The Audio Pages

Numerical Index of Projects
Page Last Updated - 27 June 2009

Projects 1-9   10-19   20-29   30-39   40-49   50-59   60-69   70-79   80-89   90-99   100-109   110 - 119   120 -

No.	Project	Description	PCB
01	A Better Volume Control	A volume control using a linear pot that is much better than most log pots
02	Simple High Quality Hi-Fi Preamp	As it says - simple, high quality preamp. Has all the facilities normally expected
03	60W / 8 Ohm Power Amplifier	(Updated) My old faithful power amp design. - See Project 3A	PCB
04	Dual Power Supply	A power supply that is adaptable for most power amps
05	Preamplifier Power Supply	Uses External AC Adapter. Safe and effective, low noise and no hum! (PCB replaced by P05A)
05A	Preamplifier Power Supply	All the features of the P05, but much more versatile. Includes 'Loss of AC' detector.
05B	Preamplifier Power Supply	All the features of the original P05A plus a complete muting circuit.	PCB
06	Phono (RIAA) Preamp	Very high quality moving magnet phono preamp - few circuits will better this one.	PCB
07	Discrete Op-Amp	Class-A Output. Intended as an experimental device - works extremely well
08	2-Way Electronic Crossover	Conventional 3rd order electronic crossover
09	24dB/Octave 2/3-Way Xover	Linkwitz-Riley alignment. This is the optimum choice for any active sysyem - Rev-B boards	PCB
9a	A Reader's Xover	This is well worth reading if you can't decide on biamping
10	20 Watt Class-A Power amp	True Class-A power amp for low power systems or tri-amping
11	Pink Noise Generator	For loudspeaker and room acoustics testing
12	Current Feedback Amp	An updated version of a very old 60W / 8 Ohm design
12a	El-Cheapo	This is the real El-Cheapo, presented in more or less original form
13	Low Noise Preamplifier	Simple unbalanced design, suitable for microphones - very low noise
14	Power Amp Bridge Adapter	A conventional adapter for bridging power amplifiers	PCB
15	Capacitance Multiplier Supply	Extremely low ripple supply with less power dissipation than a regulator
16	Audio Millivoltmeter	For Testing Amplifiers (etc) - An analogue design, 3mV to 30V with dB scale
17	A-Weighting filter	For noise measurements. Ideal for use with the AC Millivoltmeter above
18	Simple Surround Sound Decoder	A line-level version of the "Hafler matrix" decoder
19	Single Chip 50W Power Amplifier	Using the National Semiconductor LM3876 Power IC.	PCB
20	Simplest Ever Bridge Adapter	Use this simple method, and avoid external circuits
21	Stereo Width Controllers	2 to choose from. Expand or contract the stereo sound stage
22	Simple Audio Oscillator	For use with the millivoltmeter, for testing amps and speakers
23	Power Amp Clipping Indicator	A fast and accurate indicator to show an amp is clipping
24	Hi-Fi Headphone Amplifier	Contributed by a reader, this is a very nice circuit
25	Phono Preamps For All	Various circuits for moving coil and moving magnet pickups
26	Digital Delay Unit	Digital delay  (Note - The delay IC no longer available)
27	100 Watt Guitar Amp (Mk II)	The new and improved version of the original Project 27 guitar amp (now 27b).	PCB
27b	100 Watt Guitar Amplifier	The original of the unit above. Retained for posterity, and has speaker box details
28	Parametric / Sub-Woofer Equaliser	A simplified version, which performs surprisingly well
29	Tremolo Unit	A versatile guitar effect.  This is a simple circuit that gives very good results
30	Stage and Recording Mixer	Able to be built in modular form, allowing as many (or few)  channels as desired.
31	Full Featured Transistor Tester	Just the thing to check the transistors for any project
32	Car Audio Preamp + Artificial Earth	Especially for car audio installations, can be used for any single supply system
33	Loudspeaker Protection and Muting	Protect speakers from turn-on and turn-off transients and amplifier faults	PCB
34	Guitar Spring Reverb Unit	A high performance spring reverb unit for guitar amps
35	Direct Injection (DI) Box	An essential companion for the mixer for stage or recording work
36	Death Of Zen (DoZ)	An ultra simple, high performance Class-A power amp. Revision-A boards now shipping	PCB
37	Death of Zen Preamp	"Minimalist" preamp, designed to suit the DoZ (or any other) power amplifier	PCB
37A	Death of Zen Preamp	Updated "minimalist" preamp, designed to suit the DoZ (or any other) power amplifier	PCB
38	Signal Detecting Auto Power-On Unit	For equipment to be turned on with the main amp.  Detects signal and applies power.
39	Soft Start Circuit	Designed for (large) toroidal transformers, limit the inrush current to a sensible value.	PCB
3A	60-100W Hi-Fi Power Amp	100W into 4 or 8 ohms.  Has excellent performance, and is easy to build.	PCB
40	Load Sensing Auto Switch	Apply power to the system by turning on one item. Superseded by Project 79.
41	Opamp Design + Test Board	Quickly assemble an opamp circuit for testing.  Very easy and intuitive to use
42	Thermo-Fan For Amp Cooling	Use a 12V computer fan to cool your amp.  Uses diode temperature sensor
43	Ultra Simple Split DC Supply	When you need a +/- supply, and only have a DC adapter
44	Dual +/-25V Lab Supply	Up to 800mA (typical) output current at +/-25V.
45	Simple Bass Guitar Compressor	An ultra simple compressor, ideally suited for bass guitar.
46	Thermal Shutdown/ Protection	Add this circuit to either turn the amp off or activate a cooling fan if it overheats
47	Vox AC30 Simulator	This project has been withdrawn at the author's request
48	Sub Woofer Processor	Designed to operate a sub-woofer driver below its resonant frequency.
48A	Sub Woofer Processor (Rev-A)	New version of the sub-woofer driver has far greater flexibility.	PCB
49	Guitar Vibrato Unit	A reasonably simple circuit, with results similar to the Vox AC30 guitar amp
50	Mic Circuit Tester	Small oscillator to check mic & line circuits during sound setup
51	Balanced Line Drivers	Use these to eliminate hum for long signal leads
52	Distortion Analyser	A simple distortion meter you can use with an oscilloscope or millivoltmeter
53	Output Power Limiter	Just the thing if you want to limit amplifier power to something "sensible"
54	Low Power FM Transmitter	Useful to retransmit the hi-fi to another FM receiver nearby, or as a wireless mic
55	PPM and VU Meter	A versatile and useful VU meter circuit, can also operate as a Peak Program Meter
56	Variable Impedance	Modify the output impedance of an amplifier with this simple circuit
57	SIM - The Simple Version	The smallest variation in amplifier performance is shown with this simple circuit
58	Speaker Measurement Set	Based on work done by Siegfried Linkwitz (reproduced with his permission)
59	Self Oscillating Amplifier	Allows you to make a power amp oscillate at a defined frequency for testing
60	LED VU Meter	Standard LED VU meter, includes simple rectifier circuit for full wave detection	PCB
61	55W Hi-Fi Power Amplifier	A design from a fellow Australian. (Full details unavailable)
62	LX-800 Lighting Controller	Light is always needed for theatre and live music, and this is just the ticket
63	Multiple Feedback Bandpass Filter	This is the basis of an expandable equaliser and analyser or vocoder
64	Instrument Graphic Equaliser	Designed especially as a guitar / bass equaliser, this unit is expandable
65	Strobe Light	Designed as a companion to the LX800, can also be used by itself
66	Low Noise Balanced Mic Preamp	A discrete front end makes this balanced microphone preamp very quiet	PCB
67	Fast Audio Peak Limiter	This peak limiter is simple and very effective.  Uses discrete FET gain control
68	300W Subwoofer Amplifier	This amp is designed especially for subwoofers	PCB
69	Switchmode Car Power Supply	Low power +/-12V supply for car preamps and equalisers (etc)
70	DoZ Headphone Amplifier	The DoZ is ideally suited to headphone use. Revision-A boards now shipping	PCB
71	Linkwitz Transform Circuit	The Linkwitz Transform circuit - an equaliser to provide extended bass response	PCB
72	20W/Ch  Stereo IC amplifier	Based on the versatile LM1875 from National Semiconductor	PCB
73	Hi-Fi PC Sound System	You have never heard your MP3 collection, CD or games sound so good	PCB
74	Simple RF Probe	Indispensable for any RF work.  Uses just 4 passive components
75	Constant Q Graphic Equaliser	Constant Q design. Can be made using as many or as few sections as needed.
76	Opamp Based Power Amplifier	This is a contributed project, and has some interest as a learning exercise
77	13.8V Power Supply / Charger	A supply for testing and working on car amplifiers - up to about 500 Amps!
78	3-Way 12dB/ Octave Crossover	Contributed project, simple 12dB/ Octave crossover network.
79	Current Sense Auto Power Switch	A current sensing switch turns on multiple devices from one master
80	Reverse RIAA Equaliser	Test phono preamps for correct equalisation, or convert unused phono inputs.
81	12dB/Octave 2-Way Xover	Linkwitz-Riley alignment and phase coherent (uses the P09 Rev-B PCB)	PCB
82	Loudspeaker Test Box	Quickly and accurately determine the optimal impedance correction network
83	MOSFET Follower Power Amplifier	Another contributed project that may be of great interest
84	Subwoofer Graphic Equaliser	This is a constant Q design, eight 1/3 octave bands covering 20Hz to 100Hz.	PCB
85	Simple S/PDIF DAC	Quite possibly the simplest possible S/PDIF receiver and DAC you will ever find
86	Miniature Audio Oscillator	The Miniosc - low distortion battery powered audio oscillator
87	Balanced Transmitter / Receiver	Updated and upmarket versions of the Project 51 balanced circuits	PCB
88	High Quality Audio Preamp	An audiophile quality preamp, with full switching and programmable gain	PCB
89	Switchmode Power Amp Supply	A high power (350W typical) car power amplifier supply
90	Dimmer Control Polarity changer	Convert old dimmer units using a 0 to -10V control signal
91	78 RPM and RIAA Phono Equaliser	Multi Standard 78 RPM and RIAA Phono Equaliser handles all "standards"	PCB
92	Guitar and Bass Sustain	A simple, low distortion limiter for musical instruments
93	Recording and Measurement Microphone	A simple selection of projects for making your own microphones	PCB
94	Universal Preamp/ Mixer	A small and versatile mixer and preamp, suitable for many uses. 27 Jun 09	PCB
94A	Universal Preamp/ Mixer	Alternative wiring for the versatile mixer/ preamp, suitable for many uses. 27 Jun 09	PCB
95	Low Power -Ve Supply	Low power -ve supply for car audio preamps and crossovers
96	48V Phantom Supply	Low noise 48V regulator and phantom mic supply circuits.	PCB
97	Hi-Fi Preamp	Another preamp, but this one has tone controls, and all pots are PCB mounted	PCB
98	Battery Charger	Automatic Charger for Battery Operated Hi-Fi Preamps
99	Subsonic/ Rumble Filter	A 36dB/octave 17 Hz high pass filter to remove ultra low frequencies Rev-B PCB	PCB
100	Headphone Adaptor	A simple adaptor to provide a headphone output to an existing power amplifier
101	MOSFET Power Amp	200W MOSFET Hi-Fi Power amplifier	PCB
102	Simple Pre-Regulator	Use this to adapt P05 to a power amp supply for your preamp
103	Subwoofer Phase Control	A standard phase control for use with subwoofers.
104	Preamp/ Crossover Muting Circuit	Muting circuit suitable for all line-level applications.
105	DIY Electrostatic Loudspeaker	An ESL using ready made panels available exclusively from ESP. Part 1
105 -2	DIY Electrostatic Loudspeaker	ESL cabinet details. Part 2
105 -3	DIY Electrostatic Loudspeaker	ESL Transformers and Power Amplifier Details. Part 3
106	hFE Tester	An hFE tester with switched collector currents for the Device Under Test
107	Polarity Reversal Switch	Switch the absolute polarity (180° phase shift) of signals with this simple circuit
108	Switchmode PSU Protection	This contributed circuit can help prevent failure of your switching power supply.
109	Portable Headphone Amp	Another contributed circuit, this is a complete portable headphone amp that features crossfeed.
110	IR Remote Control	Volume and mute are provided by this simple but functional circuit. Suitable for all preamps.	PCB
111	PIC Speaker Protection	This doesn't replace P33, but it is possibly the ultimate speaker protection.
112	Dummy Head Recording Microphone	Surprise yourself with one of the most realistic recording processes known.	PCB
113	Hi-Fi Headphone Amp	Yet another headphone amplifier, but this one will have PCBs available soon.	PCB
114	PWM Power Amplifier	Based on the ColdAmp BP4078 400W module, Class-D is here. Definitely worth looking at!	PCB
115	GainClone Amplifier	Complete GainClone amplifier, including full chassis details (2 part article)	PCB
116	PWM Subwoofer Amplifier	Using a ColdAmp BP4078 module, this article has complete construction details	PCB
117	1.5kW Power Amplifier	Just the thing for those for whom no amount of power is enough
118	PC Power Switch	Simplest ever PC switching unit - turn on peripherals with the PC
119	Signature Analyser	A component signature analyser that allows in-circuit parts tests
120	Crowbar Speaker Protection	The final answer to speaker protection. Comes with many cautions and warnings!
121	Reading Inductance	Use your DC voltmeter or frequency counter to measure crossover coils.
122	Ultra-Simple Mic Preamp	A single low cost IC and tiny PCB make a great utility microphone preamp.	PCB
ABX	ABX Comparator	Full ABX testing unit, without microcontrollers or a PC
X	A-B Switch Box	Can you really hear the difference between amps or cables?

Although I am happy to provide assistance to prospective builders, I cannot (and will not) be drawn into prolonged e-mail exchanges if the project does not work as expected. I can say with complete confidence that all projects presented will work if properly constructed according to the published design. This is not to say that no help will be available - I will always help where I can.

It is inevitable that in some cases (due to component tolerances, for example), a project may require a different value resistor, capacitor (or whatever) to correct for an unexpected variation. Since I cannot control or predict the quality of components sourced by readers, nor the standard of workmanship in assembly, it is not possible to allow for every contingency.

Please do not attempt the construction of any project which you do not fully understand, or if you do not feel completely confident that you can build the project without further assistance. Do not expect me to be able to diagnose an obscure fault remotely, and especially if the project has been modified in any way whatsoever.

Under no circumstances should any reader construct any mains operated equipment unless absolutely sure of his/her abilities in this area. The author takes no responsibility for any injury or death resulting from, whether directly or indirectly, the reader's inability to appreciate the hazards of household mains voltages or other voltages as may be present within the circuitry of a project. Please read the disclaimer now if you have not done so already. Also read the warning on the main projects page. This is important!