# Topping LA90 Review (Integrated Amplifier)

## Rate this amplifier:

• ### 4. Great (golfing panther)

• Total voters
784

#### Ingenieur

##### Addicted to Fun and Learning
Looking at the image it's set to 10v per graticule thus about 80v full scale. This puts 58 volts right about where the trace is on the right hand side of the display. That clipped peak appears to represent 74 volts. This also puts the lower level to the left at about 20 volts...

So 20 squared / 8 time 0.707 puts it at 35 watts average power ... with a peak at around 480 watts ... more than enough to make your years bleed. As I commented earlier I've worked on movie theatre equipment that isn't driven this hard.

I see it now:
The lower left is 16 V
The peak is 74, 74 - 16 ~ 58 (full scale)
the center line is 0, ~ 1 wave cycle
So -24 to 34 ~ 58 pk to pk
Full scale is 2 mS ~ 500 Hz for the partial wave cycle

V rms ~ 35/sqrt2 = 25 V
Assuming 8 Ohm ~ 78 W avg,
peak 156 W

With 89 dB speakers ~ 108 dB

#### F1308

##### Major Contributor
The apparent clipping is not the amplifier, but it is in the CD data. Tchaikowsky 1812 Telarc,
Telarc did that with those cannyons ????
Or when the bells were rung ?
All the time thinking it was my system and in fact was the CD !!!!

Last edited:
D

#### Deleted member 46664

##### Guest
Movie theatre is movie theatre. Have you also worked at a recording studio for classical music?

Only fixing the consoles.

Your average power estimation is based on a very short part of the track so it is pointless to indicate to listening level set. Below is the full track rip.
BTW I do not understand your calculations. Peak voltage is 35Vp (zero level is in the middle of the scope screen as usually) and 35Vpeak with 4ohm load would make 306.25W peak power. The impedance is in fact close to 6 ohm so it is less.
58.61V refers to 58.61Vpeak-peak on the whole screen .
It's been a long and difficult day ... I was a little off on that one.

#### Ingenieur

##### Addicted to Fun and Learning
I think I have that CD (the article referenced the lp).
I have a bunch of TELARC bought in the early 80's. I'm going to look for them tomorrow.

#### razamanaz

##### Member
To be more precise, the amp doesn't clip at 25 W for a 1 kHz single frequency sine wave with a crest factor of 3 dB, which is the test signal used in this test. With a signal (e.g music) that has a high enough crest factor, it will clip at 25 W or lower.
We are talking about the power of the sine, the power of music is an abstract thing. Amplifier gain 20dB, I use a DAC D30Pro -10dB volume, respectively 2V -> 20V and 25W at 8 ohms. I don't see where the clipping would appear?

#### infinitesymphony

##### Major Contributor
I'd like to think Topping took inspiration from my Bryston x Topping mashup:

And my Centered volume knobs thread:

(They didn't, but I'd like to think so. )

#### CedarX

##### Active Member
Forum Donor
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.
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)?

#### PeteL

##### Major Contributor
My apologies, for some reason I always associated your name with a youtuber that reviews/measures speakers with similar equipment as Amir's. As to your claims of conflation, 2 points. You raise the issue of RC in your post, and directly reference Dirac Live and ARC and you mention room correction, but you argue that I conflated the two. If you are going to make the argument of conflation, at least verify your post is not referencing RC.

As to limiting the argument to bass management, that actually makes your argument even more spurious. Bass management is extremely uncommon in stereo setups, and many arguments can be made on either side, especially in the context of where this amp does well. My argument does not change and your assessment remains lazy. The market dictates what is needed, is not the "mere existence of other crap integrateds" that dulls your argument, is the extreme rarity of integrateds with bass management that makes your argument questionable (i.e. that integrateds that do not include bass management are essentially failures). Moreover, if bass management is critical to a user, there are numerous ways of addressing this. At the risk of repeating myself, one can:

1. Use a PC as a source (and use numerous tools to address bass management)
2. Use a source that provides bass management
3. Pass the source through electronics that provide DSP prior to reaching the amp (I have a MiniDSP that provides Dirac for any HDMI source, this can easily be converted to analog and address bass management, system loudness could be addressed through the source)
3. Use speakers that have integrated DSP to address bass
4. Use speakers that do not need bass management (the use cases I discussed for this amp, make the necessity of bass management questionable, and most users would not want to pursue that path)
4. Alternatively, and for many users this is a preference, take steps to correct room issues, and use speakers that provide sufficient bass instead of using having to rely on bass management.

Again, my apologies for confusing you with the youtuber (btw, his reviews are generally excellent).
I think you are over complicating the issue... Even before you want to talk about DSP or "Bass Management" that seems to be synonym to you. First thing first. How do you integrate a sub? In the end they call it an "integrated amp", it has 3 inputs it has volume control. What kind of Bass management are you talking about exactly when you ask to fix it at the source? this has a volume control, you plan on using it or not? You go and enumerate 5 sentence (at risk of repeating yourself), but don't repeat yourself, explain what you have in mind? Preamp with a sub out with DSP in between with the preamp out in this? Your computer as a source, you connect it to this amp how if you want bass management? All your solutions of "One can" are extremely vague. In all cases, Volume control need to be before the sub and by consequent before DSP. How do you plan to do that?

#### tomchr

##### Addicted to Fun and Learning
Audio Company
Forum Donor
I have these speakers http://yb-audio.pl/realizacje/zephyr_le/ and a 2x25W amplifier https://neurochrome.com/products/modulus-186
Speakers distort at maximum volume (25W)
I'm not really sure why this shows up in this thread. If you have an issue with your Modulus-186, how about contacting me directly? You can do so via PM here, via email, or via the Contact Us form on the Neurochrome website.

The Modulus-186 will deliver 40-45 W into an 8 Ω load when powered by ±30 V. It'll deliver 60-65 W into 4 Ω under the same conditions. I use the point in the graph where the THD+N shoots up as the max output power spec, not the 1% THD+N or 10% THD+N that most other manufacturers use.

If you're only getting 25 W into 8 Ω from your Modulus-186, you're probably running it on ±24 V. Up the supply voltage to ±30 V.

To be more precise, the amp doesn't clip at 25 W for a 1 kHz single frequency sine wave with a crest factor of 3 dB, which is the test signal used in this test. With a signal (e.g music) that has a high enough crest factor, it will clip at 25 W or lower.
That statement makes no sense whatsoever.

Tom

#### Red@

##### Active Member
Iirc 20K.
Please guys can anyone explain what is lirc.
And can someone point me to the balanced inputs impedance ?
I know I asked the question many times. But I am surprised it is not concerning any of you as topping are having unusual input impedance in their amps.
I am interested in this Amp for my susvara. Hopefully the performance does not drop with 60ohms

#### Doodski

##### Grand Contributor
Forum Donor
On balanced inputs ?
What is lirc ? If I may ask
It means, "If I remember correctly."

The input impedance is stated to be ~20,000 Ohms. (20K Ohms)

#### Red@

##### Active Member
It means, "If I remember correctly."

The input impedance is stated to be ~20,000 Ohms. (20K Ohms)
Thanks for the clarification. but is it for rca or balanced as they're usually not the same

#### NTK

##### Major Contributor
Forum Donor
We are talking about the power of the sine, the power of music is an abstract thing. Amplifier gain 20dB, I use a DAC D30Pro -10dB volume, respectively 2V -> 20V and 25W at 8 ohms. I don't see where the clipping would appear?
The standard method of testing amplifier power is by using a single frequency sine wave, which has a crest factor (CF) of 3 dB. A 3 dB CF means that the peak voltage is sqrt(2) = 1.414 times the RMS voltage.

Therefore, for examples, if an amplifier starts clipping at 0.25 W into an 4 ohm load and it clips because it is voltage limited, the clipping voltage is 1 V RMS or 1.414 V peak (for a sine wave).

If the signal in not a single frequency sine wave, V_peak is usually not equal to 1.414 times the RMS voltage. Here I give an example of a signal with one component at frequency f1 and a second one at 2*f1. They both have the same V_peak of 1. Into a 4 ohm load, the total power of both components is: 2 * (1/1.414)^2 / 4 = 0.25 W.

If you have an amplifier that is tested using a single frequency sine wave and it clips at 0.25 W at 4 ohm, the clipping voltage is sqrt(0.25 * 4) = 1 V RMS, or 1.414 V peak.

In the worst case, the 2 component signal can have a V_peak of 2 V, and therefore will clip with this amplifier even though the power required of the 2 component signal is not more than its "rated power".

At this point, I will also appeal to authority and ask you to read the posts by @Charles Sprinkle.

#### Mnyb

##### Major Contributor
Forum Donor
The standard method of testing amplifier power is by using a single frequency sine wave, which has a crest factor (CF) of 3 dB. A 3 dB CF means that the peak voltage is sqrt(2) = 1.414 times the RMS voltage.

Therefore, for examples, if an amplifier starts clipping at 0.25 W into an 4 ohm load and it clips because it is voltage limited, the clipping voltage is 1 V RMS or 1.414 V peak (for a sine wave).

If the signal in not a single frequency sine wave, V_peak is usually not equal to 1.414 times the RMS voltage. Here I give an example of a signal with one component at frequency f1 and a second one at 2*f1. They both have the same V_peak of 1. Into a 4 ohm load, the total power of both components is: 2 * (1/1.414)^2 / 4 = 0.25 W.

View attachment 202945

If you have an amplifier that is tested using a single frequency sine wave and it clips at 0.25 W at 4 ohm, the clipping voltage is sqrt(0.25 * 4) = 1 V RMS, or 1.414 V peak.

In the worst case, the 2 component signal can have a V_peak of 2 V, and therefore will clip with this amplifier even though the power required of the 2 component signal is not more than its "rated power".

At this point, I will also appeal to authority and ask you to read the posts by @Charles Sprinkle.

Yes it’s typically not power with sine waves you need . The crest factor of some music can very high not at all square root of 2 ( 1:414...) as a sine test signal.

I tend to think about amplifiers as a voltage generator with a voltage limit and current limit .

You can clip your amp in either way or both depending on circumstances.

Amp applies a voltage over the speaker and current needed is decided by the impedance of the speaker at that signal .

I also tend to think about power needs in this way .

Small , 50wpc (8ohm) , 100w , 200w , omg ( kilowatts) .

My current active speakers have 225watt per speaker.

I’ve used 50 watt amps in the past with passive speakers, no problem, but if one wants sota performance I want to avoid driving an amp into clipping at all under any circumstance.

#### Mnyb

##### Major Contributor
Forum Donor
I would absolutely have used this amp with the circa 90dB pair of floorstander I had as a student .

#### theREALdotnet

##### Major Contributor
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)?

In the olden days you would use wire bridges to dial in any SINAD/power combination you wanted…

#### NTK

##### Major Contributor
Forum Donor
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.

yo

#### confucius_zero

##### Addicted to Fun and Learning
Now I just wish there was an RCA version of this.

#### Ra1zel

##### Addicted to Fun and Learning
~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

#### xrk971

##### Member
Audio Company
Amir said that the brick was +64V splitter/converter would be internal.
It depends which 2 of the 3 pins across are measured. Pick the +/-32 and you get 64.

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