Beomaster 4400 - Australia Project - Wrapping Things Up

This Beomaster 4400 from Australia passed its final bench testing today.

I can also report that musically the Beomaster 4400 sounds great.

Here are a couple of pictures of my first listening tests on the bench.

I will install the Beogram 4400 cabinet cover next.  Then move the receiver to a listening room where I can spend more time checking out all of its features.


Prior to this listening test, I ran my usual harmonic distortion and frequency response tests on the Beomaster 4400.
I use a dummy speaker load of 8 ohms and use a 1 KHz, 0.316 VRMS test input sine wave into the Tape 1 inputs (L & R).

I run the harmonic distortion (THD) and frequency response tests with the Beomaster 4400 at its maximum rated output.  For an 8 ohm speaker that is 50 Watts.  I actually tested it at 55 Watts in this case.

Here are the measurement results.

The signal drop off above 22 KHz on the frequency response measurement is due to the measurement device (QuantAsylum QA401 Audio Analyzer) ending its test run.

The THD measurements at 55 Watts are nicely below the Beomaster 4400 rated value of 0.1%.

Those measurement results are what I have been getting from my Beomaster 4400 restorations so they are good measurements to make and compare to.

To get to this final bit of the Beomaster 4400 restoration testing I spent some extra time installing some power protection features to the receiver.

On all of my Beomaster 4400 restorations I have been installing an arc suppression device to protect the Beomaster 4400 power switch.  The Beomaster 4400 On/Off switch switches full power across its contacts and I have seen one Beomaster 4400 where those contacts were pitted so bad the switch had to be replaced.

My previous Beomaster 4400 restorations were all Type 2419 versions though.  They only required a single arc suppression device.  The following schematic shows the Type 2417 and 2419 power switch differences.

The On/Off switch of the Type 2417 routes both the hot and neutral AC wires to the Beomaster 4400 transformer while on the Type 2419, only one of the AC wires runs through the switch.

On the Type 2419 version I only have to put one arc suppression device across the switch contacts because the two sets of contacts are connected together for the one AC wire they handle.

The Type 2417 uses a set of contacts for both AC wires (hot and neutral) so I added arc suppression on each contact.

Here is my installation of the arc suppression for the Type 2417.  I had to build a 3D printed support to mount them inside the Beomaster 4400 cabinet.  The black mounting screws for the assembly are plastic.

Another power protection install I did was to install a bleeder resistor on each of the two ±35 V rail reservoir capacitors.  The bleeder resistors insure that both 10,000uF capacitors discharge together and relatively evenly when power is turned off.  This also provides a bit of safety when the Beomaster 4400 is opened up for service.  The two 10,000uF capacitors will be at zero volts in that case.

For the bleeder resistors across 10,000uF capacitors 0C8 and 0C9 I chose 5100Ω.

The final power protection installation I did was to build and install a soft start circuit for the ±35 VDC rails.  A lot of amplifiers do this as the soft start circuit slows down the in-rush of current to the reservoir capacitors when power is turned on.  Limiting the in-rush current will put less stress on the transformer, fuses, diode bridge and reservoir capacitors.

The way it works is when the Beomaster 4400 power switch engages, the ±35 V rail voltages go through a pair of 22Ω resistors instead of directly to the 10,000uF capacitors.  That slows down the charging up of those two capacitors.  After about 1.7 seconds, a relay switches out the two 22Ω resistors so the remaining 5 to 10 VDC of rail voltage directly charges up the reservoir capacitors.

Here is a picture that shows the 10,000uF reservoir capacitors charging up with and without the soft start circuit.

A nice side effect of the soft start circuit is that it greatly reduces any "thump" sound through the speakers when the Beomaster 4400 turns on.  However, the reason I added the soft start circuit was for long term protection of the power components.

Here is the soft start circuit installation that I implemented.  I made a small 3D printed mount for the circuit board so I could easily attach it to the inside of the Beomaster 4400 cabinet.

The soft start circuit is powered by the Beomaster 4400 22V power supply.
The inputs to the soft start are the ±35 VDC from the Beomaster 4400 bridge rectifier.
The outputs from the soft start go to the the two 10,000uF capacitors (0C8 and 0C9).

Note: For a Type 2419 Beomaster 4400 I remove the two auxiliary AC plugs that the Type 2417 does not have.  Removing the two AC plugs provides room for the soft start circuit and I created a 3D printed plate to cover the rectangular cabinet cutouts for those plugs.

Now for some more listening to this Beomaster 4400 before packing it for shipment back to Australia.

Beogram 4002 (Type 5513): Full Upgrade with SyncDrive Platter Motor, Commander Remote Control and Internal RIAA Pre-Amplifier

My customer from Kentucky decided to give his Beogram 4002 the 'full treatment' and asked me to install all three Beolover upgrades that are currently available for the DC platter motor Beogram types:

1. SyncDrive synchronous platter motor: The SyncDrive improves RPM stability and consistency and levels DC motor Beograms up to AC motor performance.
2. Commander remote control system: The Commander is the perfect addition to 4002 and 4004 Beograms for protecting their fragile keypad coatings. It uses an Apple remote for controlling all functions of the Beogram. In addition the Commander adds auto-repeat functionality and an improved << >> scanning function.
3. Internal RIAA pre-amplifier: The Beolover RIAA replaces the original output board and allows directly connecting the Beogram to any high-level input of modern amplifiers, like CD, DVD or AUX.

All three upgrades are plug and play, i.e. there is no soldering required for their installation. I started with the SyncDrive. This shows the original DC platter motor still installed:

The SyncDrive bolts to the same mounting posts and it only needs one cable connection to the main PCB:

Then I removed the keypad to get to the output board. This shows the original board still in place:

The Beolover RIAA pre-amplifier has the same form factor like the original board. Simply plug the wire harnesses into matching board headers on the RIAA board. At the same time I also plugged the Commander remote control board into the keypad header on the main board:

The final step was putting the keypad back in, plugging its connector into the Commander board and bolting the auto-repeat indicator in with the keypad screw:

And then it was time to play this lovely updated Beogram 4002 a bit more. I selected another great Milt Jackson vinyl, "Olinga", which was recorded in 1974 on the CTI label (CTI 6046). Before play, this record was ultrasonically refreshed using a CleanerVinyl ProXL setup reducing clicks and pops to a minimum. 

Beolovely!

I will now play this deck for another week or so and then it should be time for sending this upgraded Beogram 4002 back to its owner in Kentucky!

Update of MMC Cartridge Box for MMC 1-5 Cartridges

A while ago I designed a storage and shipping container for MMC cartridges. Initially this container was only outfitted with an insert for the old style MMC20 cartridges.

I just designed a new insert specially designed to hold and protect the newer MMC1-5 cartridges:

It opens like a book. Just stick the cartridge in the specially molded holder:

The inserts are printed from flex filament, i.e. are a bit elastic for a gentle and safe fit of the cartridges.

That is how they look closed. A little window shows what is inside:

Beolovely! Like all our parts these boxes are available to other enthusiasts!

Beolover MMC Cartridge Storage Box: Yet Another Redesign

Sadly, I had to retire my last Beolover MMC storage box design due to inconsistencies in Shapeways' production output. The tolerances requirements for press-fits is fairly high, and Shapeways seems to have variances that are too large. Recent orders yielded parts that were a bit too tight and the cartridges would not fit smoothly anymore.

Triggered by the desire of a customer to acquire a few of the storage boxes I set out to come up with a more robust (in production terms) redesign that can be printed directly by the Beolover Printer Farm. This shows my new approach:

The white insert is printed from a special flexible filament, which gives it a rubbery texture that holds the cartridge securely in place. This insert slides into a hinged hard shell box that protects everything. The insert is held in place by a protrusion from the bottom of the box that clips into a matching opening in the insert.

This shows the box closed:

The 'window' informs about the content of the box. So if one has several cartridges for different listening situations, it is easy to find the right box. Beolovely!

MMC Cartridge Box: Now Available on Shapeways

What better way to celebrate my 400th beolover post with making the Beolover MMC Cartridge Box available on Shapeways?? It is time for adequate protection for our valuable cartridges!

It was a lengthy and difficult process to get this part designed and I had to go through many design iterations to get the 'feel' right. I desired to have a solid press-fit between the cartridge and the 'base' of the box to afford maximum protection to the cartridge in case someone accidentally drops the base after inserting a cartridge. The top on the other hand was supposed to fit with some, but not too much friction to enable easy access. Some manufacturing tolerances at Shapeways did not help this process either, and so it took me many design iterations and test prints to get to a point where the print outcomes between different print-runs were satisfactory.

So here we go: This shows the bases with cartridges inserted and the matching tops:

And with closed tops:

And why not get base and top in a duo-tone combination??:

There are 49 color combinations possible as they are available in seven colors...check out the parts at my Shapeways store!

Or use these direct links below for ordering. You can select the color during checkout. It usually takes about two weeks to get parts from Shapeways in most parts of the world.

MMC Cartridge Box: Another Iteration

This is a follow up to my recent post about the design of MMC20 and MMC4000/6000 cartridge storage boxes. I just received the next iteration from Shapeways. I changed the lettering on the covers and also designed a cover with a view port to directly see what type cartridge is inside. Here are a couple of impressions:

I also made the covers a tad thicker in the hope to get a tighter fit, but now they are a bit too tight for my taste. So, I guess the next iteration may be the final one...;-)

MMC Cartridge Box: A First Impression

I accumulated a few MMC20 and MMC4000/6000 cartridges over the years, and I only have a couple protective covers. I always wanted a better solution for keeping them safe. Protecting them definitely makes sense considering the prices they fetch these days in good condition. So I set out to design a 3D printable small box. First I took exact measurements of a MMC20 cartridge and built a model in Inventor. Then I created the lower part of a box moulded to the metal housing of the cartridge and a cover.

Yesterday I received the third version of the design from Shapeways, which finally seems to fit the cartridge perfectly, and also has enough friction between the cover to give a nice open-close feel. The issue with 3D printing really is that every technology and material behaves differently, while having specific tolerances and 'quirks'. So it takes a bit of trial and error to get a working product from a CAD design. Well, here are a few impressions:

This shows the empty container. The bottom part shows the characteristic slant of the bottom part of the cartridge. The front part is cut out deeply to make sure that the cantilever and tip never touch anything:

Pretty amazing the resolution that Shapeways can achieve. The slightly grainy surface is a result of their Selective Laser Sintering (SLS) process that blasts the plastic granules in the printing bed to fuse them into a solid body. 

And here with inserted MMC20CL cartridge. The cartridge body makes a nice smooth press-fit with the part to ensure protection even if turned upside down:

And closed. The cover shows the cartridge type on top:

I think I will redesign that a bit with bigger lettering. I will make a specific cover for each MMC20 and the MMC4000 and MMC6000 models that one can easily find the desired one. Shapeways also offers a bunch of nice colors, i.e. color coding will be possible, too.

Stay tuned for the final version...They will be offered at the Beolover Shapeway store.