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AnthonyA 28th June 2019 02:20 PM

USSPA Build thread
1 Attachment(s)
Hi everyone,

I had been participating passively. And following the diy progress of Dominic aka Pinnochio. Excellent diy work and built and learn alot from the posts.

I came across this interesting preamplifier. Ultra simple symetrical preamplifier by fabaudio. I couldn't find any open group buy for it and contacted Fab direct and he graciously let me have the pcb. Thank you Fab.

This is an extremely exciting project for me because my buddy have all the transistors in stock. And he kept raving about them. But hey.. Where is the fishished goods?? Attachment 765406Fab have a great design.. Let's do it!
Happy to find a great heat sink locally. Start populating the board
Some of the parts is non existance locally
Like the cap and feedback R. Waiting for them. I like to use carbon film for gate resistors especially with mosfets and with my experience the sound is much more heavy and musical . The rest will be a mix of quality parts.

Talema toroid is ready and I'm also waiting for the supply module. I prefer lt 1963 lt 3015. As it have a good mix of quietness, dynamism and pssr. Yet will not dry out the music, ringing etc. I use them successfully in a few projects. I had tried alot.

Depending on the shipment. I will update accordingly


fab 30th June 2019 02:49 AM

I will follow your thread closely ;)

AnthonyA 2nd July 2019 12:30 PM

1 Attachment(s)
Attachment 766034

Just waiting on some capacitor from ebay. Uk and we are good to go.

Hard to find high quality 4.7r. So used holco 5.1 ohm
0.33r dale for ground break, which should be fine.

fab 3rd July 2019 04:36 AM

Your selected resistors values are fine.

Just a note that C2/C4 and C3/C5 values and cap type are selected to get the lowest resulting impedance at all relevant frequencies so it is recommended to stick to the BOM for these power supply caps.

AnthonyA 15th July 2019 06:20 PM

2 Attachment(s)
I hear ya fab found the x7r smd samsung

Caps all here. Just waiting for my buddy to dig out the jfet

Already matching the finals as we speaks
Attachment 768448
Attachment 768449

AnthonyA 15th July 2019 06:42 PM

2 Attachment(s)
Attachment 768452

Transformer ready. Rs. Which is high quality. And i got this favourite ic. Well if its suitable. Will get 2 for dual mono.

I may run it 15v or 17v depending how it sounds

Already have both super through or mundorf main cap. Will try both to see which one better. I would probably use schottky diodes. Also depends how it sounds

5mm base plate aluminium.

AnthonyA 24th July 2019 05:19 PM

2 Attachment(s)
:DAttachment 770446
Attachment 770447

Finally tr matched after much hunting around the net for the unobtaniums jfets
Jfet within 3% idss
And the fets at 1% vgs
Slapping on thermal paste on them was so satisfying

Got a few mishaps with fakes and luckily a good Samaritan pointed me to the right direction.
Now I got enough of the fairy dusts for fssa amplifier:wiz::hbeat:

AnthonyA 31st July 2019 07:41 PM

I had completed the preamplifier for almost a week.
Attachment 771733

I had installed it inside a diy goldmund mimesis clone to make it a integrated amplifier.
I'm going to do a first below 100 hours review. Break in was quite straight forward. Bias at 80ma. With a 1963/3015 power supply at 15v. Very easy to get it to run.. The documentations from Mr Fab is class A+. Smooth operations

Preamplifier that i often listen to.
Tron seven
Conrad Johnsons.
Mark Levinson
Sonic frontier
Pro stuffs
Sansui Marantz luxman. And so on and so forth

Some I own and some I borrowed or at my friends house.

Associated equipment DAC. Mirand 4490 with discrete output with usbridge allo.

Speakers nht 2.3a / Yamaha ns 10. The two I tried.

Cables. Acro link rca2200ii Speaker cables1010. Power cable pc7300.

Usspa is extremely transparent without being thin and irritating. But., since it's very transparent. Careful matching is necessary. It like neutral sounding cable. For me it's acro link black rca.

The stage is like a class a sound. Huge, room filling. Wide. Each sound is placed well separated., more to the front and more to the back. It sounded more like MBL kind of sound stage, all rounded, front seat, very different from like Mark Levinson/tron which is more raw and linear middle of row seat. Very quiet background. No noise whatsoever. Good design.

Vocal is class A like. Light airy, thick focused, bloom, without glare. The bass is not the punch it dynamic type. But articulate heavy enough and satisfying enough. The low releases well and it gets better with time.. Since transformer is also new it takes time to get better. What it does better than the rest of preamplifiers is the atmosphere and reverb. Enough slam and excitement. Linearity is good. Thick and focus but too bloated. Not too colored to make everything sound the same. Great dynamic bandwidth where it should be soft it's very soft
. Where it should be dynamic its dynamic. Musicality is good, slightly. more than ml or tron but not too mushy. It's a little more "colored" in that sense.. More informations compared to ml or tron however. Which I like!

I threw all sorts of music. Pop. Jazz. Classics. Vocal. Acoustics. It does very very well on difficult tracks. Like LA bamba by ozone percussions. Santana black magic woman. Adele. If you can listen to the whole track without losing interest.. They have such flat recordings.

So it's a top tier preamplifier that does a lot of things well and beyond and you don't have to spend a bomb. Which I did .. And man.. Well it's a journey right?

Don't think I should say too much yet since it's a 100 hour below review. Not completely cohesive yet. I shall post a long term review after more burn ins.

Going to bring this to more friends with more experience and see how it fares. MY Buddy is making his usspa as well. And I will post if I have something interesting to say. Or not :D

But for now., very impressed with this preamplifier. Thank you. Fab for your pcb, designs, and wisdom.

Thanks everyone for reading.

fab 1st August 2019 04:18 AM

Thank you AnthonyA for your comments and for this detailed preliminary review :). I believe you have assembled the USSPA1 (mosfet output) version.

I would be interested to get also feedback for the USSPA2 (Sanken bjt output) version. Maybe your friend?

Note that your attachment does not show in your last post.


AnthonyA 1st August 2019 05:08 AM

2 Attachment(s)
Attachment 771878
Completed integrated amplifier
Attachment 771879

My buddy on test. Bias slightly smaller. Waiting for heatsink.

Carbon resistor mostly

He said it's crazy good.. He is a much more experieced diyer than me. He repair hifi audio for living

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