East Coast HST at York
|DCC Sound update for the Hornby Cross Country Class 43 HST Power car and Trailer Car|
This page initially explores how a sound system can be added to the Hornby Cross Country liveried HST. Once a way forward has been decided, the details of the implementation will follow.
|The first challenge is to
identify how a suitable speaker can be accommodated in the Power
Although there is quite a large available space at the rear of the car, there are no external vents to get the sound out efficiently and so other options are addressed.
The fan vents in the roof plus the upper regions of the side vents would enable a speaker to work successfully if placed where the fan drive mechanism is currently positioned.
Alternatively, the lower moulding between the bogies could accommodate a downward firing speaker.
Top view of the fan assembly
The motor would probably have to be removed to gain access to the screws which I guess are holding on the lower moulding.......
WRONG! ...... In fact the fuel tank moulding is clipped to a solid metal extension of the chassis block....no room for a speaker here!
So the upper speaker looks to be the only viable solution. The fans could be retained if fitted on a plasticard bridge between the speaker and the roof.
The trailer Car:
No problem here, but I'll use a similar speaker arrangement to match the sounds at the front and rear of the train.
I'll mount the speaker on the chassis, facing upwards towards the fan grills and remove the original fan tray, using a new bracket to support the fans, that lets the sound escape through the grills.
|Time to go and take a
listen to a real MTU engined HST at York Station:
No Cross country HSTs today (all Voyagers while I was at the station). However, plenty of East Coast HSTs (with identical sounds) coming through.
The non-stop London train at platform 3
|Getting a bit closer to
This time, listening from platform three, near to the lead power car stopping location.
As you might expect, standing immediately next to the power car, the increase in volume level is more significant, as the engines wind up, but as before, the revs increased, but not a lot. The departure was again smooth and drama free.
|Choice of Sound Decoder:
This turns out to be somewhat more straightforward than expected as the only MTU powered HST sound decoder I can find available currently is the Olivia's Trains LokSound 4 offering. So I've phoned through an order for the lead car variant 2pm on 27th November (including a 20x40 speaker) and it won't be long before I see how it compares with the real locomotives... I hope! ..........If all is well, I'll order up an additional rear car variant later.
Well, that's what I call a fast response! Decoder & speaker arrived 28th November! The speaker provided was actually a DCC Supplies 20x40 unit, so I've ordered up the slightly larger ESU unit from Digitrains, as I know this has good performance from Class 150 experience.
(There are several sound decoder offerings available for the now obsolete Paxman Valenta powered HSTs, but although more spectacular than MTU sounds, these are just not correct for todays' HSTs. )
|Fitting the speaker in the
Before: Original LokPilot decoder and fan assembly in place.
First the original LokPilot decoder was removed, then the fan drive housing could be unscrewed and extracted. Finally, the fans were removed, ready to be included in the new assembly if there is room.
Static fans glued in place
Oops! Now I've dismantled the power car, I can see why Olivias provided the smaller speaker..... the frame bulges in immediately in front of the fan drive box, so to fit that ESU enclosure directly below the fan grills I am going to have to carve some holes in the plastic box then carefully seal them. Alternatively, I think the speaker enclosure will fit without modification a little further back. If positioned with a slight forward tilt, it should stay clear of the rear bogie gear housing and have a wider air path to the grills.
Showing where the internal frame width is reduced next to the flywheel.
|Fitting the New Parts:
Connecting the decoder function wires:
This is the first HST Power Car I modified and has a very simple circuit as I modified the Hornby lighting PCB to convert it from negative to positive ground. The circuit is shown below:
Fitting the ESU Speaker and decoder:
The wires to the rear wheel contacts are slightly repositioned to enable the speaker to be slid into position, glued and wedged between the frame sides using thin sheets of plasticard. There is just room to accommodate the decoder on top of the already modified Main PCB assembly. The decoder and wires are held in place using thin electrical tape.
Speaker mounted partially between the frame sides at a slight angle
Top View of the power car before re-assembly
The orange decoder wire parted company with the decoder as I arranged the wires, so this had to be carefully soldered back into place.
The bass response on the ESU speaker is much better than that of the 20x40 speaker that came with the decoder, so the extra effort to accommodate the bigger speaker was well worth while.
|Re-mapping the buttons for
the Power Car LokSound Decoder:
One essential change is to provide a button number within the range 1 to 12 for night running lights, so that the trailer car FL4 can be switched with the same button. Shunt mode and Zero CV3 & 4 mode are also added.
First the sound slot numbers are found by interrogating the 3 CVs assigned to each sound trigger button. The sound slot numbers appear in column 3 below. Only a few changes are proposed (outlined in the right hand column.)
LokSound CV Changes Required:
The detailed changes in CV values can be established using the data in the ESU LokSound manual, which now provides a comprehensive programming guide.
CVs for the FL4 in the rear car (pending possible second sound decoder fit):
The original arrangement used button 1 for night running lights. The new mapping uses button 11, so a few changes are needed.
(Plus address reset to 3 to match power car.........All now working OK.)
Sound Level adjustments:
Each sound slot can be independently adjusted for volume:
The completed power car on the programming track (part way through optimisation).
The fader is converted to an inverse fader to simplify volume boost at platform departure under computer control.
The Olivia's settings were a bit on the fast side, but curiously, transferring in my original LokPilot values, the loco moved too slowly. So I've reset the relevant CVs as follows:
CV3=40, CV4=24, CV5=120, CV6=40, CV53=140
Scale max speed = approx 100mph
Resetting the max speed on Traincontroller to 97mph, the loco stops at exactly the right point near the end of the platform. I've increased CV3 to 60 to make the acceleration a little more gradual, without causing any problems.
The start delay with sound active is approx 14 seconds (during which time, the engine sounds simulate the pre-departure power-up process).
It takes about 15 seconds for the engine start process to complete and I found that the loco needs to be stopped for at least 20 seconds before stopping the engine results in a believable sound sequence.
The real engine is relatively drama-free as the train departs, and I think the Olivia's sound is pretty close. However, I'll experiment with making a small increase in the master volume about 4 or 5 seconds before the loco moves (using the LokSound fader function). I can mask a return to normal volume when the train stops, using the air release sound slot........ This works fine, but its debatable if its necessary!
Results are good enough to add another sound decoder to the trailing (dummy) power car..... so the order went in today!
|"Stay Alive Capacitors"
There is plenty of room at the rear of the power car to add 3 or 4 1000uF 25V capacitors to keep things going in the event of a brown-out due to track problems. The trailer car has even more room, but 2000uF should be sufficient there (no motor).
Showing the wired connections that need to be added. (Only the GND needs a new connection as U+ is also the common positive blue wire)
|Stay-Alive Capacitors in
the Power Car:
Ground wire soldered to the decoder
4000uF of 25V capacitors filling the available space at the rear of the car.
Unfortunately, the body would not refit on to the chassis with this arrangement, so I had to fix the four capacitors into the rear of the upper body shell instead!
|Trailer Car Circuit:
The Circuit diagram for the trailer car, now also equipped with a speaker and LokSound decoder, includes a 100 ohm load resistor which is added between the otherwise unused motor contacts, to enable programming.
Circuit diagram of the trailer car, now equipped with a LokSound Decoder
Ground wire soldered to Trailer Car decoder
|Trailer Car Lower Deck
The ESU 50334 speaker enclosure is mounted on the ballast weight plate, directly below the fan vents. (Plasticard spacers are used to clear the ballast weight fixing screw and the inside edge of the two screw towers on either side of the speaker are filed down to keep them vertical.)
The decoder is fixed to the top of the ballast weight using a double sided adhesive foam pad. (This will be below the main PCB when it is refitted).
Two 1000uF capacitors are connected in parallel and mounted at the rear of the car, to keep the sound chip alive in case of track brown-outs.
|Trailer Car, upper deck
The Main PCB is refitted and the decoder function wires are connected as indicated in the circuit diagram. As can be seen above, the fans have been fixed in position within the upper body shell to retain the original appearance.
100 ohm resistor motor substitute, only connected when programming, tucked away
out of sight on the loco underside (before being painted matt black).
|Trailer Car CV Changes:
Next, I'll run both power cars under computer control and see how they sound.
|Running both power cars:
That's interesting....... I've got both the real and the dummy power cars on the track and several of the sound effects are direction specific. The horns and right away tones are much louder on the forward facing power car, while the guard's door slam is much louder from the rear power car. Nice touch!
In fact, I've now updated the CVs to only activate the horns and right away tones in the leading car, while the guard's door only slams from the rear car now.
The power cars work well under computer control, where I have now removed the volume boost when the train prepares to depart the platform.....its not really needed!
I did briefly consider adding hazard lights and interior lights to the 5 Mark 3 coaches that form the rest of the Cross Country HST Train as an extension to this project, but decided that this can wait til another time. So.....Project complete!
For a YouTube video clip of the finished HST pair operating on the test track, please click here.
Improved speaker fit starts here.......
sound in the lead car:
The video demonstrates an interesting difference in the sound quality between the lead and rear power cars. The speaker and enclosure is identical in both cars. However, the limited space in the lead car did not enable the speaker to be installed directly below the fan vents (as accomplished in the rear car). The frequency response of the rear car seems to be lower, giving a richer engine sound.
Yesterday, I came across a video on YouTube suggesting that the use of a sealed enclosure is not always the best approach to model rail speaker fits. So I've decided that its time to experiment with an alternative approach.
I'm planning to try the same 20x40mm drive unit, mounted on a new baffle directly below the fan vents. The new baffle will also box in the duct up to the fan vents, sealing the top of the duct to the roofline on the loco upper body shell. By not using a sealed box under the speaker, I think it will fit above the chassis unit. The side vents below the fan vents will be covered using electrical tape. I'm hoping that the entire loco body will provide a form of reflex enclosure, but it will be shear luck if the sound leaking out around the bogies arrives in phase with that directed out of the fan vents!
Cross section of the lead power car, showing the original speaker location and the planned update.
|A new speaker fit in the lead car:
The modified speaker installation, uses an identical ESU 50334 20x40mm drive unit to the original. The photos below show the fan vents complete with fan support bracket, the new baffle assembly (which needs to keep the speaker cone clear of the fan bracket) and the new speaker in place:
The fan vents complete with non-working fan blades and supporting bracket
The new plasti-card speaker baffle shaped to fit the roof underside and clear the fan assembly.
The parts that will be visible through the fan vents are painted matt black.
Speaker drive unit placed on the baffle before being glued in position and sealed
The speaker, glued and sealed to the baffle, showing the cone which faces the fan vents
After gluing in place with liquid poly, the baffle is sealed against the roof using "Glu n' Glaze".
The sound quality from the new arrangements is a significant improvement in tonal quality over the original and is also noticeably louder.
Comparing the new power car solution to the original trailer car speaker, it now becomes more apparent that the trailer car frequency response is lacking in the mid to top region. The horn and "right away" tones are reproduced much more loudly and with significantly better subjective quality, by the new power car speaker system.
So, only one conclusion....... A similar mod is required for the trailer car too!
To watch a test track video of the HST loco pair with the updated speaker arrangements, click here
Unfortunately, the Youtube video doesn't really show the sound improvements via my camera microphone as well as they sound through a pair of human ears......but at least its a record of a kind.
And that really does complete the project......... at least for now :-)
|0 Forward||Day H/L + Mkrs forward|
|0 Reverse||Day running reverse|
|1||Power Car Engine start|
|2||Single Tone Horn|
|3||2 Tone Horn|
|7||Right Away buzzers|
|8||Rear car engine start|
|11 Forward||Night running forward|
|11 Reverse||Night running reverse|
|17||Zero CV3 & 4|
|Supplier website links:
These will be added or updated as the project progresses.......................
The photos of the model were taken using a Canon Ixus 220HS on the kitchen worktop, sometimes with on-board flash.