DOCSLIB.ORG

A 45W Amplifier for 23Cm LDMOS Technology Offers Easy and Economical Microwave Power

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A 45W Amplifier for 23Cm LDMOS Technology Offers Easy and Economical Microwave Power RADCOM ♦ JUNE 2009 DR JOHN C WORSNOP, CENG, MIET, G4BAO ♦ E-MAIL: [email protected] TECHNICAL FEATURE A 45W amplifier for 23cm LDMOS technology offers easy and economical microwave power. smaller heatsink with a fan can be used, as shown in Photo 1 . A mini kit consisting of the PCB and MRF9045 is available [3] . This project uses small surface mount devices and requires some experience to construct and set up. It is therefore not suitable for novice constructors. CIRCUIT DESCRIPTION. Researching designs for the MRF9045 and similar devices it seemed that matching these devices to 50Ω at 1.3GHz requires a relatively simple microstrip network with low impedance (ie wide) lines on the input and output. Half a day playing with Appcad [4] and a Smith chart program [5] allowed me to get a reasonable handle on the required matching networks. Figure 1 shows the complete circuit diagram. In order to reduce losses, the final circuit avoids using trimmers and shunt capacitors. Device input and output impedances are matched to 50Ω using series low impedance lines TRL2, 4 and 5. ‘Shunt’ lines facilitate the final tuning. The open circuit shunt lines TRL3, TRL6 perform the function of the shunt capacitors of lumped element designs and there is a short circuited shunt line on the input, TRL1, grounded at PHOTO 1: A prototype 23cm power amplifier fitted to small aluminium heatsink with fins running the end by C5. horizontally. A small black fan gives enough airflow to keep the heatsink cool (Photo: Colin, G8LBS). The 28 volt supply is connected to the drain via an isolating quarter wave high describes a 45W Class impedance line, TRL7 and decoupled over TABLE 1 - COMPONENT LIST AB Power amplifier a wide range of frequencies by C3, C4, C5 Component Value Type Farnell reference covering the 1.3GHz and C6. band that requires only Positive gate bias is fed via a similar high R1, R3, R4 820Ω SMD 0805 9334890 a few watts of drive for impedance line, TRL8, from a 5V regulator R2 10k SMD preset 1173884 C1, C2, C3 100pF Np0 ceramic 0805 1414655 full output. It is a and potential divider to set the standing drain C8 47pF Np0 ceramic 1206 1414734 modern, safe current to 350mA. The gate supply is C11 47pF Np0 ceramic 0805 1414692 replacement for a single decoupled by C7, C8 and C10. The C4, C7 1nF Np0 ceramic 0805 718567 2C39A valve amplifier connection to the gate is via ‘stopper resistor’ C5, C9 10µF 35V SMD electrolytic 8823120 and does not require a R1. This is essential to the design, as it vastly C6 100nF X7 ceramic 0805 9406387 hazardous high voltage improve low frequency stability of the amplifier. C10 47µF 16V SMD electrolytic 498762 power supply. It is ideal LDMOS devices are remarkably robust but they U1 MRF9045 LDMOS power FET www.g4bao.com for use with a DB6NT are susceptible to too much gate voltage. The U2 TS2937CW SMD 5V regulator 7261365 or similar transverter, only time I've destroyed a device during TRL1-8 Microstrip matching lines on PCB a Kenwood TS2000X development is when I omitted this resistor. or similar transceiver, Without gate bias the amplifier takes very reaching a power level little current. Switching the 5V regulator from INTRODUCTION. For many years I operated where the 1.3GHz band becomes interesting. the press to talk (PTT) line is a convenient on 23cm with just 2 watts RF output but The design is very simple and based way to switch the amplifier in and out of never experienced the aircraft scatter and around a single Freescale [1] MRF9045 28 standby, minimising standby power consistent over-the-horizon contacts that I volt LDMOS device. The PCB is designed to fit consumption and heat generation. knew the band could support. Increasing the in to a readily available 72 x 55 x 30mm power by 13dB or so opened up the band in tinplate box [2] , and should be bolted to a CONSTRUCTION. The PA is built on a ways I didn’t think possible. This article suitable large, heatsink. Alternatively, a special 0.8mm thick low loss Teflon PCB, the 63 TECHNICAL FEATURE JUNE 2009 ♦ RADCOM overlay for which is shown +12 V bi as sup ply FIGURE 1: 23cm power amplifier circuit diagram. in Figure 2 . I developed the (optionally PTT switched) design using RF35 from R3 U2 Taconic Advanced Dielectrics 820Ω TS2937C W Division in Ireland [6] to In Ou t whom I gratefully Gn d 1 acknowledge the sample C9 C10 2 R2 of material that allowed the 10μ 47μ 10k +28 V 3 development. C8 My first attempt at the C7 820Ω 47p 1n design, using cheap FR4 C3 C4 C5 C6 material, worked after a R1 100p 1n 10μ 0μ1 fashion, but produced much 820Ω less power and, more TRL 7 importantly, eventually failed, TRL 5 Outpu t as the losses in the board TRL 8 caused the output microstrip 47 p Inpu t C1 TRL 2 TRL 4 U1 line to heat up alarmingly MRF904 5 TRL 6 and produce smoke after 100p about 5 minutes! TRL 1 TRL 3 Table 1 shows the component list for the C2 amplifier. The only really 100p critical component is the 1206 capacitor for the output coupling. The MRF9045 used in the design is the drain and gate tabs go, bolted the Connect the amplifier output to in a TO270 solder-down plastic package. spreader and PCB tightly together. I then a power meter/ dummy load capable of These are now becoming more popular and dropped the module, spreader side down, dissipating and measuring at least 50W. eliminate the need for hazardous beryllium on the kitchen ceramic hob, turned it on Connect the drain to 28 volts via an oxide in the package. and waited for the solder to melt. It duly ammeter on the 1A range. Connect the The device is soldered to a piece of copper did, leaving a shallow ‘pool’ of solder in the gate bias supply, starting with minimum plate approximately 27mm square and 1mm rectangular hole in the PCB. I carefully placed volts on the gate and very carefully increase thick, which acts as a heat spreader between the device into the hole, pressing down with the gate voltage until the device begins to the MRF9045 and the heatsink. (Actually I the tweezers. I then quickly slid the module take current. This onset is very sharp, so be used one face cut from a piece of waveguide off the heat, keeping the pressure on the very careful, as the drain current can easily 16). The spreader is soldered to the device until the solder set. Once the device is swing up to many amps if you are not careful. underside of the PCB and has two holes fitted you can solder in the other components. Set the drain current to 350mA. Switch off drilled in it to allow the spreader to be bolted I have used this technique many times now power and then switch the ammeter to the to the heatsink. with no ill effects on the devices. If you have 10A range. Switch back on. Apply 0.5W Applications note AN1907 [7] from a proper hotplate, all the better; I have now drive and check the input VSWR. It should Freescale gives very strict guidelines on gone ‘upmarket’, using an old dry clothes be better than about 1.7:1. temperatures for soldering these devices but iron, that I clamp upside down in a vice; If the input VSWR and output power are I thought, "what the heck, I can’t afford a that does the trick just as well. about right you’re finished, so leave well soldering oven, but I can afford to sacrifice No special precautions or techniques alone! If not, switch off. Remove one section a couple of devices if it doesn’t work". So I are required for fitting the other components, of one input tab at a time until the VSWR is tinned the underside of the PCB, the mating apart from good microwave practice. Be less than 1.7:1 and check the output power surface of the spreader and the topside where particularly careful to avoid excess solder, and current. If necessary, trim the output whiskers or excessive flux tabs in the same way for maximum power. residues as these can Do NOT try to make these adjustments affect performance. with the amplifier operating. Turn up the drive in 3dB steps to 2W and check that ALIGNMENT. Bolt the the power increases about 3dB each time assembled board and until it saturates. Now trim the output tab for heat spreader to a large minimum current consistent with maximum heatsink. The input and output power. It goes without saying, I hope, output matching tabs are that you disconnect both the drain and source split so that you can bias supplies before you trim the tabs. lengthen or shorten them by bridging them with RESULTS. Test results for a prototype solder, if necessary. Start amplifier are shown in Figures 3 and 4. with all the tabs linked for maximum length. CONCLUSIONS. This is an inexpensive PA Connect the input from and is relatively easy to build, with readily your 1.3GHz transmitter to available components and produces a useful FIGURE 2: PCB overlay. the amplifier input via a increase in output power for transverters and suitable SWR meter. transceivers. 64 RADCOM ♦ JUNE 2009 TECHNICAL FEATURE FIGURE 3: Measured FIGURE 4: gain and Typical efficiency for power a prototype output and amplifier.
Load more

Recommended publications
  • Design and Testing of High Voltage Rf Electronics
    DESIGN AND TESTING OF HIGH VOLTAGE RF ELECTRONICS M. Walden and R. Harrison Roke Manor Research [email protected] [email protected] www.roke.co.uk Introduction When one mentions High Voltage RF electronics, one thinks of the valve amplifier where the anode and grid supplies can be in the hundreds if not thousands of volts. But in a world where low voltage solid state devices are more usual, is there still a place for HV RF? We believe that there is, and to show our confidence in this, Roke has invested in a world beating High Voltage Testing Facility. In this paper we will describe some of the recent HV RF activities that have been performed at Roke. The paper concentrates on work to significantly extend the duty cycle of a VHF SSPA design to make it more attractive for scientific, medical, and other less obvious applications where valve amplifiers still dominate. We shall also discuss techniques and infrastructure for safely testing HV RF devices, from relatively simple interlocked test jigs to the workings of our new High Voltage Testing Facility. Extending the duty cycle of a VHF SSPA Previously we reported a low cost, high power, high voltage solid state amplifier which used commercially available MOSFET devices to achieve over 2kW of pulsed power [1]. This was designed for an application which required very short pulses and very low duty cycle (roughly 100µs pulse length and 0.1% duty cycle). 1 VHF SSPA and results Following this exciting result, Roke conducted some market research into other applications and markets where this type of amplifier might be of value.
    [Show full text]
  • DISTORTION Koosha Ahmadi 311176976 Digital Audio Systems, DESC9115, Semester 1 2012 Graduate Program in Audio and Acoustics Facu
    DISTORTION Koosha Ahmadi 311176976 Digital Audio Systems, DESC9115, Semester 1 2012 Graduate Program in Audio and Acoustics Faculty of Architecture, Design and Planning, The University of Sydney ABSTRACT By the mid 1950s rock guitarists began intentionally "doctoring" amplifiers and speakers in order to create even This work attempts to introduce the technology and the science harsher distortion. In 1956 guitarist Paul Burlison of the Johnny behind non-linear effects focusing on Distorted guitar effects. A Burnette Trio deliberately dislodged a vacuum tube in his short history of Distortion and its impact on modern music is amplifier to record "The Train Kept A-Rollin” after a reviewer followed by physical theories and modeling techniques raved about the sound Burlison’s damaged amplifier produced (Clipping, Harmonic Distortion, N-order Volterra serries) in during a live performance. Guitarist Link Wray began non-linear domain. We briefly go through Simple circuits and intentionally manipulating his amplifiers' vacuum tubes to approaches to analogue Distortion (Diode Clipping) afterwards. create a “noisy" and “dirty” sound for his solos after a similarly Basics of different approaches to designing digital accidental discovery. Wray also poked holes in his speaker Distortion (Wave-shaping, Simulation of analogue circuits) cones with pencils to further distort his tone. The resultant construct the final part of this review. sound can be heard on his highly influential 1958 instrumental, "Rumble". In 1961, the American instrumental rock band The Ventures 1. INTRODUCTION asked their friend session musician and electronics enthusiast Orville "Red" Rhodes for help recreating the “fuzz” sound caused by a faulty preamplifier on Grady Martin’s guitar track Distortion effects create "warm", "dirty" and "fuzzy" sounds by compressing the peaks of a musical instrument's sound wave for the Marty Robbins song "Don't Worry".
    [Show full text]
  • An Easily Constructed High-Quality Single-Ended 8W Amplifier Using
    An Easily Constructed High-Quality Single-Ended 8W Amplifier Using Standard Valves and the Lundahl LL 1664 Output Transformer Claus Byrith 2002 31-10-02 1 Preface After the publication a year ago of my paper Power Amplifiers with Valves I have received a lot of comments and very much to my surprise I learned that a great deal of interest in single-ended (SE) amplifiers exists, and I have been asked for a similar paper concerning such amplifiers. I admit that I have been very reluctant. I still remember when I was 17 and my financial situation finally permitted me to buy a decent transformer for 2 EL84s in push-pull (PP) capable of handling 10 Watts, and I remember the joy that came from listening to my first PP amplifier. I never thought that I was ever again to show any interest in SE amplifiers. The output transformer is by far the most critical component in any valve amplifier. The problems to be solved by the manufacturer of output transformers are even more complex for an SE-transformer than for a PP-transformer. I shall return to this matter later, but I can without exaggerating say that the output transformer found in the SE-amplifiers of almost every radio receiver, tape recorder or record player in the late fifties and in the sixties was very poor as was the design of the amplifiers. The advent of stereo in these years did not improve this situation. On the contrary it worsened because the public would only accept a small rise in the investment costs when upgrading to stereo.
    [Show full text]
  • Capacitor & Amplifier Distortions
    Oct mu.qxd 17/9/03 10:55 Page 1 COMPONENTS Capacitor & Amplifier Distortions Cyril Bateman uses his real-time distortion measuring system to investigate capacitor distortions in audio power amplifiers ssembled using polar based on more than eighty distortion rated polar capacitor I tested, aluminium electrolytic measurements, taken while measured -99.5dB with 6 volt bias A capacitors for C1, 3, 9 and investigating the possible reasons for and -94.4dB with 12 volt bias. Using 11, my workhorse 100 watt Maplin these improvements. 0.2 volt AC and larger test voltages, Mosfet amplifier, tested at 1kHz and In the past, many amplifier second and third harmonic distortions 25 watts into an 8Ω load, measured designers have stated that provided in polar aluminium electrolytic -81.5dB second harmonic, -91.4dB the capacitance value is chosen to capacitors increase dramatically, third harmonic, clearly meeting its ensure only a small AC signal voltage measured with and without DC bias claimed less than 0.01% distortion1. drop can appear across capacitors at voltage. Fig. 1. the lowest frequencies, then capacitor Tested using a 1 volt signal, this Replacing the four polar aluminium distortion can be ignored. capacitor’s third harmonic remained Fig. 1. Schematic electrolytic capacitors in this My original Capacitor Sounds close to -100dB, with no bias its circuit of my Maplin schematic, with the same value and series2 found measurable distortions second harmonic was -93.2dB, Mosfet 100W voltage rating bi-polar electrolytics occurring in un-biased polar increasing to -77.9dB at 6 volt bias amplifier, redrawn and no other changes, amplifier aluminium electrolytic capacitors and -72.9dB with 12 volt bias.
    [Show full text]
  • Valve Circuit Analysis
    Elliott Sound Products Valve Circuit Analysis Copyright © 2009 - Rod Elliott (ESP) Page Created 30 Oct 2009 Share | Valves Index Main Index Contents Introduction 2 - Test Preamp Circuit 3 - Guitar Preamp Circuit 4 - Tone Controls 5 - Phase Splitter 6 - Power Stage 7 - Improved Power Stage 8 - Output Transformer 9 - Clipping and Bias Shift 10 - Power Supply 11 - Heat & Vibration Conclusion References Introduction Finding a circuit for analysis is easy, but finding one with enough information is not. Because there are so many on the Net, guitar amps are a natural choice, and the one I selected is simply representative. There are literally hundreds of variations - even from a single manufacturer. The one used for preamp analysis is from the Marshall model 1959 (aka JCM800), but the choice was fairly arbitrary. I selected this one because it provides voltage readings for the various points on the circuit, however some of these were impossible and have been corrected. Unlike a transistor circuit where various parameters are more or less fixed (such as the base-emitter voltage), many things can change in a valve circuit. They don't even remain fixed once the design is complete - as the valves age, voltages change. Some relationships are absolute - if the current through the plate resistor of a valve stage is known for example, then we know that the current through the cathode resistor is the same - it cannot be different unless there is a serious fault somewhere. Ohm's law tells us the current through the plate and cathode resistors, based on their value and the voltage measured across either or both of them.
    [Show full text]
  • Marshall Amplifier Emulation
    California State University, Monterey Bay Digital Commons @ CSUMB Capstone Projects and Master's Theses Capstone Projects and Master's Theses 5-2018 Marshall Amplifier Emulation Peter Alvarez California State University, Monterey Bay Follow this and additional works at: https://digitalcommons.csumb.edu/caps_thes_all Recommended Citation Alvarez, Peter, "Marshall Amplifier Emulation" (2018). Capstone Projects and Master's Theses. 314. https://digitalcommons.csumb.edu/caps_thes_all/314 This Capstone Project (Open Access) is brought to you for free and open access by the Capstone Projects and Master's Theses at Digital Commons @ CSUMB. It has been accepted for inclusion in Capstone Projects and Master's Theses by an authorized administrator of Digital Commons @ CSUMB. For more information, please contact [email protected]. Peter Alvarez 5/2/18 MPA 475 Prof. Sammons Marshall Amplifier Emulation Just a little over a half a century ago down the street from our school (CSUMB), a well known artist by the name of Jimi Hendrix secured his right of passage into music history upon setting his Stratocaster ablaze in the final moments of The Jimi Hendrix Experience’s set during the 1967 Monterey Pop Festival. Behind the flames of the guitar a large row of Marshall amplifiers from the UK surrounding the back of the stage can be seen. By combining American guitars with British amplifiers, Hendrix and many other guitarists of his generation were able to achieve sounds and tones like no other inspiring guitarists over the next several decades including myself. Since I started playing, I have spent most of my musical career chasing those classic blues/rock tones I have come to admire so dearly.
    [Show full text]
  • Thermionic Valves
    Web: http://www.pearl-hifi.com 86008, 2106 33 Ave. SW, Calgary, AB; CAN T2T 1Z6 E-mail: [email protected] Ph: +.1.403.244.4434 Fx: +.1.403.245.4456 Inc. Perkins Electro-Acoustic Research Lab, Inc. ❦ Engineering and Intuition Serving the Soul of Music Please note that the links in the PEARL logotype above are “live” and can be used to direct your web browser to our site or to open an e-mail message window addressed to ourselves. To view our item listings on eBay, click here. To see the feedback we have left for our customers, click here. This document has been prepared as a public service . Any and all trademarks and logotypes used herein are the property of their owners. It is our intent to provide this document in accordance with the stipulations with respect to “fair use” as delineated in Copyrights - Chapter 1: Subject Matter and Scope of Copyright; Sec. 107. Limitations on exclusive rights: Fair Use. Public access to copy of this document is provided on the website of Cornell Law School at http://www4.law.cornell.edu/uscode/17/107.html and is here reproduced below: Sec. 107. - Limitations on exclusive rights: Fair Use Notwithstanding the provisions of sections 106 and 106A, the fair use of a copyrighted work, includ- ing such use by reproduction in copies or phono records or by any other means specified by that section, for purposes such as criticism, comment, news reporting, teaching (including multiple copies for class- room use), scholarship, or research, is not an infringement of copyright.
    [Show full text]
  • Stereo Valve Power Amplifier
    Stereo valve power amplifier For most of us a high power valve amplifier is unaffordable. This kit changes that, so that now everybody can enjoy that sublime "valve sound". Total solder points: 700 Difficulty level: beginner 1 2 3 4 5 advanced K4040K4040 ILLUSTRATED ASSEMBLY MANUAL H4040IP-1 Features & specifications Features: Pure valve sound with high quality EL34 valves. High quality black and chrome housing. Chrome valve socket covers. Easy bias adjustment with LED indication. Removable bottom for easy access and service. High quality capacitors and components. Gold plated input and speaker terminals. Standby function. Soft start circuit for power transformer. Specifications: 2 x 90Wrms in 4 or 8W. Up to 2 x 15Wrms full class A. Bandwidth: 8Hz to 80KHz (-3dB/1W). Harmonic distortion: 0.1% @ 1W/1KHz. Signal to noise ratio: >105dB (A weighted). Input sensitivity: 1Vrms. 115VAC or 230VAC / 500VA max. modifications reserved 2 Assembly hints 1. Assembly (Skipping this can lead to troubles ! ) Ok, so we have your attention. These hints will help you to make this project successful. Read them carefully. 1.1 Make sure you have the right tools: A good quality soldering iron (25-40W) with a small tip. Wipe it often on a wet sponge or cloth, to keep it clean; then apply solder to the tip, to give it a wet look. This is called ‘thinning’ and will protect the tip, and enables you to make good connections. When solder rolls off the tip, it needs cleaning. Thin raisin-core solder. Do not use any flux or grease. A diagonal cutter to trim excess wires.
    [Show full text]
  • Audio Frequency Interference (AFI) {Reprinted from Radio Communication
    Tony Tregale, VK3QQ FEDERAL EMC CO-ORDINATOR 38 Wattle Drive. Watsonia. Vic 3087 This month we have reprinted an article which appeared in AR in September 1974. Although the monetary values have increased since this time the basic problems are still the same and the solutions may help many of our younger amateurs and members. Audio frequency interference (AFI) {Reprinted from Radio Communication. April 1973) P W Waters, G30JV (Reprinted from Amateur Radio. September 1974) 8 Gay Bowers. Hockley. Essex. UK THE PROBLEM THE CAUSE The current boom in hi-fi sales has led to an Before discussing the various ways in increase in the number of cases of interference which this kind of interference can be caused by radio transmitters operating in prevented, it is necessary to understand how close proximity to audio equipment. Almost the RF signal reaches the amplifier, is rectified, all audio equipment now being produced for and emerges at the speaker as an unwanted the domestic market is enti rely solid state and signal. Fig 1 shows typical audio amplifier low this changeover from valves to transistors has signal stages. In the case of the transistor coincided with a hi-fi boom, making it difficult version notice the base/emitter junction. This to assess to what extent transistors are forms a fairly effective junction diode and any responsible for the increase in the number of RF signal that reaches this stage will be cases of interference. Certainly transistorised rectified and passed on as an audio signal to equipment appears to be far more susceptible the following stages.
    [Show full text]
  • Digital Modeling/Implementation of Valve Amplifiers Senior Project Proposal By: Cody Frye & Mitchell Gould Advisor: Dr
    Digital Modeling/Implementation of Valve Amplifiers Senior Project Proposal By: Cody Frye & Mitchell Gould Advisor: Dr. Lu 1 TABLE OF CONTENT I. Introduction………………………………………………………………....pg. 3 II. Motivation and Objective…………………………………………………...pg. 3 III. System Description………………………………………………………….pg. 3 IV. Methods……………………………………………………………………..pg. 4 V. Preliminary Results………………………………………………………....pg. 5 VI. Bill of Material……………………………………………………………...pg. 8 VII. Schedule and Labor………………………………………………………....pg. 9 VIII. Summary and Conclusion…………………………………………………...pg. 9 IX. References…………………………………………………………………..pg. 10 2 Introduction It is estimated that seventy five percent of the market for vacuum tubes is taken up by electric guitar amplifiers. Since tubes were first used in guitar amplifiers in the 50’s and 60’s, their signature sound has become a staple for rock guitar players. Valve amplifiers come in a broad variety of shapes and sizes. Every model has its own signature tone that musicians specifically seek out. When it plays loudly, the sound of vacuum tube amplifier arguably presents much better than the sound from a solid state amplifier because of the more musical and smoother clipping. Also, since there are much greater operating voltages for valves, they have a much greater dynamic range. Unfortunately vacuum tubes are large components that overheat often. In addition, tubes have a short life span and they can burn out at any time. Sometimes this even can cause damage to the transformer and other components. Once they burn out, they often need to be replaced quickly. This is caused by the higher power consumption that results in a lot of heat being generated within the valves. The downside of using a tube amplifier is not only the overheating and aging problems.
    [Show full text]
  • Building Valve Amplifiers
    //SYS21///INTEGRAS/ELS/PAGINATION/ELSEVIER UK/BVA/3B2/REVISES_23-04-04/0750656956-CH000-PRE- LIMS.3D – 1 – [1–8/8] 5.5.2004 11:48AM Building Valve Amplifiers This Page is Intentionally Left Blank //SYS21///INTEGRAS/ELS/PAGINATION/ELSEVIER UK/BVA/3B2/REVISES_23-04-04/0750656956-CH000-PRE- LIMS.3D – 3 – [1–8/8] 5.5.2004 11:48AM Building Valve Amplifiers Morgan Jones AMSTERDAM · BOSTON · HEIDELBERG · LONDON NEW YORK · OXFORD · PARIS · SAN DIEGO SAN FRANCISCO · SINGAPORE · SYDNEY · TOKYO Newnes is an imprint of Elsevier //SYS21///INTEGRAS/ELS/PAGINATION/ELSEVIER UK/BVA/3B2/REVISES_23-04-04/0750656956-CH000-PRE- LIMS.3D – 4 – [1–8/8] 5.5.2004 11:48AM Newnes An imprint of Elsevier Linacre House, Jordan Hill, Oxford OX2 8DP 200 Wheeler Road, Burlington, MA 01803 First published 2004 Copyright Ó 2004, Morgan Jones. All rights reserved The right of Morgan Jones to be identified as the author of this work has been asserted in accordance with the Copyright, Designs and Patents Act 1988 All photographs (including front cover) by Morgan Jones No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1T 4LP. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publisher.
    [Show full text]
  • Physics Explains Why Rock Musicians Prefer Valve Amps 8 February 2017
    Physics explains why rock musicians prefer valve amps 8 February 2017 For many guitarists, the rich, warm sound of an Professor Keeports said: "The output from the amp overdriven valve amp – think AC/DC's crunchy showed that a moderately overdriven valve preamp Marshall rhythm tones or Carlos Santana's singing produced prominent 2nd and 4th harmonics at 400 Mesa Boogie-fuelled leads – can't be beaten. and 800 Hz, and only a very weak 3rd harmonic at 600 Hz. For the solid state power amp, this pattern But why is the valve sound so sought after? David was reversed. All of this behavior is consistent with Keeports, a physics professor from Mills College in the common claim about the harmonics that valve California, looked at the science of valve amps for and solid state amplifiers produce. But the story is the journal Physics Education, to explain why their not quite so simple. Overdriving the valve preamp sound is 'better' to the ears of so many guitarists. harder produces strong odd harmonics." Professor Keeports said: "Although solid state "The shift toward odd harmonics at increasing gain diodes and transistors are cheaper, more practical, is a characteristic of valve amplifiers that further and technologically more advanced than glass explains their appeal. An electric guitar player can valves, valves survive because so many guitarists overdrive an amp two ways: by turning up the are exacting about their tone, and prefer the sound amp's gain control, and by attacking guitar strings a valve amp gives them." more strongly. Experienced guitarists don't just play their guitar – they also play the amplifier.
    [Show full text]