Let it Glow #2

How hot is a class A pentode?

As pictured, it is 6n14p pentode at 12.5 watt dissipation, class A biased at 50mA/250Vplate. It can reach 200 degree CELCIUS inside (cathode) !!!

Outside, there is still glass cover and vacuum in between, so the heat transfered may only be the radiated one.

How hot is the glass tube? I have no idea, but smelling the heat on the air surrounding it, well, just DO NOT touch.

Let it glow..

Let it Glow !!

I learned tube circuit the hardest way, by using 6n2p-ev (high gain dual triode, 6.3v heater) at 12V. 

Why is it the hardest, because at 12v, the "tube theory" doesn't work at all :

- biasing is hard, no negative power supply, very small anode current for cathode resistor

- gain is limited, i got only 10 from

- headroom is limited, i lost around 2V on both side, makes only 8v room to play

- output inpedance still very high

On the good side, the limited gain works enough for line level amplification for a small watt application (headphone amp, etc), therefore i build my first "tube amp" for headphone amp.

My headphone had only 16-32ohn impedance, it need current driver more than voltage amplification. Well, such current can't be provided from tube circuit at low voltage supply. Therefore i use BUF634 chip for the output. The tube act as voltage amplification, the buffer act as current driver. 

6n2p-ev is dual triode high gain (similar to 12ax7 but with 6.3v heater), the biasing is done by resistor to positive 12v (??, amazing discoveries by the person who created attached pdf file) to make sure anode voltage at around 6v-7v, with stereo 100kohm pot at input side as gain control, 100kohm plate resistor, 15kohm grid stopper resistor, and buffer at output side (coupled by 2200uf 16v , grounded with 1kohm resistor) to the headphone. This makes me have to wait for the capacitor to fill up (to make sure output at ground level) before i connect the headphone or else loud pop exist, the same need to be done in reverse when power off, headphone need to be removed before power being turned off.

The heater is powered by lm317 set to 6.3V output, slow start done by adding big capacitor at adjust pin to ground, the problem is it waste a lot of power on thr lm317, proper heatsink is needed (300mA x 5.7V, around 2 watt).

The sound is warm, i believe i hear more detail of the sound (like breath of the singer, detailed drum playing), and this save my flac player battery as i can play it at low volume and let the tube amplify.

Let it glow..

One bike to work, one less car on the street ..

One small step on the pedal is one giant leap to healthy life.. 

10 km with strida and the new foldable butterfly handle bar !

Strida with Butterfly Handlebar #2

Testing the new handlebar on Strida for few days shows me that i use the top(further) position more. The lack of folding mechanism on the bar (due to short brake line) is another negative part i want to improve.

Therefore last two days i got my self two 150cm new brake lines, and managed to replace te old ones. It ia quite easy installation, i remove the inner cable from both old and new brake lines, and i tape (yes, tape) the new line on the bottom section of the old one. The tape must be strong but thin enough avoiding stuck inside the frame. So i pull the old one from the top, and at the same time i push the new one from the bottom. New brake line move smoothly guided by the old line. The front one need to bend sharp near to handle clamp, but the guide line help it done nicely. The rear brake line need no help, it goes to the center linkage hole, and then i install the spring protector, and passed to the front area. 

I make holes on each side of the handle bar (put a mark on the locking notch before you make the hole, it is inline with the hole for the twisting mechanism), puch a 3mm brass bar, cut it enough, and trim the handle bar end little bit to allow rotation inside the handle clamp. Now it can fold nicely!

So another ride to the same spot, with my Strida and the same butterfly handlebar, new handle brakes position, and bigger smile on my face !

Testing the butterfly handlebar on my Strida

This is awesome...!!!

Strida with Butterfly Handlebar

In my search to improve my Strida handling, i cut a butterfly handle bar and mount on it. It is quite difficult to find good position for the brake handles. as what best for the hand position may not suite for the brake handles, instalation plus i don't want to mess around with new brake cables (in case i need longer ones).

So what you see in the pictures is the final result after several trials and errors. It improves the riding quality as it improve the ergonomics by providing several hand positions. The shortest hand position improve stability on launch (less wobble/wiggle), and the longest position improve the stability on cruising as body mass spread further to the front.

I didn't put any hole to the bar as in this position it can't be folded properly flushed, therefore i loose the folding capability in exchange for benefits above. Not a big deal, in fact it adds eye catching effect (which already too much from the bike it self). Let's  have a ride...