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

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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..

DIY Do It Yourself KIT Headphones Hibryd 0fb Class A Tube Amplifier Using Boost Coverter Power Supply DC DC Coverter output 190Vdc 6.3Vdc starting from 12-24Vdc

Zero Feedback 100mW Hi Fi Tube - BJT Amplifer using Hi Voltage Power Supply by DC DC Boost Converter.

Boost and Buck Board provide to give:

VAS Tube Supply: 190Vdc
Curret Buffer Amplifer Supply: 30Vdc
Heater voltage 6.3Vdc by Step Down converter

All voltages obtained starting from 12-24Vdc power supply, as Desktop power supply or Battery

DC DC Step Up and Step Down Board

High End Tube Headphones Amplifier - Goodnight Project

One implementation of my 

"Goodnight "

Tube Headphones Amplifer

"Operazione Goodnight" Tube & BJT Hybrid Class A Headphones Amplifier Project Schematics Layers SMPS Power Supply

My Goodnight Tube Headphone Project Schematics  

SMPS Power Supply 

Triode Amplifier Section ECC82 ( 12AU7)

Voltage Tube Amplifier Stage Schematic

Class A BJT Emitter Follower Current Buffer 

2SC2238 2SA968 

2SC1815 2SA1015

LM334Z

Current Buffer Stage Schematic

Top Layer and Components Amplifier Section

Switching Power Supply Based on Texas Booster Driver IC LM3478 and Buck IC LM22673.

Vin=12Vdc

Vout1=200Vdc

Vout2=30Vdc

Vout3=6.3Vdc

 Top Layer:

SMPS Buck-Boost

"Operazione Goodnight" Headphones Amplfier Using Vacuum Tube ECC82 ( 12AU7)

My  Project about a Vacuum Tube Headphones Amplifer for my Philips Fidelio X1:

My Tube Amplifier and My Headphones Philips

My Headphone Tube Amplifier 

Tube used for amplifier is a ECC82/12AU7 followed by a discrete Class A BJT Buffer
The First One mede uses ELNA Cerafine Audio Capacitors.
The Power Supply is my Board made by a mix of  Bust and Buck Switching Converters from main 12-24Vdc
So  From DC Supply we can obtain: 200Vdc for Tube circuit, 30Vdc for Buffer Circuit, 6,3Vdc 

"Goodnight" Powe Supply Board 

Switching Board with IC, Mosfet and Audio Board with Philips Miniwatt NOS ECC82  12AU7

NOS ECC82 Philps Miniwatt and Switching Power Suupply Board

Headphone Amplifier complete with a White Led on the base of Tube

TUBE

The Second One uses ELNA Audio Silmic II Capacitors

The Second One With ELNA Silmic II Audio Capacitors

 Boards and Headphones

DIY Headphone Hybrid Amplifier Schematic Simulation

To semplify last project I choose to exchange Current Generator by a simple Resistor.
Power dissipate is about 4W so this component, 60ohm, shoul be composed by 2x120ohm/5W resistors.

Semplified schematic

Distortion increase, third harmonic

Distiortion increase, Vin=1Vpk, Vout=5Vpk but the power on the Haedphone is 400mW near the maximun power admitted, 500mW.

At 3Vpk out:

3Vpk output

Hybrid Headphones Amplifier Project, ECL82 (6BM8) plus Power BJT for 32ohm Philips Fidelio X1 With Tube Distortion

I'm looking for an Amplifier to drive my new 32 ohm impedence Philips Fidelio X1 Headphones.

My personal project is illustrated below:

Static Voltages

I would have a tipical Tube Distortion, I choose ECL/PCL to drive a Big BJT witjout other BJT drivers, not only 2SC3281, maybe I'll use 2SC2337 I bought from GB but potential fake....
Q3 should be change by 2 diode 1N4148 with related R25 value.
The amplifier factor should be not high, here is 5, there is no overall negative feedback.
Below the Simulation of distortion with V2(Vin)=1Vpk, V(R6)(Vout)=5Vpk F=1kHz

Second armoni c distortion for: V2(Vin)=1Vpk, V(R6)(Vout)=5Vpk F=1kHz

Static Currents

HeadPhones Amplifier Bandwidth

I hope I'll make it soon...