[Kouzelna]

Also, since it's not switchable, what would be involved in converting the M Stage from 110 to 220 once I move?  Is it even possible?
 
P.S.  I will indeed list my Millet Starving Student Hybrid tube amp for sale, if there are any takers.  I have the power supply and 2 extra pair of never used NOS tubes included.    I have a 100% feedback rating on eBay with 114 sales, and 99% or so on Amazon with 40+.
 
http://www.head-fi.org/t/590473/fs-millet-starving-student-hybrid#post_8055334

 

[Acix]

Quote:

Also, since it's not switchable, what would be involved in converting the M Stage from 110 to 220 once I move?  Is it even possible?
 
P.S.  I will indeed list my Millet Starving Student Hybrid tube amp for sale, if there are any takers.  I have the power supply and 2 extra pair of never used NOS tubes included.    I have a 100% feedback rating on eBay with 114 sales, and 99% or so on Amazon with 40+.

The V-100 use 4-5 NE5532 opamps, maybe you can find some evidence of rolling warm opamp in the M stage amp.

 

[Kouzelna]

So, is replacing an opamp is a fairly simple process?  And if I understand correctly, just like with replacing tubes, replacing an opamp changes the sound signature, correct?  

 

[Chris J]

Quote:

You need an amp that has an output impedance lower than 62 Ohms, which is the impedance of a K-702.  An OTL won't have an output impedance low enough (read up on the damping factor if you're not familiar with it) save for the Zana Deux, which is outside your budget.  Its 6C33C tubes have a low output impedance, and it is the only OTL of its kind available outside of DIY projects.
 
Otherwise, you need a transformer-coupled amp.  Output transformers are not cheap.  The least expensive transformer-coupled amp is the Bottlehead Smack at $500 and you have to assemble it.  I've paid $500 for a pair of Sowter output transformers, not including the rest of the amp.
 
However, you can find a good solid state amp for $300.  Solid state has a low output impedance and you don't have to spend a lot of money on a high voltage power supply or output transformers to get it.  And solid state sounds good, too.  The end goal is to make your headphones sound good.

Lower than 62 ohms?
Say what?
I think you mean lower than 6 ohms.
 

 

[smial1966]

Kouzelna,
 
My amp recommendation was the ALO Continental MKI and not the ALO RX MKII, as the former is a tube/solid state hybrid and the latter solid state.
 
Cheers.

 

[Kouzelna]

Smial1966 thanks for the recommendation.  Appreciate it.
 
Problems I see with it, though it looks terrific, are first that the tubes are rare and second it has a rechargeable battery system again, which I don't like.  It burns out in only 6 hours and then takes 3 to charge back up.  But it all boils down to how it sounds with my K702, and for that, I sure wish I could test them out or buy them all and sell what I didn't like.  
 
The real issue is price, cost $500 and right now I guess I'm settling for the M-Stage as it's priced lower.
 
Thanks again!

 

[Kouzelna]

So I went ahead and got the M-Stage.  Found a good deal from a great seller on Amazon.  However, the unit is not switchable it is only 110.  This is bad for when I move, as Europe requires 220.  So at that point (probably this June) I'll need to sell it and buy a 220 unit, unless someone has a better idea?
 
Will write all about it coupled up with the AKG K702 once it arrives.  
 
As I'm now on Top Ramen rations due to this purchase, I once again humbly direct your attention to my Starving Student Hybrid listing, upon which I've now posted some handy photos:
 
http://www.head-fi.org/t/590473/fs-millet-starving-student-hybrid#post_8055334
 
Cheers, and thanks for all the help!

  I'm in San Diego if anyone is around to test out some of this stuff.

 

[Kouzelna]

 
Some new possibilities arrived:  
 
A friend is offering me an Objective2 built by him from the kit from JDSLabs.  How's the feeling that this would be the amp to properly drive my K702?  JDSLabs' website says that it is.  Comparisons to the Matrix M-Stage I just actually bought?  Anyone know a review posted here on that subject?  I can't find one.
 
I'll have to keep one and sell the other, so it'd be nice to hear some thoughts.
 
Finally, I got sucked back into the tube realm again reading through more posts.  I never realized the Little Dots were so affordable.  And then, the subject of OTL vs ? comes up again, which sadly I truly don't understand.  If anyone has the time, if you could give me a quick 1 - 3 paragraph summarization of what type of amp works with my AKG K702 and what types don't, both tube and solid state, and why this is.  Man oh Man, I would definitely appreciate that.
 
If I had the cash, I'd just get a Woo Audio 6 which I've heard perfectly matches the K702.  But again... I don't even know why that is.  
 
However, I found this from an old 2010 post by Happy Camper:
 

I have been a proponent of a tube somewhere in the circuit to give the 701s some character. Using an SS amp with a digital source is just too much sharpness for my tastes without EQ. Of course this is only my opinion and should be taken that way.
 
SS amps are cheaper per watt of power but when you are trying to get a little warmth out of the 701, the tube amps will do a better job. The tube amps cost more per watt because of the power supply needed. The 701s will not sound like a Denon or Senn because they are made for recording/mixing. Tubes will bring some warmth to that presentation at a cost. Budget tube amps will cut cost in the power supply. One option would be to use a tube output DAC or CDp into the SS amp. Another is a hybrid amp. This allows the efficiency of solid state with the warmth from a tube source. Yes it is distortion but all amps do. Tube amp distortion is more pleasant to the ear than SS amps.
 
Having to max out the volume to get the 701 to sing is undersized.

 

 

[Chris J]

 
AKG K702s have an impedance of 62 ohms.
 
As a rule of thumb you want the output impedance of the headphone amplifier to be approx. 10 times less than the impedance of the headphone.
Theoretically the lower the output impedance of the headphone amplifier the better: lower damping factor, less frequency response interaction between headphone and amp, less distortion.
The Matrix M Stage has an output impedance of 5 ohms. This is undoubtedly one of reasons why the Matrix M Stage is a favourite of K702, K701 and Q701 fans.
 
Vacuum tube amplifiers often have a higher output impedance than solild state amps.
To answer your question, there are two types of vacuum tube headphone amps:
those with output transformers:        they will usually have a low output impedance, but are more expensive
those without output transformers:    these are referred to as OTL (Output Transformerless), will usually have a higher output impedance and will tend to be cheaper (output transformers are one of the most expensive components in a vacuum tube headphone amplifier.
 
Theoretically OTL amps work better with higher impedance headphones, say 250, 300 or 600 ohm headphones. 
Lower output impedance amps (solid state or tube) are more versatile and can be used with low AND high impedance headphones, as long as they have enough power.
 
However, some folks, like me, enjoy the sound of their OTL vacuum tube amps with their AKG K702.
Personally I have a pair of Q701s and a La Figaro 336C OTL amp and am quite pleased with the sound of that system, I find it warm and relaxing for some music
But I also like to use my Q701s with my Matrix M Stage: tighter, punchier bass, and a more articulate, crisper sound for music with drum sets (for example).

 

[Kouzelna]

Chris J you're the man!  Thanks so much for the class lesson.  Now, finally, this makes sense!
 
So in the future, if I was looking for a headphone amp, I'd want to have saved up my pocket change and be looking for a non-OTL tube amp.  Correct?  (Is there a name of a non-OTL tube amp, besides "non-OTL?")
 
Tube amps I've owned in the past that I really liked include the Glow Audio Amp One, and Peter Millet's original HA-1.  Any way you can find out if these were OTL or not? Because they both were dynamite with the K701 and 702.  The two Millet Starving Student Hybrids I've owned were also good, just not good enough.  You love 'em, but are always ready to upgrade once you have the money.
 
I hope I like the M-Stage too.  I'm worried I will miss that laid-back, warm tubey sound which I love so much, and which does so much I feel to balance the analytical nature of the K/Q 701/2 series.  I had a Grace 901 a few years back, and that thing just shredded music down to its component parts, even with a top notch source.  After a while, I had to sell it.  None of my music sounded musical anymore.  Was like the music was on the operating table, and I was a scientist dissecting it.  
 
Guess that's why it was designed for audio engineers.  Perfect for that.  Not so perfect, I think, for listening.  At least to the stuff I like.  (Vocal Trance predominantly, when I listen to headphones.  For which tube amps do a world of good - transports them to a magical plane!)

 

[Chris J]

Quote:

Chris J you're the man!  Thanks so much for the class lesson.  Now, finally, this makes sense!
 
So in the future, if I was looking for a headphone amp, I'd want to have saved up my pocket change and be looking for a non-OTL tube amp.  Correct?  (Is there a name of a non-OTL tube amp, besides "non-OTL?")
 
Tube amps I've owned in the past that I really liked include the Glow Audio Amp One, and Peter Millet's original HA-1.  Any way you can find out if these were OTL or not? Because they both were dynamite with the K701 and 702.  The two Millet Starving Student Hybrids I've owned were also good, just not good enough.  You love 'em, but are always ready to upgrade once you have the money.
 
I hope I like the M-Stage too.  I'm worried I will miss that laid-back, warm tubey sound which I love so much, and which does so much I feel to balance the analytical nature of the K/Q 701/2 series.  I had a Grace 901 a few years back, and that thing just shredded music down to its component parts, even with a top notch source.  After a while, I had to sell it.  None of my music sounded musical anymore.  Was like the music was on the operating table, and I was a scientist dissecting it.  
 
Guess that's why it was designed for audio engineers.  Perfect for that.  Not so perfect, I think, for listening.  At least to the stuff I like.  (Vocal Trance predominantly, when I listen to headphones.  For which tube amps do a world of good - transports them to a magical plane!)

Hi Kouzelna,
 
Thank you for your kind words!
Typically the amps with output transformers are called "Transformer coupled".
The amps without the output transformers are typically called "OTL".
When I get some time tonight I will look up the specs on the Glow and the various Milletts.
 
As you can see, a lot of the guys tune the sound of the M Stage by replacing the Op Amp in the M Stage. I've tried this and it does not radically change the sound of the M Stage.  I'll say one thing for the M Stage, it is very popular with K701/702  and Q701 owners so the must be doing something right!
But I agree with your comments about tubes and the "magical plane"!
 
Chris
 

 

[Kouzelna]

Chris,
 
Yeah, I am really looking forward to the M-Stage with my K702, since the going theory is that it's a perfect match for the price range.  Should arrive Friday.  Maybe sooner!  Will definitely post my thoughts.  Should be extra awesome as my current amp really doesn't drive my cans well enough.
 
Thanks for looking up the specs.  Gives me something to shoot for in the future.  I was thinking a Glow again, or, a Woo.  And thus I guess that would be the Woo 6, as I understand that one is transformer coupled, while the Woo 3 is not.
 
David

 

[Chris J]

Hi David,
The Milletts all seem to be variations on OTL.
What can I say?
If it sounds good....
 
In addition, the Schitt Valhalla is OTL, but some people like it with K702s.
And some people say the Vslhalla does not sound very tubey.
The Glow seems to be transformer coupled.
 
There is  thread with a comparison of Grado SR-325, AKG K701, Sennheiser HD650 and Beyer DT990 by a young lady called Dubstep Girl.
EDIT:   Thread is called  "Comparison of four popular cans from $275-350........"
She uses a Woo Audio amp (can't remember the model).
If you do a search you should be able to find the thread, she loves the Woo and the K701!
 
Confusing as all hell, but everyone likes something a bit different!
 
Chris

 

[Kouzelna]

Sweet!  
 
Actually, at the time I used an HD600 with the Millet HA-1, and it was my first real setup.  My next was the HD650 and Grace 901, along with an ER-4S that sounded so good and was so practical (I was married at the time), I sold the Senns.  So what do I know?  
 
But my current setup is, I think, underpowered.  It sounds good, but there's more potential I can feel it.  And that's the K702 with the Starving Student.  Great amp, but the K70x series needs more, I think.  Greatly looking forward to comparing the M-Stage and Objective2 with these headphones.
 
The Glow with the K701 I had at the time just flat out rocked!  I have a huge review here on it, with a bunch of great headphones.  Find and enjoy.  
 
I'll look for Dubstep's thread.  Funny, I have an old Dubstep mix... If I'm not mistaken, that's old school Techno, man...  Wonder how she got introduced to that.

 

[liamstrain]

edit.... outdated. answered an old post.
 
But about Dubstep girl, she uses a Woo 6 SE, which is transformer coupled. 
 
The Beezar Torpedo DIY amp is transformer coupled and might be worth looking into, if you want to go tubes for less (should come in under $300). Likewise the Bottlehead Smack (around $550). 
 
But some OTL amps do seem to work well with the K702. Just a matter of preference, I guess.