[Deleeh]

@Toonartist Exactly, you describe it correctly.

However, I have two different amplifiers and when I swap the Kt88 tubes I strangely only notice small differences from the same tube.
Which are quite subtle.
It seems to me that the KT88 sounds the same and the subtle differences have other causes.
Certain things sound so different between the two amplifiers that there is a little more bass in amplifier A, and a little less bass in amplifier A, but more room.
The rest of the hardware is the same, i.e. dac, headphones, cables, etc...

Apart from the Ecc35, I've listened to it long enough and when you swap it over, you realise immediately where something has shifted or got better/worse.

 

[khaine1711]

For me, RCA 5691 and Tung-Sol 6SU7GTY are very close. Do you have the 5691 already? If so, I think you will find the 6SU7GTY is a lateral move. I personally prefer them over the Mullard ECC35 in Aegis, but I haven't compared in a while.

Yea I have the 5691. Like you said, I think it's more of a lateral move than an upgrade. I have tried around 6 7 types of 6SL7 and was surprised most of them sound really good, like there's subtle change in the tonal balance rather than clear technical upgrade between them.

The fomo is strong with this one ... "what if that one tube could bring something worth having to the table..."

When the differences are slight and subtle as you describe, how can you be sure there is even any difference at all? When it is considered that audio memory is extremely imprecise, and it must take at least a moderate amount of time to switch out tubes, wouldn't that introduce a fair amount of confound to the listening impression and comparison?

Changing only one type of tubes at a time (input/power/rectifier) and play with the combo for a few weeks, that's how I do it. Some changes like different power tube family, different rectifier type are pretty obvious; some ( different tube construction, tube age...) I'd admit could be my mind playing trick on me xD.

 

[L0rdGwyn]

Yea I have the 5691. Like you said, I think it's more of a lateral move than an upgrade. I have tried around 6 7 types of 6SL7 and was surprised most of them sound really good, like there's subtle change in the tonal balance rather than clear technical upgrade between them.

The fomo is strong with this one ... "what if that one tube could bring something worth having to the table..."

Changing only one type of tubes at a time (input/power/rectifier) and play with the combo for a few weeks, that's how I do it. Some changes like different power tube family, different rectifier type are pretty obvious; some ( different tube construction, tube age...) I'd admit could be my mind playing trick on me xD.

What's interesting about the 6SU7GTY is the sections were matched in factory, so the operating curves of the two sections overlay each other almost perfectly (I've confirmed this). That isn't hugely advantageous in Aegis, but definitely a mark of their quality. Yeah in Aegis differences in 6SL7 are going to be more subtle whereas changing output tube type will affect the sound more significantly due to differences in transconductance.

Edit: here are the curves. Also shows the excellent linearity of the 6SL7.

 

[jonathan c]

.... I am excited about Aegis .... already starting a collection of 6SL7, 6SU7, 6V6 ....

 

[Pharmaboy]

.... I am excited about Aegis .... already starting a collection of 6SL7, 6SU7, 6V6 ....

This amp is 100% worth the excitement IMO....

 

[L0rdGwyn]

.... I am excited about Aegis .... already starting a collection of 6SL7, 6SU7, 6V6 ....

So one note in regards to using 6V6 in Aegis - I had to choose a bias point to try and accommodate a range of output tubes. What that means is lower power tubes, like 6V6, are going to bias on the hotter side of their plate dissipation, whereas higher power tubes, like KT88, will bias on the colder side, i.e., nowhere near their maximum plate dissipation. Using a 5AR4 / GZ34 rectifier in Aegis, which is the lowest Vdrop rectifier out there, 6V6 is biasing pretty hot, right around its maximum plate dissipation. Now in a speaker power amplifier, that's a normal thing to do as you are trying to maximize power output. In a headphone amplifier, it isn't really necessary to push the tubes that hard. You can if you'd like, but it may shorten their usable life (although, I'm sure it will still be very long, especially if you are tube rolling). With all of that being said, for using 6V6, my recommendation would be to use a higher Vdrop rectifier to knock that bias point down a little bit, like a 5U4, 5R4, 5Y3, etc.

 

[khaine1711]

So one note in regards to using 6V6 in Aegis - I had to choose a bias point to try and accommodate a range of output tubes. What that means is lower power tubes, like 6V6, are going to bias on the hotter side of their plate dissipation, whereas higher power tubes, like KT88, will bias on the colder side, i.e., nowhere near their maximum plate dissipation. Using a 5AR4 / GZ34 rectifier in Aegis, which is the lowest Vdrop rectifier out there, 6V6 is biasing pretty hot, right around its maximum plate dissipation. Now in a speaker power amplifier, that's a normal thing to do as you are trying to maximize power output. In a headphone amplifier, it isn't really necessary to push the tubes that hard. You can if you'd like, but it may shorten their usable life (although, I'm sure it will still be very long, especially if you are tube rolling). With all of that being said, for using 6V6, my recommendation would be to use a higher Vdrop rectifier to knock that bias point down a little bit, like a 5U4, 5R4, 5Y3, etc.

I've been wanting to ask this for a while but I kinda just forgot ... Does lower/higher bias point change the sound of the tubes - or just the power output?

Like if one modifies the Aegis bias point to get near maximum plate dissipation for KT88, will the KT88 in that case sound better than the default Aegis' bias?

 

[jonathan c]

Thank you for the advice!

 

[L0rdGwyn]

I've been wanting to ask this for a while but I kinda just forgot ... Does lower/higher bias point change the sound of the tubes - or just the power output?

Like if one modifies the Aegis bias point to get near maximum plate dissipation for KT88, will the KT88 in that case sound better than the default Aegis' bias?

It depends. I would say small changes in bias point likely are not audible. Even moderate changes. Huge changes? Maybe you could hear that. Like say if you severely underbiased a KT88 at 20mA, then rebiased to 70mA, you would probably hear a difference. But in my experience, small changes aren't going to be heard. Changing the bias point will change the transconductance and plate resistance, so it will have some effect on output impedance.

I doubt they would sound better. And in Aegis, the bias current of the tubes isn't limited by the maximum dissipation of the tubes themselves, it is dictated by the core airgap in the output transformers, which is rated for maximum 60mA bias.

 

[zach915m]

For those hungry - or thirsty for more Aegis - here's the product page, I'll have the sale page up soon too but ofcourse won't be LIVE until; next friday.

One note - I haven't really tried the 12ax7 etc tube types, so can't speak to them, and I know there's a typo in the graphic that we will fix that says 12ATY on the product page. We will fix it too.

https://www.zmfheadphones.com/aegis-amp

Drink up! (I think this is Mike Tyson, but it might not be)

 

[zach915m]

Product page is up - https://shop.zmfheadphones.com/collections/amps-dacs/products/aegis-amplifier

Not sure who this guy is, but he's thirsty!

 

[Huntersknoll]

 

[Dexterama]

Are there stock available to ship at launch, or will there be an extended wait time?

 

[AnyDave]

Are there stock available to ship at launch, or will there be an extended wait time?

Our best estimate is that they will ship 1-3 weeks after launch for the first batch of units.

 

[Dexterama]

Wow, I love this picture from the product page. I could sit in this room all day.