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Doehler & Haass chuff sync


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  • RMweb Gold

I have a Doehler & Haass SD18A with a steam sound project and I'm trying to sync the chuff rate to the host loco but it has defeated me so far.


The D&H manual says that CV353 sets the chuff rate at speed step 1 and then CV354 adjusts it for higher speeds but the decoder behaviour at speed step 1 is not consistent:

  • If I start the loco from 0 and go up one step (1 of 128) it makes no chuff sounds at all, no matter how many wheel revolutions I wait.
  • If I accelerate up to a higher speed and then come down to speed step 1, the coasting sound stops responding to loco speed and just runs at it's own independent rate.


So it seems to be impossible to sync chuffs at speed step 1...?

I'm trying to set CV353 first and then adjust CV354 because that is the strong suggested method from the descriptions of the two CVs and empirically trying any other 


It's possible that some other threshold setting in the decoder is preventing the chuff rate from responding to loco speed at low speed inputs but I can't immediately see what.


It's also possible, I suppose, that by "Speed step 1" they mean 1/28 rather than 1/128...? That's not clear but worth a try.


Does anyone have experience of these decoders and setting the chuff rate?



Update: While writing this, I've realised that I should probably try setting VHigh to max and setting a linear speed response.


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  • RMweb Gold

After another session of fiddling at speed step 2/128 with a linear speed curve, I do at least get chuffs that seem to be related to loco speed.


Having set CV353 to a reasonable sync at speed step 2 I then speed up the loco and set CV354 to get good sync at the faster speed. But that then throws out the sync at low speed, etc., in an endless spiral of doom.


Man, this is frustrating!


At the moment I don't think it's actually possible to get a decent chuff sync across a range of speeds with this decoder.


Edited by Harlequin
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Since this is not an ordinary German D&H project, but Locoman's, I took a look at Locoman's website, and voilà: technical information->CV list->CV353 at speed step 2.

And I'm very sure it's 2/28.
For me it's an iterative process, which means switching between CV 353 and 354 again and again, 3 or 4 times.

I usually test with speed step 2, 6, 10, maybe 12, at most 14.
At higher speeds you can't see it clearly anyway. I use PoM to set it up and it usually takes 5 - 10 minutes.

The last step is to adjust CV 362 to limit the chuff rate at very high speeds.

By the way: a real locomotive can only maintain such a low speed for a brief moment as is achieved (on a scale) with the D%H decoder at speed step 1. At least you won't hear any chuffs on the real thing, so it seems reasonable to me that no sound can be heard on the model. Just switch on F5 and it sounds realistic for me

  • Agree 1
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  • RMweb Gold

My decoder is installed in a batch 1 Dapol Mogul, which has very high gearing so the default values in the Manor project don't apply.


I have managed to get a reasonable sync while CV5 VHigh is set to the default 92. I would like to lower it because of the high gearing of the loco but when I did that things seemed to be less predictable, as described above. I need to go back and re-test that.


The speed curve as set by CV48 is the cause of the lack of chuffs when accelerating up to low speed settings and of the "free-wheeling" chuffs after decelerating down to low speed settings. The flat start to the curve seems to fail to trigger the chuff counter. Seems like a bug to me.


By setting a linear curve (CV48=0) I was able to set up a decent chuff sync but I have subsequently reset the speed to have a shallower curve to get more natural starts. Chuffs don't start below 2 but when driving for real you quickly pass through that zone and don't notice. With the revised speed curve the sync remains the same as with the linear curve - I half expected it to go out of whack.


The Acceleration and Deceleration rates can also be changed without affecting chuff sync, thank goodness.


So I have something that works OK for now but the loco is way too fast. That's the fault of the loco but I hope I'll be able to adjust the decoder to compensate for it and setup a decent chuff sync.


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Cv3 and Cv4 do not influence the chuffs rate

The value corresponds to the time in seconds from start to max speed 

The value of Cv4 again corresponds to the time in seconds from max speed to stop

Cv9 changes the motor frequency and sometimes it can be helpful 

All details are published on our website at the main menu bar at the Technical Info

The problem is that most of clients do not take notice of reading the manual of instructions which could reduce frustrations

When Phil received our decoder he noticed an electrical pop sound in the file perhaps due to a memory flash of the decoder in subject which thanks to his patience was rectified by a new reblow and he now seems to be satisfied for the result 

The process of a chuff rate sync can take quite a few minutes and sometimes can be quicker than other times due even to the motor of the model train

We tested the same decoder with the same values on a Bachmann model and immediately the chuff rate was not in sync but the decoder was responding at its best just like when it was connected to a similar Hornby model although once again the chuff rate needed to be readjusted 

We are thankful to all our clients for their understanding and cooperation 

Edited by Locoman58
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  • RMweb Gold

Sorry Alex, I read through the D & H manual but I can see now that you have extra information on your website that would have been helpful.


I didn't realise it was there and it might be a good idea to refer to it in the covering material you send out with the decoder.

To be clear, I have no problem the sound project itself. The sounds are more realistic than others I have used and the dynamics of how they are applied during driving is very natural.


I think it's a bit odd that CV353 is defined as "Chuffs at Speed Step 1" and yet with the default speed curve you can't actually hear any chuffs at step 1. That's a D & H problem.


I will try again to get good chuff sync when VHigh is set to a lower value and will report back.


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