Project "Dictogrand Dictograph R-3 Horn Speaker" (1/2)

I won this obnoxiously big horn speaker on eBay and it finally arrived here on New Year's Eve all the way from the US of A. This is a Dictogrand R-3 Speaker made by the Dictograph company in 1923 according to the information on this renowned website (http://www.radiomuseum.org/r/dictograph_dictogrand_r_3.html) which makes this speaker about 90 years old. The horn is made of brass and is connected to a (cast iron?) elbow that links it to the speaker driver located in the rectangular box made of wood. It has a volume control knob on the front of the box where the brand is stamped.

The funny reason why I bought this obnoxiously big horn speaker is as follows:

I was out in town some weeks ago and I saw a shop in Singapore selling this "Gramophone for iPhone and iPad" which really caught my eye because I am such a sucker for vintage audio stuff as this blog can attest for. I thought it was a wired dock which you can plug your iPhone into and it'll play it through the speaker but it is solely an acoustic amplifier with no electronics or active speakers whatsoever.. kind of steep considering it was selling for $400sgd++ (!!!) if I saw the pricetag correctly.. it looks beautiful though as a decoration piece but I feel it isn't exactly a 'functional' speaker. Also it isn't exactly 'real' vintage unless the horn was taken from an actual antique speaker but I couldn't verify if that was the case.

Image from Restoration Hardware and for your reference only, click to go to their website

I also saw this in another shop for a whopping $700sgd++ (!!!!!??) by enandis (en & is), which is also a really nice decor piece but also has no electronics and depends solely on the iPhone's built in speaker for sound before being amplified by the ceramic horn. Another nice curio for your home if you can afford it..

Image from enandis and for your reference only, click to go to their website

Then finally there's this brilliantly designed project on Kickstarter: the Gramovox, which uses an active speaker to play sounds through the functional horn and even has bluetooth capability to stream music. It costs slightly more than $400sgd++ with shipping included (pricey but at least it has some functionality over the other two) which means taxes are applicable if I do purchase it and that would send the cost even higher.. so no snazzy retro horn speaker for me..

Image from Gramovox and for your reference only, click to go to their website

At least until I found this gem on eBay and won the bid a few days before Christmas for $68USD! It isn't exactly 'cheap' as well but compared to the examples above it is very affordable.. and I would believe it is increasingly rare as well which justifies a little more cost. It is ideal for a modification project because it has a good sized box below the horn where the driver (speaker) sits and I would be able to replace it with whatever I wanted to. As mentioned earlier, it also comes with a volume knob on the front that I should be able to link to a volume potentiometer as well.

The horn is fixed to the back of the box by two easily removable thumbscrews

Once the thumbscrews are removed, the horn slides right off the two screws and will be freed.

It is a good sized horn, no?

The bottom of the box can be removed as well and is held together by two fastening screws on either sides of the box shown here.

Once the screws are removed then the bottom cover comes right off as well.

The bottom of the box carries the now faded and torn instructions on how to use the speaker. There are readable examples available online but the instructions contain nothing useful in terms of modern day technology.

It says: "Best results will probably be obtained by using about 67.5 volts (!!!!!!) of "B" battery on the amplification unit

The antique speaker driver has an impedance of over 1kOhm which compared to modern speakers which are anywhere from 4-16 ohms is a great deal more and would not be compatible with modern day amplifiers because the sound would probably be too soft to be heard, assuming the driver works at all after 90 years! You could use a impedance matching transformer to hook up your modern day amplifier to this speaker but I believe the sound would come out very distorted.

The gears you see connected from the volume knob to the speaker actually adjusts the distance of the speaker diaphragm to the horn entrance. When the volume is turned lower, the gear turns the mechanism inside the speaker that adjusts the diaphragm further away from the horn entrance at the back and it does the opposite when the volume is turned up. I do not have a powerful enough amplifier to hook this horn speaker up as it is and decided right from the beginning that it is time to remove this speaker driver and let modern electronics take over.

The volume knob is held by a retaining pin that can be simply pulled out and the whole knob can be taken out of the box. The speaker driver can then be removed by lightly (or violently, depending on how warped the wood box is after 90 years) tapping on the two screws at the back.

It is time for you to retire!

The back of the speaker driver holds the two (irremovable) screws that can still be used because they are needed to hold the horn in place to the box. The screws have been rusted shut, but a little machine oil left to seep in for 5 minutes helped make the task a lot easier. 

So that is a complete teardown of the speaker. I intend to make this into a self-powered speaker with a rechargeable battery similar to the Gramovox above, but without the fancy bluetooth feature (perhaps in the future). I did my research and found many possible components I can fit inside from sites such as Adafruit where they have a Class D amplifier breakout board together with a USB/DC battery charger that I can hook up together.

Image from Adafruit and for your reference only, click to go to their website

Image from Adafruit and for your reference only, click to go to their website

But then I realized, there is only 1 horn, thus 2 channels for stereo is overkill.. and I couldn't find an acceptable mono amplifier. The other big problem was sourcing for a good speaker: it had to be small, but able to play audio at a good volume with no distortion. The small speakers available for DIY projects (also available on Adafruit) are the common ones with paper cones and are designed for simple tones and buzzes and not built to handle music playback.

Image from Adafruit and for your reference only, click to go to their website

So what then? Well, thankfully, the best small speakers (according to several reviews on the internet) is made right here in Singapore and it is the X-Mini Capsule speaker and it is readily available in all the shops here.

Okay.. readily available except in the black color that I wanted it but heck.. 

The X-Mini is a very common portable speaker that has been around for quite some time now. It has an expandable accordion baffle in the middle that gives the speaker a lot more air volume to work with so the relatively small 40mm driver sound a lot better and louder than it should and so I felt it was very ideal for this current project. The best part is that it has a complete circuit built in, so there's no need for me to design a battery charging circuit with an amplifier with a speaker.. this single device combines everything I intended to build into one small capsule that would (most probably) outperform any speaker I source to use in this project.

The speaker is pretty easy to take apart as well. Remove the four screws on the bottom part of the accordion and the base will drop out, revealing the PCB.

Remove the one screw on the PCB and everything will be exposed. I had no need to modify the upper half of the speaker where the driver is so I left that on its own. I planned to remove the switch, potentiometer and 3.5mm plug and extend it out of the box so I would be able to power on and off the speaker, adjust the volume, and plug in whatever music player I want to without opening the box to do so.

I set about desoldering the components from the board, but I found it extremely difficult to do so because the components were mostly soldered on both sides via through holes and they were a real pain to remove. I yanked out the potentiometer together with its traces and I had to improvise with thin strands of wire to rebuild the traces. It wasn't pretty but it works.. hopefully if your project requires you to repurpose the X-Mini like this then you would have a good desoldering tool to help you.

With the switch removed. The speaker uses a Double Pole Single Throw (DPST) switch but it only actually uses a single pole, thus a simple single pole switch would work.

The black tape hides my demolition job on the volume potentiometer traces. They also act as a strain relief so I don't accidentally rip out their tracks again by moving the potentiometer around.

I desoldered the male 3.5mm connector and soldered a female connector at the end of the longer wire. This female connector will be accessible together with the on/off switch on the outside of the box. I also extended the LED indicator so I would be able to see if the speaker is on or off. I did not touch the USB connector that is used for charging the device, but I ordered a microUSB extension (that has yet to arrive) that I will plug into the port on the speaker and fix the female end to the rear of the speaker box.

TLDR; I will eventually be able to access all the features of the X-Mini without needing to open the speaker box, making it a fully portable standalone speaker.

While the speaker has a 40mm driver, the entrance of the horn is a lot smaller at about 18mm. This means that simply placing the speaker at the horn's entrance would result in a lot of sound energy (volume) being wasted because the sound waves do not all enter into the hole.

I basically needed a small horn to guide the sound waves emitted from the X-Mini into the horn's entrance. I found these hard cardboard cones from the shop "Spotlight" where they sell all sorts of handicraft materials and cut it down to size:

I put everything together as shown below before closing it all up to give it a try, and it doesn't sound half bad! But I would prefer a metal cone rather than a cardboard one so this would only be a temporary fix just to get a feel of how it would fit and sound like. I will be taking a good look around to explore other options over the next few days/weeks and see what I can find.

I made a simple recording of the capability of this project with my phone's camera, and I will make a higher quality video when I am finally done with this project.

(Link to part 2/2)

Project "Technics SL-Q3 Direct Drive Automatic Turntable"

I have been using this turntable for about 2 years now and it has been chugging along steadily. It belonged to my father who said he bought it about 30+ years ago and the fact that it still turns at all is a miracle in this generation of gadgets that never seem to last longer than a couple of years before giving up the ghost. It originally comes with a thick rubber platter mat which I have since replaced with a thinner cork one. It spoils the look of it somewhat but it isn't going to win any design awards even with the black rubber mat anyway.

It is a quartz locked direct drive turntable, meaning no spinning motors or turntable belts, and if working well it would be spinning 99.9% (or so) at the correct speed all the time at either 33 or 45rpm. The tonearm moves automatically to the first track of a record when the start button is pressed, and returns automatically to rest when the end of the record is reached...simple and convenient. It does what it was designed to do with minimum fuss and performs well to my ears.

This turntable was built to last, but everything has its limits and recently I noticed it has been struggling to keep a constant speed. I can hear it every time I play a song with a sustained note and you can hear the pitch go up and down when it is supposed to be a steady pitch. A quick check with a stroboscope confirmed this and I set about dismantling the turntable to see what was up with it.

To take it apart, remove the platter mat and you will see two holes in the platter. Put a finger into each hole and GENTLY lift the platter up. Do your best to try and lift it straight up without knocking the against the center spindle as the direct drive motor magnets are there and might be damaged with rough treatment.

You can see the direct drive magnets in the picture below. The black cover has 3 screws securing it to the turntable body. Remove these screws and the cover lifts right off.

The cover has an indicator showing the front orientation so you can't put it back wrongly.

Lifting off the cover reveals...electrolytic capacitors!!! The number one most replaced component on this blog so far! They have been in service for 30+ years and it was time for them to be replaced...

The bottom plate has to be removed in order to access the bottom of the PCB. The four spring feet were in terrible condition and the rubber dampers we disintegrating as I handled them. They came apart as I unscrewed the four screws holding the bottom plate to the turntable body. I would obviously have to replace the feet as well.

What would you expect to find in a 30+ year old turntable? 30+ years worth to dust perhaps? Yep...it was so dusty that I took the entire bottom plate and ran it under a tap to wash away all the muck. I realize now that in my haste to assemble the turntable back later I forgot to take a picture of the clean bottom plate but trust me when I say I cleaned it up real good.

With everything stripped away I now have access to the top and bottom of the PCB. You can see the intricate system of gears and pulleys that control the auto start and return system. No electronic servos or other high tech stuff here! Besides the quartz locked motor speed control which is electronically controlled, everything else is nearly mechanical which is very interesting to look at...

Replacing the electrolytic capacitors was as simple as noting down the value and voltage rating and getting new replacements.

As always, modern equivalent capacitors are usually smaller than what they were 30+ years ago..

I found a few capacitors that were leaking as I desoldered them one by one. None of the other capacitors other than electrolytic generally require replacement after 10 years or so and they are usually the first components to fail, so do keep that in mind every time an old piece of equipment fails suddenly. You could bring it back to life by simply replacing the electrolytic capacitors as I have done many times on this blog with the other projects.

There...good as new for the next 10-30 years!

While I was at it, I decided to replace the corroded RCA plugs as well. These plugs connect to my pre-amplifier and have always needed an occasional twisting in their sockets to get a good connection and I was sick of it so it was time for them to go!

I ordered a good solid pair of Amphenol plugs and I couldn't ask for any better quality in a RCA plug (none of those 100% solid-gold-blessed-with-holy-water kind of plugs please...) Here's a short guide on how to replace RCA plugs on your player:

Strip the wire carefully to expose the shielding and the inner insulated core.

Twist the shielding to form a 'wire' on its own. This shielding is to be soldered on to the flat horizontal prong you see in the picture below.

Strip the inner wire ever so slightly and solder that to the center hole of the RCA plug. Solder the shielding as mentioned before and that settles this plug!

Rinse and repeat for the other plug and voila, new corrosion free plugs!

The old spring/rubber feet could no longer serve their purpose of absorbing the vibrations from the surface which the turntable is coupled to, so I bought these solid metal cone feet to replace them. They act as mechanical diodes, allowing vibrations to transfer from the turntable down to the surface which it is sitting on, and not the other way around.

I stuck cork pads on the corners of the base plate to give a buffer zone between the supports and the turntable for added dampening. This is beneficial especially if your speakers are near to your player and the vibrations induced by your speakers will result in audible feedback which is when the energy of the sound waves from your speaker causes your needle to vibrate, which in turn creates sound in your speakers, which in turn causes your needle to vibrate, which in turn...well...you get the picture...

Lastly, I also decided to give the dust cover a good cleaning and polishing as well. 30+ years of wear and tear has made it opaque. I used fine grade sandpaper for the more obvious scratches, followed by Novus plastic polisher no.1 and 2 which I last used with great results on the Westclox clock lens.

It seems to be dusty but it is actually covered in many fine scratches from the years of daily wear and tear.

Apply a good amount and buff with a soft cloth:

It's not perfectly clear, but it is much better than before. You probably won't get it glass clear without using a electric buffer but this was good enough for me.

I put everything back together and now the turntable works perfectly again. 

-The capacitor replacement cured the inconsistent motor speed.

-The new RCA plugs stopped the intermittent connection between the turntable and the pre-amplifier.

-The new cone feet reduced the vibrations absorbed by the turntable body, resulting in lesser mechanical feedback.

-The polished dust cover made the turntable slightly nicer to look at.

All in all a great success!