Next generation Ozone analog stage - 'free radical'
Posted 25th January 2014 at 02:28 AM by abraxalito
Updated 6th February 2014 at 04:49 AM by abraxalito
Updated 6th February 2014 at 04:49 AM by abraxalito
Last night I finished building the second channel of my dual mono approach to DAC building which I've called 'free radical'. Here's a picture of the second channel's build just prior to adding all the crapacitors (cheap shanzai 'Sanyos' which measure extremely well). While building the second channel I was listening to the first in mono and that was a spur to quick completion 
From left to right there's the AD605 with its top hat array of MLCCs - outputs are isolated via ferrite bead chokes from the AD8017 under its own pile of SMT ceramics. In between the two active stages are the capacitors associated with power supply reference voltage filtering. I realized from the previous build that as the AD605's gain is controlled by DC voltages, these voltages need to be low noise to ensure gain stability. Hence lots of RC filtering with those Nichicon and Rubycon low ESR lytics. I'm using BC817 transistors as low drop-out regulators and the reference voltages (2.5 and 5.7V) come from a couple of TL431s in series.
The large empty areas either side of the active circuits I've now filled with 32 3,300uF Shanyos. The ADI chips now have around 50,000uF each across their 5V rails. The sonic result is spectacular in one respect - 'thereness'. This is very hard to put into words but there's much more believability to the whole presentation, which I put down to the lowering of LF noise on the supplies.
<Update> I have a 'munged' edition of this now, minus the headphone drive and volume control capabilities. Its using a pair of AD8129s. I have tried increasing the total supply capacitance and currently have 100,000uF per chip...
From left to right there's the AD605 with its top hat array of MLCCs - outputs are isolated via ferrite bead chokes from the AD8017 under its own pile of SMT ceramics. In between the two active stages are the capacitors associated with power supply reference voltage filtering. I realized from the previous build that as the AD605's gain is controlled by DC voltages, these voltages need to be low noise to ensure gain stability. Hence lots of RC filtering with those Nichicon and Rubycon low ESR lytics. I'm using BC817 transistors as low drop-out regulators and the reference voltages (2.5 and 5.7V) come from a couple of TL431s in series.
The large empty areas either side of the active circuits I've now filled with 32 3,300uF Shanyos. The ADI chips now have around 50,000uF each across their 5V rails. The sonic result is spectacular in one respect - 'thereness'. This is very hard to put into words but there's much more believability to the whole presentation, which I put down to the lowering of LF noise on the supplies.
<Update> I have a 'munged' edition of this now, minus the headphone drive and volume control capabilities. Its using a pair of AD8129s. I have tried increasing the total supply capacitance and currently have 100,000uF per chip...
Total Comments 7
Comments
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Nice, Richard. Stability, stability, stability - is the key - create as benign an environment as you possibly can for the active components - and you reap the rewards.
The 'thereness' just gets better and better, it makes one amazed at times about how much was captured by the recording process, even in the 'poorest' efforts ... enjoy!
FrankPosted 25th January 2014 at 05:33 AM by fas42
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What's amazing to me is that even through my fairly unreedemed (as far as PSUs go) amplifier, improvements of this kind are readily audible. The amp is long overdue for upgrades to its PSUs as it was about a year ago when I threw out its LM317/337 pair and installed TL431 shunts. More caps are called for on the opamp's supply along with some noise filtering.Posted 25th January 2014 at 02:34 PM by abraxalito
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Par for the course ... the better the system gets, the easier it is to hear the impact of a change, negative or positive - and it doesn't require 'outstanding' components to make it happen. There is where John Curl is wrong, [I]any [/I]system to a sufficient level of refinement is adequate to hear the effect of alterations.
This is the core of my fiddling with very low level stuff, the most 'mediocre' electricals can be shown to have enough integrity to allow the 'light to shine through' ...
The scary thing is, :D, I have never had absolutely everything in top notch condition, there is always a part that's a bit dodgy - yet still get superb sound at times from that. So, if the whole kit and kaboodle was firing on every cylinder ... what would the sound be like then ...? ;)
The 'invisible' speaker thing, do you get any of that?Posted 25th January 2014 at 10:04 PM by fas42
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Yeah I've been at the invisible speaker stage for quite some time now. I think that came once I got rid of the sibilance (what some others call 'detail'). One measure of how transparent the system is is how well the sound decouples from the speakers - you become totally unaware of the speakers as the sources of the soundfield. They're like the two ends of a curtain rail, and the 3D curtain which is the sound is hanging between them, seemingly without visible support from them. Since they've been becoming progressively more invisible the more I've 'refined' the sound, I (like you) wonder what the end-point is?
When I had only one channel of the 'free radical' running it was interesting to see how pure a line source was projected when the same signal was fed into both L and R. I didn't examine it carefully but I did get the impression that the amp might well be 'smearing' the signal over to one side in that one speaker sounded a bit less invisible than the other. I could test this (but haven't yet) by swapping over the speaker wires.Posted 25th January 2014 at 11:27 PM by abraxalito
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Ah-ha ... you're getting into interesting territory - the pure mono feed. The effect that "should" occur here - but it could depend on how one's ears are 'tuned', of course - is that the image moves along, as one shifts in position to the left or to the right - the musical "picture" is always in front of you.Posted 26th January 2014 at 01:09 AM by fas42
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50ku is a lot. Is this in crcrc?
Sounds like you have a winner.
I love that speaker disappearing act. some times I marvel at the notion of . What are those things doing in the room?Posted 27th January 2014 at 10:01 PM by wlowes
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No, its all paralleled up in a single lump, after one inductor. Before the inductor is an EF operating like a cap multiplier.
Having made a recording of the supply noise, seems the AD605 generates its own hash, notwithstanding the CCS on its outputs. Which is as I expected, not all the circuits in the device are in pure classA. I also made a measurement of the LF PSRR at the output, its somewhere around 55dB. Hence all those caps aren't for filtering the incoming noise, rather for protecting the chip against its own detritus.Posted 28th January 2014 at 01:35 AM by abraxalito
Updated 28th January 2014 at 01:43 AM by abraxalito
