[AnyDave]

I'm back on Aegis myself since my HY69 amp is in the shop. Listening with AC, Happy New Year!

I need to get a set of the redbase 6SL7s.

 

[L0rdGwyn]

Happy New Year! I should be building my aegis this coming weekend, unless something comes up. I also caved and ordered a bokeh, which I am sure will be a great pairing with it!

Nice, will be good to see your chassis with an amp in it!

I'm listening to Bokeh now, can confirm it sounds great. I like the hybrid pads.

I need to get a set of the redbase 6SL7s.

Yeah those are the RCA 5691, a ruggedized 6SL7. They sound great, and they look cool which is always a nice bonus.

 

[AnyDave]

Happy New Year! I should be building my aegis this coming weekend, unless something comes up. I also caved and ordered a bokeh, which I am sure will be a great pairing with it!

Yeah, it's a solid pairing indeed. I've been putting some Bokeh time with the Aegis.

 

[goldwerger]

I'm back on Aegis myself since my HY69 amp is in the shop. Listening with AC, Happy New Year!

How do those amps compare?

 

[L0rdGwyn]

How do those amps compare?

Well, I haven't done a head-to-head comparison and the HY69 amp is still a work in progress, but what I'd say is that it does what Aegis does, just more of it, meaning larger soundstage, higher degree of clarity.

It essentially takes the idea of Aegis (high gain input stage with cathode follower output stage biased by the output transformer primary DC resistance) to the extreme by using transformer coupling rather than choke loading the input stage, and uses a directly heated pentode as opposed to indirectly heated. BUT, to make that work means a much, much more temperamental circuit. It is much more susceptible to noise given the directly heated output tube (a problem I have now solved), and a high gain input stage capable of transformer coupling means a very high transconductance tube in the D3a. D3a and its high gm counterparts are notorious for parasitic oscillation. These are wide bandwidth tubes that are prone to picking up radio frequency noise, leading to high frequency oscillations that can bleed into the audio band. Very careful measures must be taken for these tubes such that they do not oscillate. Even if the amp sounds good and no obvious signs of oscillation can be heard does not mean it is not happening, it can be measured, so I am battling that now

So, yes the HY69 amp is a evolution of Aegis topology, but I have to pay the price of a very tricky circuit, not to mention something like this commercially would likely cost >$20K. Whereas Aegis sounds great, is affordable, is very stable and works on the first go! HY69 amp is the very end of the diminishing returns curve for single-ended tube amps.

 

[goldwerger]

Well, I haven't done a head-to-head comparison and the HY69 amp is still a work in progress, but what I'd say is that it does what Aegis does, just more of it, meaning larger soundstage, higher degree of clarity.

It essentially takes the idea of Aegis (high gain input stage with cathode follower output stage biased by the output transformer primary DC resistance) to the extreme by using transformer coupling rather than choke loading the input stage, and uses a directly heated pentode as opposed to indirectly heated. BUT, to make that work means a much, much more temperamental circuit. It is much more susceptible to noise given the directly heated output tube (a problem I have now solved), and a high gain input stage capable of transformer coupling means a very high transconductance tube in the D3a. D3a and its high gm counterparts are notorious for parasitic oscillation. These are wide bandwidth tubes that are prone to picking up radio frequency noise, leading to high frequency oscillations that can bleed into the audio band. Very careful measures must be taken for these tubes such that they do not oscillate. Even if the amp sounds good and no obvious signs of oscillation can be heard does not mean it is not happening, it can be measured, so I am battling that now

So, yes the HY69 amp is a evolution of Aegis topology, but I have to pay the price of a very tricky circuit, not to mention something like this commercially would likely cost >$20K. Whereas Aegis sounds great, is affordable, is very stable and works on the first go! HY69 amp is the very end of the diminishing returns curve for single-ended tube amps.

Sounds pretty exciting, and definitely for the most committed… I’m sure once you finished tweaking it, it would be worth the effort.

Very very interesting!!!

 

[mattiastomas]

Yeah, it's a solid pairing indeed. I've been putting some Bokeh time with the Aegis.

It’s crazy how good the Bokeh sounds with the Aegis!

Really glad I built the Aegis. It’s sounded amazing with anything I’ve connected to it. Really an endgame tube amp for you. Only itch I get now is tube rolling

 

[AnyDave]

It’s crazy how good the Bokeh sounds with the Aegis!

Really glad I built the Aegis. It’s sounded amazing with anything I’ve connected to it. Really an endgame tube amp for you. Only itch I get now is tube rolling

It is indeed a stellar design. I'm also quite pleased with the build.

 

[Toonartist]

For me the Aegis is what I'm building my system round. I love it for both the Elite and the AC. The AC just sounds so open with it it's hard to believe at times it's a closed back!

This and the pride and fun derived from building it means its a forever amp for me

 

[khaine1711]

For me the Aegis is what I'm building my system round. I love it for both the Elite and the AC. The AC just sounds so open with it it's hard to believe at times it's a closed back!

This and the pride and fun derived from building it means its a forever amp for me

I saw you have both the Mullard EL34 xf2 and the El38, how do they compare?

The reason I'm asking is the stock on El38 atm is ... varied to say the least. Lots of variations on construction (trough/halo/2x halo/rectangular getter) and most sellers now offer single tube only (others offer matched quad - and we only need 2). To use in pair I should at least get two that looks the same/has the same construction right?

Meanwhile I could easily source a pair of el34 xf2.

 

[Toonartist]

I saw you have both the Mullard EL34 xf2 and the El38, how do they compare?

The reason I'm asking is the stock on El38 atm is ... varied to say the least. Lots of variations on construction (trough/halo/2x halo/rectangular getter) and most sellers now offer single tube only (others offer matched quad - and we only need 2). To use in pair I should at least get two that looks the same/has the same construction right?

Meanwhile I could easily source a pair of el34 xf2.

It's been a while since I listened to the XF2's on the Aegis. I seem to recall I favoured the EL37's (another really good tube) when I compared them to the EL34's when I first built the amp. I'll need to revisit them to see how they compare.

What I would say, if you're buying NOS tubes, is not to worry too much about buying singles. I've done this a couple of times.

What I've found is the Trough getter EL38's seem to be earlier versions with a slightly different process to create the getter flash. The ones I have both have dark, near black, getter flashes when viewing from the outside and are from the early 1950's (bought from different sellers). These pre 1955 tubes have an EL38 tube code of 1326 before the date code. The double halo versions have a bright silver getter flash and were made in the 1960's and have the HM1 tube code. I googled the thing about the dark, near black getter flashes on new tubes and apparently it's normal and is the result of a different process used to create it. I haven't had a chance to run in the trough getters in order to compare the sound but the 3hrs testing didn't make me think there was going to be a big difference.

After receiving advice here about buying matched pairs and being told not to worry too much (for the Aegis anyway), I tend to buy singles provided they've been tested, and I just try to get a reasonably close match. If you use the search on this thread you should find tube matching has cropped up a couple of times.

 

[khaine1711]

Yea I'm not worrying much about matched pair. Still, many of the EL38 sellers now (especially in the UK) sell singles in large quantity - something I am pondering about ... Lot of 4 is cheap but what if you get 4 tubes with 4 different types of getters lol.

Sadly with the lunar new year coming up, I am reluctant to ship anything ... hopefully those listings that specify getter types/tube codes is still there one or two months later.

Have you tried any EL38M? - they seems to be EL38 with the same appearance as the EL39 Radio Technique - still I cant find any info on them being EL38 equivalent or not.

El37 are quite expensive now, I got quoted 330 bucks for a local pair... also some comments earlier on this thread about many of them being noisy so I decided not to order any adapters for them (yet).

 

[Toonartist]

No, I've never tried the EL38m... In terms of noise, I've never had any issues with the EL37's though.

 

[AnyDave]

It's been a while since I listened to the XF2's on the Aegis. I seem to recall I favoured the EL37's (another really good tube) when I compared them to the EL34's when I first built the amp. I'll need to revisit them to see how they compare.

What I would say, if you're buying NOS tubes, is not to worry too much about buying singles. I've done this a couple of times.

What I've found is the Trough getter EL38's seem to be earlier versions with a slightly different process to create the getter flash. The ones I have both have dark, near black, getter flashes when viewing from the outside and are from the early 1950's (bought from different sellers). These pre 1955 tubes have an EL38 tube code of 1326 before the date code. The double halo versions have a bright silver getter flash and were made in the 1960's and have the HM1 tube code. I googled the thing about the dark, near black getter flashes on new tubes and apparently it's normal and is the result of a different process used to create it. I haven't had a chance to run in the trough getters in order to compare the sound but the 3hrs testing didn't make me think there was going to be a big difference.

After receiving advice here about buying matched pairs and being told not to worry too much (for the Aegis anyway), I tend to buy singles provided they've been tested, and I just try to get a reasonably close match. If you use the search on this thread you should find tube matching has cropped up a couple of times.

I found a pair of XF4s when going through my tube stash the other day. They aren't matched well enough to be used in my vintage Marshall guitar amps, so they weren't installed anywhere. I know they aren't as desirable as the XF2, but I'm going to throw them in the Aegis and see how they sound.

 

[Toonartist]

I found a pair of XF4s when going through my tube stash the other day. They aren't matched well enough to be used in my vintage Marshall guitar amps, so they weren't installed anywhere. I know they aren't as desirable as the XF2, but I'm going to throw them in the Aegis and see how they sound.

I'd imagine they should sound great.... I mean, do Mullard make duff tubes?

I often forget about the XF2s as they're in the Auris Nirvana and that amp hasn't had much play time since the Aegis was built. I still like it... I just find the Aegis is more to my preference and, it's a lot more versatile. It takes so many different tubes that change the way it sounds. The Nirvana is restricted to EL34's and using the 12au7's as a way to change how it sounds. The changes are not as dramatic as changing power tubes in the Aegis.

The time may come when I have to decide whether to keep it or use it to invest in a good transport into the VEGA G2.2 DAC. We'll see how things pan out over the year!