[Rawrbington]

Quote:

 
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).

hey chris,
question for ya,
why do you think it still sounds so good with such a high output impedance?
i agree with you, i love an OTL sound and with most of my headphones the sound is still very clean and crips. unless were talking 32 ohm cans, then the mismatch really shows up.
but like the hd 650 with my amp only has a damping factor of 3.
but still sounds incredible.
How?

 

[Chris J]

I'm going to have to find the Glow review!
 
i just edited my previous post,  check it out.
  
Dub Step Girl used  a Woo WA6SE, expensive as all hell and transformer coupled.

 

[Chris J]

Quote:

hey chris,
question for ya,
why do you think it still sounds so good with such a high output impedance?
i agree with you, i love an OTL sound and with most of my headphones the sound is still very clean and crips. unless were talking 32 ohm cans, then the mismatch really shows up.
but like the hd 650 with my amp only has a damping factor of 3.
but still sounds incredible.
How?

The $ 5 Million question!
 
Technically it should not work all that well, but it does anyway!
 
Theories:
 
Tube circuits are simple,  maybe this creates a purer sound?
 
OTL circuits gets the transformer out of the circuit, maybe no transformer is better than a cheap transformer?
 
maybe we like the sound of the distortion?
 
I want to get a pair of Grados, some these guys on Head Fi say they suck with OTLs, that's just what I've read...........sounds like that is your experience too?
 

 

[Rawrbington]

i had a pair of 32 ohm 770s, it just didn't work very well at higher volumes.
but the 80 ohm beyers sound nice, as did the shure 840s.
who knows why?
 

 

[Chris J]

Quote:

i had a pair of 32 ohm 770s, it just didn't work very well at higher volumes.
but the 80 ohm beyers sound nice, as did the shure 840s.
who knows why?
 

 
I assume you are talking about your experience with an OTL head amp?   Thanks, looks like I'm not using my 336C with any Grados I get in the future!

I'm going to guess that the OTL amp you were using doesn't deliver enough current for low impedance 'phones.
A typical characterisitic of OTL is they do not output a lot of current.
 
Another thing about OTLs is they can output a fair amount of voltage which is great for High Impedance 'phones.
My OTL amp works great with my 600 ohm phones and my 2,000 ohm phones.
 

 

[Chris J]

Quote:

i had a pair of 32 ohm 770s, it just didn't work very well at higher volumes.
but the 80 ohm beyers sound nice, as did the shure 840s.
who knows why?
 

I really have to pay more attention to your signature

 
Your signature shows a Woo WA2, colour me green with envy!
I guess the 32 ohm Beyers didn't like the Woo WA2, reason is probably not enough current available at the output.   More current = more volume.
Which leads me to say:  Too bad they don''t make high impedance Grados!
 
One more thing about SS and vacuum tubes:
 
You can design just about any SS head amp to be very low output impedance, but the designers often create a high output impedance by ADDING resistance to the output.
IMHO they should just concentrate on making the output impedance as low as possible to allow them to drive any 'phone (within reason). 
Transistors (and Op Amps) are low output impedance devices.
 
OTL vacuum tube amps inherently have a high output impedance because the output tubes have a high output impedance.
 
One of the purposes of the output transformer in a transformer coupled vacuum tube amp is to reduce the output impedance of the amp.
 
 

 

[Kouzelna]

Thanks for the info on the Torpedo, liamstrain.  I have a friend who'd be able to put that together for me, I think.  
 
I would LOVE to hear what Dubstep thinks of her Woo WA6 matched with a K702.  Has she posted anything about that?  I'm still waiting for an elusive person to post some comparisons between the Glow and WA3 or WA6.  
 
The M-Stage arrived today, one day early.  

  I'll post my thoughts later this weekend.

 

[Chris J]

Quote:

Thanks for the info on the Torpedo, liamstrain.  I have a friend who'd be able to put that together for me, I think.  
 
I would LOVE to hear what Dubstep thinks of her Woo WA6 matched with a K702.  Has she posted anything about that?  I'm still waiting for an elusive person to post some comparisons between the Glow and WA3 or WA6.  
 
The M-Stage arrived today, one day early.  

  I'll post my thoughts later this weekend.

Dubstep Girl's headphone review:
She reviews the K701 with a Woo WA6SE in here. She says "AKGs are awesome!"

http://www.head-fi.org/t/576061/comparison-of-4-popular-cans-in-the-275-350-range-k701-hd650-dt990-600ohm-sr325is
 
Interesting article about distortion in audio amps, the interesting thing is that the distortion in a lot of vacuum tube amps is predominantly second order harmonic.  The artilce explains it in more detail.
https://passlabs.com/articles/audio-distortion-and-feedback
 
Can't wait to hear your Matrix thoughts!
 

 

[Kouzelna]

Thanks Chris, am reading the review and the article on feedback.  
 
Questions:
 
a.  what is the difference between output voltage and output current?  does it differ between SS and Tube?
 
b.  which headphones have 2000 Ohms!?

 

[liamstrain]

a. Power = current x voltage... high impedance cans need high voltage, low impedance cans need high current. Tube amps, OTL especially, are primarily high voltage. 
 
b. broadcast headphones, normally

 

[Chris J]

Quote:

a. Power = current x voltage... high impedance cans need high voltage, low impedance cans need high current. Tube amps, OTL especially, are primarily high voltage. 
 
b. broadcast headphones, normally

He was asking about my 30 year old Sennheiser HD424 headphones. Old but they still sound good. Not the world's greatest by any means but I still use them every now and then.  Rather bright, BTW, the opposite of Sennheiser HD650.
Apparently older headphones normally have a higher impedance; 600 to 2,000 ohms.
 
Far more than you ever wanted to know about impedance, power, voltage and current can be found here!   http://www.head-fi.org/a/headphone-impedance

 

[Kouzelna]

Thanks again guys for the info, and the link.
 
[size=10pt]The M-Stage so far is great.  But on first listen it falls short in comparison to the Glow, which of course was about 3x the price.  My point being that the M-Stage really gives the K702 some power behind it, which is the first time I've heard it like that in a while, having used having used amps that weren't designed for it as of late.  Suddenly all kinds of details and effects are present, where before the music sounded good but rather flat and one-dimensional, as if the effects weren't working.  (I listen to mainly Vocal Trance when I listen to headphones - lots and lots of precision layering and effects).  Also, it provides the K702 with the best bass I've heard it ever do, including counting the Glow.  And wow, does it really shine: precise, punchy, not the slightest bit of boom.[/size]
 
[size=10pt]However, there's a place where you know the K702 wants to take off and do more, and that's where the Glow was able to provide for it.  With the Glow, as I've written extensively, the music seemed effortless, as if it came out of a vacuum in space.  It's like nothing was between you and it.  It just had ample room to move and breathe and express itself.  With the M-Stage, it seems to be running into limits, and I can hear them when it does.  Kind of like a singer that runs out of air at a critical moment.[/size]
 
[size=10pt]Dub step girl said:[/size]
 

With ambient/trance music, everything just seems to float out in space and have no end, its quite an experience on some songs.

 

[size=10pt]She was exactly right, as to my experience with the Glow, and I guess with the WA6 too as that is the amp she's using when making that statement.  But with the M-Stage, the music sounds far more compressed to the width of your head, basically.  There are moments I remember with the Glow that the music would soar far outside the dimensions of my head and seem to fill the room, but those are the moments where with the M-Stage the music seems to bump up against an invisible barrier and go flat.  It's not just limited in that sense, but the limit is obvious, and sounds awkward.  As if the music went "splat" against a glass wall.[/size]
 
[size=10pt]However, I'm just not being fair.  The M-Stage for it is, at at the price I paid, is just awesome.  I'm really going to enjoy it.  I will enjoy putting a lot more time into it next week.  [/size]
 
[size=10pt]It's also put together in a far more practical package than my Glow was, allowing for me to transport it easily enough when it finally comes time to move.  I'd be very, very interested to hear thoughts in comparison to the HeadRoom Micro, from someone who's heard both, which is another amp at least relatively in my price range (sort of).  And of course, I'm excited to hear it compared to the O2 which I should have next week or so.  [/size]
 
[size=10pt]One worry is that the O2 is a whole lot smaller amp than the M-Stage, which is pretty long.  Would that necessarily prestage the possibility of it not being as good?  An amateur question, I guess, but it would seem tough to me to pack quality power into a thing so tiny, which is what the K702 seems to really need.[/size]
 
 
 

 

[Chris J]

 
Hi,
 
Short answer:
Your impressions of the M vs. the Glow are basically the same as my impressions of the M vs. my La Figaro 336C.
One nasty qualifier with the 336C, you really have to replace the stock Chinese tubes with some better tubes to get it really going into the astral plane.
Fortunately it only has 2 tubes.
 
The O2 has a much smaller power supply than the M Stage. The O2 uses batteries. I've never heard the O2 so can't really comment on it.   The owners see to really like it.
 
C.

 

[Kouzelna]

Well, I'll be getting a completed O2 fairly soon, probably late next week.  If anyone is interested, let me know by PM, as I'll either be selling it or the M-Stage.  (Whichever one I like less, though I imagine they're both good.  Don't have the funds to keep both).  They are both brand new.
 
The M-Stage is already getting better.  I don't know if it has "burn-in" like headphones, or I just had to get used to it.  The other thing, is that I'm a little ill, and perhaps when I was laying down my sinuses got stuffed up and my ears weren't hearing right.  (Bad time to write a review!)  So anyway, when I sat up later and was listening while surfing Head-Fi, I was able to appreciate them a lot more, and they weren't quite as limited.  Not a Glow, of course, but still awesome and I'm really getting to like them.  SS is quite a different sound than tubes, but with Trance it has its own allure and merit, being an entirely electronic form of music anyway.
 
Also, the M-Stage is entirely silent, and fairly dark sounding.  So it's really a good mix for the bright, airy K702.  Seems to reign her in just enough, and smooth out the rough edges in all the right places.  Kind of like my feisty ex, when I could get more than one glass of wine in her.  

 
BTW, here's a great review of the M-Stage for those of you considering.  It really is astounding for the small price.
 
http://www.head-fi.org/t/475618/matrix-m-stage-amp-review-simple-cheap-and-excellent

 

[Kouzelna]

 
BTW - Does anyone know the best gain settings with the M-Stage for the K702?  Right now I have to crank the volume to 6 to get a good sound.  Thankfully, the dip switches are easily accessible at the bottom of the unit.
 
The choices are:  0dB  10dB  18dB  or 20dB.
 
Thanks!  Sorry to double post, wanted this separate.