[Varejao17]

Can you/would you be able to describe the difference between the two?

$4900 - $799 = $4101.

 

[Mikem53]

Can you/would you be able to describe the difference between the two?

I can try ... I’ve had it for a few months now.. My previous class A amp was the BAT VK75SE Which I owned for several years. A modern tube amp that’s not thick or syrupy like some vintage tube amps tend to be.. but always Issues with output tubes going out of bias, blowing fuses, the heat.. etc.. so I decided to move on from tube amplifiers and find something that sounded similar to tubes without the downfalls of power tubes.
The schiit Aegir with their continuity topology claiming class A sound was Too good to pass up.. and it did live up to their claims... But I was still not hearing vocals That sounded life like natural and always a bit recessed compared to other foreground sounds ? The Aegir played loud at low volumes but not all the sounds seemed balanced.. excuse my lack of audiophile terms.. Bass was well defined, some might think it’s loose or wooly, but I prefer natural bass to bass slam or tight boom.. the Aegir had plenty of detail too... or so I thought until I compared it to the Pass..
Everything is Better with the Pass.. I never had an amplifier that made such a Huge difference in sound.. I mean it’s crazy detailed.. everything comes thru.. it’s not distracting like some SS amps can be.. Vocals, Which are very important to me, come through so natural and clean and lifelike.. the soundstage is so solid, so well laid out.. Everything is more Real.. Pianos sound like the percussion instruments they are.. You can hear and feel the hammers striking the strings.. it’s so precise and REAL.. I’ve been avoiding writing a review about the amp because I am so in love with it and I find it so amazing, I figured I would just be labeled a fan boy and mostly ignored.. but even though the XA25 is 5 times the price of an Aegir.. it’s a bargain at that price..
The output devices On the XA25 Are directly connected to the speakers. it’s a different design Compared to the other class a amps pass builds..
As well as the output devices themselves.. While the amp is only rated it 25 W per channel, it will do 50 W per channel in class A, And a whopping 80 W per channel wide-open at the low distortion rated spec. It gets as hot as a tube amp, its heavy and expensive... but its so very good... Every time I sit and listen, I get so much enjoyment from the system the amp pays for itself each time I sit and Listen... highly recommend!

 

[Balthazar B]

Can you/would you be able to describe the difference between the two?

If you're handy with a soldering iron, you can build a pair of Nelson Pass-designed ACA monoblocks for the price of an Aegir, that should work quite well with very efficient speakers like Mikem53's Athenas. While they are likely not going to be as sublime as an XA25, people seem to love them.

https://diyaudiostore.com/products/amp-camp-amp-kit?variant=7072933085218

There's a very active forum on these amps, including tips on upgrading a couple of components relatively cheaply to noticeably improve their performance. They should pair very nicely with a Freya+ upstream...

 

[artur9]

$4900 - $799 = $4101.

Um. I meant sonically

 

[artur9]

If you're handy with a soldering iron, you can build a pair of Nelson Pass-designed ACA monoblocks for the price of an Aegir,

I injure myself with a letter opener. The ACA stuff does look like fun.

 

[Mikem53]

I built the Pass ACA 1.8 Class A amp about a month ago.. Was a great experience and enjoyed the challenge.. I wasn’t expecting to be so Good !!
Nelson Pass used some of his private stash of vFET transistors in this kit.. It was able to power my main system... but not enough oomph to drive it
properly... So I set it up in my office .. Macbook pro > Modi Multibit > Magni as preamp > ACA amp > NHT Super ones .. Great sound.. Very quiet background, plenty of volume and bass !! Using one ACA in stereo mode is more than you would expect.. I hooked them up to the NHT, 86 db sensitive and wasn’t expecting it to even work... Yet it sounds glorious and plays louder than I will ever require of it !!

 

[Mikem53]

If you're handy with a soldering iron, you can build a pair of Nelson Pass-designed ACA monoblocks for the price of an Aegir, that should work quite well with very efficient speakers like Mikem53's Athenas. While they are likely not going to be as sublime as an XA25, people seem to love them.

https://diyaudiostore.com/products/amp-camp-amp-kit?variant=7072933085218

There's a very active forum on these amps, including tips on upgrading a couple of components relatively cheaply to noticeably improve their performance. They should pair very nicely with a Freya+ upstream...

The ACA did drive my speakers... but didn’t Compare to the XA25 in dynamics, tonal balance, etc.. the ACA did Better with a 2 way monitor speaker, less crossover to deal with..

 

[Mikem53]

Since the Pass ACA amp was brought up, I thought I would add a quick summary from my build experience and forums, research..
the good:
quality parts and circuit card.. not only designed well, but traced on both sides with copper barrels for connection points on a sturdy board.. this is useful for those who don’t solder often, like me.. sturdy thick , etc..
you can supply your own case, PS, parts, etc.. the case in the kit is very high quality, pre drilled for main card heatsink.
Optional switch on rear to wire amp for stereo, mono parallel or Bridged operation. I chose to do this and it’s simple to do..
great Class A sound.. only 2 stages.. no frills, very clean Sounding, quiet background. 8wpc with the 24v 120w power supply.
amp distorts with even order harmonics, like tubes.. never a sharp edge.. very Musical..

the bad:
only 8wpc, not for everyone
since the kit is made for all audiences, the PS is external, 24v for safety. It comes with a meanwell regulated switching PS. Works fine and measures stable.. but I’m going to build a linear PS with more cap storage, more available current..
Have to solder !!! I watched Mr. Carson’s lab, how to solder YouTube video to sharpen my skills.. it took me a week to build only because I didn’t want to screw it up.. Can be done in a few evenings w a bit of soldering experience..
The case was difficult to align because there are so many connection points that need to come together aligned.. but once setup, it’s very sturdy and nice looking and gets quite warm in operation, I measured 122F on the center of the heatsink.. but it’s small in stature, so it’s not a heater..

Summary:
I have the ACA amp hooked up to a pair of NHT super ones. Rated at 86db sensitivity with a sealed, non ported enclosure.. that makes it harder to drive.. I hooked it up as an afterthought thinking it wouldn’t even work.. Yet it can be heard loud and clear in other rooms in the house when I crank it up..
I measured the amp current draw and it showed 81 watts, So that’s quite a bit of heat going up with only 16 watts being used for sound.. that’s the price you pay for that Class A sound.. a worthy trade off..
I don’t like switching power supplies as they tend to be noisy, but I don’t hear any “noise” with this particular model. I am still going to put together my own power supply possibly in a matching case.
I built Heathkit electronics years ago and this kit is the best I’ve ever put together as far as quality and the final product itself. If you’re looking for an amp to power some efficient speakers or even inefficient speakers with a reasonable sound level and you like to tinker with electronics.. then this kit is for you. If nothing else, it shows you how important the first few watts really are, and what a properly designed low power amp can do..

 

[Balthazar B]

Since the Pass ACA amp was brought up, I thought I would add a quick summary from my build experience and forums, research..
the good:
quality parts and circuit card.. not only designed well, but traced on both sides with copper barrels for connection points on a sturdy board.. this is useful for those who don’t solder often, like me.. sturdy thick , etc..
you can supply your own case, PS, parts, etc.. the case in the kit is very high quality, pre drilled for main card heatsink.
Optional switch on rear to wire amp for stereo, mono parallel or Bridged operation. I chose to do this and it’s simple to do..
great Class A sound.. only 2 stages.. no frills, very clean Sounding, quiet background. 8wpc with the 24v 120w power supply.
amp distorts with even order harmonics, like tubes.. never a sharp edge.. very Musical..

the bad:
only 8wpc, not for everyone
since the kit is made for all audiences, the PS is external, 24v for safety. It comes with a meanwell regulated switching PS. Works fine and measures stable.. but I’m going to build a linear PS with more cap storage, more available current..
Have to solder !!! I watched Mr. Carson’s lab, how to solder YouTube video to sharpen my skills.. it took me a week to build only because I didn’t want to screw it up.. Can be done in a few evenings w a bit of soldering experience..
The case was difficult to align because there are so many connection points that need to come together aligned.. but once setup, it’s very sturdy and nice looking and gets quite warm in operation, I measured 122F on the center of the heatsink.. but it’s small in stature, so it’s not a heater..

Summary:
I have the ACA amp hooked up to a pair of NHT super ones. Rated at 86db sensitivity with a sealed, non ported enclosure.. that makes it harder to drive.. I hooked it up as an afterthought thinking it wouldn’t even work.. Yet it can be heard loud and clear in other rooms in the house when I crank it up..
I measured the amp current draw and it showed 81 watts, So that’s quite a bit of heat going up with only 16 watts being used for sound.. that’s the price you pay for that Class A sound.. a worthy trade off..
I don’t like switching power supplies as they tend to be noisy, but I don’t hear any “noise” with this particular model. I am still going to put together my own power supply possibly in a matching case.
I built Heathkit electronics years ago and this kit is the best I’ve ever put together as far as quality and the final product itself. If you’re looking for an amp to power some efficient speakers or even inefficient speakers with a reasonable sound level and you like to tinker with electronics.. then this kit is for you. If nothing else, it shows you how important the first few watts really are, and what a properly designed low power amp can do..

Thanks for the summary, Mike! One other item of note: whatshisface over at Audio Science Review hates the ACA because it doesn't measure well and won't drive his 85 db speakers. Will leave it to y'all to decide whether his opinion should be included in the good or in the bad...

 

[Mikem53]

Thanks for the summary, Mike! One other item of note: whatshisface over at Audio Science Review hates the ACA because it doesn't measure well and won't drive his 85 db speakers. Will leave it to y'all to decide whether his opinion should be included in the good or in the bad...

You’re Welcome ! I read their review of the ACA and the claim about how he couldn’t even hear the speaker being powered by the ACA, which made me hesitant to even try the NHT’s at first.. Maybe I wired mine wrong.. Seems that site has a few questionable reviews.. Like the Yggdrasil review.. where he used a hair dryer to heat it up Instead of letting it warm up as required for an R2R dac before measurements... and who listens to measurements ? Ive been doing this audio thing long enough to know what and Who to ignore..

 

[Odin412]

Since the Pass ACA amp was brought up, I thought I would add a quick summary from my build experience and forums, research..
the good:
quality parts and circuit card.. not only designed well, but traced on both sides with copper barrels for connection points on a sturdy board.. this is useful for those who don’t solder often, like me.. sturdy thick , etc..
you can supply your own case, PS, parts, etc.. the case in the kit is very high quality, pre drilled for main card heatsink.
Optional switch on rear to wire amp for stereo, mono parallel or Bridged operation. I chose to do this and it’s simple to do..
great Class A sound.. only 2 stages.. no frills, very clean Sounding, quiet background. 8wpc with the 24v 120w power supply.
amp distorts with even order harmonics, like tubes.. never a sharp edge.. very Musical..

the bad:
only 8wpc, not for everyone
since the kit is made for all audiences, the PS is external, 24v for safety. It comes with a meanwell regulated switching PS. Works fine and measures stable.. but I’m going to build a linear PS with more cap storage, more available current..
Have to solder !!! I watched Mr. Carson’s lab, how to solder YouTube video to sharpen my skills.. it took me a week to build only because I didn’t want to screw it up.. Can be done in a few evenings w a bit of soldering experience..
The case was difficult to align because there are so many connection points that need to come together aligned.. but once setup, it’s very sturdy and nice looking and gets quite warm in operation, I measured 122F on the center of the heatsink.. but it’s small in stature, so it’s not a heater..

Summary:
I have the ACA amp hooked up to a pair of NHT super ones. Rated at 86db sensitivity with a sealed, non ported enclosure.. that makes it harder to drive.. I hooked it up as an afterthought thinking it wouldn’t even work.. Yet it can be heard loud and clear in other rooms in the house when I crank it up..
I measured the amp current draw and it showed 81 watts, So that’s quite a bit of heat going up with only 16 watts being used for sound.. that’s the price you pay for that Class A sound.. a worthy trade off..
I don’t like switching power supplies as they tend to be noisy, but I don’t hear any “noise” with this particular model. I am still going to put together my own power supply possibly in a matching case.
I built Heathkit electronics years ago and this kit is the best I’ve ever put together as far as quality and the final product itself. If you’re looking for an amp to power some efficient speakers or even inefficient speakers with a reasonable sound level and you like to tinker with electronics.. then this kit is for you. If nothing else, it shows you how important the first few watts really are, and what a properly designed low power amp can do..

I'm glad you enjoyed the build and the amp! I built the ACA last year but I ended up selling it and getting an Aegir instead, which I enjoy very much. I really liked the bass and midrange of the ACA with my Zu Omen Dirty Weekend, but I never did quite enjoy the treble. Anyway, it was a fun build - and I haven't built a kit since back in the 80s.

 

[Mikem53]

I pulled out my trusty RS sound level meter, and phone app which showed 83dB at 7 feet from the speakers.. No clipping and I had more to go.. This was more than comfortably loud.. I usually listen avg in the low to mid 70 dB range.. I’m in a room 19x15 with 11 ft ceiling. I use this for My PC via optical and usb for the Macbook, which I use for music source. Would be glad to show it off to someone else as Im Pretty impressed with what I’m hearing.. While an HP-555 or BFG-9000 might have measured more accurately... it’s close enough..

 

[ScubaMan2017]

FWIW, I am currently running a pair Magnepan 1.7is off a single Vidar; I have allowed for an eventual upgrade to a second Vidar so I can run both as balanced/mono amps. I can't say I find the current setup wanting though I am by no means pushing the Vidar into high decibel realms.

Tracking right there with you, Renault4. Using a single Vidar to drive a pair of Magnepan LRS's. Have had good success - plenty loud and wall shaking. Got a Yggdrasil GS a few weeks ago and it's really upped the sound quality of the Vidar / LRS combo. So revealing. Last piece - a pair of Magna Risers MK-7 stands. Once those arrive, I think the system is set!

I’m combining the above 2 posts for future reference!

I ran a pair of Aegir amps in bridged mode for awhile when I had a pair of Focal 1028 speakers.. Sounded pretty good..
I then replaced the Focals with a pair of Daedalus Athena’s , I kept the Aegir amps bridged in monos for a couple of months before I
tried a single Aegir in stereo mode.. The difference was not subtle... The sound was way more musical and Class A like.. everything was smoother and more natural sounding.. Plenty of volume and dynamics from the single amp, the daedelus speakers are 95.5 db sensitive with only a 1 ohm drop across the freq range.. so it was a good match for the Aegir in Stereo mode.. The Aegirs in mono mode weren’t near as good as non bridged mode... from my experience.. also had similar experiences in the past with other amps being bridged.. the power comes at the expense of some finesse and loss in naturalness.. have since moved on to a Pass labs XA25 Class A amp.. You can’t beat the Aegir price wise.. but there’s no going back after the Pass..

$4900 - $799 = $4101.

and I’m pairing these 2 post together (for my retirement gift after teaching high school).

I built the Pass ACA 1.8 Class A amp about a month ago.. Was a great experience and enjoyed the challenge.. I wasn’t expecting to be so Good !!
Nelson Pass used some of his private stash of vFET transistors in this kit.. It was able to power my main system... but not enough oomph to drive it
properly... So I set it up in my office .. Macbook pro > Modi Multibit > Magni as preamp > ACA amp > NHT Super ones .. Great sound.. Very quiet background, plenty of volume and bass !! Using one ACA in stereo mode is more than you would expect.. I hooked them up to the NHT, 86 db sensitive and wasn’t expecting it to even work... Yet it sounds glorious and plays louder than I will ever require of it !!

Since the Pass ACA amp was brought up, I thought I would add a quick summary from my build experience and forums, research..
...{{snip}}…
Have to solder !!! I watched Mr. Carson’s lab, how to solder YouTube video to sharpen my skills.. it took me a week to build only because I didn’t want to screw it up.. Can be done in a few evenings w a bit of soldering experience..
…{{snip}}… If nothing else, it shows you how important the first few watts really are, and what a properly designed low power amp can do..

I’m intrigued with the Pass’ first watt philosophy. When I have more time, I’ll pick up a soldering gun and try my first DIY 2-ch amp. My retirement property will have an off-grid electrical system. The more efficient the amps, the better. Or, I’ll pick up a vidar and have it double as a heater.

 

[Mikem53]

I’m combining the above 2 posts for future reference!


and I’m pairing these 2 post together (for my retirement gift after teaching high school).


I’m intrigued with the Pass’ first watt philosophy. When I have more time, I’ll pick up a soldering gun and try my first DIY 2-ch amp. My retirement property will have an off-grid electrical system. The more efficient the amps, the better. Or, I’ll pick up a vidar and have it double as a heater.

You will love retirement !! work is so overrated.. Look to Class D amps for the most efficient use of power.. I’ve owned several iterations of class D topology, including the last 2 , ICE and the HypeX. They are quite impressive sonically, especially for hard hitting music, and easy and inexpensive in DIY form.. If you need a heater, less output and more mass.. Class A amps are great, the side effects on sound are worth it IMO..
I want to try one of those Pass First Watt amps.. they are very specialized and on the raw side when it comes to frills. His amp based on the SIT output device, the SIT-3 is the one I would like to hear.. Pass had a batch of these Static induction Transistors built some years ago and they’re not made or available elsewhere.. so it’s limited to small run of amps.. The Problem is the magic lies in one area of the Sonics.. and elsewhere is sometimes compromised.. As with most things in life... trade offs...

 

[renault4]

I’m combining the above 2 posts for future reference!


and I’m pairing these 2 post together (for my retirement gift after teaching high school).


I’m intrigued with the Pass’ first watt philosophy. When I have more time, I’ll pick up a soldering gun and try my first DIY 2-ch amp. My retirement property will have an off-grid electrical system. The more efficient the amps, the better. Or, I’ll pick up a vidar and have it double as a heater.

I’m a little ahead of you, having retired in July after ~40 years service in bioscience research; as is the case with you, I (I should really say we—) planned ahead on a 2-channel system based around Schiit and Magnepan to be put together once I retired. My family totally surprised me by adding a Schiit Sol/Mani combo to the system, with our children, friends and my siblings all sending albums to commemorate the event. As @Mikem53 said, you will love retirement! I found that the hardest part was getting used to getting up in the morning or going to bed in the evening and NOT thinking about work—for the rest of the day, once you fire up those Maggie’s, nothing else matters much.