Any DC-powered amps work like Proton "Dynamic Power on Demand"?

[Mark185]

picture is a dual TPA3255 amplifier board I am experimenting with. Chips on the bottom are input opamps. Chips above them with thermal paste on them are TPA3255. Square devices with number 100 are called inductors. Next to them are capacitors (red). The capacitors and inductors form an output filter to block most of the high frequency switching noise from the output transistors. Switching frequency is typically somewhere between 425-650 Khz. All class D amps have these filters. Quality of the inductors and capacitors has impact on distortion and SNR.

 

[kyuu]

PFFB is overrated IMO. If the output filters are optimized for the speaker load you intend to use (ie. 4 or 8 ohms) there is no need for PFFB. Nice to have but you can get very good performance without it.

This is a weird statement. One, even if accurate why would you want an amp that only works correctly with very specific speakers? Two, it doesn't seem like this can be accurate since a speaker's impedance varies with frequency. Three, if you can get a flat frequency response in the audible band why wouldn't you want that? Unless you simply can't get it at your desired price point and/or with your desired feature set.

 

[john61ct]

> speaker's impedance varies with frequency

And some lots more than others, LS50 famously so.

Hence needing relatively high current to get to max-safe SPL, more important than the basic watts power rating.

 

[EJ3]

From what I can tell, he has from 24V-60V DC power in his home and would prefer not to convert to AC & then back to DC.
So the objective would be to find a powerful enough POWER amplifier (with a DC 24-60 Volts input {so he would not have to convert power] to then power his sub-woofers).

At least that is what I am getting from this thread.
Please correct me if I am wrong.

 

[Mark185]

This video explains quite a bit about output filters on a good amp that does not have PFFB. PFFB has a very slight impact on frequency response in the 18-20 kHz range with a well designed amp. If you can hear sounds in and above that range, you are in the minority.

 

[Roland68]

I mean power amps with DC power input. That can include equipment designed for mobile use, or pro or audiophile gear so long as they can be powered via DC as many external PSUs supply.

Whatever the voltage is OK.

> it offers (and technically cannot offer) absolutely no advantage in sound or performance measurements.

It did offer much more headroom for transient power demands far above the RMS rating, hence caught my interest. OK, I understand not relevant to my use case

> cheaper (stripped-down) version of a Class AB amplifier.

Do you consider Class AB superior to Class D for high SQ? Taking a poll...

> With a low-pass filter at 200 Hz, the LS50 can't draw 30-40 watts; that's physically impossible.

Interesting, I did not realize that.

BTW a HPF (min Hz) but I bet you knew that. I will not use any LFP on the front/main pair nor any of the other full-range speakers, only on MBM/subs.

> Moreover, the TPA3251 used in the LS50

Wut? mine are OG passive as I stated, do you mean an active variant?

May I ask why you want to use a DC input for the amplifiers?

Where would you get the +/- 107 volts for the D1200, for example?

Is this for mobile use?

What about availability? Is it limited?

Or is there another reason?

Sorry, my mistake, it was a bit late. I meant, "Even a 3E Audio A5 or Topping PA5 II/Mini300 would be overkill and more than sufficient. Furthermore, the TPA3251 used in the listed amplifiers is even slightly better than the TPA3255 in the A7."

 

[john61ct]

he has from 24V-60V DC power in his home and would prefer not to convert to AC & then back to DC.

The usual 12V "range" is easiest, but many power amps have higher power/current output when fed higher volts, which we can accommodate NP, any DC voltage is fine, the 60V ceiling is just a preference.

And "home" is where I hang my hat, off grid cabin, boat, truck camper, hosting a party out in the desert...

I have nothing against small inverters for low power line level gear that require AC. I just don't want to do that for high power gear.

The GFA-555 stays back on the AC grid connection.

 

[john61ct]

Where would you get the +/- 107 volts for the D1200, for example?

Again, I have no interest in the D1200 specifically, nor the NADs, I was only asking about their ostensibly unique technology

hoping there were equivalents DC units

which y'all have now set me straight about.

> Is this for mobile use?

Also stationary-off-grid.


> Even a 3E Audio A5 or Topping PA5 II/Mini300

Fosi V3 Mono or 3e A7 are minimum power levels, would prefer higher.

Willing to sacrifice SOME SQ purity to get that higher power even if the LS50s don't need it,

and also bass management built into the amps.

Or I will need to invest additionally into inexpensive non-DSP crossovers

finding that to be a rabbit hole in itself, especially featuring BPFs for the "basstand" MBMs

Currently researching

3-Way Active Crossover With Line Driver

Shop online DS18 XM3 3-Way Active Crossover with Sub-Level Control. 3-way active crossover. FREE SHIPPING on all US Orders.

ds18.com

2XS - AudioControl

archive.audiocontrol.com

The latter is likely cleaner SQ I think?

Is that an "active" crossover? I love the idea of swapping those resistor network modules to adjust the crossover point rather than knobs that are likely to drift

"poor man's Marchand" ;-)

But I like the former's gain control, and the sub level remote may come in handy

maybe even adjustable bass boost?

 

[john61ct]

This video explains quite a bit about output filters on a good amp that does not have PFFB.

I love his videos, thanks, great learning but currently way above my paygrade. I'll stick with 3e A7 anyway as my top TPA3255 even if "overkill" not like PFFP has a downside,

Not saying it's necessary, but proper implementation along with PBTL at least shows design competence.

 

[john61ct]

to then power his sub-woofers

Here my focus is on just the front main pair, but yes ideally I can standardise on one power amp to drive all channels.

Ability to bridge channel pairs would give flexibility

For mono true subs (say matching SPL down to below 40Hz) my understanding is going to multiple say 10" driver boxen can compensate for the relatively lower power per amp, and flexible placement help overcome "room mode" issues. Infra/sub sonic HPF is often missing from crossover units, thinking maybe a standalone inline passive filter will do for that.

For the stereo basstands (BPF'd maybe 60-200Hz maybe higher) going to 2Ω loads might be good for efficiency, no bridging needed.

Some 4-channel amps from the auto world look promising in that regard...

I want the center to be able to dominate when watching films (relatively rare) thinking of maybe using a pair of more efficient speakers in mono for that, collocated with a mono true sub for the Michael Bay booms

 

[EJ3]

The usual 12V "range" is easiest, but many power amps have higher power/current output when fed higher volts, which we can accommodate NP, any DC voltage is fine, the 60V ceiling is just a preference.

And "home" is where I hang my hat, off grid cabin, boat, truck camper, hosting a party out in the desert...

I have nothing against small inverters for low power line level gear that require AC. I just don't want to do that for high power gear.

The GFA-555 stays back on the AC grid connection.

I fully understand, as I am similar in need, at times: It's why I always have, at a minimum a 750 watt 12V to 120V inverter for my truck, just in case I want to run something small.
At my cabin (the last place the power grid line runs to): I have 30 amps of service from the power company. It's also a place that is close to the river.
Any thing else I need power for, I supply it, one way or another, where ever I am (240 can be an issue, though [but rarely needed]):

I think that the ratio of boats to land vehicles is about right at my location.

 

[Mark185]

Again, I have no interest in the D1200 specifically, nor the NADs, I was only asking about their ostensibly unique technology

hoping there were equivalents DC units

which y'all have now set me straight about.

> Is this for mobile use?

Also stationary-off-grid.


> Even a 3E Audio A5 or Topping PA5 II/Mini300

Fosi V3 Mono or 3e A7 are minimum power levels, would prefer higher.

Willing to sacrifice SOME SQ purity to get that higher power even if the LS50s don't need it,

and also bass management built into the amps.

Or I will need to invest additionally into inexpensive non-DSP crossovers

finding that to be a rabbit hole in itself, especially featuring BPFs for the "basstand" MBMs

Currently researching

3-Way Active Crossover With Line Driver

Shop online DS18 XM3 3-Way Active Crossover with Sub-Level Control. 3-way active crossover. FREE SHIPPING on all US Orders.

ds18.com

2XS - AudioControl

archive.audiocontrol.com

The latter is likely cleaner SQ I think?

Is that an "active" crossover? I love the idea of swapping those resistor network modules to adjust the crossover point rather than knobs that are likely to drift

"poor man's Marchand" ;-)

But I like the former's gain control, and the sub level remote may come in handy

maybe even adjustable bass boost?

I have built Marchand crossovers in the past. They are good for what they are but in today's prices, they cost way too much. I have also used Audio Control active crossovers. I prefer their 24 XS which is 24 dB/octave Linkwitz Riley and still has pluggable resistor networks to switch frequencies. I still have 2 of them on the shelf and am comtemplating using them again. I think absolute best bang for the buck right now is the Down 4 Sound EZDSP 68+. lt is based on the very good Analog Devices ADAU1452 DSP chip. I bought one of these over a year ago and have been very impressed with how it performs.

DOWN4SOUND EZY DSP68+ - All-in-One Hi & LOW LEVEL Car Audio DSP 6-in-8 Out

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The owner of this business appears to have a lot of haters but the EZDSP processors he sells are good values with low noise and distortion. The processors are not quite as good as those from ARC Audio and Helix but they come close for a lot less $$$. Helix does make a DSP Mini which only has 6 channels I have seen priced as low as $399 used on Ebay but if that suits your needs, it is a great processor with the best software support in the industry. There are cheaper mobile DSP units under $200 but I have no experience with them. At the $200 price point, there is the Dayton Audio DSP-408. I own one of those also. It is a bit overpriced for what it offers. It used to sell for ~$150 before tariffs made everything go up in price. When you could get one for less than $150, it was a good deal.

All of these 12 Volt DSP units can be used in home environments with a suitable low noise supply. I would not recommend investing in an analog active crossover with the maturity of lower cost DSP units now.