Topping LA90 Discrete Amplifier Review

[babadono]

And the 12V trigger? Is it AC/DC or only DC. I was going to power sequence these amps just by shutting on/off the AC input. But they don't remember what state they were in when AC is cut and then reapplied. They just come up off.
I emailed Topping, waiting for a reply.

 

[babadono]

Topping says on vacation until April 6th or 7th....

 

[babadono]

I will go forward assuming the trigger must be DC only. I will apply AC to amps then a few seconds later apply the trigger. My DIY power sequencer is up to the task

 

[adLuke]

I thought about that also... but they were on sale at -13% so I figured what the heck. I do know that I am exhausting my 40W per channel amp trying to keep up with the bass and mids of my speakers. They are very efficient whereas the AMTs not so much. What the heck this is a hobby, right?

Can I bother you to tell me where is the sale? Tank you very much in advance

 

[babadono]

the sale ended sometime last week. Perhaps end of March.....something tells me there will will be another.

 

[babadono]

Heard from Topping...trigger is 12v DC only.

 

[adLuke]

the sale ended sometime last week. Perhaps end of March.....something tells me there will will be another.

The saly was on Topping own website?

 

[babadono]

The sale price was on every website that I found selling the Topping LA90. I was definitely looking for the best price. I don't recall if I checked on Topping's own site.

 

[babadono]

OK so I know there are people here a lot smarter than me and more familiar with these amps. Why would a jumper be needed between the two negative outs to use in "mono" mode? The two terminals are already shorted to the chassis and therefore each other. What is an additional wire going to do?

 

[babadono]

Topping finally responded after me prodding them twice:
Hi,


This connection is for DC protection.


UH OK ........DC on outputs?

 

[babadono]

Hi,



The 12V trigger is supposed to detect voltage jumps.









Best Regards,

	service
[email protected]

 

[babadono]

I think something lost in translation. I asked if the 12v trigger is a constant 12v for on and 0v or open for off. Or if it needs to be pulsed. I can report from my own now finished implementation that it is a constant 12v for on and remove the 12v and the amps turn off.

 

[nagster]

>7Vrms.

The exact value I've only ever seen @nagster test, though I don't think he's taken a look at the LA90D yet.

I noticed your post the other day, and today I posted the LA90 THD ratio vs generator level graph in the LA90 thread.
I don't have a LA90D, but the input section may be similar.

Topping LA90 Review (Integrated Amplifier)

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

www.audiosciencereview.com

 

[mike7877]

Dang, the built in volume control wasn't measured

 

[staticV3]

Dang, the built in volume control wasn't measured

L7Audiolab measured the volume knob's impact on the original LA90 at 5W/4Ω:

Source: https://www.l7audiolab.com/f/topping-la90/

Roughly the same impact can be expected with the LA90D.

 

[babadono]

I'm using a pair of these LA90Ds to run my Heil AMTs as the tweeters in a actively crossovered tri amp setup. I have a pair of AMTs on each the Left and Right wired in series so an 8 ohm load. Each amp is bridged, low gain with volume control about 11 or 12 o'clock to keep "no signal" noise/hiss as low as possible. All I can say so far is Wow, just wow.

 

[babadono]

Perhaps if/when they go on sale again I may purchase another pair to run the mids as well.

 

[Reddoc]

a pair of these LA90Ds to run my Heil AMTs as the tweeters in a actively crossovered tri amp setup

Sounds fascinating- have you got a "My System" page that we can see, babadono?

 

[babadono]

Pics or it didn't happen I'm kinda new around here post/knowledge wise, do I add a "My System" to my profile?

 

[mike7877]

L7Audiolab measured the volume knob's impact on the original LA90 at 5W/4Ω:
View attachment 365547 View attachment 365548
Source: https://www.l7audiolab.com/f/topping-la90/

Roughly the same impact can be expected with the LA90D.

Nice.

Check this out:

50mV -83dB THD+n

SNR has to be higher than THD+n. In this case I don't know by how much, but for fun let's say the noise is at -87dB compared to signal - puts it pretty high up there in the ASR chart of headphone amps (best being 95 except for the L30 II)... We already know the thing sounds good- at this point, might as well make a 2x speaker wire (terminated with banana plugs) to female 4 pin XLR connector and use the LA90(D) as a headphone amp! Comes complete with volume control lol