[Pharmaboy]

Matt, one option for a more “budget” OTL could be a pre-owned Woo Audio WA2 and getting top-shelf tubes for it.

The WA2 scales REALLY well with better tubes and sounds wonderful with ZMF DD headphones.

It would cost you about $1800-2000 to do that, with the option to upgrade the fuse and power cable if that’s something you’d want to do later.

Not cheap per se, but a bit less that the DecWare, and with excellent quality and results sonically.

I would also give a shout-out for one of the great sonic overachievers, the humble Woo WA3. It's compact, has just 3 tubes (2 input tubes and 1 power tubes), and on paper has a modest power output. But IRL use, the WA3 has way more than enough power for anything I try with it.

With the right tubes (in my case, a pair of Brimar CV455s* on adapters + a Tung Sol 5998 for power), you get a very healthy dose of OTL magic with ZMF high impedance dynamics.

* @jonathan c turned me on to these--really special tubes

 

[ckhirnigs113]

Here's a scary thought--I have yet to hear the CC on the Aegis. That'll be another level of amazing.

I’m really interested to hear how you think the Aegis compares to your beloved HP8. I was very close to buying an HP8 after selling my Quicksilver, but ended up sticking to solid state for a while (Mjolnir 3). Now the much more expensive Aegis is what I’m tempted by, so be sure to let us know how the HP8 stacks up against the Aegis with all the ZMFs you have on hand.

 

[Pharmaboy]

I’m really interested to hear how you think the Aegis compares to your beloved HP8. I was very close to buying an HP8 after selling my Quicksilver, but ended up sticking to solid state for a while (Mjolnir 3). Now the much more expensive Aegis is what I’m tempted by, so be sure to let us know how the HP8 stacks up with all your ZMFs you have on hand.

The HP8 can't best the Aegis, a true endgame amp, but it comes surprisingly close in SQ.

I compared the HP8 head-to-head w/the Aegis in my review of the Aegis. I expected the Aegis to walk all over the HP8, but it didn't play out that way. I'm listening to the HP8 right now. I just love this amp.

 

[robo24]

Spent today with the Caldera Open on the Mojo 2 and am pleasantly surprised. I've never found Chord DACs when used as amps for higher impedence dynamics especially good but apparently it has some current doubling technology for lower impedence headphones like planars. Got the Mojo 2 for the DCA Stealth based on that and some specific recommendations and used the built-in EQ to boost the sub-bass and bass for the Stealth to warm it up a little. So that's how it was set, though the Caldera doesn't need that. However those settings are also really nice on the Caldera! Quite enjoyable and shows the Caldera doesn't need a megabucks setup to sound fantastic.

 

[LongSong]

exactly right IMO

I don't think you thought this through to a proper conclusion. Just one solid state amp???

 

[Toonartist]

Thanks for the suggestion! The WA2 definitely is on the list to consider.

Might try more tube rolling on the Aegis first to see. Seems the most economical

Very true... also, don't forget that the DAC has a big influence on stage and imaging. And, as with most DACs, they're also very sensitive to mains noise and you can boost the performance of an DAC by providing it with a good clean power supply.

The Auralic VEGA G2.2 I have has amazing shielding, double cased etc with a separate internal copper chassis. The only way in for noise was via the power supply. When I added a good quality power block and conditioner, bass, micro detail and noise floor all improved and as a result, so was the imaging. I was surprised the difference when moving it from an unfiltered socket on the block to one that was filtered. Initially it felt like some detail was lost but after a while I realised it was still there it was just the false detail that had been removed and what was left was a smoother more liquid sound. Removing it altogether after a couple of weeks and the sound felt edgy, harsher so the conditioner was replaced straight away.

You have to remember in most households we have so many bits of gear (smart this and that) that aren't as careful with noise control as our HiFi gear and that noise is pumped back into our mains system (AC) and straight up the cable to your DAC. It's not about the electricity company supplying clean electricity to your house, it's about the noise our equipment adds to that supply once it reaches us which then flows around the ring mains.

Just a thought though... clean power is very important and something that the 2 channel community, more than the headphones community, focuses on greatly as it really helps to reveal what your existing gear can really do.

 

[cats4cans]

It’s a tough job that might take weeks, but someone’s gotta do it because these tubes aren’t going to test themselves. I just need to triple check the 6/12 volt dip switch is in the correct position before power up. No one likes to see NOS tubes go poof before even getting a listen.

 

[AnyDave]

I would also give a shout-out for one of the great sonic overachievers, the humble Woo WA3. It's compact, has just 3 tubes (2 input tubes and 1 power tubes), and on paper has a modest power output. But IRL use, the WA3 has way more than enough power for anything I try with it.

With the right tubes (in my case, a pair of Brimar CV455s* on adapters + a Tung Sol 5998 for power), you get a very healthy dose of OTL magic with ZMF high impedance dynamics.

* @jonathan c turned me on to these--really special tubes

I'm going to snag a WA3 at some point. I want to have one of those in my collection.

 

[L0rdGwyn]

Got a four day weekend off, doing some listening with my beloved Atrium Open this morning. With my chassis maker on hiatus and the Aegis project(s) done, first time in a while I'm not actively working on an amplifier (although, I really want to be). Trying to use the time to get back in touch with just listening for enjoyment. When I'm working on amps, it's easy to fall into a habit of every listening session being an evaluation! So I'm listening to one that doesn't need to be evaluated, it's done done and old news. I've shown it here a few times before, but my OTL is like a super Airmid, a pretty extreme take on the direct-coupled cathode follower OTL, uses either two 6336 outputs or the higher transconductance 6528 outputs. Bias current for each output tube is 275-300mA, which in tube terms, is a lot. Gets the output impedance down to around 20ohms for the 6336 and 11ohms for the 6528. The output stage is actively loaded with FETs in series with some high power resistors for biasing purposes. Those are both mounted to the giant heat sinks on the side panel as otherwise they would get wicked hot and go kaput.

With Atrium, it probably has the highest degree clarity of any amplifier I've made. I think these types of OTLs are great for that. Compared to transformer coupled circuits (mine at least), it doesn't quite have the same degree of "body" and "heft", but the clarity and airiness are pretty stunning, especially for acoustic music.

I've got some new Aegis tubes coming into over the next couple days, going to be fun trying those out too.

 

[George Hincapie]

It’s a tough job that might take weeks, but someone’s gotta do it because these tubes aren’t going to test themselves. I just need to triple check the 6/12 volt dip switch is in the correct position before power up. No one likes to see NOS tubes go poof before even getting a listen.

I did exactly that with a new pair of matched Melz. On the MZ3 as well. I'm still traumatised!

 

[AnyDave]

Got a four day weekend off, doing some listening with my beloved Atrium Open this morning. With my chassis maker on hiatus and the Aegis project(s) done, first time in a while I'm not actively working on an amplifier (although, I really want to be). Trying to use the time to get back in touch with just listening for enjoyment. When I'm working on amps, it's easy to fall into a habit of every listening session being an evaluation! So I'm listening to one that doesn't need to be evaluated, it's done done and old news. I've shown it here a few times before, but my OTL is like a super Airmid, a pretty extreme take on the direct-coupled cathode follower OTL, uses either two 6336 outputs or the higher transconductance 6528 outputs. Bias current for each output tube is 275-300mA, which in tube terms, is a lot. Gets the output impedance down to around 20ohms for the 6336 and 11ohms for the 6528. The output stage is actively loaded with FETs in series with some high power resistors for biasing purposes. Those are both mounted to the giant heat sinks on the side panel as otherwise they would get wicked hot and go kaput.

With Atrium, it probably has the highest degree clarity of any amplifier I've made. I think these types of OTLs are great for that. Compared to transformer coupled circuits (mine at least), it doesn't quite have the same degree of "body" and "heft", but the clarity and airiness are pretty stunning, especially for acoustic music.

I've got some new Aegis tubes coming into over the next couple days, going to be fun trying those out too.

That's a sharp looking amp.

 

[L0rdGwyn]

That's a sharp looking amp.

So sharp in fact, bodily dismemberment is a real risk when transporting it.

 

[AnyDave]

So sharp in fact, bodily dismemberment is a real risk when transporting it.

Yeah, if you're around hi-fi long enough, you're bound to have some heat sink scars.

 

[cats4cans]

I did exactly that with a new pair of matched Melz. On the MZ3 as well. I'm still traumatised!

That’s simply awful. And I desperately want to avoid a similar event. I typically shy away from the unobtanium end of the pool. I’ve been collecting early RCA 12SN7GT since I got the MZ3. They’re not too pricey yet. Given the expected life, I think I’ll be dead before I manage to use them all. But I finally decided to pony up for a few 6SN7 pairs that I’ll hopefully use in an HP8 someday. Still less than a new pair of top tier Linlai or Psvane, but I’m being very careful.

 

[Toonartist]

Talking of tube destruction ... I was removing a RCA Red Base 5691 the other day. I watched in slow motion as it pinged out of my fingers and landed on the laminate floor My heart sank.

I picked it up and checked it over... tentatively popped it back in and powered up. To my amazement it worked and sounds as it did before. They must be built like tanks. It fell about 3 foot onto the wood floor