I also think you need to look at the time base used for the actual graphs @fireanimal produced. Kind of like comparing apples to oranges. I seriously doubt the frequency analysis examples used a 1uS/div time base.
Yes, SACD, which is DSD 64, if well recorded sounds great but one requires a good amp and even better speakers. DSD 256 is the highest quality recording I ever listened to (there is also DSD 512 and 1024) and it was truly impressive. A friend of mine has top Electrocompaniet PA (very fast and damping rate of about 1600), electroststics supported by active sub so that's what one needs to get the best of truly good high resolution DSD recordings. Alternativly to good electroststics one could use bands of ribbons or planars for Mid and High frequencies . My fastest amp is Stochino (300v/us) but its distortion levels are not impressive and as I do not have electroststisc nor bands of ribbons (my fastest tweeters are two pairs of planars) I can't get the best of the best recordings. Nevertheless I'm waiting to hear what this great amp will bring into the sound of my music. Once it's built I'll take it to my friend's place and connect it to his speaker system and we will compare Wolverine to Electrocompaniet. It'll be an interesting experience.
cheers,
Are you sure about this measurement #1655? 2nd harm. -145.3 dB ??? That's rarely achieved by a very good op amp. I can't imagine that with a power amplifier with an 8 ohm load.
No I love to post false measurements. Yes its verified and repeated multiple times, I was 100% sure it was correct before it was posted on here. I have worked for almost 6 months on my measurement setup just to be able to measure the Wolverine accurately. In fact as you can see, I am sure the THD is actually better, but I do not have the equipment to extract it from the noise floor.
Goodies,.....still a bit early to worry about those 2 mf's but glad they are in at least. I saw the example powersupply scheme in the documentation and these 2 are at the basis of it. I do have the quasimodo jig to determine the R value for the 4 snubbers I have to add.
The Wolverine boards should be ready in 1 to 2 weeks after which I need to start testing and I do have a few questions on the test-setup. I've read all the notes and remarks of Stuart mainly but just want ot make sure of a couple of things.
- Is the normal way of testing using the power-supply I still need to build in conjunction with a dim bulb tester at the AC part and lower value fuses at the PCB part?
thx in advance
w.
The Wolverine boards should be ready in 1 to 2 weeks after which I need to start testing and I do have a few questions on the test-setup. I've read all the notes and remarks of Stuart mainly but just want ot make sure of a couple of things.
- Is the normal way of testing using the power-supply I still need to build in conjunction with a dim bulb tester at the AC part and lower value fuses at the PCB part?
thx in advance
w.
I did a back-of-the-envelope calculation that gives the same THD as the measurement. This amplifier is easy to analyze. 
Open-loop gain = 92e3
Closed-loop gain = 29
Negative feedback = 70dB
Open-loop output stage THD: -70dB (from my THD simulator)
Closed-loop THD: -140dB
The calculation is below:
The output stage already has low distortion with Re=0.22ohms and four pairs of transistors. Then, 70dB of negative feedback is applied.
Ed
Open-loop gain = 92e3
Closed-loop gain = 29
Negative feedback = 70dB
Open-loop output stage THD: -70dB (from my THD simulator)
Closed-loop THD: -140dB
The calculation is below:
Code:
// wolverine
// compute thd of wolverine at 8 ohms and 1KHz
// Copyright © 2023 Ed Grochowski
ic1=0.7/200/2;
gm1=ic1/0.02585;
xc=1/(2*3.14159*1e3*47e-12);
vgopen=gm1*xc/(1+gm1*22);
vgclosed=22e3/(1/(1/1e3+1/3.9e3))+1;
nfb=20*log10 (vgopen/vgclosed);
thdopen=20*log10 (.0003);
thdclosed=20*log10 (.0003/vgopen*vgclosed);The output stage already has low distortion with Re=0.22ohms and four pairs of transistors. Then, 70dB of negative feedback is applied.
Ed
^^^ Yes it is very close.
Here is a measurement at 112 Vp-p square wave at 1 kHz into an 8Ω non inductive test load, the signal generator has a measured rise time of 14.4 ns at the input terminals of the amplifier including the input lead.
I used a 200 MHz 500 MSa/s function generator and a 300 MHz 2GSa/s Oscilloscope.
The slew rate is calculated based on the rise time reported by the oscilloscope at 10% to 90% of the amplitude: 112.0 V - 20% is 89.6 / 1.195 µs = 75 V/µs
Here is the small signal 10 kHz square wave for fun:
Also I would like to say thanks to Fireanimal for all the efforts he has put into getting a THD measurement recently, this amplifier has very low distortion so it is not an easy task to measure.
- Daniel