Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: pakirk on December 27, 2007, 08:31:26 PM

Title: Sound units, your thoughts
Post by: pakirk on December 27, 2007, 08:31:26 PM
Sound units, your thoughts
Hi all.
As you may probably know I am developing new sound units to replace the missed JJC units.

I need your input.

The AMP as you will know from the JJC units get quite hot.
There are several options to cool them I would like you thoughts.

Heat-sync:- To do this properly a LARGE expensive heat-sync is required, this is because in a model there is no air flow to cool the heat-sync.

Force cooled FAN:- This is another option witch reduces the size of the Heat-sync required. But increases the maintenances. These fans are only designed to run <4000 hours.

Water cooled:- Small compact reduces cost. The down side is, you need a pump and plumbing is not everybodyís cup of tea. Pumps and water lines also clog up.

What would you prefer??
Title: Re: Sound units, your thoughts
Post by: DickyD on December 27, 2007, 08:35:05 PM
Something similar to the JJC, they work OK in my GRP hulls. O0
Title: Re: Sound units, your thoughts
Post by: John W E on December 27, 2007, 08:35:28 PM
Hi there

What size wattage output are you talking about?  ..... when you say you will need a huge heat sync?

john e
Title: Re: Sound units, your thoughts
Post by: red181 on December 27, 2007, 08:42:23 PM
my short experience with 2 x jjc units was that they where VERY VERY hot, too hot to be comfortable in a wooden "damp" boat. Water cooling would be fine with me as my boats are water cooled anyway, and a fan would be fine as I have plenty of room, an old computer fan works fine!
THe sooner they are on the market the better, but I would like to hear them, dont want the robbe "angry wasp" sound!!
Title: Re: Sound units, your thoughts
Post by: funtimefrankie on December 27, 2007, 08:47:22 PM
Surely a computer fan would last years in a model boat, a model boats run hours must be far less than a computer.
Title: Re: Sound units, your thoughts
Post by: pakirk on December 27, 2007, 09:07:31 PM
WOW quick response.
DickyD, nonít mean to correct you but a can assure you they get HOT. I have over 50 JJC units in for repair. Most of them and amps are burn out with heat, some the PCBs have charred.
Philips recommend a very large vary large heat-sync 60x 75x10mm.

Bluebird, Not an easy question to answer. The max on the basic model I am doing is 15Wats using the same AMP as JJC did ďNice AMPĒ.
The wattage actually disperses varies to the sound frequency and amplitude , voltage and speaker.  The lower the frequency and larger the amplitude the higher the wattage.

People want the lower frequency to get that rumbling thumping effect.
The JJC Turbo-Cat had the lowest Frequency and the larger amplitude and dispersed approx 12Watts of power and got extremely HOT.

Title: Re: Sound units, your thoughts
Post by: longshanks on December 27, 2007, 09:54:37 PM
Hi Pakirk,

Great to hear they may be a replacement coming for JJC sound units. I was looking to buy when I read on this forum it seemed to be going pear shaped - thanks guys.

Vis yr question (might be a dumb answer) is it possibe to offer perhaps a couple of options at time of purchase or will this push the cost up.

Regards longshanks
Title: Re: Sound units, your thoughts
Post by: banjo on December 27, 2007, 09:58:58 PM
An enterprising fellow should be able to incorporate the "very very hot" heat sink into the pipe of the smoke unit and produce a "Sound & Smoke" unit???

Title: Re: Sound units, your thoughts
Post by: Stan on December 27, 2007, 10:17:30 PM
Hi Guys .

Surely is it not possible to incorporate a small tube  built on to the sound unit amp.Water could be taken from a scoop in front of the prop/props  around the unit and  out of the hull . This is not rocket science  one electronic manufacture already  fits these pipes allowing units to be water cooled. :-\ :-\
Title: Re: Sound units, your thoughts
Post by: Colin Bishop on December 27, 2007, 10:22:58 PM
I confess that I'm pretty ignorant when it comes to electronics but generating heat on the scale being talked about here suggests that there is a significant degree of inefficiency in the system. We don't have to watercool our home cinema systems do we? (not that I've got one!)
Title: Re: Sound units, your thoughts
Post by: Martin [Admin] on December 27, 2007, 10:48:34 PM

How about a setup where there is fixed small heatsink where we can bolt on a range of options large metal plate, multi-finned compact heatsink, water cooling, fans.... anything we wanted, recommend or supplied as an option.
Title: Re: Sound units, your thoughts
Post by: cos918 on December 27, 2007, 11:17:03 PM
if you had a fan would this run off the drive bat? as modlers use diffrent voltage to drive boats.
Personly the only down side i see to a fan or pump is current draw. Heres a possible scene the unit is cooled by a fan or pump. Shortly after your boat put to sea say for an hour the cooling fails .Say batter low etc how long before the unit will be cooked.
So on that thought i think a heat sink might have an advantage, will this work in a small space of say a small packed hull.
Title: Re: Sound units, your thoughts
Post by: Bunkerbarge on December 27, 2007, 11:55:30 PM
Colin has a fair point there.  Instead of looking into ways of dissipating the heat it would be a lot more productive to be looking into ways of not creating it in the first place.  Not only is the heat itself undesirable but it is an obvious waste of battery power.

The question then has to be what creates the heat and how can it be reduced?  How can the electronics be redesigned to reduce this heat generation?  That would be a major step forward.

As for using a smoke generator to cool the sound unit, if you heated the cold water vapour you would evaporate the moisture droplets and reduce the effects of the smoke.  It may however be usefull to pre-heat the water in the reservoir to make evaporation easier.
Title: Re: Sound units, your thoughts
Post by: malcolmfrary on December 28, 2007, 12:07:16 PM
The poblem is that we are using what is basically an analog amp designed for HiFi use.  Heat production is not usually an issue, but the instructions usually advise not blocking the airvents, and power used is rarely a problem as they are usually mains powered.  We have an enclosed box with a batery for power.
Mphmph years ago a young Clive Sinclair marketed a PWM amplifier that was "95%" efficient.  It ran on 12 volts and shoved 10 watts into a 16 ohm load.  Bass performance was terrific - distortion at higher frequencies (it only sampled at 40K) was not good, so other products that produced nicer sounds won out.  It was physically large by todays standards, but it pre-dated chips and was stuck with early 1960s transistors.
It should be well within the bounds of possibility for one of the PIC wizzerds out there to program a PIC to be a PWM amplifier - all that is needed for the output then becomes four nice big transistors which just switch on and off, with much reduced heat production.
Title: Re: Sound units, your thoughts
Post by: Subculture on December 28, 2007, 01:26:02 PM
If you're developing new design, why not take a look at class D amplifier chips-,2879,759%255F1075%255F0%255F%255F0%255F,00.html

Upto 25 watts, no heatsink required.

Title: Re: Sound units, your thoughts
Post by: malcolmfrary on December 28, 2007, 04:21:09 PM
They look like really handy devices. O0  You just need a job for the other channel if you cant parallel them up....... :-\
Title: Re: Sound units, your thoughts
Post by: wombat on December 28, 2007, 04:45:02 PM
If you're developing new design, why not take a look at class D amplifier chips-,2879,759%255F1075%255F0%255F%255F0%255F,00.html

Upto 25 watts, no heatsink required.


Scanning the data sheet, not sure I agree - looking at the integrated 25W unit, you can be dissipating up to 6 watts in the device - it will get quite sweaty without heatsinking. Saying that, class D has to be the way to go for small, high-effciency amplifiers. Remember to leave space for the output filter too  - that can be as big as the actual amplifier!

Title: Re: Sound units, your thoughts
Post by: Subculture on December 28, 2007, 06:03:52 PM
But wouldn't that be at maximum duty?

I think it's unlikely the amp is going to be used like that.

Title: Re: Sound units, your thoughts
Post by: malcolmfrary on December 28, 2007, 06:16:09 PM
If it is going to handle large engine sounds, a healthy continuous rating will be needed.  Intermittent sounds like ships horns, less so.
Not too sure about just how needed the filters would be for boat use.  In the old Sinclair design, a lot of reliance was placed on the mass of the speaker to sort out high frequencies - the only time that the use of filters was mentioned was where a tweeter was being used, and we are not really into that kind of thing.
Title: Re: Sound units, your thoughts
Post by: red181 on December 28, 2007, 06:41:30 PM
I have heard of some people using cheapo mp3 players. Can the sound not be reproduced somehow one one of these, then the speaker plug in options are huge, depending on the size of the boat, and mp3's dont get hot, and are small. AS posted previously, surely some pc boffin out there can come up with a remedy
Title: Re: Sound units, your thoughts
Post by: wombat on December 28, 2007, 10:24:05 PM
But wouldn't that be at maximum duty?

I think it's unlikely the amp is going to be used like that.


Hi Andy,

Looking in a bit more detail, if it were me, I would be heatsinking - without even on moderate power the junction temperature will be running fairly close to the wind - all up thermal resistance of the case is about 22C/W. The package would be a bit of a swine for amateurs and small manufacturers to deal with (unless they have access to a decent SMT line).


I think that the output filter would be essential with one of these integrated jobbies - otherwise the inductive spikes caused by the speaker could play havoc with the output transistors. I think also you could find that any high frequency sound could be screwed.

Title: Re: Sound units, your thoughts
Post by: malcolmfrary on December 29, 2007, 10:57:08 AM
PMDEVLIN  -  For low power the MP3 players are great, but for all but the faintest sounds you need an extra amplifier to get the sound level required.  MP3 players are usually intended to drive headphones rather than loudspeakers.  There are some out there who want the same sound level as with the full size, and that needs pure brute thrutch.

Wom  -  I was just referring to the '60's technology.   Agreed the output transistors would benefit from being protected, but the capacitors shown would have the effect of smoothing off the high frequency edges presented to the speaker.  The speaker used in a boat would probably be a single unit with plenty of mass, and so any signal presented above about 3.3K would be attenuated.  In any case, the chip used to hold the sound sample would be one developed for voice recording, and so the output would stop there.  Real HiFi demands a response up to over 20K, far beyond most human hearing, and these chips were probably developed with this market in mind.  No values are given for either capacitors or inductors, but I suspect that they are small and aimed more at calming down the spurious responses to the amplifier's PWM switching when the speaker can respond to them.  I reckon that with a single knobbly speaker, no-one would notice unless the speaker leads were long enough to radiate RF.
The big trouble is that the price was quoted in batches of 1000+. 
In a boat, which is intrinsically a sealed box, any cooling will need forced flow, be it water or air.  For air, a computer fan, should do the job.  Even with a life of 4000  hours, thats 6 months running 24/7.  At a couple of hours a week, its a long long time, and if its made accessible for replacement.....
Title: Re: Sound units, your thoughts
Post by: Circlip on December 29, 2007, 11:24:27 AM
Come on guys, it's a b****y toy boat. you will NEVER get a true engine sound out of a three/four inch (OK 75/100mm) diameter speaker. Todays Youfs fall into the trap that loud is good and don't understand the QUALITY of sound. I suspect malcolm may have had some involvement with Hi-Fi so understands the principles. If you want the base response required to give a TRUE representation of modern diesels etc, you are going to need a speaker of AT LEAST 7"dia and the bigger the better. Yes I know manufacturers like BOSE have mini speakers but ALL of them use SUB-WOOFERS for the base units. Seen an electric powered DH Hornet with a HI-FI system built into it to emulate the sound of the Merlins, but it's 100" wingspan, and the amps heatsinks are aircooled, 2 X 40W amplifiers, gosh!
Title: Re: Sound units, your thoughts
Post by: bigfella on January 04, 2008, 09:13:03 AM
Hi All

Now I may be missing something here, but during the 70's I used to take one of those hand held transistor radios that used 9volt batteries to bed and listen to the top 40 before going to sleep. Many times I would wake up in the morning and the radio would still be going. My point is that the radio after 8 or so hours of use was never warm. Surely technology has not gone backwards. I also have one of those (what used to be called "Ghetto Blasters") that runs on batteries it never gets hot and is so loud that it rocks the china in the cupboard. These Ghetto Blasters also have motors in them to run Tape and CDs so power consumption is not a problem. I can not see any problem in utilising this type of Amp in a sound module. And before you mention about the bottom end why not use a low frequency speaker or even a full range one as most of these systems have.

Seams simple really

Regards David
Title: Re: Sound units, your thoughts
Post by: Shipmate60 on January 04, 2008, 09:52:35 AM
Haven't we lost sight of the forest for the trees here.
The sounds from a ship isn't the sound of the engines, if it was the crew would all be deaf!!
You hear the sound from the exhaust!!
The engine room is sound insulated, the only way to hear the actual sound of the engines is to stand beside them.
Can you hear a Steam Recip, NO. You hear the feed pump clanking. In a Steam Recip engine room you can talk without hardly raising your voice, so how does that translate to the external sound emitted from the ship. It doesn't.
The main sound from a ships exhaust is from the generators not the main engine(s) as they are smaller engines with a higher frequency.

Title: Re: Sound units, your thoughts
Post by: portside II on January 04, 2008, 10:22:32 AM
well said Bob
i have the turbo cat jjc sound unit and a while back i asked Jim (jjc) why that sound  and if he could do one with a bit more grunt ,the sound is taken from the engine room and not from outside the hull , would like one that has the sound from the stack's ,even if it does sound like the exhausts are blowing .
There is a small tug at goole (little shuver) that has a bige petrol engine in it and when working all you can here is this loverly purring sound  music to my ears .

If jjc has closed its doors what about the sound units and other products from him ,are they replicateable (can we copy them legaly) .

I mean the base of these devices is an eprom chip which can be read and duplicated ,legaly of course  ,and then fitted onto a board which has a purpose built heat sink .

Reading the posts on here there has been mentioned the use of water and air as a cooling solution but dont forget the transistor also requires heat to opperate efficiently and having cold water pumped around its extremities may actually be too much ,the heat sink is the way to go and it is also a good base to mount your module to the hull/whatever.
Title: Re: Sound units, your thoughts
Post by: malcolmfrary on January 04, 2008, 12:22:14 PM
The point about heat generated in olde portables - these were low power devices, intended for the listener to be quite close.  Even so, if you took the lid off and examined the output transistors with your thumb, you would note that you then had a sore thumb.  In the case of the ghetto blaster, the audio amps carried substantial heatsinks, and they were well vented.
If you want the sound of three Packard V12s a few yards away to realistically jiggle everybody's bowels in the open air, then you are talking POWER. 
A typical passive HiFi loudspeaker was deliberately made very inefficient, conversion was considered good at about 1%, and the rule of thumb for a given room was "10 watts per drive unit per 1000 cu ft per channel".  The open air is a BIG room. 
The speaker setups that we use are not HiFi, but restricted to "normal speech" plus maybe an octave lower, max 3.5KHz, min whatever can be managed.  We do not use multiple drive units and filters, so efficiency can be much higher (don't know, ask somebody else) and what is needed is a solidly built speaker (bass/lower mid) with a powerful magnet and long throw, and an amplifier built to drive it.  This for continuous loud sounds.
For intermittent sounds, the need is much less.  A speaker rated at a couple of watts can handle rather more in short bursts such as a ships horn.  An ocean liner would need to move a lot of air with the rather deep sound, a warship can have a much smaller speaker for the "whoop".  The speaker in my corvette is about 45mm diameter and the whoop can be heard over 50 yards away, about 2 and a bit miles in scale terms.
Title: Re: Sound units, your thoughts
Post by: bigfella on January 04, 2008, 12:45:43 PM
Precisely why you do not need to go too big on amplification. What you want is SCALE sound to match your Scale boat. I think if the sound module puts out too much sound for the size of the model it ruins the effect.

Malcolm: I used to work with PAs for bands and in the clubs it was worked out that each punter absorbed 1watt. Believe it or not some bands went to some gigs with only a 1000watt PA system where the crowd was just under 2000, and they wondered why they could not be heard.

Regards David
Title: Re: Sound units, your thoughts
Post by: red181 on January 04, 2008, 01:35:31 PM
bigfella dont forget we have to "overscale" our sounds as we have to overcome the noise of the electric motor, in my case a loud graupner, but good points raised
Title: Re: Sound units, your thoughts
Post by: tigertiger on January 04, 2008, 02:06:49 PM

I have seen small external speakers for laptops/mp3 that have two speakers of less than 2", run on 5.1v (from USB) and do not get hot. They were very loud, beefy with good base response and with internal amp. Total size for unit with two speakers was about 9" x 2.5" x 2". ( I did not buy this particular model as it was relatively expensive for China retail (about 20quid), so cannot give any more details.) What I can say is that they were not tru Hi-fi. But I don't think we need hi-fidelity for ship engine sounds, do we.

As for water cooling, as has been pointed out, you don't need a pump. there are units used for motors that work by differential pressure as the boat moves on the water. So unless you plan to be stationary, this would help.

Edit 2 post together - Admin.
Title: Re: Sound units, your thoughts
Post by: BlazingPenguin on January 05, 2008, 07:29:07 PM
dont want the robbe "angry wasp" sound!!
Ahem....I was taken to task for a comment like this, one rule for some, different for others?  :police:

I swapped the fitted heatsink for a section of extruded aluminium from an old roller blind chassis, no probs since, but it did get very hot before that.
I will be after someting like JJC's steam unit for a steam tug if your doing one like that?

(No woodpeckers were harmed in the posting of this reply)
Title: Re: Sound units, your thoughts
Post by: pakirk on January 11, 2008, 07:47:56 PM
Hello all
Well LOTS of exelent comments.
I will ready through them all and take note.

Thank you all
Title: Re: Sound units, your thoughts
Post by: pakirk on January 20, 2008, 04:04:00 PM
Well I have been very busy.
 Lots of prototyping and tested and experimenting with different ideas.
This is what I have settled on.
Big heat-sync - Expensive and bulky. >>:-(
 Water cooled- Erratic and unreliable works fine for ESCs but boat has to be moving or a pump running. Pump has to be filtered and clogs up easily. >>:-(
 O0 Fan force cooling. :D
Constant, reliable and controllable thumbs up.
Tests on the fan cooling was excellent reliable and neat.

The System
The AMP and sound units are separate units.
The AMP is in a 40x40x20mm based box (The same as my ESCs) with a 10mm deep fan.
15W power output to a 4Ω speaker running at 18V
I decided to design the AMP around a 4Ω speaker because they are more readily available 8Ω are getting harder to get. 4Ω speakers are used in cars. They are more efficient to drive from a battery system also. Hence why they are used in cars.
The input is correctly balanced to a Pre AMP driving the power AMP and has input and output filters.

The sound module is again in a 40x40x20 box. They inter-link into each other (NO LINK CABLE REQUIRES saving £3 a shot ). They also inter-link to the AMP unit.
For additional sounds simply add another sound unit next to each other. If you require more power then simply add another AMP unit.
If you do wish to separate them, then simply use a standard servo extension lead.
You donít require a servo Y slitter either again saving £3, your ESC plugs directly into the sound units.
The units are opto isolated from you receiver insuring no interference, as was experienced with previous sound units out there.

Many of you have JJC Slaves and canít use them because the master has packed in.  With a special conversion lead I do you can use JJC slaves with my system.....

Well they should be out on the market soon.
I have tried my hardest to keep the price the same as the JJC units (£40 for master), (£30 for slave), (£30 for AMP unit), (£3 for link cable and £3 for Splitter) , but there are lots more components evolved in my units plus a fan.

I donít have a Master as such; itís like the AMP unit and slaves. This is to give the users more flexibility.
So itís looking like this:
Sound Module £30
Sound module and AMP purchased together £45 
Sound and motion Module £35
Separate AMP £30
Bearing in mind you DONíT need a £3 Y splitter or a £3 link cable .
I hope very much to hear your comments.
Title: Re: Sound units, your thoughts
Post by: Martin [Admin] on January 20, 2008, 04:31:40 PM
Lot of work done there sir!  :o

We look forward to seeing hearing the prototype.
Title: Re: Sound units, your thoughts - solution already done!!
Post by: david.harrison on January 21, 2008, 10:23:52 PM
Guys, I would like to introduce my company - "Model Solutions of Canada Ltd." - (

We already have two different sound modules on the market and they are available today. They are WAY superior to anything else on the market, including those beloved JJC units!! There is no need for anyone to start developing a JJC replacement - we are already there!

They have a USB interface - you can download YOUR OWN sounds to them via a PC program that we supply with the module.

They use an extremely efficient Class D PWM power amplifier that delivers a full 12Watts of power into 8 ohms at 14V - i.e. a fresh 12V gel battery.

At 12V you can get 9 Watts and get this folks, NO heatsink, no fan, no heat - period.

Our current SFX4 series modules are 2.75" x 3.225" x 3/4"

They are at the higher end of the price spectrum CDN$169.95 and $139.95, but bear in mind what you are getting.

8 - 10 sounds
Total of six minutes of digital sounds
Full configurabilty via its PC interface
12Watts power - NO HEATSINK, NO FAN!!
Built in 16 channel R/C switch decoder
16 button keypad for the transmitter
8 auxiliary switched outputs
2 switched outputs can be configured to flash in sync. with any of the sounds
   (e.g. lamps in gun barrels) - completey user assignable.
USB cable
SFXPC application software + free sound editors - Audacity and others.

If you were to buy a 16 channel switch decoder from us , or other manufacturers, it would set you back CDN$150 just by itself.

The closest competitor to us is the Robbe unit at 135 Euros (CDN$203) and it only has six sounds, two aux outputs and IS NOT downloadable.

We are also developing some simpler, smaller, lighter, and cheaper units, our SFX5 series - availability May 2008.

Shipping costs to the U.K. CDN$56 - 5 business days, or CDN$30, 2-3 weeks.

1 CDN dollar is 50 pence.

Hope this helps.

David Harrison
Model Solutions of Canada Ltd. (