Topping LA90 Review (Integrated Amplifier)

[Ziofrenko]

As always it depends on how sensitive the speakers are, the maximum SPL you expect and the listening distance... And clearly from the environment!

 

[nagster]

This is a graph of THD ratio versus generator level. This is for checking the allowable signal level of the LA90 input section.

 

[staticV3]

This is a graph of THD ratio versus generator level. This is for checking the allowable signal level of the LA90 input section.

Thank you for the measurements!

So basically, the LA90 has an effectively un-clippable input. Nice!

Also relevant to @babadono I believe:

Also anybody know the maximum input level before clipping the input stage?

 

[babadono]

Please educate me... how does this show that the input is unclippable? Do you mean that it is always the output section that clips before the input? The input still must have a limit though, correct? All I want to know is the maximum signal input say +20dBu or whatever it might be. On the semi pro gear that I am interfacing with these type of specs are given. Both input and output.

 

[babadono]

Oh and an input impedance spec would be cool too.

 

[staticV3]

Please educate me... how does this show that the input is unclippable? Do you mean that it is always the output section that clips before the input?

Correct.

The input still must have a limit though, correct?

Not necessarily. A simple passive attenuator has no clipping point as-such.

All I want to know is the maximum signal input say +20dBu or whatever it might be.

With the LA90's volume control bypassed, you can input 6.9Vrms (=19dBu) in Low gain, or 2.2Vrms (=9dBu) in High gain, before the Amp's output clips.

With the volume control engaged however, even 25Vrms (=30dBu) is not enough to cause clipping, provided that you set the LA90's volume knob low enough to avoid clipping the output.

 

[babadono]

So the "volume" knob is a dual differential passive attenuator? Now I REALLY want to take one apart

 

[nUUK25]

I've had just one LA90 for some time (July) and realized that with two the sound might be less constrained. Two month ago I've bridged (mono) two amps, one for each speaker and it works wonders in terms of the past 'constrainment'. Definitely an audio quality ascent ! Now I'm thinking I might gain some improvement with another two LA90 in the setup as my Martin Logan Electromotion speakers are bi-amp capable. I doubt the improvement will be proportional; two to four, but even less are welcome ! The fact that one amp will be dedicated to the electrostatic section and another amp to the dynamic section in itself might reveal more clarity. If I do go for it I will report back here !

A lot of time has passed - Well, not a surprise ! 4 are better than 2 - it is worth it !!

 

[SashaR]

I ask for the help of experts!

How to use the Topping D90SE and Topping LA90 kit with the greatest efficiency?

1. The D90SE DAC should be used in DAC mode, WITHOUT volume control, - and the LA90 amplifier should be used in volume control mode.
2. The D90SE DAC is used as a volume control - and the LA90 amplifier is switched to the mode WITHOUT volume control.

USB cable comes to the input of the DAC, and 4-ohm speakers with a sensitivity of 88.5 dB (Vela 408) are connected to the output of the amplifier. The interblock cables are XLR.


Thank you very much!

 

[antcollinet]

I ask for the help of experts!

How to use the Topping D90SE and Topping LA90 kit with the greatest efficiency?

1. The D90SE DAC should be used in DAC mode, WITHOUT volume control, - and the LA90 amplifier should be used in volume control mode.
2. The D90SE DAC is used as a volume control - and the LA90 amplifier is switched to the mode WITHOUT volume control.

USB cable comes to the input of the DAC, and 4-ohm speakers with a sensitivity of 88.5 dB (Vela 408) are connected to the output of the amplifier. The interblock cables are XLR.


Thank you very much!

Audibly it won't matter. But operating the DAC in DAC mode, and controlling the volume on the amp will give you the best technical SNR.

Plus that method protects you from the (pretty unlikely event of the) DAC spitting its dummy and putting out full volume.

 

[SashaR]

Audibly it won't matter.

But they have very different "structure" of distortions and reasons of them! The different superposition MUST be matter - maybe even audible (for example, Topping ask me to prefer the DAC mode of the D90SE).

controlling the volume on the amp will give you the best technical SNR

This aspect - the best technical SNR - is the kind of the effect which I loock for! BUT much-much more I'm interested in the minimizing of all other artefacts (intermodulation distortion, harmonics, etc.)... Which superposition will better in this matter?!

I was told that the LA90 volume control does not work well (distorts at the low volume levels at which I use it) - and this is one of the main reasons why I started looking for a way to improve the situation - and that's why I want to replace the LA90 volume control with the GOOD DAC's volume control!

I was suggested to use a headphone amplifier with a relay volume control - but I don’t need headphones, and, besides, an additional hardware module will definitely lead to sound deterioration ("technical" as you put it. Or even audible?)

Thank you very much!!!

 

[antcollinet]

Which superposition will better in this matter?!

Other than the possible low volume issue you have mentioned, it will make absolutely no difference.

I think the low volume issue you mention will be channel imbalance - possibly non linearity if at very low volumes. In this case, then yes you will be better off using the DAC volume.

If you are going to do that, I'd suggest turning the DAC up to full, setting the amp volume to the maximum you could ever want to listen to (or alternatively the maximum safe level for your speakers), and then use the DAC to turn it down from there.

 

[SashaR]

I'd suggest turning the DAC up to full, setting the amp volume to the maximum you could ever want to listen to (or alternatively the maximum safe level for your speakers)

Thank you very much for your advice!
But please forgive me for the stupidity of my clarifying question:
Will switching the amplifier to “direct” mode (bypassing the volume control using a switch on the back of the amplifier) be the correct implementation of your recommendation (my speakers have more than twice the power reserve compared to the maximum power of the LA90 amplifier)?



Please tell me in which mode is it better to use D90SE? With the 5-volt version, I set the D90SE to -35 dB as the “central” point of the “volume control” - but in Amir’s measurements it is clear that the local minimum of SINAD is achieved at 2.5 Vrms (in the 5V mode)... How can you make the D90SE work in the best area of SINAD, varying the settings of the DAC - at what decibels on its screen do I get closer to the least DISTORTION and at what its mode (5V or 4V) ?

https://www.audiosciencereview.com/forum/index.php?attachments/topping-d90se-thd-n-vs-level-measurements-balanced-usb-dac-png.135764/

 

[SashaR]

This is a graph of THD ratio versus generator level. This is for checking the allowable signal level of the LA90 input section.

Is there a similar graph for the TOPPING D90SE DAC (THD as function of the dB-on-the-screen) in its "PRE-amplifier" mode - and anything about its DAC mode to be able to comare with PRE mode?

 

[nagster]

First of all, my English ability is that of a 3-year-old. Please don't be offended.
I'm using Google Translate but I don't understand it well. Is this link helpful?

Cheap but non-degrading solution to add volume control between dac and amp.

I've got a Yamaha AVR as a 2.1 amp, set the AVRs volume level to "0db", use a Topping L30 as volume control, works great.

www.audiosciencereview.com

What is "PRED-amplifier mode"?

 

[nUUK25]

I ask for the help of experts!

How to use the Topping D90SE and Topping LA90 kit with the greatest efficiency?

1. The D90SE DAC should be used in DAC mode, WITHOUT volume control, - and the LA90 amplifier should be used in volume control mode.
2. The D90SE DAC is used as a volume control - and the LA90 amplifier is switched to the mode WITHOUT volume control.

USB cable comes to the input of the DAC, and 4-ohm speakers with a sensitivity of 88.5 dB (Vela 408) are connected to the output of the amplifier. The interblock cables are XLR.


Thank you very much!

What works perfectly for me: Ad2. Go to D90SE (in preamp mode) and the setup and set from 4 v to 5 v. Keep the low gain on LA90 and no volume - only set to high gain if you need more output from speakers. Just a tip about speaker plugs. Get the bananna plugs which are male tube shape : they will have a large contact surface on the plug in the speaker. Don't get the ones (male) which push the plug to the side in the speaker plug by a spring. They are all shit with less contact surface but quite common !

 

[SashaR]

What is "PRED-amplifier mode"?

Thank you! I have corrected this typo. I meant pre-amplifier.

Is this link helpful?

Thank you very much for the information! Do I understand correctly that we are talking about improving SINAD using the PRE-90, which is the most effective of all these "volume controls"?
Thank you again!

 

[SashaR]

tip about speaker plugs

Thank you for sharing !!! Now I use this way (D90SE in pre-amp mode).

The only difference is that I don’t use plugs, but screw the wire directly onto the speaker clamp nut: I’m not a pre-sales dealer and I don’t need to constantly reconnect cables between different amplifiers and different speakers.
Thank you again for your sharing!

 

[nagster]

Thank you! I have corrected this typo. I meant pre-amplifier.


Thank you very much for the information! Do I understand correctly that we are talking about improving SINAD using the PRE-90, which is the most effective of all these "volume controls"?
Thank you again!

Okay. I've never seen a THD sweep graph for the D90SE.
The graph in post-1208326 is a comparison measurement of SINAD when the volume is adjusted before the D90SE and when the volume is adjusted after the D90SE.
The settings for the D90SE are as written in the graph.

The connections are as follows:
AP => TOSLINK => D90SE => XLR 2m => Volume control device => XLR 2m => AP (200kohm)
AP => TOSLINK => D90SE => XLR 2m => XLR 2m => AP (200kohm)

About the measurement of the D90SE in "PRE mode".
A, The volume of the input signal is fixed at 0dBFS, and the volume is adjusted inside the "PRE mode D90SE". (Front panel or remote control)
B, The volume of the input signal is variable, and the D90SE is in "DAC mode"
In preliminary measurements, the SINAD of A and B was within the measurement error range. Therefore, we only plotted "B", where automatic sweep measurement by AP is possible.

 

[SashaR]

the SINAD of A and B was within the measurement error range.

Thanks a lot for your clarifications!

I don't really understand the meaning of the words "within the limits of measurement error" and would be very grateful for any information that could help me have an idea of the amount of intermodulation distortion created by the D90SE at different dB values (that it shows on its screen) - at several points within the range from -45 dB to -10 dB (and at -00 dB too - for comparison with the DAC mode).

Thank you very much again!