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post the replies of Buson Audio
I am in contact with Dennis from Burson Audio. He asked me to try several things such as using only one V5i instead of two, and measuring the voltage across pins 4 and 8. I measured the voltage to be 23.9V which was in the normal range. Also, keeping only one V5i and replacing the other with the old NE5532 significantly reduced the noise, although didn't completely removed it.
However here is the really bizarre part. With the two Bursons in place, I was hearing a lot of static in my headphones. Also when I moved around the headphone cable, the static changed in intensity. The static turned out to be radio signal, because today I was able to hear FM transmission through my headphones! I even heard a commentator say 101, so I know the station captured is near 101 MHz. My wife heard it as well. Clearly, with the Bursons in place, the headphone cable is acting as a receiver antenna and all that static was radio interference. How that signal is getting amplified to be audible through the headphones is beyond me. I don't have enough electronics knowledge to figure that out. I am writing to Burson Audio about this.
Like several other opamps, V5i may not be compatible with all amps out there. Like I said before, my Matrix HPA-3B didn't quite liked the V5i much and I was reading here on Head-Fi that other head-fiers had issues with other amps model (feel free to search for yourself).
You might be able to solve it if you're willing to adjust the gain of your amp.
I agree with you, but the thing is, several others have successfully used the V5i in the amp model that I am using and none of them faced any noise issue (I got the V5is based on their recommendation). https://www.head-fi.org/threads/nobsound-ns-08e-also-know-as-nobsound-6j9-hybrid-tube-amp.794796/
It doesn't seem like, my particular amp has any electrical defect either, since the old opamps work just fine. I am considering burning them in for several days to see if subtle changes in their electrical characteristics can improve the noise issue. I am curious about the V6 and may consider getting a Matrix amp in the future to try them (I hope the V6 fit inside them with the cover closed). The Sennheiser 6XX sound really sweet with these opamps.
How do you adjust the gain of the amp (there is no gain switch)?
Seems like interference in both power chord and headphone cable. Will try adding a couple of ferrite cores to see if that solves the issue.
you are right use some ferrite cores and post the update
Using ferrite cores on both the power chord and the headphone cable (Sennheiser factory one) eliminated the noises almostly entirely. Now, there is a very low level noise that is only detectable in absolute silence. I had to use two ferrite cores each on the cables. However, the ferrite cores didn't help at all with my Sennheiser cable from ZY cable. This cable picked up loud FM interference and was unchanged with ferrites. Anyhow, I am now a lot more satisfied with the amp and probably will keep the opamps.
Back when I was testing the V5i I had similar issues too, but to know that they might be radio signals is quite interesting.
Are the LME49720 dual op-amps in the Gustard H20 amp can be swapped to discrete op-amps like the SS3602 or the Burson V6?
Tried all the opamps quickly today on my XD-05
Tube sounding opamp. Not quite replaceable with tubes but pretty close. The typical reverb (or harmonics) is present, treble is really sweet. This one is the most pleasurable to listen. But not accurate and precise, certainly not that detailed. Bass depth is average, or maybe below average. Treble extension is unnoticeable if it is present even. Mids are forward, really nice and smooth.
Smooth, details not satisfactory. Neutral, very thick sounding. Bass depth is noticeably nice, treble extension is better than the OPA1602. It's actually a toss between this and opa1602, for different moods. They are both quite different.
This is the one that gets closest to LME49720. It's very confusing to compare these two. One thing is clear though, lme49720 is more precise and accurate in terms of imaging and placement. Also, lme49720 seems to have better and more extended highs. But I need more time to get conclusive on this opamp. It looks promising. It has the same level of clarity as lme49720. For now, I have replaced lme49720 with opa1642 to get more detailed impressions.
As of now, LME49720 & OPA1642 are the 2 best in my XD-05.
I've never found a setup where at times you don't catch the OPA1602 struggling with articulation - its minor but just enough to be displeasing - a shame as otherwise an excellent imitation of a tube a like sound.
Out of that OPA16xx line I prefer the OPA1612 while a little synthetic sounding especially at first and a very touch light on the bass it is detailed and clear and I've never heard any problems with articulation, etc. those preferring a warmer sound and/or a bit more rich "musicality" might not like it though. I actually prefer it to the LME49720 as while it doesn't quite have the clarity due to being a touch smoother it doesn't have that slight metallicness for want of a better way to put it as the LME.
Personally I end up going back time and time again to the AD8066 with the right capacitors around it it just has everything I want.
Sounds like you didn't try 1622
My XD-05 is dc coupled with BUF634, so it sounds different from capacitor coupled circuits.
In my XD-05, LME49720 and OPA1642 sound better than OPA1612. 1612 to me has boosted sub bass, makes instruments sound a bit more hefty
My stock XD-05 was all great with 1613 until I swapped it out for LME49720, it's just more linear, natural and has edge at details and clarity, at least in a perceivable way. 1612 had a very laid back boosted sub bass which hampered with detail perception and soundstage a lot.
In fact in the OPA16xx series OPA1642 is better in my setup.
Folks at MD were gaga over V5i in XD-05.
I've not seen the 1622 in a DIY friend format yet - though I've heard interesting things about it. Local place only has it in VSON which I'm not setup to solder though I suspect I could probably manage to jury rig it
Ah the BUF changes things a bit - surprised about the 1612 though in all my implementations it has if anything been a touch lacking on the sub-bass front but only slightly.