Beogram 8000 (5613): Installation of Redesigned Internal Beolover RIAA Pre-Amplifier

I recently redesigned my internal RIAA pre-amplifier for the Beogram 8000 and 8002 to feature a set of dip switches that allow choosing between amplified and non-amplified signal routing. That makes it possible to switch the pre-amp off if an equipped Beogram is moved from an amplifier without RIAA to an amplifier with a phono input. 

My previous design required removing the pre-amp board to accomplish this, and I thought this needed to change. All my other RIAA designs have this capability. The RIAA circuit is unchanged in this latest iteration, i.e. my previous in-situ measurements apply. Read here about my distortion and frequency response measurements on this design.

This shows the new board:

The main change from previous versions is the addition of a 6-position dip switch:

The above picture shows the switches set to 'RIAA'. Flipping all six returns the Beogram to its non-amplified configuration, and it could be plugged into any standard phono input.

In the following, I will discuss how to install the board. It connects directly to the solder points at the end of the ribbon cable that connects to the carriage. I usually mark the right channel with a black marker so I don't get confused when it is time to solder the wires to the RIAA board outputs:

For clarity, here is a snippet from the service manual showing the terminals of the ribbon cable:

The terminals at the bottom are the left and right outputs.

The first step was unsoldering the right and left output wiring and cleaning the solder pads with a desolder gun:

After removal of the mounting screw at the end of the ribbon cable assembly, I bolted the RIAA board in using the same screw and positioned it to overlap with the four solder pads of the output cables. Then I put a small amount of solder into each of the 'connection vias' of the board to make the connections between the RIAA inputs and the ribbon cable terminals:

The next step was to connect the L and R wires to the respective output terminals of the RIAA board:

I replaced the original woven insulation of the shield braids with modern shrink tubing (black) for a cleaner look.

The final part of the installation was connecting the RIAA board to its power supply.

Unfortunately, there is no power connected at the end of the ribbon cable, i.e. a separate wire needs to be installed to the 15V regulator. I connected a wire to the "15V" solder pad of the RIAA:

Note that the 15V label corresponds to the minimum voltage the RIAA needs for proper functioning. The maximum voltage allowed is 36V for this design. The next step is routing the wire to the voltage regulator PCB next to the front rod of the carriage. I recommend routing the wire along with the other wires beneath the subplatter. The critical routing points are labeled yellow in the photo below:

By feeding the wire under the plastic clips that hold the other wiring in place, it reliably avoids chafing with the sub platter. This shows the first of the clips (counted from the RIAA board):

And this the second when the wire emerges from underneath the subplatter:

This is how these two spots look with the subplatter installed:

The wire terminates at the input terminal of the TIP32 (0TR1) voltage regulator of the 15V rail. This terminal connects directly to the rectifier and main capacitor of the 15V rail and usually carries about 23V. I soldered the wire to the terminal, and this concluded the installation of the RIAA board!:

And then it was time to enjoy this redesigned RIAA pre-amp! I plugged the Beogram into the tape input of my amplifier and put on one of my favorite records, "Very Tall" by the Oscar Peterson Trio with Milt Jackson. This record was released in 1962 on Verve Records. I appear to have a re-issue from 1982 (UMV 2026).

Beolovely! This Beogram is now ready to be used with pretty much any modern amplifier or 'device' that still has a wired line-in!

New Beolover Commander Remote Control System for Beogram 8000 and 8002

I recently completed my work on the Beolover Commander Remote Control for Beogram 8000 and 8002. A few customer requests motivated me to port my Beogram 4002/4004 Commander System to the later 800x models. It seems more and more people aim to integrate these classic Beogram models with their modern B&O setups and remote control is part of the equation.

This is the reason that this time I designed a board that can be switched between using a standard classic Apple remote and Beo4 remotes. But it still needs a different IR receiver to match the 455 kHz modulated B&O remote control signals if a Beo4 is to be used.

Both versions are now available at the Beolover store.

I made a video that demonstrates the new 800x Commander system for both Apple and Beo4 remotes. The video also discusses the installation of the board on the Beogram keypad PCB. Enjoy:

New Internal RIAA Pre-Amplifier for Beogram 8000/8002 - Installation and Characterization

I was recently offered a nice looking Beogram 8002 from a gentleman in Oregon. After I received the unit I decided to restore it and while I had it opened up on the bench, I thought it would be a good moment for adapting the Beolover RIAA pre-amplifier design for this type Beogram. The 8000 series is popular among B&O collectors due to its unique linear induction platter motor, which drives the platter directly without any mechanical contact.

This shows the new Beolover RIAA pre-amplifier design:

I had to dramatically reduce the circuit dimensions due to the much less open interior space of the Beogram 8000 series. The design uses the exact same amplifier circuit I designed for my initial 400x pre-amplifiers, but the power supply is adapted to work with the 15V system of the Beogram 8000 series.

Implementation of this board requires opening up the Beogram. It is best to put it into 'service position', i.e. remove all significant components from the enclosure and set everything up on the bench:

This enables easy access to the ribbon cable that connects the output wiring to carriage and tonearm. This shows the end of the ribbon cable in its original state. The two left and right output cables are soldered to terminals on the ribbon end:

After removal of the wiring, a pattern of 4 circular solder pads is revealed:

The Beolover 800x RIAA pre-amplifier is soldered directly to these pads. It also bolts in mechanically using the bolt that connects the Beogram wiring to chassis:

The power connection to the board unfortunately requires routing a wire from 0TR1 that makes the stabilized +15V supply. This shows 0TR1 next to one of the carriage rods

The orange wire that connects to the emitter of this pnp TIP32 transistor carries about 21.3V from the rectifier. This voltage is used to power the RIAA board. The thicker red wire that is soldered to the solder terminal of the orange wire in the picture above is routed to the RIAA board and soldered to its 15V (min) terminal (see picture above).

After this fairly straight-forward installation, I characterized the circuit. Since the amplifier section of the board is identical to the version for the Beogram 4002 and 4004 series, I will only discuss the noise characterization here, which is specific to the Beogram 8000 series. The amplification and RIAA de-emphasis data is identical to what I discussed earlier in the post about the original 400x design.

When considering internal RIAA pre-amplifier designs the amount of electromagnetic interference (EMI) and back EMF from the platter motor leaking into the amplified signal is the most important quality factor after the performance of the pre-amplifier itself.

Since motors are notorious for feeding back voltage ripple into the power rails of their supply, it is necessary to take special precautions when designing an internal pre-amplifier that shares its power supply with a motor. RIAA preamps have their maximum gain of around 60dB in the lower frequency range due to the fact that lower frequencies are encoded at smaller amplitudes in the record grooves.

60dB corresponds to a 1000x voltage amplification. Unfortunately, platter motors usually generate voltage variations in exactly this low frequency range, i.e. even the smallest motor related voltage ripple can become very audible in the audio output signal if the amplifier supply is not carefully separated from the main supply of the turntable. As an example, a small 1mV motor ripple in the amplifier supply voltage could result in a 1V output ripple at 60dB amplification! This would be about the same volume level like that produced by a loud section on a vinyl record.

Characterization of the noise performance of the Beolover internal RIAA pre-amplifier for Beogram 8000 and 8002:

I used a QuantAsylum QA400 audio analyzer for these measurements. The QA400 is a predecessor of the currently sold QA403. The QA400 is essentially a very sensitive analog to digital converter (ADC) that is matched with software that can show a Fast Fourier Transform (FFT) of the audio signal. The resulting 'FFT spectra' essentially show the amplitude of individual frequency components of an audio signal plotted on the frequency axis. A simple example would be the FFT of a perfect undistorted 1 kHz tone. The FFT spectrum of this signal would be a single peak at the 1kHz frequency.

When measuring noise spectra with such a device, one gets spectra that show all the different frequency components of the noise. Ideal 'white noise' would yield a spectrum that has the same amplitudes for all frequencies, i.e. one would get a horizontal line above the frequency axis.

Real life situations are usually more complex and this brings us to the graph below:

This graph contains FFT spectra measured at the output of the Beogram 8002 deck before and after installation of the RIAA pre-amp board.

All five spectra were measured with the arm down and the platter running. In other words in the situation one encounters when playing a record.

The green spectrum at the bottom was measured before installing the RIAA pre-amp, i.e. represents the situation found in an Beogram 8002 in its original factory condition. The signal from the cartridge goes directly into the DIN7 output plug without any electronic circuitry in-between. Therefore the noise seen in this spectrum is purely related to the Johnson noise coming from the cartridge coils and the wiring hooked up between the cartridge and the QA400 audio analyzer, plus any EMI from external sources. The peak at 60 Hz is related to the EMI coming from the power system around the house where I did these measurements. It is very difficult to get rid of this peak in practical terms since this type of EMI is omnipresent in the environment and so would require complete Faraday shielding of the measurement setup. Luckily in FFT spectra one can easily identify it and then ignore it as a measurement artifact.

It is more interesting to look at the other end of this spectrum, where we see a number of small peaks. These peaks seem unique to the Beogram 8000 series since I did not see them in the corresponding spectrum measured when I characterized the original Beogram 4002/4004 version of this amplifier design.

While it is difficult to determine the origin of this noise signal with 100% certainty, my hypothesis is that it is interference from the linear platter motor. This motor is much more exposed than the fully shielded DC platter motors of the earlier Beogram 400x series and so it seems likely that these peaks are caused by EMI from the drive system.

This EMI seems to couple into the output signal via the traces on the ribbon cable that connects the tonearm wiring to the terminals where the output wires are connected. This ribbon cable is a mechanically elegant solution enabling carriage motion while maintaining wire connections, but is not shielded at all. In comparison the preceding 400x series Beograms bring shielded wiring right up to the base of the tone arm before it becomes exposed. This may explain the more quiet spectrum I measured for the 400x.

This hypothesis is supported by the measurement results on the RIAA pre-amp shown above the green spectrum. The first spectrum I measured (brown) was measured with the RIAA board soldered in, but the inputs connected directly to GND with small wire bridges. This is shown here:

This measurement allowed characterizing the noise that is contributed by the amplifier itself, since the signal at the inputs is 0V (GND). This is a common approach for testing the noise background of amplifiers.

Let's have a look at the spectrum. It basically replicates the low frequency peaks already seen in the green spectrum, which are measurement artifacts, but it does not show any of the high-frequency peaks seen in the green spectrum. This means that these spectral components in the green spectrum really come from 'before' the RIAA amplifier, i.e. from the wiring between cartridge and amplifier input.

This is clearly supported by the next spectrum (red) that was measured after removing the GND jumpers. In this case the signal from the cartridge was directly fed into the amplifier, and the amplifier duly amplified the noise.

In fact, when connecting the Beogram output to my amplifier, I was able to hear a weak noise signal from the speakers when turning up the volume to maximum. Music at this level would certainly have alerted our neighbors...;-). I.e. for all practical purposes this is a very weak noise signal that needs a lot of amplification to be audible. But the FFT spectrum mercilessly shows it in a fairly dramatic way!

To further characterize the significance of this EMI noise I did two more measurements, this time using  'Ultimate Analogue Test LP' from Analogue Productions. This test LP allows doing FFT measurements under actual vinyl record playback conditions. The blue spectrum in the graph was measured while playing Track 6 on Side 2 of this record ("Silent groove for bearing rumble and table isolation"). This track is a simple smooth V-groove without any encoded audio signal, i.e. it mainly produces vinyl groove surface noise (and of course a few klicks and pops). This essentially gives us the noise floor of a well-manufactured record. We see here that the blue spectrum has a considerably higher noise level than the red spectrum. The EMI noise only very weakly peaks through in this spectrum, i.e. it basically blends into the vinyl surface noise. I was not able to discern it anymore from the vinyl noise when listening to the track via my amplifier, even at very high volumes.

The final (black) spectrum in the graph was measured on Track 1 on Side 1 of the record, the "1kHz reference tone", which basically simulates actual listening conditions. This spectrum is dominated by a singular peak at 1 kHz, accompanied by its harmonics towards higher frequencies. These harmonics are mainly caused by distortions in the cartridge, which are typically around 1% (the amplifier itself has only about 0.012% harmonic distortions).

More interesting for this discussion is that the surrounding noise spectrum is even higher than the pure vinyl surface noise and in this spectrum the EMI noise is completely drowned out by noise coming from the 1 kHz track.

After this analysis it was time to enjoy this restored Beogram 8002 and just listen to some nice music. I selected one of my favorite records, "House Boat" by Volker Kriegel, which he recorded for the MPS (Music Produziert im Schwarzwald) label in 1978 (MPS 15.535). In my opinion one for the best Kraut Jazz records of all times. Maybe one of the best jazz records overall (I know...beauty is in the eye of the beholder...;-).

Anyway, a perfect record for a Beogram that originated from the early 1980s! Of course this record was cleaned ultrasonically before play with a CleanerVinyl ProXL setup to bring out its full analog vintage glory!

Here is an impression of the setup!...I always like playing the 800x turntables in their service position. Almost looks like one of those Very Expensive Modern Designs!...;-)

This sounded all very well! A pretty happy result. This Beogram can now smoothly be integrated with more modern B&O systems that do not have a phono input anymore.

This Beogram will need to remain in service position a little longer. I am working on one more upgrade, which I am hoping to feature soon in another post.

Beogram 8002: Transplantation of Output PCB

Finally I had some time again to work on the Beogram 8002 that I recently started to restore. The last two weeks were an 'interesting experience' after Michael Fremer's video appeared on analogplanet.com featuring my CleanerVinyl ultrasonic vinyl cleaning equipment. 

The next step in this project was to transplant the DIN7 output assembly from a parts-Beogram 8002 that I acquired from a crooked audio repair shop in Chicago. This unit is now coming in handy here since the 8002 was missing its DIN7 output cluster:

I always wonder what drives people to do such things, but here we are on our interesting little self-absorbed planet...;-).

I extracted the assembly from the parts 8002:

I decided to update the relay with a modern encapsulated unit while I had everything on the bench. The original Omron G2V-2 relay can easily be replaced with its modern G5V-2 cousin, which has the same footprint:

And here is a photo of the installed new relay:

and with its shield clamped on:

This shows the restored wiring:

After verifying that the relay worked properly I installed a grounding switch that allows to connect signal and system grounds if there is a hum problem:

On to the two other issues that I was able to identify: The deck does not detect the absence of records and happily lowers the arm onto the platter. It also has a missing digit in the RPM display. One step at a time.

Beogram 4000: Keyboard Keys - Video About Removal and Installation

A Beogram 4000 that I recently sent out after restoration arrived with two keys detached from the keypad. I had taped them down and put a foam pad on top so that the hood would press them down, but two still came loose.

This is a little bit a design flaw of the 4000, since its beautifully large (and therefore heavy) keypad keys are only attached by leaf springs. This is great as long as the unit sits on your sideboard, but the rigors of shipping can be too much for this mechanism. I wanted to avoid another round trip of this beauty, and so I decided to design special installation tools for my customer, and I made a video how to use them. The video shows how to remove the keys, and how to get them back in. Like all my part designs, the tools are available to other B&O enthusiasts. They are plastic, i.e. there is little risk to damage the precious brushed aluminum surfaces. The tools also work much better than the usually employed flat head screwdrivers. Check out the video:

Beolink 5000: Glueing the LCD Screen Back In

The Beomaster 4000 that I recently outfitted with a toroid transformer came with another Beolove challenge piggybacked into the box: A broken Beolink 5000 remote control, which had a detached LCD screen. Unfortunately this Beolink 5000 was beyond repair since the LCD screen had mechanical damage at the contacts end, probably due to a fall of the display on a hard floor or similar. 

We decided to not give up but rather try to procure a potentially fixable unit from ebay. Luckily, a few weeks ago a 'lot' of three Beolinks became available with the promise that one of them was actually still in fully working condition. My customer won the auction and had the units shipped directly to my bench. Unfortunately, it turned out that the LCD screen of the working unit also was already loose,

but it had not detached yet from its ribbon cable. Luckily, the seller had the presence to tightly wrap this unit so the screen stayed where it was during shipping and it did come alive when I put batteries into the unit:

I decided to develop a fix for glueing the display back into the remote body without breaking the very flimsy plastic foil ribbon connector that connects the LCD display to the circuit board. In fact this particular design feature seems to do in 99% of the Beolinks since it simply rips off when the screen detaches and falls out due to ageing glue. The glue seems to be the same foamy stuff they used for attaching the aluminum cover to the Beogram 8000/8002 turntables, i.e. it is no surprise that the LCD screens also pop out at this point in time.

Anyway, the task was to not kill the ribbon connector, while handling everything and cleaning the old glue out etc...It was beneficial that I had the two other units with completely detached screens to practice on. I used them to develop a 'tool set' that would allow me to do the repair with minimal mechanical stress on the ribbon connector. 

Here we go:

I opened the unit up:

Then I carefully pressed the LCD screen out of its frame and moved the PCB and screen a bit to the left to release the board from its tabs on the right. Once the two parts were liberated I supported them with a custom designed 'brace' that would stabilize them in their relative alignment:

I applied the matching top part:

And flipped the entire 'assembly' over to the right:

Now I removed the board-to-board ribbon cable from the display control board:

The two tabs left and right of the ribbon can be pulled out and then the cable comes out:

This liberated the display part allowing me to go to work on removing the glue from the display frame:

The next step was to remove the glue from the LCD. The orange part of the brace now served as support during this procedure. I had designed a screw hole into left side of the orange part that allowed me to bolt down the circuit board to make sure there was no movement between LCD and PCB to protect the ribbon:

After cleaning off the glue it was time to install some industrial strength double sided tape in the frame. I had developed two more 3D printed parts that would allow me to apply the tape and then cut it to size with precision to not impair the translucency of the screen:

and with tape applied:

Then I cut the 'window' out of the tape layers using a razor blade and a matching 3D printed part that fit exactly into the display bay from the top:

This was the end result:

after removing the tape backing

Then I reconnected the display board and flipped it over with the braces in place:

After carefully pulling out the red brace part, I pressed the display into its bay, making sure that it was aligned properly:

And then came the moment of truth! Did the ribbon cable survive this stressful operation? After putting the keypad back on and inserting the three batteries it turned out that the operation was successful. The unit came alive again!

The next step is to figure out how to repair completely detached screens...another day, more Beolove!