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ACA Vs First Watt?


Mark51

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I just got a Pass ACA amp on eBay.  It was already assembled - not a Chinese copy but the DIY store version.  Sounds good with my Fortes.  I'm curious if anyone has listened to both and ACA and a First Watt.  How would you compare?  I realize the price difference is thousands of dollars and I would expect the First Watt to sound better, but how much? Thousands of dollars better?

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} I’ve owned both, still have a FW F3. And you never specified - lots of flavors in the FW lineup?

I really liked my ACA monoblocks which were built with vastly oversized power supplies, one for each block and much larger than the wall wart delivered with the standard design. To be sure the power supply was larger than the mono itself. In the end the F3 easily beat the ACA, which it should. Find a used FW and find out - 

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On 2/2/2020 at 3:22 PM, richieb said:


} I’ve owned both, still have a FW F3. And you never specified - lots of flavors in the FW lineup?

I really liked my ACA monoblocks which were built with vastly oversized power supplies, one for each block and much larger than the wall wart delivered with the standard design. To be sure the power supply was larger than the mono itself. In the end the F3 easily beat the ACA, which it should. Find a used FW and find out - 

I was contemplating ACA or F3. It is for 115db horns (only mid/high not bass)

Would you mind elaborating the sound difference exactly between the two for me. 

I prefer a little softer very smooth and on the warm side for this revealing sensitive horn. 

Especially smooth upper mid range. 

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20 hours ago, Nos1 said:

I was contemplating ACA or F3. It is for 115db horns (only mid/high not bass)

Would you mind elaborating the sound difference exactly between the two for me. 

I prefer a little softer very smooth and on the warm side for this revealing sensitive horn. 

Especially smooth upper mid range. 

The F3 is a better amplifier than the ACA. I have built them both. The ACA is a simple circuit amplifier designed by Nelson as a diy project for a beginner amplifier builder to get a taste of what a class A mosfet amplifier sounds like. The F3 uses what is called power J-fets which also the more modern Firstwatt J2 uses. If you want more details of the F3 circuit you can look here.  https://firstwatt.com/pdf/art_zv9.pdf The Zen 9 from 2006 is the same circuit retailed as the F3. Both are very good sounding but if hearing good enough you will hear a difference in the F3. 

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I built 2 ACA amp's, set them up as monoblocks with XLR inputs and linear power supplies. They are impressive little amps! 

 

Then I built an F-5, F-6, B1K preamp and finally an Aleph J. They all sound great and are improvements over the ACA's.

 

I'm currently using two Firstwatt F8's. They sound really good and are definitely an improvement over the Aleph J, which was my favorite of all the DIY boards that I built.

 

Who knows what a couple of Sit-4's will sound like?

 

I might have to find out when they become available.

 

F8s.2.jpg

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2 hours ago, DMH said:

Henry,

 

To clarify this, you built the 2017 Sony Vfet amp?

https://diyaudiostore.com/collections/power-amplifier/products/sony-vfet-circuit-boards

 

And the 2021 Vfet amp offering?

https://guides.diyaudio.com/Guide/Sony+Vfet+(P+2021)/15?lang=en

 

Have you built any of the other Firstwatt DIY amps?

I was the first builder of the PP SET amplifier at diyaudio.com. I also am the one who asked Nelson for a SE V-fet design and he agreed to design one. It took a few years but he did produce it. Also I have built the majority of Nelson Pass diy projects including nearly all of the Firstwatt clones. Nelson Pass 74 year old groupie.

 

If you like the sound of the ACA you would love the sound of the Burning Amp #1 SE amplifier with multiple output devices. https://firstwatt.com/pdf/art_ba1.pdf  The Burning Amp #2 has a lot in common with the Pass Labs amplifiers. Similar to the F4 with an extra output stage if memory is correct with a front end circuit added where it will operate without a high output linestage that the F4 really needs for full output. 

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7 hours ago, DMH said:

Henry,

 

To clarify this, you built the 2017 Sony Vfet amp?

https://diyaudiostore.com/collections/power-amplifier/products/sony-vfet-circuit-boards

 

And the 2021 Vfet amp offering?

https://guides.diyaudio.com/Guide/Sony+Vfet+(P+2021)/15?lang=en

 

Have you built any of the other Firstwatt DIY amps?

DMH....Sent you a PM attached to an old PM...hope you get it. If you don't respond I'll send a new PM.

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17 hours ago, henry4841 said:

I was the first builder of the PP SET amplifier at diyaudio.com. I also am the one who asked Nelson for a SE V-fet design and he agreed to design one. It took a few years but he did produce it. Also I have built the majority of Nelson Pass diy projects including nearly all of the Firstwatt clones. Nelson Pass 74 year old groupie.

 

If you like the sound of the ACA you would love the sound of the Burning Amp #1 SE amplifier with multiple output devices. https://firstwatt.com/pdf/art_ba1.pdf  The Burning Amp #2 has a lot in common with the Pass Labs amplifiers. Similar to the F4 with an extra output stage if memory is correct with a front end circuit added where it will operate without a high output linestage that the F4 really needs for full output. 

Very impressive! I'm a relative newbie to Nelson Pass's designs. I appreciate his work but I'm not even close to a "Nelson Pass groupie". Not that there's anything wrong with that.

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1 hour ago, DMH said:

Very impressive! I'm a relative newbie to Nelson Pass's designs. I appreciate his work but I'm not even close to a "Nelson Pass groupie". Not that there's anything wrong with that.

The difference with Nelson and the other audio engineers is he shares some of his knowledge with the electronic audio geeks. 

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26 minutes ago, henry4841 said:

The difference with Nelson and the other audio engineers is he shares some of his knowledge with the electronic audio geeks. 

That's totally true! Let me tell you, I purchased a used Firstwatt amp from ebay that made a thunking noise when you turned it on. It was like the noise that happens when you turn on a high current bus, like in a factory but on a much smaller scale. I didn't want to return it because it sounded great. So, I looked on the Firstwatt webpage for some sort of customer service email. There was a single email address and it turned out to be Nelson's personal email address. He graciously explained what he believed may be causing it and was certain it wasn't a problematic issue. Although he encouraged me to send the amps in to the shop to have them checked out under warranty. Talk about being customer service oriented!

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