训的网友(点此报名培训),说明如何以$4.3价格购买 实战所需的LP-MSP430FR2476(原价$14.99) 、 MSP-EXP430FR2355 (原价$12.99)开发板以及在TI.com上购买需要注意的事项。如阅读本帖后仍无法解决问题,请扫描下方二维码,入群询问。   本
nmg 【微控制器 MCU】
CC2630烧录无法识别芯片的问题
软件使用的是Smart Flash Programer2。 仿真烧录工具是XDS100V3。 板子烧录口是VCC-GND-TMS-TCK-RESET五个引脚,RESET不接也可以用。板子跟烧录器上用杜邦线对应连接即可。 刚开始总识别不到芯片,显示Unknown。解决办法是: 烧录器上的5.PD接口需要连接,如果板子没有给电源,仅由烧录器供电,则PD短接到VCC;否则就直接连
fish001 【无线连接】
应用笔记(AN4672)LPS22HB/LPS25HB 数字压力传感器:系统硬件集成指南
本应用笔记的目的是提供硬件集成指南,用于将意法半导体的 LPS22HB 和 LPS25HB 压力传感器集成到 客户的最终应用中。 将 LPS22HB/LPS25HB 压力和温度传感器集成到应用系统,例如便携式设备(PD)(例如 智能手机和可穿戴设备)、气象站或工业设备中时,应不损害传感器性能。在执行系统集成 时,可以考虑主要的机械和几何参数以及影响传感器性能的因素,从而优化这些参数。
littleshrimp MEMS传感器

评论

登录/注册

意见反馈

求资源

回顶部

datasheet推荐 换一换

About Us 关于我们 客户服务 联系方式 器件索引 网站地图 最新更新 手机版 版权声明

北京市海淀区知春路23号集成电路设计园量子银座1305 电话:(010)82350740 邮编:100191

电子工程世界版权所有 京ICP证060456号 京ICP备10001474号 电信业务审批[2006]字第258号函 京公海网安备110108001534 Copyright © 2005-2020 EEWORLD.com.cn, Inc. All rights reserved
$(function(){ var appid = $(".select li a").data("channel"); $(".select li a").click(function(){ var appid = $(this).data("channel"); $('.select dt').html($(this).html()); $('#channel').val(appid); }) })