The flash is from a small bit of thin filament with a low resistance when cold, when heater voltage is applied a large inrush current goes through, the small filament heats up quickly (flashes), increasing in resistance which then allowing the main heater to warm up with the current stabilising.

Quote: Originally Posted by cerbie You can drive an LED quite well with a voltage source (LM317+pot+spare DIP socket--try it). However, 20mA is more likely to be the same brightness between samples than 3.0V will be. I like real ones better than text book ones. Things do start...

Quote: Originally Posted by cerbie The thing is, 1ma could be 2V, 10ma could be 2.5V, and 50ma could be 3.5V--not a nice neat voltage scale (it's logarithmic, as is your perception of light). So, with a plain RC circuit, you would be ramping voltage, the LED would appear to turn on late...

Logarithmic, so at first the change in brightness is large, but as the current goes up the change becomes smaller. I would look into PWM circuits, adjusting the duty cycle from 0-100%.

Quote: Originally Posted by nullstring Tridacnid: whats a CCS chip? Punnisher: I want a gradual warm up.. not one that is instant after a few seconds. CCS is a constant current source. LED brightness depends on the current, not voltage. So you cannot simply use a capacitor to...

I would be really interested in being in the prototyping phase, can I put my hand up? How much power output would it have?

Quote: Originally Posted by smeggy Switched it down to 6v, plugged in the 6n6p and off it flew... nice bass increase over the Siemens and the rest sounds damn nice too. I'm very happy with it especially considering how cheap these tubes are. I like how this sounds a lot Big tube...

Would anyone in/near Australia be interested in a completed CTH amplifier? I made five, and one person pulled out of paying for one.. So I have a spare fully made and tested, with the C3H modification and perforated top (thanks wiatrob!) and the choice between a few different tubes I have...

Quote: Originally Posted by Jingo Lingo Thanks for the replies. I have a multimeter so i'll try that out. Would you think the power supply needs to be exactly 500mA? Could I get away with using a 400mA or 600mA wall wart? The current rating is its maximum supply current. Hence it...

I am using a gamma1 with the optical out of my MBP.

R and C should be in some generic library, I think it is 'ANALOG'. A lot of what you have is unnecessary for simulation, get rid of the charge port, iPod dock, 3.5mm jack and switch. Use a resistor of 32ohm (or whatever your headphones are) to simulate the headphone output, use a Vsin (from...

Here are a few schematics for ideas: Variable PSU 0-30 VDC STABILIZED POWER SUPPLY WITH CURRENT CONTROL 0.002-3 A 0-15 Volt Tracking Power Supply Using a multi-tapped transformer with some comparators and relays would allow you to have the input to the regulator switch to the appropriate...

Yep he means SPICE (Simulation Program with Integrated Circuit Emphasis). It will allow you to simulate the circuit and analyse voltages/currents at any node, and a lot more. There are a few free ones available. And if you want people to comment on it, just attach your schematics to your post.

Quote: Originally Posted by Mizu So if I understand correctly, a Dac will do a better job than the Mini3 on itself when converting digital signal coming from a computer/mp3 player ? A DAC converts digital to analog. The Mini3 does not do this, it takes the analog audio signal...

Just thinking out loud, would a ripple on B+ cause hum? Has anyone looked at the B+ waveform loaded/unloaded? Of course, make sure your oscilloscope can handle ~100V inputs (or AC couple it). Is VG stable compared to SG? And is it recommended that SG point be connected to anything? I've...

Quote: Originally Posted by jacc1234 I am not sure if I have the heater switch installed correctly. It has 6 "lugs" 3 in each row and looks like this: === I soldered H1 and H2 to the left and right lugs on the top skipping the middle. I am thinking I should have connected one to the...

Quote: Originally Posted by holland you can put a fast acting fuse on the output and input or a breaker. Variable current limiting is nice, but you can do it on the cheap with a few properly sized non time-delayed fuses. Easier to use a current limiting circuit. A fuse or breaker...

I agree with the above, its best to buy a good quality lab power supply. I was toying with the idea of DIY'ing one, but I decided to buy a dual adjustable output, fixed 5V one like this: Triple Outputs Laboratory Power Supply-CA18303D - eBay (item 270385823382 end time May-12-09 11:41:00 PDT)...

If you are going to use an LM317, the National Semiconductor datasheet recommends 240ohm for R1 and 720ohm for R2 to give 5V output. So if on the TREAD you use R1 = 240ohm, then R2 and the pot resistance must equal 720ohm to get 5V out.

Quote: Originally Posted by sandbasser For those non-engineer types among us (chiefly me, or so it seems)... what would need to be done to a Tread to change it to 5V??? Thanks, Easier just to use an LM7805 +5V regulator, rather than an LM317 adjustable voltage regulator if...

Quote: Originally Posted by runeight Yes to the first question. You are correct about the buffer. Its Zi is so high that increasing C4 is unlikely to affect the base response. Are you hearing variations in base with different tubes? Excellent. Yes I am hearing different bass...

The 175 lacks backlight and temperature measurement, so if you don't want them and want to save money then go for it. But I would buy the best you can afford, as you probably wont ever need to replace it.

Just two quick questions: With my headphones (MS-1's, 32 ohm), I only have to turn the pot about 1/3rd around to get the maximum volume I'd want. I am using 100 ohm resistors for R18L/R. Would roughly doubling R18 give me more control with the pot? And will this decrease the noise present...

You can't go past a Fluke. I use a 179.

Question, would increasing the value of C4 improve the bass response? Or is the input impedence into Q4/Q5 sufficiently high that it would not make a noticeable difference increasing C4 to 470nF/1uF?