PT05 DIY Preamplifier.

17 Jan. 2012 by Thanaporn, 140 views.

PT05 Hifi DIY Preamplifier.
PT05 is the upgraded version of PT03 preamplifier.
The design is very similar.
- Designed to be used the independent power-supply circuit for left and right.
- Cascode circuit for the differential amplifier stage in order to reduce distortion and increase the linearity.
- Cancel the DC servo circuit. I have found that without DC servo, brings the better sound quality and more natural.
-2.1 stages voltage regulation power supply.

PT05 DIY preamplifier schematic
The overall design.
It is also 2-stage amplifier. The differential amplifier stage is a fully complementary transistor-based circuit and of course, it runs in class A.
The next stage is working with the first stage as well it is a fully-complementary. The cascode circuit is also in this place to improve linearity of the amplifiers. Cascode circuit requires a constant reference voltage biasing
to make a cascode transistor on. We chose to use a transistor array as a voltage reference. Because it requires less current compared to the use of zener diode, diode and LED, and of course, it has lower noise. The overall voltage gain is set to 12 times.

The use of electronic devices.
Good electronic devices are used in this preamplifier.
- BC550C/BC560C low noise transistors.
- Elna electrolyte capacitors.
- Dale resistors for the most important part.
- Wima film capacitors.
- Fast switching with soft off recitifier diodes.
- Nichicon electrolyte capacitors for DC filter.
DIY Preamplifier

Power supply.
What are the power supply of my PT05 DIY preamplifier. It is a linear power supply with a voltage regulation circuit includes a rectifier and regulator IC amounting 2 pieces per side.
Therefore, it is totally 4 pieces for positive and negative side. In fact, you will see actually 6 regulators, but I canceled 2 of them.
It was called a 2.1 voltage regulation. 2 is 2 stages voltage regulation by 2 regulator ICs. 0.1 is a shunt voltage regulator. So I called it a 2.1 voltage regulation.

Listen PT05 DIY preamplifier.
Overall, It would polite sound. The deep bass is slightly less than the PT03. But it gives the better musical. Midrange and treble detailed are done very well.
It is sweet to hear. Detail and identifying between pieces of music do better.
Thanks for reading.