Auna AV2-CD508BT Hi Fi Amplifier to High End Preamplifier AUX bluetooth

How to made an economic High End Preamplifier.

My Auna CD508 project: from Hi Fi power amplifier to High End Preamplifier with Phono MM and MC.
The original amplifier has a switching power supply, the input selector is made by CD4052 and power amplifier is made by Texas Instruments AB class IC, LM1875 in bridge connection. The power rails voltage are +16/0/-16 Vdc and it as some features like tone control, BT connection balance, remote control , motorized volume knob, output relay, 3 inputs(4 with BT) , a tape recording output and a headphones out.
Estimated  power output on 8ohm should be around 50W/CH.

Amplifier Auna AV2-CD508BT before mod

I dismounted the power amplifier section and I made a substitution with my Espritaudio Preamplifier modules: ESPRE

Preamplifier Auna AV2-CD508BT after mod

Bridge connection of LM1875

Repair of KUSTOM KBA 100 Bass Guitar Amplifier TDA7293 100W

Kustom KBA 100 fix.
Transformer and TDA7293 IC Audio Power Amplifier  Replacement.

My PCB GY50 Evolution Power Hybrid Amplifier

Here my new circuit boards about Aloia's amplifier GY50.

Next Power Amplifier based on Sony Esprit Series Using No Negative Feedback Architecture

I'm traying to make an amplifier following example of Sony TA-N902 Esprit Sere, the last aftre TA-N900 mono and TA-N901 stereo.
Sony's Esprit  amplifier all haven't Negative Feedback, they had a Voltage Amplifier Stage made by discrete components, which has his proprer feedback and a current stage located out the loop, This architecture decrease the TIM distortion. To minimize THD Sony used his own  patent concerning non-switching power devices, the stage also remain a AB class but  results similar to pure class A.

3D of the  Voltage Amplifiere Stage

Some amplifier are been used as example for schematic or as  components donor.

Power supply is from a PLPS from an old TA-F80,electronic components for VAS are coming from a TA-F500, the chassis is given by a broken Behringer A500.
Other components are new and PCB are made by myself.

Current Amplifier 3D

I used a lot of SMD components, all with 1206 dimension

Soon I'll show the complete work

My personal 18W Marshall Style Guitar Tube Amplifier is Working!!!

EspritAudio EL84 Guitar Tube Amplifier Protototype

First Classic Guitar  vacuum tube amplifier from ESPRITAUDIO

First prototipe on PCB is done!!!

DIY DC/DC Dual Boost regulated Power Supply for High Voltage Tube VAS

In relation to DIY Hybrid amplifer the first step is to obtain the High Voltage for tube's anode supply and the low voltage for heaters.

Sometimes, if not always, fora a 100W amplifier you have a double sec 150-300VA  36-0-36Vac power transformer only.
Using this board you can adjust the  needed voltage for tube stage starting from your transformer.
Without use any voltage doubler and linear regulators.

The Following image shows how the Double Boost works.

From unregulated  +55/0/-55Vdc the circuit gives at his output the needed voltage, able to supply the anode current for a tube stage.

For example you can obtain +90/0/-90Vdc and 6.3Vdc for the heaters..

Luxman LV-105 Style Hybrid Amplifier 100W Simulated Project 6DJ8 (ECC88) Hitachi Mosfet 2SK1058 2SJ162

Similar to basic schematic of Luxman LV-103 / LV-105 , this project is made by only 3 simple stages: 

1. Input stage: is a BJT cascode(Q8,Q9) with current sink(Q11)
2. VAS stage: is a 6DJ8 (ECC88) SRPP (X7,X8) buffered by a emitter follower BJT (Q10) with MOSFET current sink (M9)
3. Output stage: is a B class Mosfet Push Pull  with two couple of 2SK1058 / 2SJ162  Hitachi 

100W Schematic 

Simulated FR

Simulated Distortion 0.041% at 32Vpp out

Sony TA-F555ES Amplifier 100W

Sony TA F555ES Amplifier
ACT :  Audio Current Transfer
Shunt Regulated Power Supply for Signal Section
Big BJT Discrete  Phono, EQ, Board including MC and MM Load Selector
Elna for Audio Capacitors
Sanken Power BJT: 2SC2922 2SA1216

Sony TA-F555ES front view

Regulated Shunt Power Supply Regulator

Audio Current Transfer...

Sony Power

Attenuator

EQ Board,  Discrete BJT Phono stage including MC cartridge amplifier

Cartridge Load Selector

Sony TA-F555ES inside View