Orderd a 2-chip TPA3116... Mistake?

[sguyader]

Hi,

I'm new here, I hope it's fine to create this new topic. Yesterday I ordered a 2 TPA3116 board from Amazon, one of those XH-M190 v3. But I think I did a mistake. What I want is to use the board as an acoustic guitar amp, to power a single 8 Ohms speaker cab. The power source is a Toshiba 19V 4.7A laptop unit.

In my mind I was ordering a mono board, but of course it is not. Since it's a 2-chip board, each chip is set to PBTL mode I think, so my question is: is there a way to bridge both chips together to drive my single cab? If so, how can I do it?

Thanks for reading.

-Sebastien

 

[Jerms]

The two main problems are that the TPA3116s are already bridged. And that the "100watts" output the board may support is into 4ohm or 2ohm load.

I don't know that I'd want to link the outputs to power one speaker from both chips. ISTR TI say not to do it.

For a guitar, you may be better off with one of the TDA7498 "subwoofer" amps. Though they typically need more like 30V DC drive.

 

[sguyader]

Thanks Jerms. That's what I thought about bridging, but I needed advice.

In fact it's for an acoustic guitar, not an electric guitar. It needs a flatter frequency response than what a typical electric guitar needs. That's why acoustic guitars sound good plugged directly in PA systems but suck in an electric guitar amp.

I have another idea. I have an old active (biamped) studio monitor who's amp is dead. It has 2 speakers, a 6.5" 75W woofer and a 1" 25W tweeter, both 4 ohms impedance. Would it be possible remove the original dead amp, and put the dual TPA3116 board in it to drive each speaker independently? Maybe adding a passive high pass filter before the tweeter?

 

[FauxFrench]

I wouldn't see it as a mistake if you only paid the modest price it is sold for. It is just not optimal for your needs and may be used for another stereo purpose instead.

Paralleling of two separate TPA3116D2 IC's is most likely a very poor idea because paralleling of outputs require fully synchronous operation of the outputs. Fully synchronous operation is possible within a single TPA3116D2 IC, if set up correctly, as the output switches then use the same drive circuit. With two different TPA3116D2 ICs, the drive circuits are different and even a moderate deviation from synchronization may cause some really nasty "shoot-through" currents from the supply line and straight to ground.

Using your double TPA3116D2 board to drive the 6.5 Inch speaker is fine but the 1 Inch tweeter perhaps a poor idea. Class D amplifiers rely on the speaker load to damp the output filter resonance and your tweeter will need a series (high-pass) capacitor to filter away low frequencies. For the frequency range with most power the tweeter circuit will not damp the output filter much.

Turn your double chip board into a stereo amplifier for your wife or kids and buy a mono board for yourself.

DC 12V 24V TPA3116 Mono Channel Digital Power Audio Amplifier Board BTL Out 100W New Arrival Hot Selling-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Hot 2017 High quality TDA7492 50W2/8Ohms BTL 100W/4Ohms High Power Digital Amplifier Board Logic Board-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
DC 12V 24V TPA3118 BTL 60W Mono Digital Audio Power Amplifier Board Amp Module-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
DC 12V 24V TPA3116D2 BTL 150W xBS Bass Car Digital Audio Power Amplifier Board-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group

 

[sguyader]

Thanks @FauxFrench. Though I don't understand much about the technical things.
So if I were to to use the 2-chip board to power biamp the speaker cabinet, using just a capacitor filter for the tweeter, what would be a concrete consequences? Is there a risk of damaging the tweeter or the chip which powers this channel? Or would there just be a negative consequence with regards to the sound quality, and if so, of what kind?
Just for you to know, this amp would be used for me as a stage monitor for acoustic guitar. I need a relatively flat frequency response, but I don't need de purest hifi sound quality. I don't need a stereo amp, I already have a NAD amp and Wharfedale speakers for regular music listening at home.

 

[FauxFrench]

The problem of no loading is explained by ddapkus in another thread concerning the 3116D2:
TPA3116D2 Amp

In short, you risk the resonance circuit with the power-chokes generates voltage spikes that may destroy the chip.
For your use as a guitar amplifier, the best would be to get a second speaker unit and let each channel drive a separate (full-tone) speaker unit. A 6.5 Inch speaker unit should follow well up through the mid-range. Then, each amplifier channel is well loaded in the full frequency range.

In theory you could use an electronic filter before the tweeter such that one amplifier channel is connected straight to the tweeter. But, such a powerful amplifier connected directly to a tweeter may damage the tweeter due to excessive input power.

The last, trivial option is to use only one amplifier channel for the loudspeaker you already have and let the other channel run idle, with a dummy load at the output.

 

[sguyader]

In theory you could use an electronic filter before the tweeter such that one amplifier channel is connected straight to the tweeter. But, such a powerful amplifier connected directly to a tweeter may damage the tweeter due to excessive input power.

Of course it wasn't my intention to connect one of the PBTL channels directly to the tweeter, I was thinking of adding a simple high-pass filter (a 10-16uF capacitor in series with the tweeter). With the low filtered out, would the 25W 4ohms tweeter still be at risk?

The last, trivial option is to use only one amplifier channel for the loudspeaker you already have and let the other channel run idle, with a dummy load at the output.

I thought about that possibility, using only the 6.5" driver. But I don't know of its frequency response will extend enough into the highs to reproduce the tone of the acoustic guitar.

By the way, what is this board you linked in a previous post: DC 12V 24V TPA3116D2 BTL 150W xBS Bass Car Digital Audio Power Amplifier Board-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group? Is there a bypassable low-pass filter on it, to either use it as a subwoofer amp or full range amp?

 

[Nenola]

By the way, what is this board you linked in a previous post: DC 12V 24V TPA3116D2 BTL 150W xBS Bass Car Digital Audio Power Amplifier Board-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group? Is there a bypassable low-pass filter on it, to either use it as a subwoofer amp or full range amp?

Looks to me that it has a switch for the low pass/full range. The cut-off frequency would be nice to know, like in every other chinese amp with subwoofer channel

 

[FauxFrench]

Of course it wasn't my intention to connect one of the PBTL channels directly to the tweeter, I was thinking of adding a simple high-pass filter (a 10-16uF capacitor in series with the tweeter). With the low filtered out, would the 25W 4ohms tweeter still be at risk?

In case of such a high-pass capacitor in series with the tweeter my worry is for the amplifier because the impedance of the tweeter will be much above 8 Ohm at some 200-500Hz and not resistive. Then, the filter will not be damped as it should and suggested by TI.

I thought about that possibility, using only the 6.5" driver. But I don't know of its frequency response will extend enough into the highs to reproduce the tone of the acoustic guitar.

You are the best judge of that.

By the way, what is this board you linked in a previous post: DC 12V 24V TPA3116D2 BTL 150W xBS Bass Car Digital Audio Power Amplifier Board-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group? Is there a bypassable low-pass filter on it, to either use it as a subwoofer amp or full range amp?

I hadn't noticed that detail. Actually, there is a switch for "LOW/FULL" that clearly hints it may be used as sub-woofer or full range amplifier depending on the needs. Most likely with a by-passable low-pass filter.

 

[Jerms]

Actually, "guitar amp and speaker". If you don't need it to be very loud, try a TPA3118 mono board.

 

[sguyader]

Thanks everybody. I've been able to cancel my order and get a refund.
Now I have to think about what to do with my speaker. I still want it to be small and transportable (one speaker with a mid-range drive and a tweeter) yet powerful enough so Incan hear myself on stage (it will be a stage monitor for acoustic misc, but with drummer)

 

[Eva]

Learning requires mistake.

Audibility of portable gear at stage or street requires some power. Maximum power output is dictated by supply voltage and load impedance. Advertisements can result misleading if the root rule is not known.

BTL power ceiling equals V^/(2*r) where "V" is supply voltage and "r" is load impedance. For a 19V (single ended) supply and 4ohm load power ceiling is 45W.

More power can be obtained by boosting the 19V from the power adapter, or adding a 2nd power adapter in series. 38V is about the limit for TDA7498, for 100W/8r, per channel (in active filter 2-way operation, "4 ohm nominal" speaker driver impedance plot may be high enough for being driven by TDA7498 without shutdown or damage).

Example boost (step-up) DC-DC regulator board from ebay:
DC-DC 6-35V to 6-55V 10A 200W Boost Converter Charger Step-up Power Module | eBay
That kind of boost regulators, combined with some pass/protect diodes, and switches, and over-discharge protection circuit, allow wall-plug and battery operation.

The other issue is: what to do with 2 channels? Driving a 2-way system is a technically superior approach, which also implies technically superior implementation. There are 2 requirements to fulfill.

1- A reliable (not leaking LF into HF due to clipping) and accurate (tweaked for uniform on-axis or off-axis response) frequency division circuit, taking signal from guitar and conditioning it for amplifier channels.

2- Protection, including a gain reduction circuit based in clipping indication from amplifier (problem: if the chip does not include clip indication, another circuit is required to detect clipping), and a DC protection system for both channels (like pre-made boards, but not just pop-suppression delay boards). I don't recommend a capacitor in series with the tweeter as a protection, unless phase shift is accounted for. Simple 2-way does not sound good with too many "filter orders" in tweeter response, due to phase incoherence.

 

[sguyader]

Learning requires mistake.

Audibility of portable gear at stage or street requires some power. Maximum power output is dictated by supply voltage and load impedance. Advertisements can result misleading if the root rule is not known.

BTL power ceiling equals V^/(2*r) where "V" is supply voltage and "r" is load impedance. For a 19V (single ended) supply and 4ohm load power ceiling is 45W.

More power can be obtained by boosting the 19V from the power adapter, or adding a 2nd power adapter in series. 38V is about the limit for TDA7498, for 100W/8r, per channel (in active filter 2-way operation, "4 ohm nominal" speaker driver impedance plot may be high enough for being driven by TDA7498 without shutdown or damage).

Example boost (step-up) DC-DC regulator board from ebay:
DC-DC 6-35V to 6-55V 10A 200W Boost Converter Charger Step-up Power Module | eBay
That kind of boost regulators, combined with some pass/protect diodes, and switches, and over-discharge protection circuit, allow wall-plug and battery operation.

Thanks Eva. What do you think of this one: 6A Boost Converter DC-DC 10-32V to 12-35V Step Up

The other issue is: what to do with 2 channels? Driving a 2-way system is a technically superior approach, which also implies technically superior implementation. There are 2 requirements to fulfill.

1- A reliable (not leaking LF into HF due to clipping) and accurate (tweaked for uniform on-axis or off-axis response) frequency division circuit, taking signal from guitar and conditioning it for amplifier channels.

2- Protection, including a gain reduction circuit based in clipping indication from amplifier (problem: if the chip does not include clip indication, another circuit is required to detect clipping), and a DC protection system for both channels (like pre-made boards, but not just pop-suppression delay boards). I don't recommend a capacitor in series with the tweeter as a protection, unless phase shift is accounted for. Simple 2-way does not sound good with too many "filter orders" in tweeter response, due to phase incoherence.

In fact I was thinking to try one of the boxed amps (Breeze/Nobsound) which include an NE5532-based preamp module (Nobsound Mini Dual TPA3116 Digital Power Amplifier HiFi Stereo Audio Amp 2.0 Channel 100W×2 DIY with NE5532 Pre-level OP Amp).
I just bought a pair of used Pioneer bookshelf 2-way speakers, which I think are light enough to be portable. This way I could connect each speaker channel to one speaker, and be done with it. For just 20€ the speakers, if I blow them when testing it's won't be a great loss.

 

[Eva]

The 2 modules you propose are suitable for 24V peak output and 4 ohm speakers (72W/ch). The solution I proposed was for 39V peak output on 8 ohm speakers (95W/ch).

Note that, for stereo operation, at low frequencies, peak supply current as high as 2*24V/4r=12A or 2*39V/8r=9.75A can be demanded. This is the main criteria for sizing the boost converter. The 6A unit covers only 50% requirement, acceptable for, say, >100hz, operation (considering the little bulk capacitor bank included in the dual TPA3116 module).

EDIT: Input impedance of the amplifier module is not listed. NE5532 is an op-amp intended for low signal impedances, input impedance could be a few kohm only. Circuit modification could be needed for optimum musical instrument use.

 

[sguyader]

The guitar will go through an effect board which gives a 2 kOhms output impedance (-10 dBU line out). It is said to have unity gain. Is that enoughj to go directly into a TPA3116 amp, or does it need to go into a preamp before?

 

[sguyader]

The 2 modules you propose are suitable for 24V peak output and 4 ohm speakers (72W/ch). The solution I proposed was for 39V peak output on 8 ohm speakers (95W/ch).

Note that, for stereo operation, at low frequencies, peak supply current as high as 2*24V/4r=12A or 2*39V/8r=9.75A can be demanded. This is the main criteria for sizing the boost converter. The 6A unit covers only 50% requirement, acceptable for, say, >100hz, operation (considering the little bulk capacitor bank included in the dual TPA3116 module).

EDIT: Input impedance of the amplifier module is not listed. NE5532 is an op-amp intended for low signal impedances, input impedance could be a few kohm only. Circuit modification could be needed for optimum musical instrument use.

What do you think of this boost converter:
1 PC DC DC 600 W EN 10 60 V Out 12 80 V Boost Converter Step up Module Voiture Portable Alimentation dans Alimentation a decoupage de Amelioration de l'habitat sur AliExpress.com | Alibaba Group