Leaf Audio PA-03 MKII Review (Tube Preampifier)

[SIY]

I wish I understood what you meant by "cut-and-paste pseudo-SRPP" but in any case it's clearly a inexcusable piece of junk.

Amir comments that seems to be a clone of the Audio Research LS22. Notwithstanding that ARC's isn't necessarily aiming for lowest possible distortion, I doubt that the authentic design is such a travesty. The LS22 looks to me to be a fully balanced/differential design which Leaf Audio PA-03 MKII device might not be (?). (The LS22 uses eight tubes where as the Leaf uses only for per the internal picture shown by Amir.

Looking at the internal picture, it looks like some effort and care has gone into the construction of the unit -- apart from possible cheap Chinese clones/counterfeits of quality components. Too bad the result is such a failure.

I would really look forward to the findings of you hands-on examination of the Leaf if that can indeed happen.

LS22 has far better performance. There is a sad tendency among Chinese manufacturers of tube gear to try to ride the trademarks and brand names of others. I’ve personally seen at least a dozen preamps claiming to be Marantz 7 clones. They’re not, and truth be told, the Marantzes were nothing special, the value of the brand name notwithstanding.

If you want to learn about SRPP circuits and how crappy implementations are done, poke around a bit for Merlin Blencoe’s paper about it. I’d link you, but I’m on my phone and searching is painful.

 

[JDS]

Theyre trying to look like LUXMAN . At least that part they got right LOL

Luxman up front, Parasound around back. An audio mullet?

 

[misureaudio]

A clear disaster. May be I wasn't attentive enough, but I couldn't find the load it was asked to drive. The LS22 was decent just at (very) high load impedances. It was a disaster when asked driving a 600 Ohm load, clearly an out of reach (and specifications) target.

 

[dfuller]

If you want to learn about SRPP circuits and how crappy implementations are done, poke around a bit for Merlin Blencoe’s paper about it. I’d link you, but I’m on my phone and searching is painful.

Allow me:

http://www.valvewizard.co.uk/SRPP_Blencowe.pdf

 

[GWolfman]

The audio historians need to chime in and educate the rest of us on why that is prized enough to be cloned.

Lol

 

[Gorgonzola]

LS22 has far better performance. There is a sad tendency among Chinese manufacturers of tube gear to try to ride the trademarks and brand names of others. I’ve personally seen at least a dozen preamps claiming to be Marantz 7 clones. They’re not, and truth be told, the Marantzes were nothing special, the value of the brand name notwithstanding.

If you want to learn about SRPP circuits and how crappy implementations are done, poke around a bit for Merlin Blencoe’s paper about it. I’d link you, but I’m on my phone and searching is painful.

Thanks and don't worry about the Blencoe link -- I wouldn't understand it anyway.

I did discover these discussions of SRPP at Tubecad.com-1 and Tubecad.com-3; (I don't understand them either).

 

[Balle Clorin]

I know unity gain is som kind of standard here but, It is quite uninteresting to test this unit at 4 volt in in and 4 volts out. No one will have to run it that way .

A CD will be about max 2 volts in and the power amps often require no more than 1volt in. 4-4 volt is never going to happen in real life.
It would be useful to see how it performs then under more normal loads and input The input stage is obviously clipping the way the test was done

 

[tomtoo]

Even with all the manufacturing muscle of China -- even if many "audiophile" parts are counterfeit -- hard to understand how this thing can be sold for less than $1000.

Good question. I look at it, see the efford, and ask my self, how can this be so cheap?

But that makes me sad. Couse would all this efford go in the right direction, it would be a great product.

 

[thefsb]

. It is on kind loan from a member.

Has that owner owned up yet?

 

[gonzoucab]

Has that owner owned up yet?

im a decorator

 

[thefsb]

I See it clear now, im not an audiophile

Audiophilia doesn't necessarily imply devotion to fidelity so I don't see why not. You just love a just different kind of audio. As do a lot of musicians.

Does anyone have a schematic? This might be easy to fix, depending on what they've done. Just looking at the results, it suggests they did the same cut-and-paste pseudo-SRPP that seems to be mandatory in any tube equipment coming out of China.

Don't do it!

 

[magicscreen]

You should not use/measure it at maximum volume. It is a preamp.

 

[AdamG]

Perfect example of “Dead if you do and dead if you don’t”. Amir presents Objective data only and we get bitching and complaining that he didn’t actually listen to it and give his Subjective Observations! Just can’t win. But this thread is a timely example of the frustration Amir must deal with about damn near every review.

 

[zepplock]

Its like asking how many milligramms of cow shiit you have to insert into your food until you taste it? I dont know? I just not see why it should be in there?

Best analogy ever!

 

[tomtoo]

Perfect example of “Dead if you do and dead if you don’t”. Amir presents Objective data only and we get bitching and complaining that he didn’t actually listen to it and give his Subjective Observations! Just can’t win. But this thread is a timely example of the frustration Amir must deal with about damn near every review.

@amirm is a hero. A hero for science and logic. 200 years ago he could easely end up in a torture chamber. Things got better. But still far away from good.

 

[DualTriode]

Does anyone have a schematic? This might be easy to fix, depending on what they've done. Just looking at the results, it suggests they did the same cut-and-paste pseudo-SRPP that seems to be mandatory in any tube equipment coming out of China.

Hello @SIY ,

You have designed some quality tube projects. You also have AP test gear on your bench. It would be really cool if you post some test plots of what tube equipment can do.

I did build a SET 12B4A tube headphone amplifier near the end of 2017 about the time when I drove to Oregon and picked up an APx555. Using a solid state shunt regulator power supply that cost more than the Single End Triode stage including the output transformer, for typical listening levels The 12B4A SET cleaned up pretty nice.

Thanks DT

 

[testp]

Finally!!! we see some new wave-form/shapes in the measurement graphs

too bad thats a miss, like those VU-s...

 

[amirm]

A CD will be about max 2 volts in and the power amps often require no more than 1volt in. 4-4 volt is never going to happen in real life.
It would be useful to see how it performs then under more normal loads and input The input stage is obviously clipping the way the test was done

2 volts for CD is for unbalanced output. It is 4 volts for balanced which 99% of the DACs I test produce. And balanced input is what I used for most of the testing. The unit has specific "DAC" input to it better not clip with nominal output from such devices.

Regardless, I specifically tested other levels. Did you not see that in the review???

At 12:00 o'clock position it output about 0.3 volt. At unity gain it is well below max volume at 4 volts instead of 15 volts. As you see, performance does not change and simply shifts with different volume positions.

 

[SIY]

Hello @SIY ,
You have designed some quality tube projects. You also have AP test gear on your bench. It would be really cool if you post some test plots of what tube equipment can do.

I did build a SET 12B4A tube headphone amplifier near the end of 2017 about the time when I drove to Oregon and picked up an APx555. Using a solid state shunt regulator power supply that cost more than the Single End Triode stage including the output transformer, for typical listening levels The 12B4A SET cleaned up pretty nice.

Thanks DT

The measurements of the Equal Opportunity pre are in the articles. Not AP, but a very good soundcard setup at that time. Ditto the HMN article. Now that we're out of Arizona and living in a rural place with cold winters, I'll be building more tube gear again, and will definitely include AP measurements in my write-ups.

 

[nyxnyxnyx]

I told it in a later post, with a pure 20Hz sin you can hear it. With music i dont know?
But i not see why i should do such an experiment? It adds something that should not be there. Its like asking how many milligramms of cow shiit you have to insert into your food until you taste it? I dont know? I just not see why it should be in there?

I think the general and accurate conclusion, at least in this community is that most tubes don't measure well and at the same time bad/mediocre measurements might not easily be reflected in normal listening conditions - and as far as I know even Amir did have positive subjective impressions with certain badly measured designs (under certain conditions).

My point is that we've been having subjective impressions/conclusions besides our pristine and accurate measurements for some time now and frankly we even have rankings now. Secondly, it actually contributes a lot of value to people that visit this site. Not everyone is primarily interested in the final measurement, they also want to know how it translates to listening experiences (might be the main reason why we now have more elaborated subjective impressions that we didn't have years ago? idk) - so why not continue to do that? For example, if the distortion is completely inaudible then great. But hey, if it's more or less the same in the first case but this time you can hear it loud and clear if you use a pure 20Hz sin or with some other specific conditions then it's another great discovery. Readers that are interested in this audio piece now have concrete information and they now can decide to do what they see fit with it!


Even if we go with your cow sh!t analogy I still think there's nothing that can be worsened if we have more information about a product in different angles - which is why I think milosz has a good suggestion because it can further remove bias of confirmation (if there is any).

And lastly, you say you don't see why you should do an experiment like that, with a device most people buy to play music (or maybe as a decorative piece...), but you'd rather do an experiment with 20Hz sin wave? I mean if we look at the facts, we already know it measures badly and is quite expensive. Nobody will try to deny that, it'd just be more helpful to know how it performs in the most realistic scenarios (which is playing music).