Lichtlaerm PandorA - 60w pedalboard class d amp

[joecool85]

Lichtlaerm has released it's new pedalboard amp - PandorA.  Providing 30 watts at 16 ohms, and a claimed impressive 60 watts at 8 ohms, the PandorA features simple level, depth, and presence controls.  This is meant to be fed by an equalizer, preamp, or "amp in a box" pedal, or from a lineout on another amplifier.  Pretty great tones to be had here, mostly because rather than just a simple "flat" amplifier, they have adjusted the input impedance and EQ curve to match quality analog guitar gear.  Great job guys!

MSRP is 199 british GDP, or $219 USD.

https://www.gearnews.com/lichtlaerm-audio-pandora/

[J M Fahey]

Those power specs are, should we say .... too optimistic?

No way they can put out 30 Watts into 16 ohm and 60W into 8 ohms.
Not at just clipping that is.

This is what Texas Instruments say about TPA3118 ... they should know:

With a 24V supply, 60W into 4 ohm, around 33W into 8 ohm
That, at 1% distortion which is *just* clipping and the proper way to rate RMS.

The 10% distortion spec actually means a quite clipped signal.

No spec for 16 ohm but it should be about half the 8 ohm rating, some 18 W at clipping.

The video tests it with a puny 12V supply

Best case some 14-15W into 8 ohm, not even near the 30W claimed.

Oh well.

Captured the TI datasheet Power vs. Supply Voltage but found I can´t actually paste it gere.

Tomorrow will find some image site and link it here.

[Loudthud]

Most of these things use a regulated SMPS so they can come pretty close to doubling power with half the load impedance.

[joecool85]

Those power specs are, should we say .... too optimistic?

I think someone misunderstood how PBTL works and/or didn't look at all the graphs.  This chip does 2x BTL outputs.  At 24v, 8ohm, it puts out a solid 33w per BTL output with 1% THD.  At 4ohm, it is 60w.  This chip does offer PBTL, but he graphs only show 2ohm and 3ohm.  At 2ohm you can do an impressive 120w.  This makes sense because each side of the chip would see 4ohms (making 60w), adding up to 120w.  PBTL allows you to run lower ohm loads and higher wattage.  But my understanding is that running PBTL with 8ohm would still only yield about 30w, not 60w.

Attached is the datasheet as well as a couple screenshots of data graphs.

[joecool85]

TLDR: this amp is going to be outputting roughly 30w @ 8ohm and 15w @ 16ohm given a 24v PSU.  For reference, this is inline with the TPA3122D2N that I am working with as well.

[J M Fahey]

Yes, that´s the truth, what is physically possible given the available voltage swing out of 24V.

Glad we are all on the same page.

[g1]

This chip does 2x BTL outputs.  At 24v, 8ohm, it puts out a solid 33w per BTL output with 1% THD.  At 4ohm, it is 60w.  This chip does offer PBTL, but he graphs only show 2ohm and 3ohm.  At 2ohm you can do an impressive 120w.  This makes sense because each side of the chip would see 4ohms (making 60w), adding up to 120w.  PBTL allows you to run lower ohm loads and higher wattage.  But my understanding is that running PBTL with 8ohm would still only yield about 30w, not 60w.

PBTL is parallel running of the 2 sides, something new to me.  But is there anything saying you can't run the 2 sides in series (standard BTL)?  That would give full power into double the impedance.

One more question, in the very first sentence of the datasheet, what does TI mean by "4 ohm BTL load" ? 
A load is a load is a load, isn't it? 

[Tassieviking]

PBTL is just 2 amplifiers working opposite to each other, one puts out a positive signal while the other one a negative and then it reverses during each sinewave.

Usually the speaker negative is connected to ground and the positive to the sinewave, the ground is say 0V and the other +-12V so you get a swing of 12v on the speaker coil.

In PBTL when the positive on the speaker gets +12V the speaker negative gets -12V, and then the reverse in each sine wave, thats a full 24V swing across the speaker coil causing more movement and power.

The load on a PBTL is worked out different then just a single amp module because both amp modules share the load between them.

[g1]

PBTL is just 2 amplifiers working opposite to each other, one puts out a positive signal while the other one a negative and then it reverses during each sinewave.

You are describing BTL.
PBTL is something new to me, putting 2 BTL amps in parallel.
It gets confusing in that TI still refers to the 2 'stereo' sides as BTL.  I guess that is how they are made in the chip, but if you can't access each non BTL amp seperately it is kind of pointless to call them out as such.

So each 'side' of the 3118 is called 'BTL' but you can run the 2 sides in parallel configuration which is called 'PBTL'.
In PBTL configuration you can drive a load half the impedance of what each side is capable of.
Regular BTL requires double the load impedance that each amp seperately would be capable of.
So the 3118 can drive 4 ohms per side, or 2 ohms in PBTL configuration.

[J M Fahey]

But is there anything saying you can't run the 2 sides in series (standard BTL)?  That would give full power into double the impedance.

The confusion comes from the fact that TPA3118 actually has FOUR "standard" amplifiers inside.

Two are prewired (you can´t separate them, it´s internal to the chip) as bridgedand they call that Channel 1 , other two are w1red same way and are called Channel 2.

That´s why even if you use both halves separate, as a Stereo amp, each of them requires a floating load.
 
That´s why each of the channels is already BTL, you can´t undo that.

Now if you wire both BTL amps in parallel, you can get twice the current but peak voltage does not change.

 

One more question, in the very first sentence of the datasheet, what does TI mean by "4 ohm BTL load" ?
A load is a load is a load, isn't it?

True.
But BTL means how/where is that load connected. 

Personally, I would have callad each Channel simply "bridged amplifier", period, but somebody called them BTL and others copied it.

PBTL is just 2 amplifiers working opposite to each other, one puts out a positive signal while the other one a negative and then it reverses during each sinewave.

That is plain BTL and is already happening inside each channel.

It gets confusing in that TI still refers to the 2 'stereo' sides as BTL.  I guess that is how they are made in the chip, but if you can't access each non BTL amp seperately it is kind of pointless to call them out as such.

Each side already IS BTL.
True, you can´t access any of the FOUR amplifiers on their own, only as prewired bridged outputs.

Just thinking aloud: maybe TI does not even mention that (although it is implicit) because it wpuld be even more confusing.

Bet DIY Audio and similar sites would fillto the brim  with threads explaining how to separate each half or something.

Guess the idea is: just use them as we suggest and don´t overthink details.

[g1]

That´s why each of the channels is already BTL, you can´t undo that.

Now if you wire both BTL amps in parallel, you can get twice the current but peak voltage does not change.

I'm still wondering if Ch.1 and Ch.2 can be put together in regular bridged configuration, rather than the parallel PBTL.
If so, it would give full chip output into 8 ohms (rather than the 2 ohms of PBTL).
The reason I raise the question is that if it were possible, that may be what the Pandora is doing and how they get that high power figure into 8 ohms.  If so, I guess the amp would be marked 'minimum load 8 ohms'.  (edit:  minimum load 8 ohms confirmed here:  https://lichtlaermaudio.com/shop/pandora )

[joecool85]

That´s why each of the channels is already BTL, you can´t undo that.

Now if you wire both BTL amps in parallel, you can get twice the current but peak voltage does not change.

I'm still wondering if Ch.1 and Ch.2 can be put together in regular bridged configuration, rather than the parallel PBTL.
If so, it would give full chip output into 8 ohms (rather than the 2 ohms of PBTL).
The reason I raise the question is that if it were possible, that may be what the Pandora is doing and how they get that high power figure into 8 ohms.  If so, I guess the amp would be marked 'minimum load 8 ohms'.  (edit:  minimum load 8 ohms confirmed here:  https://lichtlaermaudio.com/shop/pandora )

To my knowledge, you can't bridge the already bridged outputs.  This chip is designed to do mono as PBTL only and for sure can do 60w of output, just not at 8ohm but rather at 4ohm.