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
In finishing up the front panel wiring I decided I didn't like the way I ran the power to the power switch and transformer. So I re-worked that part. Here is the front panel in its completed state (I hope).
...and here is the reworked wiring on the power supply transformer. I can't unplug and pull out the power supply board without unsoldering a wire at the power plug but there is enough slack in the wire that I can pull the board and turn it.
The front panel wiring wasn't quite complete. I missed running the input L/R signals to the relay card. This updated picture is with that wiring added.
With the front panel wiring complete, that leaves the front section PCB to main board wiring and the rear section PCB to main board wiring. This picture is the rear section Relay Card I to main board wiring.
Here is the rear section of the tester wired up. The loose green, chassis ground wire is for the transformer shield when I add it (later). I will have to add a small piece of insulating material between the power supply components and the output buffer PCB.
The only remaining front section wiring to complete is the wiring between the (smaller) relay card and the main board. This picture shows that wiring. I think the audio tester is ready for assembly. I have some thin copper and tin sheets to make the shield that covers the transformer but I think I will wait a bit on that construction.
Hi John
Its looking really great.
/Frede
Thanks Frede
I assembled the tester this morning. To provide a barrier between the output buffer PCB and the power supply, I used a couple dabs of tacky glue to attach small pieces of Dura-Lar to the tops of the tall capacitors. This picture shows the Dura-Lar pieces and the assembled tester.
Here is the assembled tester with power applied.
My next step is to clean up my work bench, put all of the parts away, then install the audio testing software and check the tester out. I will also need to start making the shield for the transformer. Comparing my tester with Frede's, I see now that I installed a 5-pin DIN jack on the panel for the phono input. I have an adapter for that DIN to a right and left RCA jacks. I'll see how that works for me. In the future I might want to pull the front panel and change the DIN jack to a 7-pin. Most of my turntables have RCA plugs though.
The reason for the 7 pin DIN jack is some of the B&O turntables have the DIN7 plug. Then I don't need to remove these two data pins before testing..
Here is a picture of the audio tester connected to the Creative E-MU 0204 (USB 2.0 Audio Interface).
sonavor: Here is a picture of the audio tester connected to the Creative E-MU 0204 (USB 2.0 Audio Interface).
Amazing job John, cant wait to see test results and how to use those, and how to do it. I may start saving my pocket money to build one, your total cost with all the software and hardware will be appreciated too
Collecting Vintage B&O is not a hobby, its a lifestyle.
haha...you can send stuff you want to donate to me :). I am just a novice. Thank Frede for sharing his expertise with us. I am looking forward to using this soon. This has been something I have wanted to be able to do for a long time. I will post some pictures of testing out the tester functionality soon. Once I get it all ready to use I will check out one of my Beomasters (probably my BM 4400).
Rich:So....when can we start sending you stuff to test? Nice work. Always impressed with your ability to see a project through.
Nice work. Always impressed with your ability to see a project through.
Agree, and yes, this should be our US BeoTest station
I have checked out all of the input and output connections. I had a couple places where the left and right channels were switched so the input/output testing flushed those problems out. This picture shows applying a 1K Hz test signal on the left input RCA jack and measuring the output of the tester. The yellow scope probe is measuring the input and the red probe is measuring the output. The trim pots on the Input Buffer board provide adjusting the output voltage to match the input. For these tests I used an external signal generator and oscilloscope. I think I am ready to try out the USB sound device and the PC audio software.
I started testing the audio tester inputs and outputs with the E-MU 0204 USB Audio device. My PC I am using on my bench is an older Shuttle computer I built back in 2006. It has Windows XP, some virus checking software, a PDF viewer and now the audio software for testing (TrueRTA and audioTester v3.0). I only have the free versions of the audio testing software installed right now because I wanted to see if the PC I am using has enough capability to handle it.
This first picture shows the Classic Audio Tester with the rear RCA jack inputs and outputs connected to the E-MU. I have my oscilloscope connected to the right channel monitor RCA jack of the tester. The TrueRTA software is supplying a 300 Hz Triangle waveform to both the left and right inputs at the rear of the audio tester. I have the audio tester calibrate switch engaged so it wraps the rear inputs around and back out (the rear outputs) so the TrueRTA software can measure/display its own signals on the software oscilloscope.
I think I am ready to make the shield that goes around the transformer and put the top cover on the tester. I will have to return and adjust the RIAA Input cards later because I don't have what I need to generate a good phono level (2mv - 9mv) test input. Hopefully the attenuators I ordered today will do the trick. I also need to continue reading up on how to use the testing software before I can try testing my first audio component.
The RMAA (RightMark Audio Analyzer) software is what Frede recommended and I believe is what Bo used earlier in this thread. I decided to give it a try to see what sort of results I get with the current state of my tester. My results at this point are in the neighborhood but not as good as what Bo measured on his completed tester. The screenshot of my first test is shown here. I will re-measure as I add the transformer shielding and check the calibration settings again.
I ran the same calibration test on the Audio Tester (using the RightMark software) at a higher resolution/sample rate and got better results. This test was with 24-bit and 48kHz
sonavor: I ran the same calibration test on the Audio Tester (using the RightMark software) at a higher resolution/sample rate and got better results. This test was with 24-bit and 48kHz
I ran my test 96khz 24-bit, but i had to fiddle a lot with soundcard drivers and settings before i got the results i wanted. I have the E-MU 0202 soundcard, and I think the 0204 should slightly better regarding the noise level.
When i started the I first omitted the soundcard buffer and just had a closed loop with only the soundcard in the loop. I then tuned everything (the computer settings) to get the best result before introducing the soundcard buffer into the loop.
I also used RightMark.
Best wishes.
//Bo.A long list...
I added the shielding around the transformer this morning. I used a small sheet of copper I bought at a hobby store.
BO: sonavor: I ran the same calibration test on the Audio Tester (using the RightMark software) at a higher resolution/sample rate and got better results. This test was with 24-bit and 48kHz I ran my test 96khz 24-bit, but i had to fiddle a lot with soundcard drivers and settings before i got the results i wanted. I have the E-MU 0202 soundcard, and I think the 0204 should slightly better regarding the noise level. When i started the I first omitted the soundcard buffer and just had a closed loop with only the soundcard in the loop. I then tuned everything (the computer settings) to get the best result before introducing the soundcard buffer into the loop. I also used RightMark. Best wishes. To check the test signals prior to running the RightMark tests I have been using TrueRTA. I was seeing a 7mV difference in my left and right channel signals. The left channel was a little lower. This occurred both when using the Audio Tester calibration mode and when moving the E-MU output to the Audio Tester front panel inputs. I finally thought to just do the E-MU wrap around test (inputs to outputs) and re-measure there. The difference was still there so I used the left channel control on the front of the E-MU to bring it up to the same level as the right channel. Now I have re-run my RightMark tests. Here are the test results for the tests using Audio Tester calibrate mode (E-MU inputs and outputs connected to the normal, rear connections of the Audio Tester).
To check the test signals prior to running the RightMark tests I have been using TrueRTA. I was seeing a 7mV difference in my left and right channel signals. The left channel was a little lower. This occurred both when using the Audio Tester calibration mode and when moving the E-MU output to the Audio Tester front panel inputs. I finally thought to just do the E-MU wrap around test (inputs to outputs) and re-measure there. The difference was still there so I used the left channel control on the front of the E-MU to bring it up to the same level as the right channel. Now I have re-run my RightMark tests. Here are the test results for the tests using Audio Tester calibrate mode (E-MU inputs and outputs connected to the normal, rear connections of the Audio Tester).
That new test result was a little better but the Stereo crosstalk measurement was down a bit. I ran the RightMark tests again but with the E-MU outputs on the Audio Tester front panel input instead of using the calibrate mode. That test result is in this picture.
I think my Audio Tester is ready for some tests on a piece of audio equipment. I still have to resolve my RIAA boards in the Audio Tester. The 40dB gain isn't working correctly. The odd thing is that the problem is on both boards. I have checked the boards and they look correct. I am going to test the RIAA boards stand-alone ... outside the Audio Tester. Maybe there is a problem with the OpAmps.
It appears my RIAA Amp board problem may be that I don't have a clean enough input signal down at 2.5mV (1k Hz). I checked the two RIAA boards over a couple of times and even replaced components (electrolytic caps, the two 47k ohms resistors, the C1 poly cap and the Op Amp). I also pulled the 5k ohm trimmer resistor to check its setting. After doing all of that, I still get bad results in testing the input and output of the RIAA section. This first picture is of the reworked board.
The reworked boards did not change the RIAA amp test results. In looking at the signals used in my test - When there is no 2.5mV, 1k Hz test signal applied, I still see some noise on the input line. When 2.5mV, 1k Hz is applied you can sen there is noise present. The noisy 2.5mV affects the RIAA amp output and that is what I am seeing. I can skip and come back to the RIAA problem later if I want. Here are what TrueRTA shows in measuring the test signals for the RIAA test.
It looks as you don't have capacitor C1 mounted! Is that on purpose?
BO: It looks as you don't have capacitor C1 mounted! Is that on purpose?
The purpose of C1 is for another application with inputfrom the motherboard.
classic: BO: It looks as you don't have capacitor C1 mounted! Is that on purpose? The purpose of C1 is for another application with inputfrom the motherboard. /Frede
As Frede replied, the C1 is not needed for this application. I originally had it on the board but I removed it just to see if it was part of my problem. It wasn't. The C1 cap is in the path that goes to the board connector but it doesn't go anywhere beyond that.
-sonavor
I haven´t tested my RIAA card in any other way than listening, but they sound excellent!
I might just try that next. Did you do any adjustment of the gain trimmers on your boards?
sonavor: I might just try that next. Did you do any adjustment of the gain trimmers on your boards?
Only on the input buffer card, to get the signal level as close as possible to the the levels with the closed loop (without the soundcard buffer).
The riaa trimmers I haven´t adjusted yet. I'll think need to my hands on some test record before I do that.
BO: sonavor: I might just try that next. Did you do any adjustment of the gain trimmers on your boards? Only on the input buffer card, to get the signal level as close as possible to the the levels with the closed loop (without the soundcard buffer). The riaa trimmers I haven´t adjusted yet. I'll think need to my hands on some test record before I do that.
Yes, I am looking for some good test records as well.
I had some success on the RIAA boards today. Deciding to go the route that there is too much noise coming from the signals generated by the PC E-MU device going through attenuation in the Audio Tester, Frede suggesting I use an mp3 device to produce the simulated phono signal. That works quite well. I installed some mp3 sine wave signals on an iPod Nano and created a playlist I could loop for the 1k Hz file. I also have a couple of cables that connect to an iPod headphone jack and to a 5-Pin Din plug (and another to RCA plugs). The result was a nice clean 2.29mV, 1k Hz test signal. I checked the signal with TrueRTA first and then applied it to the RIAA board inputs. Then I measured the RIAA board outputs. The results are in the picture below. The top picture shows what the output of the iPod looks like. It is a clean sine wave. The second picture is with the iPod feeding that signal to the Audio Tester Din phone jack and TrueRTA measuring the RIAA amp output. I still can't get a 40dB increase. The RIAA board gain trimmers do affect the signal now. When I reworked the RIAA board yesterday I preset the trimmers to 1k ohms. In the picture below I had to turn the trimmers fully (clockwise) to get the maximum output which is around 150mV. It should be about 220mV.
This is odd to me. Applying my nice 2.29mV, 1k Hz sine wave to the phono input of the RIAA amp board, I get a clean 1k Hz sine wave amplified to around 150mV whether measured from the RIAA output RCA jacks on the front of the Audio Tester or from the RCA output jacks at the rear. Both measured by TrueRTA. I verified the measurements with my DMM and my external oscilloscope. However, when I use my external oscilloscope directly on the RIAA output pins, I get around 250mV which is much more like what is expected. I tested with some different cables and get the same result. I also tested by measuring the RIAA output through the front panel monitor RCA jacks. The same thing.
Here is a picture of the RIAA amp left channel output as measured by my oscilloscope in two places. The red sine wave is measured at the Audio Tester left channel monitor outputs. The yellow sine wave is measured directly on the RIAA amp output pin. Note that the output pin where that measurement is take goes directly to the front panel RIAA output RCA jack that the TrueRTA measurement measures 155mV. So I am seeing a loss somewhere in the RCA audio jacks?
sonavor: This is odd to me. Applying my nice 2.29mV, 1k Hz sine wave to the phono input of the RIAA amp board, I get a clean 1k Hz sine wave amplified to around 150mV whether measured from the RIAA output RCA jacks on the front of the Audio Tester or from the RCA output jacks at the rear. Both measured by TrueRTA. I verified the measurements with my DMM and my external oscilloscope. However, when I use my external oscilloscope directly on the RIAA output pins, I get around 250mV which is much more like what is expected. I tested with some different cables and get the same result. I also tested by measuring the RIAA output through the front panel monitor RCA jacks. The same thing. Here is a picture of the RIAA amp left channel output as measured by my oscilloscope in two places. The red sine wave is measured at the Audio Tester left channel monitor outputs. The yellow sine wave is measured directly on the RIAA amp output pin. Note that the output pin where that measurement is take goes directly to the front panel RIAA output RCA jack that the TrueRTA measurement measures 155mV. So I am seeing a loss somewhere in the RCA audio jacks?
I have made the same test to my Audio Tester and got the following result:
iPhone output: 3.12mV (This signal to the DIN5 input of the RIAA Amplifier)
Phono output: 316mV (this is the output directly from the RIAA - the phono socket on the front of the Audio Tester)
Monitor : 315mV (measured by the monitor of the Audio Tester - the monitor with gain 1 and monitoring the RIAA output)
TrueRTA: 315mV (measured on my PC / Soundcard 0204 --- the output on the backside of Audio Tester)
My RIAA amp gain is about 1% too high.
So there is really something strange by the results John see. I can't see any logical explanation at the moment.
classic: sonavor: This is odd to me. Applying my nice 2.29mV, 1k Hz sine wave to the phono input of the RIAA amp board, I get a clean 1k Hz sine wave amplified to around 150mV whether measured from the RIAA output RCA jacks on the front of the Audio Tester or from the RCA output jacks at the rear. Both measured by TrueRTA. I verified the measurements with my DMM and my external oscilloscope. However, when I use my external oscilloscope directly on the RIAA output pins, I get around 250mV which is much more like what is expected. I tested with some different cables and get the same result. I also tested by measuring the RIAA output through the front panel monitor RCA jacks. The same thing. Here is a picture of the RIAA amp left channel output as measured by my oscilloscope in two places. The red sine wave is measured at the Audio Tester left channel monitor outputs. The yellow sine wave is measured directly on the RIAA amp output pin. Note that the output pin where that measurement is take goes directly to the front panel RIAA output RCA jack that the TrueRTA measurement measures 155mV. So I am seeing a loss somewhere in the RCA audio jacks? I have made the same test to my Audio Tester and got the following result: iPhone output: 3.12mV (This signal to the DIN5 input of the RIAA Amplifier) Phono output: 316mV (this is the output directly from the RIAA - the phono socket on the front of the Audio Tester) Monitor : 315mV (measured by the monitor of the Audio Tester - the monitor with gain 1 and monitoring the RIAA output) TrueRTA: 315mV (measured on my PC / Soundcard 0204 --- the output on the backside of Audio Tester) My RIAA amp gain is about 1% too high. So there is really something strange by the results John see. I can't see any logical explanation at the moment. /Frede
Thanks for checking Frede. I bumped my test input up to about 5.1mV to see what the result would be and RIAA outputs were 389mV. So it is pretty much the same amount of gain. My problem must be related to the Op Amps, the R1 trimmer, R4 and R3, right?
The capacitor C3 = 4.7nF in the RIAA circuit (it looks like during the different drawing versions I have made an error and used the value 47nF)
I am really sorry for all your work by finding the reason for the problems of getting 40dB gain.
I found out the error by going all the way back to my simulation circuit and compared with the circuit in the PDF file.
In my own RIAA I have used 4.7nF that explains why I get the correct measurements.
classic:The capacitor C3 = 4.7nF in the RIAA circuit (it looks like during the different drawing versions I have made an error and used the value 47nF)
I can confirm that I used 47nF. I'll change them to 4.7nF. Since i never really tried to tune or use the RIAA card i didn't notice (couldn't tell by hearing)