handy stuff

[Enzo]

Thinking about handy little short cuts.

I just looked at this on my shelf, and thought I hadn't posted it in a while. For those who do not yet have tube bases burned into their memory. Or get tired of calculating output.

[Justin Thomas]

Thanks Enzo - that V/O/W chart has helped many times. Nice to have tube bases handy too!

Justin

[Bruce / Mission Amps]

The Watts to Volts to load is cool... just make sure you never actually use it with a 4 ohm, 8 ohm or 16 ohm speaker.
Always use a non-reactive load and a scope to view any distortion... then you also can be disappointed to find out your 50- watt amp is actually only making 38 watts...!! LOL

[Steve A.]

Thinking about handy little short cuts. I just looked at this on my shelf, and thought I hadn't posted it in a while. For those who do not yet have tube bases burned into their memory. Or get tired of calculating output.

Just to clarify things those tube sockets are viewed from the back side with the terminals and not the front side which is what the tube plugs into- right? I'm always looking at an old BF layout drawing to figure out how to wire up tube sockets- your drawing will be very much appreciated!

Steve Ahola

[Enzo]

Tube bases are always drawn as if you were looking at the pins from underneath.


Bruce is right, it is not the same as feeding a speaker. WHat the chart is good for is you can look at it on the wall, and not have to get out a calculator to do those exact figurings.


I had posted those before, but I tried searching them up and couldn;t find them. Lot of newer members won;t remember them.

Here is one I always liked. Mine is one of those cardboard slide rule things, but I don't see anyone making them anymore. But if you print this on heavy stock or paste a paper copy on cardboard, cut out the black areas and put the slider behind those windows, and you can have the watts-Ohms- VOlts- Amps thing at your fingertips.

[diydidi]

Reactance chart I found handy!!

[Enzo]

Yeah! That's cool.

[km6xz]

That brings back some memories. I had forgotten about those slide rules HP and others gave away. I had one for years but somewhere along the ages, must have misplaced it. They made an older one that their sales department gave away back in the 50s which was a circular slide rule that had more scales on it. They were made of plastic.

[Enzo]

I have a small collection, I always thought they were cool. Usually they are real specific. I Have one for realtors that calculates numbers for mortgages. I have one from Crown for calculating constant voltage things for speaker runs, flip it over and get inverse square law for SPL and SPLvsPower. I have one that measures rubber belts.

[Brad1]

you also can be disappointed to find out your 50- watt amp is actually only making 38 watts...!! LOL

Or...your 105W Univox is closer to 130W?!

Brad1

[bob p]

That tube base chart looks nice. I'll print that one out.

Just a note about voltage tables -- it's important to keep in mind the difference between RMS volts (like you'd measure with a true RMS meter) and peak volts (like you'd measure with a scope). I have a spreadsheet that has columns for both RMS volts and peak volts and lists the corresponding power into 4, 8 and 16R loads in the other columns.

[philbo]

A quick mental shortcut I've found useful for figuring dB gain & loss in my head (referenced to power):
-1 dB ~= 4/5 (a loss of 1 dB means the output power is 4/5 the input power)
-2 dB ~= 2/3
-3 dB ~= 1/2
-6 dB ~= 1/4
-10 dB ~= 1/10
-20 dB ~=1/100

If you flip the fractions upside down, then they give gain (positive dB).