Thought I’d share a couple of impressions that have really changed my opinion of this amp for the better, and practically completely fixed the hum / hiss issue.
Like many of you, I use the HA-6A with high impedance cans, in my case the ZMF VCs and Aeolus. And, like many of you, this combination leads to an audible noise floor that can range from kinda quiet to very distracting. For me it was affected most by different 12AU7 tubes, but there was no rhyme or reason - I have some that are dead quiet, some that are ridiculously loud, and more than one pair of certain types that fall into both camps.
I’d got to the point where I was trying other amps to see if I could get the same sound but without the problems. One of my favourites was the Feliks Euforia AE, but not for the sound signature. It was way too neutral, but it did have an enormous soundstage - it filled every corner of the headphones, if that makes sense. It was also super quiet, but the sound didn’t have that particular tube magic, so it was sent back.
Then I happened across a comment over in the ZMF VC thread, where another user recommended the HA-6A for them, but only with an adapter. Curious, I messaged to find out what adapter they meant, and was put in touch with Skedra. Turns out Skedra also owns the HA-6A along with the ZMF VCs, and he also found the noise floor bothersome. Fortunately he also makes high-end cables over at Viking Audio, and decided to make himself an impedance adapter to fix the hiss problem.
After a bit of back and forth I ordered one, and it arrived super quick. It’s a short balanced adapter with a choice of litz cables, with the magic sauce being resistors built into the XLR connectors.
The difference it's made to my amp is night and day. The background is black, I’ve got way more play with volume, and I can now tube roll again without hiss being a deciding factor. I can hear all the different characteristics of my tubes, and can listen to scores with a wide dynamic range again. It’s almost like getting a brand new amp, and it’s put a stop to me hunting for a new one.
The second impression is of some KT-88 tubes, specifically the PSvane Mk-II versions. These are a touch more neutral than the ones that come as stock, but they have much better extension at both ends. Better still, the soundstage increases in width, but particularly in height. Using these almost rivals the soundstage I was getting from the Feliks Euforia, and now I get the black background thanks to the adapter, too. As for the 12AU7s (for those interested), I've found that I prefer either RCA Clear Tops for a really wide and detailed sound without fatigue, or the Mullard CV4003 for a similar sound but with more focus on the mids and slightly less top end extension. Both options still sound thick and lush in the mids, but with loads of detail thanks to the Psvane Kt88s.
If you’re interested in ordering one of the impedance adapters just drop Skedra a message. The guy is super helpful, very knowledgeable, and his work is spot on.
Like many of you, I use the HA-6A with high impedance cans, in my case the ZMF VCs and Aeolus. And, like many of you, this combination leads to an audible noise floor that can range from kinda quiet to very distracting. For me it was affected most by different 12AU7 tubes, but there was no rhyme or reason - I have some that are dead quiet, some that are ridiculously loud, and more than one pair of certain types that fall into both camps.
I’d got to the point where I was trying other amps to see if I could get the same sound but without the problems. One of my favourites was the Feliks Euforia AE, but not for the sound signature. It was way too neutral, but it did have an enormous soundstage - it filled every corner of the headphones, if that makes sense. It was also super quiet, but the sound didn’t have that particular tube magic, so it was sent back.
Then I happened across a comment over in the ZMF VC thread, where another user recommended the HA-6A for them, but only with an adapter. Curious, I messaged to find out what adapter they meant, and was put in touch with Skedra. Turns out Skedra also owns the HA-6A along with the ZMF VCs, and he also found the noise floor bothersome. Fortunately he also makes high-end cables over at Viking Audio, and decided to make himself an impedance adapter to fix the hiss problem.
After a bit of back and forth I ordered one, and it arrived super quick. It’s a short balanced adapter with a choice of litz cables, with the magic sauce being resistors built into the XLR connectors.
The difference it's made to my amp is night and day. The background is black, I’ve got way more play with volume, and I can now tube roll again without hiss being a deciding factor. I can hear all the different characteristics of my tubes, and can listen to scores with a wide dynamic range again. It’s almost like getting a brand new amp, and it’s put a stop to me hunting for a new one.
The second impression is of some KT-88 tubes, specifically the PSvane Mk-II versions. These are a touch more neutral than the ones that come as stock, but they have much better extension at both ends. Better still, the soundstage increases in width, but particularly in height. Using these almost rivals the soundstage I was getting from the Feliks Euforia, and now I get the black background thanks to the adapter, too. As for the 12AU7s (for those interested), I've found that I prefer either RCA Clear Tops for a really wide and detailed sound without fatigue, or the Mullard CV4003 for a similar sound but with more focus on the mids and slightly less top end extension. Both options still sound thick and lush in the mids, but with loads of detail thanks to the Psvane Kt88s.
If you’re interested in ordering one of the impedance adapters just drop Skedra a message. The guy is super helpful, very knowledgeable, and his work is spot on.
