FSSA amplifier build thread with review

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#101
Hi
As anything in life PSU sizing is a compromise. Being a CFA amp it needs a good energy reserve PSU. I have 4 ohms nominal speakers with a minimum of 3 ohms.

I have one FSSA with dual mono PSU, each having:
200VA transformer
Diodes rectifier bridge(2)
CRC: 15000uF-0.1 ohms- 15000uF
Bleeder resistors

You can also use:
-an ideal bridge based on mosfet for the diode bridge
4700uF-0.1 ohms- 22000uF for CRC or use CLC instead
- use a 300VA transformer (my FSSA2)

As for SMPS I am not a fan of them but use at least 800W each.

One of my FSSA is about 50Wrms / 8 ohms and the other one is about 80Wrms / 8 ohms or so. So for 125Wrms / 8 ohms do not go below the above.

Fab
 
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#103
Another expert level ears came, his system is 100k above too. Lover of classical and acoustic music.. Passed with flying colors in that genre.. Only lose a bit of zing.. He have diamond tweeters I have silk dome. But cymbals is still palpable..

He mention.... Some of the details in the recording is unheard of..is that echo or reverb.? .. The transparency, calmness and space is extraordinary. Musicality is as good as it can be, the right amount of dynamism yet softness.

The bass is legendary. Not only it's saturation. Detailed yet controlled. Super wow cause it's diy... He said.. Maybe goldmund mono ? Mark levinson tower.? But hmm he don't remember it to be that good..

He say the designer of the circuit is very talented. Got where it should be. Impressive
 
#104
Which amp are you referring to Anthony? Without searching I seem to remember that you have more than one of Fab's great amps. Were you using his pre as well or just a V/C?

General:

I am not able to source in Europe (reliably) ANY of the Driver or output devices by Sanken;

ALSO as I have lots of closely matched Toshiba devices I think that the USSA-5 (original) is probably a good bet for me. I understand from the manual that my boards are OK....BUT do any of the component values need to be changed?
 
#105
Fssa 2
Usspa 1 and 2

Pinnocchio usspa, fssa and ussa 3 and 5/meanie build a few of ussa and usspa,


Ussa 5 is just softer and more musical. Fssa is class ab
. It have the headroom..dynamic and punch but still have class a characteristic , but exceptional capability to drive the speakers . Different of the same thing
 
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#106
AnthonyA said:
Another expert level ears came, his system is 100k above too. Lover of classical and acoustic music.. Passed with flying colors in that genre.. Only lose a bit of zing.. He have diamond tweeters I have silk dome. But cymbals is still palpable..

He mention.... Some of the details in the recording is unheard of..is that echo or reverb.? .. The transparency, calmness and space is extraordinary. Musicality is as good as it can be, the right amount of dynamism yet softness.

The bass is legendary. Not only it's saturation. Detailed yet controlled. Super wow cause it's diy... He said.. Maybe goldmund mono ? Mark levinson tower.? But hmm he don't remember it to be that good..

He say the designer of the circuit is very talented. Got where it should be. Impressive
Click to expand...
Thanks for the feedback AnthonyA!
But I do not consider myself talented, maybe just more experimented in the specific sound I am looking for...
Glad you and your firiends appreciate a similar sound as I do.🙂

You can also take the credit of your proper build assembly.

A quick observation is that your FSSA with it’s quite high bias for an class AB amp operates mostly in class A even at moderate levels.😉

Fab
 
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#108
AnthonyA said:
Fssa 2
Usspa 1 and 2

Pinnocchio usspa, fssa and ussa 3 and 5/meanie build a few of ussa and usspa,


Ussa 5 is just softer and more musical. Fssa is class ab
. It have the headroom..dynamic and punch but still have class a characteristic , but exceptional capability to drive the speakers . Different of the same thing
Click to expand...


My USSA5B heatsinks n chassis is still with the machine shop since this Covid lockdown, USSPA is done and tested, awaiting new preamp chassis.
There is nothing much i can do now, has been reading about speakers building during this period.

Be safe everyone!
 
#116
brianco said:
...
General:

I am not able to source in Europe (reliably) ANY of the Driver or output devices by Sanken;

ALSO as I have lots of closely matched Toshiba devices I think that the USSA-5 (original) is probably a good bet for me. I understand from the manual that my boards are OK....BUT do any of the component values need to be changed?
Click to expand...
Hi Brianco
Digi-Key in Canada has plenty of the Sanken driver. The latter are for the USSA5.1 or USSA5B or USSA3B.

If you already have the matched Toshiba devices than you sure can build the original USSA5 with them which is the USSA5 version built by all other members so far.
The manual clearly shows the difference in parts for all USSA5 versions.

For the FSSA1 or 2 this is a different circuit and different pcb.
FSSA1 is with Matched Toshiba drivers and FSSA2 is with Sanken bjt drivers.
Fab
 
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#117
stretchneck said:
FSSA-1 - can the gain be adjusted, or is it fixed at 20dB?

I'd be interested in the GB.
Click to expand...

As per post #9 circuit, the gain is 17.5 thus 24.9dB. It could be slightly modified but not much to avoid changing frequency stability. This should be adequate for a 100Wrms amplifier.

Signal to noise ratio is difficult to predict since it depends on your whole amplifier implementation (PSU, wire routing, ...).

Fab
 
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