# Has anyone worked with the MRC 1908 sound only decoder?



## rreiffer (Jan 14, 2009)

Hello all,

I was wondering if anyone has experimented with the MRC 1908 (this is the new 16 bit unit that replaced the old 8 bit one)? Supposedly it is able to operate on large scale through the use of an 82 ohm resistor.


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## Dan Pierce (Jan 2, 2008)

All of the Large scale units by MRC have a 21 volt limit per their spec, and HO versions would be less. 
My opinion is use it for smaller scales, not large scale unless you can be sure about the max voltage rating. 

I do have the 1818 and it works on my 22 volt track (my MX1 has a 24 volt A/C input and 22 volts out to the track. No issue to date!!


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## lownote (Jan 3, 2008)

I'm tempted to try one, and just rig up a bunch of diodes to drop the voltage. The manual for the steam version says 15 volts, the manual for the diesel says 18. I'm going to order one and see what happens


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## rreiffer (Jan 14, 2009)

Ok, I am going to get brave (I ordered one). Not only that I am going to try the TDA2040V (20W) audio amp. I will let everyone know how it turns out.


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## lownote (Jan 3, 2008)

Yikes! 20 watts? In my opinion that's WAY more than anyone needs. How loud do you plan tio get?


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## Dan Pierce (Jan 2, 2008)

If using a 20watt amp, make sure you have a speaker that can handle it!!!


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## Trains West (Oct 4, 2008)

and don't hook the amp straight to the speaker output ....


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## rreiffer (Jan 14, 2009)

Ok all, don't worry about the 20W amp, that is the rating of the IC I am using. Just because a car can do 120MPH does not mean I have to run it at that the whole time (nor would I)








 The fact was that this single chip was cheap (there I go again) and I will simply use a fraction of its capabilities which means it should run pretty clean and still hear it across the back yard.


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## Greg Elmassian (Jan 3, 2008)

right on Rich... people have no idea that it takes double the power to increase sound by 2-3 db. 

run a 20 watt amp at lower output power, lower distortion, etc. 

Greg


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## lownote (Jan 3, 2008)

I understand perfectly well about the relationship between watts and decibels. 20 watts is enough, in a guitar amp, to, say, to entirely drown out conversation in a bookstore without distortion.

There's obviously no reason why you can't have twenty watts--there's no reason why you couldn't put a class digital switching amp in a boxcar and have 350 watts, I suppose. It just seems like overkill, unless you plan to run the train in a crowded bar and you want everyone to hear the sounds above the level of conversation. In my opinion, anything over 5 watts is overkill, and it's more important to pay attention to the speaker, in our application, than to the wattage. Just my opinions. I think it's neat that you are trying it. 


Good luck with it, I'll be delighted to hear how it works. I hope it works well and gives you exactly the results you want.


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## rreiffer (Jan 14, 2009)

All, 

Actually it wasn't the fact that it had 20watts of capability (I was looking for something smaller) its just that the full ic amp was.only $2 each! (there I go again, being cheap) I will let you know how many speakers I blow out!


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## Greg Elmassian (Jan 3, 2008)

the extra "headroom" in the amp lowers distortion, if you have good ears, you can tell the difference. 

If you research a little, you can see that certain sounds can require a peak (although brief) of 1,000 watts to reproduce completely (a handclap is a good example)... 

Now most of the time, a lot less power will do a "good enough" job. 

Many people can not even "hear" harmonic distortion, and others (like me) hear it right off... 

So 20 amp capability running at 1/10 of an watt most of the time can be an improvement over a 1 watt amp... even though you are not running an average anywhere near the max. 

These sound discussions usually swirl around and around since each person's perception is different. 

Regards, Greg


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## Trains West (Oct 4, 2008)

what i ment is you will blow up the decoder by grounding out the speaker output .... you need to add an isolater transformer


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## Greg Elmassian (Jan 3, 2008)

Scott, are you worried that one of the leads to the speaker is also grounded? 

I have not seen that in any LS loco yet, but I have not torn apart a lot of LGB sound equipped locos. 

Greg


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## Trains West (Oct 4, 2008)

greg this is mrc not lgb ...... and the input to most of those amps have a ground so when you use the output of the mrc as the input to an amp you will put a ground on the mrc speacker output 


you on the right thread ?


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## Greg Elmassian (Jan 3, 2008)

right thread, was thinking on the speaker side, never seen a speaker grounded... racking my brain... 

on the input side, yeah, I getcha! 

Greg


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## rreiffer (Jan 14, 2009)

Quick report on the 1908 sound decoder. First pass: it comes with an HO size speaker that in and of it self is not really bad. Now a Phoenix it is not, however it is full DCC and seems very decent. You can vary a lot of the sound and customize fairly easily. Now I did disconnect the speaker that comes with it and hooked up a decent speaker and the sound improvement was very noticeable. As far as volume it was enough to have my wife say "will you turn that thing down!". A very nice sound decoder for $34! I'll be testing it further with some of the options later. Once again, because it is MRC you should add a diode drop to keep the voltage safe.


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