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New Line Magnetic 508ia Integrated Amp

Discussion in 'Audio Hardware' started by GoldprintAudio, May 20, 2016.

  1. Chris Amott

    Chris Amott Forum Resident

    Location:
    PNW
    So I tried this for giggles a few weeks ago. I wondered what would happen if I used Roon's digital volume control, which in theory is pretty good because it uses 64 bits for DSP processing, and went directly in the LM805 pre-in via my Lampizator DAC, which is set to a pretty standard 2V output. Way too quiet as expected. I then tried going into a regular input with the volume maxed and while I had enough gain, there was simply WAY too much noise coming from my DAC. This surprised me somewhat at first. It does seem like Lampizator tube DAC's produce a fair bit of noise when their output circuit is not 'muted' and nothing is playing. Regardless, combined with the LM input sensitivity of 300mv on the regular inputs (and 1000mv on the pre-in) there isn't much room for a clean signal. So aside from my newfound concerns about the SNR of my Lampi DAC, I don't really understand why LM (or any integrated amp) would design such low input sensitivities. Wouldn't it make sense to design an input with 2V sensitivity to match most source outputs and so the volume pot's full range could be utilized in a standard use case?? If anyone could offer insight it would be much appreciated!

    As it stands, I have useable range on my LM805 pot of between 8pm and 11pm. 9pm is casual listening, 10pm starts rocking, and 11pm is too much most of the time. And this is with 6db digital attenuation for some minimal DSP/PEQ processing I am doing in Roon. Without the headroom adjustment in Roon, I think my useable range is only up to 10pm. Is the pot attenuation linear? With a standard 2V source and a 300mv input, maybe it's reasonable to only expect max volume at 10 or 11 pm? (Note that when I performed above tests I did disable digital attenuation).

    So now I had this brief idea that I should try some Rothwell or Harrison RCA attenuators. I don't have issues controlling the volume per se, but wonder if the sound quality would improve if the pot was being used between say 10pm and 3pm instead of 8pm and 11pm ..? Or maybe any gains there would be offset by the RCA attenuators degrading the signal (apparently at the frequency extremes?).
     
  2. jmpsmash

    jmpsmash Forum Resident

    Location:
    Santa Clara, CA
    Which Lampizator do you have? does it have output transformer stage?

    I haven't tried it, but instead of a 6SL7, plug in a 6SN7 in the middle socket, that should lower the gain. Not sure how the operating point will be, but might work.
     
  3. Chris Amott

    Chris Amott Forum Resident

    Location:
    PNW
    Amber 3. It does not have an output transformer stage (didn't know any/many DACs used them) ... why???
     
  4. AP1

    AP1 Forum Resident

    Location:
    TX
    Technically there is no need to match 300B or 805 tubes. But if they are two far apart, it means that one of them can be running out of useful life.

    What is really important in this amplifier - how closely matched a pair of triodes inside each 6SN7 tube. In circuit they are connected in parallel and any significant mismatch will cause issues.
     
    IGD Positive likes this.
  5. AP1

    AP1 Forum Resident

    Location:
    TX
    LM805 does not have a separate inputs for line and pre-amplifier. What it does have - attenuator that reduces input signal when you use pre-amp input. This is fully equivalent to having regular input and volume pot set to approximately 1/3. You can try to use line input and reduced volume to match signal from your DAC and do not touch it after that.
     
  6. Pedro Guillemain

    Pedro Guillemain Well-Known Member

    Location:
    Argentina
    Hi guys
    I'm thinking about rolling some 300B tubes on my LM-508 and my budget is around $250 to $350 for a pair.

    Today I have the Golden Lions 300B and I prefered them over the Shuguang WE-300B Replica I also have as I find the latest more refined, but a little thin sounding compared to the GL.

    Eventhough GL 300B are very well rewarded among audiophiles for their price point, I was thinking about trying some other similar priced 300B valves. The thing is that there are "too many" options (JJ, Psvane Cossor, T-II, UK Sound, Shuguang Black Treasure, etc) and so little information and reviews on Internet that I would like to know if anyone of you have tried a "very" good 300B on this price range ($250 to $350 for a pair).

    I know some will recomend KR, ACMEs, EML, etc, but they cost two to three times more and they are out of my budget for now.
     
  7. Jay805

    Jay805 Member

    Location:
    20774
    Thank You
     
  8. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    The idea of matching is that typically, for a pair, there will be a single bias point. Since there is a bias point per 805 tube, they don't need to be matched at all.
     
    IGD Positive likes this.
  9. IGD Positive

    IGD Positive Forum Resident

    Location:
    Inner groove
    That's what I thought. I know very little about tube measurements (I'm learning though!) so I figured I would ask here. Given the measurements I gave in my post, do you think those would be too far apart? I just don't know what the typical range is for that Vg value.
     
  10. Jay805

    Jay805 Member

    Location:
    20774
    I have zero experience. I have not replaced the stock 300bs. One thing to note when making a choice is the 300bs is that they can last a long long time like 40,000 hours. Given that they last so long I’m thinking about the 300b as more or less permanent. So I’m going to splurge a little.

    Im looking forward to your results. I think their may be some group think in this thread around tubes. Not that the the folks have not found great combos. Just that there are probably great tubes that have not been mentioned that are not being explored. The options, particularly for 300Bs, are endless.

    I’m looking for EML 300B-xLS but I haven’t found a good deal on any yet. But if i find a Sophia Royal Princess, Western Electric, Audio Note, Psvane Acme, TJ Fullmusic Q, EAT, Takatsuki for $300-400 I will buy it and take the risk that it’s not as good or durable as the EML.
     
    IGD Positive likes this.
  11. Jay805

    Jay805 Member

    Location:
    20774
    Pedro,

    Got my VT-99 adapter. With 0 hours on them and already much, much better than stock tubes. So far biggest change for the better. Thanks
     
    Pedro Guillemain likes this.
  12. Devg

    Devg New Member

    Location:
    US
  13. Jay805

    Jay805 Member

    Location:
    20774

    What about this New TJ Fullmusic Vacuum Tube 300B/n Mesh Plate Replace 300B Vintage HIFI AMP DIY | eBay

    300B Shootout! by Thorsten Loesch
     
    Pedro Guillemain likes this.
  14. AP1

    AP1 Forum Resident

    Location:
    TX
    I have a pair of Sofia Princess with meshed plates. I tried them in this amplifier and also in another amplifier where they serve the same function - zero gain driver for final tube. They simply are not good fit for that role.
     
  15. AP1

    AP1 Forum Resident

    Location:
    TX
    AS-125 uses 211 tubes without grid current. LM-508/805 uses 805 tube with high grid current. These are two very different circuits. Unlike 508/805 AS-125 does not need much feedback to operate efficiently. But as a result AS-125 has less than 50% of useful power in comparison. It will be more like LM-518. If your speakers are efficient and easy to drive, I would recommend AS-125 more.
     
    jmpsmash likes this.
  16. Devg

    Devg New Member

    Location:
    US
    Thanks!

    My LM 805IA is too much power for single driver Cube Nenuphar. The speakers are often demoed with 2A3/300B amps but I am not sure if that low power is a good fit for a room which has a open configuration. The other solid state amp I use is First Watt SIT3 which is about 18watts @ 8Ohms. This particular speaker due to its design likes zero to low negative feedback and low DF which is also in favor of AS-125. So in paper, the AS-125 is a much better fit. The 805IA seems a very detailed amps with excellent top to bottom extension (off coarse with the right tubes) - I was wondering how do the AS-125 sounds in comparison.
     
  17. Jay805

    Jay805 Member

    Location:
    20774
    AP1,

    Thanks for saving me a waste of money. I’m glad I didn’t win my bid on those sophias. What is your recommendation for the 300b? I have RCA 805s. Thanks
     
  18. Ontheone

    Ontheone Poorly Understood Member

    Location:
    Indianapolis
    I'm using a pair of EML 300B-XLS's with my RCA 805's. I like the sound and it's an improvement over the stock 300B's. With that said, I haven't tried any other 300B tubes in my LM805.
     
    Jay805 likes this.
  19. AP1

    AP1 Forum Resident

    Location:
    TX
    For me plain Shuguang 300B-98 is perfectly good in that role.
     
    Pedro Guillemain likes this.
  20. Billion$Baby

    Billion$Baby Forum Resident

    Might want to try SIT-1's or Vinnie Rossi L2ISE on those Nenuphar's. Suppose to be a MUCH better match with the Nenuphars than SIT-3. I have a pair of Custom Blue Nenuphar Minis coming later this month. Go on AUDIOGON to visit the Very long Nenuphar Thread which is full of helpful nuggets
     
  21. Devg

    Devg New Member

    Location:
    US
    Yeah, I know, I know of the Agon thread as I participate, though seldom. The SIT-1 is an unobtonium. The L2ISE is out of my price range at the moment. I tried the Valvet 2Se but preferred the SIT3. The new F8 also seems an option. Would love to try the Bakoon 13R on the solid state side and some 300b PSET on the tube side.
     
  22. Billion$Baby

    Billion$Baby Forum Resident

    Valvet2 Just had another upgrade....now 4450 with upgraded parts. Also interested in Bakoon but cant get the usual 20% discount so its off my list for now.
     
  23. Jay805

    Jay805 Member

    Location:
    20774
    AP1,

    Those are the stock tubes? Thanks for the response.
     
  24. Devg

    Devg New Member

    Location:
    US
    Ahh..I didn't know they have E3 now. I auditioned the E2SE and in my system the SIT3 was fuller sounding than the E2SE. Need to find a way to audition the E3 now :)
     
  25. Pedro Guillemain

    Pedro Guillemain Well-Known Member

    Location:
    Argentina
    You are welcome. Yes, the Sylvania VT-99 are very good tubes for the money and they will smooth out with more hours.

    How would you describe the differences in SQ?
     

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