Hi Thomas, interesting device, I would have expected a THD meter from B&O rather than this, I had no idea they made such a thing, the T100 from Nakamichi is a great tool for adjusting tape recorders and audio. With the screws, it's a problem that I found with a lot of other devices, the design of the stand itself is one thing, but unprofessional interventions when screws of a different length are replaced is a chapter for itself. DIN sockets with a switch were also commonly used with audio devices, for example to block inputs or disconnect microphones, etc., here it is cleverly designed to ground the input so that the meter does not detect interference due to sensitivity if the input is not connected. I have probably all albums from Erasure 🤔 but "K3 distortion" is not among them 🤣 The optocoupler reminded me of my youth when, during one of the experiments, I put a diode on one side and a photoresistor on the other in a piece of pencil body 😁 Nice day 🙂 Tom
Here’s what I think: The generator that emulates a tape channel should be set to add 1kHz and 333Hz tones. That’s because the AGC expects 333Hz tone to adjust the overall channel sensitivity. Then the 3rd harmonic result is correctly scaled relative to the fundamental. So the results you were showing with changing the 1kHz amplitude were really just showing how the AGC reacted to the “wrong” signal. Maybe you did have the 333Hz in the input signal as well - I didn’t catch that. The whole thing is probably calibrated in such a way that the AGC does not need to be selective. The AGC adjusts the sum of fundamental and harmonics, with the assumption that K3 dominates over other harmonics. Adding say 15% of K3 would cause a non-selective AGC to err low on the 333Hz reference level. But that can be easily calibrated out in the scaling.
Jeg har et magen til. Jeg har lige haft det delvis skilt ad, da det er lige så besværligt at skille ad som dit og mit er original maling. Ledningerne sidder samlet, bare i et pænere gul plastic rør. Skruerne til benene går en halv mm gennem bundpladen, så det er forkerte skruer der sidder i dit.
thanks a lot, maybe the feets gets a bit soft over the years, then people tighten the screws, and then shorts happens, due to now the screws are too long, bad design anyways a screw length variation in the last mm, must not cause a problem, more margin must be in the design
Hi Thomas, interesting device, I would have expected a THD meter from B&O rather than this, I had no idea they made such a thing, the T100 from Nakamichi is a great tool for adjusting tape recorders and audio. With the screws, it's a problem that I found with a lot of other devices, the design of the stand itself is one thing, but unprofessional interventions when screws of a different length are replaced is a chapter for itself. DIN sockets with a switch were also commonly used with audio devices, for example to block inputs or disconnect microphones, etc., here it is cleverly designed to ground the input so that the meter does not detect interference due to sensitivity if the input is not connected.
I have probably all albums from Erasure 🤔 but "K3 distortion" is not among them 🤣
The optocoupler reminded me of my youth when, during one of the experiments, I put a diode on one side and a photoresistor on the other in a piece of pencil body 😁
Nice day 🙂 Tom
Here’s what I think: The generator that emulates a tape channel should be set to add 1kHz and 333Hz tones. That’s because the AGC expects 333Hz tone to adjust the overall channel sensitivity. Then the 3rd harmonic result is correctly scaled relative to the fundamental. So the results you were showing with changing the 1kHz amplitude were really just showing how the AGC reacted to the “wrong” signal. Maybe you did have the 333Hz in the input signal as well - I didn’t catch that.
The whole thing is probably calibrated in such a way that the AGC does not need to be selective. The AGC adjusts the sum of fundamental and harmonics, with the assumption that K3 dominates over other harmonics. Adding say 15% of K3 would cause a non-selective AGC to err low on the 333Hz reference level. But that can be easily calibrated out in the scaling.
Jeg har et magen til. Jeg har lige haft det delvis skilt ad, da det er lige så besværligt at skille ad som dit og mit er original maling. Ledningerne sidder samlet, bare i et pænere gul plastic rør. Skruerne til benene går en halv mm gennem bundpladen, så det er forkerte skruer der sidder i dit.
thanks a lot, maybe the feets gets a bit soft over the years, then people tighten the screws, and then shorts happens, due to now the screws are too long, bad design anyways a screw length variation in the last mm, must not cause a problem, more margin must be in the design
Bang & Awful sound 😂….interesting product though.