Power amplifier 2x500W for home use

[Vermes]

It is a construction of power amplifier 2x500W for home use. The amplifier does not have correction nor level adjustment. It can be connected to different mixers (symmetric inputs XLR – Canon for balanced signal). The amplifier can cooperate with different speakers, both 4 and 8ohm. Outputs are compatible with standard outputs of the speakers, for home use and professional ones as well. Power of the amplifier should be enough for a small party. The output power is 500W (4ohm) for a channel.



Housing:
Housing was made of aluminum, because it is an easy material to cut, sand, drill and thread at home. The housing consists of:

• front and rear panel (2 pieces) – 3mm thick aluminum (104x460mm)
• bottom and top cover (2 pieces) – 2mm thick aluminum (300x320mm)
• power supply chassis (1 piece) – 5mm thick aluminum (300x200mm)
• connecting elements (4 pieces) – full profile (rod), square cross-section: 10x10mm (L=290mm)
• left and right heat sink (2 pieces) – ribbed profile: 84x300x100mm

It is important to provide the right rigidity of the housing. It is necessary due to the weight of the mains transformer. The toroid transformer weighs more than 9kg. It is good to perform an additional chassis for the block of power supply.



Mains transformer, two symmetric systems of power supplies and soft start for toroid transformer were placed on a piece of 5mm aluminum sheet. Solid base of the mains transformer is based on aluminum profiles (rods with a square cross-section) screwed with M3 to the front and rear panel and to the bottom cover. Power amplifier systems were mounted directly to the aluminum ribbed profiles, which are also the mechanical connection for all the adjacent surfaces (front and rear panel, bottom and top cover).

There are only two elements on the front panel – supply switch and LED indicator.





The rear panel is equipped with signal contacts, separate for each of two channels and supply sockets. Control signal input – XLR contact (female), speaker output – a pair of lab contacts and additionally for professional speakers – speakon type contact. Mains – supply contact 230V AC of computer type (male). Disconnectable supply socket for a preamplifier also of computer type (female).

Supply:
There is a common mains transformer with separate secondary windings for each channel, so there is a complete separation between the channels.
Parameters of the mains transformer:

• power: 1200VA
• primary winding: 230V
• secondary winding I, II, III, IV: 55VAC
• secondary winding V, VI, VII, VIII: 30VAC

The power supply is divided into two sections: the main sections – for the power amplifiers and the other auxiliary – for input systems. In the main sections, there are two identical blocks of symmetric power supplies, one for each of two power amplifiers. Each of blocks is built of a rectifier bridge 35A/600V in Greatz system, four capacitors 10mF/100V (20mF for negative part of power supply and 20mF for positive) and inserts with fuses 15A/250V. Descriptions of symmetric power supplies can be found at: **broken link removed**. In the auxiliary section there are also two identical blocks, but there are stabilized power supplies, which provide stable symmetric voltage +/-15VDC for additional systems. Description of stabilized power supplies can be found here: **broken link removed**.

The system is also equipped with softstart system. It is very important when you use mains transformer of such a great power. Direct connection of the transformer to the mains results in immediate activation of overcurrent protection on the electrical system (fuse B10). Softstart is also module fom MAEL - Carton Audio. Its description can be found here:**broken link removed**.

Amplifiers:
Due to the little space in the housing, the amplifier systems should be mounted directly on the surface of heat sink.



Perfect system for that purpose is WMT-FET4 from MAEL – Carton Audio. It is a very powerful output stage of an output power exceeding the assumptions of this project. Its description can be found at: **broken link removed**. That system is supplied by symmetric voltages +/-77VDC from a power supply.




The amplifier has a delayed turning off the speaker outputs, so you do not hear unpleasant sounds during turning on and off the supply. The amplifier has a built in thermal protection – it has a contact, to which you can plug a temperature sensor.

System of the WMT-FET4 has a standard linear (non symmetric) input. It can be controlled from a household exuipment AV (such as a computer, CD player, cassette player, tuner, TV set) or a mixer (professional mixers require symmetric – balanced connection). Description of the converter system can be found at: **broken link removed**. Performing the system of converter allows you to save space inside the housing, but remember to make a hole for XLR socket on the rear panel.

Pictures:






Link to original thread - **broken link removed**