New Line Magnetic 508ia Integrated Amp

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

  1. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    In guitar amps, biasing hotter removes headroom and allows for easier distortion of the tubes. However, in reality, that translates into a warmer sound. Therefore, if it is biased hotter than normal but the volume isn't turned up to the point where the sound actually begins to distort, in theory, one could benefit from the hotter sound up to that point.

    I could see this as being an easy safe tweak for anybody with highly efficient speakers. For myself with 86db of efficiency, that wouldn't be recommended as the sound would likely start to distort by the time I'd hit the volume level I'm comfortable with.
     
  2. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    I said I was going to post pics of the different Elrog 300B tubes in chronological order so people can differentiate between them. Well, here they are...

    [​IMG]

    [​IMG]

    Please note the # mentioned on top of each tube so you can notice that it goes from 1 to 2, and in the 2nd pic, it shows tube #2 again and then, the latest version.

    Here's a bigger pic of the 3rd and latest version. Notice the black base.

    [​IMG]

    [​IMG]
     
    jkull likes this.
  3. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    Can anybody recommend a trustworthy source to buy red-based RCA 5692 tubes?

    Has anybody tried any of the following tubes?

    - Mullard ECC32 in the 6SN7 slots
    - MELZ 1578/6H8C in the 6SN7 slots
    - Osmar/Marconi B65 in the 6SN7 slots
    - RCA 805 power tubes
     
  4. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    Also wondering whether it matters in any way whether the 6SN7s are a matched pair.
     
  5. JeffC

    JeffC Well-Known Member

    Location:
    Catskill, NY
    Hello J.D.80 and sorry for the delayed response. Yes, I do bias my 508ia at 120. I'd be interested in learning what improvements biasing higher could bring. I wonder also what NFB setting that person you met who set bias at 135 used. The NFB settings provide -1dB.-3 dB, -6 dB and 12 dB of feedback, from 1-4 on the dial.
     
  6. J.D.80

    J.D.80 Forum Resident

    Location:
    New York City
    Rhe g
    The gentleman preferred the NFB on 4 saying it sounded the most natural to him, which I tend to agree with. To help with the softness of the sound on setting 4, I spiked my speakers instead of resting them on felt pads, trying to find the perfect balance. As you know. The more you turn the NFB toward 1, the amp brightened up which isn't always my preference. Spiking the speaker helps focus the sound a bit more.
    So the -1 through -12db (NFB setting 4-1) is in relation to zero being the highest output possible? I didn't quite understand what those numbers are in relation to.
     
  7. Davey

    Davey NP: Electrelane ~ No Shouts No Calls (2007 LP)

    Location:
    SF Bay Area, USA
    Kind of. I don't know the LM amp or the switch settings, but in general, the amount of negative feedback is roughly the open loop gain (no negative feedback loop) divided by the closed loop gain (negative feedback loop applied), expressed as dB. I assume the numbers correspond to how much the open loop gain is reduced by the addition of negative feedback, so the 1dB would be very little feedback (possibly highest distortion), whereas 6 dB would indicate open loop gain has been reduced by half and 12dB would indicate the open loop gain has been reduced by 4 (possibly lowest distortion).
     
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  8. JeffC

    JeffC Well-Known Member

    Location:
    Catskill, NY
    That's very interesting information about using spikes with setting 4. Thanks.

    -1 through -12 dB = NFB settings 1 through 4. Setting 4, which you perceive as most natural, is the setting with the most NFB. Setting 1 has the least NFB. There is no zero because that would be zero NFB. But a good number of SET purists do seem to prefer no NFB whatsoever. The 805 tube, however, needs at least some NFB to be listenable. Seems like for many who use this amp with speakers that aren't particularly sensitive that might be a good thing because with NFB there is an increase in damping factor and that compensates for the relatively high output impedance of these tubes.
     
    Seafinch likes this.
  9. J.D.80

    J.D.80 Forum Resident

    Location:
    New York City
    I'm not sure I grasp yet the correlation between speaker sensitivity and amplifier damping factor. I always thought that damping factor was the relation of the speaker impedance to the amps internal inpedance, so the actual nomial impedance of a speaker was what effected the DF, not the speaker sensitivity rating. My speakers are neither very sensitive nor are they difficult to drive. They have sensitivity of 92db and an 8 ohm nomial impedance. An easy load for most amps to drive. I've actually been thinking of selling trading and paying my way into a used LM219ia which puts out only half the wattage of my 508 since my current speakers are so much easier to drive than my last pair of Dynaudios. But I'm getting off topic here.
    I have much reading to do on NFB and DF now. Especially since I've always believed that what I was hearing was lowest NFB on 4 is in all reality the highest NFB setting. I must say that if this is indeed true, that I LOVE amps with NFB because I never play the 508 below setting 3. I always alternate between settings 3 and 4. Anyway, thanks Jeff and Davey for the responses.
     
  10. JeffC

    JeffC Well-Known Member

    Location:
    Catskill, NY
    I think you are correct to question my assumption of a direct correlation between sensitivity and damping factor. I'm using the term incorrectly and the correlation I'm suggesting is at best indirect. By sensitivity I just meant speakers that are easier to drive for SET amplifiers. And I think you are right about impedance--but I think the actual impedance plot is more significant than the so-called nominal impedance. In other words, knowing the minimal impedance or how low the impedance actually dips is what's crucial. From the reading I've done, some suggest that a dip below 6 or 5 ohms may be problematic for some (mostly lower-powered) SET amplifiers---unless these amps employ some negative feedback, which does improve damping factor. So what I'm talking about here is bass performance. Push-pull amps use negative feedback and have a higher damping factor. SET amps without negative feedback have a high output impedance and therefore low damping factor. Yes, the 508ia sounds brighter (more vibrant, depending, I suspect, on the kinds of speakers in use) when we set the NFB to the lower numbers on the dial. I hear it as literally much more forward sounding at the lower NFB settings. And I'm still trying to find a clear explanation of why this is--of what NFB settings have to do with the midrange and treble presentation on this particular amp. I suspect that this may have something to do with the characteristics of the 805 transmitting tube and with the fact that in order to get the power that the 508ia provides, this amplifier runs in class A2 and not class A. (I'm still not entirely clear about the significance of this point, but according to one source online A2 designates a situation when "the valve output stage grid voltage is being pushed above the 0 volt mark and into a positive grid voltage, causing the grid to draw some current from the preceding driver stage." Maybe there are forum members who could do more to explain A2 for us and what it may (or may not) have to do with the sound of the 508ia.) But one thing I can say with some subjective, experiential certainty is that on my speakers (Tannoy Berkeleys (HPD 385) with bespoke crossovers and an impedance that doesn't dip below 6.9 Ohms) the sound of the low end changes substantially with each NFB dial position. To my ears, the highest NFB settings produce a less pleasurable, less textured bass sound (on settings 4 and 3 the bass sounds drier and more SS like) and I've settled on NFB dial position 2 for my listening.

    Like most of us, I did a lot of reading about this amp and auditioning before I purchased. And I recall distinctly that the the dealer at In Living Stereo, where I bought it, was also convinced that setting 4 on the NFB dial represented the least (or even zero) negative feedback. He too heard it as more organic sounding on setting 4. But from my experiences listening to a friend's excellent LM 218ia (using 845 power tubes)--my first contact with an SET amp-- and from what I'd read about the sonic characteristics associated with SET amplifiers and with the use of variable NFB--especially the obvious point that there is more perceptible gain with the lower settings--I wasn't convinced. Eventually I contacted James at Line Magnetic and he made clear that setting #1 (not #4) represented the lowest amount of negative feedback. I still want to understand more about how NFB, damping factor, class A2 and the 805 tube's curves are related to each other and to the sound of the 508ia...
     
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  11. Davey

    Davey NP: Electrelane ~ No Shouts No Calls (2007 LP)

    Location:
    SF Bay Area, USA
    Doesn't it sound any louder at one end of the NFB settings? Can you switch it with amp active. or do you have to turn the volume down when switching? Or do you have to power off to switch it?
     
  12. JeffC

    JeffC Well-Known Member

    Location:
    Catskill, NY
    Yes, it sounds loudest (most gain) at setting #1 (only -1dB of NFB). Yes, you can switch between NFB settings while the amp is on. And you don't have to turn the volume all the way down when you do so. But when you switch let's say from setting 3 to 2 or 2 to 1 you very obviously notice a marked increase in volume, so it's smart I think to set the volume accordingly before you switch settings.
     
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  13. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    Got an answer about whether Mullard ECC32 tubes would work and the answer is...

    "Filament current for ECC32 is too high. It is not safe to use Mullard ECC82 in 6SN7 slot."

    Glad I asked prior to purchasing these expensive and rare tubes.
     
  14. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    For those still interested in this amp and its capabilities, here's some additional info regarding the tube capabilities of this amp.

    1. The 6SN7 slots can accept 7N7 tubes with the help of an adapter easily purchased on eBay. Here's a picture and link for reference.

    1 × 7N7 7F7 To 6SN7 6SL7 Vacuum Tube Amplifier Convert Socket Adapter | eBay

    [​IMG]

    Why would you do that? Because the equivalent of some expensive NOS 6SN7 tubes might cost *much* less!



    2. Also, 6J5G tubes are compatible to a degree. 6SN7 tubes are dual triode tubes whereas 6J5G tubes have a single triode. Therefore, you'd need two to have the same amount of triodes as a single 6SN7 tube. Aside from that, they are electronically compatible.

    What does this mean? That means that, for instance, instead of buying a pair of the legendary B65 GEC/Osram/Marconi tubes at about 3K/pair (not a typo!), one could buy this adapter, buy 2 sets of matched pairs (for a total of 4 tubes), one pair per 6SN7 slot, and buy the 6J5G equivalent of the B65 which is the L63, a tube which only costs $200/pair! That'd give you the same sound but for $400 instead of $3000. Quite the discount!

    Again, the link and photo for your reference.

    1pc Dual 6J5G 6C5G VT-94 L63 CV1932 VR67 VT154 TO 6SN7GT CV181 B65 tube adapter | eBay

    [​IMG]

    The plane of the adapter can be rotated. Since these devices from China, the eBay seller's command of English left a lot to be desired. He mentioned that it can rotate 90 degrees. No idea if that means it can be rotate up to 90 degrees or just in 90-degree increments.

    Please keep in mind that whether this adapter fits will depend on the tubes and therefore clearance you have. For the record, this adapter's plane measures 85×35 mm. Before contemplating this easy and harmless mod, please be very careful in measuring the amount of room you have between tubes. Assuming it's physically possible to use these without hitting any tubes, the adapters' planes would be at about 40 degrees (diagonally). It won't look nice but would give you the sound you're after without breaking the bank.

    I did find an active member of another message board who owns a few of these adapters so I took the liberty of contacting him to get the last word on how these can be rotated.

    Hopefully, some of you find this info interesting. :)
     
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  15. sandu barbu

    sandu barbu New Member

    Location:
    Romania
    Hello. I sent my lm 508ia back because of that annoying buzz. The dealer said that some loose screws were involved in this noise and now their specialist fixed it. So now you can only hear a very poor buzz that can be heard only if you are sitting with your ear very close to the amplifier so long as you do not burn from the tubes, from about 30 cm. He also told me that the other amplifer 508 he owns has also a slight buzz, which now sounds a bit louder than in the amp I've had.

    The tubes he said were ok. However he will exchange the 300B tubes which were diffrent in shape and had some odd brown deposits. The amp is working fine they said.

    Now I don't know what to do. Any advice?
     
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  16. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    Dont know what to do about what?

    Sounds like everything works. Unless you're asking about whether to take back the repaired and or get a refund and buy something else?
     
  17. sandu barbu

    sandu barbu New Member

    Location:
    Romania
    Yes, my hesitation is about taking back the repaired unit or geting the money back? To see if everything is working as the dealer said, I have to listen it myself in my environment, so to accept the amplif back. My dealer is 500 km away. Probably this is the only way to find out.
     
  18. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    If your dealer heard the issue and now, the issue is fixed and can't be heard, as long as it remains on warranty, I don't see a problem. If the issue or other issues happen, request a refund. Otherwise, you have a great amp you'll be able to enjoy for many years.
     
  19. sandu barbu

    sandu barbu New Member

    Location:
    Romania
    The amp will be on warranty for the next 2 years. As I said I love this amp, so I'll give a try.
     
    Strat-Mangler likes this.
  20. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    Bought a set of lightly used EML 300B-XLS tubes which should be here in a week! Got them for $550 so I think I did pretty good. Can't wait to hear the difference they'll make. :D
     
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  21. Lee Seungwoo

    Lee Seungwoo Active Member

    Location:
    Seoul
    Is there anyone who have tried to roll Premium 805/CNE TJ Fullmusic tube? I'm considering buying them. But I cannot find any review on them.
     
  22. Strat-Mangler

    Strat-Mangler Personal Survival Daily Record-Breaker

    Location:
    Toronto
    Haven't found a review either. There are some 805 NOS RCA tubes that might be interesting to try for cheaper than the TJ FM tubes.

    Otherwise, let us know how the Premium TJ FM tubes are, please! :D
     
    jkull likes this.
  23. J.D.80

    J.D.80 Forum Resident

    Location:
    New York City
    I haven't, but one thing I suspect is that they may be dull emitter tubes- nickel coated dull emitter tubes. If you're into the bright emitter thoriated tungsten tubes, it may not be your cup of tea.
    I am not 100% sure if they are or aren't, so you'll have to read up to find out.
    I say this because I tried a pair of their 805/SE or whatever one was a step or generation below the CNE tube and it was a dull emitter.
     
  24. adamaley

    adamaley Forum Resident

    Wow, this thread has definitely taken off thanks to @Strat-Mangler. What great useful information his quest has brought up. I've been away from here simply because I finally got things to sound as close to perfect as I think is possible, and I have been focusing on cabling and other power supply tweaks for my network streaming source.

    I returned to using the stock Line Magnetic 805 tube - I just couldn't get the Psvane 805-ATs to work with everything else without having to attempt to attenuate its somewhat etched and dry nature. It became even harder to stick with them once I upgraded my USB cable to one that is more linear and not as mellow and colored as what I originally had. Funnily enough, the stock 805s brought a great ease, and more full-bodied sound to the music that caused me to quit with all the tube-chasing shenanigans. It made me remember one member's musing on here in one of the earlier pages of this thread on how great the stock tubes are and that we shouldn't be too quick to give up on them. I'm definitely interested in anyone's take on other off-the-beaten-path 805s like the RCAs. It is worth noting that one of my best listening sessions was when a buddy brought over his preamp and I had the Psvane 805-ATs in the mix; they worked extremely well in that setup.

    Regarding the Elrogs, mine are the newer label version but with gold bases. As of the time I ordered mine the gold bases were standard and I had no idea they have since moved to black bases( referring to @Strat-Mangler 's images above). In terms of sound impressions, in a nutshell, the Elrogs are just extremely more musical than the stock tubes and the EML XLS. I've come to realize that they do bass just as well as the EML XLS but simply in a more controlled manner. Their calling card is great tonality, dimensionality manifested by how the sound of instruments propagate from them with delicious decay. Due to this portrayal of instruments, they all stand out of the mix with relaxed relief - the mind simply does less work. I'm trying to explain it without using words like soul, heart, etc. My EML XLS were sold to a local audiophile who has Coincident Frankensteins and he loves how they brought his amp to life with dynamics and soundstage growth. Win win.
     
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  25. Encore

    Encore Forum Resident

    Has Elrog solved the reliability issues?
     
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