Massdrop THX AAA 789 ending shortly. First measurement posted.

[Rod]

OK I fell happy about me decision again.

 

[FunctionalDoc]

I bought one since I heard a version of this at the THX booth last year at RMAF and it was very good in my short listening times on several headphones they had at the booth.

Jimster got in on this drop also. I plan using this amp with DX7 as the DAC for my ultimate solid state headphone rig.

I was impressed talking with one of the THX application engineers and this tiny circuit in acrylic box with detached power supply easily and quite well a HD800 's and other planar headphones with ease.
I have HE400i 's, Aeon's closed and ZMF Teak Auteur's so need wide application of power and impedance drivability.

Let he wait begin.

 

[Sythrix]

I bought one since I heard a version of this at the THX booth last year at RMAF and it was very good in my short listening times on several headphones they had at the booth.

Jimster got in on this drop also. I plan using this amp with DX7 as the DAC for my ultimate solid state headphone rig.

I was impressed talking with one of the THX application engineers and this tiny circuit in acrylic box with detached power supply easily and quite well a HD800 's and other planar headphones with ease.
I have HE400i 's, Aeon's closed and ZMF Teak Auteur's so need wide application of power and impedance drivability.

Let the wait begin.

I was at RMAF and somehow I completely missed it. Must have been a prototype showoff? Guess I was preoccupied with IEMs around that time. Didn't spend enough time checking out the amps.

Pretty sure they would have sold out if they had made sure some reviews went up. Hoping that wait isn't quite as long as it first appears. I am usually against joining drops this far down the line, but this is one I got pulled in on. Looks like new tech and not just another circuit shuffle like you often see. Hope it pays off.

 

[Rod]

So three of us so far. yes the wait begins.

 

[mindbomb]

Oh, I just noticed it is at 300 ohms. It will produce more distortion at lower impedance loads.

Assuming 5.5 volt is the output, that represents 0.1 watts of power. So not much.

When atomicbob measured the schiit jotunheim (which is a competitor to this massdrop amp), he did his tests at 0dbu, or 0.775 volt, .002 watts.

 

[amirm]

When atomicbob measured the schiit jotunheim (which is a competitor to this massdrop amp), he did his tests at 0dbu, or 0.775 volt, .002 watts.

I am not seeing the value of measuring an amplifier at such low output. Am I missing something?

 

[mindbomb]

I am not seeing the value of measuring an amplifier at such low output. Am I missing something?

I just thought it was interesting to bring up since you thought 5.5v was conservative. But yea, 0.775v seemed oddly low to me as well.

But idk, the average headphone is around 100db/mw. So peak power in the tens of milliwatts is what I think what people need. The trend of 1w+ headphone amps is perplexing to me.

 

[readysetgo]

I am not seeing the value of measuring an amplifier at such low output. Am I missing something?

abob... he just measured the cavalli, and then tried to defend the poor SNR which was way under spec. Then he claimed the guy was one of your minions.

https://www.massdrop.com/buy/massdrop-x-alex-cavalli-cth-tube-hybrid-amp/talk/2019953

I bought it to stack with the THX for aesthetic purposes so I never cared, but it should be fun to measure

 

[RayDunzl]

I am not seeing the value of measuring an amplifier at such low output. Am I missing something?

While measuring amplifiers at their maximum is of value, it would seem they are rarely used in that mode.

Suggestion for amusement when you have nothing better to do:

Listen to some loud recording at your comfortably loud level on your favorite or even each of your (maybe not the Stax) headphones, then report on what voltage (etc) a 0dBfs input signal produces at the headphone jack, vs the jack maximum.

Maybe repeat at a comfortably soft level. I tend to keep turning the volume down when I do headphones in a quiet environment.

---

Right now listening to talk radio via the DAC2 (with factory set internal jumpers) at -24dB applied to the signal entering the DAC.



Guestimation:

DAC2 HGC Output Level Range: (at 0 dBFS) into 60-Ohm Load Off to +17 dBu

+17dBu = 5.48Vrms

Drop by 24db = 5.28 x 0.063096 = 0.33Vrms listening level on my 300-Ohm phones (maybe)

---

Changed HDRadio (digital) source to obscure WMNF Rhythm Revival, same level is good.

---

Headphone Sensitivity - 103 dB at 1V RMS at 1 kHz (maybe)

 

[Sythrix]

The trend of 1w+ headphone amps is perplexing to me.

I think it's mostly because of the notion of hard to drive planars and also the vast capability of planars to accept such high wattages that has caused the trend.

Nevermind you'd probably go deaf trying to actually listen at those levels...

 

[RayDunzl]

Nevermind you'd probably go deaf trying to actually listen at those levels...

Changed above to 0dB (momentarily), way too loud for me...

 

[amirm]

abob... he just measured the cavalli, and then tried to defend the poor SNR which was way under spec. Then he claimed the guy was one of your minions.

https://www.massdrop.com/buy/massdrop-x-alex-cavalli-cth-tube-hybrid-amp/talk/2019953

Wow, what terrible way to interact with you. It is not like you misunderstood his data yet he keeps saying you don't know about measurements.

BTW, I have the same Agilent/Keysight linear power supply he has. I prefer to NOT use it because it produces more noise/mains leakage then my old fashioned bench linear power supplies.

Anyway, someone is supposed to lend me a CTH so I will be able to measure it and report back. As it is, I don't have 1% of the patience needed to read through the thousand charts abob has put out there, obfuscating any conclusion one can draw. That, and low contrast graphs kill me.

 

[amirm]

While measuring amplifiers at their maximum is of value, it would seem they are rarely used in that mode.

I am not asking for maximum. As you have seen, I provide a full graph at all all values.

 

[readysetgo]

Wow, what terrible way to interact with you.

That's not me, I feel bad for him. I'm the person lending you the CTH, just let me know when

 

[amirm]

Will do.

 

[RayDunzl]

I am not asking for maximum. As you have seen, I provide a full graph at all all values.

Well, I'm blind...

Now that I've been admonished, there is a power sweep of distortion% from nothing to clipping on a newer test.

Could you show a distortion spectrum (usually shown at max) at lower output power levels as well?

Just curious...

 

[amirm]

Could you show a distortion spectrum (usually shown at max) at lower output levels as well?

How much lower?

 

[RayDunzl]

How much lower?

For me, and my phones, it looks like I'm happy at a milliwatt or three...

For others, and their phones, I don't know.

Maybe just show a spectrum around the sweet spot of their power/distortion sweep, which, in this case, corresponds well to the power level at which I might listen:

Just curious, I can't accurately measure this stuff at all here.

I'm probably happy with just an example.

 

[mindbomb]

I have a question. How would you convert the headfi thd measurement (which I guess is .00003%) into thd+n?

 

[junki]

As long as measurement settings are consistent from one measurement to another, that's the most important thing. @amirm can measure everything at 5.5 Vrms into C ohm if he just stays consistent with it so we can compare apples to apples. Two arguments for setting that consistent level down are:

1. Most people don't listen at 5.5 Vrms, but knowing maximum THD+N characteristics at maximum output and gain is academically interesting.
2. The maximum output of different amps are different.
3. Many published specs show metrics @ 1 Vrms. Those who also show specs at maximum output have balls.

Btw, I'm the guy in that MCTH thread. I'm obviously no one's minion and am using my own mind and judgement to editorialize information I get here and elsewhere, objective or subjective, for the optimization of my own purchases.

But to vent, I'm about = this close to quitting this hobby because there are literally just mean, pretentious, fucking stupid as fuck cliquey circlejerks everywhere I go. All I want is some goddamn honest-to-self subjective impressions coupled with consistently measured, holistic measurements with honest insights into both the good and bad. If there was only a goddamn website that did that, it'd be the best. Oh wait, InnerFidelity's got the headphone part of the market cornered. Open season for DAC/amps...