Topping LA90 Discrete Amplifier Review

[terryforsythe]

Amplifiers respond to input signal , if the input signal is substantially less than the sensitivity manufacturers state, ( being only 0.316V RMS from conventional sources ), then figures of output power are also less. Not factoring that in is what I am meaning.

The LA90D has balanced XLR inputs. Correct me if I am wrong, but balanced XLR is somewhere around 4 Vpp, which is roughly 1.41 4.2 Vrms. So, I would presume a good balanced XLR source will provide a maximum output somewhere around that voltage.

EDIT: I was incorrect. According to the review posted below by antcollinet, XLR is 4.2 Vrms, not 4 Vpp.

Now, if someone is using an RCA - XLR adapter without some type of voltage correction, the voltage will be lower, perhaps around 0.7 Vrms max.

 

[antcollinet]

Amplifiers respond to input signal , if the input signal is substantially less than the sensitivity manufacturers state, ( being only 0.316V RMS from conventional sources ), then figures of output power are also less. Not factoring that in is what I am meaning.

Why do you think I am not factoring that in?

Selectable gains simply allow you to match better based on the output voltage of your source.

Well I've just put a loundess meter on the track I'm currently playing - and "true peak max" is showing as -0.2dB

So assuming 0dB represents full scale, this track outputs instantaneous peaks of essentially full scale - which is presumably 2V for a 2V output device.

Of course - on average it is going to be significantly lower than this - but that is not the point. We don't want our amp to be clipping on the peaks, either.

(Next track is half way through and has hit -2.1dB - this by the way is sedate female vocals) Ended at -1.3dB

Third track straight in at -3.5, now at -2 after 20seconds. After 1 minute, -0.9

Most DACS will output a 2V RMS sinewave at full scale. My experiments with the loudness meter show that most music is approaching full scale at the transient peaks. So for the duration of that peak will be outputting close to 2V

Of course - the average RMS of a music track is much lower than that - typically 10 to 20dB lower if the loudness isn't brickwalled - but we also don't want to run our amp at an average of full power. We want to be able to output 2V (peak transients) from our DAC without the amp clipping.

We want a power rating of an amp - not so we can run it at that level continuously - but so we can run it continously 10-15 db lower than that (or less) without our transient peaks audibly clipping.


See the most recent DAC review here - with 2V output on RCA and 4V output on XLR

TOPPING D90 III Sabre DAC Review

This is a review and detailed measurements of the TOPPING D90 III Sabre balanced stereo DAC. It was sent to me by the company and costs US $899. As you can see, the design is what we have know about most of the Topping products. I do wish at this price that we had a high resolution display that...

www.audiosciencereview.com

 

[WeekendWarrior]

Interesting development...my LA90 started to sound odd...a bit "fuzzy", cymbals sounding watery and ill defined so I sent it back to Electromod UK. Just had a call with them and was told that one of the boards was delaminating! It's 18 months old and he's replacing it with a new LA90D. I only sent it back on Monday and replacement likely to be here tomorrow (Thursday). Kudos to Electromod UK for great service and replacing it under their 2 year warranty and all done completely hassle free.

 

[renaudrenaud]

Each time I come here and read few pages, I sadly find a new reason for avoiding this product.

 

[WeekendWarrior]

Each time I come here and read few pages, I sadly find a new reason for avoiding this product.

I think my case would probably class as a random failure that happens from time to time rather than anything systematic...and as far as I know the original LA90 is pretty reliable. However that doesn't seem to have been the case for the early versions of the LA90 Discrete, fingers crossed they have fixed that 'cos it's a great sounding amp, and IMO good value for money.

My previous post was mainly intended to compliment the after sales service, which has been subject to criticism on here.

 

[renaudrenaud]

I think my case would probably class as a random failure that happens from time to time rather than anything systematic...and as far as I know the original LA90 is pretty reliable. However that doesn't seem to have been the case for the early versions of the LA90 Discrete, fingers crossed they have fixed that 'cos it's a great sounding amp, and IMO good value for money.

My previous post was mainly intended to compliment the after sales service, which has been subject to criticism on here.

I guess the original LA90 is no more on the market. Maybe I should buy one Discrete anyway, found around 550€... Here, in China. In the country the occidental abstract concept of warranty is not well understood.

 

[Waddles]

I'm sorry if this has been discussed already, I had a quick look through but wasn't able to find out exactly.

I have one of these amps for some 8Ω (no idea what the minimum is) speakers and it's been great. However, I was thinking about getting a new set of speakers which have a bit lower sensitivity and notably a minimum impedance of 3.4Ω (nominal 6Ω, according to the manufacturer)

Since they're lower sensitivity, I was considering getting a second one to use in bridged mode as a mono block to make up the difference, but I'm worried that I could run into a current limit.

I'm not too familiar with the specifics behind this, but my understanding is that in bridged mode, these speakers could potentially present a 1.7Ω load.

That seems like it could be pretty far out of spec, and I don't want to stress the amplifier. Would the LA90 Discrete be able to handle that? It's unlikely I'd be running it at full tilt, and obviously this is the minimum impedance at a specific frequency (about 170hz.)

Edit:
I ended up reading the whole thread, and this got asked but not really answered. I did see one person mention they were using this amp as a mono block with the KEF R3, which has an even lower minimum impedance (3.2 ohms) - but also that their unit failed.

I'll try it in stereo mode when I get the speakers and hope there's enough power.

 

[babadono]

To be clear on my part...bridgeable into 4 ohms? With the provided wall wart(desk wart) supply?

 

[babadono]

Took a little searching...but Topping website says in mono(bridge) minimum impedance 8 ohms.

 

[Power Pop 23]

Took a little searching...but Topping website says in mono(bridge) minimum impedance 8 ohms.

I could be wrong......

I thought the newer, discrete version, the Topping LA90D, supported 4 ohms in bridged mode with 8 ohms being the recommended impedance for the earlier 'LA90' in bridged mode.

 

[terryforsythe]

I could be wrong......

I thought the newer, discrete version, the Topping LA90D, supported 4 ohms in bridged mode with 8 ohms being the recommended impedance for the earlier 'LA90' in bridged mode.

You are correct.

 

[terryforsythe]

To be clear on my part...bridgeable into 4 ohms? With the provided wall wart(desk wart) supply?

Yes.

LA90 Discrete Power Amplifier-TOPPING

 

[babadono]

Yes somehow I was on the non discrete data sheet where it stated only 8 ohms....please forgive me...should state no longer available also...

 

[babadono]

So... how long lived at 4 ohms bridged? I guess only time will tell.

 

[terryforsythe]

Edit:
I ended up reading the whole thread, and this got asked but not really answered. I did see one person mention they were using this amp as a mono block with the KEF R3, which has an even lower minimum impedance (3.2 ohms) - but also that their unit failed.

So... how long lived at 4 ohms bridged? I guess only time will tell.

Considering Waddles' edit, personally, I wouldn't try it with a speaker that dips down to 3.4 ohms without first contacting Topping to verify it that a minimum impedance of 3.4 ohms will be not be a problem.

 

[babadono]

So I really want to jump for one of these amps to drive the tweeters in a 3 way active setup. The tweeters are Heil AMTs currently and are rated 4 ohm. I want the lowest noise most reasonably priced amp I can get. So these have been around for about a year +/-. How reliable are they or are they not? Doesn't the designer/engineer frequent here? What is the true failure rate?

 

[babadono]

And not that I will do so but...can a RCA female to 1/4" TS adapter be plugged into the combi jack thus making it an unbalanced input that will then accept an RCA type cable. Most other balanced inputs work this way but I don't know Toppings circuit topology.

 

[babadono]

Well I jumped....two coming my way to bridge and run my tweeters. I will see about reliability.

 

[antcollinet]

Well I jumped....two coming my way to bridge and run my tweeters. I will see about reliability.

I don't think bridging the amps for tweeters makes sense.

Energy levels in the tweeter are going to be around 20dB lower than in the bass and midrange, so the power is not needed there. Then in addition, by bridging, you are going to be increasing noise by 6dB.

 

[babadono]

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?