I wouldn't change the 805s right now. The Sylvanias are almost certainly the cause. Airy and open top-end is good but having two Sylvania types is too much of a good thing. Get a Mullard ECC35. That'll change the amp completely for the better. Which setting of NFB do you use? Have you tried a lower setting? If so, what were your thoughts?
I had tried Syl vt229 and found its treble rather dark. Thus it will not help to change Syl vt 229 into other 6sl7 tubes. But Focal speaker have tendency to sound hot. You may get 6n8s tubes made in 50's from Ebay. A pair of them cost around 100$. It will sound less hot than Syl vt231. Syl vt 231 and TSbgrp can sound hot with bright system like Focal. On the other hand, Amperex 6sn7 made in 50's or RCA gt black bottle may make it sound rounder. Shootout of Nos 6sn7 tubes Amperex is the best choice for old rock but may sound too dark with warm speaker like Harbeth. Cossor will sound rounder than stock tubes, but Acme may make yous speaker sound hotter despite its good transparency and excellent details You may try to cure the sound of your speaker through cable rolling rather than tube rolling. Another option is to add power conditioner to your amp and Dac.
great info guys. I might be able to repurpose and/or borrow some other 6SN7 tubes to see if helps, and also play around with cables. Looks like ACME 805 might not be the tube for me, and Cossor is something to be considered.
Ok, interesting. So we both use TS 6SN7 BGRP's and NFB 2 yet have different opinions of 5691 vs ECC35. I still am not sure I have a good ECC35 tube as my first impression when I received it was not entirely positive. And I know that the consensus outside of this thread is that the ECC35 is a more musical tube than the 5691. That said, others on this thread have preferred the 5691 (and TS 6SU7GTY) over the ECC35 in the LM 508/805. Horses for courses I guess.
there is so much untapped potential in this amp. Back in December I purchased a bunch of upgrades parts for the LM508IA. well I went for a trip and then after coming back the world flipped upside down and then I got sidetracked with another project, so I left most of them uninstalled until now. Tonight I went ahead and made the first addition. 1. 6SL7 power supply capacitor It has long been my suspicion that the 6SL7 has the most effect on the sound of the 508IA (you guys already know that) and it make sense not only to roll the best / most appropriate tube here, but also to up the quality of the component around it. Since everything sources from the power supply, and each half of the 6SL7 has it's own capacitor as its local storage, it made sense to start from swapping out the 6SL7 power capacitor. From factory, the 6SL7 power cap is a pretty cheap Nichicon general purpose capacitor. I upgraded it using a Mundorf Myltic cap bypassed with a Mundorf Aluminum Oil cap. While I am sure there are better option for those values, the lack of space limits to those 2 smaller components. The sonic difference is really quite apparent even without any burning in. Across the board it is better, but most pronouce is more detail/texture on each instrument; a better sound stage depth and layers; a faster presentation with more immediacy; and sounding less (but still silghtly) harsh. (I am still using Syl VT229/Vt231). I still have a lot of parts to upgrade. Will take my time to listen and learn about how each one affect the sound and let you guys know.
Does anyone having a listing of what parts were upgraded from the 508ia to the 805ia? I suppose I'm hoping that my 805ia would benefit less from upgraded caps etc than the 508ia since many were already upgraded to Mundorfs I believe.
Thanks...not sure I'm THAT curious but who knows....perhaps I will do that at some point. I may ask the dealer.
They won't know either. LM states the 805 has Mundorf N-Cap capacitors and an ALPS potentiometer. I know the 508IA uses Nichicon caps. The Mundorf stuff is well regarded. Whether there's a detectable change in sound and if it's a positive change I guess would need to be directly compared to confirm.
For interstage coupling, 508IA uses I think a rebranded Multicap. which is not as good as Mundorf NCap for that position. As for the Nichicon electrolytics, Mundorf does have equivalent, but from a photo that someone posted of their 805IA, unfortunately in low res, there is not change to the Nichicons. Even the coupling caps, doesn't look like they have been upgraded either. @Ontheone , would be nice to have some higher res photos... *hint* *hint*
Ha! I'm actually truly curious but I'm just not quite motivated enough to manhandle that beast of amp and take the bottom off yet. I might though sooner rather than later!
Technically, having the word "capacitors" means they could get away with stating this by simply having 2 Mundorfs. It wouldn't surprise me if it's more like a 508IA 1.1 as opposed to 2.0 as LM is making it seem. It's not that it's all that heavy but the weight isn't distributed evenly, making it much more difficult and awkward to move. It would be a 10-min process to do so and suggest you use the opportunity the next time you need to move it or unplug all its wires to use a screwdriver and produce some high-quality pics.
The peer pressure is killing me! Agreed, I will take pics the next time I have a decent opportunity. Hopefully my iPhone can take adequate ones.
Continuing my 508IA internal upgrade. Check my previous post on upgrading the reservoir cap for the 6SL7. I continue down/up the path to upgrade the rest of the power capacitors. Down meaning down the signal path, 6SN7/300B/805. Up meaning where the power is sourced from. 2. 6SN7/300B power capacitor -> Vishay/BC 680uF 450V + Mundorf 22uF Aluminum Oil as bypass Back in December I upgraded the problematic reservoir cap that has been blowing up in other ppl's amp from a generic 470uF Nichicon to a 680uF Mundorf. I dug through more catalogs and datasheet and I found out there is a Vishay/BC 680uF that has 50% more ripple current and it was pretty cheap so I guess why not. On top of that, I added a 22uF Mundorf Aluminium Oil cap to bypass. The combo itself increased both the clarity, sound stage depth remains but with better instrument separation and speed, more notable in the firmer bass. The Mundorf is pretty huge though. I was worried that I won't be able to close the bottom lid but I managed to persuade it. 3. 805/main power capacitor -> Wurth 120uF 450V The last step is to upgrade the capacitor for the 805. There are 2 sets of capacitors, one before and after a choke. The main ones are 3x 1200uF capacitor which i think are made by Rubycon and there are no other manufacturer who make a cap of that form factor, so there is no touching those. However, there are 4x 100uF 450V which has plenty of space to upgrade. I opted for 4x Wurth 120uF 450V which not only fit nicely and looks great in bright red, it boosted the ripple current by another 50% margin. Lastly, replaced the rectifier diode with some superfast noise free Schottky. This set of changes are in the very early stage of power regulation, I didn't expect it'd affect the sound but little I knew. Mainly it firmed up the bass, and give an extra omph on loud bass passages. Deeper and faster bass. With the above changes, there is marginally better improvement. Even a friend who visit regularly also noticed it. I have been sitting here for a few hours really enjoying the improved sound. Symphony, no matter how loud and complex, has better sound stage and clarity, when the bass drum and tympani hits it is fast and dynamic. Very enjoyable indeed.
Another improvement is it improves the headroom of the power supply. Previously when I played this album by Aida Garifullina, it would clip due to supply rail dropping. Now after the power supply upgrade it boosted the headroom so it rarely clips anymore. The same adds extra reserve really improve bass impact. Now I can only wonder what it would do to increase the capacitor from 120uF to 150uF!
@jmpsmash So I just opened up the bottom of my 805ia and took some photos. Let me know if you can tell which parts have been upgraded from the 508ia. Also, the reason I opened it is because I've noticed a tiny amount of mechanical transformer hum right when I turn it on but it seems to go away almost entirely when it warms up. Is this normal as parts expands with the heat? I was contemplating tightening down the transformer bolts just to make sure nothing is loose. They appear to be on the bolts with the allen heads. Could I shock myself accidentally by tightening a bolt? Obviously the amp is unplugged but I know capacitors can hold a charge, especially the ones associated with the power supply. I just don't want to do something stupid. I'm no electrician!
@Ontheone thanks for doing that! one request if I may - can you re-upload the original image files? your original images on postimage only have a resolution of 640 x 480, and it's likely the file was (auto) sized on it's way up. its hard to drill down into the photo as this resolution. i assume you took with a phone or something? it's likely that the original has a resolution of at least 1920 x 1080 or much higher.
@Ontheone , there are discharge resistors on the caps. It's does take a while to discharge. I know 10mins it will be down to maybe ~40v, won't kill you but will make a spark if shorted with screwdriver. On the conservative side, give it one hour after turning off the amp before touching stuff. Thanks for the pics! So far as I can tell from the photos, there are only very small difference between 508IA and 805IA. The coupling Multicap are the same, though no longer LM branded. The power supply capacitors are also the same. There are a couple of small green cap near the large hi voltage capacitor, probably for noise filtering. The most significant, but not to do with the sound, is the extra circuit board below the power supply transformer. The blue box should be a relay which is to control the turning on of some circuit, probably the one that causes the capacitor to blow up over time. I don't see any Mundorf caps in there. The circuit topology and component values look exactly the same. Would be lovely to see some higher resolution photos.
Yes, took with an iPhone. I will try to upload the larger photo into higher res and larger scale and if you need anything else let me know. After waiting an hour I did try to tighten a few bolts that were easily accessible and not too close to large caps. They are were all secured extremely tightly so I don't think I have loose transformer mounts. Bottom is back on and I'm back to listening to great music.
My guess is that with the power supply flaw in the 508IA, LM has been getting complaints. So they added the timing circuit to fix it. They also tidied up the way the components are placed on the terminal strip, but looks like no change in the circuit topology. And in order to differentiate, they made a small change in the model number.