Hi all, time again for a small update.
Let's start with my ever hunting me subject : the gain ...
By pure coincidence, also yesterday I was able AT LAST to apply a gain "mechanism" with THD+N specs better than the DAC chips itself, or in other words, which does not degrade sound. Maybe, just maybe I have to come back on this later (because I don't like the sound of it afterall), but chances are very small because of the enormous improvement ot brought
I never told it publically, but I already told a few people off line that I again threw it out. This time it lasted two weeks though.
You could say that I thought it was "commercially" too dangerous. For many albums just great, but for most albums unlistenable again. At least through my system, and horn speakers which resonate at certain frequencies when those frequencies are too loud compared to others (and compared to as should). So, maybe, maybe I would be able to keep on listening to that myself, but then I thought and recognized that frequencies were just jumping out and it had to be wrong. Again.
Because it was much closer to what I think is good already, plus I could recognize frequencies jumping out, I now had some stick to hold on to, and search for the cause of this anomaly. And, with a special type of measurement I could find something not optimal in the circuitry. Something normally not important, but with the stupid PCM1704 as important as can be, once you learned how these chips behave, and react to an incorrect load.
So, with the help of measurement I could tune this optimally, and two weeks back again the module was stuffed in. No, I never give up.
This time I was sure this was commercially allowed, and this time it sounded BETTER compared to without the gain (a gain I don't need myself).
The only "difficulties" left were the more massive productions with a lot of cymbal hitting. So, if we'd take Led Zeppelin or the old Deep Purple as the example of this, I would say this wasn't quite right, but my wife keeps on telling me "this kind of music can have that" ... which almost sounds as "should have that" ...
Since anyway me hardly listens to this stuff anymore (but for testing), I thought it would be okay. So, at last I had found the combination of a sufficient amount of gain, together with outrageous detail, and highs as never before, while those highs we sufficiently acceptable throughout all music.
Now, maybe you can a "flaw" admosphere in the above. If you do, this is fine, because this is how I feel at writing it. Thus, it should be huray all over, but it is not. It is "just good", and nothing to write home about.
Oh ? so wasn't this what I have been working on for over 18 months now, and didn't I just tell that I at las achieved it ?
Yes, but I guess this atmosphere is created automatically when in the mean time something else has happened ...
Oh boy.
Allright. Let's first put things in the proper perspective again, or otherwise everybody may be lost on this. Especially those who auditioned my system in the past, and at whichever stage that was, it was already good, always ready for further improvement, or the best ever possible. The last stage "the best ever possible" is already from 6 months or so back, and this was before improvements which created crazy more detail in mainly the mid area.
Maybe a small example of this for those owning the album and because it is easy to check, if you listen to the first Dire Straits album, and the track Six Blade Knife, after 20-30 seconds there is this Trrrrr percussion instrument coming from the right speaker. That is, it must have been 6 months or so back that I first heard it, faintly. Now, with a few steps of improvement throughout these 6 months, now this instrument can not be missed ever anymore, and it almost sounds as loud as the other sounds from that track. I myself just can't believe that at first it wasn't there at all, while now it's nearly blastingly there. Btw, XXHighEnd contributes to this too.
If you try to imagine the above, or better, if you check it yourself for its audibility, you will perceive it to be there to some degree. Now, especially if you have difficulties in recognizing it, now hear me say that music, generally, is completely full of these kind of sounds. If these sounds are not there, okay, you might be having music allright, but if these sounds suddenly *are* there, well, you won't be able to recognize the album you even played yesterday. Nothing new by itself, but in this case so drastic, well, what to say.
The above was the stage from before last weekend, and where the gaining stage at last brought much much more than without it, so I was in heaven for that. Not only for the good sound for myself, but because I now knew this could go to you without any danger. Your jaws would drop from all what is there in your stupid redbook CDs. Together with it you'd have a very (very) fresh sound which would not fatigue, as long as you stayed out of Deep Purple ...
You'd be having something of which I would think "Well, this is it, at last I have done it. I can't get it better".
As said, before last weekend.
Then, on Saturday one of the more or less (haha) crucial parts arrived at last : the lastest PCBs for the DAC itself. The one which does 768KHz for input.
Sunday afternoon I soldered it together with the (new) special caps I had in mind for it, and after that no sound came from it. Yeah, that happens when you overlook for more than an hour that the cabling was still setup for Saturday's movie, in the end coming down to "forgot to put in the plug".
Then, by the time it was almost too late to listen and dinner almost was ready, it became clear within 0.2 seconds that something had drastically changed. Djeezz, how the most normal this sounded ! Yes, NORMAL. But what the heck is "normal" anyway ?
Yesterday evening, and time for listening again;
Those caps, needing a break-in of 3 days to my experience, just had one night behind them because yesterday all being powered off because of other (DAC) works. So, I started off with an album I run weekly (or anyway when something new is to test), Cornershop - When I was born for the 7th time. Not much familar to you I guess, but rather good quality, much varying, and enough strange sounds to appreciate it as Indian (hey Mani !).
I must have played this album some 50 times by now.
Well, to be brief : I did not recognize anything of it anymore. I tried to focus on before heard stuff, but I couldn't. Ok, melodies maybe, but further ? no, all the attention went to the new stuff now there. Hmm ...
After this I thought not to loose time to right away put Deep Purple to the test. Here we go again : Made in Japan (normal version). I can't count how many times I played this one ... can be 500.
Now imagine ... this is just "stupid" hardrock, and really nothing to get tears in your eyes from. Especially not if you heard it a 500 times before. And no, not even when I played it for the first time by means of CD, while the LP was played gray at the time. It is just those most familar tracks and tunes.
This one too I must be playing each week for some tracks, mainly to let squeeze out those cymbals, being fairly gray to begin with (well, as usual).
I was alone in the room, and at the swelling of Highway Star I immediately knew it ...
When I get tears in my eyes, it is always doubtful whether this is because of the music, or whether it is from a
yahoo, I have done it !, but since the "I have done it" was already behind me (with genuine satisfaction), this must have been about the music. Music ? well, some say. Haha.
I was shivering from top to toe, and couldn't think otherwise than that I just was there. No, no new sounds in this music, but just COMPLETELY live.
Imagining the live concert I really tried to see where improvement could be, but I couldn't. Including the cymbals and all ... man ... this is just IT.
I tried to analyse what actually happened that this all works, but I don't have real answers. One of it could be that just nothing disturbs. Another could be the sensation of being in open air because the sounds themselves were so much full of air. Also don't underestimate the rough deep low synth sounds coming from John Lord's "organ", and btw the lowest bass on Smoke On the Water (jumping in after a minute or so) is just that organ (and not a bass guitar). It must all be related to something like "nothing being wrong". Actually a mathematical thing. At least I couldn't hear anything being wrong, and this is the very first time in my life ...
We tend to relate good sound to the volume we can use. I too think this is related, but maybe now I found some reasoning to really justify it. Look :
The DAC now outputs 1.5VRMS (this is around 2V peak-peak, see later). The before best sounding version had an output of 324mVRMS. Notice that times 2 (6dB) this is 648 and again times 2 (another 6dB) this is 1300;
With the before 324VRMS I played this Made in Japan album at -12dB(FS) or so. In fact the maximum level without expecting complaints from the family (and which level is already shouting in eachother's ear when something must be said). Yesterday I played the album at -10.5dB, which means some 14dB louder as usual. 14dB is a LOT ...
We tend to think that we can play louder because things don't shout or get harsh etc. This sure is true. "Shout" will happen with frequencies put out unevenly (for level), and hars will happen when things are wrong (or not the best) all over. But as to how I think now, there is another reason ...
To emphasize how crazy it all is, and indirectly how sound has improved, let me also tell you that my level of playing always has been around -10dBFS. This was also the case when the DAC didn't output more than 164mVRMS (so that's another 6dB less). Now, always when I recognize I output higher than before without "pain" I measure the SPL. Important to know is that in my case the output level I use is never squeezed because of harsh sound (or shouting etc.) otherwise, because in such a case things are not good to begin with;
Whenever I measure the SPL, it is always around 90dB. So, the "technical" output is more, but the net output is not ?
Yesterday I broke another record for technical output level. I also could sense it because of the energy around me. The airyness which itself seemed to create sound pressure ...
I measured the SPL, and no way it would reach 90dB this time. It was way way lower, and merely 70dB.
Huh ?
The only thing I can think of is the official math laying in squares versus sines. So, if I output, say, 1Vp-p in squares, this will be 1 VRMS as well. Notice that "VRMS" is the average output voltage, and p-p (peak-peak) is the output voltage you would measure with a multi meter. Now, a square will always be at the peaks (horizontal line), whereas the sine only reaches the peak for one moment in the wave cycle and then drops back. The relation between a sine and its average voltage output is 1.414. In other words, 1Vp-p output = 1/1.414 = 0.7V.
So my gut feeling tells me that something like "before all was far too squary, and now it's nice sines" is going on. But it sure is audible, whatever it is.
Are we on schedule ? In theory yes, but the parts with 8 weeks lead time still have to arrive (5 weeks being past now), and it is hard to tell whether they will be there in three weeks or not. So, actually nothing much changed to the plan, but for two things maybe :
- The gain stage will definitely be in there, and has to be produced (PCB stuff);
- I have found a nice display, but it needs programming, and so far I have only 10 out of a total stock of 100 and I can't get more from that stock. So, that too needs production.
Peter
