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


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Is now a good time to mention that you can feed
a digital input into a digital amp such that the digital to analog
conversion happens at the amplified output of the amplifier? [:o]

Yes,
I think it is because that is analogous to what is happening in the
transistors in PWM. The speakers do not reproduce the digital voltages
- they average them mechanically; likewise the PWM average (useable by
a speaker) output voltage does not reproduce the switching frequency.

Also, just to be clear, not all digital is binary and there being more than two states does not analog make...

So, still... is there such a thing as a non-PWM digital amp and how does it operate?

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"The speakers do not reproduce the digital voltages
- they average them mechanically;"

No, the output lowpass filter in the amp does that.

"likewise the PWM average (useable by
a speaker) output voltage does not reproduce the switching frequency."

'Cause it is filtered by the output lowpass filter in the amp.

Shawn

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There is a form of "delta" modulation in which pulse widths are all equal length and the modulation chooses a 1 or a 0 for an entire clock cycle. These are good for memory devices such as digital delay lines which can us single bit "word" memory chips to store waveforms. I think SACD is a type of delta modulation.

Leo

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"The speakers do not reproduce the digital voltages

- they average them mechanically;"

No, the output lowpass filter in the amp does that.

"likewise the PWM average (useable by

a speaker) output voltage does not reproduce the switching frequency."

'Cause it is filtered by the output lowpass filter in the amp.

Shawn

Shawn,

I'm referring to Who's mention of a digital signal going to the

speakers... and I think it still applies to the PWM even without the

filter - the speakers couldn't play the megaHz frequencies even though

that might be what was in the voice coils.

I'm not trying to be

argumentative, just trying to get some clarity on the subject. The

enthusiastic response to class D deserves discussion about just what is

happening with the signal whether we think of it as digital or not. I'm

not well versed in digital but I'm learning... I'm just not sure class

D is really digital - I have not found anything published about it yet

that says anything other than that it is analog all the way. Is there

something I'm missing?

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"I'm referring to Who's mention of a digital signal going to the speakers..."

The digital signal going to DSP speakers is PCM. In the speakers are DSP based crossovers and then either digital input digital amplifiers or D/A converters and more typical amps.

Shawn

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"I'm referring to Who's mention of a digital signal going to the speakers..."

The
digital signal going to DSP speakers is PCM. In the speakers are DSP
based crossovers and then either digital input digital amplifiers or
D/A converters and more typical amps.

Shawn

This sentence no verb.

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I was never saying to send a PWM signal to the drivers in the speakers....I was talking about "active speakers" that have their own amplifiers inside. You could run a normal D/A and use a normal amp, or you could directly feed a digital signal into a digital amp where the D/A process happens after the amplification. I think Shawn mentioned the same thing, but I just wanted to doubly clarify my point. Well hey, while I'm at the clarifying thing - I look forward to the day when active speakers become the standard practice as I believe strongly that the amplifier is part of the speaker. It will probably be a while though before the audiophile market starts to support that notion since it's not fully wide-spread in the pro world yet either (minus all the line arrays and studio monitors and so forth....) Imma have to go hunt down and research a bit more the few models y'all posted links to [Y]

As far as whether or not the amplifiers are "digital" - I think if one was familiar with the entire CD encoding and decoding process that they would quickly see the similarities. All the arguments one might make about digital amps being only analog would also be true for CD's...

Do you enjoy math Paul? I could provide you with some killer references on digital if you're feeling up to thinking a bit.

I wonder if those trying to say digital amps aren't digital (since their output is analog) are merely trying to avoid the audiophile notion that "digital is bad"? The Class D amps are a very cool concept because they work on the premise of maximizing the efficiency and linearity of transistors.

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I believe strongly that the amplifier is part of the speaker. It will probably be a while though before the audiophile market starts to support that notion since it's not fully wide-spread in the pro world yet either (minus all the line arrays and studio monitors and so forth....).

Did you look at the link in my post on the last page for the BeoLab 5?

Mark

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I'm just not sure class D is really digital - I have not found anything published about it yet that says anything other than that it is analog all the way. Is there something I'm missing?

Pauln, you are not missing anything. Class D amps--all amps--are analog! Parts of the signal in a Class D amp may look digital but you can not distinguish analog from digital by looking at a signal. How does it behave?

There are amp makers who do try to treat Class D amps as digital--but as a rule these amps will perform poorly compared to Class D amps which utilize normal analog control techniques (feedback, etc).

If you are interested I can find and post some links to a discussion and an AES paper on this subject.

Mark

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" I look forward to the day when active speakers become the standard practice as I believe strongly that the amplifier is part of the speaker. "

I like the idea of active speakers myself, but unfortunately, you might be looking forward for some time.....

I think I had a audio magazine that showed the Meridan active speakers that Shawn mentions. It was from the late '80's, early '90's.

I recall them being a black three-way tower, with a digital signal from a CDP right to the speakers. Each driver had a dedicated amp.

I don't recall if the crossover processing and digital to analog conversion was before or after the amp. I think they used a standard amp, with some sort of digital processing and D/A conversion before the amplifiers.

It's been awhile......

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" I don't recall if the crossover processing and digital to analog conversion was before or after the amp. I think they used a standard amp, with some sort of digital processing and D/A conversion before the amplifiers."

In the DSP speakers the crossovers are done via. DSP then converted to analog to feed amps.

http://www.meridian-audio.com/m_bro_spk.htm

Another very cool system like this is the NHT XD system.

http://www.nhthifi.com/2006/ht-s-ultimate.html

That isn't integrated all into the cabinets (like the Meridian) but it also includes all sorts of other corrections such as adjusting for power compression in the drivers, phase and so on.

Shawn

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Easy... buy a set of Jubilees... buy one of these:

http://www.deqx.com/

Hah, if only it were so easy on this college budget! I can't wait to have a job and be able to fund this hobby... I'll just have to wait for the next "old guy" to come along and take you up on your suggestion and then hope he's within driving distance of Illinois [:D]
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So, mine is not the most high - end, resolving system in the world, but I decided to give it a whirl and hook up a little Trend in my set up and see what happened. I found a guy selling one used on A'gon, and got it delivered for $100. It arrived today, and after opening the box, I had the little guy connected and making music in less than 5 minutes.

So, preamp is a Carver CT-17 pre-tuner, sources are a Phillips DVD 963SA with the power supply cap upgrade, a Technics 1210M5G with an Ortofon X5-MC, and a 2nd turntable - a old Pioneer PL-600 with an Ortofon OM20 Super (what I'm listening to as I type this). Speakers are RF-7's, unmodded.

I dropped Alan Parsons "Turn of a Friendly Card" album on the Pioneer, dropped the needle, and....um....Wow!

The comments about bass in earlier threads, they are for real. This little midget amp can get the RF-7's thumping, and the bass is clean, not muddy or boomy. Pretty amazing for such a little box.

The little Trend has a non-euphonic, articulate midrange. Not the most forward amp I've heard, but it is smooth in its own way, wihout being veiled or unnatural.

I've had amps in my system that have the RF-7's cooking on high - much to high - in the treble. While the highs are certainly pronounced, they are not fatiguing. I am starting to now wonder what a Dean G mod might really do to my RF-7's. Ugh, more $$!

I've got more listening to do, but I really, really like what I'm hearing so far!

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One of the four tubes that comprise my phono EQ was

microphonic and making me blue so I bought some replacements, arrived today! Although

one of the replacements was microphonic I was able to get a set in place that

was quiet and ready for serious evaluation,,,,

Albums listened:

King Crimson;: Three of a Perfect Pair

The Yes Album

Procol Harem; Grand Hotel

Led Zeppelin (1)

This is the Trends 10.1 with the La Scalas

The King Crimson album is one of their later works and has a

techno sound lots of bass and thwack as Duke likes the thwack is there

big time

The Yes album was extraordinary deep bass and the whole

thing holds together great at high volume (ave. 100dB)

The Procol Harem has a lot of deep bass and piano that

sounded fine. This is a very well recorded album.

The Led Zeppelin is a case in point this is the original

record I bought back in 69 played it a bunch on the Magnavox console back then, sounds absolutely fantastic through the La

Scalas at high volume (100 dB).

I am so impressed by this little Trends amp everyone should

get one just to hear how great it is

Off to dinner

Pauln

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