ST-10 Questions

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givemegut

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ST-10 Questions
« on: 24 Feb 2017, 04:51 pm »
I received my new ST-10 yesterday and I have a few questions. The User's Manual says "Goodbye, heat", but this amp gets very warm, almost as warm as my Ragnarok integrated. The ST-10 replaces a Bel Canto REF150S which barely got warm even after hours of play. Is this normal. Also, I have not been able to find any info as to powering the amp down after use. Should I leave it on 24/7 or switch to standby when not in use. Thanks for any answers.

mresseguie

Re: ST-10 Questions
« Reply #1 on: 24 Feb 2017, 05:06 pm »
Hello, givemegut.

I've owned an ST-10 for a few months now. I also own an IDA-8 which was purchased before the ST-10.

Compared to my IDA-8, the ST-10 actually runs fairly cool in my opinion. Both are designed to dispel heat directly through the outer case without a fan or vent holes. When I first began using the IDA-8, I was alarmed by how hot it was, so I shot emails off to both Jason (rustydoglim) and John Casler. They both assured me nothing was amiss and that everything was fine. I quickly got used to it to the point that I don't even think about it anymore.

I always turn my unit to standby mode after each use if only to conserve a few watts. The only times I've shut it off completely were when we left the house for a few days or a week (or more).

There's actually a quite long thread in this circle in which many people share their impressions of the ST-10 - including their initial reactions to heat, and whether to power down after use.

Michael

givemegut

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Re: ST-10 Questions
« Reply #2 on: 24 Feb 2017, 09:50 pm »
Thanks for the input. Do any other NuPrime amp owners switch to standby when not listening. I have always thought that it took at least a few hours for an amp to stabilize and sound its best after switching out of standby.

JackD

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Re: ST-10 Questions
« Reply #3 on: 24 Feb 2017, 10:33 pm »
Mine stays powered up all the time.

zapper7

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Re: ST-10 Questions
« Reply #4 on: 25 Feb 2017, 12:25 am »
I leave mine on all the time and it does get quite warm too.

givemegut

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Re: ST-10 Questions
« Reply #5 on: 25 Feb 2017, 10:43 pm »
Unless someone from NuPrime sees this thread and tells me different, I'm going to leave my ST-10 on 24/7. Thanks for all the response.

John

Mic

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Re: ST-10 Questions
« Reply #6 on: 27 Feb 2017, 03:03 pm »
I have one at home for testing.

It also gets somewhat warm.

Mosty what annoyes me is that there is a litle hissing from my speaker tweeters when using this amp.

Do any of you other owners have the same hiss ?

triumph

Re: ST-10 Questions
« Reply #7 on: 28 Feb 2017, 10:13 am »
My MCH-K38 hiss (well, more like an electrical high buzz) as well, but my speakers have 95dB sensitivity... quite a bit more than the run of the mill speakers out there...

rustydoglim

Re: ST-10 Questions
« Reply #8 on: 2 Mar 2017, 07:01 pm »
If you put your ear near the speaker, when there is no music playing, the amp is in an "unknown" state.
Our amps actually do not use external PWM signal for modulation. Instead, we use the music to create a modulating PWM signal (I know, this is too complicated to explain).  PWM modulation is fundamental to Class-D design.
Now, think about this for a second. If there is no music, what's going to happen to the amp? It is in an unknown state and usually you hear some noise.


rustydoglim

Re: ST-10 Questions
« Reply #9 on: 2 Mar 2017, 07:03 pm »
About heat issue - we conduct the heat to the top of the amp cover internally, and we don't use ventilation holes (unless you have a fan, this is a bad way to dissipate heat).  Hot air goes up, and better to conduct heat to the cover than to the bottom. That's why the top cover is hot. You are touching the heat sink.

Armaegis

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Re: ST-10 Questions
« Reply #10 on: 2 Mar 2017, 10:13 pm »
If you put your ear near the speaker, when there is no music playing, the amp is in an "unknown" state.
Our amps actually do not use external PWM signal for modulation. Instead, we use the music to create a modulating PWM signal (I know, this is too complicated to explain).  PWM modulation is fundamental to Class-D design.
Now, think about this for a second. If there is no music, what's going to happen to the amp? It is in an unknown state and usually you hear some noise.

Well this kind of begs the question... is it possible to somehow feed the amp a "zero" state when there is no music so it doesn't idle in the "unknown"? Or would such a sensing circuit interfere with the music reproduction?


About heat issue - we conduct the heat to the top of the amp cover internally, and we don't use ventilation holes (unless you have a fan, this is a bad way to dissipate heat).  Hot air goes up, and better to conduct heat to the cover than to the bottom. That's why the top cover is hot. You are touching the heat sink.

I believe I've mentioned this here a couple times before as well. People think putting in vent holes will help cool down a surface, but this only works if air is actively being moved by a fan or some other external force, and even then only if there is a source for cool air to flow in to replace the hot air leaving. Passive convection at the temperatures inside an amp is extremely slow. Air itself is also a very poor conductor if heat.

So here's where the tradeoff takes place. Metal is very very good at moving heat. It practically "sucks it up" and moves it around the chassis/heat sink further away from the heat source. In this case NuPrime is using the case itself as a heat sink to move heat to the furthest edges of the body. If you put in ventilation holes, you get a very marginal increase in convection as heat can flow out of the chassis, but this flow is very slow. BUT putting in those holes means you lose conductive surface with which to pull the heat away. So you gain some and you lose some and you need to do some very fiddly number crunching or empirical testing to figure out which works better (or if the change is really worth the effort).

One very nice benefit of a closed chassis is no need to worry about dust inside, which is very bad for heat conduction.

rustydoglim

Re: ST-10 Questions
« Reply #11 on: 4 Mar 2017, 07:39 am »
Quote
Well this kind of begs the question... is it possible to somehow feed the amp a "zero" state when there is no music so it doesn't idle in the "unknown"? Or would such a sensing circuit interfere with the music reproduction?

It doesn't work like that. Take a look at the illustration on this page:
http://www.nuprimeaudio.com/index.php/guides/learning/amplifier-design-sonic-characteristic.html
See the "Triangular Wave Generator" ? That is the PWM signal that is generated from an external chip for conventional Class-D design.
NuPrime doesn't use this method!!!
The PWM signal is created using the MUSIC through a natural phenomenon called "self oscillation". Think of your music as the "spark plug" of your car. This self oscillation circuit needs music to "start the engine". Why is this implementation better? Because if you use external PWM chip, then you are stuck with whatever maximum sampling frequency that the PWM chip gives you.

This is the key to why Nuprime's amp is getting smoother and better sounding every year. We keep improving on this "engine" and now it runs at 600kHz, almost 15 times the CD quality. In our lab, we can crank it up to 1GHz and wow, that takes the sound to another level. I think there is very rare class-D amp that runs at this frequency but I recall it would cost $50K.  What we are trying to do is eventually bring this level of performance to < $1K. It is not an easy task obviously otherwise everybody will be doing it.  The rest of the circuit would have to change too. But I think we will get there in 2018 - a super amp that cost < $2K.


mresseguie

Re: ST-10 Questions
« Reply #12 on: 4 Mar 2017, 03:36 pm »

This is the key to why Nuprime's amp is getting smoother and better sounding every year. We keep improving on this "engine" and now it runs at 600kHz, almost 15 times the CD quality. In our lab, we can crank it up to 1GHz and wow, that takes the sound to another level. I think there is very rare class-D amp that runs at this frequency but I recall it would cost $50K.  What we are trying to do is eventually bring this level of performance to < $1K. It is not an easy task obviously otherwise everybody will be doing it.  The rest of the circuit would have to change too. But I think we will get there in 2018 - a super amp that cost < $2K.

If this becomes the super duper 2-channel K-38 that I asked about a while back, I would be very interested.  :)  I'll send the engineering team a 5 lb bag of coffee beans, a new coffee maker, kimchi ramen, and dancing girls to encourage them to work faster. Go team go!  :thumb:

Armaegis

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Re: ST-10 Questions
« Reply #13 on: 4 Mar 2017, 05:57 pm »
It doesn't work like that. Take a look at the illustration on this page:
http://www.nuprimeaudio.com/index.php/guides/learning/amplifier-design-sonic-characteristic.html
See the "Triangular Wave Generator" ? That is the PWM signal that is generated from an external chip for conventional Class-D design.
NuPrime doesn't use this method!!!
The PWM signal is created using the MUSIC through a natural phenomenon called "self oscillation". Think of your music as the "spark plug" of your car. This self oscillation circuit needs music to "start the engine". Why is this implementation better? Because if you use external PWM chip, then you are stuck with whatever maximum sampling frequency that the PWM chip gives you.

Ok I get that... but earlier you said this: "If there is no music, what's going to happen to the amp? It is in an unknown state and usually you hear some noise."

I took this to mean that when there is no signal, the amp self creates a bit of noise floor due to being in the unknown state, but once there is music then the noise disappears. Is this assumption correct or am I misreading? Because if this is the case, would it be possible to create a sensing circuit that will feed the input a "zero" when there is no signal present?


rustydoglim

Re: ST-10 Questions
« Reply #14 on: 9 Mar 2017, 08:25 am »
This is not a digital design, i.e. not a computer. It is analog!
We can't just put some known state in it, unless we internally generate a sine wave as music, but that will unnecessarily add cost (and perhaps its own noise) with no benefit whatsoever.

Genez

Re: ST-10 Questions
« Reply #15 on: 10 Mar 2017, 07:44 am »
deleted...
« Last Edit: 11 Mar 2017, 03:25 am by Genez »

Genez

Re: ST-10 Questions
« Reply #16 on: 10 Mar 2017, 04:46 pm »
Ok I get that... but earlier you said this: "If there is no music, what's going to happen to the amp? It is in an unknown state and usually you hear some noise."

I took this to mean that when there is no signal, the amp self creates a bit of noise floor due to being in the unknown state, but once there is music then the noise disappears. Is this assumption correct or am I misreading? Because if this is the case, would it be possible to create a sensing circuit that will feed the input a "zero" when there is no signal present?

I believe what happens with the hiss can be likened to what I learned about the SR-71 Blackbird...  when on the ground and idling, it leaks fuel vapors.  It needs to be run.  Once in motion at lightening speeds everything tightens up and seals what had been leaking.  I believe a similar thing happens with this design of amplifier. Once playing music what you get is the music only. It does not like to sit around doing nothing. Its not lazy.  ;)

Genez

Re: ST-10 Questions
« Reply #17 on: 10 Mar 2017, 04:48 pm »
This is not a digital design, i.e. not a computer. It is analog!
We can't just put some known state in it, unless we internally generate a sine wave as music, but that will unnecessarily add cost (and perhaps its own noise) with no benefit whatsoever.

I believe this may lead into the question I have been having about the uniqueness of this design.  If I am using a line conditioner?   And, it has different isolated outlets with designated filtering for components of different types. Would it make any difference if I plug in the ST-10 into a socket designated for typical amplifiers?... Or, should I choose a socket designated for digital components such as for DAC's and the like?   How is it effected the filtering?    Just plug it in where a regular analog amplifier would normally plug in?   


« Last Edit: 10 Mar 2017, 08:16 pm by Genez »

rustydoglim

Re: ST-10 Questions
« Reply #18 on: 11 Mar 2017, 07:16 am »
If your power conditioner has higher filtering designed for analog circuit and less for digital, then treat Class D amp as digital as far as the power conditioner is concerned. Class D design is by nature much noisier than pure Class A design. It took more than a decade for engineer to figure out how to reduce the noise and increase the switching frequency to the point where noise has significantly reduced and made irrelevant.  If you recall, in the early days, Class D amps were publishing 0.1% THD+N and then people started to brag about 0.05% and then 0.01% was like a very big deal, since it was approaching Class A's THD+N. 
But now who cares? Because even a low cost NuPrime amp can achieve 0.005% THD+N.  By the way, you can't hear the difference as the THD+N goes below 0.05%.  It has become so low that the instrument can't measure it.  And in some design (Class A+D), we actually added back some "noise" as even order harmonics to make it sounded warmer.

Self oscillation is a naturally occurring phenomenon, see
https://en.wikipedia.org/wiki/Self-oscillation
So if a circuit is arrange in certain way, a sine wave started to appear.  In order to make the circuit oscillates, some external input (i.e. music signal) is required.  Over the years, we have been improving this circuit to the point where it can oscillate at 700kHz.  It is not easy to control this. Self oscillation circuit can become unstable (like spinning out of control) so it took many years to master this technique.  And that's the reason only a handful of high end Class D designs existed in the world. The analogy would be street legal sports car. There are very few (street legal) cars that can run at top speed of 200m/h for example. To make the engine, drive train run at that kind of speed, the tire design, aerodynamic etc all have to meet the requirement.  Likewise for amplifier circuit.

Genez

Re: ST-10 Questions
« Reply #19 on: 12 Mar 2017, 01:08 am »
Jason....    I LOVE how your designs sound. 

I am a musician and adore how the instruments will sound in a well placed system.  The sound is very alive and refreshing. 

.... I will tell you a secret that many never take the time to discover. 

I listen nearfield.  My small (phase coherent) speakers need some boost in the bottom. Placement of a subwoofer causes me perception problems.   Instead I use a BBE Sonic Maximizer.  I only use its linear dynamic EQ feature for the bottom end.  I leave its processing feature alone..  It uses a NJR Corp chip - NJM2153.  This chip is designed to make recorded music come alive through speakers.

Too many run from the idea because they think its a gimmick.  When used correctly, in an accurately set up system, its a revelation in sound.   BBE just discontinued the production of the desktop model... I read on their web page they do license out the technology.  Its for high end, but the way they had been marketing it made it look like a gimmick... It should be used in high end systems. With the NuForce/ NuPrime amps - (I have heard both) -  the BBE technology makes these amps leap alive!  Its like when the movie the  Wizard of Oz switches over to the Technicolor from black and white.  It sounds very alive when used with this amplifier technology...   VERY DYNAMIC. 

link to see...
https://www.amazon.com/BBE-Desktop-Maximizer-Unbalanced-Connections/dp/B00FRLB87Q/ref=cm_cr_arp_d_product_top?ie=UTF8