Buzzing Noise : LUSENET : Wiring for DCC : One Thread

Hi all...

Just installed a Digitrax Empire BuilderII on my small layout. The installation went well as did my install of a DH142 and a couple of DH 121's in my Kato's.

My question is how can I eliminate the buzzing/humming noise that is emitted from my loco's - especially atlow speeds? Or, is a certain amount of this type of noise inherent with DCC?

Thanks for any and all suggestions from the group.



-- Craig L. Slawson (, June 23, 2002


The noise you hear is what you get with those Digitrax decoders. Some motors make more noise than others but you can't eliminate it witht eh decoders you have. You can if you buy the newer decoders from Digitrax and others that offer "silent running" or "stealth drive" or whatever marketing term is used to describe the feature that provides an adjustable higher frequency drive pulse to the motor.


-- Dale Gloer (, June 23, 2002.

Hi Craig.

If the frequency by which those engines get driven is raised then the noise level comes down. The frequency is determined by the decoder. A good decoder runs above 10kHz frequency. Zimo is a manufacturer that builds what they call "Supersonic" decoders. They are the only ones that drive the motors at 32 kHz, thats beyond our hearing range! It is adjustable between a low frequency of 30Hz and 32 kHz. They also have fully adjustable back-emf and many more features. If You want to check them out, go to this web site: The prices for the decoders came down drastically. They are now selling for Can$55.00.


-- Art Luescher (, June 24, 2002.

Thanks all for your help!

All the best,


-- Craig L. Slawson (, July 01, 2002.

I pleased to see an open and frank discussion on this subject. It is true that both NCE and TCS proudly offer quiet decoders, but when I approached Digitrax with the same question they first insisted that their decoders did not make any noise (some months ago), and just today responded "maybe you should look at our web site", referring to their new 163 series decoders. It's sad that they still can't give an honest answer to an honest question. Nothing in their web info directly suggests that these are silent decoders, although its quite possible that its hidden in the techno-babble that Digitrax is so fond of using. I would appreciate hearing back if anyone can confirm whether these new decoders are in fact silent.



-- Sheldon Frankel (, July 29, 2002.

I think you're missing something very important. In your zeal for silent decoders you lose one very big advantage. The low frequency Buzz is what makes such smooth operation at slow switching speeds. Newer microcontrollers running at high frequencies allow the maker to tout "silent or quiet" operation. Trouble is- you lose performance! TCS has restored some of this capability with "dither" programmable with CV56 & CV57 and it seems to work well. My ancient NCE decoders built from kits run balky old Athearns very nicely thanks to the low frequency buzz. In the old days we paid extra money to get this buzz and it was marketed as "pulse-power"

-- Wayne Roderick (, July 29, 2002.

Wayne is correct about the low PWM frequency of early DCC decoders causing a motor 'pulse power' effect. I have purposely re-programmed several of my NCE 'silent-running' decoders to operate at 35-40 Hz just to regain the smooth operating performance at low speeds on older engines. Pulsing at a low frequency doesn't always mean creating lots of noise. Play with the PWM frequency CV9 (?). You may find as I have that some motors and loco gearboxes are relatively quiet at certain low frequencies. Pick the ideal PWM frequency for each loco. Do that before attempting to set up max & min speeds or speed tables as the resulting speed is affected by the PWM setting.

-- Don Vollrath (, August 02, 2002.

Maybe small scale motors respond differently from the larger motors used in large scale, but I find that the high frequency decoders, and Aristo's Train Engineer, provide BETTER slow speed performance than the extremely noisy Digitrax and MRC decoders. The noise made by a DG580L can be heard from 30 feet away when driving Mabuchi motors.

The addition of back-EMF (in the Lenz LE230 low frequency decoder) and the Zimo high frequency decoders makes for extremely smooth low speed performance, especially with 2 or 4 motor locos which sometimes have problems at low speed due to less than ideal motor/drag matching.

- gws

-- George Schreyer (, August 03, 2002.

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