As far as I know X-Sabre has 6,8V output via XLR. Using digital volume control inDAC would result too much attenuation, worsening the sound. On another hand, volume control in LA90 is not good as well (bypassing is recommended). So, using preamp makes sense (DAC maxed, LA90 volume control bypassed).
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Topping LA90 Review (Integrated Amplifier)
- Thread starter amirm
- Start date
Ziofrenko
Member
I have similar setup:
PC with RME UCX interface set to +4dBu out (+13dBu at 0dBFS).
La90 set to low gain, volume bypassed, I listen in nearfield with KEF iQ30 (90dB) normally at -15dB volume setting from RME.
I need this because with no master audio material I am near to 0 volume out.
Wonderful amplifier, really!
mccririck
Active Member
Not sure. Maybe the Yamaha is trans.I am confused as to what the message is.
So I did some multiplication and division, and came to the realization the LA90 makes no sense (it could if the power supply was rated for 84VDC / 7.5A, but it's not....)
Example 1
Bridged mono: 95 watts into 8 ohms:
95 watts and 8 ohms needs 28VAC
28VAC peaks at +40 and -40V
Since the supply is 64VDC and this is a class AB amp:
Any rating over 64 watts should be impossible... but we somehow don't have 64, we have 95!
(Yes, I know this is bridged mono, but as there's only one supply and not dual isolated, Unless there's a beefy [noiseless] boost converter inside for use when running mono.....
Example 2
There's the 4 ohm measurement showing up to 50WPC comes out clean.
2x 50WPC 4ohms: with a 100% efficient class AB amplifier, that means 7.5 amps!
Since 7.5A is available to 4 ohms, it's also available to higher impedances. That is, until impedance rises so far that sufficient voltage is no longer available for it (power then becomes voltage limited)
With 3.75A put through two 8 ohm speakers (totalling 7.5A), power would be 112.5W x2
I'll check if we have enough voltage for that.
Unfortunately no, we don't - shy two volts! So 98 watts is what we should have, not 112.5.
Side note: (though not necessarily true) with voltage being higher and current being lower (by 0.5A), this 98w through 8 ohms should be cleaner than the 50w/ 4 ohm combination.
In the review 8 ohm only reaches 36W before clipping begins though! I want 98!!
Example 3
192W / 4 ohms in bridged mode is, again, 28VAC.
28/0.71 = 40 (+40 to -40 is +80)
So the included 64VDC power supply is insufficient.
Equally important: a single 28VAC output to 4 ohms making 192W means 7A!
Remember, the adapter's rating is for just 4 amps.
And remember, too, that the amplifier isn't some obscenity. It's essentially a standard AB amplifier optimized by people who cared about the outcome (they spent time swapping out components to find the best values, in the process learning how they all interact. Also they upgraded key components to higher grade when the choice made sense. Yes, that's all it takes to make something great. Too bad most good businesses don't last... they're bought out and then change direction to the new owner's agenda, or are just shut down so someone who's was starting to lose market share can continue selling their crap.
Final note: maybe the power supply drops from 84 to 64V when in stereo mode and 8 ohm loads are detected!
Let's find out:
64 / 2 = 32
32 * 0.70707 = 22.5
22.5 - 0.5 = 22 : 0.5V from external wire and connector)
22 - 2 = 20 : 2V from external and internal droop when wave in the >14VAC
20 - 2 = 18 : 2V for keeping some distance between the signal and the rails because if they ever meet, the transistor gets stuck there (in the on position) and your amp transforms into an unnecessarily expensive, heavy, and usually unregulated, power supply. What a waste!
Obviously I'm joking about the reason... which isn't important, but if you must know it's to avoid the area of operation very likely to contain distortion in most amps.
Ok! That leaves us with 18 volts, which is 4 watts more than the 36 Amir measured. So it's settled: the power supply has MPD: the same disorder many people, especially girls, on TikTok claim to have (but don't and it's obvious because real people (and PSUs) with MPD don't have multiple personalities simultaneously conscious in one body, they take turns controlling it and are unaware of the thoughts of the others - their only clue to their existence is losing time whenever their specific personality is not at the wheel. So Topping 64V 4A has at least one alter: 84V 7.5A...
Or maybe I'm just confused about how AB amps work. People these days are throwing clots left right and centre, maybe one came my way about 470 microns thick, just the size to fit into and block the capillary giving sustenance to the 724 neurons once dedicated to AB amplifier details (now dedicated to taking up space and off-gassing toxins while necrotizing. Protein factories remain transcribing corrupt and partial instructions,
slipped in surreptitiously by psychopaths. At first, normal cellular functions persist alongside, but after time, the toxic product begins doing damage locally. Often this damage is to DNA. Usually this slowly but surely ends the cell - all processes shut down one after another until it's just a protein factory. Myocardium cells, neurons, muscles, kidney - instructions were in nano sized industrial fats designed to cross the blood brain barrier, they're everywhere. Usually when the body's own cells start making toxins, the body attacks them. Usually it isn't all or most of the body's cell types at once (respiratory virus for example is in lungs). So when your body is busy killing thousands of all of its own cell types per day for years on end, autoimmune disprders begin (when the body attacks itself). Years on end? Some have lost both parents and all grandparents already - years if lucky.
Look up US military health statistics. In 2021, the average number of all types of diseases increased by 5x. That means the total from 2016 2017 2018 2019 and 2020 was about the same as 2021. Cancer. Autoimmune. Things like MS went from 400 per year to over 2000. Guess what's happening about it
I bought one of these amps, should be arriving from Shenzhen in a few weeks as long as geopolitics doesn't get in the way... I guess if it does I won't be too concerned about the quality of my music playback, will I? Lol
Example 1
Bridged mono: 95 watts into 8 ohms:
95 watts and 8 ohms needs 28VAC
28VAC peaks at +40 and -40V
Since the supply is 64VDC and this is a class AB amp:
Any rating over 64 watts should be impossible... but we somehow don't have 64, we have 95!
(Yes, I know this is bridged mono, but as there's only one supply and not dual isolated, Unless there's a beefy [noiseless] boost converter inside for use when running mono.....
Example 2
There's the 4 ohm measurement showing up to 50WPC comes out clean.
2x 50WPC 4ohms: with a 100% efficient class AB amplifier, that means 7.5 amps!
Since 7.5A is available to 4 ohms, it's also available to higher impedances. That is, until impedance rises so far that sufficient voltage is no longer available for it (power then becomes voltage limited)
With 3.75A put through two 8 ohm speakers (totalling 7.5A), power would be 112.5W x2
I'll check if we have enough voltage for that.
Unfortunately no, we don't - shy two volts! So 98 watts is what we should have, not 112.5.
Side note: (though not necessarily true) with voltage being higher and current being lower (by 0.5A), this 98w through 8 ohms should be cleaner than the 50w/ 4 ohm combination.
In the review 8 ohm only reaches 36W before clipping begins though! I want 98!!
Example 3
192W / 4 ohms in bridged mode is, again, 28VAC.
28/0.71 = 40 (+40 to -40 is +80)
So the included 64VDC power supply is insufficient.
Equally important: a single 28VAC output to 4 ohms making 192W means 7A!
Remember, the adapter's rating is for just 4 amps.
And remember, too, that the amplifier isn't some obscenity. It's essentially a standard AB amplifier optimized by people who cared about the outcome (they spent time swapping out components to find the best values, in the process learning how they all interact. Also they upgraded key components to higher grade when the choice made sense. Yes, that's all it takes to make something great. Too bad most good businesses don't last... they're bought out and then change direction to the new owner's agenda, or are just shut down so someone who's was starting to lose market share can continue selling their crap.
Final note: maybe the power supply drops from 84 to 64V when in stereo mode and 8 ohm loads are detected!
Let's find out:
64 / 2 = 32
32 * 0.70707 = 22.5
22.5 - 0.5 = 22 : 0.5V from external wire and connector)
22 - 2 = 20 : 2V from external and internal droop when wave in the >14VAC
20 - 2 = 18 : 2V for keeping some distance between the signal and the rails because if they ever meet, the transistor gets stuck there (in the on position) and your amp transforms into an unnecessarily expensive, heavy, and usually unregulated, power supply. What a waste!
Obviously I'm joking about the reason... which isn't important, but if you must know it's to avoid the area of operation very likely to contain distortion in most amps.
Ok! That leaves us with 18 volts, which is 4 watts more than the 36 Amir measured. So it's settled: the power supply has MPD: the same disorder many people, especially girls, on TikTok claim to have (but don't and it's obvious because real people (and PSUs) with MPD don't have multiple personalities simultaneously conscious in one body, they take turns controlling it and are unaware of the thoughts of the others - their only clue to their existence is losing time whenever their specific personality is not at the wheel. So Topping 64V 4A has at least one alter: 84V 7.5A...
Or maybe I'm just confused about how AB amps work. People these days are throwing clots left right and centre, maybe one came my way about 470 microns thick, just the size to fit into and block the capillary giving sustenance to the 724 neurons once dedicated to AB amplifier details (now dedicated to taking up space and off-gassing toxins while necrotizing. Protein factories remain transcribing corrupt and partial instructions,
slipped in surreptitiously by psychopaths. At first, normal cellular functions persist alongside, but after time, the toxic product begins doing damage locally. Often this damage is to DNA. Usually this slowly but surely ends the cell - all processes shut down one after another until it's just a protein factory. Myocardium cells, neurons, muscles, kidney - instructions were in nano sized industrial fats designed to cross the blood brain barrier, they're everywhere. Usually when the body's own cells start making toxins, the body attacks them. Usually it isn't all or most of the body's cell types at once (respiratory virus for example is in lungs). So when your body is busy killing thousands of all of its own cell types per day for years on end, autoimmune disprders begin (when the body attacks itself). Years on end? Some have lost both parents and all grandparents already - years if lucky.
Look up US military health statistics. In 2021, the average number of all types of diseases increased by 5x. That means the total from 2016 2017 2018 2019 and 2020 was about the same as 2021. Cancer. Autoimmune. Things like MS went from 400 per year to over 2000. Guess what's happening about it
I bought one of these amps, should be arriving from Shenzhen in a few weeks as long as geopolitics doesn't get in the way... I guess if it does I won't be too concerned about the quality of my music playback, will I? Lol
Its bridged to output so terminal + has to supply 14VAC ( +20 -20 swing) and the output terminal the same but inverted.
The output over the +/- is now 28VAC isn't it?
thecheapseats
Addicted to Fun and Learning
so what's happening is - you bought one of these amps? because of MS?... that's a heck of a punchline...
This.
Ziofrenko
Member
You have a lot of problems...
F1308
Major Contributor
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L
Will you try the other version ?
Let us know, please, as soon as it arrives and you start enjoying it...or not.
Will you try the other version ?
I am not going to check your calculations but let's assume they are 100% correct, you still have to consider the manufacturer's specs vs measurements. Specifically, the power output specs are:
90 Wx2 @ 4 ohm, THD+N <1%
50 Wx2 @ 8 ohm, THD+N <1%
180 Wx1 @ 8 ohm, THD+N <1%
So, if it measures better than those figures, you would have what you paid for.
As for voltage, as you know, it only needs 19 V to output the 90 W as specified, at less than 1% THD+N 19 V rms is about 53.7 Vpp and that is just below the 58 Vpp @ 4 ohm that Topping specified in the owner's manual.
Now, if higher than 1% THD is acceptable, then the measured output voltage and power output would of course be higher and the limit would again depend on the THD limit specified, and be verified by bench measurements.
Sokel
Master Contributor
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Thing is that according Amir's chart it shuts down way below 1% SINAD (at least at 20Hz).
restorer-john
Grand Contributor
Put the calculator down and measure some amplifiers.
You are completely ignoring voltage drops which increase with current drawn across OPT devices/emitter resistors/even supply cables and regulation (or lack thereof) in the PSU.
Bridge mode is mono mode right ?
At 1% THD normal mode it has 88W of power, which is more than half of what my X3700H provides, so I can assume that if i need power it's really not the amp to choose and will even be worth even if it's performance are perfect at low power right ?
At 1% THD normal mode it has 88W of power, which is more than half of what my X3700H provides, so I can assume that if i need power it's really not the amp to choose and will even be worth even if it's performance are perfect at low power right ?
If you need power, buy two of these, and use bridged mode.
manisandher
Addicted to Fun and Learning
Here are the power outputs for a single channel, according to Amir's measurements:
Stereo
36 watts into 8 Ohms
56 watts into 4 Ohms
50 watts into 2 Ohms
Bridged Mono
95 watts into 8 Ohms
192 watts into 4 Ohms
The LA90 seemed perfectly happy driving a 4-Ohm load in both stereo and bridged mono mode, according to Amir.
I have three LA90s. I use one as a stereo amp for my headphones, and a pair as monos in my office system. Very happy with all three.
Mani.
Yes, and these all make the case strongerPut the calculator down and measure some amplifiers.
You are completely ignoring voltage drops which increase with current drawn across OPT devices/emitter resistors/even supply cables and regulation (or lack thereof) in the PSU.
I'll measure when it arrives! Still hasn't left. Lazy buggers have only printed a label in almost 2wks
I saw some pics of internals, looks like bulk caps are nichicon 70v, maybe 10,000uf.
I have a couple nice 0-62V / 5A (linear) lab supplies I might try to power with
Wiki can help you out of your confusion : search for amp and bridged mode (versus paralel mode)
Do you have a link for these linear power supplies, thank you.
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