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

Cassette Deck Revox B710 mkI vs TEAC V9000 Esoteric vs AIWA AD-F660a

Cassette Deck World 

    80's Example

"Professional"

Revox B710 mkI 

4 Motors DD

ReVox B710 Microcontrolled Cassette Deck

"Audiophile"

TEAC V9000 Esoteric

All AudioGrade Capacitors

TEAC V9000 Esoteric

"Consumer"

AIWA AD-F660

3 Heads, Dual Capstan, Dolby HX PRo, 

ADMS, a lot of Wires....

AIWA AD-F660

AIWA "Spaghetti Made"

Sony DTC-1000ES Digital Audio Tape DAT with Sony CX20018 ADC and Philips TDA1541A DAC inside

Sony DTC-1000ES DAT Player

Not Working, but very beautifull Player!
Elna Audiograde Capacitors.
Philips TDA1541A - SAA7220P/B Chipset for DAC
Sony CX20018 for ADC

Sony CX20018 ADC 

Philips TDA1541A

To restore and repair.....

Not Working Cassette Deck AIWA AD F660 Repair

Not Working Cassette Deck AIWA Repair.

3 heads, 2 motors (1 for capstains, 1 for reels)
Closed loop dual cpastan, Dolby B, C HX Pro, Bias adjustable. 
ADMS Automatic DeMagnetizing System

Trouble: In Play Mode Capstan Correctly Work but tape go out, Reels don't go

Repair: Not mechanical problem, but electrical, in Power Supply zone; a lot of defective soldering joint!

AIWA AD-F660 Not Working

AIWA DX R&P Heads , Dual Capstan

AIWA Mechanical Detail Dual Capstan Big Motor

Bottom Layer, Power Supply Zone

Defekt

Teac V9000 Esoteric Top Cassette Deck

All Audio Grade Capacitors in electronic circuits

Teac V9000 Esoteric, Cassette Deck, 3 Heads, Closed Loop Dual Capstan
Only Audio Grade Capacitors used.....

Erase, Rec & Play Heads in die cast metal base

Beautifull R&P Heads in one block

Play

Pretty look

Calibration

CrO2 Calibration

REVOX B710 Professional Cassette Deck

Deck Inside......

Inside view REVOX B710: 4 motors, 3 heads, Dolby B

A Lot of Leds in Meters

Gorgeous, Red Leds, Peak Reading Meter REVOX B710

B710 & B226

Revox Family Pic