Topic: diyer's Hybrid Tube PreAmplifier

[alientbelt]

Hello To all diyer's,

I would like to share this simple project, it is more on the "abc's" of electronics, a little of software programming and few little on sonic, its more of being happy watching your own masterpiece, when you see the outcome of your work,  than (probably) listening to its performance, although the main target is to enjoy both the Displaying and style of controlling with Audiophile performance.

What I have here is a Vacuum Tube Preamplifier  adding with digital controls to add some customized display and some stuff like gain control, bass, treble which are done in digital domain thru software applications.

I hope you like it,  and I hope our audiophile expert can help to bring this Pre-amplifier into the next level better than what I can do alone.


This is the analog part taking care of Audio processing


Here is the digital controller running by MCU (Micro Controller Unit),  a program requires to run the hardware,  it comes with programmable  Tone Control with Volume control in 1 or 2 dB steps adjustable using the binary encoder,  looks like potentiometer with push at the center to access the "menu", to adjust the Gain, Treble, Bass and Speaker Attenuation control using rotate left or rotate right.

These are the prototypes to confirmed the idea and allow me for experimentation.   Anyone whose into diy electronics can build the same too,  I think, even a beginners can do it.

[alientbelt]

I should start the display with





Let's see some MMI (Man Machine Interface)

[alientbelt]

The analog module will now meet its digital controller module





we have now a working Pre-amplifier hardware  based on 6N3 vacuum tube operating at low voltage of +-32 Vdc.  The MCU and LCD operate at +5Vdc, the digital Tone Control operate at +9Vdc.   The nest step is obviously to test it functionally with an Amplifier match with good speakers and a clean source of music.

[Weng!]

wow, ang ganda sir. put this amp in an anodized aluminum case, hi-end na ang dating. very good job

[Nelson de Leon]

Question sir, does that mean analog input siya, then convert to digital via ADC for digital processing, then back to analog?

[alientbelt]

Hello,  for Audio signal  is pure analog processing, analog input and analog output.  Di bale itong module ng vacuum tube pre-amplifier



standalone pre-amplifier na siya,  kulang nalang ang Potentiometer para ma adjust ang Volume as a means to increase and decrease the  Volume level.  Iyong idea ay papalitan ng  digital means (use Mciro Controller)  inyong Potentiometer para mayroon ibat-ibang means of controlling the volume,  puwede ito manual adjustment o di kaya puwede tin Remote Control  IR o kaya RC,  also to add stuff of displaying information to make the MMI to have a better interaction  (Man Machine Interface), like when you increase the volume and you will see on the LCD the volume level in dB,  or, when you go to the Menu and when you press it, you will hear a beep, some sort of.

So here, it is the idea of "controlling" that is why we have this digital module to do the job



The binary encoder, that looks like potentiometer but it generate binary signal which decode by the MCU, the program knows when you rotate left or rotate right or press the center to go into the Menu.



The yellow PCB composed the MCU and its hardware like Buzzer, Switch, LCD port, etc.  which is the command center, this is where we load our program (firmware).  Behind it is a Tone Control (green PCB), it is an analog process but the way it is controlled is digital means  using the I2C protocol developed by  Philips (NXP).   It means, when you adjust any of its function like the Gain, Volume, Treble/Bass,  you use program (I2C protocol). 

We used this so that we can have a control of the Volume --- it is this reason we have more hardware, but it pays off with additional controlling and style,   probably if you look at deeper into its electronics, maybe  more degrade performance due to the fact that I2C protocol which is a high speed bit stream may interact into the analog processing which inject some sort of high frequency noise (when the design is not careful engineered).  Those challenges makes diy builder a better guys, something they can be proud of when we (they) solved such problem on the power of their fingertips.

[alientbelt]

let's see its history in this link    http://www.1diycentre.com/Tube_for_a_CAUSE.html      perhaps pay attention on the New idea Block Diagram   which has been remodified for many times  (I remember that even some guys would like to include iphone or Android controlling via Bluetooth or Wifi, eventually, it ended up in Hobby level)

[Nelson de Leon]

Thanks for the explanation. Gets ko na.
Nasa analog domain pa din ang control pero digital ang controller. Just a thought, instead of gain via potentiometer ang kino-control, may available din bang multiple resistor type na parang DACT ang volume control?

[alientbelt]

ano ba technical term doon, stepper potentiometer, at mayroon dB attenuation step iyan, I have seen sa ibang post sa internet.   

[Nelson de Leon]

ano ba technical term doon, stepper potentiometer, at mayroon dB attenuation step iyan, I have seen sa ibang post sa internet.   

Yan nga ata. I dunno much re techincals and electronics kasi.

[alientbelt]

Let's put some MMI to control the Bass and Treble,  its limit to 0~+14dB boost only, as I think cutting the treble or bass wont make the music sounds better,  a 0 dB means there is no boost or cut, its flat response.





How is the volume?  it is measure in terms of Attenuation denoted by the minus  "-",  say,  -40dB means it attenuate the signal by 40dB, a 0 dB means no attenuation,  -80dB is mute according to the datasheet of TDA7449.  You have to send data into the TDA7449 using I2C protocol.

[alientbelt]

demo firmware is ok for testing,  let's see some action

1.  Using PC as Player
I will need to use a DAC, 24 bit 96 KHz connected to my PC on USB port, the DAC output is analog connected to the input of the Hybrid Pre-amplifier



The amplifier is a class-D with smps power supply,  I just share this amplifier today here at the forum,   http://www.pinoydvd.com/index.php/topic,183383.0.html





Th CD is Susan Wong Best Selection 16,   songs like "You Needed Me, Sometimes when we touch, Stay a While",   the Speaker is bookshelf type - full range pioneer, rated 30W 8 ohms.


2.  Let me try the Phono Player


This phono already included the phono preamplifier and can fed the stereo audio directly into the hybrid pre-amplifier

[alientbelt]

wow, ang ganda sir. put this amp in an anodized aluminum case, hi-end na ang dating. very good job

Thanks for the suggestion,  I would consider that.

For me,  and some other guys who are bloody DIYers,  I prefer like this, which all my prototypes keep inside the case,  minsan tawag namin dito ay "Kikay Make-up kit",   a sample of a prototype,  soon, this prototype will be house like this :

[docpuge]

Are u planning to sell this? Astig eh! nice work sir... 

[ATJr.]

Welcome to the forum alentbelt......there are more end users here than diy'ers than at elab.....
are you going to sell your turntable with built in preamp as well? can you give srp please?

[alientbelt]

hello Sir  it was planned for diyer’s who would like to customized, as for us bloody diy, we do do what we like as I do not like the standard product

but several diyer’s can help to build a version for a specific design.  With your query, Im thinking to make a standard  version,  and from the standard version will deviate for customization

@ATJr,  the Turn Table is only for checking purposes at that time.  I am not really sure if someone like it,,  but for DAC and digital  coax, fiber interfaces or bluetooth interfaces and with music source such as media player,  probably our friends stationed in China can provide an offer

[fishda]

very nice sir. what's the sound character of the pre amp?