[KevinW]

The holy grail of energy efficiency in amplifiers is Class D.  "normal" solid state and tubes just cannot even come close.  My product lineup really needs a digital amp, and I've been working hard with Jena Labs to develop one.

Here's a breadboard version which I just wired up this morning. Note the audiophile quality plank of wood, and aluminum angle bracket.



It uses the LC Audio digital modules distributed in the USA by DIY Cable. These little modules are really slick!  The size of a credit card, they can do 250 watts into 8 ohms no problem.  I've got them running at 125 watts/ch, and they won't draw more than 10 watts each on my power meter, for a 92% efficiency rating.

Oh yeah... I get so excited about efficency, that I forgot to metion the sound.  Well it's astoundingly good, to say the least.  Very dynamic with outstanding bass control... digital amps are where it's at if you like good bass.  Detail and resolution are also extremely good.  The soundstage is particularly vivid and deep.

But the sound quality performance that I most care about is the tube-like sound.  There's just no comparison between tubes and solid state as far as a warm, lush, musically involving sound.  Digital amps have the potential of equaling tubes in this regard, because they are not prone to a particularly viscious kind of harmonic distortion inherent to solid state analog amps.  At this early stage, this amp has the beginnings of a good tube amp sound, but with extreme detail and bass control that is commonly lacking from tube amps.  

In comparing the sound of this prototype with my ASL Tulip w/ Level 2 mods (a 3.5 SET stereo amp).  The digital amp is not quite as musically involving as the Tulip.  But the Tulip can literally turn your bones to jelly as you sink into its warm, lush musical presentation...  In detail and soundstage ability, the amps are about equal.  Regarding the ability to drive regular efficiency speakers, the digital amp kills the Tulip.  The Tulip also consumes 70 watts of power, compared to 20 watts on the digital.

In short, the early results are very encouraging, and there are still a lot of tricks up our sleeves. The finished product could be a hit at VSAC  

[JLM]

Good luck with the amp Kevin.  

Is this a good time to offer wish list sort of suggestions?

Keep the cabinet simple (save money and the planet's resources).  Doesn't have to look like a boat anchor, but painted black is O.K.  Doesn't need LCD displays or power meters.

Keep it honest (let form follow function).  Does a power amp need a laser engraved 3/4 inch thick faceplate?  Or be 17 inches wide and filled mostly with air just to look impressive?

Also offer a lower wattage version (save cost, size, power, natural resources).  The high efficiency speaker folks don't need more than 20 wpc.  IMO only offer two sizes, 20 wpc and 200 wpc.  That should satisfy 98% of the market.  (I tire of people wanting 200 wpc versus 100 wpc when it's only a 3 dB of gain, half again as loud, difference.)

Offer them as monoblocks (for the HT and audio to HT migration).  Would also help channel separation.

Keep content value high (perhaps this is more of a need to educate the consumer).  As with your speakers, it's not easy to convince consumers why single driver speakers should cost $1,000 each.  If the "guts" of a digital amp is a $5 chip, why should it cost ???  A DIYer's recent release of a digital amp to the retail market was accompanied with a statement from him on open forum that his $1,800 amp had $60 in parts, mostly in the gold volume knobs.  Now that's a turn-off!

Build in easy servicing (diagnostics port, modular construction, don't over cram components into the cabinet or connecters onto the rear panel).  If a power switch is offered, locate it on the front and keep all the plugs in the back.  Use an IEC plug for swapping out power cords.

Offer options (package deals, upgrade specials, cabinet damping, replacement feet, isolation pads).  But don't upgrade the guts every few months (especially if production lags behind product release).

Post a list of recommended options and speaker match ups.

Have the amp (and all your offerings) professionally reviewed by Richard George (my favorite reviewer).

jeff

[KevinW]

JLM,
Thanks for the suggestions.  Now is definitely the time for anyone else to make suggestions, as I will be designing the different levels of amps and pricing them out in the next couple of days.

I will be producing three levels of amps.  One very simple amp in the $1-2k range.  One significantly improved amp with a vacuum tube input stage in the $2-3k range.  And one no holds barred amp in the $4-5k range.

Any opinions on the price range?  What would you be willing to pay for?

Power will be in the 100 watt to 250 watt range.  With the digital amps, the same modules produce the power, it's only the transformer that makes a difference.  So it's not that much cheaper to do a lower powered version.

The amps will use the same chassis, and there will be upgrade options from the lower to the higher levels.

What do people think about an integrated vs. a stereo power amp?  Which would be more attractive?

Monoblocks are not necessary at all sonicly, as there is very good separation between channels, and I have learned a few tricks to effectively completely separate the channels.  However, some people may want drop-in replacements for their existing monoblocks.  How strongly do people feel about monoblocks?

[KevinW]

Break-in on the prototypes above has produced stunning results.  The emotional inolvement factor is going way up, as vocals have become smooth and liquid, and with a palpable presence that wasn't there initially.  It's starting to sound more SET-like, but with PLENTY of power to spare.

Very encouraging results, especially considering that Jena Labs and I are working on several new features designed to increase the SET-like factor.  This could be a winner, even for the die-hard SET lovers.

[sica]

Kevin, I am interested in this amp because I want something that is musically involving.   I think the upgrade option is great, very thoughtful of you.
To answer your questions:
I would want something between $1000 to $1500.
Integrated would be great, but I understand everyone has different needs.

Is this prototype the one that will be about $1000?

[JoshK]

Kevin,

When you say integrated, do you mean analog inputs, with an analog pre section with the amp converting A/D?  Or do you mean digital input with digital volume control like the soon to be released Spectron or Tact offerings?  

I really like the idea of monoblocks, for if no other reason than modularity, but I guess stereo amps can be modular too especially when the mono's wouldn't be much less expensive to make than the stereos would be likely, since the rest of the parts are $$$.

[KevinW]

Sica,
I am still working out  price options... but the level one amp will look very similar to this prototype.  In other words, it will not have a tube input stage, but there will be room for an upgrade to tubes later on.  There will be several different upgrades to level 2 (or perhaps the "Deuterium" level ), which can be installed in mix-and-match format.  The target is to get the base price under $1500, and as close to $1000 and still be able to make money.  The level 2 will be in the $3k range, and be able to absolutely destroy the competition.

[sica]

Kevin, are you using your Solar 1.0 speakers to test this amp?

[KevinW]

I am using the Solar 1.0 speakers primarily because they sound so good, and are so completely transparent and uncolored from the midbass on up.  

To test the low bass, I have a pair of Acoustic Reality Tetra's.  Remember those?  A tall pyramidal speaker, with scanspeak reveletor 6.5" woofer and 9700 tweeter.  This is a very high quality representation of a 2-way ported speaker design.  The Fusion can really pound out the bass, no matter how much rap or reggae I throw at it.  

But the Solar 1.0 just totally slays the Tetra in sound quality.  I'm waiting for people to hear how good this speaker really is compared to everything else in the price range.  When you hear just how many veils are lifted from the music, the compromise of needing a sub for low bass is just not a big deal.  But since most acoustic bass is comprised of harmonics above 60Hz, the Solar 1.0 has the most natural sound when blended with the sub.

[JLM]

Kevin, this is off topic but you opened the door...

What sub do you recommend with the Solar 1.0's?

jeff

[KevinW]

Kevin, this is off topic but you opened the door...

What sub do you recommend with the Solar 1.0's?

jeff

Any sealed sub will work well, because the transmission line rolls off very smooth. I personally am quite happy with the Adire Daeva. It uses the Tempest 15" driver, and is very tight and musical. Even better it uses a 300 watt class D amp, which is 90% efficient and has very good control of the woofer.  Why not go all the way Class D on the main power amp, and the subwoofer amp?

The Daeva costs $599. For a little less money, the Rava sounds just as good, but only plays down to 30Hz for $399.

I would not recommend a ported sub at all.  Passive radiator subs could be okay, but are not as musical as a sealed sub.

[KevinW]

Kevin,

When you say integrated, do you mean analog inputs, with an analog pre section with the amp converting A/D?  Or do you mean digital input with digital volume control like the soon to be released Spectron or Tact offerings?  

Thanks for your question, Josh.  I'm glad someone brought it up, as this is a very confusing point for many consumers.

It's not very easy to run a Class D amp from a digital signal, because the frequencies of the two formats are radically different.  CD players emit roughly 44 kHz, while the LC Audio modules run at 500 kHz.  It is possible to do a direct conversion of frequencies entirely in the digital domain, but this produces lots of messy errors and ends up sounding very bad.  Even though it seems illogical, it is far better to use a separate DAC to convert to analog and then let the amp module convert back to digital.  Modern DAC chips are very sophisticated and sound so good because of the many years of effort to improve their performance.

There's a reason why the big Class D amp manufacturers have been slow in releasing a direct digital connection... it's not easy to make it sound good.  In fact, I half-suspect that there's simply an internal DAC in those future offerings.  I think the customer will be better served by being able to use their own DAC of choice.

However, I will offer direct digital input when SACD digital input parts are available.  This makes sense because SACD samples at 2.8 MHz, which would be fed directly into a capable Class D module.  This could sound REALLY GOOD. Don't hold your breath on this one though, as it could be a couple of years before parts are available to even make this possible for any corporation not named "Sony".

In the meantime, the integrated will have 3 or 4 analog inputs and a volume control. Probably a Dact, since anything less wouldn't do the sound justice.

[KevinW]

Oh Yeah!!!

Implemented the first of three major circuit additions to the basic amp module, and I am flat out stunned with the results.  Blown away, falling over laughing at how good it sounds.  The music is so natural, clear and alive.  In fact, it kills my SET now.  The emotional impact and involvement are the best I have ever heard, while retaining the picture perfect detail and accuracy of the best SS amps, with plenty of power to spare.

I wish I could say what we did, but this circuit was designed by Jena Labs and myself, and is intellectual property.  I really did not expect the simplest of the three circuits to make such a huge difference.  This is going to make the base model of the amp represent incredible value for the money.  I am really excited by this!  I like nothing more than delivering a superior product at a superior price.

Later today, Jena Labs is coming over to try overclocking the modules up to 1Mhz, and we're starting work on the vacuum tube input stage next week.

I'm also working on the price options.  The goal is to have the base model be under $1500, with various upgrade options.

[Hantra]

I cannot WAIT to hear this!

B

[Sa-dono]

I cannot WAIT to hear this!

B

I'm highly interested as well. Any chance we can get a nice looking chassis? Maybe some pics when they're available as well?

[KevinW]

A nice looking chassis is what you want?

What do you think of this?  




These little beauties are made by IAG Audio (www.iagaudio.com).  Highly recommend for DIY too. I used this same chassis to make a TS Grounded Grid preamp several years ago.  Very solid and thick machined aluminum.  Very nice polish.  I'll be having the holes for switches, jacks, etc. laser cut, and the labeling laser engraved.  I'll also be replacing the wood sides with some very nice looking bamboo plywood.  



The bamboo comes in four flavors, natural and carmelized color, and horizontal and vertical grain.  The purchaser can pick the style of the bamboo.

ps.  I thought about making the chassis into a semi-dodecahedron shape, just to one-up a certain other Class D amp maker whom we old-timers all know and love.  But in the end, I decided that the practicality of a simple rectagon is more important.  

[Sa-dono]

A nice looking chassis is what you want?

What do you think of this?  

Looks pretty good. I'm going to need to see one with the bamboo sides first though. I think darker finishes will end up looking better, but the lighter ones will fit my setup better....unless you make a gloss black version.

ps. I thought about making the chassis into a semi-dodecahedron shape, just to one-up a certain other Class D amp maker whom we old-timers all know and love. But in the end, I decided that the practicality of a simple rectagon is more important.

Too funny!

[JLM]

Bamboo laminated flooring now is available (like Pergo).  You can see flat grain, clear finish at Lowes, etc.

BTW bamboo (or light maple) and natural cherry go incredibly well together!

jeff

[JLM]

Kevin:

How's your knee after surgery?

Please update your work on the amp!!  Are you still shooting for a minimum of 100 wpc?  

Please post the size of the Solar 1's.  

Seems like the Solar 1's aught to play lower than the 60 Hz you specify since the driver itself is rated lower and the cabinet provides transmission line loading (which extends bass response).  I know you don't want to get into futzing with specifications, but could you explain?  I'd guess it should be good down to around 35 - 40 Hz (in room).  This is an important consideration for the concept of the product to be valid as a single driver, full range speaker.  Below 35 - 40 Hz. a powered sub is best IMO to be able to taylor the response to the room and/or listener taste.

I'm a SET/high efficiency speaker fan.  Does the pairing of the Solar 1's with the new amp have the dynamic magic I love?  Is that where you need a sub, to help with higher spl's in the 35 to 60 Hz range?

(For some reason the Adire site keeps coming up blank on the Daeva page.)  

thanks,

jeff

[KevinW]

Kevin:

How's your knee after surgery?

Please update your work on the amp!!  Are you still shooting for a minimum of 100 wpc?  

My knee is recovering pretty quick, thanks for asking.  It's not too painful.  Still walking with a slight limp and it should be fully healed in about month.  I can't wait to get active again, especially now that the rainy season is almost here.

The amp progress is real, but ya know what?  There's a lot of steps and decisions that go into a production quality amp!  The first chassis is going out to the laser cutters and then the laser engravers this week.  I expect to receive the final parts this week, including the power transformers.  Final power depends entirely upon the voltage of the transformer, but it should be between 220 watts to 250 watts into eight ohms.  Four ohms is double the power.  Because the amp is so efficient, a lower powered amp would only reduce a few dollars off the final price.

The tube stage should be ready by next week, and the finished product is still on target for VSAC.

The question about the Solar 1.0's I'll answer in a new thread.