I've read about transformer hum before. Not normal. I'd definitely contact the dealer if it's still under warranty.
Transformer hum is really actually quite common in lots of gear. However, if the amount of hum has increased greatly from what it typically was before you made the tube swap, then there is a chance something else is going on.
Yep I swapped back the original tubes and it is still there. Something is definitely wrong. yea i tried adjusting the hum balancer to no avail. I swapped back in the old tubes and the hum is there. Contacted my dealer and he helped me out. I just sent it into the tech. Hopefully she comes back ok. Yea, its when i turned it on last night the hum was VERY loud. Definitely not the normal hum. And also the hum is general coming from the speakers but this was 100% coming from the amplifier. I unplugged everything (speakers, inputs etc.) and same thing. Sent it in to the tech today. Fingers crossed. Thanks for all of your replies guys.
Hello Guys, Has anyone tried the LM-508 with a SS preamp? If so, wich SS preamp? did it make a big difference in sound or not? Thank you!!
The tech received the amp said he heard no hum. Not a good sign. Will hopefully have more news this week.
Hello Seafinch, I've got my 508 last week and even it is brand new, only about 25 hours of playing, and the valves need to burn more, I'm getting the same ear fatigue as you were and IME I'm not sure this "little" shrill in the high mids is goint to dissapear using the valves more time, maybe smooth out a little bit, but not dissapear. My valves are quite similar from what you had in your 508. I have: original Psvane 805 + Shuguang WE 300B + Shuguang WE 6SL7 + Shuguang Treasure 6SN7. I got them from my supplier in China, instead of the original valves, on my request. I am thinking about rolling some other tubes (after waiting for a while to burn the valves more) and I would appreciate if you could tell me exactly what 6SN7 valves you got to smooth thing out, along with the JAN 6SL7GT. Thank you!
Hey Pedro, the tube that actually made the biggest difference in that regard was the Mullard ECC35 (6sl7), in fact it made the biggest difference on the overall sound of the amp versus anything else I've tried. It's hard to find and not cheap, but totally worth it.
Pedro, without purchasing anything new, try placing all the stock tubes back in the amp. It is highly musical in stock form form but lacking bass definition, details, extension, and a few other technicalities.
@Seafinch Can you please describe the qualities of the Mullard ECC35? I am looking for a 6sl7 that will add some sweetness/goldenness with increased decay, yet not take away from resolution and detail. Something more mid-centric. @Pedro Guillemain Sorry, I missed the part where you stated you didn't have the stock tubes. IME the Psvane 805 tubes need to be paired with tubes that ameliorate its highly resolving and somewhat dry nature. Seafinch's idea will be a step in the right direction. I must add though that they smoothen out somewhat over time.
@adamaley I think the Mullard is exactly what you're looking for - it does that Mullard midrange magic thing and definitely smooths out and sweetens the top end without sacrificing details. It's really amazing. The low end is great too - only tube I've tried that bettered it for the lows was the Ken Rad 6SL7GT (VT-229).
Thank you Seafinch and Adamaley for the tips. I will look on the Mullard 6SL7. Have you tried any NOS RCA or Silvania 6SN7 on the 508? Have you tried any good tube preamp?
I've tried 6sn7 - Sylvania JAN CHS 6SN7WGT 1950's HYTRON JAN CHY 6SN7GT 1950's 6sl7 - RCA 5691 Red Base, Black Plates STANDARD 33S29B Mullard (will get them next week) they are all great tubes and i need some more time to learn the differences. at the moment i prefer the RCA+SYLVANIA combo. waiting for the mullard i would also love to try RCA grey or Kenrad for the 6sn7's
I got the Mullard recommeded by @Seafinch yesterday (a Philips branded version). It is a very refined tube, and it breathes a lot of life into the music. It does however overshoot my system past the point I was trying to take it. I am currently close to the center of what I want things to sound like, and I needed just a smidgen of a push to get there. The Mullard is definitely a great option to tame an overly aggressive system yet maintain the details. Unfortunately, so far, I'm missing some degree of impact/punch with it. I intend to let it burn-in for a week or so. It definitely sounds better with the EML XLS 300bs in the amp. It complements it almost perfectly, however, I can't live without what the Elrogs bring to the table, so I am back to the drawing board. I'm so close to what I want, I feel that maybe cabling may be the way to go rather than tubes.
A mish mash. I have Cardas speaker cables, which I'm not in a position to experiment with because I need 15 feet runs. I use Verastarr Grand Illusions as power cords, custom XLR to RCA Acoustic Zen interconnects from DAC to amp (can't remember the model but I had them made by Acoustic Zen so I could take advantage of the preferred XLR outputs from the Schiit Yggdrasil DAC. I use an Audience AU24SE AES/EBU as cabling from Mutec to DAC, and finally, a TotalDAC USB cord from Microrendu to Mutec.
I'm selling my Line Magnetic 508ia amp. I've added almost $1500 worth of upgraded tubes - NOS United 805, Psvane WE 300B, Bugle boy 6sn7, several 6sl7 (tung sol, RCA redbase, etc) with less than 75 hours on them. I've used it with Allnic L300 Mk2 which takes them to a new height (makes it a bass monster and warms up the sound). The Allnic is also on sell. I'll post it on audiogon/usaudiomart soon. But I thought I should let this thread know first as this is where I learned about this beautiful amp.
