Do they benefit from power conditioners and power cords?
Its able to reject a fair amount of AC power line problems. A nice power cord if helpful if you push the amp hard. Its only going to draw serious power when its making power (true of all class D amps)- that's where a nice power cord will help. We've got no feedback on the use of power cords with the amp at this point, AFAIK everyone is using the stock cord.
I love my GaN amp, which is on 24/7 as is the rest of my system, but when not played > 12 hours, it sounds edgy/hard/glass-like. It takes a good 30 minutes of play time to smooth out.
Interesting. We don't seem to experience that, nor has it been reported. My personal experience is the amp sounds right as soon as its turned on.
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do they need break-in?
And if so, then how much?
It appears that they do from the feedback we've been getting. Apparently 100 hours or so.
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Put another way, we want the amp to be able to run at full power indefinitely.
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Can you make a higher power amp with this module or is it limited to output as designed?
We can, but we're holding it to a rather high standard: At present, the amp can sit at full power with a sine wave input all day long- something you simply can't do with a conventional solid state amp. We're looking into how far we can push that.
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Well, those inefficient speakers will flourish with more powerful and higher quality and affordable class D amps.
Maybe. But its a simple fact that with less efficiency comes more thermal compression. Its also a simple fact that if you make a power amp (any power amp) work hard for a living, its going to make more distortion.
That additional distortion is often audible as harshness and brightness. We've been hearing that for 60 years... IMO/IME if you want the best performance out of your amplifier dollar investment, its best served by speakers that are of higher impedance (8 Ohms being better than 4) and also easier to drive.
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Class D is about the needs for addressing increasing demand on our collective electrical supply. Not just quantity but, quality(s) and reliability, too.
This statement appears false. Class D offers the possibility of using loop negative feedback in a way that was previously not possible due to stability concerns.
Legacy solid state and tube designs lack the Gain Bandwidth Product needed to support very high amounts of feedback. This causes the amplifier to have increasing distortion with frequency, resulting in harshness and brightness since the ear assigns tonality to distortion.
In addition the prior art has issues with phase margins in the design. Adding too much feedback can cause oscillation. For these reasons feedback has gotten a bad reputation with music lovers.
Class D offers a way around those problems.
Last then there is the TCO (total cost of ownership). Is this approach really a sustainable business model? Is blending Tubes & GaFNET, Helper Circuits & Class D just greater uncertainty (Heisenberg/Schrödinger)?
'Apparently.' for the first. Your so-called 'Helper circuits' are class D modules so do not warrant a separate classification; the Ghent stuff uses Icepower modules so isn't a thing. So winnowing out that bit of confusion, the answer then becomes 'no'.
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I'm asking because I wonder if these 100 watt class D monos have enough testicular fortitude to drive <89 dB efficient speakers with grunt and authority. I would completely understand if you chose not to answer the above question ;)
Generally speaking I'm not a fan of low efficiency and hard to drive speakers. This is simply because the harder you make any amplifier work for a living, the higher the distortion, and with that distortion comes a less relaxed presentation (due to the generation of higher ordered harmonics) and less detail (since distortion obscures detail).
89dB is borderline low efficiency. A lot depends on the room and your listening habits as to whether 100 Watts is enough power or not. The speakers in my bedroom system are about 90dB and I play them with an amp that only make 5 Watts with power to spare, no worries. You have to take the room into account.
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Ralph, is your design a module like most of the others?
It is a module; because of noise concerns that's really the best way to do it.
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Would the dead time be more like, or analogous to, crossover distortion, slew rate distortion, or neither?
Neither. At least in our design, its responsible for lower ordered harmonics. We can see that there is a cubic non-linearity, as (like our tube amps) the 3rd harmonic (treated by the ear the same as the 2nd) is the dominant distortion product.
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At only 500Khz, what is the advantage of using GaN?
@kuribo
In a nutshell, reduced distortion and less heat than MOSFETs, not like that's much of a thing. The faster speed of GaNFETs requires less deadtime, which has to be increased at higher switching frequencies (when we first started doing this, I thought the deadtime would be constant regardless of the switching frequency and learned otherwise; either way deadtime becomes a greater distortion influence as you increase the switching frequency).
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There are many sources of distortion in class d amps, not only those you have mentioned, but also in the output filter. Do you use post filter feedback?
Yes.
Please share some measurements of the frequency response with load, THD+N with power and frequency, FFT's and IM. Also, can you share the switching frequency used? Lots of claims made here (not all by you) so it would be enlightening to see a more complete picture of how this amp performs in actuality, not how it sounds to those who haven’t heard it yet.
The frequency response is load invariant within 1/10db from 20-20KHz, with 0 degrees phase shift at 20Hz and less than 1 degree at 20KHz. The invariance due to the output impedance being a few milliOhms, the low phase shift due to the feedback value, which allows the amp to correct for phase shift at the bandwidth extremes.
THD from 20Hz- 20KHz is < 0.1% at full power (200 W into 4 Ohms) and about 0.005% at 1 watt. We think it might be lower but finding a decent filter to knock out the residual has been tricky during the pandemic. We found one about a week ago and are interested to see how things differ once its integrated into our test setup. The distortion is lower into 16 Ohms.
The switching frequency is just shy of 500KHz, depending on load. The input is entirely direct-coupled.
The filter I mentioned is an Audio Precision device and is used to knock out the residual to prevent it messing with the distortion analysis. If I got this right its 8th order(!) and puts the residual down about 60dB... This is why we've not posted any more distortion data since the residual throws the readings off.
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I wonder how well this new product will work with 16 ohm speakers? Sure, it will work, but, how effectively. This is a surprise for folks who have cherished the OTL designs for use with 16 ohm speakers.
My speakers at home are 16 Ohms as well as our speakers at the shop. Any amp driving 16 Ohms will have lower distortion.
So he is adding distortion to please a certain group of people? And those who don’t prefer his particular distortion preference, not so much.
@kuribo In most class D designs, the distortion sources in the design are caused by dead time and non-linearities in the encoding scheme. In our design these result in lower ordered harmonics- its not been tailored.
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Anyone?Are they all basing it off of the standard “Bruno parts”?
@holmz No. The amp uses a module of our own design. I don't see why it could not be used in a bi-amped system.
will you, like Bel Canto now discontinue or gradually phase out your tube based models?
Its way to early to say. One big difference between our tube amps and the class D is the latter behaves as a voltage source with an output impedance of only a few milliOhms. Our tube amps are designed to be instead a power source, meant to work with speakers of higher impedance or speakers that aren’t voltage driven, like most ESLs. http://www.atma-sphere.com/en/resources-paradigms-in-amplifier-design.html
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I wish you even greater success in the new year with them.
Thanks!
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Where did he get the amp if it's not even on the website?
We're doing limited production and the product page isn't yet up.
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