ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Many Beoworlders spend a lot of hours and money refurbishing the classic B&O products.
The normal “test” of all the effort is a listening to the sound quality, which is really ok and always needed.
Have you ever considered being able to measure the specifications and compare the specifications with the original B&O spec.?
I have for many years been using a system based on
PC
External soundcard – E-MU 0204 USB
And a very necessary interface for the soundcard – impedance converter on both input and output of the soundcard.
Software
Very technical but what can it be used for?
With this system you can measure the following specifications:
· Frequency range
· Distortion
· Sensibility
· Signal / noise level
· Crosstalk
· Damping factor
· Output power
Why not use specific test equipments for these measurements?
Because the price of such equipment is very expensive – even if you find second hand equipment.
I have done the following:
· I have bought the PC (of course), the USB soundcard and the software
· I have designed, developed and build the interface / buffer test equipment.
The price level for the complete system is only a fraction of the price for dedicated test equipment.
The reason for explaining all this ……… perhaps someone would like to establish a very high performance test system for a relatively low cost?
If so – I would try to help.
I am not selling the equipment, but I would like to help by giving away the circuit diagrams, advises how to build a much more.
I can also supply the printed circuit boards and the alu front panel because I have already paid for the masks.
See some photo’s of my new 3.rd. generation of the soundcard interface / buffer.
Please contact me if you are interested in the project!.
/Frede
This is a top view of the test equipment.
This the PCB's and the Alu front panel for the equipment.
(You start from here )
To day I have finish building this 3.rd. gen. interface / buffer and I have been testing the result.
I am really very happy about what i have gained by this new updated build. All the specifications of the test equipment have been improved quit considerable and my test of the classic B&O products in the future will be even more precise
The photo is of the build in RIAA amplifier, which means I can easily test any Beogram and get e.g. a frequency characteristic of the cartridge, measure the distortion af the cartridge and more.
A very generous and helpful offer Frede.
This is very interestiing Frede and I for one would love to be able to measure equipment that I am working on without the worry of old equipment being out of spec :-) Tell us more please!BTW Have you considered software based wow & Flutter measurement? Would be superb as I am not sure my meter is up to scratch although the result I get suggest it is not at all far off!?
Olly
Step1: This is very interestiing Frede and I for one would love to be able to measure equipment that I am working on without the worry of old equipment being out of spec :-) Tell us more please!BTW Have you considered software based wow & Flutter measurement? Would be superb as I am not sure my meter is up to scratch although the result I get suggest it is not at all far off!?
It is allready implemented. I have used the MKII of the soundcardbuffer for some years allready to measure wow, flutter and rumble on turntables and taperecorders.
The software for this is found here: http://www.audiotester.de/
(I actually suggested to the sofware developper to expand his software to be able to measure these specifications some years ago and as you can see on his webpage - he did. I also supported him to compare with the results of traditional testequipment)
I must have done something stupid
But, respect for the amount of time it must have cost you to develope the circuitboards etc.
Very interessted in the diagrams etc.
Did you finalize the project? As the pictures above shows us an unused switch and din-connector?
Beobuddy: I must have done something stupid ???????????????? But, respect for the amount of time it must have cost you to develope the circuitboards etc. Very interessted in the diagrams etc. Did you finalize the project? As the pictures above shows us an unused switch and din-connector?
????????????????
Oh yes the procect is all finished by now.
What was missing on the photo's was the build RIAA preamp, it is in place and tested now.
If you are seriusly interested to build this project, please send me an email.
I am right now doing some work on the documentation.
I have been testing the design and I am very happy with the results.
The software for performing the test is: RightMark Audio Analyzer 6.2.3
The testsetup:
Test loop thrue: Soundcard output -> Testequipment output -> Testequipment input -> Soundcard input.
So the result you see is the full system result!
I have received a few questions regarding "what can be measured" with the soundcard and soundcard buffer ?
This is the parameters:
(I know because this is the parameters I am measuring on costumers products when I perform a full restoration)
FM receiver
Sensibility
Frequency range
Signal/Noise
Distortion
Chanel separation
Crosstalk
Pilot tone suppression
You also need: Signal generator - Radiometer re101 - Stereo coder Radiometer re SGH40 or similar
Software: TrueRTA - Audiotester
Amplifier (Power amplifier and preamplifier)
RIAA frequency response
Damping factor
You also need: Ground loop isolator (speaker output -> soundcard buffer)
You cannot measure:
Total output power (because the soundcard cannot handle voltages over 2v or less depending on the soundcard you choose)
This could be measured using: B&O Audio Monitor AM1
Loudspeaker
You also need: Microphone - microphone preamplifier
Record player
Wow
Flutter
Rumble
You also need: A vinyl test record - one for wow and flutter and one for rumble
Software: Audiotester
Cartridges - Pickup
Channel separation
Channel level difference
You also need: A vinyl test record for frequency range
Tape recorder - wheel to wheel or cassette
You also need: Test tape for frequency range and for wow, flutter - if your tape recorder have separate heads for recording and playback you don't need a test tape for frequency range.
Software:
I am using......
TrueRTA - http://www.trueaudio.com
Audiotester - http://www.audiotester.de/
Test records:
I am using.......
wow - flutter: B&O 3621016 - but you can use any test record with a constant tone of 3.16 kHz tesfrequency
rumble: DIN 45544 Rumpel-Mess-Schallplatte
Frequency range: Brüel & Kjær Stereophonic gliding frequency record 20-20000Hz
Test tape:
I have bought Revox test tape on the eBay
Test conditions:
I am using the DIN 45500.
Because this standard belongs to the classic products.
Checking that all components fit into the box.
//Bo.A long list...
Bos00:Checking that all components fit into the box.
You may have to squeeze it a little
Collecting Vintage B&O is not a hobby, its a lifestyle.
Almost done, but i missed a few thing when ordering so I'll have to wait for those.
Testing the power supply.
Here is my start of the Classic Audio Tester project. I will try to just post some information on the project that hasn't been posted yet. I have between 80 and 90 percent of the parts in but it will likely be late January before everything arrives. The PCB parts, transformer, front panel and case arrived though so I started some of the mechanical work. Even though the boards, front panel and case all go together, there is some minor fabrication needed to make everything fit. The front panel lines up perfectly with the mounting holes in case. However, the edges of the panel should be filed down (rounded) in order to fit properly in the case end cap. The main PCB also needs to be filed in four places so it will slide perfectly into the case. Some aluminum mounting brackets should be fashioned to secure the main PCB to the case. I used some angled aluminum stock to cut a couple of brackets.
My next step is to determine where holes need to be drilled in the case for my two mounting brackets.
Here is a before and after picture of fitting the main PCB in the case
Here are all the boards waiting for assembly.
Getting closer.
Bos00: Getting closer.
What did you do for your switches? Were you able to find SPDT switches that fit the holes in the front plate or did you have to drill the holes bigger? I haven't been able to find any switches with a mounting barrel diameter that small (4.7mm). The smallest I found are 6mm so I got some of those but I was wondering if you found some smaller switches.-sonavor
sonavor:What did you do for your switches? Were you able to find SPDT switches that fit the holes in the front plate or did you have to drill the holes bigger? I haven't been able to find any switches with a mounting barrel diameter that small (4.7mm). The smallest I found are 6mm so I got some of those but I was wondering if you found some smaller switches.
No, I had to drill the holes slightly, to 6mm.
Okay, thanks
-sonavor
A little progress. Power supply and all relays and switches connected and working. Reaming is signal wires and grounding
So finally.
Testing.
Result
Special thanks to Frede Kristensen for idea, design, instructions help & support.
It is time for me to get back on track with building Frede's audio tester. I got delayed when I thought I could do a Beogram 8002 repair while waiting for my audio tester parts. Anyway, I have all of the audio tester parts so I am starting to work on it this weekend. Mechanically I installed the two mounting brackets to the case for the main board. I cut and shaped some angled aluminum stock with a small hacksaw and a file. Next I drilled holes for the mounting points and tapped the holes in the aluminum with threads for the screws. I used aluminum screws to secure the brackets to the case.
I finished up most of the mechanical work this weekend. This picture is of the front and rear panels. I had to drill holes and cutout a section in the rear panel for the AC power recepticle. On the front panel, I had to redrill the holes for the switches to make them larger. I ended up increasing them to a quarter inch as that is the typical size for small toggle switches I can get. The switches shown in the picture are some I ordered (6mm mounting hole) earlier...but I'm not sure I will keep them. One of the seven switches broke so I ordered seven more (different brand - 1/4 inch mounting hole). All of the metal cutting tasks should be over now so I can get to work on soldering components to the boards.
It turns out I did have an extra toggle switch so I now have all of the components in place for the front and rear panels. Last night I started soldering the PCB connectors for the main board and the large relay board. The large relay board to main board connectors took me a while to decide on - reviewing all of the pictures of the two, fully assembled testers. I hink I have those ready to wire up (later). The next step is to get all of the PCB components soldered in place. Once that is done I will be able to do the wiring.
I managed to get some bench time this weekend and made a little progress. I have the Input Amplifier board done except for the grounding terminals. The two Output Buffers are started. I also have PCB edge connectors and component sockets installed. On the Output Buffer I found a discrepancy with the schematic and the PCB regarding R15 and R16. The PCB and build example correctly show R15 as 68 Ohms and R16 as 6.8K ohms. The schematic and parts list have them reversed (R15 as 6.8K an R16 as 68). I installed them per Frede's example build.
I have most of the board components installed now. I am short a couple of 2-pin board connectors (one for each RIAA PCB) and I don't have the jumper/test point PCB terminal posts installed yet.
I am finally ready for the board assembly and wiring everything up. Here is a picture of the boards with the terminal posts soldered in.
Test fitting the boards in the case
Another view of fitting the boards in the case. Here is looking more closely at the power supply and two output buffer boards. I will add the star grounding point next and start on the wiring.
I was able to put some bench time in this weekend and got the +-12 VDC power supply for the audio tester working. The picture here shows the +-12 VDC measurements of the supply by itself. In getting the power supply board wired up I discovered my installation of the main board didn't allow for enough adjustment. There was a problem fitting the power supply board and the rear test panel. The AC power plug terminals stuck out too far (even when I bent them at right angles). The fix for this wasn't too bad. I realized I needed slots in my main PCB mounts that attach the board to the bottom of the tester case. With the slotted holes I was able to adjust the position of the main board so everything would fit. After adjusting the position of the boards, I ran the AC power ground wire to the star grounding terminal tab (green wire). I ran one of the AC hot wires (red wire) to the front panel switch (through a connector). The other side of the switch routes the power signal to one of the transformer input pins (white wire). I connected the other AC hot wire (white wire) to the front of the tester and through a connector to the other transform input pin (white wire). I used a connector for the wires from back panel AC input plug so it would be easier to take the tester apart if I need to.
On my 12 VDC power test, the on board blue LED that is next to the voltage adjustment trimmer doesn't illuminate very bright. I used the same type of blue LED (in series with a 1K ohms resistor) for the front panel Power On indicator and it illuminates as bright as I expected.
Here is a better picture of the power signal wiring. The next step is to build the wiring runs from the front and rear panels to their respective PCB connectors. It is easier for me to solder all of those wires to the front panel locations without having the front panel mounted to the chassis.
Here is a picture that shows the underside connection of the AC active and neutral signals to the transformer inputs.
I started wiring the front and rear panel RCA jacks. I also added the shield wires on the jacks that where the shield wires go to the star grounding point. My wiring color scheme is red for right channel, black for left channel and green for shield wire that goes to the star grounding point. I will use a different wire color for the RCA shields that go to the PCB signal ground. I will also use some other wire color for the switches.
I found it a little difficult to determine the correct wiring for the Monitor & RIAA/Input switches to the relay card. I believe this picture is correct now. The relay control wires are connected to the Monitor Switch terminals that are normally open when the switch paddle is pointing to the output RCA jacks. The relay control wires are connected to the RIAA/Input Switch terminals that are normally open when the switch paddle is pointing to the input RCA jacks.
This picture shows more of the front panel wiring. I connected the wires for the Input Buffer Gain Switch, Output Buffer Gain Switch and Calibrate Switch. I also connect the left and right signal wires for the RIAA front panel RCA output jacks. At the back of the tester I ran the left and right signal wires for RCA output jacks to the soundcard.