stereo to mono problem

[SentinelAeon]

Hello, i am trying to convert stereo into mono on my bluetooth amplifier/receiver, since i am using a woofer + tweeter setup. I included a picture of how i solder the pins together. Right now the pot is up to a maximum, which means the pins are effectively shorted together. I know ur supposed to use a resistor but i am looking for a max SPL, even if the amplifier dies after a few months. The amplifier chip itself is TPA3116D2. The amplifier board is ZK-502C hifi.

Problem 1: Even when the pins are shorted together, i get on average about 4-5dB less SPL than i would otherwise and i dont understand why since i am not using any resistors and pot doesnt offer any resistance.

Problem 2: When pins are shorted together, the speaker amplifier will shut down and restart if the pot is over 80% volume. This happens even if the speakers are not connected ! I am really wondering why.

Question: Is there any way to get around this since i need every single last dB i can get, so i cant lose even 1dB, let alone 3dB.

 

[eTech]

Maybe this will help (I hope).

The objective is to convert the amplifier from "stereo mode" to "mono mode" so that it can provide 100W output power to ONE output (not both..because it can't). These changes rely on the TI datasheet schematic reflecting your circuit board design which MAY NOT be the case.

The changes below you do at your own risk! as there is the potential for damage to occur that renders it inoperable.

Output:
1. Bridge the IC amp outputs as shown in green. The red "X" means to cut trace.
2. Afterwards, only use the Right channel speaker terminals. Connect this to the speaker crossover network input. Then connect the woofer and tweeter to the appropriate crossover network outputs.

Input:
3. Connect INPL and INNL to ground as shown in green.
4. Afterwards, only use the Right input channel. Connect the external R/L input signal combiner to this input channel.

BTW-

It would have been a lot easier if you had just bought the 100W "Mono" version of this amplifier.

 

[rjenkinsgb]

The objective is to convert the amplifier from "stereo mode" to "mono mode" so that it can provide 100W output power to ONE output (not both..because it can't).

My version keeps both sets of filter components and parallels the outputs at the screw terminals, rather than (or as well as) at the IC.

I very much doubt that the output filter components can handle double the current, as there would be if you only use one pair of output terminals.

Paralleling at the screw terminals [in the same fundamental configuration] puts two sets of filters in parallel, so no increase in current per inductor.

 

[eTech]

I very much doubt that the output filter components can handle double the current, as there would be if you only use one pair of output terminals.

Something I overlooked and agree.

Paralleling at the screw terminals [in the same fundamental configuration] puts two sets of filters in parallel, so no increase in current per inductor.

However, connecting jumpers internally without cutting traces will short circuit the outputs.

 

[Nigel Goodwin]

Something I overlooked and agree.


However, connecting jumpers internally without cutting traces will short circuit the outputs.

I would have said not - whereas your modifications would result in both amplifiers being shorted out (by the green wires).

 

[eTech]

I would have said not - whereas your modifications would result in both amplifiers being shorted out (by the green wires).

I think you need to review my mods again...

 

[SentinelAeon]

eTech I agree it would be easier to buy a mono amp with 100W but thats not easy. The one i am using is 7$ and it sounds fantastic + has bluetooth receiver on it. I bought the one in the attachment also and it sounds like a complete crap. And its the same chip, so i dont know how did they manage to make it so bad. I have 7 pieces left and they are so bad i might aswell throw them in the garbage. I tried a few others and either they sound very bad, or their price is like 4 times of the one i am using. And since i now know how to mod it easily, i will stick to it until i find a better one. I wish this company, the black one, made the same amp with bluetooth but with mono.

 

[audioguru]

The 4 ohms woofer, 4 ohms tweeter and a crossover network for them does not make a 2 ohms speaker system.
If it did then millions of home sound systems would have their amplifier overloaded, especially when the speakers are three-way. A 2 ohm speaker system uses two similar 4 ohm speakers playing everything at the same time.

it is much better to use one channel playing the woofer and use the other channel playing the tweeter so that when the woofer channel is clipping then the tweeter channel dos not play the woofer channel's distortion harmonics, resulting in louder sounds which is wanted.

But the TPA3116 stereo amplifier produces 50W to 65W into 4 ohms and the little 4 ohms woofer has a maximum allowed continuous power rating of only 40W.

 

[Nigel Goodwin]

I think you need to review my mods again...

Direct shorts across the outputs of each bridged amplifier?.

It's already two pairs of bridged amplifiers, you can't bridge them again.

 

[rjenkinsgb]

Direct shorts across the outputs of each bridged amplifier?.

That part is correct - when the IC is switched to "mono" by directly grounding the left inputs, it reconfigures so both right channel outputs become one terminal and both left channel the other.

However the datasheet only shows the principle, not details of the output filtering, which then may also be required to handle twice the current - hence my advice to parallel at the module screw terminals, so both sets of filter components run in tandem.

 

[SentinelAeon]

Like i stated over and over (and over) again, i am making different speakers and i clearly stated many times that this time i am making a big speaker, woofer is 50W RMS/100W MAX, tweeter is 30W RMS/60W MAX. Single 50W output will simply not do it. The problem with leaving the amplifier as it is, is that in stereo parts the thing sounds strange plus the overall quality is worse than in mono. If i just do the mixing of the channels by bridging + 2 resistors, i get sound quality, proper mono but lose some SPL. But i still have 2x50W at my disposal. If i change amplifier into mono mode then i am stuck with a single 50W unless i use 2 ohm speaker. I added datasheet of both speakers in the attachment.

Btw i decided i will not do any crossover on my woofer and only do a 1st or 2nd on tweeter to protect it. I dont care if the woofer screams at high frequency or if the tweeter dies after 3 months. Tweeter is like 10$ a piece, i would pay more for proper coils and fancy caps.
As for my little woofer, its been running alone on 1 channel with no crossover, killawatt is reading 50-65W going into it. Its been working for almost 3 years being run at 100% volume often.

I really failed to explain well the enviroment in which my speakers are used. Its outside place, really loud, alcohol, talking, jelling, etc. I dont have a good video of mine to show but i will just show some really really old video i remember being online. Its a lot different than how we party, music is mostly different, people are different, environment is different, but things that are similar is loud music, intoxicated people, loud talking/screaming and people who just want music as loud as possible and with good bass and dont care about anything else. They really dont care about which order crossover is on which speaker and how the frequencies combine or reduce at certain height. Now, when i want to do a good sounding speaker, i will say it outright and i will do a proper crossover. But when i say i want SPL and bass, i want SPL and bass.

 

[audioguru]

"The problem with leaving the amplifier as it is, is that in stereo parts the thing sounds strange plus the overall quality is worse than in mono."
1) Did you use two identical speakers in stereo? Was one connected with backwards polarity (then the sound will be strange).
2) Was the amplifier clipping? Then the sound will be bad.
3) Were the speakers over-powered and causing their voice-coil to slam into the magnet structure (then the sound will be strange).

Your tweeter is 2.5dB louder than the woofer so it needs to be attenuated which will make it last much longer.
Without a lowpass crossover filter on the woofer then the added highs will be another +3dB too loud.

The video has no bass, no mids and no highs. Just drums and noises. Is that what you want?
You say you want only loudness, not good clear sound.

 

[rjenkinsgb]

Are you aware of the enclosure size to get good low frequency response from that speaker?
It's not in the datasheet, but some retailers include it:

FEATURES

• Vented reinforced plastic chassis
• Proprietary cone material with natural fibers made in-house
• Soft low damping rubber surround for improved transient response
• Large spider for improved linearity
• Optimized motor system
• Vented coil former for low compression
• Non-resonant long life lead wires

Some possible box alignments:

Sealed box of 0.4 to 0.6 cubic foot for a 3dB down of about 80Hz

Vented box of 0.5 cubic foot with 2″ Ø vent by 8″ long for f3 of 65Hz
Vented box of 0.75 cubic foot with 2″ Ø vent by 5″ long for f3 of 55Hz
Vented box of 1.0 cubic foot with 2″ Ø vent by 4″ long for f3 of 50Hz
Vented box of 1.25 cubic feet with 2″ Ø vent by 3.5″ long for f3 of 47Hz

One cubic foot is around 28 litres.

 

[SentinelAeon]

audioguru Ofcourse i didnt use 2 identical speakers in stereo, you know i am doing woofer + tweeter setup always. I tested sound quality at room volume and mono was better sound quality. As for the recording, it is an old and bad recording, in reality you can be sure the bass was good and it was loud. And i was mostly talking about environment, so when you talk about those +3dB or -3dB at certain frequencies, you can be sure no one there cares as long as its loud and bassy.

rjenkinsgb Yea, i know how to calculate the enclosure so there wont be any problems.

 

[audioguru]

1)Then you had the amplifier in stereo but you had the woofer on one channel and had the tweeter on the other channel?
2) Did the woofer and tweeter have a 2nd-order crossover network with the tweeter having reverse phase?
3) Was the tweeter attenuated to match the sensitivity of the woofer?

Of course mono sounds better than the woofer on one stereo channel and the tweeter on the other stereo channel. They both should play mono on their separate channels.

 

[SentinelAeon]

1) Before, i had stereo with woofer on 1 channel and tweeter on another. Now i use mono (bridging left and right at receiver and add 2 capacitors to protect them).

2) No and No. I am not crossing woofer probably ever, because i dont notice anything wrong with it and until i hear something that bothers me, i dont care. Tweeter had first order and it worked for a long time without problems. I might do second order though materials cost me more than a new tweeter that lasted for 3 years. As for the reverse polarity, i didnt know i have to do that when i have 2 separate mono channels ? Remember, i will not be using the amplifier in mono mode as i thought i would. So its back to 2x50W channels, i just mixed the stereo into mono at receiver, using 2 resistors to protect the left and right channels from eachother.

3) No it wasn't. Why would i be reducing the tweeter SPL, i need SPL, every 0.0001dB of it. Dont know how many times i have to say that i am about SPL and bass with this speaker, not quality. Its like im trying to build a car for drag racing and you keep asking me if i got enough space in the back for 2 kids and a shopping bag. It doesn't make any sense.

 

[audioguru]

Sentinel, everybody except you want good clear sounds. They attenuate the tweeter to match the sensitivity of the woofer, use a proper CL and LC second-order crossover network with the tweeter wiring reversed to fix the phase and they never drive the amplifier into clipping.

You are not using a second-order crossover network then you should not reverse the wiring for the tweeter. The phase and any phase problem are exactly the same in stereo or in mono.

Using separate mono channels then now you will have up to 65W per channel with fairly low distortion when powered from a fully charged 6-cells Lithium battery. You can turn up the volume to maybe 80W in the woofer channel without the woofer channel clipping distortion from being heard in the tweeter channel.

You mention adding resistors and capacitors but you do not post a schematic of their values and locations.

 

[christinescoms]

Hello, i am trying to convert stereo into mono on my bluetooth amplifier/receiver, since i am using a woofer + tweeter setup. I included a picture of how i solder the pins together. Right now the pot is up to a maximum, which means the pins are effectively shorted together. I know ur supposed to use a resistor but i am looking for a max SPL, even if the amplifier dies after a few months. The amplifier chip itself is TPA3116D2. The amplifier board is ZK-502C hifi.

Problem 1: Even when the pins are shorted together, i get on average about 4-5dB less SPL than i would otherwise and i dont understand why since i am not using any resistors and pot doesnt offer any resistance.

Problem 2: When pins are shorted together, the speaker amplifier will shut down and restart if the pot is over 80% volume. This happens even if the speakers are not connected ! I am really wondering why.

Question: Is there any way to get around this since i need every single last dB i can get, so i cant lose even 1dB, let alone 3dB. floor grinder Los Angeles

Hello. I also need help with the same project

 

[Tony Stewart]

When I had a 100W stereo Bogan tube amp and 12" Philips full range speakers in massive cabinets 30 Hz to 20kHz. It was loud enough to vibrate the living room and anything hanging on the wall. Even a transistor radio with a 9V battery was loud enough in the garage. I see you prefer > 20% THD.

 

[SentinelAeon]

Just wanted to say i put the project on hold for now, not enough time, no way to get needed materials, will use my usual speaker which should be ok since its a privat barbeque. But it would be cool if we keep the thread open to throw around some ideas.

christinescoms: feel free to post a question

audioguru: I know, maybe i was to harsh cause i was under extreme time pressure. I want quality ofcourse, but SPL and bass are first and second, quality is third. The problem is also that i simply fail to notice the difference a lot of the time. And while my hearing at lower frequencies is perfect (i have perfect pitch xD), i have very bad hearing of higher frequencies, above 10.000Hz i barely hear anything. Was like this ever since i was a child. Thats why in the beginning i didnt understand why i even need a tweeter.

To answer my stereo - mono question i posted a schematic i drew a while ago for someone else. Where there is R written, thats a resistor. Value depends. Remember even without resistor i lose 3-5dB and i can hear that a LOT (3dB is about 24% SPL, very clearly heard by me). I tried 10 ohms which is to low to protect the channels. I tried 1000 ohms which might be ok, and someone here said i might even try 100 ohms cause the bluetooth receiver might be for the headphones.

You said something about me being able to get 80W into the woofer when i use 2 separate mono channels. But wouldn't that blow the amplifier ? I thought amplifier is able to suply just 50W per channel.


A bonus question about the boost. We talked before that i can replace 2 resistors on the amplifier board to get a +4dB boost which is very welcome. But would that mean i would also use double the power ? Wouldnt that just blow the amp ? And another funny thing. When i mix stereo into mono i lose 3-5dB, dB meter says that and i can very clearly notice the difference. But there doesn't seem to be any difference in power consumption. Its still like 65W combined. Shouldn't it be like 35W if its 3-5dB more quiet ? Its like i am using the same power but getting 3-5dB less out, which doesn't make any sense.

 

[Tony Stewart]

I hope you are using EXACTLY 21V power Supply with sufficient power into 2 Ohms , if you want 50+50W

TPA3116D2 15-W, 30-W, 50-W Filter-Free Class-D Stereo Amplifier Family With AM Avoidance
• Supports Multiple Output Configurations
– 2 × 50 W Into a 4-Ω BTL Load at 21 V (TPA3116D2)


Don't confuse gain with max Power . You can control input levels, gain and DC voltage level and speaker impedance to obtain optimal power levels. The dissipation of max power implies the chip is operating at maximum temperature levels and may require forced air cooling.

7.3.1 Gain Setting and Master and Slave

The gain of the TPA31xxD2 family is set by the voltage divider connected to the GAIN/SLV control pin. Master or Slave mode is also controlled by the same pin.

An internal ADC is used to detect the 8 input states. The first four stages sets the GAIN in Master mode in gains of 20, 26, 32, 36 dB respectively, while the next four stages sets the GAIN in Slave mode in gains of 20, 26, 32, 36 dB respectively. The gain setting is latched during power-up and cannot be changed while device is powered.

See Table 1 which lists the recommended resistor values and the state and gain:
.
In datasheet

https://www.ti.com/lit/gpn/tpa3116d2