They just can't say it, can they?

[Chris A]

See some patterns?

Well said. Can the F3 be had for less than $500, and will it function without a DAC / Pre-Pro upstream?

No - not without building it yourself. The article on the NAD C390DD triggered me to come to this thread.

What is interesting to me is that it has taken so long for the audiophile community to come around to accepting what their ears have apparently been telling them for some time: it doesn't take $5-10K amplifiers to do it, but it does take some understanding of what you're looking for when selecting system components.

I've never been a proponent of component cost = quality. In fact, I actually pride myself in going the opposite way. but sometimes I've found some components that sound good also cost more than I wished them to be (speakers, for instance). That's the engineer in me. I'm always looking for a better/cheaper/easier to use/more reliable way. How it looks means little*.

Chris

*A little gift from my old man: he instilled a different way of evaluating audio components, that is, instead of the way that they look.

[ClaudeJ1]

A $200 chip amp can sound better than a $2,000 or $20,000 amp. With the right setup, equivalently mixed CD audio surpasses LP audio over a set of tubes, with less fuss and even less outlay. It's 2012...it can be done.

I was blown away the first time I heard one of those Sonic Impacts with the 2020 chip. Now I have some with the 2024 chip, which was rated in the top 10 most important IC's produced in the last century by Electronic Engineering Times magazine...........very prestigious.

I used the Sonic Impact to demo my Walnut Khorns to a buyer about 5 years ago. He was impressed. I brought the little sonic impact to Indy and one of the engineers tested it for me. It's 6 clean watts and I wish Paul W. Klipsch would have lived to see and hear it because he always said the world needed a good 5 watt amplifier. They have been here in the form of Tripath chips for a while now.

[DrWho]

What I want to see (and hear) are some really inexpensive "chip amps", with Class A SET sound quality, with the low-end power and command that a good solid state power amp has, AND has built-in variable steep slope filtering and time delay capability so three of them can be used to tri-power, say a Klipschorn with integrated power amplifiers.

Funny you should say that....as that's exactly what my old roommate and I accomplished several years ago. Basically we made a 2in-8out DSP feeding 8 class-D amplifiers. If you're starting with a digital source, then this is absolutely the best way to go (because then all the DSP is free). Unfortunately I can never find the time to actually turn it into a product.

One of the things we quickly learned is how each topology has its own set of quirks that need to be mitigated.

The chip amps are my least favorite - especially the ones with PCM input because they inherantly have horrible power supply rejection. This is why the power supplies for these amps can have such a large impact on the sonic signature. If you have a chip amp, then I would recommend going overkill on the power supply capacitance - like crazy overkill.

The performance of the fixed frequency designs is limited by the accuracy of the triangle wave used to create the "digital signal" - which you could think of as the reference for a single bit converter. In these designs, the "comparator source" is the limiting factor for distortion and it's honestly quite interesting how you can adjust the sonic signature with this stage. The more advanced topologies can use any variety of feedback topologies to dramatically improve power supply rejection, but then you've got another source for sonic signatures. You also run into weird beating problems and other totally random frequency artifacts....which Yamaha solved by throwing in a lot of PLL's. At the end of the day, to do a really really good fixed frequency class D amplifier, you need a ton of parts...and you basically end up building a sigma-delta converter that has enough oompf to drive a speaker.

The self-oscillating appraoch is my favorite because it uses the fewest parts and you're using the switching output as the comparator source.....so now all of your comparator source distortions are a direct function of the source material itself and it just sounds really good. The switching frequency also shifts in a way that is more conducive to lowering distortion. You also get almost perfect power supply rejection, and you don't have to worry about the typical feedback parasitics because you actually want the phase reversal to make it oscilate. Just like the fixed frequency topologies, the feedback and output stage topologies will affect the sonic signature. I think the biggest downside to the self-oscillating approach is that it is very difficult to make the amplifier robust to where a user won't easily blow it up. You also have the same beating issues as well.

Another distortion common to all Class D designs is the non-linear flux of the output inductor. It creates a distortion extremely simmilar to that of an output transformer for a tube amp, which is where I think much of the "tube-like" descriptions come from. This is where the Hypex amplifiers get interesting because there is an additional feedback chain after the inductor - which then allows you to correct those distortions out. Of course it doesn't sound like a tube amp either.

The self-oscillating design we liked the most wasn't taking the feedback after the output inductor, and there was some intentional tweaking to get the distortion harmonics to be predominantly second-order. It was kinda cool because we could shift the sonic signature from SET to Tube to SS simply by changing a few part values - we always joked about turning it into a knob control.

Btw, we did all blind listening when we were working on the project and it wasn't too difficult to discern differences. Sometimes it was hard, but then that just means the source material wasn't triggering the artifacts. And the flip side happened all the time too....we'd start chasing down some weird behavior only to learn that it was actually the source material itself.

This will probably come off the wrong way, but critical listening is something that is learned and requires very controlled conditions to even start learning to differentiate between various sounds. So when a DBT is conducted and no difference was apparently heard - either the source material wasn't triggering any of the artifacts, or the listener hasn't learned to identify / differentiate a certain artifact. Our acoustic memory is really poor so if you don't recognize something going in, then you just instantly attribute it to being part of the source material itself. That said, I don't believe in golden ears and I strongly believe that most of this stuff the vast majority of people can hear. I just think it's a misinterpretation of the facts when one makes the blanket claim of something not being audible in a DBT as if it could never be audible.

Anyways, enough rambling....hopefully this has worked to stir up the pot though because I do strongly feel Class D will be an ever growing topology.

[DrWho]

I came across this article from 2004 (i.e. a very long time ago) and wondered if anyone could comment on or update the authors predictions about the future of Class D, specifcally the analgog controlled vs digitally controlled amps.

http://www.audioholics.com/education/amplifier-technology/the-truth-about-digital-class-d-amplifiers

I feel like a dog watching TV in this thread. I see things moving and hear the noises but don't always understand what is being said.

I would basically agree with everything mentioned in that article.

[sheltie dave]

I'll go ahead and say it...my chip amp was sent to the floor, where it is still mopping and moping. A little too sterile.

[Mallette]

This will probably come off the wrong way, but critical listening is something that is learned and requires very controlled conditions to even start learning to differentiate between various sounds.

Not only doesn't come off in the wrong way, it comes off as

TRVTH

I learned that here a long time ago and it's saved me from a lot of dumb discussions.

See if you agree with this:

1. First, you learn to tell a difference.

2. Then, you decide one it is "right" and the other is "wrong."

3. Often, "2" is arbitrary and dependent upon learned and technical factors that may or not be related to general perception.

In any event, once I understood the basic principle I decided to leave development of that talent to those who want or need it. My only interest is is in good music.

I suspect many of us who really love class d are in the same category and appreciate cheap, good music over expensive, good music. I am not deaf to amp differences...well before class d I'd discovered that to me, all SS amps sounded the same at any price and it was too clinical in general, and way too clinical for 'horns. That transformer/output inductor aberration probably accounts for my epiphany the first day in 2005 I heard a class d amp in my own system and went "YES'M, that's what I've been looking for...cheap, GOOD music!"

And also why I can now much more accurately identify the equipment head from the music head by their comments re:class d.

Excellent write up, Mike. If you could get your amp on the market I think you'd have some attention at least from the Klipsch Klan. Just make sure you make at least one where you haven't "cured" that problem that makes'em sound warm and non-strerile to so many of us.

Dave

[Marvel]

As long as you only listen to kick drums, bass, guitar, and perhaps voice, a lot of folks don't hear the effects of AM distortion (e.g. high-THD SET amplifiers sound odd when trying to reproduce string orchestras).

Was the only SET you heard the Bottlehead amp? I think you need to get out more... [] Seriously, I don't think my Moondogs have an odd sound on string orchestras. Just finished listening to some Sibelius, Elgar, Dvorak... They have lots of strings, and they sound, to me, like going to hear our local symphony (they can sound odd themselves, but that's different).

Bruce

[Chris A]

Bruce,

Can you direct me to a graph of THD vs. output power for the amplifier that you mention (Moondog)? Nelson Pass does this for all his amplifiers, and I believe that he uses that graph as a design aid when evaluating amplifier designs.

Chris

[Marvel]

Can you direct me to a graph of THD vs. output power for the amplifier that you mention (Moondog)?

Nope, never seen one. While I would find it interesting, it hasn't bothered me that I don't have any real technical info on these amps.

I'll ask, somewhat tongue in cheek, do you enjoy listening to music or are you always trying to dissect the quality and technical merits of the equipment? I mean no disrespect.

Bruce

[Chris A]

Bruce,

I'll take you at your word, but understand that it twice appears to be ad hominem to the casual observer. I'd appreciate keeping the discussion on the equipment, if you don't mind. I am an engineer and I don't believe that I'm going to apologize for being one any time soon, nor am I going to go for subjectivist arguments in the near future.

The question was straight up, and I'd still be interested in seeing something from bench tests. I'm really trying to understand, not to criticize.

Chris

[Marvel]

Chris,

Not a criticism at all. We need engineers to help keep us from only believing in flooby dust. I would really like to see some tests from the Moondogs, but if no one has published any (they may be out there somewhere), I'm not about to ship mine off to have them tested. On the otherhand, these were also sold as kits wehre folks could pick parts to match what they thought would sound good. There may honestly be very few that would test the same.

If I can find someone close by who could do some tests, I would carry them over to have it done.

Bruce

[Quiet_Hollow]

I feel it's much too easy to digress into an amp topology discussion when, what I think, the real issue at hand is a big shift in how the source is dealt with.

Chris, I do agree with you. It is arguably beyond the scope of the Klipsch Forum. We're simply on the "front line" of change, in a sense, with these speakers that are so revealing of everything.

[LousyTourist]

Back in the day I ran my Klipschorns with a Sony VFET preamplifier... sounded real good to my ears but I was young and not overly critical. Lost that guy in the shuffle years back. They are pretty much hen's teeth now.

Fast forward to a decade ago or so... picked up a 300B SET, and that sounded great to me. I go by 'pounds per watt' and that baby packed 4 or 5 pounds per watt, so I knew it was good.

A while later, I found (and had rebuilt) a Sony VFET and I replaced the SETs with it. The lower bass tightened up (a bit) as I guess can be expected from SS, and otherwise it sounds fantastic. I had looked into the F3 but it was a bit too pricey for my blood. It's on my list of things to try someday, but I have to win the lottery first. Actually, I have to start buying lottery tickets first.

[Chris A]

the real issue at hand is a big shift in how the source is dealt with.

I don't think that many folks truly understand the effects of this: everyone still thinks in terms of analog stages. EMI and the need for component quality/stability is just erased from the signal chain by staying in the digital domain. The only requirement is real-time processing using the desired word length (digital resolution). By the current digital processing standards, this is almost trivial.

One wonders why this has been such a long time coming? Unfortunately the NAD is just the starting point - why AVRs don't output to HDMI (audio) and that downstream components use HDMI or other digital buses for connectivity is worth talking about.

Chris

[Mallette]

Unfortunately the NAD is just the starting point - why AVRs don't output to HDMI (audio) and that downstream components use HDMI or other digital buses for connectivity is worth talking about.

If you aren't spending time with Mike Bentz you should be.

Chris, meet Mike. Mike, meet Chris. Now, you guys build the perfect amp for heritage and let me beta test it.

Dave

[Chris A]

Down Dave, down!

The Aggies also say..."rest!"

[8-)]

Chris

[erik2A3]

Quiet_Hollow: I had to smile when I read your comment. We had covered this ground several years ago (that fact amazes me...), when some of us mentioned the potential and performance capabilities of some of the then-available T-Class amplifiers. Reactions were varied....from defensive to supportive. It's just interesting to see this come around again. I (as a few others here) have been very involved and active user/builders of tube preamps, and still very much prefer many of their merits. Back then, there were a few of us who used these amplifiers in our main systems, and I recall one individual whom I haven't seen post here in some time, who used a couple in a tri-amped system. This personal was also very technically oriented, and was a very capable builder/designer.

I recently purchased another from Parts Express, though I can't recall the model. It was under $90.00, with performance that comes exasperatingly close to an OTL amp I have that sells for many times the cost of the one from Parts Express. Frequency response is more evenly balanced, I feel, then it used to be in some of the amps I heard back when a similar thread came up. Very quiet, extraordinarily efficient, they are remarkable little amps. It's always a matter of personal taste, so probably a good idea to keep that in mind. There is another amp I have, or rather recently rebuilt, that is similar in many ways to the Parts Express amp: it's an old push pull Baldwin organ amplifier. I loved the sound of it so much I bought two more to rebuild this summer. The one just mentioned went to a friend, who I am glad to here is also able to sense some of the remarkable qualities of this new technology! I think the same.

[erik2A3]

Did someone mention Bottlehead SET amplifiers? Not to be contrary, but rather offer an opinion, that many consider them to be among the finest of that kind of amp available. A couple of observations I've heard in the past has to do with the comparatively small size of the output transformers used. This reflects really more of an incomplete understanding of the output topology than it does a design weakness -- their designs are far from weak. I'll leave some of the names associated with this company out of the details, but they are among a select group who almost single-handedly resurrected the vintage but, in terms of outstanding sound quality, superb output configuration known as "parallel feed" (aka parafeed for short, also known as shunt feed). Bottlhead products are NOT a step-down in terms of performance, and I say this as a Welborne Labs and Moth Audio SET owner (both of which offered highly regarded SET circuits). In many respects Bottlhead may in fact be superior to the other two (obviously subjective) -- at least in terms of opinions I've heard. Not sure if they still use MQ iron, but that's where they used to source their parafeed OPTs. Parallel ouput transformers are small because they don't have to be any larger than they are. There is a VERY beneficial separation between the DC power supply component and the AC signal side, which, in a more conventional air-gapped single ended transformer, is not done. Instead, a parallel feed amp uses a very large plate choke connected between the plate of the output tube and high voltage. I am absolutely one who makes an effort to give credit where deserved, and would like to thus encourage whomever it was that showed interest in one of their products, particulalrly their amps, but I've heard that new versions of their Foreplay preamp aren' too shabby, either. I bought the first Foreplay preamp kit back when Bottlehead was called Electronic Tonalities. It cost under $100, and was a killer preamp. I still have it. Just my opinion....as always YMMV.

[erik2A3]

Adding one more here re: parallel feed. Gordon Rankin of Wavelength Audio sums up parallel-feed well (have at look at their amps while you're there!) http://www.wavelengthaudio.com/amps-pf.html

[Marvel]

Not sure if they still use MQ iron, but that's where they used to source their parafeed OPTs.

Bottlehead says they have custom wound OPTs, but Magnequest lists upgrade iron kits on their website for most Bottlehead products, so an email or call would probably give a better answer.

Bruce