Hi X, great comparison! Using AKG Q701 cans, multiple instances of Potplayer, and knocking down the level of the amplified clips a tad, the amp/speaker renditions and the reference clips sounded really close. Re: the FH9 and the Quasi, to my ears the FH9 sounded a bit louder whilst the Quasi did seem to offer a smidgen more detail (eg. the shaker from first track sounded closer to a shaker).
Re: recordings and the first clip, the shacker didn't sound properly defined in all clips when compared to the reference clip. I wonder how much of that was/could be attributable to the room (I could hear faint slap echo/room colouration), diffraction from wide baffle and/or limitation of the 10f's upper range, amplification, my systems?
Looking foward to your 3 way!
Re: recordings and the first clip, the shacker didn't sound properly defined in all clips when compared to the reference clip. I wonder how much of that was/could be attributable to the room (I could hear faint slap echo/room colouration), diffraction from wide baffle and/or limitation of the 10f's upper range, amplification, my systems?
Looking foward to your 3 way!
Thanks to xrk971 for taking the time to post this comparison.
All the amps listed performed very well. Having listened to all samples, I like the Quasi and the VHEX amps best. I think clip number three best illustrates the differences between those two amps:
1) Starting at 17 seconds into clip #3 - ("...there's a light at the end of the tuuu-uuu-uuu-nnell...") the quasi doesn't resolve all the detail in that passage. There's a point where she's almost breathless when singing "tunnel", and also the rhythmic up and down as she sings the rest of that passage - on the Quasi I could barely hear that. The VHEX resolved that perfectly, you hear a lot more detail in that passage.
2) At 39 seconds into the clip ("...that woman's son...") - the piano player plays two quick chords after she finishes that sentence. The Quasi reproduces this sound with much more energy, you can really feel the piano player hitting the keys, and the notes kinda hit you in the face, with real gusto. The VHEX doesn't emphasize this passage, the piano notes sound more natural, albeit less exciting.
The Quasi comes across as warm and dynamic - it's all honey, and lots of it
The VHEX is more natural and transparent, but yet dynamic and warm enough.
In conclusion, even though I really like the Quasi's sound, I would prefer the VHEX due to it's more natural presentation and higher resolution.
All the amps listed performed very well. Having listened to all samples, I like the Quasi and the VHEX amps best. I think clip number three best illustrates the differences between those two amps:
1) Starting at 17 seconds into clip #3 - ("...there's a light at the end of the tuuu-uuu-uuu-nnell...") the quasi doesn't resolve all the detail in that passage. There's a point where she's almost breathless when singing "tunnel", and also the rhythmic up and down as she sings the rest of that passage - on the Quasi I could barely hear that. The VHEX resolved that perfectly, you hear a lot more detail in that passage.
2) At 39 seconds into the clip ("...that woman's son...") - the piano player plays two quick chords after she finishes that sentence. The Quasi reproduces this sound with much more energy, you can really feel the piano player hitting the keys, and the notes kinda hit you in the face, with real gusto. The VHEX doesn't emphasize this passage, the piano notes sound more natural, albeit less exciting.
The Quasi comes across as warm and dynamic - it's all honey, and lots of it
The VHEX is more natural and transparent, but yet dynamic and warm enough.
In conclusion, even though I really like the Quasi's sound, I would prefer the VHEX due to it's more natural presentation and higher resolution.
I think this is the same phenomenon causing XRK to think that VHEX had more detail than the reference.
And that's the proof that, even in the reference clip, the resolution is very low.
You think it is "that woman's son" when it is actually "that mornin sun". The word "mornin", especially the "IN" is not clear in both VHEX and Quasi, but it is very clear in the reference and circlophone.
I don't know why the sound resolution in the reference clip is so very low, but at least the circlophone can reproduce the sound very close to the reference. So may be it really is a low quality source/recording (hopefully not the input impedance issue).
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Actually, I think I modified my statement that the VHEX recording had more detail than source once I used good headphones and good headphone amp. The source clip is still the best. I will have to listen again to see what this "Morning Sun" business is all about. I know the song so well it never occurred to me it may be unintelligible on some clips.
Haha, probably related to fact that source was 320kbit mp3 format vs FLAC lossless. Really, a compromise made to allow a 45 second long sound clip to fit as an uploadable file on DIYA servers. It works for most situations but of course, no comparison to a 192kbit/sec 24bit FLAC on a good DAC.
Unfortunately, I did not save the recorded high resolution sound clips. So I would have to re-record everything and that's too much work. I don't like the idea of having the sound clips located on a remote server - the probability for broken links in the future makes the post not very enduring through time. One of my pet peeves is going through an old thread that would otherwise be really interesting except for fact that most of the content is missing because of broken links.
AX11 Bimo Mod Sound Clips
I'm adding another amp into the sound clip library. The Apex Audio AX11 Bimo mod, with layout by Prasi. I am runnung 100mA quiescent bias current with same 35v PSU used by the other amps.
Classic differential LTP input stage and complementary Toshiba 2SA1943/2SC5200 output stage.
Photo of unit 2:
Measured harmonic distortion:
Change sound clip extension to.mp3 to listen.
I'm adding another amp into the sound clip library. The Apex Audio AX11 Bimo mod, with layout by Prasi. I am runnung 100mA quiescent bias current with same 35v PSU used by the other amps.
Classic differential LTP input stage and complementary Toshiba 2SA1943/2SC5200 output stage.
Photo of unit 2:
Measured harmonic distortion:
Change sound clip extension to.mp3 to listen.
Attachments
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Listening through my laptop's speaker, I couldn't find anything special. Probably my least favorite... Compared to FX8 which has similar input stage, no contest.
I have not listened to it myself on headphones. However, I just put the Quasi back in for a test of some new IRFP240's that arrived in the mail (yes, the Quasi is my cheap Chinese MOSFET tester ). The MOSFETs are good and furthermore - the amp immediately sounded better to my ears than previously installed AX11. Will have to listen on headphones next. But interesting comments so far.
). The MOSFETs are good and furthermore - the amp immediately sounded better to my ears than previously installed AX11. Will have to listen on headphones next. But interesting comments so far.
i did gave a listen too for the three amps, AX-11, FX-8 and the Quasi.
quasi is slightly smoother through the entire range, FX-8 bimo mod is neutral and more "hi-fi".
AX-11 bimo mod sounds similar to FX-8, but has slightly pronounced drum beats.
**I havent read through the thread, just downloaded the clips where they are and gave a listen atleast 10-12 times, initially i felt there was no difference, but repeat listening gave the above observation summary. Does this correlate with your findings ? as you are the first hand direct listener to all the amps. We are the mercy of differences in head phones, laptop DACs, recording instrument etc, etc. Also some room acoustic effects might also get added to recording, unless you you have taken care of that **
** Just opinions, no preferential treatment to any amp, as I think XRK's three amps PCB have my layout design..
quasi is slightly smoother through the entire range, FX-8 bimo mod is neutral and more "hi-fi".
AX-11 bimo mod sounds similar to FX-8, but has slightly pronounced drum beats.
**I havent read through the thread, just downloaded the clips where they are and gave a listen atleast 10-12 times, initially i felt there was no difference, but repeat listening gave the above observation summary. Does this correlate with your findings ? as you are the first hand direct listener to all the amps. We are the mercy of differences in head phones, laptop DACs, recording instrument etc, etc. Also some room acoustic effects might also get added to recording, unless you you have taken care of that **
** Just opinions, no preferential treatment to any amp, as I think XRK's three amps PCB have my layout design.
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Hi Prasi,
Thanks for your observations. The point of the test and listening by the remotely located auditioner is that the whole recording and source chain and listening chain (your DAC, amp, headphones) are identical. The only difference being the amp under test. So any perceived differences must come from the change in the amp. I agree they all sound very similar and it means that people will probably be happy with any of these amps as they are quite good, well excellent sounding really compared to much commercial stuff at usual stores under $1k. There is some unavoidable room effects which I try to minimize with mic placement at 0.5m from speaker. The sound you hear is exactly represented by the measures frequency response posted which is pretty much flat within 5dB over 50Hz to 16kHz (or wide range of our hearing).
My in-person reactions to the sound are different than what the recordings show because I do get more room effects by listening farther away at the listening position and I get benefit of stereo separation and sound stage.
I do agree FX8 Bimo is very HiFi sounding. In person though, the amp that seems to get me to take notice are the Quasi, Circlophone (BJT), and the FH9. The Quasi has a totally different sound signature - it's probably difference in H2 vs H3/H4 but dynamics seem very lifelike. FH9 has a very pleasing engaging and powerful sound. The Circlophone (BJT) seems to do everything right - overall very balanced, low distortion, great dynamics. For critical listening and lowest distortion - probably the Jason K VSSA and VHEX+ are what I would say as most accurate. If I had to pick one amp as the only amp I had to live with for a long long time...
The VHEX+ gets the nod. In the end, neutrality, great dynamics, and midrange and high range resolution keeps me listening to all genres.
But, what's the most "fun" amp to listen to that will make you, as Hugh said, "get your feet tapping", the Quasi and the FH9.
Thanks for your observations. The point of the test and listening by the remotely located auditioner is that the whole recording and source chain and listening chain (your DAC, amp, headphones) are identical. The only difference being the amp under test. So any perceived differences must come from the change in the amp. I agree they all sound very similar and it means that people will probably be happy with any of these amps as they are quite good, well excellent sounding really compared to much commercial stuff at usual stores under $1k. There is some unavoidable room effects which I try to minimize with mic placement at 0.5m from speaker. The sound you hear is exactly represented by the measures frequency response posted which is pretty much flat within 5dB over 50Hz to 16kHz (or wide range of our hearing).
My in-person reactions to the sound are different than what the recordings show because I do get more room effects by listening farther away at the listening position and I get benefit of stereo separation and sound stage.
I do agree FX8 Bimo is very HiFi sounding. In person though, the amp that seems to get me to take notice are the Quasi, Circlophone (BJT), and the FH9. The Quasi has a totally different sound signature - it's probably difference in H2 vs H3/H4 but dynamics seem very lifelike. FH9 has a very pleasing engaging and powerful sound. The Circlophone (BJT) seems to do everything right - overall very balanced, low distortion, great dynamics. For critical listening and lowest distortion - probably the Jason K VSSA and VHEX+ are what I would say as most accurate. If I had to pick one amp as the only amp I had to live with for a long long time...
The VHEX+ gets the nod. In the end, neutrality, great dynamics, and midrange and high range resolution keeps me listening to all genres.
But, what's the most "fun" amp to listen to that will make you, as Hugh said, "get your feet tapping", the Quasi and the FH9.
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OK great!
when i said differences in headphones, DACs etc, i meant from one person to next person, e.g., like me and other people giving a listen. So you will find varying opinions, depending upon individuals choice and taste and equipment they use to listen.
slightly busy these days, cant find time, otherwise I would love to build all of these amps and give a listen myself.
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