Pass ACA Class A Power Amplifier Review

[HornJunkie]

Does Hafler still sell kits?
If so, the Hafler is a well engineered, clean, powerful amp that would have performance far exceeding the Pass ACA amp.

what or who is Hafler?
pls send me a link

best Regards,

Florian

 

[MRC01]

what or who is Hafler?
pls send me a link ...

https://hafler.com/
They used to sell each amp in two ways: factory built ready to use, or as a kit you build yourself.

 

[HornJunkie]

There's a ton going on in the DIY world building SOTA measuring and sounding class D amps. Check out a couple other sites like DIY Class D, and Ghent Audio. You could then build a amp that will give you decades of accurate listening pleasure.

But I don’t want class D.
I want a small class a amp, with a lot of power consumption and less power.
Maximum 40 watts, because I just want to drive my horns active and no bass drivers. For bass I’m using a Parasound 1206 amp.

PS: I’m from Germany, not US
Because shipping from US to EU is not cheap and I have to pay taxes.

best regards,

Florian

 

[MRC01]

... But I don’t want class D.
I want a small class a amp, with a lot of power consumption and less power.
Maximum 40 watts, because I just want to drive my horns active and no bass drivers. For bass I’m using a Parasound 1206 amp.
...

In that case, here's another idea. Many years ago I had a SET OTL headphone amp called the Wheatfield HA-2. I really enjoyed it and the OTL was well suited to driving high impedance headphones like the HD-580 and HD-600 of that era. It was designed by a fellow named Pete Millett, who has a site with several different amp designs. Some of them may be just what you're looking for.

 

[mhardy6647]

https://hafler.com/
They used to sell each amp in two ways: factory built ready to use, or as a kit you build yourself.

David Hafler was -- ahem -- also the founder of Acrosound and Dynaco.

 

[LTig]

But I don’t want class D.
I want a small class a amp, with a lot of power consumption and less power.
Maximum 40 watts, because I just want to drive my horns active and no bass drivers. For bass I’m using a Parasound 1206 amp.

PS: I’m from Germany, not US
Because shipping from US to EU is not cheap and I have to pay taxes.

best regards,

Florian

Seriously: please think about it again. A 40 W class A amp will emit a lot of heat when switched on, regardless of volume. My neighbor had such and sold them because in summer time his room got too hot, and heating it in winter time with electric power is much more expensive compared to oil or gas central heating.

Spoiler

Anyway: waisting power for nothing is no responsible way to deal with our future.

 

[Sal1950]

Every time I look they are about $250 with shipping, they seem to have gone up in the last few years.

It appears there's a little cult growing around the Adcom GFA amps, glad I got mine when I did. I got 5 on active duty and one in reserve just in case.

what or who is Hafler?

If there was an official HiFi Hall of Fame, Davids name would be right at the top. He expanded on work of Williamson and Blumlein to bring the Ultralinear tube-transformer circuit to the popular market. I believe his Dynaco ST-70 stereo tube amp holds the record of the best selling amplifier of all time. He also later popularized the Hafler circuit, a way of hooking up the + and - sides of a stereo amp to extract ambiance for rear speaker use. One of the first surround sound ventures that later was expanded into the matrix attempts. There's tons of info on David but a simple wiki search will fill in some of the big blanks.
https://en.wikipedia.org/wiki/David_Hafler

 

[HornJunkie]

Seriously: please think about it again. A 40 W class A amp will emit a lot of heat when switched on, regardless of volume. My neighbor had such and sold them because in summer time his room got too hot, and heating it in winter time with electric power is much more expensive compared to oil or gas central heating.

Spoiler

Anyway: waisting power for nothing is no responsible way to deal with our future.

I don’t want a 40 watt amp, was just a range for inspiration.
I prefer a 5-20 watt amp.

And yes, they need a lot of power, but this is passion and if you are not driving the amps 24/7, it’s fine in my opinion.

best regards,
Florian

 

[mhardy6647]

Single ended 2A3 for 3.5 watts'll do you fine.
Eschew that Roswell/alien flying saucer* transistor technology!




____________
* Those fun-loving engineers even hinted at the extraterristrial origin of these infernal devices right there in the design of some of 'em, for all to see -- those jokers!

 

[MakeMineVinyl]

I don’t want a 40 watt amp, was just a range for inspiration.
I prefer a 5-20 watt amp.

And yes, they need a lot of power, but this is passion and if you are not driving the amps 24/7, it’s fine in my opinion.

best regards,
Florian

5 - 20 watts is the ideal range for direct connection to a highly efficient horn. Any more than that is utterly wasted (I'd argue that more than a couple watts is wasted), and there is increased risk of blowing out the diaphragm either unintentionally or by electrical fault (a series cap won't help with too much power!). The power consumption issue I can easily see if we're talking a 50 watt single ended amp, but a low wattage single ended amp actually draws less power than a conventional class A/B home theater amp.

 

[dtaylo1066]

There are some very inexpensive, minimal parts and solid performing chip amp DIY projects out there.

 

[HornJunkie]

There are some very inexpensive, minimal parts and solid performing chip amp DIY projects out there.

actually I’m watching the Chinese diy kits on eBay.
Often you just only need a power transformer, because the board have already everything else.
I think i try some boards.

 

[HornJunkie]

5 - 20 watts is the ideal range for direct connection to a highly efficient horn. Any more than that is utterly wasted (I'd argue that more than a couple watts is wasted), and there is increased risk of blowing out the diaphragm either unintentionally or by electrical fault (a series cap won't help with too much power!). The power consumption issue I can easily see if we're talking a 50 watt single ended amp, but a low wattage single ended amp actually draws less power than a conventional class A/B home theater amp.

BTW, my HF horns (500Hz crossover) are 107dB efficient, just a tad more than yours. I can create blisteringly loud sound while not even coming close to the limit of my 2.5 watt SET on the HF horn. The lower frequency horn handles below 500Hz and these are driven by a 40 watt amp which is coasting along the vast majority of the time, if not all the time. Where the real power output is needed is the subwoofers, and those get 1000 watts.

Ohh 500hz crossover? Which Horn and which driver?

so I think we share the same point of view

 

[levimax]

But I don’t want class D.
I want a small class a amp, with a lot of power consumption and less power.
Maximum 40 watts, because I just want to drive my horns active and no bass drivers. For bass I’m using a Parasound 1206 amp.

PS: I’m from Germany, not US
Because shipping from US to EU is not cheap and I have to pay taxes.

best regards,

Florian

See below 3 DIY class A amps. There are boards available for 2 of them. ESP projects are well documented and work and I can highly recommend them.

https://sound-au.com/project10.htm

https://sound-au.com/project36.htm

https://sound-au.com/project3b.htm

I built the project 3b a 25 watt class A and it worked well but I can not recommend a class A power amp. They are expensive to build, require a huge and expensive case, and generate an unbelievable amount of heat.

The Neurochrome Mod-86 amp, which I also built, makes much more sense. It is class AB but very low distortion and extremely quiet and will work great with your horns.

https://neurochrome.com/products/modulus-86

Good luck and have fun.

 

[SIY]

Single ended 2A3 for 3.5 watts'll do you fine.
Eschew that Roswell/alien flying saucer* transistor technology!




____________
* Those fun-loving engineers even hinted at the extraterristrial origin of these infernal devices right there in the design of some of 'em, for all to see -- those jokers!

View attachment 105461

TO-36 or GTFO.

 

[mhardy6647]

TO-36 or GTFO.

View attachment 105489

Game, set, and match.

 

[mhardy6647]

See below 3 DIY class A amps. There are boards available for 2 of them. ESP projects are well documented and work and I can highly recommend them.

https://sound-au.com/project10.htm

https://sound-au.com/project36.htm

https://sound-au.com/project3b.htm

I built the project 3b a 25 watt class A and it worked well but I can not recommend a class A power amp. They are expensive to build, require a huge and expensive case, and generate an unbelievable amount of heat.

The Neurochrome Mod-86 amp, which I also built, makes much more sense. It is class AB but very low distortion and extremely quiet and will work great with your horns.

https://neurochrome.com/products/modulus-86

Good luck and have fun.

Yes, Eliott Sound Products -- good stuff. Y'all know his website, yes? Lots of good information there.
https://sound-au.com/

 

[anmpr1]

Wait a minute... isn't that the HF driver on the Schmidlapp Zeta 10000 Electrophonic omni-octapolar speaker?

 

[mhardy6647]

Wait a minute... isn't that the HF driver on the Schmidlapp Zeta 10000 Electrophonic omni-octapolar speaker?

View attachment 105584

Gadzooks!
I think I have a pair of those in the basement!

 

[peng]

I don’t want a 40 watt amp, was just a range for inspiration.
I prefer a 5-20 watt amp.

And yes, they need a lot of power, but this is passion and if you are not driving the amps 24/7, it’s fine in my opinion.

best regards,
Florian

The ACA amp would do what you want it to do if all you need is 5W for your speakers to produce your desired spl. So I would suggest you figure out your power need first, based on the distance, speaker sensitivity and your desired maximum spl.

In the event that you are going to do it, I would suggest you use and external fan (I used two), and I think the capacitor thing is a good idea.

Peak SPL Calculator (homestead.com)