The "Pre In" feature on the LM 508ia bypasses only the volume control but not the preamp stage. Even with an external active preamp or an external passive preamp (an auto-former- or transformer-based volume control, for instance) attached, the 6SN7 tubes as well as the 6SL7 input tube are still in the circuit. I found this out by communicating directly with Line Magnetic. So using the "Pre In" does not transform this integrated into a power amp. Both of the unit's gain stages remain intact.
Well, a couple of things here, I have heard comments along those lines. But it still does mean that the 508 can be used as a HT bypass. I have the 518. I did replace a pair of 12AX7's with NOS RCA black plates from the late 50's, because of what you mention. I have four systems in the room, all connected to a single SS integrated amplifier that has a DAC, with both digital and analog inputs. It is used as an input source selector, DAC and class "A" preamp. I do not use the built-in amplifier, perferring to use four separate outboard power amplifier's. There is on PrimaLuna amp on a front pair of Zu's. The other two systems are SS. And the last one, which powers a pair of vintage, restored and modified, Altec Lansing A7, Voice of the Theater speakers. This system has a SS back-up amplifier, but is powered by any of the many different tube amplifier's that I have. Several are straight power amplifier's but others do have a built-in preamp stage. All system sources lead directly into the SS integrated, that acts as the input source selector. The from the line level output of that unit, it feeds into a separate tube preamp, which is always in the circuit that runs the A7's. I can use a separate input on the tube preamp to bring the turntables directly into the tube preamp, bypassing the main source control, if I want to run the turntables into the A7's. At any rate, the tube preamp is always in the A7 circuit. Sometimes, I may have a tube integrated preamp that I have driving the A7's, so, in this case, there is always the main tube preamp feeding into that integrated. They have always sounded fine, no complaints. But, most of the time, the tube preamp is feeding into a straight power amplifier. Before I acquired the 518, I bought a LM 211iA integrated and ran it with the external tube preamp, no issues. From the beginning, I ran the 518 from the tube preamp to the line level power amp input, which I felt sounded excellent. One day, I decided to switch to one of the other inputs to see what effect it had. I switched the input cables and selected one of the preamp inputs. I played with the volume control and I did not feel that the sound was the same at all. I was expecting it to have little effect, other than being able to control the volume level on the 518 also. I was not satisfied, with the sound and I moved the inputs back to use the 518 as a straight power amp and I feel that it does sound both different and better this way, using the external tube preamp and not the preamp in the 511 also. I don't know what is going on inside the 518, but I will only run it now as a power amplifier.
It definitely makes sense to me that the 518ia would sound better in your set up with your active preamp attached to "Pre In" and not one of the other inputs since using one of those normal source inputs and not the "Pre In" feature means that the signal of your sources is passing through at least two separate volume controls (I'm not sure how the preamp stage of your SS amp factors in to this). And standard signal attenuators can certainly degrade the quality of a source. I'm assuming you've also been able to a/b using your external tube preamp in "Pre In" vs. attaching your source directly to the 518ia (that is, bypassing both your SS amp used as a source selector and your tube pre). What's most important, of course, is using what sounds best to your ears.
Which ones? Couldn't one simply use a converter like this instead? Which one? Your profile isn't filled.
The OP's question relates to how he'd like to get the best of both worlds ; using a 3.1 (2 mains, a center, and sub) setup for movies and just having the 2 mains active when listening to music.
I have a Peachtree iNova which is my source selector switch and the central point of control for the system. Other than the two analog inputs on it, one from the phono-pre selector output (two TT's in system) and the analog input from the processor, the other inputs are digital and go through the internal ESS Saber DAC in the iNova and it's class "A" SS preamp stage. The Polk LSiM707's are powered from the iNova, through an External 250-Watt Emotiva EPA-2 (gen. one), the SS rear amp and subs get the same signal from the preamp of the iNova. The signal from the phono preamp is split, so that it can go into the iNova, for the front and rear system. This is the tube preamp which stays in and I never remove it from the system. It is the preamp that is used to power the tube integrated or power amp that drives the vintage Altec Lansing A7's. There is a line level output from the iNova that bypasses the volume control, which runs into this tube preamp, so that digital sources can be played through the tube system that powers the A7's. I use a 2nd input on the tube preamp as a direct input for the phono stages. Any integrated or power amp is placed after this tube preamp in the circuit. This tube stage, provides tube richness to either a digital signal that has been converted to analog or of a SS or tube phono preamp. The SS preamp is necessary to play digitally sourced music so it stays in the system at all all times, as does the tube preamp. THe 518 plays beautiful with the external tube preamp in its usual place, when used as a power amplifier. When used as an integrated, no so much.
That is what I do, except I have a 5.1 system, with rear speakers. I can leave the sub on or take it off for either movies or stereo. My front mains are the same ones that I would use if I had either a HT or a stereo set up. So of course, I use them for both, as the OP should be doing as well. THe center channel is only put into play when in HT mode.
It would be helpful to the OP if you could name the preamp you're using to give him an idea of what he should be on the lookout for. He has an Anthem AVR. Not sure if it could be used as a preamp and no idea whether it would sound better or worse than using the 805IA as an integrated.
I believe that you might have this thread, which was an announcement by the OP about the introduction of the new 508iA and this current thread. Help with first integ. amp - Primaluna v. Rogue v. Line Magnetic v. McIntosh v. Naim My preamp is very uncommon and almost impossible to find. Before Cary audio decided to go to an Internet Direct marketing company, the decided to open up an Internet Direct separate division. So they could have an iron in the fire. They named that division Audio Electronic's and introduced two quality products in keeping with the Cary Audio reputation. They offered a power amp called the Hurcules for $1,895 and a preamp, the Constellation for, $1,500. Both are tube units. Both products were very well designed to have high quality parts but be very basic in design, the Constellation preamp has two 6SN7 tubes three line level source inputs and a motorized volume control with remote volume control and mute function. They do not even offer a tube cage as an option. Both of these products were discontinued soon after they were announced and the Audio Electronics division appears to have gone away and Cart itself is now Internet Direct, though they do retain a dealer network. Here is a link to their 2012 product announcement in TheAbsoluteSound back in 2012. (Note, this product is not to be confused with Constellation Audio, which is a company). However, there is one that is newly listed on Audiogon, just on October 7th. Cary Audio Electronics Constellation Preamplifier This would be a great find to grab. There were very few of these units made and they are the best new manufacture tube preamp that is offered at a $1,500 price point. Here is a review for both the Constellation and the Hurcules from Positive Feedback. This just happens to be the preamp that I own and use. Many already have their own separate preamps or maybe, like me, they have a unit like a Peachtree integrated that has both a DAC and analog imputs and happens to have a nice sounding SS class "A" amplifier and headphone amplifier. Even if they do not have a tube preamp, andy good preamp might work better than the one in the 518. I could take the preamp out of the iNova and route it directly into the preamp-in channel of the 518. Before I acquired the Constellation, I used the preamp output of the SS iNova to drive my Rogue M-120 monoblock's (which have since been replaced by a pair of M-150's). I would rather drive a tube power amp with a SS preamp, than the other way around, though others disagree with my position. In the other thread, I have already advised the OP how he can set up his Anthem for both stereo and HT. He could use the Anthem as a preamp to drive the 508 in either the line input mode or the preamp mode. I suggest that he try this both ways to see if he thinks that either way would work for him. Since he already has the gear, it costs nothing to try this. I think that the Anthem might prove to be a fine SS preamp, as they make really excellent quality gear. You never know, unless you try.
Strat - Im using a mixture of Blue cactus & Miflex both picked up in Akihabara, Tokyo. Awesome little dingy audio perv market. I don't have any pics to hand as i am away with work for several weeks, i do have this pic though it is before i fitted the 2c22's in, i can take more pics when I'm back if it interests anyone? I also changed the cathode bypass caps, to Audio Note Kaisei & Nich Muse, i played around with their uf value to see what different bass frequencies i could get but ultimately decided the original values were best. I also changed all manner of resistors around the amp, in amp stage, PS etc, all to good affect. TKD, Takman, AMTRAM, Mills. Aldo a few other bits that have escaped me. https://i.imgur.com/J9MEBKH.jpg You certainly could use the adapter and it will likely sound better than a 6SN7, however i always run my pre amp into the amp and decided it had too much gain, if you use one 2c22 then, in reality, gain is less than 1/2 a 6SN7. Also if it is implemented correctly with a CCS board it will behave and perform far better, not to mention look cooler & tidier. The pre I'm using is a totally rebuilt and modded Supratek Chardonnay, too many mods to mention just check the pics, its a force of nature and is the best pre i have owned or had in any system its been in. I did however find an annoying ground loud hum when putting the pre into the 508ia, i tried all manner of traumas to remove it, resoldering most joints, lifting ground system etc but eventually took the plunge on a Jensen isolating transformer between the pre and amp, it worked superbly, greta bit of kit. Although the fiend in me has seen some capacitors & resistors inside the Jensen & will no doubt cave in to upgrading them too, probably with naked Vishays & Jupiter Coppers. The disease is real, however so are the benefits, usually, probably hahahah https://i.imgur.com/U433uIK.jpg Just for info, the pre in still keeps the pre stage tubes in the circuit & bypasses the volume however i believe the pre in operates at a much higher input sensitivity of around 1000mv apposed to the regular rca in's of around 300mv. I actually use the regular because the difference in sound is so minimal but the convenience of the LM controller is wiked, all be it at annoyingly loud intervals (due to the sensitivity) Keep enjoying the music peoples : ) J
Strat - Im using a mixture of Blue cactus & Miflex both picked up in Akihabara, Tokyo. Awesome little dingy audio perv market. I don't have any pics to hand as i am away with work for several weeks, i do have this pic though it is before i fitted the 2c22's in, i can take more pics when I'm back if it interests anyone? I also changed the cathode bypass caps, to Audio Note Kaisei & Nich Muse, i played around with their uf value to see what different bass frequencies i could get but ultimately decided the original values were best. I also changed all manner of resistors around the amp, in amp stage, PS etc, all to good affect. TKD, Takman, AMTRAM, Mills. Aldo a few other bits that have escaped me. https://i.imgur.com/J9MEBKH.jpg You certainly could use the adapter and it will likely sound better than a 6SN7, however i always run my pre amp into the amp and decided it had too much gain, if you use one 2c22 then, in reality, gain is less than 1/2 a 6SN7. Also if it is implemented correctly with a CCS board it will behave and perform far better, not to mention look cooler & tidier. The pre I'm using is a totally rebuilt and modded Supratek Chardonnay, too many mods to mention just check the pics, its a force of nature and is the best pre i have owned or had in any system its been in. I did however find an annoying ground loud hum when putting the pre into the 508ia, i tried all manner of traumas to remove it, resoldering most joints, lifting ground system etc but eventually took the plunge on a Jensen isolating transformer between the pre and amp, it worked superbly, greta bit of kit. Although the fiend in me has seen some capacitors & resistors inside the Jensen & will no doubt cave in to upgrading them too, probably with naked Vishays & Jupiter Coppers. The disease is real, however so are the benefits, usually, probably hahahah https://i.imgur.com/U433uIK.jpg Just for info, the pre in still keeps the pre stage tubes in the circuit & bypasses the volume however i believe the pre in operates at a much higher input sensitivity of around 1000mv apposed to the regular rca in's of around 300mv. I actually use the regular because the difference in sound is so minimal but the convenience of the LM controller is wiked, all be it at annoyingly loud intervals (due to the sensitivity) Keep enjoying the music peoples : ) J
Hello Shertzy, and thank you for posting all of this fascinating information! I'd love to see more pictures of your full 508ia mods (especially with the 2C22s!) when you get back from your travels. It looks like you've really transformed that Supratek into something very special! I also think the 508ia may have too much gain for use with most sources, and especially if you want to use an active preamp with it, and so I'm curious about your swapping out of the 6SN7s for the 2C22s. The amp's NFB settings, according to LM, offer differences of -1dB, -3dB, -6dB and -12dB respectively (from setting 1 to setting 4 on the switch). Can you share with us what effect using the 2CSSs with their lower gain has on the different NFB settings? I know that NFB is still at work since it is associated with the 6SL7 input tube. I'm assuming that because the gain structure of the preamp stage has changed so have the differences in NFB. I've had my 508ia modded to bypass the 6SN7 gain stage altogether (and have had those wonderful Jupiter caps installed between the 6SL7 and the 300Bs) so that I can get the most out of a high quality passive preamp. I've very much enjoyed the results!
When you have time, can you check which specific ratings for each you got? It might be interesting to experiment but having a laundry list of all the exact parts needed to duplicate your results would be helpful. That would be fantastic! Definitely interested. Tidier, absolutely. Can you please elaborate on what is meant by behaving and performing better?
Hello I have the LM508 and two days ago I connected to it an Audio-gd Master 1 SS preamp, wich is said to be a very fine preamp, competing with preamps costing much more. The sound has become much more refined, detailed and pure, but it has also become more polite, with less punch and bass attack. Has any owner of the LM508 have had a similar experience with an SS preamp? I was expecting to have more powerful sound, not the opposite.
That is odd for a few reason's. I am not familiar with your SS preamp, but back in 2013 I acquired a pair of Rogue M-120 monoblock's and I used to run them with a SS class "A" preamp and the monoblock's really rocked. I have the 518iA and I always use it with a external Cary, Constellation 6SN7 tube preamp and it rock's too. I can't imagine a SS amp not really rock'in the 508?
Yes. That´s exactly my point. I'm intrigued why is it happening because I've heard that the Audio-GD Master 1 preamp had a lot of gain and it its full class A SS preamp. It sounds much more refined, with more detail and less sibilance/harsh in the uper frecuencies, but it also sounds less powerful. Could it be influenced by the RCA cable that connects the Master 1 to the LM508?
Getting close to making a decision to get the 805ia and it got me thinking about tube rolling potential. It sounds like there are various options available as this thread is super useful (and long). Some have mentioned that the 300b change has the biggest change amongst the other tubes - the Princess ($1,200) and the EML XLS a($852) re both very pricey new. Is the Gold Lion even worth considering over the stock or should I just save up for the former 2? I've taken notes on suggest 6SL7's (namely the Mullard or the less expensive Tung-sol) but what about the 6SN7's?
Just one more thing to add to the 508 thread and all the tube rollers here. Psvane has introduced a new line of tubes: Their "ACME" line of tubes. One of the tubes in this line is the 805 tube. There aren't many options out there for this tube, but here is a high priced, high end option. They also are making a 300b ACME tube. So you may end up wanting to add this to your list of options.
Try Ssl7 first. It has a most effect . I am happy with Brimar True NOS Gain Tested Brimar England CV1985 / 6SL7GT Vacuum Tube Brown Base | eBay I also have ECC35 recommend by other folks here. But it is in my storage. I may try it in 2 weeks to compare it with excellent Brimar. Stock 300B is pretty good. I changed it with Sophia but with just more transparency and details. I recommend you to keep the stock 300b and 805 for a while. It is better to play with SN7 and Sl7 tubes first. They make huge difference from stock tubes.
I've got the biggest upgrade in sound of my LM508 replacing the 6SL7 tube FIRST, second the 6SN7 tubes and in third place the 300B and 805 tubes. 300B and 805 are expensive, so I've only tried a few (and not too expensive) Shuguang WE Replica and Gold Lions in the 300B (I like better the second ones) and Psvane 805, stock vs A-TII (much better the A-TII). The preamp tubes are much cheaper so I've tried a LOT of NOS tubes, not Mullards or Telekunken, but Tungsol, Sylvania, GE, Ken Rad, Raytheon, Shuguang Black Treasure, Westinghouse, National, Hitachi, NEC, etc... And I prefer Tungsol BY FAR. They are a bargain and they sound fantastic. Im not really sure if spending +1000 bucks on a pair of 300B is worthwile. Its up to you, but I dont know if you will be rewarded with a really big step in sound quality against the 250 bucks that a pair of Gold Lion cost. If you spend a big amount of money on a pair of 300B or 805 (for instance TJ Full Music Premium 805), please let us know the result!!! Im anxious to hear your resulta!! Nevertheless, I would start spending less money and changing the preamp tubes for Tungsols!
It could be mismatch of impedance. The output impedance of pre is not low enough for the input impedance of LM 508. But I can not tell for sure. If that is the case you can use transformer but good matching transformer can cost as much as your pre. That is the pitfall of blind shopping without auditioning. But you have little choice in Argentina.
Noted on the SN7 and SL7 tubes. Thanks for the recommendation on the the Brimar 6SL7. I ended up purchasing a ECC35 to start with and will see how I like that sound and go from there. I agree, I think I'll stick with the stock 300b's and the 805 for now. Those are a bit pricey and it doesn't sound like it offers quite the difference in impact versus the preamp tubes? Noted on the Tung-sol. I ended up with a set on order as well. Looking forward to trying those out in the 6SN7 slots.
Just be sure you buy NOS Tungsols. I havent tried the new production ones, so I cant tell you about them. Let us know your results!
I have a LM 518iA. See post for photo. I recently brought out a little Decware Amp and found that I had a defective JJ 6V6GT tube. I replaced the set with new manufacture Tung Sol's. I am sitting here listening to this little 3.9-Watt class "A" single ended pentode, right now. My 518iA is sitting on the shelf. As good as these are, I NEED to investigate some NOS Tung Sol's and maybe some other's as well.
