[Pharmaboy]

Hello, please let me present my candidacy to join this select and iconic group.

After much reading and researching (surely you all know what I’m talking about) I decided to go with the Icon HP8 for my first tube amp. I got this one from the classifieds last week. It’s not the Signature version, just MKII, but if it sounds this good, I can't imagine how fantastic the Signature version will be. My intention though is to update the Caps at some point, but for now I'm not letting it go anywhere




The HP8 MKII came with its original tubes, 2 x David Shaw and 1 x JJ 12AX7, but I also got two additional NOS tubes from the seller (well, NOS but used), one RCA 12AX7 from 1970 made by Mullard and one RCA 12AX7 Black Plates from 1950 (long plates)

I have tried the 3 driver tubes and to my ears there are subtle differences but always maintaining the wonderful sound signature of this fantastic amp

My first Wow moment came with the stock tubes, with that thick and bold sound yet very detailed, deep and tight bass, lush and liquid mids and very pleasant and controlled highs. Great holographic image with a good soundstage. The soundstage was not as huge as I expected, but it was still a very good size.

The RCA Black Plates brought more detail and air, with better separation and bigger stage. Also (even) better bass and extended treble. This tube works very well with rock, blues, etc, but with Classical the high frequencies are a bit harsh sometimes (violins for example) to my ears (maybe this is due to my chain too)




And finally, the RCA 12AX7 made by Mullard, that is my favorite now, gives a smooth, musical and detailed sound, with nice warm mids, which works very good with Jazz, acoustic and Classical, that are the main genres I tend to listen




I have read entirely this thread and there are plenty of tube recommendations (thanks for that!) But, among all of them, which would be your choice to get a smooth, musical and warm yet detailed sound with big and holographic soundstage? (Both power and driver). I think my next purchase will be Brimar 12AT7 CV455 KB/FB to get a bit more headroom in the volume pot, but I don’t know which is the sound signature that this tube can provide


Well, and that’s all. I’m very happy with this little but powerful amp, and now I can see how many people loves this lush and euphonic sound coming from theses little glass bubbles made 50-60 years ago

Great write-up! Welcome to the very select HP8 club (not really ... I just like typing that).

Brimar CV455s are among the best 12AT7s I've tried. I have a couple of Mullards -- I've never heard a NOS Mullard input tube I couldn't like. I didn't care for any 12AX7s until a friend sent me an Amperex ‘fisher’ 12AX7 (1959). It's an impressive tube that really locks in with the matched 1951 Sylvania 6SN7GT/GTAs I've used as power tube for the past year. The Sylvanias slam & do bass like crazy, plus big mids and not expecially extended treble. The Amperex/Fisher tube also slams, too, top to bottom. I like the resulting synergy.

 

[jonathan c]

For impedance loading with ZMF dynamic driver headphones, I'm an "H" .

 

[Pharmaboy]

For impedance loading with ZMF dynamic driver headphones, I'm an "H" .

This comment will probably be self-indicting, but when I tried all 3 impedance settings with my VO, I couldn't really distinguish their sound in any real way except volume. The fact that volume varied with the 3 settings may have obscured differences between their sound for me...? I just don't know.

I ended up switching to "Medium" and leaving it there. I like what I'm hearing to the point that I stopped caring about experimenting with impedance.

 

[Rollnrock]

This comment will probably be self-indicting, but when I tried all 3 impedance settings with my VO, I couldn't really distinguish their sound in any real way except volume. The fact that volume varied with the 3 settings may have obscured differences between their sound for me...? I just don't know.

I ended up switching to "Medium" and leaving it there. I like what I'm hearing to the point that I stopped caring about experimenting with impedance.

I have settled on "High" but I could also live happily with "Medium"

I think there may be more "meat" in the notes with "High" but no too much difference to my ears

 

[Rollnrock]

For a 'first tube amp', HP8 Mk II is one hell of a start!! With the cap upgrades, select tubes -- music 'manna from heaven' is yours!!

@Rollnrock Congrats! You got a very nice set up to start off. If you decide to upgrade the capacitors later the team at Audioarcan in Ontario were able to work on mine and it was a pleasure to coordinate with them. I've done a little bit of tube rolling with it and did switch out a stock ECC83(12AX7) Psvane valve that originally came with mine that seemed a bit bright/edgy. I used this guide: https://www.thetubestore.com/12ax7-tube-reviews?12ax7-tube-reviews=undefined&goto=5751

I'm using a NOS JAN-Philips 5751 to smooth the gain stage. For the 6SN7's I have a couple sets of vintage GE and Sylvanias. Currently I'm using a pair of new Linlai high shoulder tubes. It is hard for my old ears to tell much of a difference on swapping the 6SN&'s but I do acknowledge the powerful presentation of the music with the HP8. It immediately impressed with it's strong presence. All my HP's sound fantastic on it and the adjustable impedance tap works nicely with both dynamics and planar. ZMFs seem to like the Mid setting on the output impedance.

Great write-up! Welcome to the very select HP8 club (not really ... I just like typing that).

Brimar CV455s are among the best 12AT7s I've tried. I have a couple of Mullards -- I've never heard a NOS Mullard input tube I couldn't like. I didn't care for any 12AX7s until a friend sent me an Amperex ‘fisher’ 12AX7 (1959). It's an impressive tube that really locks in with the matched 1951 Sylvania 6SN7GT/GTAs I've used as power tube for the past year. The Sylvanias slam & do bass like crazy, plus big mids and not expecially extended treble. The Amperex/Fisher tube also slams, too, top to bottom. I like the resulting synergy.

Just wanted to thank you for your kind comments (and useful info)!

All the impressions/thoughts/comments that you and all the folks have posted here are the reason why I have purchased this little gem. And I couldn't be happier!

 

[JerseyD]

Just wanted to thank you for your kind comments (and useful info)!
All the impressions/thoughts/comments that you and all the folks have posted here are the reason why I have purchased this little gem. And I couldn't be happier!

Need to get to work on those wood "ZMF X Icon Audio Super Secret Select Club" membership cards, shirts and hats. We would be the fashion Icons of any CanJam!

 

[lauthoerer]

While you're at it, guys, can you also check if the impedance settings corresponds to any perceived hum?

As described before, on my ZMFs (VC + BC), sadly, I'm far from a "black" noise floor, and instead get a discernable "ground hum" which seems to be treatable with the right set of cables (AC and HP cables). Silver makes it worse, copper makes it less. Interconnects (DAC > HP8) don't seem to make any difference. The higher the impedance, the worse it gets as well. Apart from the hum, seems to me like the "high" impedance suits well for the VC.

If none of you have any "humming" to report (ZMF or otherwise), that would be interesting as well. Not quite sure if that is the case from your previous helpful comments.

Still want to narrow the issue down as much as possible before reaching out to icon Audio to ask for an authorized shop in Germany to possibly send it in.

 

[WorksUnit]

I have issues with hum between the low and medium settings, particularly the low.
It's almost like a sweet spot between them where it just drops off.
I worked some Deoxit in and the issue seemed to improve....
It's one thing I'm interested in getting fixed when booked in for a service for sure.

 

[Rollnrock]

While you're at it, guys, can you also check if the impedance settings corresponds to any perceived hum?

As described before, on my ZMFs (VC + BC), sadly, I'm far from a "black" noise floor, and instead get a discernable "ground hum" which seems to be treatable with the right set of cables (AC and HP cables). Silver makes it worse, copper makes it less. Interconnects (DAC > HP8) don't seem to make any difference. The higher the impedance, the worse it gets as well. Apart from the hum, seems to me like the "high" impedance suits well for the VC.

If none of you have any "humming" to report (ZMF or otherwise), that would be interesting as well. Not quite sure if that is the case from your previous helpful comments.

Still want to narrow the issue down as much as possible before reaching out to icon Audio to ask for an authorized shop in Germany to possibly send it in.

Hello, I don't detect any background noise while listening to music, only when I have my phone nearby. I try to keep it away when listening

Yesterday I tested with the headphones connected but without music. Turning the volume up to 12 o'clock or more I can hear a soft hum, mainly at high impedance. But fortunately it doesn't bother me when I listen to music (usually I don't go above 9 - 9:30 on the volume knob)

I hope you can solve it soon

 

[infinity3914]

Sorry for taking so long with my report, but here are my observations that might help someone. Similar to @lauthoerer, my HP8 is only about 99% pitch-black. The hum and static are the loudest at the "high" impedance, inaudible at "medium", and non-existent at "low".

While you're at it, guys, can you also check if the impedance settings corresponds to any perceived hum?

As described before, on my ZMFs (VC + BC), sadly, I'm far from a "black" noise floor, and instead get a discernable "ground hum" which seems to be treatable with the right set of cables (AC and HP cables). Silver makes it worse, copper makes it less. Interconnects (DAC > HP8) don't seem to make any difference. The higher the impedance, the worse it gets as well. Apart from the hum, seems to me like the "high" impedance suits well for the VC.

If none of you have any "humming" to report (ZMF or otherwise), that would be interesting as well. Not quite sure if that is the case from your previous helpful comments.

Still want to narrow the issue down as much as possible before reaching out to icon Audio to ask for an authorized shop in Germany to possibly send it in.

• At the "low" impedance level, which is more suitable for my Empyrean 2 (32 ohms), the background is about 99% quiet as the radio station's conversations are extremely quiet, infrequent, and on the right channel. I can deal with this since I usually have music playing and the RF is negligible and ignorable. It's only problematic for genres like orchestra and ambiance due to the quiet passages, and during the transition between songs. Nevertheless, I can deal with this as I'm working and not noticing the noise as much.
• At the "medium" impedance level, which I exclusively use for my Atrium (300 ohms), the background is also about 99% quiet. Without music, I need to focus hard to detect the faint radio station's conversations. With music, the RF's noise is also negligible, and only noticeable for orchestra and ambience. The background hum and static are still here, but in my experience this might just be the classic "tube amp warmth". To my ears, they are not annoying nor piercing, but only add to the music.
• At the "high" impedance level, the hum and static are most prominent on the left channel and unbearable - it reminds me of the old TV static sound lol. If there's a treatment to induce schizophrenia and psychosis, this is it.

I observed that the hum was not dependent on driver tubes or pre-amp tubes, and was mildly dependent on the cable material and to a certain extent, the headphones' impedance. When I tested the Meze silver cable with the Atrium, the hum was louder than that in the ZMF copper cable. When I tried the copper cable with the Empyrean 2, the hum was louder than in the silver cable. These observations were confusing, but I've always loved the lushness and warmth of the copper cable in my Atrium so this didn't bother me. Additionally, this phenomenon did not happen at my old apartment on the ground floor facing away from the giant cell tower, so I suspect the cell tower and electricity's cleanliness had something to do with it.

What I found helped me the most was the copious amount of ferrite beads. I have 5 strapped on each cable - 1 right out of the amp, 1 middle of the cable, 1 right before the Y-splitter, and 1 on each side coming into the headphones, 2 on the power cables, and 4 on the the RCA cables. Coiling the headphones cable also helps moderately, but this is unreliable. What didn't help much or was insignificant in reducing the hum were the iFi GND Defender (tried on my PC, my DAC, and the HP8), different power strips with the "ground" features, and the Faraday fabric. What made it worse though, was these cheap ass RCA cables I used for testing. I'd burn these if I could.

I didn't go through with @JerseyD's recommendation of the Blue Jeans RCA cables and @geoffalter11 and @JerseyD's recommendations of a better power conditioner (ex. Pine Tree Audio Power Filter) because I've been swamped with my thesis and I'm comfortable with the "low" and "medium" impedance setting. Once I have more free time these are next on my list. I do have the option to bring the HP8 to my local amp repairman, but he's been taking too long to repair my QSA.

Anyway, @lauthoerer, based on my observations, I think the ferrite beads, the Blue Jeans RCA cables, and the Pine Tree Power Filter are worth a try. The beads are abundant on Amazon so returning is easy. The Power Filter can be used on your other systems so it's still a functional purchase. Hope this helps!