Fun. I would be interested in seeing a schematic of the 805 and if it has any differences to the 508.
It definitely has some differences but the question is whether they're major ones. From what I've read, the 805 is superior as it has a dedicated pre-out which means the preamp tubes in the 805 aren't used when using a dedicated preamp. That's the biggest difference I'm aware of although LM has specified the wiring and some caps in the 805 are supposedly of superior audiophile quality than with the 508.
Yes for example did they change that capacitor that blew up on a few people? Where is that located on the schematic?
It's the one immediately under the (when facing the amp) right transformer. No idea if it was changed. One member said he'd look in his 805IA but never got around to it.
Lansche Audio Lansche Plasma 4.1 | Full-Range | Covina, California 91724 | Audiogon This looks exactly same as mine,although I do not have mine on sale. The speaker is a real beauty (nice WAF) and work well with Line Magnetic 508 or 805 even in good size listening room due to high efficiency (99db/w). If you have LM 508 and 805 and spare 17,500$, you can enjoy spooky vocal out of it due to plasma tweeter. It also give excellent dynamics due to two active 10 inch woofers.
Can someone explain the purpose of the single 6SL7 vs the pair of 6SN7's in the input/preamp stage? It looks like the 6SL7 is some sort of input buffer maybe and the 6SN7 are input drivers/gain? If so, does each triode in the 6SL7 buffer each channel separately ... ? Aside from an interest in understanding how my amp works at a low level, I am also trying to determine how important it is that the single 6SL7 be internally balanced. Similarly, how important is it that the 6SN7's be matched (which is not the same as a balanced dual triode). thx
If someone had some answers to Chris' questions I would be very happy, because I have had my 508ia for a year now and just started rolling tubes in the preamp section (some Melz 6n8s and 6n9s and TJ Full Music 6sn7 thus far). I am very interested in learning about the functions of the 6sn7 and 6sl7 positions and how they divide the workload. Between the tubes and within the double triodes. I also would like to thank all you experts here for the extremely valuable facts you have contributed to this forum.Reading all 64 pages has helped me enjoying my 508ia even more.Thank you guys!
The signal path goes through all the tubes. Each stage amplifies the signal so nothing is just a pure buffer. The 6SL7 has 2 sections inside, the L/R channel each take one section. The 6SL7 drives the 6SN7. Each L/R channel uses one 6SN7. 6SN7 also has 2 section, they are wired in parallel. The 6SN7 drives the 300B. 300B is difficult to drive properly so perhaps that's why it takes 2 6SN7 sections. Each L/R channel uses one 300B. 300B drives the 805 tube in class A2. Which means 300B also contributes to the current driving the output. So while ppl say 300B is not important, IMHO it is still important and it is not just for show. The signal passes through each tube one by one, each stage amplifies the signal a little in order to provide enough voltage to the output transformer. So each tube has gain and contribution. It is hard to say which tube will affect the sound the most. Leave that to your own experiment and your ears. IMHO, it is important for each section of the 6SL7 to be matched well, and also for the 6SN7 to be a well matched pair. Similarly for the 300B and 805.
I've been reading this thread with great interest. I have a brand new 805ia arriving next week to share time with my Pass XA30.8 driving a pair of DeVore O/96's. I've been itching to get these monkeys connected to a SET amp with a little grunt to it. I'm planning to use it as a power amp and continue running my sources through my VAC line stage. Are most owners using their 508/805 as an integrated or power amp? And are sonic improvements often noted when using as a power amp or is the preamp section exceptionally strong? I realize it's easy enough for me to A/B both ways and listen for myself.
I got started using tube amps when I bought a used pair of Rogue KT88 monoblocks. I already had a Peachtree iNova integrated that I had been using as the main preamp/amp. Later I bypassed the iNova's power amp stage, when I picked up a separate Emotiva power amp. These I used for the main SS system. I then added the monoblocks to use with the Altec Lansing A7 theater speakers, still using the preamp output with a splitter for the monoblocks. Later I picked up a separate tube preamp from a division of Cary Audio. I switched to the line output of the iNova, which still served as my system source selector and DAC, before the monoblocks. Over a period of time, I tried a dozen tube amps. All of which went through the tube preamp first. But all of them were not straight power amps and some were intergrated amps, new and vintage and one was a Fisher 500C vintage receiver. I bought a LM 528iA integrated, which is their 22-Watt 845 tube amp. I ran it though the power amp input, having a separate preamp already in place. It was fantastic! Later, out of curiousity, I switched the input leads to the preamp input and turned the source selector to that input. My take was that while running through the LM preamp input, the sound was nowhere as nice as when I used it as a straight power amp. When I switched it back to the power amp input, the sound quality greatly improved. My takeaway from this is thst LM wisely spent the most of the cost of the integrated on the power amp section. This would be because, many users would already have or would be using a separate preamp. If you look at the preamp section of the LM, you will see that it is pretty basic, not necessarily bad, just basic. My external preamp weighs about 22 lbs. and is a lot better. Since I have run the other integrateds and the receiver through their preamp sections and they sounded fine, I was not expecting to hear much, if any, of a difference with the LM either way. I also didn't really care, since I did expect it to sound the same. But, I definitely feel that it sounded better with the preamp bypass.
Thank you jmpsmash for your precise explanation. It helps greatly understanding the working of my beloved 508ia!
Very helpful summary of your process and conclusions! I will report back once I receive the LM. I would find it hard to believe that the LM preamp section could compete with the $10K retail VAC (especially considering it has an incredible outboard power supply, transformer coupled outputs, and Lundahl transformers) but hey, crazier things have happened in the world of sonic synergy.
That is the point. I went into a detailed explanition because I had been informed by others in this forum that in the power amp mode, the LM preamp section is still active and it only by passes the volume control. I don't agree with this assessment as running it as a straight power amp with the external preamp made a big difference. If it didn't, I would be fine running it either way. LM makes their own preamp and it is in the neighborhood of $6K. Why would they bother to do this when the 518iA was a $4,500 integrated? But the difference goes from good to astonishing with the external preamp. The Cary is a very straightforward and simple preamp with only two 6SN7 tubes. The beauty of the 528iA is that with the right high sensitivity speakers and upstream components, it really is an end game world class power amp. Here the built in preamp section is really the limiting factor. My preamp is no where on the level of the VAC, but it does have a huge power transformer and two huge output transformers. While it is no where near the 77 pound weight of the LM 518iA, the power supply and transformers are far larger than I would think that they would ever need to be. I can understand a large power supply transformer and large output transformer for a power amplifier but it wouldn't seem that the same rules would apply for a device that only has to produce an output of 1.5 Volts? I am retired now, but I put together a tour of my former audio room directly after my equipment listing. It is complete with photos and descriptions. Check it out if you like, you may find it to be of some interest.
I actually asked my LM dealer this question before I purchased the 805 this week. He confirmed that while the LM preamp tubes remain on , that when switched to "preamp in" the preamp section is indeed completely bypassed, so you are exactly correctly. Others on the forum were wrong. They must have thought because they saw the tubes still glowing that the preamp section was still active. I would never have bought the amp if this were the case.
It would benefit us all to clear up this confusion once and for all. I have used my LM 508ia solely as an amp for the majority of the time I've owned it. What I came to realize was that both the 6SN7 and 6SL7 were as influential to the sound as when I used the unit as an integrated amp. So, we can all at least agree that they are still in the signal path and influencing the sonic end result. Also, the preamp tubes still affect the gain of the unit. I should know since I dealt with overall system gain issues that caused the sound to distort depending on the tubes I used in my DAC. Different 6SL7s were especially noticeable in shifting gain. I plan on modding my LM 508ia, and I believe the tech working on it will be able to provide clarity once he opens things up. Now I just need to find the time and commitment to give up the amp for a significant period.
Hopefully I'm not coming across as argumentative, but this has been discussed quite a few times in this thread....... What you posted is incorrect......The preamp section IS still in the signal of the 805 (and 508). The volume control and input selector are the ONLY things bypassed. The 219ia and 845Premium are the only integrated units in the Line Magnetic family at this time that have true, full preamp bypasses.
The funny thing is that some on this thread have stated that the 508 sounds much better with a dedicated pre-amp in front of it, while others have stated little difference with a pre-amp in front of the 805. Given all of the contradictory anecdotal evidence, there is likely a lot of expectation bias going on here. Seems like the pre-amp input is really just best suited for: a) sources (DAC's) with their own volume control. b) possibly a higher quality passive volume control than the built-in pots control. Adding a full pre-amp in front of the 508/805 to make it sound "better" is probably more a matter of preferential coloration being added.
Interesting and I trust that you're correct. I suppose I will simply try it both ways with my gear and see how it sounds. This makes me hope the LM onboard preamp section is pretty darn good! Fingers crossed. @GoldprintAudio Let me ask...my linestage has 12 dB of gain. Will that gain get passed onto the 805ia when using the bypass inputs?
On the preamp bypass, the volume level of the 805 does not adjust the sound levels....whatever your line stage is passing will come through as is.
My apologies for the late reply. I am not sure what you are refering to. I have replaced the cap as well as adding the protection diode. Things has been working since then without any issues. You can find more info on the other thread: Design flaw for Line Magnetic's LM-508IA.
It's been a while since I've used/seen a 210. But with the switch setup like it is, it's very possible that it also is a full bypass. It's setup similar to the 219.
