Thanks, Salas. Well, when I connect the module to the gen & CRO when it's out of the case (ie. just resting on the wooden work-bench):
#1. I have one half of an ordinary (coax) RCA cable with the RCA plug at one end cut off and the wires separated - so I can clip these wires to the input/ground wires. I have another half RCA cable (minus RCA) clipped to the output wires ... going to the CRO.
#2. When the modules are installed in the case, I use one half of an ordinary (coax) RCA cable from gen to input RCA on the case, with another half RCA cable going from output RCA to CRO (at the gen & CRO ends there are RCA-BNC converters).
I would've thought that if I am picking up RFI which is causing instability ... then this would happen more in #1, when the module is just lying on the bench? Yet this sine wave is stable?
Regards,
Andy
Sorry, Salas - how do I "engage the line trigger"?
I normally plug the output into one of 2BNC sockets which say "1Meg 25pF" (two channel CRO.)
But there is a 3rd BNC socket - this one says "Ext Trig" ... do I plug the output into this BNC, instead? Or do I plug something else into this BNC, to engage the line trigger?
Thanks,
Andy
There is trigger options menu if using a DSO or a physical switch if using an analogue cathode ray oscilloscope that usually has AC DC HF LF LINE trigger mode. External trigger input is to sync a source that gives trigger pulse, not of use in this test. Line triggering synchronizes trigger to mains frequency.
Hi Nick, I'm done with my linkwitz subsonic filter. After several experimentations I did find out that my initial 15Hz -6db attenuation calculation point was too low and I still heard flipping woofing. For my setup it should be set to about 30Hz initial point then it is working right. To be exact, with 15n and 243k I have 30.8575Hz.
Question to experience guys: due to many tests, I ended with the usage of CMF55 Vishay 1% 100ppm now. Does it make sense for such filter type to replace these with more precise resistors like Vishay PTF 0.1, 5 or 10ppm?
Question to experience guys: due to many tests, I ended with the usage of CMF55 Vishay 1% 100ppm now. Does it make sense for such filter type to replace these with more precise resistors like Vishay PTF 0.1, 5 or 10ppm?
The distortion contributed by the 100ppm is so low that most here cannot measure it.
In fact the very few that can measure it have to use very sophisticated procedures that those operational test conditions rarely apply to our amplifiers.
Just ensure all the feedback resistors run cool.
243k & 15nF seems too high a resistance.
Would 24k and 150nF work as well?
In fact the very few that can measure it have to use very sophisticated procedures that those operational test conditions rarely apply to our amplifiers.
Just ensure all the feedback resistors run cool.
243k & 15nF seems too high a resistance.
Would 24k and 150nF work as well?
Did you ever measure the room response nodes when your large self powered subwoofer is on? If a system is overbearing the room down low, the final response maybe actually extends more than the electronic filtering suggests. Its an electrical and acoustical outcome. If the system still sounds fleshed out with natural weight then don't worry about highish filtering frequency on paper. Vinyl does not carry much real modulation below 30Hz anyway. As for resistors PPM, as Andrew said. Especially in the low bass the transducers distortion, room nodes, and ear brain slow integration don't permit details. Its a matter of even coverage and low reverberation. Beyond bass PEQ band points for even FR that digital processors offer, the reverberation is still a dimensional and structural matter that big basstraps try address to make a smaller room appear larger.
I see. Thank you for all details.
It is room temp in that build and no components that produce heat.
I see. Thank you for all details.
It is room temp in that build and no components that produce heat.
I tried to stay with the range of 15-33nF for caps and played with resistors. I did not put attention to “How critical” for OPA2134 such high resistance vs. change of capacitance.
Can that tandem modification (like 150nF and resistors in range of 20ks) can change my slope shape (to make it more stiff falling from -6dB at 30Hz to -24dB)?
If yes, then I can go lower then 30Hz for -6bB. Previous tests (15nF with 499K and till 262K) indicated that 15->22->28Hz still give me the woofing. 243k resolved it with about 31Hz.
My room is quite big (11Mx9M) with about 4m celling height. I did not measure acoustic responses in my room (have no equipment), but I do have some mild resonating effect. I hear on some furniture in that room since its vibrating on low frequency. But it is very mild. Absorption is also not that bad. Carpet floor and all walls are decorated. In general I like the sound now, but I remember it was more punchy when I used it with CD and no Linkwitz. I assume it is due to slop that starts at about 34Hz, then 30.8Hz with -6dB and go down till -24dB. I assume miss some 20s. May be Andrew is right and I use wrong resistors (243k is too high for this opamps).
The room is not small, but it is a room not a hall. To have music hall quality bass (nodal region up to 20Hz only) it takes a... music hall. Obviously the woofing is not a function of bass response alone but air and structure vibrations traveling feedback to the TT. You most likely attenuate better a resonance region that the TT suffers at as long as you go higher in filter frequency. Make sure of your resistor values and frequencies. After defined and evaluated, if not absolutely satisfying, there is always the measurement and DSP bass management final frontier prospect for the subs. These days such stuff is very reasonable economically and well documented. Two channel home bass does not need the most transparent and expensive DSP gear. Its not an arena reinforcement line array system to control...
Not for long before the bug bites again. Goodbye nice decorations, hello ugly panels & diffusers
Guys, I need your advice. The best way to isolate power transformer magnetically (or electromagnetically) is to use it in separate box. Air distance is a friend here.
Here is my question: If not way to use stearate box, then what is the best isolation material to box it inside the same chassis (like to make an isolation wall) : aluminum, copper, iron? Also what about thickness?
Here is my question: If not way to use stearate box, then what is the best isolation material to box it inside the same chassis (like to make an isolation wall) : aluminum, copper, iron? Also what about thickness?