[Spakka]

So, I have a quick question now I have the capacitors (delivered rather quickly!)...
 
I have the Jensen ones and they suggest placing them so that the outer foil is closest to the grounded side of the circuit (the output stage?) and the inner foil is closest to the positive side - I think this means the inner foil (which is marked by the black line on the cap) should be connected to the 6SN7, and the unmarked outer side to the 12AX7.
 
Is this correct?
 
 
 
 
 
Edit: This appears to be the case from the pictures posted in the thread, but it's not 100% clear as pics blurry/small.

 

[Spakka]

So I have inserted the new caps... 
 
And, whilst I obviously can't A/B, I was feeling very cynical that I would be able to hear any difference... There definitely is a reasonably sized improvement - Bass is certainly improved, and I'm fairly sure that the higher end is a tad clearer. Of course it's hard to tell with certainty, but overall seems like an improvement well worth the cost!

 

[Xcalibur255]

The caps are new.  Run the amp as much as possible and put about 100 hours on the new parts, then listen again.  You'll be impressed all over again.

 

[lithium1085]

It seems that Icon audio has gone ahead and updated the HP8 with custom CV181 tubes.
 
http://www.musicdirect.com/p-164284-icon-audio-hp8-mkii-cv181-triode-tube-headphone-amp.aspx
 
 
I also had a question about the MP3 amplifier. Has anyone tried them with high sensitivity circumaural headphones ?

 

[PTom]

audioaffair.co.uk told me that Icon Audio are updating the HP8 MKII so I contacted Icon Audio directly regarding the specific upgrades and received the following reply:
 
"The new version has some circuit improvements, improved cosmetics and a “loop through” facility for those with limited inputs/outputs."
 
They also mentioned that they have a more expensive signature edition with Jensen caps and valve upgrades.

 

[lithium1085]

  audioaffair.co.uk told me that Icon Audio are updating the HP8 MKII so I contacted Icon Audio directly regarding the specific upgrades and received the following reply:
 
"The new version has some circuit improvements, improved cosmetics and a “loop through” facility for those with limited inputs/outputs."
 
They also mentioned that they have a more expensive signature edition with Jensen caps and valve upgrades.

hmm.. So there will still be a 6SN7 version available? I am not sure if I interpreted that correctly...

 

[PTom]

I think so, the specs on their website seems to indicate that they are using 6SN7 valves. 
http://www.iconaudio.com/portfolio-item/icon-audio-hp8-mkii/

 

[PTom]

I'm not sure what exactly he meant when he said that the upgraded version had "some circuital improvements".

 

[khaine1711]

  I'm not sure what exactly he meant when he said that the upgraded version had "some circuital improvements".

It's actually out for quite a while. The one on Icon site is still the old Hp8 mkII (which project86 reviewed) with the power switch on front. The "new" version have the power button on the side, stereo/mono switch on the front and revised impedance setting.  
 
I didn't keep that email last year but I recall Icon calling that version the Hp8 Mk2.2 

 

[lithium1085]

  It's actually out for quite a while. The one on Icon site is still the old Hp8 mkII (which project86 reviewed) with the power switch on front. The "new" version have the power button on the side, stereo/mono switch on the front and revised impedance setting.  
 
I didn't keep that email last year but I recall Icon calling that version the Hp8 Mk2.2 

 
Thanks for the info. What exactly have they revised in the impedance settings?

 

[khaine1711]

I need to dig up the manual again but it was a very minor change I think the mid setting goes down from 300 ohm to 250 ohm. Will confirm back later. Also I forgot to mention the Mk2.2 got slightly better volume pot than the MkII.
 
Anyway if you order after  I think June last year, you'll always get the Mk2.2 (with the copper plate). Was quite surprised myself when I received mine and it looks nothing like the picture .
 
On another note, the US site (musicdirect) is slightly strange. Me and Excalibur have both emailed Icon and was told not to use the Cv 181 in place of the 6sn7. You can only use the Shuguang Cv181 which is technically a 6SN7, but all other "real" Cv181 can't be used.

 

[lithium1085]

  I need to dig up the manual again but it was a very minor change I think the mid setting goes down from 300 ohm to 250 ohm. Will confirm back later. Also I forgot to mention the Mk2.2 got slightly better volume pot than the MkII.
 
Anyway if you order after  I think June last year, you'll always get the Mk2.2 (with the copper plate). Was quite surprised myself when I received mine and it looks nothing like the picture .
 
On another note, the US site (musicdirect) is slightly strange. Me and Excalibur have both emailed Icon and was told not to use the Cv 181 in place of the 6sn7. You can only use the Shuguang Cv181 which is technically a 6SN7, but all other "real" Cv181 can't be used.

If you look at the musicdirect picture closely, the CV181 tube is labelled as David Shaw. I believe based on their new brochure for 2014 that these are custom CV181s made to order for Icon. 

 

[Xcalibur255]

They are likely having Shuguang make a customized version for them.  Or possibly TJ, which would be better actually as the Full Music are decent tubes.  Seems like marketing to me, the bigger glass looks cooler to most people. 
 
Electrically it is a 6SN7, a true vintage CV181 valve draws 50% more heater current and would fry the amp.  Shuguang uses this glass style and calls their Treasure series a CV181 as a marketing ploy.  They are nice 6SN7s, but that is what they are:  6SN7s.  Personally my suggestion to new owners of this amp is to grab a pair of Sylvania 6SN7GTB wedge plates for around $25 and go from there.  The new production tubes are very expensive for the performance they offer.

 

[khaine1711]

I agree, cheap pair of NOS Sylvania 6SN7 and a GE 5751/12ax7 Gold lion gotta be the best bang for bucks rolling option for this amp. Might as well stop there and not thinking about BGRP and Osram and other exorbitant 6SN7s haha.

 

[Xcalibur255]

The Gold Lion coaxes the best resolution out of the amp for sure, it actually beats NOS tubes and sounds very linear too.  I have stuck with my Sylvania 5751 because it lowers the gain enough to make the transformer hum completely inaudible for me.  That the Gold Lion sounds more resolving despite the higher noise floor is really saying something.
 
I do think the amp gains something with the more "famous" 6SN7s in place, but diminishing returns kicks in pretty strongly so it's only really practical for people like you and me who had an existing collection to throw at the amp.  The cap upgrade made tube rolling more satisfying, changes in tone and presentation were a lot easier to detect afterwards.
 
I've been meaning to put the Tung Sol BGRP back in, my hunch is they'll mesh very well with the K712.