Fosi Audio LC30 Speaker/Amp Switcher & Meter

[Old_School_Brad]

Just add 2 of those at $467 each and you are set

Just picture a company like Fosi here, creating something with the same capabilities packaging them into an attractive 430 mm device. They would likely succeed at a much lower price too.

 

[Ropeburn]

The way the remote control works has a nice side benefit: you can select between A/B and 1/2 directly, or using the toggle buttons.

That means it's usable for blind comparisons. Just tape over the indicator LEDs, press the amp/speaker toggles on the remote multiple times so you really don't know what is what anymore, et voilà! Blind testing.

 

[Sokel]

Just picture a company like Fosi here, creating something with the same capabilities packaging them into an attractive 430 mm device. They would likely succeed at a much lower price too.

Probably not too much lower if we add weight/size as they add a lot at shipping fees and proper western safety certifications (at a minimum) as a package like this cannot operate with a pre-certified brick.

 

[AaronJ]

Buy a non-working (mechanically) vintage cassette deck, put it in rec/pause and you have some really accurate line level meters. Many have peak hold, adjustable ballistics etc.

I stuck a Sansui QS-1 in my system for the meters because it also blends in with the rest of the gear. I was merely commenting on the development of so many speaker-level meters and don't understand the fascination when it’s even easier to do it at line-level. I guess people like wattage meters.

 

[Sokel]

I stuck a Sansui QS-1 in my system for the meters because it also blends in with the rest of the gear. I was merely commenting on the development of so many speaker-level meters and don't understand the fascination when it’s even easier to do it at line-level. I guess people like wattage meters.

Some times is practical.
My amps don't have watt meters but they have volt and ampere meters for each channel (icePower has this embedded in it's modules along with temp,etc)
It's easy to see if you have gone too far and dial a while back.

Edit:typos

 

[OldManMatt]

AMM-1

The Audio Multimeter and Handheld Dyno. Measure TRUE amplifier power! Measure impedance of speaker boxes. Measure voltage drops, and much more! The purpose of this tool is to enable the user to: Measure True Amplifier Power output into any load reactive or resistive Measure Common DC...

damoreengineering.com

Thank you for that link. Some very cool devices on that site.

 

[RCS]

I bought the original version of this when it first came out. Sent it back because the needles barely moved with the sensitivity maxed out. I had two ZA3 amps hooked up to it. (Really like the amps.) Unless I missed it, there is no info on the differences of the LC30-Y and LC30-B on the Fosi webpage.

 

[CrankTaintly1000]

I love this as a concept, but what a let down.

It look really good (my preference would be black meters with a white needle and white indicators), but the fact that it doesn’t actually measure anything and can’t be calibrated is a dealbreaker.

Hey, I’m not looking for the thing to be the ultimate in power amp metering, but it doesn’t sound like it really does anything at all other than bounce the meters around.

If it really doesn’t give me any idea what the power output of the connected amp is, really, what good is it?

I realize the meters on power amps have always been an approximation, but this isn’t even that.

It’s a damn shame.

 

[musicforcities]

Hey fosi:

Put two of the V3 mono blocks and the meters of this unit in a single case. (Power supply can be separate). Maybe follow the design language of the Luxman m4000 etc. but smaller.

Create option for a silver brushed anodized faceplate.

Please…hugs and kisses

 

[ryanmh1]

I love this as a concept, but what a let down.

It look really good (my preference would be black meters with a white needle and white indicators), but the fact that it doesn’t actually measure anything and can’t be calibrated is a dealbreaker.

Hey, I’m not looking for the thing to be the ultimate in power amp metering, but it doesn’t sound like it really does anything at all other than bounce the meters around.

If it really doesn’t give me any idea what the power output of the connected amp is, really, what good is it?

I realize the meters on power amps have always been an approximation, but this isn’t even that.

It’s a damn shame.

It's got to be basically just a voltmeter. That's the only way you're going to get one of these things to work, so they move in proportion to something and it has to be measuring something to move the meters. (Okay, fine, you could actually make it accurate by spending money on engineering for a peak sample and hold circuit, but like that's going to happen.) But who knows or cares what? I mean, it's marked with WATTS anyway, so like that's every going to line up to whatever your amp is. You can use the gain knob to have 0dB/100W be full output from the amp, then you have clip meters, sort of. But I probably wouldn't bother.

Really, though, if there was some sort of scale to grade gadgets on, I would give this is a B- next to the NEOHIPO which would get an A-. Who knows if its accurate either (doubt it), but the NEO has adjustable lights, bigger meters, a microphone to make the meters bounce (look ma! no wires!), and sensitivity and swing adjustments. The only thing this has going for it is a better looking meter faceplate. (Fair disclosure: I bought the NEOHIPO.)

 

[LugsyTL47]

Why get a toy?

 

[msmorgan]

FOSI AUDIO LC30 REVIEW
Mark S. Morgan – 09/24/2025



To be clear right up front, this audio component was provided by the manufacturer for my review with no expectation of return. Their only request was an honest and thoughtful review. I will do my best to oblige.

The Fosi Audio LC30 is a speaker and amplifier switcher which just happens to come equipped with a pair of left and right channel audio meters. I am of the audio enthusiast camp which enjoys the entire musical experience, including the visual aspect, and my position is that the more senses involved, the better. For that reason alone, this device already gets my opinion moving in the positive direction.​

​

On the switching front, the unit comes complete with the ability to select between two amplification sources and two speaker loads via the front panel buttons as well as the included remote control (batteries not included). Bi-wiring nor bi-amping are supported, which is inherent to the design, and only one source or one load may be active at any time. There is provision for controlling the amber back-light level for the meters in five steps, including off, and these functions are replicated on the remote, along with the obligatory power switch. On that topic, the LC30 is powered via an included USB-C cable, but you must provide your own power supply. It should also be noted that the LC30 must be powered on to pass any signals. The most important feature is the provision of variable meter sensitivity via a front panel (only) knob. This allows for the selection of satisfying meter movement at any listening level. Speaking of the meters, the 0dB point for the meters is labeled as 100W, presumably at 8 Ohms nominal speaker load. However, because of the variable sensitivity adjustment, this cannot be trusted as a true measurement. The manual gave no indication of what sensitivity knob position would provide accurate power indication. Power handing is rated at 250W per channel, again, presumably at 8 Ohms.​

​

On the positive side of the equation, we have a very attractive component with an impressive build quality that will likely look at home in most system setups. It is also quite reasonably priced, at $149.99, and has what I consider to be some of the most attractive audio meters available in almost any price category. The variable meter sensitivity adjustment allows compensation for varying listening levels while still providing plenty of visual stimuli, which I believe, is the entire purpose of the LC30.​

​

I installed the LC30 in my primary listening system which consists of a pair of Bowers & Wilkins 683 S2 speakers driven by a Denon AVR-X3100W A/V receiver, although I make no use of its surround capabilities. Sources were primarily streaming via Apple TV’s Music app over HDMI or vinyl via my Pro-Ject Debut Carbon turntable with Ortofon Ruby cartridge. As for the sound and listening impressions, I have very little to share, which is a good thing. I was unable to detect any audible difference between listening with the LC30 in or out of the audio circuit. I don’t have the ability to provide objective test measurements, but I would expect it to measure reasonably well and would have no problem leaving it in my primary listening setup full time.​

​

I do, however, have a few recommended improvements that would make this device a giant killer. The form factor of the switcher is narrower than full-size (typically around 17 inches) and so it may be difficult to stack with existing gear, except on top. I just happen to like my equipment to look coherent and would appreciate a wider footprint. While the sensitivity adjustment is certainly a very nice feature to include, it is only accessible from the front control panel. I might suggest providing three sensitivities (perhaps, 1, 10, and 100 Watts at 0dB) that could be switched from the remote as well. This would also allow for accurate power readings to be made from the meters. The only other addition I could imagine would be color selection for the backlight. Blue would certainly look quite nice and might get the attention of the boys in Binghamton.​

​

All told, I believe this is a very solid and attractive component. It’s functionality and sound impact can hardly be faulted, and it seems to be a great value. And I must admit, I love watching the needles dance to the sound of my music.​

 

[bumblebee657]

I'd prefer you use standard size font. This is really hard to read.

 

[bumblebee657]

Thanks! Much better now.

 

[LMac]

Picked one of these up a couple of weeks back and finally getting around to hooking it up & testing. I've gotta say it looks great and works well (can you say fun!), I particularly like the default Amp B to Speaker B connection when powered off, this really suits my setup well as I'll be using it as an amp switch.

Just did some testing to confirm the load on "the un-selected" amplifier since I'll be using it with a class A tube amp that shouldn't be operated with out a load (reflected impedance, high voltages, transformer insulation breakdown, tube damage, bla bla bla). Reading on Fosi's web site, they claim that there's a set of 390ohm resistors switched into the circuit to "prevent amplifier no-load conditions" but when I check resistance across the un-selected amplifier input with an ohm meter I see an open circuit. Yes, using a quality meter, recently calibrated Fluke 787 process meter. Tried this on both A & B amplifier inputs, unit powered on & powered off but getting the same results every time.

Also checked with a cheap LCR meter just in case they were capacitively coupling the load resistors in but not seeing anything, i.e. open circuit.

Has anyone else observed this with their LC30? Is it to be expected? Am I missing something completely?

Cheers, L.

 

[LMac]

Did some further testing and from what I can see the 390 ohm load resistors are switched in and out of the speaker terminals and not the amplifier terminals. Looking at a full set of resistance measurements (unit powered on, no speakers or amplifiers connected) we get these results (tested 1 channel only, results were the same on L or R channels):

From this, it appears the the unit has a 680 ohm load on the selected amplifier at all times (likely the feed circuit to the meters) and switches a 390 ohm load in parallel with the 680 (the 248 ohm readings) on the speaker side, but the speakers that the 390's are connected to are based on the un-selected amplifier - i.e if amp B is not selected, the 390's get connected to speaker 2, while if amp A is not selected, the 390's get connected to speaker 1.

If the intention is to connect the 390's to the un-selected amplifier then it looks like there is a a possible design error and the load resistors are connected to the speaker terminals instead. This could have a small affect on the impedance seen by the active amplifier as they will be in parallel with the speakers (in some cases) while at the same time leaving the un-selected amplifier with no load. This appears to be counter to their web site claim re. amplifier no-load conditions:

If the 390's were instead connected to the un-selected amplifier, I would have expected to see the following measurements:

I've sent this along to Fosi's online support, will update with their reply when it comes through.

Cheers, L.

 

[LMac]

Have gotten a response from Fosi's tech support (quick response BTW) and they confirmed what I had already figured out - i.e. the resistors are connected to the speaker terminals but are controlled by the amplifier selection. Here's Fosi's response:

Thank you for reaching out to us, I hope you are doing well.
The 390 Ohm resistor is designed to avoid no loading, and except for it, there is also 680Ohm with the VU meter.

When your amp connect to Amp A, then the 390 Ohm resister is on Speaker 2,
then you measure the impedance of Speaker 2 will be 248Ohm (because the 390 Ohm resister and the VU resister are in parallel);
and the impedance of Speaker 1 is VU resister 680Ohm (no 390 Ohm resister).

What your amp connect to Amp B, then the 390 Ohm resister is on Speaker 1,
so the measured impedance of Speaker 1 will be 248Ohm (The same reason as above);
and the impedance of Speaker 2 is VU resister 680Ohm (no 390 Ohm resister).

I hope this can help.

Why they did it this way doesn't make a lot of sense to me and have emailed them back to explain how this is "Designed to provide amplifier no-load conditions", still waiting on that reply.

In the meantime I'm calling this either a flawed design or a mistake when laying out the PCB.

Cheers, L.

 

[daVinci]

I can confirm LMac's statement and report other more or less serious shortcomings of this device. And here we are already talking about the improved second version, the first series probably had other problems such as a completely inadequate sensitivity. This problem has only been insufficiently improved in the “improved” version that I own.

But first things first, the problems start with the incorrect printing of the scale. It is clear that this is not an accurate “measuring device”, but the approach should be correct for such a not very cheap device. The current power is displayed in watts and dB. The reference is 0 dB / 100 watts. The power ratio is calculated as 10 * log10 ([current power] / [reference power]).
This means that in addition to the reference value, only -40 dB / 10mW is correct. All other values are printed incorrectly.

-50 dB should be either 1 mW or -49.2 dB,
-30 dB should be either 100 mW or -27 dB,
-20 dB should be either 1 W or -17 dB,
-10 dB should be either 10 W or -7 dB,
+4 dB should be either 250 W or +3 dB,
+6 dB should be either 400 W or +4.8 dB.

However, this device also fails to meet other basic promised features. The missing terminating resistor has already been reported. This is not a problem for digital or conventional transistor amplifiers, but can be fatal for a tube amplifier if you rely on the manufacturer's specifications.

The “measured values” displayed over the frequency are “different” than expected. The display over frequency is not linear with my device. The display value falls at low frequencies and rises at high frequencies.
This is inexplicable, as the greatest power is transmitted at low frequencies. Measurements were taken with a high-quality TRMS bench multimeter up to 100kHz. The outputs were loaded with 8 Ohm resistors.
The display of the channels is also slightly different here, which is not really a problem because, as I said, it is not a “measuring device”, but it is still remarkable. Here are the values I determined; reference 1000Hz. First column is the frequency in Hz, second column right channel in dB, third column left channel in dB.

20 -60 -60
50 -31 -29
100 -16 -15
200 -10 -10
500 -2 -2
1000 0 +0,2
2000 +0,2 +0,8
5000 +2 +2,5
10000 +3 +3,5
20000 +3 +3,5

Without a connected load resistor, the display increases by almost 1 dB. This should not be the case because the connected transistor amplifier has a very low output resistance. The output voltage was nevertheless measured and does not increase. The display should remain the same with or without load.

The transition resistances between the amplifier and speaker terminals are relatively high on my (new) device at 60-80 mOhm per channel. Not dramatic, but it remains to be seen how this will develop over longer periods of operation. 80 mOhm corresponds to 17 mOhm mm²/m after all. With a 4 mm² cable 4.25 mOhm/m this means ~9m of additional cable. The relays used do not appear to be of the highest quality and are probably not gold-plated due to the high contact resistance.
I have not tested them under high load. But it is to be feared that there will be effects at high output powers. After all, with the specified 250W at 4 ohms, around 8 amps flow. The initial posting by binirm shows clearly visible distortions in the 20 watt range and above.

The holes in the connection terminals are only 10 mm deep, but a banana plug has a length of 18 mm. This means that almost half of the plug cannot contribute to the contact and therefore increases the contact resistance if plugs are used.

There is no need to comment on the manual, it is really poor and needs to be comprehensively revised.

It must be stated that quality assurance has not taken place, or not to the extent required. And we are talking here about the improved version that has already been revised. The high-quality feel of the device and its great appearance do not make up for the lack of inner values. A lot of appearance, not much substance.

Naturally, I contacted Fosi support with all these points. They took a week to reply and initially questioned the validity of the points, only to admit a few emails later that the criticisms were correct.
The support team's basic statement that the device is merely decorative in its current state is the bottom of the barrel. You don't know whether to laugh or cry. As “compensation”, $10 was offered - for a new device that cost €170.

 

[davidgale]

I recently bought this thing. Primarily for the purpose to compare two different amps/speakers.
What I immediatelly noticed on my unit, the left channel power meter is not as "responsible" as on the right one. Clearly they did not bother to calibrate them. But this would not be a dealbreaker for me. The major dealbreaker (which I did not think about prior to buying) is total lack of possibility to trim (e.g. via resistors) output level to speakers.
Luckily I bought it via amazon. Returning tomorrow.

 

[NTK]

I recently bought this thing. Primarily for the purpose to compare two different amps/speakers.
What I immediatelly noticed on my unit, the left channel power meter is not as "responsible" as on the right one. Clearly they did not bother to calibrate them. But this would not be a dealbreaker for me. The major dealbreaker (which I did not think about prior to buying) is total lack of possibility to trim (e.g. via resistors) output level to speakers.
Luckily I bought it via amazon. Returning tomorrow.

Welcome to ASR.

Using a resistor network to pad down the amplifier output will significantly alter the output impedance of the amplifier as seen by the speakers, which can significantly affect the frequency response of the speaker/amp combination. That will invalidate your speaker comparison test.

It's much better adjust the signal levels at the input of the speaker amplifier(s).