![]() Are there any guides for isolation/troubleshooting of this kind of problem? Would anyone be willing to walk me through it in a sort of AK forum/chess-by-mail fashion? I would definitely commit to seeing the process through and posting the details here. ![]() I would like to troubleshoot the problem but don't really know what steps to take. ![]() as mentioned in another reply, the subsonic filter mitigates the problem (mostly).īased on use-case type testing, it seems that the problem has to be in the phono circuitry (preamp), doesn't it? My assumption is that if the failure were outside of the phono pre-amp the symptoms would be observed on other outputs. In some cases, the protection circuitry kicks on when this is happening (but not always). The behavior happens almost all of the time. The frequency of movement is in the ~1hz range. It's almost like an invisible hand is pushing and pulling on them. Even at low volumes, the woofers (both channels) move in and out in a very exaggerated, slow fashion. Phono 1 and Phono 2 both show the problem. Tuner, Tape out, and Aux do not show the problem. All turntables (when paired to the Sansui) show the problem. I have tried multiple amps and multiple turntables. I swapped out the speakers over the weekend so that I could better characterize the problem. can anyone point me in the right direction? For starters, which board should I be looking at? Does this sound like a familiar/known issue? Can you suggest any tests to help me isolate the issue further? I have searched the forums but didn't find anything that seemed quite the same. I have a manual and schematic and a meter but I am no electronics tech. As mentioned, it seems to be particular to the phono input only. Maybe not at "0" but it will do it with only very slight volume. The new power supply gets rid of the wall-wart, making the Musical Surroundings Nova 3 even quieter than before. This tends to sound a bit like thunder but sometimes it's more like low-frequency static. The third generation of this popular phono preamp has been designed by analog maven Michael Yee and features a discrete dual-mono circuit, subsonic filters and incredible flexibility when it comes to loading options. My question concerns those preamps which offer a 'subsonic filter' to reduce or eliminate rumble caused by vinyl imperfections. Symptoms: When the phono input is selected and a signal is present, the speaker woofers intermittently have "siezures" where they travel their full range of motion. Hello, After following the forum for a while I thought it was time to be more active and actually post something I have been researching phono preamps as I am currently relying on a built-in stage in my Onkyo amplifier. Phono amp and subsonic filter assembled as a single PCB.My AU-717 is currently out of commission: it seems to have some kind of problem in the phono stage.Īt first, I didn't realize the problem was related to the phono input, but after the process of troubleshooting I think that is the case. Power supply board mounted in vertical orientation. The green board is the one for bass/treble. Phono amp and subsonic filter assembled as a single PCB. The cost went up almost double due to the bass/treble board and dual control pots. A DIRECT switch provided for bypass the bass/ treble stage. I used a commercial bass/treble board for his purpose. In addition to the phono stage he asked Bass / Treble control also. In the same way I constructed another phono stage for our FM Vijayan. The phono stage board is bottom of subsonic board. The right side board is power supply board and left one is subsonic filter. Completed Final view Front View while working Rear View Inside View Please note after burn in period the LM4562 ICs performance are not up to my satisfaction and after few trials with different op amps finally settled with Texas make NE5532. Mirror image layout used for L&R channels for better sound balance and image. Shielded cables are used for all signal connection. PCBs are Common Purpose type and resin coat done on layout side of PCB after completion soldering and testing. In other aspects high quality solder led and gold plated RCA sockets used. The unwanted holes in the cabinets are so hidden. For the front face plate I used two layer commercially available silver color sheet which is commonly using for vehicle nameplates / stickers. The cabinet is a small commercially available FM stereo metal box. External 1A 16VAC wall adaptor used for feeding supply. Supply filters are f and 4nos 1000f electrolytic capacitors. The power supply is 15V dual type and constructed with regulator chips LM337 and 317 instead of conventional 78xx, 79xx series. All resistors used are low tolerance metal film type and electrolytic capacitors are Keltron make. A Sub Sonic Filter also added in the output of the phono stage. ![]() I used the circuit of Rod Elliott ESP phono circuit with National Semiconductors LM4562 op amps. Here are few phono Preamps which I built. ![]()
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