Schematic & Wiring Diagram

This is the easy build surround sound processor circuit using the digital delay process method. This audio processor isn't applying any unique function ICs that tough to obtain parsonaly, and designed in only common purpose ICs.

The kind of this Surround Processor is producing the surround impact with processing two channels of stereo supply. The majority of those are generates the surround impact with separates reverberations from supply signal and applies any processes, after which mix it to front channels or output as rear channel.

The circuit works and contains three modules:

Separating the Reverberatins

The distinction in between each channels is separated with distinction amplifier from the op-amp. And greater frequencies inside the distinction signal are cut using the LPF.

A-D and D-A conversion

These are composed with common purpose ICs. The A-D converter is basically delta modurator that making use of a comparator plus a D type flip-flop. And it converts analog signal into digital data of one bit, 2 Msa/sec. Following passed digital delay, the bit stream is directly conversion into analog signal using the integrater.

It isn't beneficial that signal to noise ratio and distortion as this A-D, D-A converter.

Digital Delay

For the digital delay method, a DRAM chip is utilised as a FIFO memory. This circuit design demands a 64K bit DRAM, but I utilized a 256K bit DRAM discovered within the junk box. Shift register generates Read-Modify-Write cycle, read out old data and save new data in a single cycle.

And lower byte in the address counter is assined as row address with the DRAM to increment row address every single cycle, to ensure that refresh cycle is often omitted. The FIFO length is 65536 bits and 2 Msa/sec makes 33 msec of delay time.

Surround sound processor circuit source page: http://elm-chan.org/works/srp/report_e.html

Thi circuit is very simple with only one transistor. No need additional active components, but if you want to hear the sound louder, just build another amplifier circuit... :)

Part designator	Part description
C1a,C1b	10 pf, 50 v, ceramic disc capacitor
C2	22 pf, 50 v, ceramic disc capacitor
C3	RF tuning capacitor
C4	330 pf, 50 v, ceramic disc capacitor
C5,C8	0.001 uf, 50 v, ceramic disc capacitor
C6	0.22 uf, 50 v, film capacitor
C7	0.0047 uf, 50 v, ceramic disc capacitor
C9	22 uf, 16 v, electrolytic capacitor
D1	TL431AIZ voltage control Zener (shunt regulator)
EPH1	High impedance earphone
L2	22 uh RF choke
Q1	2N4416A JFET transistor
R1	470K, 1/4 w, resistor
R2, R3	1K, 1/4 w, resistor
R4	10K, 1/4 w, resistor
R5	1M, 1/4 w, resistor
R6	100 ohm, 1/4 w, resistor
S1	Small SPST switch
screws for C3	screws for mounting C3 (2 needed)
nylon screw	#4 nylon screw used for tuning C3
battery connector	mini battery snap

More instruction how to build this circuit, visit this page

This is a small variable power supply delivers adjustable output voltage of 1.3v-12v. The current output determined by R3. With current setting (see part list), it will deliver current output about 1A.



Detail Specification:
Output (approximate values):

Vmin = (R4 + R5) / (R5*1.3)
Vmax = (7.15 / R5) * (R4 + R5)
Imax = 0.65/R3
Max. Power on R3: 0.42/R3
Min. Input DC Voltage (pin 12 to pin 7): Vmax + 5

Parts List
B1 = 40V/2.5A
R1 = 1k ohm
R2 = Potensiometer 5k ohm
R3 = 0.56R/2W
R4 = 3.3k ohm
R5 = 4.7k ohm
C1 = 2200uF (3300uF even better)
C2 = 4.7uF
C3 = 100nF
C4 = 1nF
C5 = 330nF
C6 = 100uF
D1 = Green LED
D2 = 1N4003
F1 = 0.2A F
F2 = 2A M
IC1 = LM723 (in a DIL14 plastic package)
S1 = 250V/1A
T1 = 2N3055 on a heatsink 5K/W
TR1 = 220V/17V/1.5

R2 sets the output voltage. The maximum current is decided by the value of R3: the over-current protection circuitry inside the LM723 senses the voltage across R3 and starts shutting the output stage off as soon as this voltage approaches 0.65 V. This way the current through R3 can never exceed 0.65/R3, even if the output is shorted.

C3 and C4, both ceramic, must be placed as close as possible to the integrated circuit, because the LM723 can be prone to unwanted oscillations. It is not an overkill to solder them directly (and very carefully) to the pins of the IC. All other connections should also be kept short.

The LM723 works with input DC voltages from 9.5 to 40 V and the IC itself can source some 150 mA if the output voltage is not more than 6-7 V below the input. When an external pass transistor is used (in the usual emitter-follower mode), the base-emitter junction of T1 represents a significant resistance and the integrated circuit's output stage is relatively lightly loaded. All the current drawn by the load passes through T1 and it dissipates an amount of power that is directly proportional to the current and the difference between the input and the output DC voltage.

This schematic diagram is a light-operated, remote-controlled solidstate switch circuit to handle lamp. While in darkness, the resistance of Light Dependent Resistor (LDR) is extremely hight, it shoots up to megohm range. As a result, the triac isn't going to have gate drive and therefore it doesn't conduct.

When LDR is lighted by way of a torch-light beam, the level of resistance of LDR immediately reduces (under 10Kohm). This leads the triac to conduct and turn on the lamp. Light received from your lamp (normal lamp in the room, not from the torch) will keep LDR’s resistance low. So, the lamp stays continually "on". When the lamp is ‘on’, it could be turned "off’ once again by disturbing the light falling on LDR, by either waving hand in front of it or by disturbing power source for the circuit for just a moment.

RFC applied right here could be built by winding about 15 turns of 18 SWG wire over an insulated ferrite rod.
Circuit title: 220V Light-Operated On/Off Switch. This kind of circuit also can be modified to make a alarm circuit for security purpose.

Here the very simple and easy build gold detector circuit. The circuit capable to sense gold or metal or coins from a distance of about 20cm, depending on the size of the object to detect.

The circuit oscillates at about 140kHz and a harmonic of this frequency is detected by an AM radio. You can simply tune the radio receiver until a squeal is detected.

When the search coil is placed near a metal object, the frequency of the circuit will change and this will be heard from the speaker of AM radio.

Below image is the construction of the circuit, you will see that the radio is placed on the hand stick of the complete detector.

This is a 2-station simple intercom circuit build based on transistors part and using common 8R mini speakers. The speaker works as microphone and generate sound, so there is no need microphone for this intercom. The "press-to-talk" switches should have a spring-return so the intercom can never be left ON, push on switch can be used for this kind of task.



The secret to preventing instability (motor-boating) with a high gain circuit like this is to power the speaker from a separate power supply! You can connect an extra station (or two extra stations) to this circuit design.

Build the circuit into two separated boxes (for 2 stations). On each box should be use 2 ports for external power supply port (if you use external power supply, not battery) and connection port to other stations. Create some holes for speaker push on switch.