ZMF Aegis Official Thread

[L0rdGwyn]

Huh, the 6cg7 is functionally the same as a 6sn7. You could put those into the 6sl7 slot and not need any adapters. Of course good versions of those are quite a bit more expensive. Thought @L0rdGwyn said the 6sn7 wasn’t compatible? I guess since you’re limiting the type of headphone it’s working ok for you.

Since you already have the adapters you might want to try the 6kn8. As far as I can tell they were only Japanese made regardless of the branding. It has a gain of 45 so should work just fine. It’s an amazing tube and can be found at very reasonable prices.

Well the gain is very low relative to a 6SL7, and given the topology of the output stage, the amp requires a high gain input tube for any significant amount of power output. If using with insensitive headphones, they will be okay from a gain standpoint. The other concern is the core airgap of the anode chokes. It's 5mA. So assuming they bias at less than or equal to 5mA, they should be okay. Could perhaps go a little bit over, you just don't want the choke cores to saturate. But I'm not comfortable saying they are compatible and putting them on the sheet given the operation of the amp is significantly altered while using them.

 

[theveterans]

Huh, the 6cg7 is functionally the same as a 6sn7. You could put those into the 6sl7 slot and not need any adapters. Of course good versions of those are quite a bit more expensive. Thought @L0rdGwyn said the 6sn7 wasn’t compatible? I guess since you’re limiting the type of headphone it’s working ok for you.

Since you already have the adapters you might want to try the 6kn8. As far as I can tell they were only Japanese made regardless of the branding. It has a gain of 45 so should work just fine. It’s an amazing tube and can be found at very reasonable prices.

On the plate resistance, I don’t dare go lower than 6CG7 so to me anything between it and 12ax7 would be perfectly fine for Aegis (as long as heater current isn’t more than 6CG7)

I did try a couple of 6SN7 but it’s too linear for my taste. You should try 6CG7 and be prepared for some oh so vintagey sweet tone but without any muddiness or lacking clarity. Perfect balance of both for me

Well the gain is very low relative to a 6SL7, and given the topology of the output stage, the amp requires a high gain input tube for any significant amount of power output. If using with insensitive headphones, they will be okay from a gain standpoint. The other concern is the core airgap of the anode chokes. It's 5mA. So assuming they bias at less than or equal to 5mA, they should be okay. Could perhaps go a little bit over, you just don't want the choke cores to saturate. But I'm not comfortable saying they are compatible and putting them on the sheet given the operation of the amp is significantly altered while using them.

I haven’t seen any signs of any unusual distortions or unnatural sound that can point to anode choke saturation, but sonically, it’s excellent!

 

[SunRa Fan]

Acme KT88. So far, sounding as described previously. It's always nice to have a tube that takes better advantage of the Caldera's resolution.

 

[bajaed]

Acme KT88. So far, sounding as described previously. It's always nice to have a tube that takes better advantage of the Caldera's resolution.

I've had those in my Rogue Cronus Dark for about eight months and am very happy with them.

 

[SunRa Fan]

I've had those in my Rogue Cronus Dark for about eight months and am very happy with them.

I know they come with 24hrs of burn in already and mine sound quite clear. How long would you say yours took to burn in? For a premium tube that's been on the market for awhile there's surprisingly little info in the way of reviews out there. I actually learned more about them by searching this thread. Luckily, they're perpetually on sale and a good value.

 

[bajaed]

I know they come with 24hrs of burn in already and mine sound quite clear. How long would you say yours took to burn in? For a premium tube that's been on the market for awhile there's surprisingly little info in the way of reviews out there. I actually learned more about them by searching this thread. Luckily, they're perpetually on sale and a good value.

It's been awhile but I also remember them sounding quite good out of the box. I'd say 100 hours total should get you most of the way there.
I've always felt half of tube burn in involves them physically breaking in and half is our ears adjusting to the new sonic signature. The Acme KT-88 are a fantastic tube imo.

 

[Deleeh]

Do they sound more warm or more neutral?
Personal impressions would be great, because you can find almost nothing about them and read about their justification.
There must be a reason why PS Vane are sticking with them .

 

[SunRa Fan]

Do they sound more warm or more neutral?
Personal impressions would be great, because you can find almost nothing about them and read about their justification.
There must be a reason why PS Vane are sticking with them .

Right out of the box mine are on the warm side, but clear with very good detail retrieval. One more tube on a very short list of tubes that takes advantage of the Caldera. Competing well with the Ray KT88 selects(more or less the same price). I expect they'll clear up even more but I'm pretty happy with them so far. Last things last...they look pretty cool.

 

[idairyou]

Right out of the box mine are on the warm side, but clear with very good detail retrieval. One more tube on a very short list of tubes that takes advantage of the Caldera. Competing well with the Ray KT88 selects(more or less the same price). I expect they'll clear up even more but I'm pretty happy with them so far. Last things last...they look pretty cool.

Your description is close to my listening experience to the LinLai KT88D. Nuetral/warm with very good detail.

Considering the price of GEC NOS, PSVane and LinLai are very good alternatives.

Also friendlier to your pocketbook.

 

[SunRa Fan]

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.

 

[Isaacc7]

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?

 

[theveterans]

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?

It all boils down to they sound great with Aegis

KT88 and KT66 are my all-time fav tube sound followed with 6L6 and EL34

 

[Wes S]

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?

Grip and finesse at the same time, with effortless control.

 

[theveterans]

Grip and finesse at the same time, with effortless control.

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

 

[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.