NEW BRZHifi PAD-30 : Dual TPA3255 +PFFB @ $99

[john61ct]

Well that's the point of testing.

Maybe a valid alternative if clean enough, for those wanting cheaper and willing to accept lower power.

But I agree lower priority than Fosi CA30 8-D

 

[Ruediger]

I think in terms of power it will be with the other dual TPA3255 amps. If a 48v10a psu is used.

The specs read a bit off with that mono rating. I guess these are per channel in stereo operation, very colorful at a high THD.

 

[john61ct]

3e A7 mono at 51V 10A is my power availability benchmark.

Not cheap ofc, so if this unit is clean, a great alternative for less thirsty channels

 

[Ruediger]

I use the A7 mono for the center in my home cinema. The 3e audio amps integrate nicely with their auto-sensing and no need for (a lot of) trigger cables.

They offer it at sporty prices here and there and include the 48v5a GaN psu. Can't go wrong with this choice.

But it's still about double what this stereo box costs. And the A7 stereo even a good bit more. But I consider these the very best of the TPA3255 poweramps at this time (that I know of).

I like the BRZhifi better for a "not so clean" setup like a garage stereo though. It doesn't have huge openings for venting and external access. It will be better in a bit more dusty environment.

 

[john61ct]

I meant SQ specs as in clean signal. Doesn't need to be "as perfect" as 3e, just so we are informed of any quirks before committing, even with low investments

 

[ICIETDIYEUR]

@ Ruediger

In the previous posts, you indicated:

1> The trigger port doesn't fit properly. The various cables require adjustments every time -> that is not the case with the unit I received.

2> When the device is turned off, the red power light flashes, which is very annoying -> in my case, the light is off (which is normal).

3> The on/off volume knob seems to have a lot of play -> I haven't noticed any issues in this regard, and the volume levels for each channel are perfectly balanced, even at the lowest setting (unlike with much more expensive amplifiers, such as those from 3eAudio).

4> ... very colored sound and high total harmonic distortion -> I haven't observed anything to support such a claim; do you have objective measurements to back up your statements?

 

[Ruediger]

Are you trying to misunderstand me?

1) It didn't work initially, only after wiggling around there. With different cables. It then stayed working. Just a poor fit.

2) Interesting! What is mine doing different?

4) Referring to the power specs, max. power indicated above max. power from biggest psu, at 10% THD or so? Colored as in a tube amp going mad.

 

[ICIETDIYEUR]

2> Actually, nothing. The PCBs, components, and their layout appear completely identical across the production units; I therefore do not understand why your LED flashes when the device is turned off using the volume knob (which acts as the power switch), because on my unit, the amplifier is completely powered down—not just in 'idle' mode—and the LED is off.

4> It is a general observation that, since the release of Class D amplifiers using the TPA3255 chip, almost all retailers have been listing incorrect power ratings; they ought to state power figures measured within the limits acceptable for "Hi-Fi" equipment, backed by graphs. As for the sound coloration you are experiencing, I haven't found the same issue with my own amplifier; this may be because I replaced the op-amps—as I mentioned earlier, one of the ones on my unit was microphonic. Upon closer inspection, they turned out to be very poorly made components—visible by the exposed pin connections on the sides—which is why I recommended replacing them.

The ones I installed are genuine parts from Audiophonics.

The models I selected are designed to operate with low power supply rail voltages; furthermore, as I previously noted, the OPA1642 (JFET) models are better suited to the circuit's input impedance requirements, and Texas Instruments specifically engineered them to perform well in environments subject to EMI and RF interference.

I do not have the equipment needed to confirm this through measurements, but the difference is unmistakable simply by listening; furthermore, the datasheets for these op-amps provide sufficient information to state unequivocally that they represent an improvement over the poor-quality op-amps originally installed

 

[Ruediger]

2) We might do different things here. When the trigger didn't work, I used the knob on/off. Tried trigger with the unit on, then off.. thought it needs a certain state of the knob for trigger to function. It then started working, but off = standby LED. Maybe the behaviour is different as per the state of the power knob. I will see.

4) Yes absolutely. I find those numbers a bit laughable. I experience no coloration. I was expressing that when one draws the max. power as per the spec sheet, he is probably at 10% THD and that distortion will color the sound pretty good. It will also make one's ears bleed.

It's an interesting, inexpensive little box for some DIY work.

I was looking for that psu at audiophonics, but they now list it for the same price with just 7.5a. Different stock I guess. I don't see that 42v psu anywhere else.

Capacitors - working on it.

Also noted the opamps.

If you don't mind, if you keep a "parts list" for this thread of all the little tweaks you found and did - that can be helpful to many others I guess.

 

[RandomEar]

I do not have the equipment needed to confirm this through measurements, but the difference is unmistakable simply by listening;

You've been around long enough on ASR to know that that isn't sufficient, isn't reliable and isn't proof of anything. You expected improvements, you've heard improvements - congrats, you confirmed that bias is real.

There must be a dozen threads talking about detailed measurements of op amps and specifically showing that the hypothetically possible improvements are negligible for each and every audio circuit and that in practice, equal or worse measured results are vastly more likely. Audible differences essentially do not occur unless you insert op amps which become unstable or overloaded in that specific circuit.

Does Op-amp Rolling Work?

When I post my last video on review of Douk A5 amplifier, I mentioned that rolling (changing) op-amp ICs in there is fruitless. I got have a dozen comments under that video in youtube asking why so I thought I experiment again with the A5. Note that I have done the same testing with both DACs...

www.audiosciencereview.com

Op-amp Rolling Using Sparkos on Fosi V3 Mono

This is a study of measured differences if one swaps up the TI NE5532p dual IC op-amp in a Fosi V3 Mono amplifier with a "discrete" opamp from Sparkos. It is a test requested in the youtube comments of my video test of the same using Douk A5 and Sonic Imagery op-amp. The Sparkos SS3602 retails...

www.audiosciencereview.com

Op-amp Rolling Using AIYIMA A07

I have made my homework and re-measured AIYIMA A07 with NE5532, LME49720 and OPA2134. My measuring system has been improved since the time of my first measurements of the A07. However, no breakthrough findings, but good enough to debunk some strange myths. I measured the A07 supplied from SMPS...

www.audiosciencereview.com

Fosi Audio V3 op-amp rolling, has anyone tried it? Snake oil? Or are there actual differences?

A plastic cup holds water. A glass looks better, has better specs in certain areas... but still it just needs to hold water, which it does fine be it crystal, Ikea glass or plastic. And sometimes the "worse" component, a plastic cup, is just what was specified for the job and lasts longer and...

www.audiosciencereview.com

 

[RandomEar]

If you don't mind, if you keep a "parts list" for this thread of all the little tweaks you found and did - that can be helpful to many others I guess.

It's not helpful, it is misleading misinformation. This isn't audiosnakeoilreview.com

 

[Ruediger]

It's not helpful, it is misleading misinformation. This isn't audiosnakeoilreview.com

The listening part, I fully agree. But if there are inexpensive parts that are a better electrical fit and serve as spare parts, I simply like that info.

 

[RandomEar]

The listening part, I fully agree. But if there are inexpensive parts that are a better electrical fit and serve as spare parts, I simply like that info.

But how will we know if parts are a "better electrical fit" if there's no measurements or at the very least some circuit simulations?

 

[Ruediger]

But how will we know if parts are a "better electrical fit" if there's no measurements or at the very least some circuit simulations?

Oh, I see what you mean. He replaced OPA1612 with OPA1642. I thought he found the same opamp as originally installed at audiophonics, but in a better version.

Nothing to see here then.

Audiophonics also has the OPA1612 of course, it costs a bit more than the OPA1642. These opamps have quite different supply voltage specs. No idea if these are even suitable drop-in replacements.

 

[ICIETDIYEUR]

@ RandomEar:

I am not trying to provoke you—let alone be disrespectful—but your attitude is disheartening.

You persist in repeating things that everyone else has managed to read and, more importantly, understand—though that does not seem to be the case for you.

It is obvious that "OP-rolling," as practiced by some, is merely a game; given that they possess at least some technical knowledge, they wouldn't waste time—and certainly not money—on it otherwise, knowing full well they are risking damage to their equipment or, worse, causing a breakdown.

I believe Amirm has pointed out in his reviews (which include measurements and/or comparisons) that one cannot simply label certain op-amps as "good" or "bad" (though that can sometimes be the case with poor designs or shoddy manufacturing); rather, they may simply be unsuitable for the specific circuit in which they are being used.

This isn't a game; it is technology based on sound principles. Datasheets are designed to steer people in the right direction—provided they take the time not only to read them thoroughly but, more importantly, to interpret them correctly.

Furthermore, if you took the time to read everything I’ve written, you would see that I am not just spouting whatever pops into my head; I have actually participated in numerous private discussions (via email) with O-NOORUS, SYLPH Audio, and even 3eAudio back in the day.

We exchanged ideas, experiences, and technical solutions aimed at improving the Class D amplifier circuits discussed here (specifically those using Texas Instruments TPA3255 chips).

It wasn't really about subjective opinions—though those can't be entirely ruled out, given the human element involved.

The subjective aspect cannot be overlooked because, for instance, you cannot make someone appreciate the "best dish in the world" if they dislike the main ingredient used to prepare it.

Just because they do not enjoy it while you do, it does not mean that either of you is wrong...

That being said, if you look back at what I wrote, you’ll see that I refer to Texas Instruments' datasheets and recommendations. I fail to see how anyone could presume to question their findings, considering they are the inventors of these power chips and op-amps—do *you* claim to know better? I certainly don't.

So please, at least take the time to properly read what a poster has written, or ask questions if you didn't understand or if they didn't express themselves clearly.

As for me, it would be a great pleasure to try to help you gain a better understanding.

Best regards

 

[RandomEar]

@ RandomEar:

I am not trying to provoke you—let alone be disrespectful—but your attitude is disheartening.

You persist in repeating things that everyone else has managed to read and, more importantly, understand—though that does not seem to be the case for you.

It is obvious that "OP-rolling," as practiced by some, is merely a game; given that they possess at least some technical knowledge, they wouldn't waste time—and certainly not money—on it otherwise, knowing full well they are risking damage to their equipment or, worse, causing a breakdown.

I believe Amirm has pointed out in his reviews (which include measurements and/or comparisons) that one cannot simply label certain op-amps as "good" or "bad" (though that can sometimes be the case with poor designs or shoddy manufacturing); rather, they may simply be unsuitable for the specific circuit in which they are being used.

This isn't a game; it is technology based on sound principles. Datasheets are designed to steer people in the right direction—provided they take the time not only to read them thoroughly but, more importantly, to interpret them correctly.

Furthermore, if you took the time to read everything I’ve written, you would see that I am not just spouting whatever pops into my head; I have actually participated in numerous private discussions (via email) with O-NOORUS, SYLPH Audio, and even 3eAudio back in the day.

We exchanged ideas, experiences, and technical solutions aimed at improving the Class D amplifier circuits discussed here (specifically those using Texas Instruments TPA3255 chips).

It wasn't really about subjective opinions—though those can't be entirely ruled out, given the human element involved.

The subjective aspect cannot be overlooked because, for instance, you cannot make someone appreciate the "best dish in the world" if they dislike the main ingredient used to prepare it.

Just because they do not enjoy it while you do, it does not mean that either of you is wrong...

That being said, if you look back at what I wrote, you’ll see that I refer to Texas Instruments' datasheets and recommendations. I fail to see how anyone could presume to question their findings, considering they are the inventors of these power chips and op-amps—do *you* claim to know better? I certainly don't.

So please, at least take the time to properly read what a poster has written, or ask questions if you didn't understand or if they didn't express themselves clearly.

As for me, it would be a great pleasure to try to help you gain a better understanding.

Best regards

You imply that I've neither read nor (fully) understood your posts, but you are in no positionto make that kind of judgement. The additional jab that everyone else but me understood it even makes the statements pejorative and is a clear sign that you do not seem to be interested in a civilized discussion. If you ask me, there is no place here for this kind of attitude.

I'm not denying that you can read datasheets or that they are useful and a great guidance. I honestly do not care who or where you discuss those with. My grievance here is simple: You exchanged parts for "better" parts and claim audible improvements, without supporting this with any evidence. If you had read my post with the same care you expect from others, you would have easily grasped that. I can simplify it to three points:

• Claiming audible improvements without controlled testing or measurements is bogus
• Small measurable (but not audible) improvements by op amp swapping are possible, but less likely than no change or a deteriotation - I get that you know more about the circuit than the random audiophile, so your chances are higher to not make it worse
• The changes seen in any op amp swapping experiment on ASR were either inaudible (no change or inaudible improvement), or a clear deterioration

 

[Krusty09]

This is boring. Send this to the galactic waste .

 

[ICIETDIYEUR]

You claim to have read and understood my posts, yet I maintain that you haven't; I clearly pointed out that the unit I received contained a microphonic op-amp which I subsequently replaced. Since I started with a malfunctioning unit and restored it to proper working order, I was naturally able to get better performance out of it.

I also noted—citing Texas Instruments datasheets—that given the high input impedances (10kΩ) and the fact that they differ for each input, a FET-type op-amp was more suitable for this specific circuit; nothing more.

Contrary to your insistent claims, I am not passing judgment, nor am I using derogatory language; in fact, you are the one who initiated a discussion—for reasons I do not understand—that has no place here.

I simply provided readers with objective information that can be verified by consulting the manufacturer's datasheets, as well as the photos and annotations regarding this device that I was happy to share.

Whenever I expressed subjective opinions, I explicitly stated as much, leaving no room for ambiguity on the matter.

 

[ICIETDIYEUR]

Hi again

I’ll try here to better explain the reasoning behind my choice of op-amps for this amplifier (bearing in mind that one of the factory-installed op-amps was defective).

For now, I will only discuss two of the op-amps (see the photo below), as I haven't yet fully analyzed the circuit schematic for the one located next to the volume potentiometer.

The following photo makes it possible to identify the circuit's resistance values, which is of great importance, as will be seen later.

Here is a "simplified" diagram for greater clarity and a better understanding of what follows.

Important note: The OPA1612 (a bipolar type) incorporates a bias current cancellation circuit; consequently, the specified low current noise is achievable only if both inputs see the same impedance (see the datasheets)—which is not the case with this circuit, as is clearly evident from the schematic.

To avoid ill-advised actions—such as simply swapping the operational amplifier—refer to the specifications in the Texas Instruments datasheets (for example).

As a reminder—and to be more precise—the OPA1611 (the single-channel version of the OPA1612) are bipolar devices, just like the JRC 5532DDs originally installed in the amplifier; however, the OPA1612s are much newer and, above all, offer superior performance when comparing their respective datasheets.

That said, we can examine the relevant sections of the OPA1612 and OPA1642 datasheets (I have added a few annotations, as you will see).

We can see from the graphs that with a 10 kΩ source resistance, the "noise" (Eo) is higher and rises progressively with the OPA1612, whereas it starts lower with the OPA1642 before eventually "tracking" the input source resistance noise.

Another important factor regarding operating conditions: the OPA1642 and OPA1656 op-amps feature EMI and RF interference filtering, unlike the OPA1612 models.

Admittedly, one could argue that these are merely assumptions since no measurements were actually performed on the amplifier in question; however, logic suggests that its performance should be superior.

This might not show up in our measurements—as we lack the equipment, methodology, and expertise of Texas Instruments engineers—but in any case, it seems highly unlikely that the measurements would be worse than those obtained with the original op-amps.

In 2023, I briefly asked Lester (SYLPH AUDIO) about this, and here is a short excerpt from his reply (there is nothing "secret" here) ->

"... The resulting THD+N will depend on the 'circuit' in which the op-amp is used.
If high-value resistors and low gain are used, distortion will be low with many op-amps, but noise will dominate; FET input stages like the OPA1656 and OPA1642 will offer better noise performance.
If low-value resistors and high gain are used, noise will be low with many op-amps, but distortion performance will vary from one op-amp to another."

You can read this discussion:

https://www.diyaudio.com/community/...st-possible-thd-n-really-the-best-way.367692/ ...)

The link he "sent" me is very interesting, and I encourage you to read it.

The linked content describes an experiment conducted by a member; I will provide a brief summary to explain why I chose the OPA1642 over the OPA1656, a more well-known op-amp. Here is the experiment in question (measurements included) ->

1> Schematic of the setup used:

2> Measures taken:

3> Conclusion and some necessary explanations regarding this "experiment":

The OPA1656 is somewhat noisy at low frequencies.
Below is a comparison between the OPA1656 and the OPA1642.
Two identical amplifiers with a gain of 11 were tested.
Each amplifier consists of two operational amplifiers connected in parallel in a balanced configuration.
The input is short-circuited via a 10 mΩ resistor to obtain a reference signal of -140 dB; this approach is based on Dicks' website.
The output of the 1656/1642 amplifiers is further amplified by 90 dB.
The measurement system is calibrated in dBV and Virtins displays the noise spectrum, so no additional spectral correction is required.
In this configuration, the noise at 10 Hz is 200 nV/√Hz for the OPA1656 and 40 nV/√Hz for the OPA1642.

In conclusion:

Please understand that this reflects my personal opinion; I am not trying to influence anyone or claim to be right. It is simply the choice I made based on the visible and identifiable components, the relevant circuit schematic, and the data and recommendations provided by the manufacturer (Texas Instruments).
All these factors seem objective enough to justify the choice of operational amplifiers I selected.

I am not perfect and can make mistakes like anyone else; I am simply sharing information that I believe is useful and aligns with the "scientific" spirit of this site.

Thank you for taking the time to read this.

Have a great day, everyone

 

[john61ct]

Another, designated for subs, adjustable phase, adjustable LPF, unknown if rumble filter HPF

unknown if same manufacturer

TPA3255 600W High Power Professional Grade Subwoofer Digital Amplifier Board Finished Machine Low Frequency Frequency Adjustable

https://a.aliexpress.com/_mNSNmi7