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Little Dot MK8SE / MK6 Super Mods (All verified mods are on first page)

Discussion in 'Headphone Amps (full-size)' started by redge78, Sep 26, 2015.
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  1. baronbeehive
    Thanks!

    Looking forward to getting in some serious listening with those WE's….. and finishing the mods!

    Modding can be a problem, constantly rearranging the components inside the amp, that's what caused the cap leg to break off, unknown to me.
     
  2. baronbeehive
    ANODE/CATHODE listening tests: The Results...

    [​IMG]

    The graph above showed my proposals in green.

    upload_2018-8-26_15-31-2.png

    I've recalculated the graph with my revised B+ of 185v. The graph shows the region of interest where we are looking for the best operating points.

    I tested 20 positions in all including 2 types of 6SL7 driver tubes and high/low gain settings.

    I've got my amp up and running again I've been able to finish the anode/cathode experiments for the driver stage that I had started previously so here's what I did for these tests:

    I've stuck with the RCA 6AS7G's for the purposes of the experiment because I had already started the experiments using them, before getting the full set of WE's, and I'm used to the sound. For driver tubes I used TS 6SL7's and GE 12SL7's, which are my favoured sets now.

    I used the same test tracks, including some high res tracks, for all the tests and the same volume level as far as possible.

    I made notes as I went along in brief comprising soundstage, bass, midrange, treble. Initially I also compared high/low gain settings but as I preferred high gain, I decided to stick with this and not evaluate it further after the initial results because I believe there is enthusiasm to see how high we can go with the gain settings in future, I found no downsides with high gain. I desoldered my gain switch due to its unreliability. By the time I had nearly finished the tests I wrote more abbreviated notes referring to other positions rather than repeating myself over and over.

    I found that pretty much all of the settings sounded good, with the exceptions of those with scores of -1, and would not discourage anyone from using any of these settings, the difference is mostly a matter of personal preference, and at this level differences are not that great, I used a numerical evaluation, for example starting at 0 for the baseline - Sonic's and my settings - with anything at 1 indicating a preference over the 0 level but with this not indicating a massive difference such as a score of 2 would indicate. I've indicated why I thought one setting was better than another but you have to bear in mind that where there is a difference of only 1 point there is a subjective element in all of this. Only a score of 2 would indicate a definate, objective, indisputable difference. I didn't think any differences justified a score of 2 because there were no massive differences such as is the case for example when changing RCA power tubes for the WE's. Having said that there was one position that I nearly gave a score of 2 to!

    One reason all settings sounded pretty good I think was because the voltage swing on this amp is not great as MrCurwen said before, so that even if an operating point was chosen for a tube which was close to a non linear region on the graph it would be unlikely that the swing would go near to the non linear part of the grid curves. This is probably a strength and a weakness of this amp. Another reason is that we are already in the good regions and trying to find the optimum points but I decided not to test the extremes because I wanted to stay in the linear parts, so for that reason there would not really be a huge difference. Anyone who would like to look into those non linear regions, feel free!

    We have now looked at a range of operating points and currents for the tubes, we are limited by the voltage we can get so I don't think there's much we have missed concerning the tube operation now. One thing, I believe that the amp sounded better with the 2 last R, 3K3 resistors lowered in value to give a B+ of 185v on my amp.

    To summarize my results there was one stand out position which hit me the moment I started listening, the sound was full, palpably real with good clarity and texture which you could almost feel. The sound had a presence, transparency, resolution and dynamism. This for me was the obvious setting to use. I was a bit surprised that my proposed intermediate settings in between Sonic and Maxx's settings were not my favourite, probably because it fell in the middle it was neither one thing nor the other. The best operating point was with an anode of 69K and cathode of 380R, point 7 in the graph. I will scan in my notes page later so you can see in more detail.

    The tests also confirmed my choice of driver tubes, I've gone from preferring the TS 6SL7 to the GE 12SL7 because my experience with the other amp made me prefer a sharper, more lively sound which the GE does well, for only a couple of dollars too! The sound of the GE is better for hearing things such as the sound of the plectrum on the guitar string, whereas the TS 6SL7 has a smoother, more liquid yet still detailed sound. The surprising thing about my preferred position is that it happened with the RCA 6AS7G's in, so if it's that good I can't wait to try the new setting with the WE's!

    I hope this has been useful for others trying to find the settings which suit them.
     
    Last edited: Aug 26, 2018
    Maxx134 likes this.
  3. baronbeehive
    upload_2018-8-27_11-43-37.png upload_2018-8-27_11-44-24.png

    The baseline was at my current settings of 33K - anode, and 380R - cathode, which was a setting that Sonic and myself had chosed to be very good for sound quality. The scores of 0, or higher were therefore at least as good as this. Going through the anode settings as follows:

    33K - good baseline score, with cathode of 380R, as above, however at 2 of the cathode settings, 1K and 1.5K, I felt that the sound was somewhat flat and lifeless. High gain sounded better, slightly more transparent, with both 6SL7 tubes.

    46K - again, good baseline score or thereabouts, with cathode of 380R, but with the GE tube with scores of 1 for bass, mids, treble, and soundstage I felt that this justified a second place position for SQ. Very good transparency and detail. With the 1.5K cathode the scores fell to -1 with a flat rather lifeless sound.

    69K - here with all 3 cathodes I felt was the best sound with all 3 cathodes the sound was considerably above baseline. With the 1.5K cathode I felt that with the GE tube it justified second equal position in SQ. With the 1K cathode and with both 6SL7's I felt that second equal position was justified with full bodied, incisive, real and transparent sound. However as soon as I started listening with the 380K cathode in I knew straight away that I would be very happy with this setup. The sound was full bodied, had a real presence, and had the most texture to the transients and treble which gave it a dynamism. For example piano had weight and attack, guitar notes stood out, vocals sounded real, bass had weight and definition and drums had attack, you could almost feel the kick drums.

    I don't want to overplay this, as I said all settings sounded good, except for the ones with scores of -1 which were a bit lifeless sounding, but anything on 0 or over sounded good but I felt that some with scores of 1 sounded just that bit better and the best position I liked immediately, but those scores in second place were not much different to first place. Interestingly I thought that all the positions in the anode setting of 69K were best so I wondered if the anodes were more important for sound, while for the other anodes nearly all positions apart from the baseline position, scores were worse with the most lifeless sound.

    I would recommend that overall it would be best not to use the 33K anode setting, or the 1.5K cathode settings and go for the first place or one of the second place settings.
     
    Last edited: Aug 27, 2018
  4. NNewman
    Hello. Sorry to ask in this thread, but in other places I have already got nothing...
    And the maasdrop drop time counts down and I need to make a choice quickly.
    I m looking for a good pair to my SS headphone amp in the tube field. Currently I m choosing between LD Y1, LD mk6+ and LD mk8 se. Tube pair is seems to be "working" only with HD800, AKG k340 and LCD4.
    LD mk6 is not preffered as it has an active cooling and for a bed time setup it might be crazy bad idead. My wife might send me out to sleep on the coach. :) But I must be 100% sure if MK8se is really good pair for LCD4...
    • Please share with me your oppinion about this 3 variants.
    Thanks in advance.
     
  5. baronbeehive
    No worries, the other thread is grinding to a halt now!

    Sorry I can't be much help, I don't have the headphones you mention, and I've never heard of the LD Y1 and had to look it up.

    Re: your headphones, the HD800 I think does work with the MKVI, I've heard people say so but obviously the MK8 is preferred, probably also for your LCD4. I don't think you would go wrong with the MK8, but it's only my opinion based on what others here have said.

    The type of sound you get is good balance, refinement, resolution, and great soundstage. The sound is not tubey but clear and musical, I would say it falls between the tubey 300B and the hotter SS type sound. I don't want to say more because someone with those cans may come on.

    Hope that has helped with your choice.
     
  6. NNewman
    Hello. Thanks for the answer. LD Y1 was a flagship for some years, until now when Y2 was out. Y2 is just an upgraded version of Y1: new traffos, DACT volume control and many many more. If somebody is interested I can post a detaild photos of Y1 here...
    To MK8SE: I think that I have read any where that change of the power tubes to another type brings a noticable power boost... is it right? Or I have messed smthg?
    One more question: tho OPamps in MK6 and MK8 are out of the sound path?
     
  7. baronbeehive
    Nearly ready to implement to CCS.

    NB: this is a dummy run, the resistors etc are not correct so I labelled the correct values. I've compressed it as much as possible so that it will fit!

    upload_2018-9-2_13-2-33.png upload_2018-9-2_13-4-30.png

    upload_2018-9-2_13-5-57.png

    Does that look right?

    I'm a bit worried that the amp might go up in flames....
     
  8. MrCurwen
    No, the worst that could happen is the CCS self-destructs.

    What FET are you using, why didn't you go for the standard IRF8x0 types?

    In the future don't bend the pins so close to the body. When bending a pin always keep part of the pin closest to the body completely straight.

    3D construction looks decent enough, with TO-220 body FETs you can get much better and clearer construction. Use the FET body as a main binding post.
     
    Maxx134 likes this.
  9. baronbeehive
    Thanks!

    Yes, bending the pins close to the body was the reason a leg broke on a coupling cap.

    I'm about to go ahead and build the CCS now and will post pics when I've done it.
     
    Maxx134 likes this.
  10. Maxx134
    I would not reccomend the LDMK8 for that planar.
    If it is a double sided magnet, they require lots of power..
    I myself have had to increase bias and plan to increase cathode cap to offset the drain planars give on this design since it is OTL.

    Anyways, I never noticed that other LDY1 amp and it does looks powerful enough...
     
    Last edited: Sep 4, 2018
  11. baronbeehive
    I think I'm ready to install the CCS now.

    upload_2018-9-5_13-48-37.png upload_2018-9-5_14-4-36.png

    Using all 1w resistors made it a bit more difficult with the size, and thickness of the leads, however it will still fit, I can stick the FET with 3m sticky tape onto the board.

    I will test it before putting in the active filter to see what it's like before and after.
     
  12. MrCurwen
    Decent 3D layout there baronbeehive. Pretty symmetry. I would go for smaller size and less pretty but that'll work just as well. Remember the FET metal tab is connected to the drain, so make sure it touches absolutely no metal anywhere.
     
  13. baronbeehive
    OK, thanks!

    Having made one that I knew would fit both sides I didn't want to chance my luck and do the other one any differently!

    Edit: As I'm removing the cathode resistors where I currently have the driver stage decoupling cap connected to the cathode side, can I simply connect the cap direct to a cathode tube pin and ignore the ground connection which was there on the other side of the cathode resistor?
     
    Last edited: Sep 5, 2018
  14. SonicTrance
    No, because the cathodes are not grounded. Cathode node will be at about 1V.
    You can connect the decoupling cap lead in the same ground hole as the cathode resistor was, if it fits?
     
  15. MrCurwen
    I just looked at your connections in the picture.

    There is no anode connection, only B+.

    B- and filter are the same thing, B- for the CCS is the filter output (I realise you plan to try the CCS before adding the filter). Just making sure you understand to not connect unfiltered B- after you have the filter.

    Not to be annoying, but precision is very important.
     
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