Moon Audio Luna

[postjack]

Lets talk about the Moon Audio Luna, a headphone amplifier.

All of the pictures, features, available model information, and specifications were taken from the Moon Audio website.

The Moon Audio Luna headphone amplifier marries the resolving power of vacuum tubes to the very highest quality audio transformers to bring nuanced, dynamic sound to headphones. The Luna has been designed to minimize audible (as opposed to measured) distortion and allow the subtle details and dynamic contrasts of recorded music to pass unaltered to your headphones. The Moon Audio Luna uses vacuum tubes and Lundahl audio transformers to achieve the goal of giving you all of the music!

Features:

-Completely transformer / direct-coupled tube amplifying stages

-Lundahl audio transformers throughout

-Two stage Class A differential circuitry

-Low impedance vacuum tube rectified choke regulated power supply

-Unique amplifier balance controls to accommodate ?tube rolling? and retain optimum amplifier performance

-One balanced (XLR) and two unbalanced (RCA) inputs.

-Two front panel Neutrik Combo jacks for either two ?? plug equipped headphones or one stereo XLR cabled headphone compatible with virtually all headphones.

-One balanced (XLR) and one unbalanced (RCA) back panel outputs for line stage preamplifier use.

Available Models:

The Standard model uses high grade audiophile parts to achieve an excellent result.

Price: $2200

The XL model adds the following exceptional quality parts for the ultimate in reproduction:

Black Gate power supply capacitors

Lundahl iron amorphous core output transformers and higher signal level cobalt amorphous core input transformers

DACT discrete resistor stepped volume control

Silver plated fuse holder and AC input connectors

Ohno continuous cast 6 nines copper wire

Price: $3000

The XL model with Penny and Giles conductive film pot with 24k gold wipers

Price: $3300

Specifications:

Gain: 15dB

Frequency response: -0.5dB @ 20Hz, -0.3dB @ 20KHz, at 1 volt output, 1KHz

Output impedance: 16 ohms

Tube complement: 2 x 6N23P/6DJ8/6922/ECC88/7308 2 x 6H30Pi 1 x 6BW4

Power requirements: 120VAC 0.5A or 230VAC 0.315A

Dimensions: 14? wide by 14? deep by 4? high

Weight: 16 lbs. (7kg)

So basically this looks like it could be the answer for folks like myself who love Grados and other low impedance phones.

I'm curious as to what the big brains around here think not only about the amp in general, but also about the different models. Also what is a Penny & Giles conductive film pot?

EDIT: the Luna uses 6DJ8/6922 tubes, like the Melos.

[n_maher]

Honestly, my first (and really only) criticism of the amp is its use of a stepped attenuator. Using low impedance cans I'd be pretty nervous only having 24 steps. And the Penny &Giles pot isn't' a cheap option at $500 (figure -$200 for the dact, +$300 for the P&G).

[postjack]

Just received Roam's permission to repost his impressions he sent me via PM:

"Indeed it is, I haven't had it for very long, though impressions to date have been good. Mine is the standard base model, I'm using Mullard E88CC tubes on the input and the stock output & rectifier tubes.

Keep in mind that my Grados are extensively modified, Pt-Ir cables, EnABL treatment of drivers & housing, rounding off all sharp corners & edges, damping of various structural parts, etc. They retain the basic character of their stock counterparts, but with much greater resolution and ability to extract low-level details.

With that out of the way, the Luna does not really do anything wrong, and that's about the highest compliment I can pay to any component. The frequency response is excellent, flat, wide bandwidth with no roll-offs. Most tube amps fail here already. There is no real colouration beyond the sound of whichever 6DJ8/6922 is being used. I can hear the Lundahl transformer sound, though I suspect the vast majority of people won't notice it at all. I'm very familiar with the sounds of various audio transformers so I recognize these things, but again, most people won't even know it's there.

What it does better than every other commercially available tube amp I've heard is control, especially in the bass & midrange, along with freedom from the overly syrupy & rich midrange of many tube amps. Most tube amps lose control in the bass, especially with low impedance Grados, textures & details are smeared out and notes lose definition. The Luna doesn't do this, or rather, the degree is an order of magnitude lower than the norm, though still not up the lofty standards set by my custom amps. Same idea with the midrange, it's quite clean and is almost free from the usual tube colouration, though it still retains a distinct tube sound.

The tube sound is the way it should be, that is, one of ease, liquidity, and freedom from grain and harshness. Detailed textured bass, expressive mids, and sweet highs, along with good dynamics and drive. It is not the bloomy bloated crap which passes for "tube sound" these days.

One warning though, do not expect to be impressed by the amp on first listen. It's not a "wow" amp, there's nothing which will really step out and grab you. Rather, it's an amp which will grow on you, as you go through you music you'll start hearing new things in new ways, and that's when you'll start realizing how good it is. All those transformers also take a long time to break in and sound their best, give it a good week or so of solid play for best results. Use the cheap tubes during this time so you don't burn hours off your good 6DJ8/6922 tubes.

This is one of the very few commercially available tube amps which I feel comfortable recommending to others. The design is technically solid, and it sounds good too."

[philodox]

It was my favourite amp at the first national with my K340s.

Also, you could try the 6BQ7A/6BZ7 in place of the 6922 as it is basically just a higher gain, cheaper, and some say better sounding version of that tube.

Not sure about the Luna, as I didn't try it with Grados, but my amp is just fine with Grados and K340's and only has 24 steps.

[aerius]

Also, you could try the 6BQ7A/6BZ7 in place of the 6922 as it is basically just a higher gain, cheaper, and some say better sounding version of that tube.

Electrically, the 6BZ7 is nowhere close to a 6922 except in gain. Half the transconductance, twice the plate resistance, a bit more gain. Given that the input & output tubes are direct coupled, I wouldn't drop in a 6BZ7 without seeing the full schematics of the amp.

[philodox]

oops, sorry for the bad advice, someone told me they were very similar at some point.

[philodox]

It is quite possible I am getting the 6922 confused with another tube.

[aerius]

Honestly, my first (and really only) criticism of the amp is its use of a stepped attenuator. Using low impedance cans I'd be pretty nervous only having 24 steps.

My math could be wrong, but a gain of 15dB works out to a gain of 5.6 or so, so it's not all that high. I think could get away with using a stepper with only 24 steps, or if worse comes to worst you could swap in different transformers to drop the gain.

[n_maher]

My math could be wrong, but a gain of 15dB works out to a gain of 5.6 or so, so it's not all that high. I think could get away with using a stepper with only 24 steps, or if worse comes to worst you could swap in different transformers to drop the gain.

I agree, with the gain that low 24 steps should be ok, it would somewhat depend on your source output level but odds are it'd be alright.

[NotoriousBIG_PJ]

Ding ding ding, Roam is Aerius's chick friend? ^^

Biggie.

[Nanoha]

Ding ding ding, Roam is Aerius's chick friend? ^^

Biggie.

Uhm.

[JBLoudG20]

But I though Aerius likes little boys?

[aerius]

Ding ding ding, Roam is Aerius's chick friend? ^^

Biggie.

Nope. She doesn't have a turntable and she ain't got those speakers. Plus she hangs around on diyaudio, not head-fi, cause the latter rots your brain.

[NotoriousBIG_PJ]

Ok, so they both have recabled grados with enable process and rounded off edges, and both own the same source and both have custom dht amps for grados. But, they arn't the same person.

Biggie.

[JBLoudG20]

ROFL.

[PFKMan23]

ROFLCOPTER

[JBLoudG20]

lolerskates

[humanflyz]

.......................__ ............

......<ROFL ROFL ROFL ROFL>.

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..\ \_...........|--|---|..\\ ....\....

../ L \____,/-------\___\___\

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.//.............____//___ __\\__/.

[ojnihs]

hahaha

[philodox]

Yeah, totally the same person.

Either that or Roam and Aerius' girly friend both know eachother and one is copying the other.

[Nanoha]

But from what I understand, Roam is a guy? Weird...

[hungrych]

"Rounding off sharp edges"? What would that do?