Digital amplification in retrospect...it made a believer outta me!

[Erik Mandaville]

Sure, I understand that, Chris. I had a cobalt version of the Horus here for repairs last year, and thought it to be a really great sounding amp. I couldn't afford the cobalt OPTs when all of this sort of happened, but I think the permalloy OPTs are quite good, as well. I think What you are saying about the cost factor is important, and I in fact took out a loan from my school district credit union in order to buy the parts I needed to build two Horus monoblocks from scratch.

I actually prefer the Teac to any single-ended amp I have heard, including the cobalt Horus I worked on last year. I've said it so many times before, but the Horus is a fantastically good amp. You might even consider the possibility of an 'ultrapath' cathode return on the output stage -- which I did on my Moondogs and Horus amps. Leok also did this on his cobalt parafeed mod of the Moondog, and this is something that Jeff was able to see, as well. I also have the cathode resistor on the 5687 input cathode bypassed with a small, high quality electrolytic capacitor (as do the Moth si2A3, the Moondog amps, Wright 2A3s, and the Welborne DRDs). This improves the gain characteristic even more, and will possibly bring an improvement in bass response to your amplifiers. Leaving that part unbypassed is sometimes thought of a more 'pure' approach, but is probably less common. It's really just another 'personal taste' and preference issue. An extra filter stage was also added to the above Horus, and helped reduce a small amount of hum and noise. I'll never sell my modified Horus amps, though. I like them very, very much. With the modified quad 6SN7 grounded grid (not the Transcendent Grounded Grid) preamp I built, the Horus were excellent two channel-only amplifiers.

At this time, the Teac sounds better to me than both the Horus and Moth amps. It's bass response is not only much stronger, but it is tighter and cleaner, and completely absent of the overhang I find with the Moondog (less so with the Horus). That said, I would never part with my Moondogs, either! They are also really great amps.

As you mentioined, cost is an interesting thing to look at. A single empty and unpunched chassis for one of the Horus pair was about the cost of the light-weight, far more powerful 3-channel Teac. I think we become used to equating aesthetic and physical weight characteristics with 'high end sound.' Tubes require heavy transformers for, among other things, impedance matching to the voice coils of the speakers they are powering. Power and OPTs are also physically quite large, and it perhaps just makes more sense for beefy hardware like that, which necessarily results in physically heavy amplifiers, to cost alot. For my part, I confess to having adhered to the perhaps somewhat underinformed notion that there is a direct correlation between an amplifier's weight and sonic attributes -- that the heavier the amp, the better the sound; and the less I mind if there is a correlation between the weight of the component and it's price tag. If I had paid the same amount for the Teac that I paid for the Horus chassis and parts to build them, I would feel like I had been terribly ripped off -- despite how good the Teac sounds! The sheer physical weight of the amplifiers helps me think and believe I did well for the money -- which, having made them myself, I think I did.

The one amplifier I have made that I think shares some of the sound quality of the Teac is the SE OTL. It is simply a stompingly good (whatever that means!)value for the money, and sounded better to me than any transformer coupled amp I've heard. With the same approximate power of a single-ended 45, all three SE OTLs I made for other forum members sounded fantastic to us. Marie thought it just got really hot, which, being a pretty inefficient amp (compared to especially the Teac!), it does -- sending out a considerable amount of heat energy. Same is true for the Transcendent Grounded Grid. There were a couple of posts that commented on the very small plate and filament transformers in the GG, but it's simply an unfounded argument -- based once again on the incorrect thinking that 'heavy' means 'good.' Heavy can mean good, but the sound I get from this small digital amp cuases me to carefully adjust what I have known and thought to be true about audio amplifiers.

Erik

PS: Sorry this is so long! We have a school holidy today, and I can't do too much else these days other than listen to music and write!

Chris: Please know I am not saying this Teac is better than your Cobalt Horus (What would it matterif I was!?). You have already indicated you far prefer the Horus, and I respect that. Everything I am saying is in light of my own recent experiences. There was also a time I would have laughed out loud at the idea that I might one day be listening to a surround sound system with an SS digital processor, 7 speakers, and a tissue-box-sized digital amplifier. You know what drastically changed my thinking on all of this? Paul Klipsch's 'minibox'!

[Mallette]

Erik: Que es la Klipsch "minibox," por favor?

Dave

[Erik Mandaville]

Dave:

It combines hard Left and Right speaker level signals for a derived center channel/plus volume control for blending the center with the stereo pair.

It sent me down the road to well-done surround sound so quickly I'm surprised I didn't get stopped for speeding. Actually, I did get pulled over in a manner of speaking...

Erik

[Mallette]

Is there any difference here between this minibox and circuits such as the Hafler DynaQuad unit I am using for the same purpose? It has a center volume as well, but of course only attenuation since it is a derived channel. One of the reasons I've been looking for a Belle or LaScala to replace my center Cornie is that it is about 3db too little to do the center job perfectly. Sometimes it is good, sometimes you still have a bit of a "hole." You may or may not recall that my listening room is about 4 feet or so from providing a perfect 'horn soundstage w/o a center fill.

Dave

[sfogg]

Dave,

"Is there any difference here between this minibox and circuits such as the Hafler DynaQuad unit I am using for the same purpose? "

You would have to open up the DynaQuad and see what it is doing. The minibox literally is just a passive mixer that combines the entire left channel with the entire right channel and that gets fed to the center. It can work well but for hard L or hard R material it shrinks the soundstage width since it ends up getting reproduced by L and C or R and C.

The Hafler might be doing that to of course. Does it also offer a 'surround' output? If so that is most likely just a L-R difference signal (same as connecting a speaker across the positives of a stereo amp).

Shawn

[Erik Mandaville]

Dave:

There was a recent thread on the Hafler circuit a few pages back -- can't recall what the title/subject of the original post was, though...

We are using the Klipschorns along our shorter, approx. 15 foot wall, and we were able to get a very good center image prior to the inclusion of a third center channel. However, and despite that fact, using a dedicated derived center speaker added more to the overall perceived sound than just provide more sharply delineated images. It added a much improved(IMO)sense of volume and mass, and that in turn is what I think made the sound so captivating and all the more present and 'real.' With side and rear channels, the illusion of listening to a live musical event, which is what I think we are all after, became stronger still. Once again, the effect provided by the Lexicon is subtle and understated. I imagine some might, and naturally so, think that what we are experiencing is the result of 7 speakers all blasting away at one's head and at the same volume. It's nothing at all like that. The sound, while still coming from a frontal position (with flexibility even with that characteristic)has a comprehensive quality provided by the surround information -- as if one were in a real acoustic space and in the same room as the performance.

When I switch back into two channel stereo only mode, the sound quality is still quite good, but sounds 'forced' or emphasized in a way that isn't as subtle, natural, or complete as the surround experience. BTW: We don't use this for home theater -- it's strictly a music system. The majority of what we like to watch in terms of movies usually doesn't depend as much on sound effects as other aspects, so we are happy with just the speakers on either side of the Trinitron for 'home theater.'

I'm pretty sure that we'll eventually incorporate this into a dual-purpose system, but that won't happen for some time. It would be nice to get a better television for that, but the ones we have researched and looked at just 'ain't cheap at all!

Erik

[sfogg]

Erik,

" and we were able to get a very good center image prior to the inclusion of a third center channel. However, and despite that fact, using a dedicated derived center speaker added more to the overall perceived sound than just provide more sharply delineated images. It added a much improved(IMO)sense of volume and mass, and that in turn is what I think made the sound so captivating and all the more present and 'real.'"

Center channels.... they are *not* just for HT....

"BTW: We don't use this for home theater -- it's strictly a music system. The majority of what we like to watch in terms of movies usually doesn't depend as much on sound effects as other aspects, so we are happy with just the speakers on either side of the Trinitron for 'home theater.'"

My system has always been music first too but has had a HT aspect to it for a long while as well. But that literally (until very recently) was nothing more then a 32" RCA direct view TV up front with appropriate video sources plugged into the Lex. then into it. IME, the sound was more important then a huge picture. Watch a scary movie and mute the sound.... how scary is it? Then listen to the sound with the picture off.... which is more effective?

Great sound with a small picture was more involving/enjoyable then a big picture with lousy sound. Of course when you have both....

As far as what you watch for movies and what they need for surround effects you might be suprised at some effects. The most impressive are the really subtle stuff that draw you into the movie without your even realizing it. And of course there is a *lot* of music in many movies so getting a system that serves the music well works here too. And compared against a lot of how music is being mixed/mastered now movies still understand the importance/effects of dynamic range... something the horns handle easily.

"It would be nice to get a better television for that, but the ones we have researched and looked at just 'ain't cheap at all!"

(Psst.....when it comes time for that think front projection!) Keep your regular TV for normal viewing and hang a pull down screen up or put one up on the wall if you have the space for it. Then when you want to watch a movie you can do it on a BIG screen. Front projection can be done for much less then many people realize... less then most any of the 'big' screen TVs you will find in Circuit City or places like that.

(I am such a bad influence... Marie is going to kill me.....)

Shawn

[Mallette]

Hmmm... Thought the Hafler circuit had been beaten to death in the forum.

Here are the basics:

1. Hafler orginated the concept of surround by determining that conventional two channel stereo would have ambience information that was out of phase with the direct information.

2. His original circuit was simply to wire the rear channels out of phase with the front, tending to favor the otherwise obscured and sent to the front ambience information.

3. When developed as "DynaQuad," he added an aid to setting rear levels, switch to control rear/main/both, and a volume control.

4. The concept was developed in the 70's into "quad," where out-of-phase information was electronically retrieved/enhanced via various analog encoding schemes that thoroughly confused everybody.

5. Whole concept died until Dolby Pro Logic, which has it's roots in Hafler

Anyway, that's a nutshell. I am using the "current" DynaQuad unit which also provides a summed L+R center. It does a great job with stereo sources, and I even have the original DynaQuade demo LP, which has some moments of Front/Rear separation every bit as discrete as Dolby/DTS.

Firesign LP's, with all their overdubbing, mixing, etc. produce extrordinary results due to all the out of phase info in the 2 channel mix.

Dave

[Erik Mandaville]

I'm sure it had/has been beaten, but I guess I wasn't around to contribute to the flogging!

In any event, the Klipsch minibox simple derives a third, center channel by combining full Left and right signals -- and then sends the result to a mono amplifier connected to the third speaker. It's an incredibly simple litte circuit that sounded incredibly good -- and much better after the installation of in inline crossover (I installed that in the box, as well)that rolled off at 150Hz.

Thanks for the information on the Hafler stuff, Dave.

Erik

[sfogg]

Dave,

The 'Hafler' circuit has been discussed relative to several different implementations which is where some confusion happens. Hafler, typically, like you said refers to the difference signal between both channels... what a speaker will receive if it is wired across both positives of a stereo L/R amp. But Hafler also had info on how to get a center channel by wiring across the negatives of a stereo amp. That is why it can be a little confusing when talking about a 'Hafler' setup. One can also add L-Pads to the front and rear speaker to give more control over balancing it in assuming it needs to be turned down relative to the mains not up.

" It does a great job with stereo sources, and I even have the original DynaQuade demo LP, which has some moments of Front/Rear separation every bit as discrete as Dolby/DTS."

If you are listening to the orignal 'Hafler' passive surround circuit it has 3dB of channel seperation relative to the front. Unless it is using active steering (which I don't think it is) then it will have more channel seperation.. probably on the order of 10-25dB of seperation.

DD/DTS is actually discrete encoded channels (up until around 16kHz or so where the encoding starts to share data) and has CD like levels of channel seperation... as well as stereo information in the rear... not mono like DPL or the Hafler circuit.

Shawn

[Mallette]

Shawn:

"But Hafler also had info on how to get a center channel by wiring across the negatives of a stereo amp. That is why it can be a little confusing when talking about a 'Hafler' setup"

Agreed. Note that I mentioned I am using a "modern" Hafler with a summed L+R center Hafler never provided except in the Dynaco ST-80 amp.

"If you are listening to the orignal 'Hafler' passive surround circuit it has 3dB of channel seperation relative to the front. Unless it is using active steering (which I don't think it is) then it will have more channel seperation.. probably on the order of 10-25dB of seperation."

Agreed again, in theory. No active circuits but significantly better than 3db F-R sep achieved (as also inadvertently on the Firesign albums) by increasing out of phase information via various methods in the source material.

"DD/DTS is actually discrete encoded channels (up until around 16kHz or so where the encoding starts to share data) and has CD like levels of channel seperation... as well as stereo information in the rear... not mono like DPL or the Hafler circuit."

Agreed again...I specified Dolby Pro Logic, the predecessor, as having its foundations in Hafler theory.

Dave

[Erik Mandaville]

Just read in Stereophile this afternoon, a review Michael Fremer did of a new very powerful digital amp from Yamaha -- the MX-D1 500watt/channel. At $5000, it is expensive to say the least. I'm not going to quote from the review, but recommend it if you haven't done so -- many of you may already have. I found it interesting, with certain similarities to the little Teac. If you are looking for an amazingly good and silent running amp for Klipsch Heritage, the Teac is one of those very definite 'no brainers.' It sounds like it should weigh at least 100 pounds! Seriously!

this is the April 2005 issue of Stereophile.

Erik

[Mallette]

You've mentioned this "little Teac" in several posts, and, unless I am missing something, you've mentioned neither the model nor the price so far.

Also, have your hear the Panasonic I purchased sight unheard for 150.00?

Digital amps are a mystery to me both in theory and in application. However, those of you who know me at all know that I will change attitudes at a moments notice when presented with verifiable facts, and am always open to a new idea.

As to the 5,000 digital, even without knowing how digital amps work I am skeptical. I certainly do know how binary circuits work...and, basically, they either do or they don't and the cheapest works as well as the most expensive since it is a yes or no proposition. Now, the D/A part, of course, is another issue, but even there the theoretical differences would be quite small between expensive and inexpensive components.

OK, so I've stated I am ignorant, then proven it with a load of BS off the top of my head.

What I started out to say was that if digital amps follow the cost/performance curves of digital technology as we've come to know it, extraordinaryly clean amps will start showing up blister packed at Kroger pretty soon.

Dave

[sfogg]

Dave,

See this thread for info on the Teac:

http://forums.klipsch.com/idealbb/view.asp?topicID=62868

Or do a search on Teac and find several other threads as well.

Shawn

[Mallette]

Thanks, Shawn, will do.

Dave

[3dzapper]

Dave here is a link to Tripath. the company which makes the "class T" digital amp chips in the Teac. You can learn about the technology there.

Rick

[3dzapper]

Deja vu?

[jt1stcav]

I'm curious...if the cheap lil' SI 5066 T-amp that weighs 1.5lbs. is supposed to sound so wonderful due to its chip, then what about the much heavier digital amps like the 5 grand Yamaha? Or the one-ton BASH digital amps you'll find inside SVS subwoofers? Does weight make a difference between digital amplifiers and their sonic signatures, or do they all sound the same? Will bass output be less with the tiny SI T-amp as opposed to the SVS BASH amp and its beefier power transformer?

[3dzapper]

The "T" amp and the BASH amp are two entirely different animals Jim. The "T" uses high frequeny signals to turn the amp on and off, BASH "class D" technology uses the peaks of the natural waveform has much larger output devices and the heavy transformer necessary for the high output power. BASH Class D is not digital it is part of a progression up from Class A, AB, AB1, B, etc. Not to be confused with Class D digital amps like the Gainclone.

The SI does not have nearly the sound quality of the Teac. Especially in the highs. They are good sounding for $30 and are fun toys. The Teac is great sounding for $100 and are serious amps. (Not SET but very good SS)

Rick

[jt1stcav]

Thanks for the explaination, Rick (I'm more confused than ever dammit)! As interesting as this digital technology is, I'm still partial to my old fashioned 300B SET!