Is ST FFX the same as DDX ?


2013-12-22 6:40 pm

When I browse the ST catalog for their digital amplifiers, I find some products stamped DDX (like the STA326), and some FFX (like the STA350, STA508...).

I understand that the DDX is the renowned legacy of Apogée.

Is FFX the same stuff rebranded for some reasons, or is it a different technology, that may be expected to sound different?

I could not find information about similarities/differences on ST website. New chips seem to be FFX.

Best regards,



2016-09-01 12:28 am
hi JMF11,

when you look into the datasheet of STA516BE (FFX amp), you read this:
"This result was obtained using the STA309A+STA516B demo board."
"A cost-effective, high fidelity audio system can be designed using ST chipset, including a modulator (e.g. STA309A or STA321) and the STA516BE."

The STA309A has a DDX output, and the STA321 has a FFX ouput...both work fine, as they say, with the STA516BE amp, which has an FFX ouput. I think both DPSs also will work this the STA516B amp, which has an DDX output.
So my conclusion is, that there is no big difference. But i also read about, that in some DPSs you have to set through special bits, if you use DDX output or FFX output...

it's so a hard thing to find some information about this...
but i will try it out by my own, and maybe i will post some of my workout

Harman Kardon HS500 + HS200


I refresh (hopefully...:D an HS500)
On the amp boards i see this Power AMP DDX2160, and the DSP chip DDX-8001. According to the datasheet it is a very good combo. (2006;))

at the HS 200 model (stero model -2.1 channel) is the STA508 power amp and the STA308A as DSP.

Question 1
Which configuration sounds better?which experience do you have?

Which modifications make sense if you look at the pics:
Q2 the original inductors are silver collored and magnetic shield and according to both service manual (HS 200 and HS500) 15µH..the power of both chips are about 4,5 amps so are the too small?

the original sticker to fix the colling plate to the chip is a double side sticker! is that a joke ???!!...i will replace this with washer in respect to don´t push to hard the screws for the cooling fan.

In the datasheet of STA508 (should be similar to DDX2160) is the Cap near to the chip recommended as 1000µf with 50V. but the power supply is 34V. so is that because of return energy from the speakers? or could i use a bigger size e.g. 4700µ with 35V???
the only topic is that the room for the cap is limited at 18mm diameter and about 40mm high.



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i try it again with some power Caps (e.g. class d normally 100µF/50V) issues:

Does it make sence to use on the amp PCB "audio grade" caps or is it better to use low/ultra low ESR caps "no audio" grade brand??

any experiences????

my experince - on 2 x Harman Kardon HS200 refurbished

different input (analog input PCB) one had the original "normal caps" the other has some audio grade caps
both full identically at PSU CAPs and Power caps on the power amp board

result: the "audio grade" caps sound better,better timing, more deeper room, more details

Laptop-foobar- - aduioquest diamand -DAC Gustard A20H - HS200 - open baffle 12.5(or KEF Q100)

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