ZMF Aegis Official Thread

[SunRa Fan]

I’m sure all of these kt88 and kt90 tubes being discussed sound good but I’m still puzzled as to why they are attractive tubes for headphone amplifiers. There’s quite a premium for the high power capabilities that just aren’t used in headphone amps. I only listen via speakers and I don’t need what the kt88 can do. What’s the appeal of high power tubes like kt88, 6550, el34, etc. in amps like this?

Pure sound only. Someone a few posts back is using KT120s I believe. Chasing it.

 

[Wes S]

I dig this type of tightness with planar headphones. Could definitely be too tight and contrasty with dynamics though

I completely agree.

 

[L0rdGwyn]

I’m sure all of these kt88 and kt90 tubes being discussed sound good but I’m still puzzled as to why they are attractive tubes for headphone amplifiers. There’s quite a premium for the high power capabilities that just aren’t used in headphone amps. I only listen via speakers and I don’t need what the kt88 can do. What’s the appeal of high power tubes like kt88, 6550, el34, etc. in amps like this?

Generally speaking, as it isn't always the case, these higher power tubes have higher transconductance, which in a cathode follower design means lower distortion, higher bandwidth, lower output impedance. It's the same reason pass regulators tubes are often used in OTL circuits, they are high current, high transconductance devices (by tube standards). You aren't getting more power output in this amp, but you are putting the transconductance of the tubes to use, which is reflected in the sound.

 

[betula]

Out of curiosity, how complicated is it to modify the commercial Aegis to accept any kind of 274B rectifiers? I know, it is possible to modify the DIY Aegis to accept 5U4G/U52 tubes, so I thought it could be a similar process on the Cayin made Aegis just the other way around? (I also know that the SE 274B works in the commercial Aegis, but some users reported issues with that too and I am wondering about other brands anyway.)

 

[theveterans]

Out of curiosity, how complicated is it to modify the commercial Aegis to accept any kind of 274B rectifiers? I know, it is possible to modify the DIY Aegis to accept 5U4G/U52 tubes, so I thought it could be a similar process on the Cayin made Aegis just the other way around? (I also know that the SE 274B works in the commercial Aegis, but some users reported issues with that too and I am wondering about other brands anyway.)

This should be as easy as the DIY version

 

[Isaacc7]

Generally speaking, as it isn't always the case, these higher power tubes have higher transconductance, which in a cathode follower design means lower distortion, higher bandwidth, lower output impedance. It's the same reason pass regulators tubes are often used in OTL circuits, they are high current, high transconductance devices (by tube standards). You aren't getting more power output in this amp, but you are putting the transconductance of the tubes to use, which is reflected in the sound.

Well, today I learned something new. Thanks!

 

[iamoneagain]

Burned the ACME KT88s for 24hrs and swapped in a good front end to see where things have fallen sound wise. They retain their great clarity but also they've remained warm, so that last bit of air and resolution such as with the Ray Select KT88 that I was hoping for...isn't there. Still a very good tube. For when you want to listen to the Caldera as though it were an Atrium but with more detail. So in the end it does NOT compete well with the Ray KT88s as I said prematurely. The ACMEs are darker and warmer but with a lovely delicacy. It has a tad bit more body to voices as well which comes through nicely on the Caldera. Like most of you, I've been through quite a few tubes that in the end I wind up not going back to and these don't fall into that category. It's an interesting tube. The EH KT90s remain my favorite for the Caldera..for when you want to hear everything they put on tape.

So giving kt90’s another listen now that I’ve switched to 1/4 output in low impedance with ZMF 2k Copper cable vs XLR in low with Verite Silver. I’ve been loving the Gold Lion kt88’s since they‘ve burned in. So to be honest with you, in this current setup, I wouldn’t be able to tell the kt88’s were swapped with the kt90’s. Both sound excellent and so very close. It’s possible now the kt90’s has hint more holographic sound where sounds float behind and front better than kt88’s. They both sound really sweet in the mids with great punchy bass and crystal clear highs.

Listening to Keene’s Hope and Fears, which has pretty dynamic sound. Had just listened to it with the kt88’s so should be easy to pick out differences but not really hearing them. Possible kt90 has slight hint of better precision but hard to say. So at this point I can just keep the kt90’s and be good. Or put back the Gold Lion kt88’s and just as good. I kind of like having all NOS tubes, going to leave in the kt90’s and keep kt88’s as backup. Strange now sound so close when preferred kt88 in past but I guess now using 5 ohms output with Caldera might have had an impact.

To note: rectifier Mullard gz34 f31 fat base, input RCA 5691 red base

 

[SunRa Fan]

So giving kt90’s another listen now that I’ve switched to 1/4 output in low impedance with ZMF 2k Copper cable vs XLR in low with Verite Silver. I’ve been loving the Gold Lion kt88’s since they‘ve burned in. So to be honest with you, in this current setup, I wouldn’t be able to tell the kt88’s were swapped with the kt90’s. Both sound excellent and so very close. It’s possible now the kt90’s has hint more holographic sound where sounds float behind and front better than kt88’s. They both sound really sweet in the mids with great punchy bass and crystal clear highs.

Listening to Keene’s Hope and Fears, which has pretty dynamic sound. Had just listened to it with the kt88’s so should be easy to pick out differences but not really hearing them. Possible kt90 has slight hint of better precision but hard to say. So at this point I can just keep the kt90’s and be good. Or put back the Gold Lion kt88’s and just as good. I kind of like having all NOS tubes, going to leave in the kt90’s and keep kt88’s as backup. Strange now sound so close when preferred kt88 in past but I guess now using 5 ohms output with Caldera might have had an impact.

I use the ZMF GSP cable terminated in XLR at medium impedance for the Caldera which is a significant improvement in resolution over the 2K, which is also a lovely cable on its own if you can say such a thing. The front end on the Aegis is the RCA 5R4GY DD with 5691 reds. With these variables, the EH KT90 exhibits a unique quality that I haven't found in any other tubes yet. To my ears it "goes to 11." Another way of putting it is that tracks have this illuminated quality that is very seductive to the ear. I do also have the Gold Lions but haven't spent much time with them yet(bought at the same time as the ACMEs). My second best tube for the Caldera is the Ray Select KT88, which exhibits the kind of air and resolution the KT90s offer but without that Je ne sais quoi that makes them special. I wish I could describe it better, but perhaps you did it best above. Holography.

 

[theveterans]

KT88 or KT90 + planar headphones = magic

Getting goosebumps right now with Susvara and TJ Full Music KT88/c sa well. Just sounds so special that one would even be shocked that this very seductive tone is coming from Susvara. Aegis with KT88 just ticks all of Susvara's romantic buttons to 11

 

[jonathan c]

Are those actually TungSols?

..... I believe that NJRT Company bought a portion of remaining stock of Tung-Sol 6SL7 when production of those was being wound down .....

 

[iamoneagain]

I use the ZMF GSP cable terminated in XLR at medium impedance for the Caldera which is a significant improvement in resolution over the 2K, which is also a lovely cable on its own if you can say such a thing. The front end on the Aegis is the RCA 5R4GY DD with 5691 reds. With these variables, the EH KT90 exhibits a unique quality that I haven't found in any other tubes yet. To my ears it "goes to 11." Another way of putting it is that tracks have this illuminated quality that is very seductive to the ear. I do also have the Gold Lions but haven't spent much time with them yet(bought at the same time as the ACMEs). My second best tube for the Caldera is the Ray Select KT88, which exhibits the kind of air and resolution the KT90s offer but without that Je ne sais quoi that makes them special. I wish I could describe it better, but perhaps you did it best above. Holography.

Interesting that you like that combo. The RCA 5R4GY DD and the kt90’s didn’t sound good to me. It gave me this weird concert-hall reverb effect. Didn’t sound right to me. Also the gz34 fat base has more power, speed and precision. As far cable, I chose the 2k over the GSP because I was looking for more warmth over the Verite and wasn’t concerned about getting ultimate resolution. The medium impedance with XLR seems to make things very dynamic but at the cost of the mids. I’m finding the 5 ohm single ended output has the best control over the bass with a nice warmth and texture while being better balanced. Just something more natural and organic. But we all have different tastes. But at least got me to give kt90’s another shot.

 

[SunRa Fan]

Interesting that you like that combo. The RCA 5R4GY DD and the kt90’s didn’t sound good to me. It gave me this weird concert-hall reverb effect. Didn’t sound right to me. Also the gz34 fat base has more power, speed and precision. As far cable, I chose the 2k over the GSP because I was looking for more warmth over the Verite and wasn’t concerned about getting ultimate resolution. The medium impedance with XLR seems to make things very dynamic but at the cost of the mids. I’m finding the 5 ohm single ended output has the best control over the bass with a nice warmth and texture while being better balanced. Just something more natural and organic. But we all have different tastes. But at least got me to give kt90’s another shot.

You know, for all the effort we put into sharing great sound synergies we're still left with the fact that no two tubes sound exactly the same, not to mention the fact that hearing differs between us all. For instance, the "weird concert hall reverb effect" you describe does not occur with my setup. I hear an excellent holographic soundstage with enough clarity and separation to hear what everyone is doing and where they're doing it from. When I hear this I feel that this combination is FULLY exploiting the Caldera. If only it were so simple to get the same result for everyone else here.
Would that it were so simple

 

[iamoneagain]

You know, for all the effort we put into sharing great sound synergies we're still left with the fact that no two tubes sound exactly the same, not to mention the fact that hearing differs between us all. For instance, the "weird concert hall reverb effect" you describe does not occur with my setup. I hear an excellent holographic soundstage with enough clarity and separation to hear what everyone is doing and where they're doing it from. When I hear this I feel that this combination is FULLY exploiting the Caldera. If only it were so simple to get the same result for everyone else here.
Would that it were so simple

So strange, just put the The RCA 5R4GY DD back in and no longer hear the strange soundstage. It sounds right. But I understand why you’re using the better headphone cable. The RCA rectifier is lacking clarity compared to the Mullard. And it’s lacking precision. It’s a nice sound but I would be looking for a better cable as well. But with the Mullard gz34 fat base f31, the 2k Copper works since don’t think I’d need anymore clarity. Also the RCA is missing the high end sparkle of the Mullard. Be aware this is only with the f31 fat base version. The f32 resolution is probably about the same as the RCA, the fat base brings things to another level but it cost a lot more but to me worth it. Haven’t heard the metal base version but read the fat base has stronger bass, so that would be my preference.

Edit: sorry I was editing it and got few likes before the edit. It’s early on West Coast so thought had time to delete what’s no longer true.

Just did quick comparison with The Halo Benders - Virginia Reel Around the Fountain and with Mullard the separation and layering are definitely on another level. It’s possible someone still might prefer the RCA since it’s smoother and guitar is less harsh but find it accurate with the Mullard. The Mullard also has much tighter bass control.

 

[AnyDave]

So strange, just put the The RCA 5R4GY DD back in and no longer hear the strange soundstage. It sounds right. But I understand why you’re using the better headphone cable. The RCA rectifier is lacking clarity compared to the Mullard. And it’s lacking precision. It’s a nice sound but I would be looking for a better cable as well. But with the Mullard gz34 fat base f31, the 2k Copper works since don’t think I’d need anymore clarity. Also the RCA is missing the high end sparkle of the Mullard. Be aware this is only with the f31 fat base version. The f32 resolution is probably about the same as the RCA, the fat base brings things to another level but it cost a lot more but to me worth it. Haven’t heard the metal base version but read the fat base has stronger bass, so that would be my preference.

Edit: sorry I was editing it and got few likes before the edit. It’s early on West Coast so thought had time to delete what’s no longer true.

Just did quick comparison with The Halo Benders - Virginia Reel Around the Fountain and with Mullard the separation and layering are definitely on another level. It’s possible someone still might prefer the RCA since it’s smoother and guitar is less harsh but find it accurate with the Mullard. The Mullard also has much tighter bass control.

I think it also depends on what preamp and power tubes it's paired with.

But yeah, preferences go a long way with this sort of thing. 5AR4/GZ34 tubes have been my least favorite in the Aegis, while other folks find them to be the best. It's what makes tube rolling so fun and interesting.

 

[iamoneagain]

I think it also depends on what preamp and power tubes it's paired with.

But yeah, preferences go a long way with this sort of thing. 5AR4/GZ34 tubes have been my least favorite in the Aegis, while other folks find them to be the best. It's what makes tube rolling so fun and interesting.

So I believe you use the Chord Dave with Mscaler. I was going to say going from the RCA to the Mullard was like adding the mscaler to the Dave. Brings the clarity, separation and layers to another level. So I can imagine if already starting with this as your source, the gz34 is going to be hyper real and probably no longer musical.

I’m using a Naim HE, which some might claim is mid-fi compared to the Chord setup but I prefer its sound signature of having more PRaT with more bass presence. Previously owned the Chord combo before the Naim. So could be that my preference on tubes is balancing out the Naim HE and increasing the resolution. Vs starting out with ultimate resolution and softening it a hint. Same with how cables increase/decrease clarity and warmth.

But even if we were all listening to the exact same setup, we’d come away with different impressions. I’ve seen this at CamJam. We all have our own preferences and also hear differently. So when making decisions based off others, have to take all that into consideration. I bought RCA rectifier based off rave reviews but was disappointed but other hand gz34 fat base also highly recommended and worked out for me.