[svmusa]

I do agree on making instant A-B comparison difficult and subjective, but generally on few reference songs you can start picking the differences to land on a tube that gives the right synergy and sound signature with the headphone and source collection - that was my end goal with tube rolling.
 
I referred to an old MicroZotl original version tube rolling thread and picked the Sylvania 5692 and Kenrad 6SN7 with Sylvania GB 12AT7, the recommendations from that thread were right on.... seems like I personally lean on sound signature with bass and neutrality in rest of the spectrum so Kenrad suites me well but if I had to recommend a good tube that can satisfy a typical listener than I would go for Sylvania 5692 and Gold brand 12AT7. 
 
Stock tubes I find bass has less definition but rest of the spectrum sounds fine with a tad less energy and impact than my NOS tubes, overall for me the NOS tubes brings a good 25% improvement over stock tubes in my own setup. 
 
It would be great to hear others learning as well..here is the old thread for those that are into tube rolling. I have been using conclusions from scottpaul_iu 
 
http://www.head-fi.org/t/8494/microzotl-tube-rolling-thread/60

 

[doctorjazz]

OK, thanks, get back to listening if I ever get the PC sound back
(meantime, GO BRONCOS!)

 

[doctorjazz]

Broncos won! Yay!
Got Ponomusic world working again (had to reinstall drivers, uninstall the Ponomusic World program and reinstall it...Have JRiver21 with the same problem, but it's a bigger pain to do it with JRiver since you need to enter the registration numbers, which I would have to get from them, can live just fine with Ponomusic world, it is JRiver without the video part).
Anyway, my non burned in, non comparison, unscientific, totally biased (hahahaha) impression, after a few minutes of listening to them, is that I like these NOS RCA tubes. Seems to have a bit more presence, immediacy, compared to what I remember of the stock Sovteks, which is a good thing for my HEK, which leans towards laid back (of course, I may change my mind after burn in, or on recomparing them). Maybe lose a bit of clarity, not sure, but they have about 10 minutes of listening time on them.

 

[jelt2359]

What's the general consensus regarding the mzotl2 as a pre?

 

[doctorjazz]

I could try it into the Liquid Carbon, then listen to the HEK, but I'm not sure that's what you really want to know...

(just go for it, I know you want it... )
Back to the tubes, I can see the appeal, if you decide you need to change your sound sig, instead of going out and buying a new amp, a few tube substitutions would probably hold you from upgrade-itis for a bit...cool!

 

[jelt2359]

Was thinking more along the lines of plugging it into the Krell!

 

[doctorjazz]

Need a good unbalanced interconnect to do it, run the Krell balanced from my Peachtree Grand Pre...I'll see what I can dig up.

Was thinking more along the lines of plugging it into the Krell!

 

[willsw]

What's the general consensus regarding the mzotl2 as a pre?

 
Here's a review that uses it as a preamp at AVrev.com.
The AudioCircle guys reviewed the room with the MicroZOTL2.0 as a preamp to the ZOTL40. 
 
We actually test the MicroZOTL2.0s primarily by using them as preamps. Everyone can keep working while enjoying music. Headphones are used as well, of course.  

 

[NightDayAudio]

After some time to listen and compare back and forth with all the other gear here, I am very impressed with the sonics of the ZOTL2.0.  Did a little tube swapping on the 6SN7 variants...not a lot as I don't have the complete collection of every 6SN7 ever made like I used to in the past.... but as a dealer, that is a slippery slope if I am going to demo the amp for possible buyers with non-stock tubes... need to show it in stock form so buyers aren't mad/upset/disappointed when they get theirs and it doesn't sound like it did during the demo.  I have to remember to swap back in stock tubes for a demo
 
Power supplies are an easier demo and explanation in my experience.... so far, I'm enjoying the SBooster the most with it of the options here for us to use.  It adds weight, increases bass depth and definition, and opens things up even more and creates and even more enveloping sound.  Keeps the speed, resolution, detail and openness of the stock unit and just adds more to the overall presentation.  I've been very happy so far with every situation where I added an Sbooster power supply... very very nice product and not really expensive either for the improvements that come with one in the chain... very curious to hear the factory linear power supply in comparison as soon as it is shipping...
 
this headphone amp is not out of place with top shelf electronics in front of it and headphones after it.... I really like it with the PS Audio DirectStream DSD DAC, as well as with the top end Lumin Music network players.  It's also a very nice sounding preamp as well in a home stereo system... lack of remote kills it for us lazy buggers that use network music players with digital files that have wildly varying recording levels.  But it is a startlingly great sounding piece of gear for not a lot of cash compared to its performance.  I don't have any of the ultra high efficiency Tannoys here on display (we're only stocking up to the Definition line and don't have the reference stuff here yet).  So I can't really comment on how well it drives speakers with its lower power output... on lower efficiency stuff here it works but it does run out of juice when pushed.... it is only a watt after all
 
We have the ZOTL40 power amp here as well....  very, very nice on speaker setups... that drives the crap out of anything we have here on display...
 
These are unique product offerings that have a compelling story to tell that will appeal to a lot of customer's sonic tastes and offer a value that is tough to beat.
 
Anyone in the Raleigh/Durham area of NC (or within driving distance) that wants to come hear this and compare it with a multitude of other options is more than welcome.  We've got a good chunk of the comparable products out there available here to listen to, along with all Audeze LCD series and EL-8, Mr. Speakers Ether and Ether C, Sennheiser HD800, ENIGMAcoustics Dharma, ADL, etc. etc. etc. headphones so you can hear everything in one place.  

 

[doctorjazz]

Thanks, will look into the SBooster power supply, just looked at the site, reasonable, wondering if you get more for about 3X the money with the Mojo. Also, don't see US dealers listed, but I can email the company to find out about that. Is Linear Tube Audio releasing their own LPS? Any details on price?
The mZOTL is a great little amp, as you note-Steve Guttenberg liked the mZOTL driving the Klipsch RP-150M high efficiency speakers. I'm wanting to try it as a preamp one of these days, but, as my current main system is balanced, I have to dig up the interconnects to make it work.
I have used it out of my Linn LP12/Pro-Ject Tube Box S, into my HE-1000...man, it makes a nice sound, indeed, though I mostly, for ergonomic reasons, have it in my PC based system.

I replaced the stock Sovtek tubes with NOS RCAs, have had them in for about 5 days now. I think it does nice things for image solidity, bass impact, PRAT, maybe not as open sounding, as much air/space/soundstage as the original tubes, but, as I can't go back and forth yet (still really in burn in from what I've been told), not 100% sure. But it's fun to play with, a bit like getting a new amp (without buying a new amp, though I can see that the tube purchases can start to add up in no time...)

 

[willsw]

We will have a prototype of our linear power supply at the Philadelphia meet this Sunday (we were waiting for the unpainted case to be pulled off the line and shipped over to announce, but oh well). The final version (basically, when the painted cases arrive, as long as they're all good) will be announced, along with date of availability and price, very soon. And for those who already own a MicroZOTL2, we'll certainly be letting you know our appreciation in our release pricing.

 

[doctorjazz]

We will have a prototype of our linear power supply at the Philadelphia meet this Sunday (we were waiting for the unpainted case to be pulled off the line and shipped over to announce, but oh well). The final version (basically, when the painted cases arrive, as long as they're all good) will be announced, along with date of availability and price, very soon. And for those who already own a MicroZOTL2, we'll certainly be letting you know our appreciation in our release pricing.

Cool, tight schedule Sunday, could jump out but I have to go to a heavy metal concert with my teen daughter (getting ready to surf the crowd...), (Breaking Benjamin and Starset), maybe I can get out early and get back on time, maybe not, the info will be appreciated anyway, thanks.

 

[jcx]

the "ZOTL" is an amusing misdirection - or even a lie
 
there are transformers in each output, clearly seen in the photos, detailed in the patent
 
they are however ferrite pot core high frequency transformers being fed audio (plate V ?) chopped way above audio (250 kHz according to the op text) just like switching power supply transformers that Audiophiles are often suspicious of
 
you can also see the pot core for the step-up switching power supply too - for a total of 3 transformers in the box, solid state switches. high frequency switching all over the place in that box, "in the signal path" even, and the internal wire bundles not even twisted/shielded
 
it is an interesting technological approach to an engineer - I find it amusing that it violates so many Audiophile Memes, seems to get a pass on novelty, perhaps ignorance of what the circuit actually does
 
I would love to think it were only being rated on literal "sound" - but I personally really doubt it when reading so much typical Audiophile hype - much echoing the marketing, not reflecting on the tech that would otherwise be expected to be anathema to Audiophiles, especially vacuum tube fans
 
even on just vacuum tube amp topology grounds push-pull lacks the mystique of SET too - might as well just go for accuracy, literal "hi fidelity" - which SS does cheaper, and much cleaner than adding 250 kHz switching converters in series with the outputs
 
while SET may well have "tasty" distortions, push-pull cancels the even harmonics, reducing "tube character", in fact Carver tweaked one of his SS power amps for full sized loudspeakers to match a more expensive "Audiophile respected" push-pull tube amp - to Stereophile's "Golden Ears" - in their own offices, their selection of music, speakers...
http://www.stereophile.com/content/carver-challenge#cLxahGobkx87V301.97

 

[willsw]

Did a little tube swapping on the 6SN7 variants...not a lot as I don't have the complete collection of every 6SN7 ever made like I used to in the past.... 

 
Let us know which tubes you end up preferring. We're always interested in what can make the MicroZOTL2.0 sound better.  

 

[jelt2359]

  the "ZOTL" is an amusing misdirection - or even a lie
 
there are transformers in each output, clearly seen in the photos, detailed in the patent
 
they are however ferrite pot core high frequency transformers being fed audio (plate V ?) chopped way above audio (250 kHz according to the op text) just like switching power supply transformers that Audiophiles are often suspicious of
 
you can also see the pot core for the step-up switching power supply too - for a total of 3 transformers in the box, solid state switches. high frequency switching all over the place in that box, "in the signal path" even, and the internal wire bundles not even twisted/shielded
 
it is an interesting technological approach to an engineer - I find it amusing that it violates so many Audiophile Memes, seems to get a pass on novelty, perhaps ignorance of what the circuit actually does
 
I would love to think it were only being rated on literal "sound" - but I personally really doubt it when reading so much typical Audiophile hype - much echoing the marketing, not reflecting on the tech that would otherwise be expected to be anathema to Audiophiles, especially vacuum tube fans
 
even on just vacuum tube amp topology grounds push-pull lacks the mystique of SET too - might as well just go for accuracy, literal "hi fidelity" - which SS does cheaper, and much cleaner than adding 250 kHz switching converters in series with the outputs
 
while SET may well have "tasty" distortions, push-pull cancels the even harmonics, reducing "tube character", in fact Carver tweaked one of his SS power amps for full sized loudspeakers to match a more expensive "Audiophile respected" push-pull tube amp - to Stereophile's "Golden Ears" - in their own offices, their selection of music, speakers...
http://www.stereophile.com/content/carver-challenge#cLxahGobkx87V301.97

 
Can you share a bit more about your understanding of the ZOTL tech? I must admit that I do not understand any of the current explanations about the unique approach employed in the ZOTL, and how it differs from OTL, vs traditional transformer-coupled amps.