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It would be interesting to see a more sophisticated 300B implementation. As Pavel mentioned above, the power supply scheme is very pretty noisy. From the teardown photos, it's a very simplistic CRC implementation. Filaments on DHTs are very sensitive - not sure how much care was given there...

The first is likely to sound noisier even with reasonably efficient speakers. The 86dB peak at 120Hz as well as the spray of noise from 200-2k a centered around -100dB (+/-) will be audible with ear against the speaker. The second is around 10dB less noisy and from my experience once you’re in...

@amirm how is that you are showing SNR at 5W at 96dB but the FFT also at 5W showing a lot of spikes higher than 90dB. 120Hz is peaking around 86dB for example. Perhaps in misinterpreting

are we confusing missing fundamentals with difference tones/beat frequencies?

Hi @amirm , could you take a measurement of the switching noise level and frequency?

What would happen if you rotated a speaker such as this 90 degrees, so that the bass driver is on the bottom and tweeter + midrange at the top? Would there be lobing, and other negative results? I have a similar configuration speaker myself (compact 3-way, identical placement of drivers...

Definitely we shouldn't accept questionable design choices and poor FR for such a high dollar. I was partially being facetious with the recommendations. But if you picked them up second hand cheap, it's amazing what some sub integration and DSP can do when done properly. There's a pair on Ebay...

Plug the port with some foam, to get rid of the resonances, cross with subs to cover the low end, send it through DIRAC to clean it up and integrated the subs properly. That should about do it, right?

With respect to the mains noise, it’s really hard to get lower than -100 dB/V with a normal linear power supply. I’ve built a few power and preamps with both linear and smps, and smps is always way quieter. This despite all the praise/scorn of linear/smps.

I don’t think there are any magic two sentences. Rather I think a video for beginners about voltage and current that uses a lot of imperfect analogies would help people to understand the nature of electricity and its terms. And from there people can get a more intuitive understanding. A little...

I think Amir was trying to tailor the video to audio consumers, and in an effort to dumb it down, the way current and voltage are described is not 100% accurate. I used to design exhibits for science museums, and did quite a few solid state high voltage static electricity exhibits in the range...

Of note is that 16 out of 20 blue "excellent" amplifiers in terms of SINAD, are either Hypex or Purifi (Bruno P) based. The 4 within this category that are not are the Benchmark AB, Topping PA5, Neurochrome Modulus, and SMS VMV. Just interesting is all.

Agreed. But even without ASR, with just s few hundred $ of investment and a bit of time, it’s possible for anyone to confirm the accuracy of some of these basic specs down to 100dB of dynamic range (below that it gets harder). So hopefully the pendulum has now swung in the people’s direction.

The whole hifi industry relies on a hope that the consumers stay ignorant. Even after people finally get this power thing, next stop SNR. Oh, you were using dBV? I was using dBFS or dBW. Oh you mean dB 1 watt for 8 ohms ? No I was using dB Wampum which is DbW, silly mistake this stupid shift...

Haha, too many peaks these days lol. I know your being tongue and cheek and it’s a good joke, but it raises an interesting point…. That peak refers to the power as calculated using the peak V of the sine wave that the amplifier is able to output into a fixed R (vs the average power from that...

The problem with AirPlay is the attenuation. My understanding is that the attenuation is all done at 16bits, so you lose a lot of resolution as you go down in volume when controlling with a phone. Streamers usually resample at 24 bits, so instead of 65k lines of resolution to scale volume, you...

Love seeing these classic amps reviewed! Thanks to whoever sent it. It’s over 60 lbs from what I’ve read. Incredible!

It actually looks like there are a few threads already for speaker measurements, although they look more like in-room rather than close mic or gated. It can’t hurt to put whatever you have in here, but I was originally thinking this thread could be used more for amplifiers or preamps.

I'll start. This was a version of the First Watt F5, as designed by DIYA member Juma: https://www.diyaudio.com/forums/pass-labs/168040-f5-2sk2013-2sj313.html My version runs at +/- 15V, so max about 10W RMS. I used a SMPS to keeps things light(ish) It was tested on an Quantasylum QA400, (ASR...

I propose this thread for all the diy'ers out there who have measured their gear. There are some threads over on DIYA, but they are scattered about, so thought this would be a good alternative to create a consolidated record of some of our projects. Let's keep this thread as straightforward as...