Hi All, Been away for so long that I was not even aware of ... all this. Worderfull stuff, wonderfull adventure. I'm very happy for you. I've read Maxx review (bless him) and I'm impressed. Maybe one day I'll buy one ... and mod it to death ! :ksc75smile: Redge78

The MK8, even more than the MK6 due to its specific power tubes, being OTL is a "High voltage swing" / "Low current" amp. It fits perfectly the low power & high impedance receivers (our Senn headphones are a blessing for the OTL community).   When you decrease the impedance of your receiver...

Sorry for the late answer, i have had a busy personal/professional life these last weeks. It will be more calm during summer, I hope.      Quote:   The overall idea is not to lower the total R, but to "decouple" as much as possible the Signal loop (Energy provider > Tube > Headphone)...

    OK, you've got your boundaries here, let's say a 3000$ for a "pair of Output Transformers" Vs 3000$ for a "pair of 300B" (just an exemple).   I'm pretty convinced that the real difficulty is to find the right balance between the "circuit design", the associated costs and the final sound...

You've got your Quest, Sir Galaad !  Go find the Truth !    

I'm afraid you'll find it "old-fashioned" but it has 2 strenghts : it's easy to implement (not so easy after some thaughts tho) and I can understand it.   I took the "energy" viewpoint, how much do I have of it and how fast it can be delivered ...   Our (power) PSU is basically an "average...

[...Extending (and partially breaking) my boat metaphore; decoupling the rails as closely as possible, it's like both the guy with the laser pointer and the canvas are on the same boat as you are, jumping with the light. Without decoupling, the canvas and the laser guy are on another boat, that...

  Tell him that he would have more room to new decorating ideas !  

  You may have but I don't. I have enough new mods to keep me busy for the rest of the year, not speaking of the mod that I have already implemented and are in test right now.     I don't deny that, even if the term 'information" may be a bit strong. There is a large community of...

For the record, I have (slightly) changed the tittle of this thread, and made an addition in the first post.   For the last 20 pages or so, the discussions have severely drifted from their original purpose. Personally, I find that interesting, even if I would have preferred to have some...

Mogos, I really like the aesthetic of your amp. The only thing is that bothers me are the little holes you've got on the bottom box, they must **** up your ventilation path. The air is supposed to exit from the holes around the tubes ... Pretty sure we already talked about that earlier on, when...

No misunderstanding here. The temp you have on the datasheet will be the max operating value, not the best operating value. Same than all the other caps from all the other brands. This is one point that is utterly important if you want to put those Jupiter in a tube amp. The life expectancy of...

To answer that specific question ... NO   Actually, you should try to be as far as possible from the "max temp" of the cap. A generic rule of thumb ("Arrhenius law") is that you double the life expectency of each 10° decrease from the Max Temp. Originaly, this law is for chemical caps, but...

  For the record, my three first coupling cap replacements were russian : K75-10 (0.33µF/500V) ... nice upgrade from the horrific SCR-PA 0.22µF MKP K73-16 (0.47µF/630V) ... I really liked those ones, very lively TF-3 (0.22µF/600V) ... but I probably didn't have the time to break them...

Don't get me wrong. I understand that your knowledge and experience is far behond mine, and I am happy you contribute. I'm a grown-up man and I can take criticisms and suggestions, as long as they are given in a positive mind-spirit (which I believe is the case). So, no worry about that, at...

  With all due respect, I think that on that OTL thing, you are missing the main point which is "money" ! You cannot really put some crap OT in the amp, too much impact on the sound. A pair of decent OT wil cost (some) hundreds and you have to take into account the "commercial multiplier" on...

  Basically, the MK8 has the same "White Cathode Follower" output stage than the MK6, maybe the value of the anode resistors and cathode resistors may change between the two, but that should be it.   The 6H30 are very linear, with lower Rplate than 4P1L and high Pulse plate current ... it's...

  Don't worry about that, I am pretty confident when saying that we all found this post very interesting and we appreciate the time and effort you put to do it.   I'll "answer" bit by bit, I have to think about a lot of things, and learn even more.   The "NFB reduces the Output resistance"...

    Quote: Sorry, I jumped at the "Lytic" part, missing the "bipolar" ... and yes, bipolar is not electrically required here, I didn't used any of those. If someone did it, it must be linked to some listening feedback, I suppose. And I was under the impression that the bipolar was 2...

  Great ! A schematic we can read ! Nice !   What is missing most is around the Load and how it is wired when used in Single-Ended (with a 3pin jack, I mean) where both chanels share the same "ground" and 2 power channels out of 4 are unused. Again, I didn't pay much attention to it as I...

It may be a bit late to answer that ... but here it is (the subject is interesting anyway)   "Why use a bipolar electrolytic as a cathode resistor bypass"  That was our first mods, we were experimenting and changing from a crap 2p component for a "audio grade" Silmic (+RIFA bypass) was...

  Excellent job SonicTrance. Exactly what i like. The text/pics have been copied in page 1 under section 3 ("around the Power cathode").   If you want to make changes, plz PM me.    

You have to remenber that all our amps have mecanical fans, some with adjustable fan speed. It helps tremendously to remove heat out of the box, stopping the slow building up on some areas. We are very conscious that we have to take care of our $$$ boutique caps if we don't want to change them...

or they needed the extra amplification of the 12AT7 to achieve a decent voltage swing for the Hi-Rez headphone ... or it was just cosmetic ... or it was just to cut costs ...   The 12Ax7 family has never been thaught for audio anyway and can easily be upgraded by ... anything else really.

Guys,   I'm a little confused here ... are you talking about the "Burr Brown OPA445AP" chip here (the only ones in the MK8) ? Or is there another one for the MK6 ? Because if it's the OPA445AP, the pinout above is vastly different from the official datasheet :       And without the...