Thursday, May 28, 2009

Tinkering 6DJ8

6DJ8 is the tube of choice, small signal triode, with 2 triode encased in one glass envelope.

It has a large family which is fully compatible, namely,6922, 6N1P,6N11, ECC88, EC88C, E88CC, E188CC, E288CC, .

Plenty of tube rolling opportunity.

It is good sounding, wide applications. It's high Gm, medium gain and low Plate Resistance. With some circuit tinkering, we can build quality Pre-amp, Buffer-amp, driver for small power SE amp, headphone amp... etc

IMHO the only tube which will sound normal when connected as cascode.

There are plenty of NOS (New Old Stock) available, as well as current production.

Wednesday, May 27, 2009

Tube Tinkering


"In electronics, a vacuum tube, electron tube (in North America), thermionic valve, or valve (elsewhere, especially in Britain) is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space."


A century old tech, their place in this modern world are limited to large scale signal transmission thank to its robust operation capability.

They some how managed to survive the guitar amp industry due to various aesthetic and nostalgic sentiments.

Mythologized by modern marketeers with hypes limited only by imagination. This glass ware is gaining support in the HiFi consumer market as well.

We get increasing impression of tube amps being more art then technology... IMHO, when we don't know the actual science behind a technology, it is most convenient to save face by branding them as art....

Despite all my negative impression on the sales slogans, I truly love the "Tube Sound", its as close to paradise as one could get.

In the coming articles, I'll share my tinkering journey with 6DJ8. I'll talk about some theory and specification stuff but I do my best to spare tinkerers with heavy doze of boring theory stuff instead just outline the essential start tinkering with tubes.

Circuit Theory for Tinkerers

Like it or not, we need some basic Circuit Theory for tinkering in electrical and electronics gadgets.

BTW, changing a plug, replacing a wire, spay some paint does not count as tinkering in my book. When I tinker, I dig deep.

Where did I picked up the circuit theory know-how?

All Engineers took electrical classes somewhere along the academic route; We enter the classroom, went through the motion of listening to the teach/lecturer, collect all the handouts, do some tutorials and off we go to the exams… to return the knowledge in written form. Hopefully, some of these knowledge will residual in our brain. In my case, Ohms Law, power and summation of component value calculation stayed….

Lucky me, enough for tinkering and be dangerous.

Ohms Law

V = I · R

V is for voltage, V is the unitI
I is for current Ampere, A is the unit
R is for Resistance, Ω ohm us the unit.

From here, we can derive the following equations

I = V / R

R= V / I


P = V · I

P for Power or Watt, W is the unit
V for Voltage across the component
I for current running through the component

Summation of Resistance

Series Connected Resistor

Rtotal in series = R1 + R2 + R3 + … + Rn

Rtotal is the resulted total Resistance of the series connected resistors
1, R2….Rn are the Resistance of individual resistor

~handy tips,

When connecting same value resistor in series,

Use This --> Rtotal = Rindividual x Pieces of resistors

Parallel connected Resistor,

Rtotal = ((R1)-1 + (R2)-1 + (R3)-1 + …. + (Rn)-1)-1


Rtotal is the resulted total Resistance of the connected resistors

R1, R2….Rn are the Resistance of individual resistor

~handy tips

When connecting identical value Resistor in parrallell

Rtotal = R1 / pieces of resistor

How to use them?
  • Ohm’s Law enable us to figure out how much voltage is across the component and how much current going through the component.
  • We use this as the minimum required ratings, i.e. current, voltage and watt rating of the components. *PS* For Power rating, give it at least a double,I triple when I have the chance.
  • Summation of resistor allow us to add/reduce Rtotal in the circuit. By changing the Rtotal, when use with Ohm’s Law, we can figure out how to adjust the current and voltage of the circuit and/or components. Which is an essential know-how for tinkering.

Monday, May 25, 2009

Computers and Micro Processing Unit

My inaugurate experience with computer was the Sinclair ZX81, a present from my aunt during my primary school days.

It displays a green screen on home TV. It was also the first time I actually learn something by reading instruction manual. Manged to write simple BASIC language program to occupy the screen with numbers and alphabets, make them blink, change color and make some beeping tone... etc all the usual big hoo haa at that time. I was never successful is saving any programs on tape recorder as described.... Also we can play Pong with it.

At the end, I annihilated it in the search for higher wisdom.

My next "serious" encounter with computer was in my polytechnics days when the syllabus requires CAD drawing on a Prme Medusa system, FORTRAN77 and 8051 mcu programing. The 8051 is a populated PCB baord and a 2 x 7 segment display and a input keypad which we used to punch in HEX machine code. We happilye blink some LED, excitedly make the Knight Rider running light and a traffic light as course work. Frankly, I didn't learn anything from here as my attention was on those sweet young thing around.

I then used WordPerfect in the uni's computer lab to write my final year project, the great graphics features and lovely spell check made my life much more bearable.

Then came the windows, the internet, Netscape, IE, the dot com bubble... and I was happily going along with the flow.

Until a few years ago, a fellow audio diyer built a NOS (Non-OverSampling) DAC with 3 DAC chips, namely the TDA 1541, 1543, 1545. He used a mcu to control relays for selection of chips for AB test. Another made source selection with mcu controllered relays. This sparks some interest.

For the pass 4 years, I'd been trying to start tinkering with mcu but some how it didn't happened. Firstly, I don't know where to start, and when I did, I don't have a programmer, then then training kit was too expensive and I'm too lazy to built one, one hurdle after another.... consequently, a netural death...

Friday, May 22, 2009

Why I Tinker?

I am cursed with impulsive curiosity toward the how's and why's of "things" works, just couldn't help it.

To deal with this curse, I dig and strip anything that fancy my curiosity. Eventually, I'll build a similar "thingy" base with some variance as proof of concept. One thing lead to another, I end up a hobbyist carpenter + machine machinist + metal worker + electronic technician and whatever is required of me to make it happen.

Tinkering with things is how one learn the working principle of things and deal with my incurable decease.

For the past few years, I embarked on electronics "thingy" because I am really an electronic idiot. DIY audio equipments seem to be the right track to teach myself electronics... again, one thing led to another, I design and built more then a few tube amplifiers and loudspeakers.

This blog will be my platform to share my learning experience with the like mind people and hopefully will start a few friendship along the way.

Maybe someday... after I'd satisfied my appetite for electronics, I'll proceed with shipwright... who knows... For sure its a bigger money pit.

Until then lets do some soldering, hole drilling, welding and metal cutting.