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Good Class D amps ??


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1 hour ago, GeneZ said:

  I think I found it.  They tell you to stay away from 2 Ohm speakers.  That causes problems. 

https://www.superbestaudiofriends.org/index.php?threads/nuprime-sta-9-power-amplifier-mini-review.3932/

Well I notice their amps usually spec same wattage at 8 and 4 ohms, or sometimes even less into 4 ohms.  This would indicate they are rather limited in current capability.  Some 4 ohm rated speakers with odd phase angles or impedance dips could cause issues with such an amp.  And they do say in the manuals do not use 2 ohm speakers.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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1 hour ago, GeneZ said:

 

Do you have a 2 ohm speaker?  Know anyone that does?  Most people should not be so concerned.  These amps sound VERY good.  All this data dumping, but no listening?

I am sitting here listening to my ST-10.  Silly fear mongering arguments is all I see.  2 Ohm speaker?   Google it.  Most are car speakers.  ;)

You asked this question to the wrong person.  I've got a speaker that dips to an ohm.  And the Nuprime won't handle the load well.  

 

I do realize it is not typical, and no need to get defensive about your amp choice.  The reality is many speakers that are rated at 4 ohm and better have some portions of the frequency band that will require additional current.  You may not understand how phase angle can have what seems an okay impedance yet will suck much current from an amp. The Nuprime may still sound fine for most of the time, but could struggle vs beefier amps.  

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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30 minutes ago, crenca said:

 

For those of us that have observed this for awhile (e.g. check out JA's measurements of the usual "audiophile" brands going back years) it is the norm that an "8 ohm" speaker is really a 6 ohm or 4 ohm speaker (that dips below 4, 3, or even lower).

 

Interesting what you say about REL (I run REL's).  REL's tap the amp's outputs with a high impedance (going from the top of my head, >10K) simply for a signal.  Can't think of a reason this would be a problem for an amp.  What's NuPrime's explanation as to why it is for their circuits?

I'd need to check, but I bet Nuprimes are actually differential output.  So there isn't really a ground.  Just plus and minus polarity at the output. That could be a problem input right into a REL or any of the multitude of other subs expecting a single ended input with ground on one side. 

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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4 minutes ago, GeneZ said:

 

 

What speakers?

Soundlab electrostats.  Not just low impedance in the upper frequencies, but a nasty phase angle approaching that of a capacitor more than a speaker.  This is it below.

 

666SLA1JAfig01.jpg

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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12 minutes ago, GeneZ said:

Well folks ... That low impedance issue was apparently 'old news.'   With normal low impedance speakers there is no problem with "current" models.

 

Here is an excerpt from the Nuprime STA-9 manual. (which is below the ST-10)

 

Features:

Single End Class A + D amplifier design Bridgeable allowing switch between stereo or mono mode.
Enhanced even-order harmonic (H2) circuitry resembling the most attractive features of tubed-amp sound without its drawbacks and limitations.
Highly reliable under no-load condition and enhanced short circuit protection.
High output current drive capability for low impedance speakers.
550 KHz switching frequency for accurate reproduction of musical signal.
New linear power supply with a high-efficiency toroidal transformer. Reduced high-frequency noise and strengthened low-frequency performance.
Signal path avoids cross-linking capacitors, thus achieving a frequency response at DC level for pure musical enjoyment.

 

https://nuprimeaudio.com/product/sta-9/?v=7516fd43adaa

 

Well their specs don't jibe with that claim exactly. 

 

They show the same peak power output at 8 and 4 ohms.  Amps with healthy current should come close to doubling the rating at 4 ohms vs 8 ohms.  It is a goodly amount of power, and might not be an issue usually.  But the amp is incapable of big current output should it get connected to a speaker that needs it.  I've long thought speaker makers should try harder to make easier loads, but that rarely happens.  Now something like a Maggie which is 4 ohm, and needs a bit of power, the Maggies are almost entirely resistive.  So the Nuprime type amps would likely be fine and dandy with those. 

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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29 minutes ago, GUTB said:

I just got in a Maraschino used for $650. I’m curious about these amps because they achieve 2x the bandwidth as other class D designs, they’re unique, and pretty cheap used. If nothing else it’ll be good enough for my PC. It’s plugged into a Furutech NCF outlet via a LessLoss standard + Firewall 64X.

 

Initial listening impression is that they don’t ruin the soundstage or my ProAc’s ability to image which is good. The midrange isn’t very convincing but not that bad either. They seem to make my vinyl sound like CDs, possibly robbing it of some dynamic performance. It plays well both connected to my tubed pre and directly to my tubed DAC. Gain is low so I’m finally spared my pre’s tube hiss. Anyway we’ll see. 

 

016CC252-9A5F-4ED3-A4E3-6F26A96A5FB9.thumb.jpeg.d4892f0183e39d11fad57e950ee5399f.jpeg

 

 

Now it is all so clear to me.  This must explain the following strange seismic waves.  It was GUTB finding a class D amp that DID NOT SUCK! And then the earth shifted beneath his feet just a bit. 

 

https://www.nationalgeographic.com/science/2018/11/strange-earthquake-waves-rippled-around-world-earth-geology/

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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  • 1 month later...
On 12/22/2018 at 7:34 AM, Matias said:

I would really like to see NuPrime's measurements like the typical THD x power graphs by frequency, as ICEpower and hypex use. I could not find any measurements on their website or manuals... Not that I am an objectivist only but still I enjoy analyzing the differences. Specially with all the hype around the Evolution One.

https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-nuforce-sta-200-power-amp.5039/

 

Measured results for a Nuprime amp.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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The new Icepower also works at a higher switching frequency. Over 400 khz vs 110 khz. Means reduced interaction between speaker load and treble response from the output filtering.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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2 hours ago, GeneZ said:

Nuforce is no longer in business.  The Nuforce STA 200 was a class AB amp was designed in part by Goldmund - as in the JOB amplifier. 

 

Nuprime was created to transfer the high end line of Nuforce, and to continue with only that level of product.

 

These links provide some significant measurements of some of amplifiers, and the new the Nuprime Evolution Amp..

 

https://totallywired.nz/nuprime-2/nuprime-evolution-one/

 

https://www.hifi-advice.com/blog/review/analog-reviews/amplifier-reviews/nuprime-st-10-power-amp/

 

Where are the measurements in those links?

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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2 hours ago, GeneZ said:

Why not cut to the chase? 

 

Someone ought to manufacture an amplifier and call it...   "The .00001 THD."

 

It would eventually gain the nickname...   "Are you Happy Now?  Amp."

I think benchmark and mola mola are one decimal point or less from being there.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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1 hour ago, audio.bill said:

Maybe this was mentioned previously, but to be clear (given the subject of this thread) the Benchmark AHB2 power amp is not a Class D design. To quote from their website: "The AHB2 has a bipolar class-AB output stage." It uses some unique error cancelling technology and "achieves a power efficiency that rivals that of a Class D (switching) power amplifier."

Yes, but I was replying to GeneZ's post which didn't seem concerned with class of operation.  

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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12 minutes ago, GeneZ said:

   Do you know that some scientists believe that those who find true love can be measured?    Though, they have not found true love themselves?  How ironic life can be!

Life can be ironic. But this is no example. I can measure height without being tall. If love is measurable, there no reason it can't be measured by some one not in love.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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1 hour ago, GeneZ said:

 

I do not do blind tests.  I live with a piece of equipment for several weeks to become accustomed to it. 

 

I will then try the other.  It should not be hard to hear a difference if there really is one.

Also not hard to hear a difference when there really isn't one using this methodology.  

1 hour ago, GeneZ said:

 

If the differences are not obvious?  Or, just another flavor?  Then its not worth making any change.

 

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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20 hours ago, GeneZ said:

No one can hear a difference that isn't there.  And until you have the study showing musicians aren't humans, we'll know when there is no difference they are prone to hearing one anyway.  Plus equating audiophiles with musicians is leap in logic.  

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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  • 2 weeks later...
4 hours ago, Ralf11 said:

we need a good SET Class D amp with high bandwidth...

Spoken in the voice of John Wayne, "You think a gigahertz would do it, pilgrim?"

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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3 hours ago, GeneZ said:

  

 

Could a tube possibly switch that fast with precision?  ...............    :scratch:

 

 

 

They use them in microwaves.  

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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12 hours ago, GeneZ said:

  @ a  switching frequency to 600 KHz? 

At higher frequencies than that.

 

Tubes aren't inherently low bandwidth. Transformers can be limited in bandwidth.

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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6 hours ago, GeneZ said:

  What kind of tubes would be needed in a class D amp?    Are these for output?  KT88's?  What are we talking about?  🧐

All depends upon the designer. 

 

David Berning has made amps for years that have switching supplies and a carrier frequency based OTL use on the output section.  Here is one using 211's providing 60 watts of power. 

http://davidberning.com/products/zh_211_845

 

A more powerful version. 

http://www.hifiplus.com/articles/the-david-berning-quadrature-z-mono-power-amplifiers/

 

Another good review.

https://www.soundstageultra.com/index.php/equipment-menu/442-david-berning-company-zh-230-stereo-amplifier

 

They are reputed to be very easy on the tubes with long life as well.

 

You could read his patent of how he does this.

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=5,612,646.PN.&OS=PN/5,612,646&RS=PN/5,612,646

 

Or read about Berning's products.

http://davidberning.com/

 

 

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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2 hours ago, GeneZ said:

I do not think even with supplementing with my monthly SS check could I cover that....

 

I guess I need to just depend on having a good dream about having one.

 

https://www.usaudiomart.com/details/649246104-berning-28-wpc-triode-zotl-quadrature-z-mono-amplifiers/

I'm not sure of the actual relationship.  But this company has rights to produce Berning designs at much lower cost. 

 

https://www.lineartubeaudio.com/power-amps/

 

They appear to generally be lower powered,though one is 40 watts, and a little lower spec'd performance, but still the basic Berning kind of amplifier circuit. 

And always keep in mind: Cognitive biases, like seeing optical illusions are a sign of a normally functioning brain. We all have them, it’s nothing to be ashamed about, but it is something that affects our objective evaluation of reality. 

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