AMP51Simple
by Martin Clausen (mc AT rotgradpsi DOT de)
Very simple high quality Audio Amp Controller
Table of contents:
- Volume control in 255 steps, each 0.5 dB, noise free transitions
- Balance with +/- 64 steps
- Volume and balance control via PGA2310 (adjust voltages for CS3310 or PGA2311)
- Input selector with 0 to 8 source inputs, unused outputs can be used as general purpose outputs to switch e.g. filters (I version)
- Optional volume indicator with LEDs (stripe and spot versions with different numbers of LED available)
- Mute
- Output for power switch
- 0,0004% TDH+N at 1KHz
- Control with RC5 type remote only, address selectable via dip switches
- Start volume range selectable via dip switches
- LEDs for balance, power and mute
- Low cost, standard parts, low part count
- Freeware
The device is controlled via remote only. Volume and balance are changed by the corresponding up/down keys on the remote. The I version uses the wind/rewind keys to change balance, too. In contrast the version without an input selector allows to change balance additionally with the channel up/down keys. If blance is not neutral, the balance LED is lid.
The I version uses the channel up/down keys as well as the numbered keypad for selecting the input. Outputs of the 74HC595, which are not used for the input selector can be switched on and off by pressing the corresponding number on the keypad.
In the following text a closed switches corresponds to a one, an open switch to a zero respectively.
Settings for IR-Remote Control
The device needs to know, which commands it should follow. According to the RC5 standard it is a preamplifier, but depending on the remote control you might want to give it the address of another device class. For example if you leave all adress switches open, it is the TV set address:
Address
MSB-LSB | Device
|
|---|
| 00000 | TV set
|
| 01000 | preamplifier
|
| 01001 | receiver / tuner
|
Settings for Start Volume
The device needs to start with a usefull volume setting after power-up. This value can not be programmed into the device, since it depence on the total amplification of the audio sytem and the needs of the user. I would recommend to start with 011 or 100 and go then for lower or higher settings as required.
Setting
MSB-LSB | Start Volume
|
|---|
| 000 | -95.5 dB
|
| 001 | -79.5 dB
|
| 010 | -63.5 dB
|
| 011 | -47.5 dB
|
| 100 | -31.5 dB
|
| 101 | -15.5 dB
|
| 110 | 0.5 dB
|
| 111 | 16.5 dB
|
PCB Design
Note that the PGA is connected to the rest of the circuit only by a few wires, so it is easy to make a seperate digital pcb to integrate into the front of the case, while the PGA has its own pcb in the back. Place the decoupling capacitors as close as possible to the devices.
- Semiconductors:
- 1 AT89C1052 or AT89C2051, programmed
- 1 NE5532A
- 1 PGA2310 (adjust voltage to +/- 5V for CS3310 or PGA2311)
- 1 SFH5110-36
- 1 78L05
- 1 78L15
- 1 79L15
- 8 1N 4001
- 3 LEDs, low current
Additional for input selector:
- 1 ULN2003
- 1 74HC595
Additional for volume indicator:
- x LEDs, low current
- X 74HC595
- X 74HC154
- X 74HC04
Capacitor:
- 2 33pF cer
- 13 100nF cer
- 1 1µF / 16V
- 2 3,3µF, foil
- 10 10µF / 25V
- 3 220µF / 25V
Additional for input selector:
- 2 100nF cer
Additional for volume indicator:
- X 100nF cer
Resistors:
- 1 10
- 1 100
- 3 1k
- 4 47k
Additional for volume indicator:
- 1 47k
- X 1k
Other Parts:
- 1 DIP switch
- 1 12MHz Quartz
- 1 transformer 9V / 3,6VA
- 1 transformer 2*15V / 1,5VA
Additional for input selector:
- 6 reed relais for 5V with two contacts each
- Volume Controller with balance, power, mute
- Volume Controller with balance, input selector, power, mute
- complete example schematic with 6 inputs and 2 general purpose outputs, 16 LED master volume indicator, and input indicator (by Sebastion Gill)
- amp51simplei4.hex program file for AT89C2051 V2 (for 4 inputs sources and 4 general purpose outputs)
- amp51simplei2.hex program file for AT89C2051 V2 (for 6 inputs sources and 2 general purpose outputs)
- amp51simpleisignalflow.gif signal flow diagram for AMP51SimpleI
- schematic digital part
- schematic anlog part, with PGA2310 (TI) and input source selector
- 0 to 8 inputs sources with 8 to 0 general purpose outputs are possible as well, please ask
- for volume indicator type A, C and E
- volume indicator E can be modified to support 1 to 256 LEDs, please ask
- Ask me for a chip, if you do not have a programmer.
- Volume indicator schematics
- volume indicator A, 32 LEDs for each left and right (spot type)
- volume indicator B, 32 LEDs for master volume (spot type)
- volume indicator C, 16 LEDs for each left and right (spot type)
- volume indicator D, 16 LEDs for master volume (spot type)
- volume indicator E, 16 LEDs for master volume (stripe type)
- spot type indicators have one LED on a time, the position of the LED correspondes to the volume
- stripe type indicators have a number of LEDs on corresponding to the volume
- The power consumption of the spot type is low compared to the stripe type, but the indicator is harder to read from the distance and may look less impressive.
- Volume indicators are not required for the function of the volume controller.
- power supply, with PGA2310 (TI)
- On the pages of the reference designs block schematics and photos of different constructions.
The part description in schematics is read as follows:
part type + value in exponential form + package description + subpart number in package
for example: C1040805,1 means Capacitor, 100nF, package SMD 0805, first subpart in package
Disclaimer: No warranty at all!
Copyright by Martin Clausen, Germany.
Contact the author: mc AT rotgradpsi DOT de
Impressum
