Just ordered a Trends 10.1 Class T Digital Amp - A whopping $130

[Arky]

I know you like it

loud and extended low. The Trends has a great solid low end and will

play clean (.03%) up through 5 watts (110dB on the big Heritage). You

know how loud super clean peaks of 110dB sounds... (I don't, 'cause

I've only approached 100 which for me is very loud - especially since I

am still getting used to the La Scalas playing deep bass loudly without

room effects - still freaking me out!). I'm trying to listen to

something a little louder each day but I have already passed the point

of what I would consider max super loud for me (2 watts peaks!).

This paragraph sells me, if it's clean up to 100db, im in.

[Arky]

Damn, I guess i'm in ignore mode now. [8-)]

[Rivendell61]

The Teac version uses the same 2024 chip and the instructions for that mentioned that the fine timing of the transistor switching is controlled by an algorythm that "learns" how to optimise the switching as more and more music is played through the amp. Since the Trends has the same chip this may be true for it as well, but I find no mention of it. Do your SI instructions say anything like that? Many are finding that the Trends sounds better and better as it gets some hours on it (run in?) and I suspect it may use the same switch optimization algorythm to dial in the performance.

Tripath literature is somewhat hyperbolic--the 'learning algorithm', etc is Tripath talk for feedback.

Mark

[Deang]

Arky, buy one for a nice change of pace sound, and for some blissful low level listening. There are a lot of different ways to get good sound, and this is certainly one of them -- but it's not the way to go if you live in the 100dB realm of listening. I'll drive mine to 100dB+ peaks on occasion with movies, but it will drive a nail through your skull with compressed Redbook recordings at those levels.

[pauln]

The TEAC doesn't use the 2024.

The Trends has a great solid low end and will play clean (.03%)

up through 5 watts (110dB on the big Heritage). You know how loud super

clean peaks of 110dB sounds...

Yeah, if you sit three feet in front of the speaker and don't factor

in headroom. Into an 8 ohm load these things barely hit 6 wpc.

Into 4 ohms, you get about 9 -- and to handle peaks

without clipping you need at least 3dB of headroom. In my room, it

sounds clean and uncompressed up to about 95dB, which is what one

should expect sitting about 12 feet back with a 104dB speaker. Anyone

into a lot of live level listening should ignore this thread.

http://www.crownaudio.com/apps_htm/designtools/elect-pwr-req.htm

Opps! Sorry, yeah I think the Teac is the 2050?

My

LS are cornerd 15 ft apart and I'm 12 ft back in a greater than 2500 cu

ft space with a high ceiling. The Trends sounds better loud and deep in

this space than anything else I've owned - including the old mighty and

majestic Carver M500t 250W/ch I used with the Heresys.

When I

refer to peaks I am thinking of it as headroom. The mower and leaf

blower and weedeater guys just asaulted the sonic peace of the

neighborhood with their unmufffeled gas engine cutting and blowing gear

for about an hour, so I took the opportunity to play some 38 Special

quite loud. A bit under 90dB is normally as loud as I would ever listen

- that is very loud to me, but in the name of science I turned it up to

the mid 90's and it seemed to hang together quite nicely - but its just

too loud for me. On some of the more dynamic passages with hard bass

and drums featured I turned the volume of the preamp up to 1/2 - damn

this gets scary loud but no clipping or ill effects - just too damn

loud for human listening. I can't really say about how clean or

uncompressed it was at that level because I never experience these

levels and only had it up for a few moments but "Hang On Loosely"

sounded like it was hanging on pretty tightly. I just can't imagine

people listening this loudly in the home. I don't even have a clue how

to begin to evaluate music that loud... the physical impact of the

sound is exciting but it is too loud for my personal tastes to enjoy as

music. Those into "live level listening" will have to take it from here

and say more about the amp's higher power output when they get their's

in service.

Happy listening all,

Pauln

[Colin]

Not surprised about the Carver. I had one on Cornwalls for a year or so. Hard hitting. Both bass and treble. The treble however wears your ears out.

[Mallette]

Having been a digital amp lover for several years I've followed this with interest. Suddenly I ask myself: SELF, where are the digital PREAMPS? You tech guys should have an answer for this. Paul? Leok? Dean?

What's the deal?

Dave

[leok]

A phono preamp is a precise exercise in low noise analog design. There are versions that digitize, then do RIAA equalization. But for line sources, one doesn't need a preamp: the amplitude is already high enough to drive most amps to their rated power (there are exceptions such as the Wright SETs). So, all that is really needed is a passive volume control and source switches.

Digital equalization "preamplifiers" do exist. I guess those are the equivalent.

Leo

[Mallette]

Thanks, Leo. Makes sense. I've been wrong about the consumer market. I assumed the OEM's would have pretty much all gone digital by now given the low cost. I remain unsure why this has not happened unless they fear consumers will feel that their products aren't large or heavy enough in appearance or something.

I still believe it will happen soon as this is a case of a win-win situation for the end user where they will be getting better sound (wether they care or not) and lower cost at the same time. Green, too.

Dave

[DrWho]

I'm looking forward to the day when we're sending a completely digital signal to our speakers where the manufacturers will already have all the active filtering required for getting the most out of the speakers. If I'm not mistaken, the cool thing about digital amps is that you can modify them to accept a digital input such that the D/A conversion occurs during the amplification stage.

Speaking of which, that sounds like a good senior design project...it'd be a good excuse to come out with 100W digital amps too.

[Deang]

There are quite a few high powered versions available, most based on the Hypex ucd-400 module. I think you'd be surprised at how well the low powered versions do on the more efficient Klipsch designs.

[sfogg]

"I'm looking forward to the day when we're sending a completely digital signal to our speakers where the manufacturers will already have all the active filtering required for getting the most out of the speakers. "

Meridian has been doing this for over a decade. One of the big problems with something like this is you end up getting locked into a company. You need several of their products to be able to utilize a system with their DSP speakers.

Shawn

[sfogg]

"
There are quite a few high powered versions available, most based on the Hypex ucd-400 module."

Some are based on them but there are numerous other designs out there too. Spectron has been building high power digital amps for the audio market for quite a few years and that is their own design. Crown has what they call the Balanced Current Amplifier and they are extremely powerful.... 500w/ch into 8 ohms and way more into lower impedances. I have two of these Crowns, great amps. Then there is the ICE Power stuff from B&O and TI has the Toccata stuff...etc...etc. The market is getting bigger and bigger.

Shawn

[Deang]

Aren't you running those Crowns on your subs? How do they do for the HF's -- just curious.

[pauln]

The Trends and other class D pulse width modulation (pulse duration
modulation) amps are not digital, the signal path is full analog only.

So
just to be clear, how does a true digital amp really operate? Is it
being suggested that some would perform a D/A conversion by some
multiplying factor and others would actually output a digitised signal?

[Rivendell61]

Re Meridian: the new G95 (surround receiver) uses 5 100 watt Hypex amps: http://media.meridian-audio.com/datasheets/g_series/G95ds-a4.pdf

As Shawn says there are lots of higher power Class D amps out there. Like these guys: http://www.d-amp.com/

Kharma has new --very nice--monoblocks (Hypex) that are 350W at 8Ohm and 1200W at 2 Ohm.

Dr Who, Have you seen these? If you read the text/specs at the bottom of the cut sheet I think they are along the lines of what you were describing : http://www.abtelectronics.com/images/products/PDF_Files/BeoLab5_CutSheet.pdf

They use some interesting ideas from these guys too: http://www.sawonline.com/overview.shtml

Mark

[sfogg]

Dean,

"Aren't you running those Crowns on your subs? How do they do for the HF's -- just curious."

Yes, they are on my subs now. A place they excel with 10,000:1 damping factor and huge amounts of power.

Never tried them on the horns.

I bought the first one for sub duty after my old sub amp (Onkyo M508 Grand Integra) died. JOOC I tried it on my L/R speakers of the time (cone/domes) in place of the Sunfire amp I was running on them. The sounded considerably cleaner then the Sunfire amp I was running with a smoother more effortless sound. I liked them so much that amp stayed on the L/Rs, I sold the Sunfire and bought another Crown for sub and center channel duty.

Shawn

[sfogg]

"The Trends and other class D pulse width modulation (pulse duration modulation) amps are not digital, the signal path is full analog only."

I realize the analog lovers have to tell themselves things like this to justify liking a 'digital' product (gasp) but when you convert audio (more like modulate a digital signal based on what an analog signal is doing) into pulse width modulation it is not analog anymore. You convert/modulate the audio to a binary start (either on or off) which is by definition digital. How the signal gets reproduced is by altering the binary state.... how long the binary signal is on or off and then by passing it through a low pass filter.

Shawn

[pauln]

"The Trends and other class D pulse width
modulation (pulse duration modulation) amps are not digital, the signal
path is full analog only."

I realize the analog lovers have to
tell themselves things like this to justify liking a 'digital' product
(gasp) but when you convert audio (more like modulate a digital signal
based on what an analog signal is doing) into pulse width modulation it
is not analog anymore. You convert/modulate the audio to a binary start
(either on or off) which is by definition digital. How the signal gets
reproduced is by altering the binary state.... how long the binary
signal is on or off and then by passing it through a low pass filter.

Shawn

This
is somewhat of a fine distinction. While it is true that the
transistors are swiching between full on and off they are doing so in
the megahertz range. The time average voltage output variation is
baseband continuous in comparision to that high frequency. To take your
argument to it's extreme would be to insist that the record groove
surface interface with the stylus is 40-bit digital because it is
comprised of the individual molecules of PVC exerting force to the
stylus, or that the transmission of signal to the speakers is digital
because the free electrons jump from one copper atom to the next, or
that the propagation of the sound through the air is digital because
the "waves" have to make their way one molecule at a time. Ultimately
there is no low level continuity in anything in nature if you look
closely enough, but things behave in a continuous way if the size and
or time scale is appropriate. That scale is part of what it means to
call the audio baseband when compared to the switching speed of the
transistors in PWM. The audio is baseband continuous for CD frequency
digital after it passes the D/A conversion as well by the same
reasoning.

Another thing that occurs to me is that one of the hallmarks of
a proper digital system is that it should always provide the same exact
"file" of data up to the point of the D/A conversion... (or does
dithering and other things make it different for each play???); whereas
the PWM stream of on/off will never be the same for each playing (not
because the input is analog but because there is no relative synching
between the signal with the comparator's input triangle/sawtooth wave).
Well, that argument is not very strong either...

Anyone else have any thoughts on what is digital or not in PWM? If PWM is digital, I still really like it.[:$]

[sfogg]

"While it is true that the transistors are swiching between full on and off they are doing so in the megahertz range. "

It is not relevant where the range of switching occurs in. It is that they are acting as switches... either on or off... a binary state that is relevant.

"To take your argument to it's extreme would be to insist that the record groove surface interface with the stylus is 40-bit digital because it is comprised of the individual molecules of PVC exerting force to the stylus, or that the transmission of signal to the speakers is digital because the free electrons jump from one copper atom to the next, or that the propagation of the sound through the air is digital because the "waves" have to make their way one molecule at a time. "

No, that has nothing to do with what I said.

"Ultimately there is no low level continuity in anything in nature if you look closely enough, but things behave in a continuous way if the size and or time scale is appropriate. "

What I said has nothing to do with 'continuity' of the signal. It has to do with that the signal is in one of two states. Either full on or full off. That is a binary state.... a digital state. Any of your above misrepresentations has far more then one of two states... in other words analog.

"The audio is baseband continuous for CD frequency digital after it passes the D/A conversion as well by the same reasoning."

Actually it is continuous after the reconstruction filter. After the DAC and before the filter it is very much a bunch of square waves. And yes, it is continuous at that point no matter how much the analog guys want to argue 'connect the dots', 'stair step' or whatever.

Like I said... that PWM somehow is not digital is something the analog guys try to tell themselves to delude themselves about liking something digital.

Shawn