Is this amp THD good enough?

I would guess that the amp is not anywhere near the stated THD figures in reality but apparently it gives you a fuzzy feeling seeing it on the screen so thats good! Nice speakers you have!

Rock on!

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It is a 1N4007 not an old red LED, an LED has a completely different symbol. Was just the right volt drop to bias outputs at about 6 watt each. Now running 24W class A.

Actually class A is related to the output current, not to the power dissipation as such, if the OS idle current
is 0.3A it will be class A up to 0.6A peak output current, so about 1.5W RMS and 4.8V pk output voltage,
with a +-12V voltage supply and same idle current it will still be class A up to 1.5W RMS but with only
7.2W dissipated by the OS.

At 24W dissipation/channel the optimal idle current would be 0.866A with a +- 14V supply voltage,
this would amount to roughly 10W RMS/8R assuming 1.35V max voltage drop per rail,
wich is perfectly feasible if the driver stage is supplied with say +-18V, the OS being kept at +-14V.
 
I wouldn't underestimate the importance of speaker matching. Planar with near zero inductance -- so the theory on ultra-high gain and feedback should hold up quite well.

Connect speakers for mere mortals though, and the high damping factor will be great for subwoofers but bad for mids and tweeters, and you can probably forget about FR or high efficiency transducers. At least the kind that is directly connected and relies exclusvely on active crossovers. Trouble is, stored energy in the driver is readily turned into voltage, but this amplifier robustly clamps it and turns it into current. And converting from voltage to current to vibration and back to voltage again is prone to distortion at every step. So, you can imagine at high frequencies, any ordinary speaker with break-up modes will get shredded (and of course the best 2-way is a 3-way).

This is probably much less of a problem with passive crossovers, as half their job is to add impedance at the top end of each driver's range, not just controlling frequency response. But active / DSP filters can't do that, so the amplifier has to do it for them.

If you want to brute-force the matter, you can always pay 2x or more for drivers that are loaded down with copper Faraday rings, almost making it a moot point. A particularly bad combination could be actively filtered Fostex drivers with krinkly 3g cones. I can't really fault the amplifier when planar speakers were mentioned at the outset, but they almost have to be planar to get maximum benefit.
 
HAYK, I listened to the files. I wish I could be more encouraging but I do not like classical music at all and I don't like Frank so I am too biased. To me both files are smooth and quite dynamic, but a bit flat or characterless. I am a Rock/Early Metal fan so asking me is taking a chance. I am not an audiophile either - Sorry my friend. I like listening to my genres of music and not at equipment. As Mooly quotes my equipment is for music.
 
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Hi Abstract, unfortunately I got what I have all speakers I had for many years, KEF Concerto, Rogers LS3/5 and Appogee. The Rogers I use on my Desktop with JHL 1969, they are both from the 60s/70s era and good match. The Appogees are currently on ELD, but will wait later today so my gardener can move my Concertos into the room. In fact I prefer the warmness of the Concerto also bought in early 70s. I had a set of Cadenza but when I moved here one a month ago my wife asked me to sell some equipment due to space constraint. Besides I agreed with her. The Concertos were connected to 3 x KRELL KSA50 clones with active cross over (which I still have) I also have a pair of Linn SARAs but have never used them in maybe 30 years still in their original boxes. Of all those speakers recently played I like the Appogees the least of all but, when we moved in here on the first of this month, that is what I decided to set up for the time. Of all the speakers, the LS3/5 have been my favourite and least fatiguing and they play music and whatever I do on the PC.
 
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Yes, I listen to a lot of singer songwriters and the voices are the most realistic repro I have ever heard (and I also have Quad 57 and 63 at my listening room!), but what also hit me is the stability and width of the soundstage.
I have tried other setups; but this one is my favorite one.
Nice to know you also appreciate them for a nearfield repro.
👍 😉
 
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HAYK, I listened to the files. I wish I could be more encouraging but I do not like classical music at all and I don't like Frank so I am too biased. To me both files are smooth and quite dynamic, but a bit flat or characterless. I am a Rock/Early Metal fan so asking me is taking a chance. I am not an audiophile either - Sorry my friend. I like listening to my genres of music and not at equipment. As Mooly quotes my equipment is for music.
Thank you very much for the report.
99.9% of class AB amplifiers go dirty with these music. In fact there are hundreds in between as Frank is the simplest.
I will report your comment on Wolverine built thread, where the Mazart was dirty because MP3 and My Way recorded by bad microphone. Just for humiliation of 20 years technology difference.
This phenomenon has nothing to do with the circuit, it is due to rectified currents of the supply are reinjected into the signal. The culprit is the PCB design and supply wires.
If your Amp runs in AB, it will be most probably as dirty.
Here are some others that I pass first on a new testing amp.
Happy together by Turtles ( A customer noticed in 1973)
Sing, sing, sing B Goodmans.
 
I don't know if you have the song McArthur's Park by Richard Harris also incredible. I am not sure if anything I listen too can be classed audiophile because I don't really know what audiophile means to be honest. I don't think it is any real qualification. Are you an audiophile if you can hear if something is wrong with your cars motor?
 
What I mean too is that the music is already distorted before it even enters my amplifier, and that is okay - no complaints. I tend to think that listening to your turntable directly is probably the best sound you can achieve, a stylus in a grove vibrating in the air, nothing in between that can create any distortion. 🤔
 
a stylus in a grove vibrating in the air, nothing in between that can create any distortion

That ultimate devices are available. Though, you’ll have to commission cutting new discs with your favorite modern music. 😀

pphonet.jpg
 
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Lets say a modern recording is available for that thing. What would it sound like?
My wife has a cat, when she comes anywhere within earshot the cat would run to meet her. When she calls me on speaker phone, the cat would not even flinch. However, I learned to recognise my wife's voice, why does the cat not do so. Too much distortion?
 
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I will teach her cat fast Fourier transforms maybe the cat will respond then. I would have to teach the cat to read and write first I guess. Maybe there is no bass on that thing because the horn is not seven or so meters long. Some very expensive loudspeaker horns are, but are equally ugly.