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

My PCB GY50 Evolution Power Hybrid Amplifier

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

Sony TA N902 N900 N901 Esprit Solid State Class A Amplifier Clone II Switching Dual Power Supply

DIY 
My Sony Esprit Clone Power Amplifier!

Power Boards Hetasink

Switching power supply

Sony TA N 902 Esprit Solid State Class A Amplifier Clone

Sony Esprit TA-N902 Power Amplifier:

My design about Sony's clone, power part simulation: 

Hi Fi power supply +60V 0 -60V DC

A Linear Power Supply designed for Hi Fi appliance capable of +60Vdc,-60Vdc, power diveces cuold be IRFP240 IRFP9240

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

Behringer A500 Amplifier mod Sony TA F80 PLPS Power Supply and TA F902 similar circuit

I'm working on cheap Berhinger A500 case , putting inside a Sony TA-F80 PLPS supply and  Sony TA N902 Esprit Non NFB Power Amplifer clone board ...

My new GY50 50W  Hybrid Power amplifier DIY Board 
IRFP240
2SC3281 - MJL3281
2SA1302- MJL1302

Audiograde output capacitor

"ready to run" GY50 Boards

Ampeg SVT3 Pro Tube & Mosfet Electric Bass Amplifier - Bias Adj and Repair

Custom Power Transformer suitable for My GY50 Hybrid Power Tube Amplifier 4 x 12AX7 + BJT Power Stage

Custom power Transformer  for my GY50 hybrid Amplifier clone is ready!!

Trasformatore Alimentazione Hi Fi 300VA 

Primario 230Vac

Secondari:
1 x 230Vac x anodica
2 x 67Vac x stadi finali BJT
2 x 12.6vac x filamenti 12AX7

Schermo elettrostatico primario/secondari

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..