AMP51 Tables and Hints

Encoder and Buttons

The following button pairs can be replaced by a rotational encoder: TincV/TdecV and TincF/TdecF. I recommend to replace only TincV and TdecV by an rotational encoder to save costs.
An encoder has three pins: A, B and common. Connect A to inc, B to dec and common to ground.

AMP51RTC only

Since the same software is used independend of the usage of encoder or buttons, the encoder must have dents and both contacts must be open, when it is left untouched. I recommend Bourns ECW1JB24AC24.

AMP51Pure only

The software of the AMP51Pure requires an encoder for TincV and TdecV. This encoder is not required to have dents.

Selecting Passive Components

I recommend to use only 25V or higher rated electrolyte capacitors. For higher quality audio device electrolyte capacitors within the signal chain should be exchanged for polysterene capacitors, but they are more expensive and bigger. All smaller capacitors in the signal chain should be polysterene types (e.g. Wima MKS-2 or MKS-4). All decoupling capacitors should be ceramic types (e.g. Z5U ceramic).

Trimming of the RTC crystal

To obtain a high accuracy for the clock it is neccessary to use a trimmer for the capacitor between pin 1 of the PCF8583 and ground. Its value range should range from 5pF to 25pF. You can adjust it by comparing the clock of the AMP51 with a high quality clock: If the AMP51 is to fast, increase the capacitance. If the AMP51 is to slow, decrease the capacitance.
If you have a high quality frequency meter, you can adjust the trimmer by tuning it, until at pin 7 of the PCF8583 a 1.00000 Hz signal appears.

Joint Power Supply for Amp and Preamp

If the power amp runs at a voltage lower than +/- 20V DC, this power supply can be used for the preamp and the microcontroller circuit. However, than some resistors have than to be adjusted, since in the schematics only the values for the seperate 12V DC power supply are shown.
Depending on the supply voltage the following values for the resitor between Ub and TL7705A have to be used. In the scheamtics the value for 12V (22K) is given.

Ub AC	Ub DC	Ub Reset	R
+/- 15V	+/-20,5V	16,4V	47k
9V	11,3V	10,1V	22k
8V	9,9V	9,1V	18k

Depending on the supply voltage the following values for the resitor between the BC547 transistor and the LCD backlight have to be used. In the scheamtics the value for 12V (68 ohms) is given.

Ub AC	Ub DC	R	Pres
+/- 15V	+/-20,5V	150	1500mW
9V	11,3V	68	750mW
8V	9,9V	47	500mW

Supply current of some relevant parts

Part	manufacturer	I max / mA	I typ / mA
AT89C51@12MHz	Atmel	20
AT89C2051@12MHz	Atmel	15
LCD	Sharp	2,2	1,6
LCD backlight with 68 Ohm resistor according to schematic at 12V			110
single low current LED		3
78L0X	ST	6
780X	ST	6
CS3310	Crystal	8 analog 0,8 digital
PGA2310	TI	10 analog 1,5 digital
TDA7318	ST	11	8
NE5532	TI	16	8
TL7705A	ST	3,3	1,8
PCF8583	Philips	0,2
SFH5110-36	Siemens	5	1,3
reed relais 2 contacts 5V type	Meder		10
relais 1 contact 16A/230V 12V type	Finder		33
relais 2 contacts 8A/230V 12V type	Finder		55

These values lead to the following power supply designs:

AMP51 Type	Voltage	Parts for Power Supply
AMP2051	+12V unstabilized	transformer 9V / min. 2,6VA, BC40C800, 470µF/16V
AMP51RTC	+12V unstabilized	transformer 9V / min. 3,6VA, BC40C800, 1000µF/16V
AMP51pure with LCD, CS3310		transformer 9V / min. 3,6VA
AMP51pure with LCD, PGA2310		transformer 9V / min. 3,6VA transformer 2*15V / min. 1,5VA

I recommend to use an power line filter.

Disclaimer: No warranty at all!
Copyright by Martin Clausen, Germany.
Contact the author: mc AT rotgradpsi DOT de
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