Brilliance Sound Decoders

Either that, or they've gotten it confused with the sound of four exhaust "chuffs" per revolution of the coupled wheels - of a two-cylinder steam loco with the valves set properly square...

A two-cylinder simple steam loco will "chuff" four times per revolution of the coupled wheels - perhaps this is what they were trying to say?

Froggy, what brake schedule do loco-hauled passenger cars currently use? When visting the US some years back I saw some cars with HSC schedule equipment - is this still used? Are there any operators using electro-pneumatic brake on loco-hauled stock?

All the best,

Mark.

Are you saying that it isn't "integrated into the mechanical dynamics of the locomotive" if the engine sounds change every 16 steps of 128?

Absolutely, yes. The thing uses throttle setting to try to "guess" what to do and it doesn't work. This is especially true on steam sound modules, which truly suk majorly. The old PFM sound system was the best I ever heard. It was capable of emitting the correct sound for any locomotive condition. It did this by being mechanically coupled to the machine rather that trying to use electrical/electronic information to guess what to do. You absolutely ~must~ know the exact RPM of the driving wheels on a steam locomotive in order to get the correct number of exhaust beats. Trying to guess by measuring the voltage applied to the motor, or the current demand of the motor, or the back EMF of the motor will never work. A short light train will have a completely different electronic "signature" than a long heavy train for the exact same speed. The sound module doesn't have a clue, so it cannot distinguish between the one and the other, thus it cannot produce the proper sound for the one or the other. Cutoff is the other quantity in steam locomotive operation that completely eludes all the sound decoders I have heard to date. You must have some way to control the cutoff. I think the people who design sound modules do not have a clue about how a steam locomotive operates nor what one is supposed to sound like. Your eyes and ears, however, can see and hear the difference unless you choose to be blind and deaf.

With a diesel sound module you cannot shut the throttle off and roll the way you can with a real locomotive. On level trackage, you open the throttle to get the thing rolling, then shut off and let it go until it begins to slow. If it doesn't slow, then you just let it roll with the engine at idle. Same thing downhill, you knock off the brakes, give it a bit of throttle, then shut off and gently retard the acceleration with light brake applications. If the grade is steep enough you may even need to use dynamics- if the loco is so equipped. This is not the only shortcoming of diesel sound decoders. They are many and vary from manufacturer to manufacturer.

In all, the pseudo-science of sound recreation in model locomotives still has light years to go before it is acceptable. For the present, it is nothing more than a waste of money to produce "white noise" gibberish that masquerades as "Authentic Locomotive Sound" Rubbish!

Froggy,

I thought you were specifically criticizing the Brilliance, but I see now that you feel the same way about all sound decoders. Is there anything in the specs for the Brilliance that makes you believe that they're doing better or worse than other manufacturers?

I don't know about Froggy, but I would _not_ expect the sound to change every 16/128ths. Why? Because the run has to do with the power required, which is not the same as the speed of the train (loco.) A drag freight (say a unit coal train) at 25mph may require all the power available, so the engines will be running in run 8 (an AC4400 or SD70MAC in max power mode is an awesome beast!) But a fast freight, shorter and lighter, moving at, say, 50mph will take the same or even lower engine power output.

Example: In Saskatchewan this past summer, I saw and heard a single AC4400 hauling about 120 grain cars: I estimated the speed at about

40mph (60km/h), and the engine sound was not at maximum revs as far as I could tell: ie, it must have been an empty train. A few days later, in Jasper, I watched three SD-40s start up a loaded grain train, the engines revved up a notch or two, and the train began to move -- slowly at first then picking up speed. Then he notched it up some more, and the train moved at what would be a fast jog for me. The noise was terrific. The engineer kept the train at this speed until it cleared the crossing about 100 yards down the track, but he was using a lot of power. Then I heard him notch it up some more as he hit the grade up to Red Pass Junction, but the train's speed didn't increase by much.

Diesel loco sound and speed do not correlate in a nice, linear fashion, as you seem to expect. That is, I'm getting the impression that you expect the sound of the engines to change the way the sound of your car or truck changes as you step on the accelerator. It should not be like that at all.

Diesel-electric engines do _not_ accelerate the way cars and trucks do. The diesel engine runs a generator, and the generator's power output depends on only two things: the rpms and the excitation (magnetic field strength.) The power developed by the electric motors depends only on wattage, ie, volts x amps for a DC motor, a little different for an AC motor. A motor at low revs (low volts, high amps), and a motor at high revs (high volts,low amps) can be producing the same power. Thus revving up the diesel engine does not always translate into higher speed.

So, IMO the perfect sound system for a diesel loco would respond to the amperage: higher amps = higher load, and should produce a higher run sound, regardless of the loco's speed. Maybe there should be a wheel-speed monitor, too...

HTH

The decoder has access to both average volts, ie PWM level, and current so should be able to compute and use a signal proportional to power demand, CVs could be provided to allow the user to adjust the power range of each notch to suit his loco. This should not need any link to speed as such. If the loco has back emf control it should still notch up and down as the power changes to keep a constant speed.

Similar arrangements could be used to vary the cut off on steam sounds but would need to link in to the speed signal, which you need anyway to synchronise the chuff.

Keith

There are (usually) eight throttle steps. As the engineer 'notches' up through them, you hear distinct stepwise changes in engine rpm.

That said, as each new upward step is applied, the Diesel engine RPM increases noticeably, but the electrical load varies with train speed and other factors. So, within each step, there is a range of sounds produced (whines, growls, buzzes, clacking) in addition to the engine noise. These change with train speed.

Depending on the model of locomotive, the electrical connections to the traction motors (series parallel, combinations thereof, etc.) are also switched in an out as needed with the varying mechanical and electrical load ("Transistions"). This also make changes in the electrical motor sounds, and may include relay 'clacking'.

The blower fans (often quite noisy) are thermostatically controlled, and ramp themselves up and down as conditions warrant.

In moving downgrade the dynamic brakes (IF fitted) also make distinct sounds (whining, usually), and require the Diesel engine to be operating well above idle RPM as well.

And, of course, 2-cycle (EMD) and 4-cycle (Alco, Baldwin, GE) engines sound VERY different, with individual variations as well.

Aside from the Diesel engine sounds, most of this also applies to electric locomotives.

Add various horns, bells, etc.

So, the TOTAL sound produced is HIGHLY variable. that's why many object to 'generic' Diesel sounds. There "ain't any such thing"!

But basically, yes, usually, to first approximation, the sound does increment in eight distinct steps.

Dan Mitchell ============

Full RPM, yes, but not full power. These could vary the number of cylinders in use with power demand. When just running HEP (IIRC) they only used four cylinders. And, the main traction generator was not in use at all (though turning with the rest of the 'stack').

Dan Mitchell ============

Not at all! Steamers were infinitely variable within their capacity.

A conventional steam loco (2 cylinder) always produces FOUR 'chuffs' per driver rotation (2 cylinders, double acting). this is also true of a (compound) Mallet (four cylinders, but only two exhausting to the 'outside')

A 'simple' Mallet (a bit of a misnomer) or a duplex (four cylinders) produces EIGHT 'cuffs' per revolution.

Triplexes, and three cylinder locos (rare in the USA), and other strange arrangements also produce different or odd exhaust beats.

That said, the exact sound of the exhaust varies greatly with the size of the loco, the type of stack (or 'front end'), the throttle setting, the valve 'cutoff' setting, and the load.

Dan Mitchell ============

It's NOT instantaneous, but it is quick, and DOES make a vary distict change in sound with each step. Generally, higher step settings are LOUDER (more power), but also higher pitched as RPM increases.

Dan Mitchell ============

Possibly the electronics/sound engineers also have 'no idea'! :-((

Even the BLI steamers often have VERY poor 'chuff' timing related to speed. Supposedly this is variable with a CV setting, but I've never seen it work decently at more than one speed.

And the choice of the digital recordings can be VERY suspect. My BLI PRR M1 sounds good at low speeds, but shifts into a weird "Chuff-hiss-clank, whoosh" rhythm at higher speeds that sounds like a broken-down 0-8-0, with a dropped rod, trying to limp back to the enginehouse to die. Pitiful! The T-1, J-1, and K=4 sound MUCH better.

Some of the Soundtrax units are synchronizable with a 'sound cam' on one axle ... THESE can work WELL (as I've seen).

Dan Mitchell ============

At a clinic I learned there are two types of BEMF, one of the types can count motor rpm and I forgot the other. The type that can count motor rpm can sync driver revolution very accurately given a CV for driver size and _maybe_ gear ratio. From here on out it's just a matter of good software, speed, drifting, pulling, etc. The Soundtraxx units have a CV for driver diameter but not having other sound decoders I am not sure how they work and what type of BEMF they use.

sound modules do not have a clue about how a steam locomotive operates nor what one is supposed to sound like< I think many do _but_ there are variables such a memory size and software design work. QSI should be capable of some really good stuff as the chip is huge compared to others (I assume that means a large memory area). I think it's really a matter of design but remember people want to stuff these units into N scale so the chip size is limited (memory limited also). There is also the cost factor but as telephones get smaller and smaller our sound units _should_ get better and better as a lot of the components come from this industry.

No. it looks to me like a "Me Too" product. The Digitrax sound module ~might~ be a contender for some diesel sound effects as it has a number of user configurable/definable inputs. We shall see what we shall see. Froggy,

Which brings up the fatal flaw in the whole concept, i.e., it is impossible to scale sound. No matter where you are in the railroad room, you can hear all the whistles and bells at once. The more locos you have with sound, the worse the din becomes; which prompts me to ask the question: ". . . Other than that Mrs. Lincoln, how did you enjoy the play?"

The only acceptable place for sound equipped locos is outside in the 1:1 scale world of prototype railroading. Bringing sound indoors in a model world is a no-win situation.

Froggy,

.snip

Well said. Froggy,

Don't know Mark. I no longer drive trains and haven't for quite some time. My interest in things railroad does not extend into the minutia of things such as the inner workings of air brakes, especially in today's context. That does not mean that I do not know how to use air brakes, or what makes them work, it just means that beyond describing the engine driver's duties and actions in the use of brakes in the handling of a train, I should leave more detailed explantions of the interior workings of the things to the people who actually maintain and repair them. I have a bunch of air brake manuals from Wabco, New York, and others that I have collected over the years, but I have never found them to be especially interesting reading. I have a friend who still works for NS. He is a former engine driver who now works in the car department. He can answer all your questions. I will ask him when I see him next weekend and post the reply later.

Froggy,

Froggy @ thepond..com wrote in news: snipped-for-privacy@news.east.earthlink.net:

Lately I find myself starting a train with the sound on, having a little fun with the bell and whistle/horn, then as soon as it gets out of sight, I hit the F8 button to mute it.

I'm still laying track and looking for any rough spots and it is tough to hear a truck start to drag with all that racket going on!