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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

 

It all depends upon in what dimension of life one finds themselves living in.  For, one man's music is another man's noise. 

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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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52 minutes ago, esldude said:

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. 

 

 

What speakers?

It all depends upon in what dimension of life one finds themselves living in.  For, one man's music is another man's noise. 

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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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52 minutes ago, esldude said:

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. 

 

 

Its not only Nuprime.   Class D amplifiers in general.  REL has instructions for ALL Class D amplifiers,  not just Nuprime.   Its like buying a car with a diesel engine having a warning not to use regular gasoline/petrol.

It all depends upon in what dimension of life one finds themselves living in.  For, one man's music is another man's noise. 

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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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11 minutes ago, GeneZ said:

...
High output current drive capability for low impedance speakers.

...

 

Hum, interesting marketing claim.  "Normally" this claim is made around current delivery doubling down for each halving of load (e.g. if 100w at 8ohm, then 200w at 4ohm, and so on).  NuPrime does not do anything like this, so what is the basis and thinking around this claim I wonder. 

Hey MQA, if it is not all $voodoo$, show us the math!

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6 minutes ago, esldude said:

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. 

 

Hah, we were responding at the same time.  I was thinking of Maggies and the like that NuPrime might be good with.  Dynamic speakers, at least the majority of all the usual suspects, would not appear to be the best fit for NuPrime.  Of course, this is Audiophiledom so as long as you like it then...  ?

Hey MQA, if it is not all $voodoo$, show us the math!

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51 minutes ago, GeneZ said:

 

 

Its not about just Nuprime. Nuprime simply makes it known.  Class D amplifier design, by default, causes problems with REL Subwoofers.

 

Look at the REL page and look up about hooking up Class D amplifiers. https://relsupport.zendesk.com/hc/en-us/articles/115004486607-Class-D-Amp-Connection-Methods

 

About 10 years ago or more Rel addressed this with a cable they include.

 

Having said that, there are plenty of other reasons to avoid Rel (like spontaneous combustion).

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2 hours ago, esldude said:

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

 

 

 

Everybody owns those and drives them with their Sony receivers.  My mom used to have those in the kitchen.

 

Come on folks!    These speakers would give many amplifiers problems, and most people would not own them to begin with.  :scratch:

 

 

Now.. Interesting point concerning amplifier phase shift:

 

According to the manufacturer, NuPrime amps have no phase shift. Many amps use output filters that create phase shift. When phase shifts, spatial information becomes inaccurate. Most amps present phase shifts of better than 45 degrees at 20 kHz, heading toward 90 degrees as frequency increases. NuPrime amps cancel these distortions owing to a unique closed-loop design producing ZERO phase shift across all frequencies.

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

 Note:

 

The reviewer of the ST-10 used Wilson Sabrinas.

It all depends upon in what dimension of life one finds themselves living in.  For, one man's music is another man's noise. 

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I have owned a few Class D amps- the first was the PS Audio HCA-2.  Next up was the Bel Canto Ref 500 and then a preamp, the Jeff Rowland Capri.  I liked them all.  I preferred the Bel Canto to the PS Audio, but perhaps not a fair fight as the Bel Canto was a newer design.  Treble was better with the Bel Canto (more natural, less etched, relatively speaking).  

 

The Jeff Rowland Capri is a seriously good preamp at a relatively reasonable asking price.  I loved the small form factor. As compared to running DAC direct to amp, versus preamp to amp, it was difficult to detect any degradation in transparency when inserting the Capri, perhaps just a very tiny bit, however, I felt that sound staging improved with the Capri in the chain, and the notes had a more round or three-dimensional quality.  So overall I definitely preferred having the Capri in the chain, vs DAC direct. 

 

Home: Melco N1A/2 | EtherRegen+Farad | UltraRendu+Farad | Denafrips Gaia | Denafrips Terminator Plus | Jeff Rowland Coherence II Series 2 pre | Blue Circle Audio BC-202 amp | Raidho XT-1 | 2 Revel Performa3 B112 subwoofers  | PS Audio DS Power Plant 12 

Home Office: IsoRegen+LPS1.2 | Denafrips Iris | Denafrips Venus 2 | Blue Circle Audio SBT preamp|  Eddie Current Zana Deux Super | Hifiman HE-1000SE | PS Audio DS Power Plant 12

Office:  Holo Audio Spring 3 KTE w/preamp module | Blue Circle Audio BC-28 amp | Raidho X-1 | REL T/5x sub

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On 3/25/2018 at 10:43 PM, Nordkapp said:

Now, I once owned an incredible amp designed by Demain Martin and Richard Marsh-Marsh Sound Design. It was a 100 watt AB. That amp was amazing on all levels. I've owned some other tube stuff as well but always found it too billowy and slow. My current CIAs with Hypex Ucd modules tick all the boxes for me. But it all comes down to personal preference. For me they work. That's it. 

 

Off topic, but I owned the Marsh A200s.  That was a damn good amp!  

Home: Melco N1A/2 | EtherRegen+Farad | UltraRendu+Farad | Denafrips Gaia | Denafrips Terminator Plus | Jeff Rowland Coherence II Series 2 pre | Blue Circle Audio BC-202 amp | Raidho XT-1 | 2 Revel Performa3 B112 subwoofers  | PS Audio DS Power Plant 12 

Home Office: IsoRegen+LPS1.2 | Denafrips Iris | Denafrips Venus 2 | Blue Circle Audio SBT preamp|  Eddie Current Zana Deux Super | Hifiman HE-1000SE | PS Audio DS Power Plant 12

Office:  Holo Audio Spring 3 KTE w/preamp module | Blue Circle Audio BC-28 amp | Raidho X-1 | REL T/5x sub

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On 4/7/2018 at 11:04 PM, Ralf11 said:

Right !  I put no $$ restrictions on it, but as a 2o issue, I am collecting a list of amps to replace my old Sunfire with, and would like to economize, partly just to fulfill my Cheapskate expectation bias...

 

So far, I think I'll rule out the Vidar (hum issues)

 

List includes:

PS Audio (Class A to D) $1,500

Benchmark ("magic" AB) $3,000

 

Ralf,
in fulfillment of your cheapskate eb ...
why don't you have a look on the XTZ ADGE A2-300, which also uses the output board from ICEpower,
afaik  1x Icepower 300AS1plus 1x Icepower 300A1, which could be used as mono-mode as well. Price in Europe, short of 500 Euros. Some raving reviews are to find, but also a lot of satisfied owners in some European hifi fora. IMHO, their p/q ratio is the trigger, the reported weakness had been found in the top heights ...
XTZ Edge
cheers, Tom

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On 11/24/2018 at 9:00 PM, jmpsmash said:

The NuPrime Evoluion One looks fantastic. But unfortunately out of my budget.

 

The ST-10 however, look more in my ball park. My dilemma is whether to just fix the Hypex NC400 and keep it, which cost around $400 or so, or try the NuPrime ST-10. Anyone have comparison of those two?

 

Looks like my option so far is one of:

- fix Hypex

- NuPrime ST-10

- PS Audio Stellar M700

 

 

 

Did a bunch more research online. I am throwing into the mix a couple more amp/modules and my options:

 

- fix Hypex (I already ordered a new module, I need to fix it and in the worse case, sell it)

- NuPrime ST-10

- NC500 - the popular ones have either a Sonic Imagery or Sparko opamp input stage

- ICE Power 1200AS2 module - this is relatively new from early this year. Most review rank these in par with NC500 at just above 1/2 the cost

 

Tough choice. Wish I can get all of them and compare! These are all in the region of US$1k -> $2k

 

 

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50 minutes ago, barrows said:

Hypex amps have no such issues with high level sub connection as the "black" speaker output is ground. Additionally, there are simple ways to hook up a sub via high level input to a balanced output amplifier, this is not really an issue At All!  And it is not about Class D, it is about balanced output amplifiers, you just cannot connect the "black" speaker terminal of a balanced output amplifier (could be class D, could be class A, could be class A/B, whatever) to ground without creating issues.

  Good to know....

 

Paul McGowan said that PS Audio amps need the special REL hookup.  That's where I first learned about it.

 

Yet,   REL made a special video for Class D amplifier hook ups in general. 

 https://relsupport.zendesk.com/hc/en-us/articles/115004486607-Class-D-Amp-Connection-Methods

It all depends upon in what dimension of life one finds themselves living in.  For, one man's music is another man's noise. 

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Found Nuprime's official word on REL subs.

 

 

 

In some applications, the speaker outputs from the power amplifier are used as source signals for devices such as REL sub woofer. For such application, usually the receiving devices should have DC offset blocking capability because some amplifier by design has floating ground (DC offset) on the speaker outputs.

The following models have no DC offset on the amplifier speaker outputs and the negative terminal is also the ground:
NuPrime STA-9, MCH-K38, IDA-6, IDA-16

The following models’ speaker outputs can not be connected directly to sub woofer input:
NuPrime Reference 20, ST-10, IDA-8

REL has provided instructions for connecting Class-D amp with floating speaker outputs to their sub woofers, please contact REL.

It all depends upon in what dimension of life one finds themselves living in.  For, one man's music is another man's noise. 

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On 11/25/2018 at 6:46 PM, jmpsmash said:

@mocenigo Yes. I agree. I understand the NC400 is for hobbyist with the input stage while the NC500 is the OEM one designed for that exact usage you mentioned. 

 

Yarp. Now, hypex also commercialises a simple input buffer that was initially meant for evaluation purposes only, in order to evaluate the NC500 - but some manufacturers have used that same buffer in finished products that were sold for a few thousand bucks. That buffer is horrible. I believe it contributed, in part, to the reputation of harsh sound and bad highs that in some circles Class D amplifiers still have (Class D does have some limitations - esp going to low and/or very capacitive impedances).

 

A DIYer community developed a modified version to allow opamp rolling, and engineering at companies like Sonic Imagery and Weiss helped by designing better versions. The no-longer very recent wave of amps from Nord, Apollon, and others, use those buffers, and it is in another league. I have Apollon mono blocks, which I chose after carefully evaluating the materials used and the design approach (including the placement and orientation of the PSU, for instance) and I cannot repeat enough how much I am happy with my choice.

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46 minutes ago, wgscott said:

I use a class D amp to power my pencil sharpener:

 

 

Screen Shot 2018-11-27 at 7.16.04 AM.png

 

Yea, but it leaves the graphite grainy and the words come out soulless...

Hey MQA, if it is not all $voodoo$, show us the math!

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