Originally Posted by atothex
I've said it before, and I'll say it again: I don't care for cheap tube amps, OTL or otherwise. I listen exclusively to low impedance phones, and cheap OTLs simply don't have low enough output impedance to damp them well. Grado's are easy enough loads, but my ATs just lose all their bass with most OTLs.
That's why I don't currently own a tube amp.
The reason why the Zana and Microzotl were mentioned here was because their output impedances are extraordinarily low. The Microzotl's is especially crazy, but it's a weird amp, and opinions are mixed.
Anyways, it's up to your own ears, but I would personally choose many things over Little Dot. Namely the CKKIII.
Totally agreed and dead on the dampening factor. Awesome points.
Originally Posted by Skylab
There are two very valid technical reasons that OTL tube amps are not an ideal match on paper for low impedance headphones:
1. The output impedance of most (but not all) OTL tube amps is high-ish - output impedances of 40-60 ohms are not uncommon. Running a 25 ohm headphone off a 50 ohm output impedance is definitely not ideal.
2. Low impedance, high sensitivity headphones want a lot of current swing, but don't require a lot of voltage. SS devices are generally better at delivering current into lower impedance loads. Tubes are, again very generally speaking, better at voltage swing, and less good at current delivery. Frank Van Alstine, a very talented audio guy who prefers tube-ss hybrid designs for amps, prefers them because he considers the vacuum tube an ideal voltage source, and SS devices an idea current source.There is also the fact that a high-sensitivity headphone will be less forgiving of even very low level hum, which some cheaper tube amps do have.
So there are good reasons for people stating the mismatch.
That said, I have found the Decware CSP-2, an OTL tube amp, to work well with low-impedance Denons, and I like the RSA Stealth, an OTL tube amp, very much with the medium-impedance JVC DX1000. So the proof is in the listening and the ear of the beholder, and there are no absolutes.That said, if I was a committed Grado person, I would probably not make a foray into OTL tube amps. For me personally, being a 600 ohm Beyer guy mostly, owning a bunch of OTL tube amps is a pleasure
Grados, Senns and Denons miss you Rob, since you gave all your love to Beyer...
Dead on again and great explanation.
Originally Posted by St3ve
This is what I thought. Hence, me buying a hybrid first time around. But occasionally you see people who seem to have really satisfactory pairings, against all the odds.
Clearly, transformer coupled amps like the WA6 are a much safer bet, given that their transformer allows the output stage to "match" with lower impedance (might be wrong). I would go for an amp like that at the drop of a hat, were it financially feasible.
@ HeatFan12 - I would love to hear your impression of your grados <-> MKIV se
All that being said and since I caught this thread while I was trying out my newly acquired uDac with a tube amp, I did some listening tests.
Here's a pic from yesterday's setup with the uDac (also in the uDac thread)
Westinghouse 5687s and GE JAN-CG-6SN7GT. This amp loves Senns and Beyers and at the time I was using HD650s. Once this thread came up I had my SR225s nearby, so decided to plug them in and give them a listen. Also went up to get one of my Ultrasones.
...I was very surprised at the outcome and thought they would sound "hollow" and not efficient at all. That was not the case, the sound was full, warm, the bass was there and tight too. A very smooth sound that I caught myself listening to the SR225s out of this amp for two hours.
Now on the other side of things as an example. This amp (Xenos 3HA)-
I purchased over three years ago and still own, is unlistenable with Grados. What do I mean by unlistenable? Once plugged in, the volume pot can't even be turned about half a turn, it would be too much in reference to the volume. Not only that, but the sound is very "hollow", "shrilling highs" and just sounds too powerful for them, for lack of a better word. My Senns and Beyers (300 & 250ohm respectively) sound great, the sound is full and deep and the volume knob tracks very smooth.
I thought that was going to be the case (hollow, shrill etc.) with the MPX3, but it was not.
Now onto the MKIVSE St3ve-
Again, really curious after your thread so woke up this morning and set up the MKIVSE where the MPX3 was last night, uDac to Windows 7 laptop all FLAC.
I was going to put in some CBS Hytron 6AK5Ws to add a bit of warmth, but decided against it and kept the GE 5 Star 5654s in there. Nice detailed tube. I figured this was not going to work anyway with my Grados and the sound would probably be hollow etc...
I know David had sent me a new manual in reference to the gain with low impedance phones. Set the gain to "10", used to be "5", grabbed my SR225s and put on some DT (Train Of Thought) and began to listen. Again, not expecting much...
...Full bodied, warm, smooth, detailed and not fatiguing at all. Myung's bass lines on In The Name Of God were so present and sounded crisp, where sometimes they get clouded in the backround. Don't really need to say anything about the other John, of course the guitars were everywhere and sounded amazing...
Up next my RS1i with "Live At Budokan"...Good times...
At the end of the day, we have to let our ears be the judge if the match is good or not.