Ok as the title says I have the red Sanwu tda7498E version from Amazon. I soldered the 4 jumpers together on the bottom of the PCB and input a signal into the LEFT RCA only from my low pass filter preamp. I also put both dip switches that control gain to the max setting of 36db and the output level is approximately half of what I get in btl mode! I usually use this amp in btl with (2) 4-8ohm 2-way bookshelf speakers and it gets very loud. I measured 26vac average clean with my oscilloscope while using a 34v 10a PSU. While the amp is in PBTL I'm using a 4ohm GRS 8" high excursion sub from parts express. What's going on, am I doing something wrong?
I copied and pasted this from the datasheet. Just want to make sure I am understanding this right because I don't want to let any smoke out today! They are saying to only use the LEFT signal input because the right is grounded when connecting the jumpers on the bottom of the board. Then use BOTH left and right speaker outputs and hook them both to my subwoofer? If thats true then maybe that will explain the lack of power. I tried my sub on one channel yesterday while in stereo mode and left the right channel disconnected. I only did it briefly because I heard its not good to only use 1 channel of a 2 channel class d amp but also have heard people say its ok. The sub was much louder with the amp in BTL VS PBTL.
Stereo and mono BTL operation selection using the MODE pin
The TDA7498E can be used in stereo applications or mono BTL applications. Connecting the MODE pin to the
VDDS pin configures the device in mono BTL. The output of the two channels can be paralleled. When the MODE
pin is connected to ground or floating (pulled down internally) the device works as a stereo amplifier.
Stereo and mono BTL operation selection using the MODE pin
The TDA7498E can be used in stereo applications or mono BTL applications. Connecting the MODE pin to the
VDDS pin configures the device in mono BTL. The output of the two channels can be paralleled. When the MODE
pin is connected to ground or floating (pulled down internally) the device works as a stereo amplifier.
That's the normal behavior and to be expected. BTL gives you the higher amplitude, PBTL the high current - which you can only use with very low impedance (3 Ohm). The power increase is less than 2 dB, so not really worth it. I've tried two TDA7498E amps myself, was quite disappointed sound and power wise and moved on.
Ok it's so strange to me and seemed like something was wrong. It was definitely way more than a 2db difference because in PBTL I had the max gain setting which is around 36db I think and could barely get any volume out of it. In btl I use the lowest 20db gain and get significantly more volume. Does that mean I'm experiencing at least a 16db difference or is that not how it works? All I know is that double the perceived volume is 3db and I'd say it sounded like a 4db difference while using 16db increase in gain.
I wanted to add that about 6 months ago when I first finished building my enclosure I ran 2 of these modules in PBTL one for each channel and powered my pair of 8" 2 way speakers. They worked excellent for that and gave me a noticeable increase in output which I'm guessing was due to the extra current from PBTL. Maybe they just don't work well for low frequencies and better with full signal. I have my DSP set to play 32hz-100hz to my sub.
I wanted to add that about 6 months ago when I first finished building my enclosure I ran 2 of these modules in PBTL one for each channel and powered my pair of 8" 2 way speakers. They worked excellent for that and gave me a noticeable increase in output which I'm guessing was due to the extra current from PBTL. Maybe they just don't work well for low frequencies and better with full signal. I have my DSP set to play 32hz-100hz to my sub.
Oh ok thanks for clarifying that. It's been a struggle for me to retain new information and then there's a lot of wrong information out there too. I wanted a tpa3255 that was capable of mono or stero but the only one I came across was the Wuzhi amp and I had a nightmare with the one I bought! I wonder why more of these amp modules don't have a way to switch to mono seeing as it seems pretty strait forward and easy. The Wuzhi had issues from day 1 where the audio would cut off and on repeatedly everyday 2 seconds or so like a protection was tripping. I actually found how to contact them directly from their Chinese website. They knew about the issues and actually emailed me a document they made in English with nice zoomed in photos of a fix. It was removing the capacitor from the bootstrap pin of the tpa3255. I have no idea what the actual problem was as this was obviously a band aid fix that worked briefly before the amp died altogether. It did work and sound well before just mysteriously loosing output one day.