Topping LA90 Review (Integrated Amplifier)

[xrk971]

Now I just wish there was an RCA version of this.

Just stick a RCA to XLR converter or RCA to TS (mono plug) converter. The amp will ground the negative input and drive the positive side. It will sound good and work quite well. You might not be able to get the full +/-32v swing. So no high power stuff.

 

[jae]

Now I just wish there was an RCA version of this.

 

[Toku]

~90W @ 4Ω of beyond audiblity ean power for ~10$ per W
Or
~350W @ 4Ω of beyond audiblity clean power for ~4.5$ per W in the form of competent Purifi application

Vote with your wallet.

It's not something that can be compared simply by money.

 

[Toku]

The LA90 is designed as an amplifier for balanced input only. The one in the photo cannot be used.

 

[JSmith]

Now I just wish there was an RCA version of this.

You could get a pre-amp that has balanced and unbalanced input/output conversion... although that negates the need for an integrated. Pre90 is an option for that path, but not overly cheap.


JSmith

 

[tomchr]

If you watch closely, there is a recognition in the industry that we need to move away from specifying amplifier output capability using "power" with sine waves. IMHO, the FTC method is holding us back for the development of more meaningful industry standards.

And the confusion is pretty clear in your statement in Post 760, which is why I objected to it.

I do agree that power into a purely resistive load with a pure sine wave is not the most meaningful spec if you're looking to see how an amp will behave with music in an actual system. However, it is a meaningful spec for comparing Amp A and Amp B.

The best variable for characterizing the clipping behaviour would be the output voltage, but that doesn't tell you how loud your speakers will play. Not without some math anyway. You could specify the peak output power at the onset of clipping. That would work around the crest factor issue nicely. Neither deal with the fact that the speaker impedance is not constant and often reactive.

I agree that RMS output power with a single tone is not the most meaningful spec, but for those who can do math it provides enough information that they can design a good system around the amp. And for those who can't do math (or don't like it) a power number does provide a meaningful comparison point. Just like the horsepower number for a car. It doesn't say anything about how the car handles in the curves or on ice, but I think even novice drivers will recognize that a 150 HP car is less powerful than a 500 HP car.

Tom

 

[DamianW]

If you watch closely, there is a recognition in the industry that we need to move away from specifying amplifier output capability using "power" with sine waves. IMHO, the FTC method is holding us back for the development of more meaningful industry standards.

Speaker sensitivities are now specified as a voltage sensitivity (i.e. dB SPL @ XXX V rms 1 m). So why do we need to convert amplifier power into voltage and then calculate SPL to see if the amp is powerful enough, instead of just giving us the voltage output capabilities? Of course, the amp spec must also include the info so that we'll know the amp is capable to supply the required current due to the speaker load impedance.

Below is a clip from the ANSI/CTA-2034 standard (the standard is more than just spinorama). In the data reporting of the required amplifier "power", it requires listing the amplifier output voltage, with the implicit requirement that the amp must be able to deliver the required current per the speaker impedance. Also, it accounts for a 12 dB crest factor.

You can see in the example they gave (of a pair of the example speakers in a typical room of 200-600 sq ft at a typical listening distance of 4 m), to drive it to the "loud" rating of 95 dB SPL full range, the power requirement is 158 W into 8 ohms, or a clipping threshold of minimum 50 V -- not a handful of watts.

View attachment 202983
yo

Apologies in advance if I missed it but what was the sensitivity of the speakers used for this table?

 

[formula 977]

Is this integrated amp configured as a current source?

 

[MaxBuck]

Not powerful enough for my personal use case, but unquestionably a technical tour de force. Bravo, Topping!

 

[jhaider]

If you are going to make the argument of conflation, at least verify your post is not referencing RC.

Goalposts, goalposts. As I stated, the sentence you truncated and then emphasized concerned bass management.

As to limiting the argument to bass management, that actually makes your argument even more spurious. Bass management is extremely uncommon in stereo setups,

You're probably right. I think that is an unfortunate and low-fidelity state of affairs.

Moreover, if bass management is critical to a user, there are numerous ways of addressing this. At the risk of repeating myself, one can:...

What you describe after my ellipses is how to deploy this product as a power amp in a more sophisticated system, not how to use it as an integrated amp. My comments you quoted are limited in scope to the use case integrated amp and are wholly out of scope of the use case power amp. Remember, the "integrated" functions here are source switching and volume control. If you're using a Mac or upstream DSP as source or processor, you're by definition not using the integrated source switching capability to choose between sources or the integrated volume control to control system volume. That makes the integrated functions useless appendages. So the one making a spurious argument here is...not me.

As a power amp, I expect it's as good as any other in its power class in audibly relevant factors. Of course this amp crushed the bench tests Amir performed for noise and distortion within its power limits, so spec-chasers will be in love. Personally, I wouldn't trade a stereo Purifi based amp or a pair of Hypex NC400s for it; either of those provide a great deal more power, generated with presumably higher energy efficiency, and measured performance still above audible limits. But if someone else finds this particular product a good fit for her use case, cool.

Lastly, I'm flattered that someone would conflate me with @hardisj. I expect Erin is less so.

 

[DACs_Lover]

The absolute sound, stereo Phil’s and the like will be pissed that megabuck gears cannot outperform Topping’s.

From Dac Preamp to integrated amp.

 

[solderdude]

Any clue with the provided wire bridge for the two unused (-) when bridged? Would a splitter/virtual gnd. design require that wire? Or is this something else (nested feedback)?

Virtual ground is not used in that case (no current drawn but will be the reference)
Possibly there are 2 virtual grounds, one for each channel for better channel separation ?
Only @JohnYang1997 can tell us how it is done.

Nested feedback has nothing to do with this.

Thanks for the clarification. but is it for rca or balanced as they're usually not the same

It only has balanced inputs and that is 20k input.
It is unclear whether this is truly balanced (not ground referenced) input or just symmetrical and whether or not it basically is 2x10k per input.
You can use RCA to XLR or RCA to TRS adapters to convert the input. You would have to take into account that the input sensitivity drops 6dB so you will need double the output voltage on RCA to drive it to full power or use a DI box or something similar.

 

[NTK]

And the confusion is pretty clear in your statement in Post 760, which is why I objected to it.

I used a phone when I posted post #760. I was too terse and failed to adequately explain my point. I have the utmost respect for your technical skills and abilities. I know you know this topic inside out, and any misunderstanding has to be due to my failure to communicate.

 

[KSTR]

The LA90 is designed as an amplifier for balanced input only. The one in the photo cannot be used.

Porbably. At least that's what Topping states: "compatible with XLR and TRS interfaces", not explicitely mentioning TS here.

OTOH, a balanced input by sheer definition must handle unbalanced signal as well with no problems, otherwise it's just not a viable balanced input whose definition is to subtract out any common-mode signel (when driven with TS unbalanced cable then the common-mode signal is simply half of the differential signal).

Offering TRS input invites users to plug in TS inputs (or RCA to TS adapters) and therefore it would be very strange if TS really isn't allowed (aka creating problems). Or did they state that just because the leakage current from their PSU is very high which easily creates noise in unbalanced interconnects?

This is Topping and as we have seen for the PA5 Inpus they may do things in a non-conformant style and provide little technical detail about connection / input topology and its limiting values.

 

[KSTR]

Yes, it is. The circuit used will be more similar to the one I posted.
A Virtual ground basically is a power amp with 1/2 input voltage DC out that can drive large capacitors and source/sink the needed current.

If there really is an internal rail-splitter in linear class-A/B we'd still have some useless power dissipation, being just an undriven bridge half. Large local bulk caps after the splitter do help... but not much for very low frequencies. The amp isn't DC coupled but what happens with, say, a <20Hz "earthquake" mono signal at full blast?

If split locally, why then the 3-prong DC supply connectors? This style is available in 2-, 3- and 4-pin variants. Maybe the 3-pin was simply the cheapest they could get?

 

[antcollinet]

Is this integrated amp configured as a current source?

Are any amps configured as a current source? Audio amps are (to my knowledge) always voltage sources.

 

[pma]

Are any amps configured as a current source? Audio amps are (to my knowledge) always voltage sources.

Audio power amps are all voltage sources with minimum output impedance. Speakers have flat frequency response when driven from voltage sources. When driven from current source, the frequency response of the speaker would copy its impedance curve. Amp may be designed as a current source, but then EQ or impedance compensation must be used to get flat response.

 

[Deleted member 46664]

Now I just wish there was an RCA version of this.

The input jacks are a combination Balanced and Unbalanced input. You can use Male XLR or TRS male plugs for Balanced audio. If you need to feed it from unbalanced (RCA) sources an RCA to TS adapter cable can be used in those connectors.

DB Pages: Balanced Audio

 

[Deleted member 46664]

Are any amps configured as a current source? Audio amps are (to my knowledge) always voltage sources.

Ohm's law ... current is the result of applying a voltage across a load.
All amplifiers are voltage sources... but they also have to deliver the current to back that up.

No voltage ... no current.

 

[Deleted member 46664]

The LA90 is designed as an amplifier for balanced input only. The one in the photo cannot be used.

If that's the case then using the combination input connector was a serious mistake.

The output is single ended class AB... there has to be an internal balanced to unbalanced conversion to drive it. Might as well do that right at the input connectors and get the full benefit of noise cancelling on balanced interconnects.