[khaine1711]

That statement from Adrian is a bit inaccurate. The transformer hum always stays at a constant level, and does not get louder when you turn up volume. This is true for most transformer coupled amp. The only thing that increase the hum on the Icon is the impedance tap.
 
On the L setting, once you turn up the music, you cannot hear the hum. You can still faintly hear it when no music is playing, or the music suddenly goes quiet (think Shostakovich's Leningrad -  Allegretto). But I will agree on the point that it's not audible at normal listening level, and with the majority of the recordings.
 
That is on the L position though. With the H position, you can hear the hum with say ... a video of someone talking about something on youtube. But then I doubt anyone would specifically need a 600 ohm output Z 

.
 
Did you opt for both the cap upgrade and valve, or just the caps?

 

[tigerkg13]

Sorry, I don't know much about tube amps. but I do believe the upgrade in question refers to the capacitors. Whether the valve is included or not I can't be sure. In one sentence he talks about the capacitors and then refers to it in more detail as follows:
 
 
'The benefit of  having the Jensen copper foil upgrade is that you will get a more “silky smooth” sound reproduction. The cost of this upgrade is and additional 85.00 pounds.'
 
 
I also upgraded the tubes he recommended. The costs of this upgrade is separate. BTW, my unit is the HP8 Mk2 (matte) not the HP8/MP3 version.

 

[Xcalibur255]

Unfortunately for your wallet the amp needs both a driver tube upgrade and a coupling cap upgrade to sound good.  It doesn't have to be Jensens, there are lots of good caps out there that can improve upon the stock choice.  I feel fairly confident that the remaining midrange coloration I'm hearing will go away once I get my new caps in.  Power tubes will improve your sound too, but the driver upgrade over the basic stock Shuguang is essential. 
 
Not to contradict khaine but rather just to offer my own experience for additional perspective, my own HP8 is silent during operation on all impedance settings.  I haven't gotten a hint of tranny hum and I have yet to pick up any microphonics from tubes either.  I was pleased to discover this evening that my BGRP Tung Sol 6SN7s which are noisy in driver applications work perfectly and noise free in this amp which is just what I was hoping for.
 
I have some sensitive headphones I can use to further investigate the amp's noise floor, I'll check into this.  I think what it may come down to is build variation, how close certain B+ wiring comes to the power supply and how carefully any shielding is laid out can have a major effect on hum levels.  This can vary from unit to unit because they are mostly hand wired.  I recall from the Woo owner thread somebody who was constantly haunted by hum from his WA22 which is an amp that is usually quiet.  The issue only went away for him when he sent it back to Woo and they basically re-wired it again to prevent the interference that was getting into the B+ (the electricity that carries the actual audio signal) in the first place.

 

[khaine1711]

The noise floor is pretty low. At least in my case it's lower than the hum - which is quite good.
 
Also nothing contradicting really, could be my unit, or it could be that their 120v trannies are more quiet than the 230V. But to get no hum on high setting, that's amazing. Still, I plan to send it back to Icon to check before I did my own capacitor upgrade. If it still hums I'll just accept that I'm way too anal sensitive about transformer hum in general.
 
On the tube rolling thingy, I'm also using BGRP 6SN7, but with the Mullard Mc1 in front. Trying to track down some gold brand Sylvania 5751 from the EU with no luck.

 

[Xcalibur255]

There is some consensus that the triple mica black plate 5751 Syl and the Gold Brand are pretty much the same tube sonically.  I just went with what I could find for a reasonable price, the GB tubes get bid sky high.
 
I'm suspicious there may be something going on with your amp.  I'll try out a few other headphones if it helps, but I've run the LCD-2 and the DT880 on every gain setting and never heard any transformer hum on any of them.  I've found the DT880 sounds best on the High setting now that I have the sibilance tamed, and the LCD-2 of course sounds best on Low. 
 
I'd been meaning to try the other headphones out anyway since it helps give a better picture of the amp's flexibility. 
 
The BGRP Tung Sols pair really nicely with the Genalex.  I had some Sylvania bad boys in the output position but this was a little too laid back sounding for the LCD-2s, the Tung Sols are still smooth but sounds better balanced overall.  With this setup I feel the caps in the amp are what is holding things back.  The amp doesn't feel very transparent on some material and I don't believe the tubes are contributing to this.
 
Just a random thought here, but I really wonder why David didn't just design this amp to run 3 6SN7 tubes?  This amp has way more gain than it needs with the 12AX7, and the distortion and linearity are inferior to the 6SN7 anyway.  I think a lot of designers just automatically use the 12a series mini tubes simply because that's "what you use" in the first stage, them being the most popular tubes in use when tubes originally rode off into the sunset.  I think the amp would be better all around if it were driven entirely by 6SN7s.  Maybe in the MkIII?

 

[khaine1711]

I think all black plate Sylvania 5751 are the same. The one different is grey plate gold pin. 
 
On the 3x 6SN7  I think it has more to do with availability and expectation. People generally expect valve amp to have those tiny preamp tubes, followed by several big power tubes - then add in some shiny rectifier/glowing phase splitter if possible. An amp running only one type of valve may throw some people off =p. Reminds me of the Super 7, my thoughts process is like what on earth should I do with various sets of seven 6SN7s in case I upgraded.
 
Also good 6SN7 are rare in the UK, while ecc83 are numerous.
 
Do you get no audible hum on the lcd2 with all impedance setting (especially High) - even in a dead quiet room with no music playing?

 

[Xcalibur255]

I'll have to check again when the air conditioner isn't running, but I don't recall hearing any.

 

[khaine1711]

Quote:

I'll have to check again when the air conditioner isn't running, but I don't recall hearing any.

Appreciate you taking the time to check it out.
 
One small request for owners, a bit silly though - could any of you try .... lifting the Icon up and turning it upside down to hear if there's any sound? - like a small sound of a nut/bolt tapping/touching the enclosure. I know it's heavy (7 kg) but if you could do that it would be a big help 

 
I think I heard a sound similar to a screw coming loose inside the main transformer (the big black box on top) when I turn it upside down for cleaning purposes. Could be the source of the hum I'm experiencing (transformer isn't tightened enough).

 

[Xcalibur255]

Since the wiring is point to point I think the most likely source could be a small bead of solder loose inside the unit.  Sometimes they get under things and are missed during inspection but shake loose during shipping.  Just a guess of course. 
 
Or another thought:  does it happen after the amp has been on a while?  If so it could be vibration coming from output transformer oscillation, which would be bad.  This shouldn't happen as long as there is a load on the circuit (aka you have headphones plugged into the jack).

 

[khaine1711]

Quote:

Since the wiring is point to point I think the most likely source could be a small bead of solder loose inside the unit.  Sometimes they get under things and are missed during inspection but shake loose during shipping.  Just a guess of course. 
 
Or another thought:  does it happen after the amp has been on a while?  If so it could be vibration coming from output transformer oscillation, which would be bad.  This shouldn't happen as long as there is a load on the circuit (aka you have headphones plugged into the jack).

 
The hum is constant, from the start up to when I turn it off. Oh well could be anything, could be I'm spoilt by Hashimoto/Tango and the likes 

.
 
I've sent the Icon back today - with a note hoping they would at the very least check if something is loose inside the main transformer. I also did grab the capacitor upgrade from Icon - might as well be the first to hear both the stock and the SE version (sans the tube upgrade of course). Mundorfs S/G/O and Duelund also on the way, but they gotta sit inside my drawers for several weeks I guess.

 

[Xcalibur255]

Okay I did some checking and timed it so I could have total silence in the room (no running A/C, refrigerator, ect.).  With the LCD-2 I cannot detect any hum or background noise whatsoever at any of the 3 gain settings when no music is playing.  There is just dead silence.  So I grabbed my JVC HARX-900's I usually only use for late night TV watching and repeated.  On the low gain setting there is an incredibly slight amount of hum, at the threshold of being undetectable.  It gets very slightly louder on medium, and a bit louder again on high.  You don't have to strain to hear it on high, the hum is evident, but at a level I still feel is slight and not objectionable at all.  Volume setting has no effect on this, the level is constant.  The JVCs are quite sensitive, they hum loudly on my OTL amp when I'm running 5998 tubes to the point where it is a waste of time to even try listening to music on them that way.  I also noted some static/hiss that increases with volume on the JVCs on high gain.  Slightly more noticeable than the tranny hum was at higher volumes with no music playing.  With the JVCs I can also detect microphonics from the Tung Sols.  A tap on the metal cart the amp sits on produces some slight pinging I already knew these tubes were guilty of when they vibrate.
 
For clarity sake, I cannot hear any of this whatsoever with music playing, these observations are all with no music being played.
 
Hopefully this helps.  Some other factors such as the stability of the incoming power and what other gear is feeding the HP8 might have an impact too.

 

[Xcalibur255]

On a side note, the JVCs are pretty listenable on the HP8.  Best sound I have heard from these modest headphones.  I'll have to try my other forgotten/neglected headphones I have lying around.

 

[Xcalibur255]

My HP8 got its cap upgrade today:  NOS Soviet K40Y paper in oil caps.  I wasn't quite prepared for how much bigger they were than the tiny stock caps.  They are at least 6x in size.  It's a good thing the inside of the amp isn't crowded in that area or they would not have fit, as it was they just barely fit in there.
 
Now the break-in clock gets reset since I know from experience these caps need it.

 

[khaine1711]

Just dropping in to say I got my Icon back today. Turnaround time is ~5 working days. Here's the cap upgrade. Impression compared to stock caps coming soon.
 

 
Also the rattling sound I mentioned earlier turns out to be the spare fuse in the fuse box. Nothing went loose inside the Icon.
 
The best part is the unit is completely free of hum now, even on the High setting (with the He-6). Icon said they did replace another capacitor (not the two jensen) to reduce the hum.
 
Overall I'm happy; especially when I have a (literally) drawer of 5751s heading toward England 

 

[Xcalibur255]

We'll have to compare notes. The K40 and the Jensen are supposed to be fairly similar sounding. I was able too get my caps in on each side since they are not as thick as the Jensens. They are longer though so that came with its own challenges.

I'm very pleased with the improvement I got. I actually agree with the positive reviews now. The stock cap was a major bottleneck for sound quality for this amp.