Hhmmm... what is better at $900 ?
I see a SNR of 90dB is good here. But when I look at manufacturers spec of many amps they all have more than 100 dB.. some vintage amps claim 110dB. So are they all false claims or on a special occasion they hit value ? Like peak power?
I see that you have Klipsch Forte III speakers which have a sensitivity of 99dB and are rated for 116dB continuous output. 20 years ago, I could drive my old Forte II's to ear-splitting levels with a 3wpc single-ended 2A3 tube amp.
I do believe that your Audiophonics amplifier with its NCore NC250MP modules is not likely to reach clipping levels in your system!
Plenty of small companies will build them for you. Audiophonics, Rouge, KJF, Nord, Apollon, VTV and IOM were what I took into consideration but there is bound to be more. I wanted a 12v trigger input, EMI/RF rejection on the power inlet and shipping from inside the EU and it was very easy to find a good feal among them.mostly kits - some like DIY others don't
I owned a second, larger system with the Forte II's for the 2.5 years (2003-2005) that I lived with my late partner in her house with a large, high ceiling (15 peaked ceiling) prior to her passing. It was mainly a sentimental purchase based on memories of my first tube amplifier + big bass reflex mono system while still in high school in 1958. I still owned my older Bryston integrated + Apogee Centaurus Ribbon monitor system - in the dining room - and returned it to duty as my "main" system after my partner's family sold her house, and I moved into a much smaller apartment.I see a lot of people drive the Forte with tubes. Any particular reason you do?
I wonder if there is a a reason for difference in specifications between 1 watt and 5 watts and full power (or 2V out), also 8 ohms and 4 ohms?
That's correct. This is the reason I measure at 5 watts than 1. Otherwise "distortion+noise" would just be noise.Someone correct me if I am wrong, but the random noise/hum/etc. that many components in the circuit produce is present even with no signal. It's the same amount of voltage, regardless of output level...so that noise is a higher percentage of the total output when the output power is low, and a lower percentage when the total output is near maximum power.
Today's amplifiers produce far more power anyway so 5 watts today is what 1 watt was back in 1960s....
I don't see any replies addressing the part of your question about A-weighting, so I will give it a shot. A-weighting measurements use a filter that discounts noise components at frequencies where human hearing is less sensitive. So this results in a higher SNR figure than unweighted.For the NAD C268, the spec sheet (https://nadelectronics.com/wp-content/uploads/2017/10/NAD-C-268-Data-Sheet.pdf) lists under ANALOG AUDIO INPUT/LINE OUT, Signal-to-Noise Ratio >110 dB (IHF; 20 Hz – 20 kHz, ref. 2V out). Under ANALOG AUDIO INPUT/SPEAKER OUT, it lists Signal-to-Noise Ratio >98 dB (A-weighted, 500 mV input, ref. 1 W out in 8 Ohms).
Amir states "Here is our usual dashboard where we feed the amplifier a simple 1 kHz sine wave/tone and ask it to produce 5 watts into 4 ohm load (typical for many speakers). This is what we get:"
Then he lists SNR ~95 dB at 5 watts, 107+ at full power.
For reference, the top-rated SINAD amplifier at ASR seems to be the Benchmark AHB2 (https://www.audiosciencereview.com/...and-measurements-of-hypex-nc400-diy-amp.5907/), which has a SNR of 120 dB "Using near max power."
I wonder if there is a a reason for difference in specifications between 1 watt and 5 watts and full power (or 2V out), also 8 ohms and 4 ohms?
Can you show/explain this a little more so that stupid people (me) can understand how and why that's the case?For FFT’s I much prefer to use dBv on the vertical scale rather than dBr. dBr is relative to the output fundamental test frequency. The 60hZ, 120hZ and …….. series measured in volts or dBv are much more meaningful it terms of can I hear the power supply series of tones in my headphones or speakers
First, there's a big probability your speakers aren't "4Ω", neither 8, for that matter. Speakers impedance is a variable value depending on frequency. Manufacturers spec their products in a very misleading way: "nominal impedance", being often far from the real minimal impedance measured. Knowing which speakers you're talking about would be useful to find any measurements of them out there.Advice needed!
The manual on C268 says it is not recommended to drive speakers with impedance less than 8 ohms. But most of my speakers are 4ohms. Any real issue or danger to use 2 C268 on bridge mode to dirve 4 ohms speakers?
Anyway, being honest, I really don't see the point to get two of these NADs (2X 900$) when amps such as Ncore NC502MP or dual NC500MP exist... Cheaper, cleaner, and not limited with under-8Ω impedance.Not allowed. Minimum impedance is 8 ohm in bridged mode.
First, there's a big probability your speakers aren't "4Ω", neither 8, for that matter. Speakers impedance is a variable value depending on frequency. Manufacturers spec their products in a very misleading way: "nominal impedance", being often far from the real minimal impedance measured. Knowing which speakers you're talking about would be useful to find any measurements of them out there.
But, let's face it: I don't know any consumer speakers having at least 8Ω minimal impedance.
Anyway, being honest, I really don't see the point to get two of these NADs (2X 900$) when amps such as Ncore NC502MP or dual NC500MP exist... Cheaper, cleaner, and not limited with under-8Ω impedance.
Unfortunately, that's not a good option at the price. This is old UcD Hypex design (that still perfoms well, according to @amirm measurements). You may get next generation, and better performing Ncore amps for less. Depending of where you live, you could get March Audio P502, VTC NC502, Hattor NC500 monoblocs, Audiophonics HPA-S500NC, and so on... All are performing better, though cheaper, than two C268 bridged and don't have the minimum-8Ω-concern.I want to try class D. So that's why I'm consider 2 nad as good option at the that price.
Can you show/explain this a little more so that stupid people (me) can understand how and why that's the case?
Thanks for the clarification about A-weighting!