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Audiotrak Prodigy HD2 opamp configurations list
Oct 23, 2011 at 7:28 AM Post #436 of 492

earfanatic said:
I tried some lme49990 as buffer and I liked it better than the LT1028. Very little change though.
Click to expand...


that's because you didn't try the AC grade of LT1028 IIRC
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Nov 1, 2011 at 4:39 PM Post #438 of 492
Have the 2x2x AD797BR (I/V)and 2x LT1028ACN (buffer) in the advanced HD2 version + the 4 470 ohm (not 460) resistors mod.
like the sound of it :clear and direct.
But this opamp 1028+resistors causes a loud PC power on and off 'plok' sound..:frowning2:
Must be the sensitive nature of these opamp (1028 ) DC out power up/off?
No hard plok with another opamp as buffer like lme49990? > eBay ordering...
 
Update nov 9 : received The DUAL SOIC LME49990 DIP8 ADAPTER for the buffer> the 1028ACN  and resistors out.
No loud PC Power on/off plok anymore just the soft driver clicks when windows boots.
Sound ; clear, bright and detailed mids/high.
 
Like the sound better than the 3x Burson version which I was selling: a bit to dark for me , just a matter of taste
 
update nov27: back to LT1028ACN, no resistors mod . seems to work, opamps running cool, so far I can check with the fingers..
like the LT1028ACN better than the LME49990; not so bright, more bass .
The LME 49990 did I put in my Little Dot 1+  Head amp(+DT990) a better place for this bright but nice detailed opamp.
(update :I did also a LT1028 (CS8)in my Little dot >also here deeper bass more 'organic' mids&high compared to the LME49990.

 
Now is the sound balanced: deep bass, detailed, clear mid and high,  not overbright.
So for me(and Leeperry) the  AD797BR and LT1028ACN combo is still unbeatable
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I will now try to solve the  power on/off plops with decoupling caps, output resitors and coils.
 
update dec.4:specsheet:
 

 

I did use a 47 pF over-compensation cap.power on/off plops seems less, less overshoot?.. tweaking on
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Dec 28, 2011 at 11:06 AM Post #439 of 492
Dear lovers of great sounding music!
 
I was always a freak of highest quality sound, but did come to the truth after many years by purchasing HD2 Advance DE soundcard (at least I hope so:))
 
 
To be most specific and less bothering for community just a few  questions:
 
1. Which is best for W7X64: WDM or ASIO? I need the card exclusivelty for music.
2. Based on this thread summary (excluded any experiments resulting in possible pops and clicks) going to settle at  LT1364x2+LT1361 or Lt1364x2+LM4562NA. Do we have any winners?
 
Thank you for support
 
 
 
 
 
 
Jan 7, 2012 at 8:06 PM Post #441 of 492
Some other site that had the old guy judging sound by his ear rather than specs which is more my style, had some 'old cans' on the output. I found them, you guessed it, Ebay from China ($27 FS)  OPA 111BM already mounted on an adapter.
 

I am still running the adapted AD797BR but replaced the adapted OPA627AU output with these adapted cans, no other mods.
 
The cans seem to not filter out certain frequencies where the more sophisticated OP-AMPs do. Instead of a type of muddled bass, I hear low/deep musical tones off the, drums and bass guitar. Clarity is as good or better. Staging is slightly different but certainly not missing.  I'd say it favors the mid to lower ranges, only slightly missing the highs. Voice range is excellent. Seems to reproduce older recorded music well or at least makes it sound better, probably because these cans were used back then as the best available.
 
Have some Sennheiser HD 280 Pro phones, never use them. Still in 2.1 mode using a Klipsch Ultra 5.1 sub with circa 2002 Klipsch bookshelf reference RB35RB75 speakers (6.5" mid, 1" tweet sits in a 5" horn, 52hz-20khz 94db 100watt, rear ported). These speakers actually drown out the sub for a prefect blend between the three.
 
Update: Went back with AD797BR on 2 adapter boards (I/V) and BB OPA AU697 on one adapter board (Buffer) No other mods. If I don't like the immediate sound, I can always manipulate the VIA Audio Deck to my liking. These OP-AMPs seem to cover a large range and stage well, so I have have plenty of range to work with and the OP-AMPs are very responsive to software adjustments. [The Envy Vinyl chip never fails me.] Bought Audio Technica ATH-M40 headphones for cheap, the box says flat and they are but have a nice range, voices are very clean, bass is there but doesn't jump out at you hence the reason they are flat sounding (like needed for mixing).
 
Jul 2, 2012 at 3:38 AM Post #445 of 492
Hi,
Very interesting thread. I tried the suggested combo 1x2x LT1028 + 2x2x AD797 and found it good sounding, better than the quite nice sounding combo 1xAD8066+2xLT1358 prior on my HD2 card. Only it is somewhat veiled in upper midrange and treble and not as transparent as a new combo I recently tried. That is, 1x2x AD797+2xLT1124 that IMHO is a still better sounding combo, at least as compared to the CS version of the LT1028. I haven't tried the AC-version though so if it beats that one too I can't tell.
 
 
Aug 19, 2012 at 3:56 AM Post #447 of 492
This thread appears dead but for guidance I think I might anyway convey my experience and changed opinion on best opamp combo for the Prodigy HD2. After having built a high-end cics Memory Player computer with SSD, passive cooling and pi-filters on all voltages I have come to the conclusion that the combo 1x2xAD797 as buffer amp and 2xTHS4032 as filter amps is probably as good as it gets, or at least very, very close to it (theTHS4032 is a pain as buffer amp, sharp in sound and obviously not stable but perfect and superbly sounding as filter amp). On all adapters I have soldered small film caps between the  + and - rails and on the AD797 chips I have soldered 27pF disk caps between pin 6 and 8 (distortion reduction). This is high end opamps and with high end computer gear, this is high end sound to the point of getting surprised! The timing is perfect. There is an amazing coherence, Atmosphere in recordings comes through very convincingly. The treble was first a bit shy, but after inverting absolute phase 180 degree (a convenient button in cicsPlayer) it comes through just right. I can only say that this combination will stay and is highly recommended..
 
 
Sep 11, 2012 at 1:29 PM Post #448 of 492
After some more listening I turned back to the LT1028CN8 as buffer stage. It has more body in instruments and they are more natural sounding. The AD797 is also very detailed and good sounding at first but it became obvious to me at comparing with the LT1028 that it has a slight artificial edge. That edge is also there in the filter positions. It became clear to me at comparing with the THS4032 that I find unsurpassed natural sounding here (but beware of putting it in the buffer position). The AD797 is said to be tricky but sounding very neutral and good if implemented correctly. It thus seems like the Prodigy HD2 might not provide the optimal implementation for this opamp. So the final suggestion from me is 1x2xLT1028CN8 + 2xTHS4032 for the Prodigy HD2 for unsurpassed SQ so far. The DIP8 version LT1028ACN8 sound very different from the CN8 and not as good at all (hard and with edge). It badly needs the resistor modification described in this thread to hopefully sound good as well (I havn't tried it though).
 
 
Sep 13, 2012 at 3:59 PM Post #449 of 492


And one more thing. Forget about film caps between the rails (I know...I changed my opinion again). Solder electrolytic caps instead between the +V and -V rails on the opamp adapters. I use Elna Silmic II 100uF/25V. They do a great job cleaning up the sound in my system. Bass becomes more firm and midrange and treble more detailed. Be sure to solder the caps with as short leads as possible on the adapters (to avoid creating high frequency antennas). SQ is also much improves by implementing LC- or pi-filters (C parallel - L series - C parallel) between the PSU and the P24 and P4 connectors respectively in the computer, both between each voltage and ground and between +12V and -12V. I use 4 pi-filters,1500uF-3.3mH-3300uF, between P24 +12V, -12V, +5V, +3V respectively and ground, another one between P4.+12V and ground and two 1500uF caps between P24 +12V and -12V, one before and one after the 3.3 mH inductors. Just be careful with the choice of inductor so it can take the current and the voltage drop won't become to large. .
 
Sep 16, 2012 at 5:48 AM Post #450 of 492
 
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