2P TTS sound problem - Adjusting Chuff Rate.

[Chrissaf]

This is a common TTS complaint. There is no facility for matching up rpm's and chuffs.

TTS works ok for diesels, but is a lost cause for steam outline, as far as I'm concerned..

[Howbi]

That is how it is with TTS but it's not so bad as you go up through the speed steps.........to get synchronised chuff you have to pay at least £70 up to £100 for the more capable sound decoders from Econami, Zimo & ESU for example.........HB

[KiwiKen]

Update: after a bit of reseach i now know the chuff rate etc. can be changed, i now have 4 beets per rev,  sort of. it certainly sounds better. I do not understand why Hornby do not provide this info.

CV56 - Chuffs per wheel revolution. 2 & 4 cylinder locos chuff four times in each revolution of the driving wheels, 3 cylinder locos chuff six times per revolution. This CV also set the type of whisle

2&4 cyl 0= plain whisle / 1= chime. 3 cyl 2= plain / 3=chime.

CV47 Fine tuning the chuff rate. Run your loco very slowly and count the number of chuffs in each wheel revolution to verify that it is four or six, depending on the number of cylinders as above. If you are getting too many chuffs per revolution then reduce CV 47 down from its default value of 128. If you need more chuffs per revolution then increase CV 47. 

you can also futher fine tune with CV's 2,3,&4

[Fishmanoz]

I am amazed. Chuff rate is a long-documented shortcoming for TTS that no one has previously solved. And for good reason. There are no documented CVs for adjusting it.  In particular, the 2P brochure does not mention CVs 56 and 47, or even the very basic CV2 as being supported. 

 

So where did you find the answer Ken?

 

PS.  Could a Mod please change the title to 2P TTS Chuff Rate for easy searching on chuff rate for future reference. 

 

PS2.  For future reference for posters. A topic title that says “I have a problem” isn’t terribly informative. A title that says “I have a chuff rate adjustment issue” says everything. 

[Chrissaf]

I have a new Hornby 2P class loco with TTS sound, the sound is awful 1 chuff per wheel revolution. been through the manual there does not appear to be any provision for reprograming this. Other brands of sound decoders the chuff can be syncronized with the wheel diameter. Anyone have a solution, or will i have to continue running this loco with the sound turned off, very disappointing.

[96RAF]

I have just tried this out on a TTS Coronation and a TTS King (being the only 2 TTS steamers I have with me) and I cannot see one iota of difference no matter what value I input to CVs 56 and 47. The chuff rate remained constant - ill matched wheel to chuff at the very low speed step set.

 

Nor can I see how changing a CV (I don’t know what these CVs control) can invoke a different sound set (whistle types). The burnt in once architecture of TTS sound is such that it is not possible to remap sounds.

 

CV2 kick start is not adjustable and CVs 3 and 4 accel and decell only serve to alter the chuff start if set away from the default (value 15) timing such that cylinders blow down then chuff begins As the loco moves. A higher value will mean the loco could start to move before the chuff and a lower rate will start the chuff before the loco moves.

 

Neither CV47 nor 56 will readback a value on my Elite so there is no confirmation a new value has been accepted.

Rob

[96RAF]

It makes me wonder if this is not a TTS decoder at all.

Can you please read and post here the values seen in CVs7, 8, 156, 157 and 158.

..thanks Rob

[St1ngr4y]

@RAF96

 

I concur with your findings, Rob. I just tried this out on one of my TTS steam locos. Railmaster does not allow changes to CVs 47 or 56, and when read directly by the Elite, a value of XXX is returned. I didn't try writing a value to them just in case, as I wouldn't know what value to reset them to if the changes didn't work.

Also, I would guess that even if you could change the chuff rate at the lowest speed, then the chuff rate would not increase at a steady rate during acceleration. The chuff rate seems to increase when the loco reaches certain speed steps. I haven't measured exactly which speed steps, but for example, it could be every 10 speed steps, the chuff sound starts up a new part of the sound file.

Ray

[Howbi]

Just checked my 2P tts. No readout from CV 56 or 47. CV s 3&4 are Accel & decel...... That is definitely not a TTS decoder..... HB

[96RAF]

Agreed Ray

Keep this in mind...

Generally there are 18 TTS steam sound bytes (say chuff brackets swapping every 12-13 speed steps) from stop to max chat, swapped in sequence as the motor achieves a target speed step as notified by BEMF.

 

I quote my notes...

‘... it is BEMF that governs the chuff rate bracket change ... in that the chuff rate will follow the actual loco speed and load, not the set speed step value which does not necessarily reflect the actual speed of the loco.. i.e. if the loco is under load or coasting or on a trailing throttle....’

 

Say apply max throttle and the chuff will cycle up as the loco hits an equivalent speed step and confirmed to be on load by BEMF. Once a set throttle is hit then BEMF backs off and the chuff alters to suit. Back off the throttle and the loco coasts until BEMF tells it to apply steady load again.

 

From this we can assume that one may see an apparent variation in synchronisation at certain speeds if certain CVs are altered (accel, decell, bemf), but these are more likely to be due to BEMF effect and certainly not CVs 47 and 56 which should have no affect on a TTS decoder.

 

Rob