[gychang]

I hear from a reliable source this amp is very good, so I ordered and finally received 2x from china.
http://www.ebay.com/itm/400738359092?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

somewhat confusing description:
Comes with 4 groups gain mode settings
The chip comes with amp function (need extra components), what does it mean?

Does anyone know how to adjust gain?, no answer from the seller.  I have not hooked it up yet...

[FullRangeMan]

I would say its fixed gain, hence the FX term in the board model:
2578AY-FX and FX138/5

[Markvdv]

http://www.elserw.com.pl/baza/PDFy/YDA138.pdf

FX are initials producer ampboard

[gychang]

http://www.elserw.com.pl/baza/PDFy/YDA138.pdf

FX are initials producer ampboard

thanks, no obvious way to adjust gain in my view...

[Doublej]

There is a section on First Stage Amplifier Gain Setting Function on page 6. Not exactly sure what it means though in response to your question.

[gychang]

There is a section on First Stage Amplifier Gain Setting Function on page 6. Not exactly sure what it means though in response to your question.

I wanted to know if there was a switch of some sort that can change the gain.  Usually when I listen thru my PC, the pot is at maximum and when listen from my CD player, pot is way down to "normal" position...

[gychang]

I got a chance to listen to the board on my diy bookshelf speakers.

It sound very nice in stock form.  Pleasantly surprised, wonder on higher end speakers how it would sound.
On default gain, it seems to be louder at maximum gain than my TA2020 Helder amp.

It also has a built-in headphone jack which seems to work, but not much of a heaphone person.

Would be interested in others and encourage others to spend some change to see what u all think...

[FullRangeMan]

Seems the gain are the L1 L2 L3 L4 blue K220, two per channel.

[gychang]

Seems the gain are the L1 L2 L3 L4 blue K220, two per channel.

guess not really adjustable without soldering....

[JohanH]

Seems the gain are the L1 L2 L3 L4 blue K220, two per channel.

L1 to L4 are the output inductors so have no influence on the gain.
The chip provides an input sensitivity setting (pin 26 & 27) but I don't know how this is implemented on this pcb.
On the extra amp function: it seems the chip has a separate headphone amp (2x50mW) so you'd probably need some parts added to the pcb to use it.

Cheers,
Johan

EDIT: what Doublej said points to setting gain. Next time I'll try to read first before answering...

[FullRangeMan]

The PCB description say:
Built-in 4 groups Gain Mode, can adapt to different sources.
Which seems an auto gain setting inside the chip, not a manual control gain.

[JohanH]

The PCB description say:
Built-in 4 groups Gain Mode, can adapt to different sources.
Which seems an auto gain setting inside the chip, not a manual control gain.

And doublej pointed correctly to the chips datasheet that states gain control is set by 2 pins

[FullRangeMan]

And doublej pointed correctly to the chips datasheet that states gain control is set by 2 pins

As I said before fixed gain.

[gychang]

for this novice, is there a switch of some sort ?

[JohanH]

for this novice, is there a switch of some sort ?

No, no switch.
You'd have to identify pins 26 & 27, see how they are connected now and then make a decision on if you'd want to change the settings.
You could add a switch.
Both require some experience with smd soldering.
So, not for the novice I'm afraid.

[gychang]

No, no switch.
You'd have to identify pins 26 & 27, see how they are connected now and then make a decision on if you'd want to change the settings.
You could add a switch.
Both require some experience with smd soldering.
So, not for the novice I'm afraid.

thanks, SMD soldering, can't do.

[FullRangeMan]

SMD soldering not easy and can change the chip performance.
Otherwise it inexpensive.