I have set the gain 32dB on same board and I admit the sound quality is the best among all the TPA 3116 , TPA 3118 , TDA 7498 boards I have tried so far (I have tried a dozen of amps). I am looking forward to change input capacitors on these in hope of further improvement. Doesn't 5.6uF should be the right values for this modded board (Gain 32db) as input caps ?I am planning to use Polypropylene Caps.
With gain set to 32dB input resistance is 15kOhms. A 5.6uF coupling cap results in a 3dB corner frequency of 1,89Hz. Pretty enough imho. Further increasing capacitance will increase any popp on power up/down without contributing to sound quality. Instead of fiddling with "hi-end" caps it may be a better idea to match their capacitance. I found out this can reduce popp considerably.
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You can try soldering the resistor directly to pin 8 & 9. Though that will make impossible to mount heatsink on the chip. You can try scrapping of the trace which leads to those two pads and solder the resistor across those two points though.
I have indeed tried scrapping but I did not find the upper traces for some reason, I scrapped and scrapped and only found the bottom one. Which direction should I be aiming for? top left right?
Thank you so much for your advice. I've managed to scrape the traces of Yellow and Red points (they do have continuity) and solder two copper wires from the points to a 5.6k resistor. When the resistor is in circuit, it measures 0 Ohms, and during operation it measures 0 volts, and also measuring the two points without the resistor measures 0 volts. Is that normal?
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The Resistor used in this position is Gain sensing resistor so I feel its normal to have 0 potential drop across it. If the amp is working okay now then you can simply solder a 1/8 watt 5.6 k resistor directly to those spots (Red & Yellow). Will be much neater that way.
Funny enough the amp worked fine with no gain resistor in place, couldnt hear a difference, how could it be?
Also thank you for your efforts!
Thank you for your efforts, I’ve actually just got a shui yang tpa3255, plan on putting it with a Classix II build!
Great. I myself is tuning my Overnight Sensation TM since last one year in combination to the TPA 3116 board that i have finally settled on. None of the better TPA 3255 boards are available in my country so am eyeing on Aiyima A07 unless Allo releases one anytime soon.
I think the gain of 10 is actually 20db at the voltage amplification section isn't it? I was also confused by this because I was thinking about power gain but after researching cyperpit's schematic that showed 20db he is correct.
http://www.sengpielaudio.com/calculator-gainloss.htm
I think your gain is actually negative rather than +3b because the input preamp is inverting and that will make it G = -(.950/2) I think you might want something more like a 3.3k resistor with that method then it would probably give your desired gain of 3. That would be a nice balance.
I also modified the gain on my XH-M543 board by changing R12 and R16 to 10k to make it a 6db gain. I then changed the main gain to 20db. I chose 6db to add with the 20db because I plan to change my XH-M542 boards to be a gain of 26db which is close to the normal 29db I see in home theater given that is my intended application (an outside patio 5.0 surround system). Having the preamp 6db gain followed by 20db makes the 543 a much better match for the 542 mono board.
I changed the input resistor rather than the feedback resistor because the 2k input is a bit low for the 1uf capacitor on the board. I also considered adding a second surface mount cap in parallel with the input coupling cap but I got a good frequency response once I increase the input resistance.
Strangely I also had a board with a bad tl074 opamp (or I somehow shorted it out while modifying it) which took a while to debug and made the process quite frustrating.... Fortunately or unfortunately I had already done some damage to another 435 board so I just stole the opamp from that one (surface mount soldering chips is actually easier than resistors because they don't move as much).
On the xh-m542 board I changed the two resistors to set the gain to 26db. The overall changes to the 543 are about the same given that I only had to solder one resistor back to get the 20db gain and then had to change the two preamp input resistors on the 543 board.
I think the xh-m542 mono boards are better to work with. They have no preamp so it just makes for less to deal with.
-Rich
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Decided to try the ZK-502H (one particular reason is that is seems to have the output snubbers in place - did not check, just by the count of the parts near the output inductors)
On bluetooth or wired (on aux) to the phone works perfect. But wired to the PC, it has noise with both internal or external sound card. Running on old laptop brick, 19V, I think it's a Delta power supply. Will try another power supply, this one is grounded and maybe that's an issue since the PC ground is wired to GND
Potentiometer is not to be used at very low levels (cheap one, nothing unexpected)
Not sure about the power switch if played at full power, also output inductors look small-ish
Not sure about the usb power claiming to work as both host (insert stick) and device (connect as soundcard to pc) - don't have an usb-a to usb-a cable in the drawer
Bluetooth is unfortunately SBC only, no sign of any decent audio codec
On bluetooth or wired (on aux) to the phone works perfect. But wired to the PC, it has noise with both internal or external sound card. Running on old laptop brick, 19V, I think it's a Delta power supply. Will try another power supply, this one is grounded and maybe that's an issue since the PC ground is wired to GND
Potentiometer is not to be used at very low levels (cheap one, nothing unexpected)
Not sure about the power switch if played at full power, also output inductors look small-ish
Not sure about the usb power claiming to work as both host (insert stick) and device (connect as soundcard to pc) - don't have an usb-a to usb-a cable in the drawer
Bluetooth is unfortunately SBC only, no sign of any decent audio codec
Hello X
Pls. How did you manege to get proper 19V socket on the amp case? I own a YJ V2 board playing very sactirfying till now but the female socket, from a PC board, is getting poor contact. I´m using a generic 19V PC charger from Acer.
TIA
Something like this works well. You have to be careful about the center pin diameter. Sometimes too large or too small.
https://a.co/d/bZhmOQc
https://a.co/d/bZhmOQc
I tried one of these and a lot of features for $5. Not bad for a DIY kitchen radio.