After searching the internet, I got a lot of clues but no answer. Here is the answer.
The LM3815 wants an analog input up to 1.25 volts where the tenth LED comes on.
Arduino analog output is actually PWM at 5 volts, using a 5 volt supply.
This gets a smooth voltage between 0 v. & 1.25 volts.
If it matters, I am using a 1K resistor between the pins 6&7 pair and ground.
Someone checked it with a simulator and said there might still be a 25 millivolt ripple.
It looked flat on my scope.
Hi,
Why not just use the outputs of the Arduino, to turn om the LEDS, you don't need a LM3915.
You can use software to make your line of LEDs react to the level you want to use to PWM.
If you do not have enough outputs for the ten LEDs then use a shift register that requires two outputs from the Arduino to control your line.
What model Arduino are you using?
Tom... 
I am using a MSGEQ7 connected to the analog 0 input of a Arduino Uno. I am sending the 5 lower frequency volume signals with PWM to 5 LM3915 chips which drive 5 columns of bright white 10 LED bar graph displays. It looks great with fast flashes to the beat and notes. The 50 LEDs are mounted in holes from the back of a 8" wide X 10" high sheet of Plexiglas. I intend to add colors when I find tinted plexi, plastic or cellophane. It will fit into a clear box type picture frame. I saw some examples where they used one LM3915 and multiplexed the output to 5 columns but I wanted it as bright as possible.
Hi,
After searching the internet, I got a lot of clues but no answer. Here is the answer.
Sorry I misread your post, you have found the answer and have your project working?
I saw some examples where they used one LM3915 and multiplexed the output to 5 columns but I wanted it as bright as possible.
Well my advise is don't mutliplex, if you have it running as you want it, and the 5 x 3915 are already wired in, what is the problem?
Good show that you have such a project working.
Tom..
TomGeorge:
5 x 3915 are already wired in, what is the problem?Good show that you have such a project working.
No problem.
I combined a voltage divider and RC filter. Using a potentiometer and trial & error, I solved it myself.
Just putting it out there for the next guy.
When I get color for the different frequencies, I will take a video & post it.