Stereo or mono tpa board with low gain

[flo777]

Does anyone know of any tpa or similar boards with relatively low gain? 20 to 26 db?
I'd like to use one on my desktop speakers with a small tube preamp.

 

[FauxFrench]

Any TPA3116 board can be set to 20dB gain. Better get a board where the heatsink is fixed with screw(s).

 

[flo777]

Right, but I was hoping to find a board already set at low gain, since I don't have an iron good enough to desolder such small resistors

 

[jemraid]

Hello Flo,

Here's a how to vid,
YouTube
Using an ordinary soldering iron.

And this is the best board to do it on: XH M590 carte amplificateur de puissance numerique tpa3116d2 carte amplificateur audio double 100W haute puissance 12 24V | AliExpress the one that FauxFrench advises

Cheers - Jem

 

[flo777]

Thanks FauxFrench and Jem for the tips.

Actually I already have the xh-m190 v3 tpa3116d2 board, but it has high level of hiss. I read that this is due to high gain.

Table 1 on page 14
https://www.ti.com/lit/ds/symlink/t...966561&ref_url=https%3A%2F%2Fwww.google.ca%2F

I attached a photo of my board. It has R1 of 100k and R2 of 1RD (100k?)
I'm a little confused. Do I just need to remove the R2 resistor to get 20 db gain? What's briefly the difference between the master and slave gain?

 

[jemraid]

Hello Flo,

Thanks for the message good of you. Not the two resistors you mention please leave those. Look for these two together 473 (47K) and 753 (75K) you will find two pairs of them one for each amp. Remove the 753 and the hiss will go and the hum will be all but inaudible, and the pops at startup and switch off will go as well.

Thanks to FF my board was the similar but the cure the same.

Cheers - Jem
The master/slave configuration is various combinations of resistors, the chip recognises which is in place.

 

[FauxFrench]

flo777, would it be possible that you remove the heatsink, takes of close-up photo of the two TPA3116 ICs and the resistors around? Your board is different from ours. You write that yours is a XH-M190 while ours are XH-M590.

 

[jemraid]

Hello Flo,

Just to make sure here's a couple of pics of my board yours will very likely be similar

An externally hosted image should be here but it was not working when we last tested it.

The group of three is duplicated above the highlighted group and these are under my heat sink.

and a close up

An externally hosted image should be here but it was not working when we last tested it.

Hope this helps.

Cheers - Jem

[edit] We had a similar idea at the same time FauxFrench

 

[flo777]

Sure, please see the attached photo.
How can I get the minimum 20db gain (since I'd like to use a preamp with it), and do you think that will also improve the low frequency response along with removing the hiss?
Thanks

 

[FauxFrench]

Hi flo777,
On your board, U1 is set as "master" with 26dB gain (100K/20K) and U2 as "slave" with 26dB gain (47K/75K). The two ICs are synchronized.
If you turn the volume potentiometer fully down, do you still have much hiss?

 

[flo777]

Hi FauxFrench, thanks for clarifying.
With the volume down I don't get much hiss.
However, I'd like to use this board with the volume at max, and then use a tube preamp.
Perhaps I should be looking for other boards in this case.

 

[FauxFrench]

Could you please try hiss with the volume potentiometer at MAX. (full) but the two input connectors short-circuited (signal-line to ground)?
This test will show if your hiss actually comes from the previous stage.

 

[flo777]

Actually I tried the preamp with another amp and the hiss was much less.
I thought the gain would be higher than 26db.
With the volume at max, I can only turn the preamp volume very little before it's too loud. Maybe I already have enough gain in the preamp.

 

[FauxFrench]

Hi flo777,

You have too much gain in the total signal path the way you describe the functioning of the pre-amp volume. Then you typically end up with much hiss.
You can reduce the TPA3116 gain from 26dB to 20dB but that will only reduce the hiss a little. It requires that you remove the 100K resistor for U1 (master) and replace the 75K resistor with 47K for U2 (slave). Removing an SMD resistor is not so difficult, changing an SMD resistor is somewhat more difficult.

Better is, I believe, to put two 2K2 resistors at the output of the TPA3116 board volume potentiometer such that the input-impedance the TPA3116 IC sees is not higher than 2K2 and the TPA3116 IC makes little hiss itself. Then, you connect the TPA3116 board to the pre-amp and put music on, with the pre-amp volume set to 12 o’clock and the TPA3116 board volume turned fully down. You turn the TPA3116 board volume up until you have a good music listening level.

After that, you leave the TPA3116 board volume in this position and use the pre-amp volume to increase or lower the sound level. The TPA3116 board volume potentiometer then serves as an input sensitivity adjustment stage to the TPA3116 IC and you have little hiss.

 

[jemraid]

Hello FauxFrench,

Thanks for the explanation, although I'm not going to use a preamp just an external volume control I will do what you suggest above to start the process off. It's good idea.

Cheers - Jem

 

[flo777]

Hi FauxFrench,
Thank you for the detailed explanation.
So if I put 2k2 resistors at the potentiometer output, I will not have to worry about removing an SMD resistor.

I was also thinking that I can get other stereo board or two mono boards, so I don't have to worry about turn on/volume adjustment.

Also, I noticed that the filters are 10uH or 33uH, and that the 33uH are really suitable for 8 ohm speakers. Do you know about this?
I'm using 4 ohm speakers.

These are the mono boards:
XH-M544 DC 12V 24V 150W TPA3116DA TPA3116 D2 Mono Channel Digital Power Audio Am - US$8.55
DC 12V-24V 100W BTL Out TPA3116 Mono Channel Digital Power Audio Amplifier Board - US$7.17

These are the stereo boards:
TPA3116 Dual Channel 50Wx2 Digital Amplifier Board - US$10.58
TPA3116 PBTL DC 11-26V Dual Channel 2x100W Digital Power Amplifier Board 2 Chips - US$12.25

 

[FauxFrench]

Hi flo777,

If you use 2K2 at the potentiometer output, you need not remove any SMD resistors.

That you have a potentiometer at the TPA3116 board is actually an advantage. The output signal amplitude from your pre-amp seems high and you will find it better when the TPA3116 board input sensitivity is reduced (by the potentiometer).

Myself, I use a pre-amp with a TPA6120a headphone chip at the output and I regularly use a 20dB resistive damping element between the pre-amp and the input of the power amplifier. Too much gain is a frequent problem.
I have the second mono-board you show and the first stereo-board.
If you end up with the same mounting faults as I had on my mono-board, you will need to move SMD resistors around.
As I recall, the stereo-board has by default a quite high gain (and some hiss).

Buying another board will not solve your fear of removing SMD resistor(s).

NXP generally recommends 22uH/680nF for 8 Ohm, 15uH/1uF for 6 Ohm and 10uH/1.5uF for 4 Ohm. You can use 15uH/1uF for most. 33uH/470nF will do fine with 8 Ohm but the chokes will saturate at a lower output current. It is not an exact science.

 

[flo777]

Hi FauxFrench,
Thanks for this information.

I'm using 4 ohm fullrange speakers nearfield. I don't need a lot of power, but would like to get a board with good bass output for 4 ohm speakers.

If I get the first stereo board (which you also have), then I could remove the 3-pin audio input and add the 2k2 resistors there. It seems easier than adding the resistors at the output of the potentiometer.

Alternatively, I was also looking at two ta2024 boards here
ta2024 - Parts Express Ships Fast and Ships Free.

I found the specs for the first one (black) and the gain is 20 db, input impedance 22 kohm and input sensitivity at 4 ohm/15W/1 khz is 748 mV.
I think that these specs are suitable for an active preamplifier?

 

[jemraid]

Hello Flo,

This TPA3116D2 XH-M590 board is the one that FF recommends and I use as well.

My speakers are Frugel Horn Mk3's with 4 Ohm Mark Audio CHP-70's. The board will drive them very well indeed, so much so that I can feel (for the first time) the bass in my chest cavity.

It's an amazing amp and worth buying an Antex SX25 soldering iron for removal of the 753 resistor.

Cheers - Jem

 

[FauxFrench]

Hi flo777,
Adding two 2K2 resistors on the rear side of the board, below the potentiometer is a simple and quick operation. If you do not have the potentiometer, you loose the possibility to form a variable voltage divider used to adjust the input sensitivity. The first stereo-board for purchase seems not much better than the one you already have.

I have the TA2024 board with the two red capacitors. It sounds fine with good vocals. When it comes to good firm bass, TPA3116 is superior to TA2024, in particular in 4 Ohm.
TA2024 has refinement in the mid-range, TPA3116 more "beef" in the bass and still good mid-range.
Unless age has caused you to have problems finding your reading glasses, you better take the jump into simple SMD modifications. Yes, the SMD parts look intimidatingly small but it is easier than it seems. Adjusting gain is doable.