So far I've been very happy with my LM508. The biggest issue has been trying to reduce transformer hum. I've played with the hum balancers and have it reduced about as much as I can from the speakers. I've also put in an Emotiva CMX-2 that has DC offset to try and reduce some of the mechanical hum. That helped a little. I'm also going to try the AVA Humbuster, but waiting for arrival. One big improvement was adding better feet. I didn't want to spend a lot on the Isoacoustics, even though I like their products. So I'm trying vibrapods with cones and I also tried something from Herbies, but they were too small and I don't want to have to remove the stock feet. I'm also trying Pangea feet, but those also haven't arrived yet. The vibrapods are actually working very well (using 5 to support the weight of the amp, and might add 1-2 more if I keep this option). The issue with the vibrapods is that they're known to possibly leave black marks. I might have to get some plexiglass cut into disks to sit under them. Anyway, even though I've made improvements, one issue that continues is vibration and hum from the transformers. While adding the feet has helping with vibration coming through to my cabinet (it was really audible) the transformers really vibrate and hum on their own. It is clearly audible. When I touch them you can really feel the vibration. My Primaluna didn't do this, or it was really minimal. I'm wondering if any of you who have this amp also feel the vibration from the transformers when it's on? Is this normal?
If he charges a reasonable amount, another upgrade you can eventually do is change the capacitors. Thinking of doing that in a couple of years.
Firstly, something like the humbuster won't help at all as it's designed specifically for grounding issues. Transformers can hum. It's the luck of the draw. Some do, some don't, and the ones that do either hum very little or somewhat. You're not supposed to hear it from your listening position. In fact, most phono preamps will make more noise than that. If it's still under warranty and you can easily hear the hum from where you're sitting, contact your dealer to have it repaired. Otherwise, don't worry about it.
Mine hums to. Seems like more with some tubes and less with others. From the front it's the right transformer. If I push it I can most of the time make the hum less. The hub balance screws work great in my case. Again when changing tubes it needs some tuning in my system and I can get the speaker hum to a minimum. The mechanical hum from the transformer is there all the time and mostly affected by the bad AC caused by my heater. I've had same issues with my Naim Nait XS. However not with my Naim Supernait. That one is dead quiet both mechanically and in the speakers.
A little while after posting that message I tried touching the transformers again and no vibration, or it was minimal. The amp had been on for over 3-4 hours at that point. Maybe it gets better when really really warmed up? I've gotten the hum in the speakers to a minimum. You have to put your ear up to the tweeter to hear it. I've just never heard transformers vibrate quite like this and after reading about how yours blew I was concerned. I guess its normal.
There are plenty of options! Caps cost quite a bit so it's important to do your research and to look into each specific measurement you would need before buying anything. This member upgraded his. Read his post for more info. New Line Magnetic 508ia Integrated Amp Yes, it is... to a degree. If you can't hear it from your listening position, there's no issue. Some transformers make noise but only if it can be heard from where you're sitting is it problematic.
Just wanted to add that my 508 have been working great since repair. Even better now since he also tightened the transformers so mechanical hum is now totally gone. Great!
"tightening the transformers....".... is that as easy as taking the bottom panel off and tightening some screws where the transformers are?
Sorry I don’t know but I would guess so. I actually got less speaker hum too. System got extremely silent after this.
I’ve learned that pre amp tubes are not that sensitive to matching iff the amp have feedback controls. But what about output tubes such as 805? I have a pair of original LM 805 available but the seller doesn’t know if they are matched or not.
No, the preamp tubes do not need to be matching in this amp. I believe this was mentioned numerous times in the thread but it *is* 42 pages so... Interesting question. Typically, power tubes should be matched but that is usually because the bias control is for all of the tubes. If one amp has 4 power tubes but only one bias knob, it will uniformly change the bias for all sockets at the same level. However, the 508IA has individual bias knobs, one for each socket. I would suspect in such a case that it doesn't matter if they're not matched as if one of the two tubes requires to be more aggressively biased to output the same amount of juice, this amp allows you to do so. As long as they measure around 120 on each dial, you're OK. It's if the bias keeps drifting heavily that a tube should be changed. Technically, if one tube dies, you can just buy a single one if you want... but most use the excuse to upgrade anyway.
This is good info, thanks. Hate to keep banging the same drum but I'm still dealing with quite a bit of vibration and hum from my 508. After reading about dianos's experience I'm wondering if my 508 is acting as it should. I don't have a local dealer, although I purchased from an authorized dealer so this isn't a grey market unit, and I don't know anyone in Portland with a 508, so I can't tell if what I'm dealing with is normal. What I would say is that the hum and vibration is sometimes not bad and other times really noticeable. Yesterday I was home alone for a couple hours and was listening to music at normal levels and at first the hum wasn't bad. However, after about 3 hours I noticed it (its more mechanical and not coming from the speakers) and put my hand on the right transformer (or whatever is in the black box on the right) and it was vibrating noticeably. The entire chassis was vibrating but I really noticed the back right box. It was also warmer than the other black boxes. And, in the past week or so I've noticed a couple instances of "static" sound coming from the right channel. It lasts maybe a second or less and isn't consistent -- probably happened 4-5 times but like I said very brief. I thought maybe its something from the DAC or streaming service, but now that I'm noticing the right side vibrating and this sound is also coming from the right channel I'm beginning to think something might be up. I will likely contact my dealer to see if he thinks it might be an issue, but I'm just trying to determine if my 508 is operating like it should. Could it be a bad tube? I'll swap the L/R power tubes next chance I get. I'm also going to Phoenix for work at the end of next week and there is a dealer there so if I get time I might try and go in just to feel/hear their unit (if one is on demo) to see if it's like mine. I guess I'm just wondering from other owners if they can feel their 508 vibrate? Is that normal? Thanks, Adam
What you describe sounds more or less identical to the mechanical hum I had from the right transformer. When I pushed it I could change the amount of hum from pretty much to lower but never remove it completely. Mechanical vibration could also generate heat, however the 508ia will always get extremely hot which is how it is made. During my repair my tech tightened that transformer and since then my 508 has been totally silent. I also remember I had to work the hum screws before this tweak due to speaker hum and now it's silent all the time. For a person knowing repairs it should be an easy fix so I would recommend looking into this if it's disturbing because if same as me then it can be fixed. A recommendation when swapping tubes. Be sure to let them cool down before removing them and starting the amp up again. It's a big machine with 920 volts on the 805s that want to discharge. Manual says 2 minutes but I would wait 20 minutes to put less stress on everything. If you get popping sounds from the speaker now and then then it can be a sign of worn out tubes. Small metal particles can get loose inside the tube creating these pop noises. In my case a bad tube first made pop noises, then total silence and then a couple of resistors and a capacitor blew. I assume my faulty tube was a major failure. Not sure how often this happens to tubes though.
Transformers may or may not hum and may or may not hum loudly but no way should it be vibrating. Contact your dealer. Have them exchange the unit or have it repaired with LM's parts and to their standards.
Not exactly true. Brand new tubes can have this problem as well. It's called microphonics. If a tube is microphonic, it can display this type of behavior (or much worse). For instance, all 6SN7s are microphonic to a degree. But if one tube is more microphonic than normal, these sounds can occur. It would be a pretty easy test to see whether in this case, it is related to the tube. Swap the tubes and see if the Left channel now has that popping sound. My guess is the problem is more likely to be a defective transformer.
I have been demoing a 508ia in my home for the last week and i`m a little confused and quite frankly disappointed. Compared to my 518ia focus and imaging are lacking, voices sound thin and tone is off. There is a lot of detail i will give the 508ia that but it is all over the place with some smearing. Has anyone else experienced what i have? Is this the DNA of the 508ia?
Stock tubes. It belongs to a local dealer Venice Audio in SoCal who was kind enough to let me demo the unit. I have read so many positive things about this amp i thought that i would try it many former owners of the 518 have switched to the 508, i`m just wondering if tube rolling would be enough.
To make it fair i put the stock tubes back in the 518. Voicing and instruments sound natural with the 518 but off with the 508.I guess i`m wondering if others have experienced the same and it was corrected with tube rolling.
Mine sounds terrific. I'd suggest trying another 508IA just to be sure what you're hearing is normal.
