Looking for a tube compatibility list for the Aegis. I feel like I saw one at some point, but now I've lost it. Anyone have one handy in their clipboard?
ZMF Aegis Official Thread
- Thread starter AnyDave
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Rectifer - 5V and up to 3A, includes 5U4, 5R4, 5V4 / GZ32, 5AR4 / GZ34, 5Y3 (best to use lower power output tubes) and many, many more.
Inputs - 6SL7 and all of its variants
Outputs - almost any power pentode: EL33, EL34, EL37, EL38 (w/ adapter), KT66, KT77, KT88, KT90, 6550, 6V6, 6L6, EL84 (w/ adapter)...lots more.
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A lifetime worth of tube rolling options right there. It's honestly a bit overwhelming trying to figure out where I should start. . .Don't get me wrong though, as having that many options is a good thing in my opinion.
Pharmaboy
Headphoneus Supremus
I'm desperately trying not to think about how all these tube variants might boost the already amazing sound of this amp....
Toonartist
Formerly known as dAndis67
lol… yeah. I’m now at the point now I only add something new once in a while otherwise I could be left spinning at the variety of options… it’s insane in a beautiful way!
New tubes receive a min of 60hrs before they’re allowed to be removed… that’s my first rule of Aegis Club
Toonartist
Formerly known as dAndis67
while the stock tubes are good… there are plenty of tubes out there that will just make your jaw drop. I love this amp so much!!!
There are lot of obscure pentodes out there. Like I've said on the DIY Aegis thread, if you haven't seen someone else try a new tube, best to ask and I'll look at the operating curves. That's assuming there are triode curves available, not always the case with weird tubes. If you have a curve tracer though, that isn't a problem 
Deleeh
Headphoneus Supremus
Hello,
is it possible to use other driver tubes than 6SL7 in the DIY and Zmf Aegis version which would work with adapters like 12AU7/12AT7 or maybe 12AX7?
I'm asking because if so, depending on which output tube is in there, these things could give a kick in terms of Mu gain and maybe work better overall.strong output tube like EL84 with a 12AU7 could sometimes work wonders in terms of sound,even though a 12AT7 or 6SL7 can be better, it can have too much drive.
In most modern tube amps I see little variety in the fact that the Mu factor is variable and usually already fixed, the Cayin HA3 A is a good example, which hardly allows tubes of other types.
And is indirectly a lazy sack, although it could perhaps be better.
is it possible to use other driver tubes than 6SL7 in the DIY and Zmf Aegis version which would work with adapters like 12AU7/12AT7 or maybe 12AX7?
I'm asking because if so, depending on which output tube is in there, these things could give a kick in terms of Mu gain and maybe work better overall.strong output tube like EL84 with a 12AU7 could sometimes work wonders in terms of sound,even though a 12AT7 or 6SL7 can be better, it can have too much drive.
In most modern tube amps I see little variety in the fact that the Mu factor is variable and usually already fixed, the Cayin HA3 A is a good example, which hardly allows tubes of other types.
And is indirectly a lazy sack, although it could perhaps be better.
Tubes that could be adapted as inputs are 12AT7, 12AY7, and 12AX7. I believe they have been used in the DIY version, not in the ZMF version, I cannot speak to how they sound in Aegis, but all of those tubes though are far less linear than a 6SL7. Only 12AX7 has higher mu than 6SL7. Sorry, but I'm not sure what you mean when you say too much drive or variable mu factor (amplifier gain?), if you explain a little more I can try to clarify.
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Deleeh
Headphoneus Supremus
Okay,
what I mean by that and I'll use my amplifier as an example.
It's very versatile in terms of tubes and uses the spectrum of the Aegis.
A combination of EL84 with 12Au7 sounds quite good in itself, you have a lot of headroom at the potentiometer, but the air goes out quickly.
A 12AT7, on the other hand, is a little better, you have more meat in general, but a little less headroom at the potentiometer.
Instead of 12 o'clock, the 10 o'clock position is enough for a decent volume.
If I now use a 12AX7 with an EL84, the drive, which overlaps quite quickly, is loud and sometimes tiring,
all in all over-promoted.
Definitely too much Mu amplification in the combination, 12Au/AT7 are more suitable, even 6SN7 and 6SL7.
But as I said, I'm only talking about my amplifier.
I believe or think that it could work similarly in the Aegis, but I'm not sure.
Hence the question with a little more choice on the driver tube.
If even 6SN7 can be used as a driver tube, it can work very well and sound good depending on the strength of the output tubes.
what I mean by that and I'll use my amplifier as an example.
It's very versatile in terms of tubes and uses the spectrum of the Aegis.
A combination of EL84 with 12Au7 sounds quite good in itself, you have a lot of headroom at the potentiometer, but the air goes out quickly.
A 12AT7, on the other hand, is a little better, you have more meat in general, but a little less headroom at the potentiometer.
Instead of 12 o'clock, the 10 o'clock position is enough for a decent volume.
If I now use a 12AX7 with an EL84, the drive, which overlaps quite quickly, is loud and sometimes tiring,
all in all over-promoted.
Definitely too much Mu amplification in the combination, 12Au/AT7 are more suitable, even 6SN7 and 6SL7.
But as I said, I'm only talking about my amplifier.
I believe or think that it could work similarly in the Aegis, but I'm not sure.
Hence the question with a little more choice on the driver tube.
If even 6SN7 can be used as a driver tube, it can work very well and sound good depending on the strength of the output tubes.
So one thing about Aegis that is different than other amplifiers that use pentode outputs (and I explain this a little more in an upcoming interview I did with Zach on the YooToob) is that it uses an unusual output stage, a transformer coupled cathode follower. This, to my knowledge, is the first commercial headphone amp to use this topology, so it is going to throw people through a loop who are used to owning conventional two-stage SET amplifiers, and I will try to explain.
When a tube is wired as a cathode follower (which is much more common in OTL output stages), it has no voltage gain. So essentially the overall gain of the amplifier (i.e., where in the volume dial you reach appropriate listening volume with a given headphone) is going to be unchanged no matter what output tube is being used, they all operate at a voltage gain a little less than 1. Another advantage of this output topology is there are no signal capacitors in the output stage, it is just a tube and a transformer, that's it.
As such, all of the voltage gain in the amplifier is coming from the input stage, instead of both stages in a conventional SET design. The consequence of this is that the input stage must use a high gain tube as it is responsible for all voltage gain, that is why the 6SL7 has been chosen. It is loaded by a choke, which allows its AC voltage swing higher than the B+ / operating plate voltage. This allows the 6SL7 to swing very high AC signals. The combination of the 6SL7 and a cathode follower output gives a good amount of play in the volume dial; I don't think you will find that it gets overly loud very quickly. If a lower gain tube is used in Aegis (e.g., 12AT7, 12AY7), gain will be lessened and a higher turn in the potentiometer is needed to reach listening volume. Peak power output of the amplifier will also be less. And as I mentioned, these tubes are less linear than 6SL7, so likely higher distortion as well.
A cathode follower is also a buffer, meaning it has very low input capacitance and very high input impedance, making it a very easy load for the input tube. 6SL7 is a wimpy driver tube, meaning it cannot supply very much output current to drive high input capacitances / low input impedances. It very much benefits sonically from working into a buffer circuit, like a cathode follower.
All of this is to say 6SL7 was chosen very specifically for design reasons, and this is why there is not a lot of variability in terms of input tube rolling. But because it is the optimal input tube for this design, I think most will find it performs better than other inputs that can be adapted and tube rolling output tubes will have much more drastic sonic changes.
I hope that answers your question!
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You and me both!
6SL7 is a great tube. Some of my favorites
The legendary RCA 5691
Brimar CV1985
Mullard ECC35
Ken Rad silver plates from the 1950's
Tung-Sol short bottle from the 1950's
These are all available. The RCAs, Brimars and the Mullards have gotten pricey. But the Kentucky Radios and the Tung-Sols are more reasonable.
The legendary RCA 5691
Brimar CV1985
Mullard ECC35
Ken Rad silver plates from the 1950's
Tung-Sol short bottle from the 1950's
These are all available. The RCAs, Brimars and the Mullards have gotten pricey. But the Kentucky Radios and the Tung-Sols are more reasonable.
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Deleeh
Headphoneus Supremus
This is very well explained by you from a technical point of view, thank you,
.You have now explained technically that a less powerful driver tube has an effect on the overall performance and things like that.
That's okay, question to you from a practical point of view:
Assuming the Aegis runs with a 6SN7/6SL7 to 12xx7 adapter and we use an EL84 or EL34 would your subjective impression be that it sounds just as good,even though there is less power?
We know that power is not always everything and often there are headphones that don't need much.
Zmf headphones are relatively easy to drive, but it is always better if there are still reserves.
But at 2 watts from the standard setup, roughly estimated at 1.5 watts, that would still be very decent if you were to use a 12at7/au7 tube.
Or is it more about achieving the general efficiency of the driver tube?
This is very well explained by you from a technical point of view, thank you,
You have now explained technically that a less powerful driver tube has an effect on the overall performance and things like that.
That's okay, question to you from a practical point of view:
Assuming the Aegis runs with a 6SN7/6SL7 to 12xx7 adapter and we use an EL84 or EL34 would your subjective impression be that it sounds just as good,even though there is less power?
We know that power is not always everything and often there are headphones that don't need much.
Zmf headphones are relatively easy to drive, but it is always better if there are still reserves.
But at 2 watts from the standard setup, roughly estimated at 1.5 watts, that would still be very decent if you were to use a 12at7/au7 tube.
Or is it more about achieving the general efficiency of the driver tube?
It isn't so much a question of driver tubes being more or less powerful, it's a question of driver tube linearity and gain, both of which are better optimized using 6SL7 in this circuit over 12AT7, 12AY7.
I have not used 12AT7 or 12AY7 adapted into Aegis, I believe 1-2 people have tried it in the DIY version. But again, these tubes are likely to generate higher distortion than 6SL7, I would expect the subjective performance to be worse, but still sound good. I cannot say for certain, opinions would vary I'm sure.
Power output would still be sufficient for easy to drive headphones like ZMFs, but likely not enough for the more demanding planars like a Tungsten or Susvara.
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