Fosi Audio LC30 Speaker/Amp Switcher & Meter

[soundwave76]

Hello, could you please specify what kind of system you want to include? What are the devices in front and behind? Are they all digital signals?

Two sets of Genelec SAM speakers. AES digital signal fed to both, sources Bluesound Node 2i and a PC/Mac.

 

[Ropeburn]

Silly idea: get a really cheap chip poweramp for 20 moneys or so, just to drive the LC30's meters.

 

[peng]

I would like to ask in what scenarios can voltage or current be displayed?

I am not sure if I understand the question correctly. Below is an example of a VU meter, that basically displays voltage, but in VU, ie volume unit form:
For current display, I don't recall seeing one on an audio amplifier, that's too bad as it isn't hard to do. However, as long as there is a true (such as McIntosh's iirc) power (Watts) display as well as voltage display simultaneously, the information is there, but if only power is displayed then it isn't useful and that's my only point.

 

[kokono]

I was using this Fosi for some time, aesthetically the only complaint is that the moving arrow is too thin, you can't see anything moving from more than 1m. I have the black version.
Yesterday one of the amplifiers became very hot, sound was heavy distorted at loud volumes and no sound at normal volume, but no protection was engaged. It was like the iddle current was set to max.
I disconnected it, and have to check, but is there any way the amp switcher has caused this. Fosi and the other amplifier are ok.

 

[DrCWO]

but is there any way the amp switcher has caused this. Fosi and the other amplifier are ok.

I have no idea how this box should be able to create this issue.

 

[Sjkrabbe]

Silly idea: get a really cheap chip poweramp for 20 moneys or so, just to drive the LC30's meters.

then why not just have a line level meter then - like one of these

 

[Sjkrabbe]

then why not just have a line level meter then - like one of these

Silly idea: get a really cheap chip poweramp for 20 moneys or so, just to drive the LC30's meters.

OR this one if you actually want one that is useable - i have this both at home and at work - great tool

 

[Ropeburn]

OR this one if you actually want one that is useable - i have this both at home and at work - great tool

That seems cool and useful, and doesn't cost the world either. Unfortunately no analog input. Unusable for me.

 

[Sjkrabbe]

That seems cool and useful, and doesn't cost the world either. Unfortunately no analog input. Unusable for me.

I use it in an analog domain as well - I connect it via a cheap ADC as the analog input for it - like this - see attached file

 

[Ropeburn]

Got one today - several discounts on Amazon yesterday (sadly gone today) amounting to 122€.

Looks nice, feels nice, hooray jumping needles! 9/10* shiny object. One point deduction for being suspectible to fingerprints.

Solid enough speaker terminals, works exactly as it should. Remembers settings after turning off. Sensitivity adjustment range is big. Remote with speaker/amp toggle allows for true blind testing: tape over the indicators and you won't know which is which. Very nice. Audibly transparent like a piece of wire. 9/10* usefulness and handling - would've liked a default connection when powered off. Otherwise, perfectly fine in use.

Look at it sitting there, like a fat spider in her cable net

 

[Ndelato]

Check this out from BobWire. I'm planning to get one to switch 2 amps to a single set of speakers.

Amazon.com

Check this out from BobWire. I'm planning to get one to switch 2 amps to a single set of speakers.

Amazon.com

Hi, thanks for the recommendation. I’m curious if you ever got this, and how you like it. I need a switch for the same reason as you and I don’t need the meters.

 

[Ndelato]

Oh boy! I already had this connected to a Parasound A21 (ss) with 400 watts per channel at 4ohms (way over the 250 max ) and to a tube amp. Good thing I read this review and all the comments before I turned it on! I got this to use it as an amp switch, not just for the cool factor. It looks like the BobWire is what I need. Stupid question: if I do use this just as the toy that it is, how do I connected it in parallel like Amir did on the test without running the signal through it? Any help is appreciated .

 

[Ropeburn]

Oh boy! I already had this connected to a Parasound A21 (ss) with 400 watts per channel at 4ohms (way over the 250 max ) and to a tube amp. Good thing I read this review and all the comments before I turned it on! I got this to use it as an amp switch, not just for the cool factor. It looks like the BobWire is what I need. Stupid question: if I do use this just as the toy that it is, how do I connected it in parallel like Amir did on the test without running the signal through it? Any help is appreciated .

It's not like you're gonna blow it up the moment you turn your amp on. Are you ever even using those 400W?

And parallel is just that, parallel. You run speaker cable to its input, from the amp and additionally to the speaker connection.

 

[Ndelato]

It's not like you're gonna blow it up the moment you turn your amp on. Are you ever even using those 400W?

And parallel is just that, parallel. You run speaker cable to its input, from the amp and additionally to the speaker connection.

Thanks for responding! You’re probably right . I rarely ever listen over 85 db, so I should be ok? So just to confirm, two cables from each amp terminal, one to each Fosi terminal and one to each speaker? I’d have to use a spade and a banana connection to each amp terminal, correct? Or bare wire + banana or spade? Basically different connections at the amp terminals? Thanks

 

[Ndelato]

It's not like you're gonna blow it up the moment you turn your amp on. Are you ever even using those 400W?

And parallel is just that, parallel. You run speaker cable to its input, from the amp and additionally to the speaker connection.

I’ve been listening and switching all morning with no issues .

 

[ziggurcat]

Conclusions
The LC30 from Fosi brings us a high quality fun meters with switching ability. If you just want dancing meters, I suggest tapping from the amplifier speaker binging to LC30 and not routing your signal through it. That's the way I would use it.

I know this is a few years old, but (visually) what would that connection path look like?

 

[darrylhopkins]

I know this is an old thread, but I'm bumping because I wanted to share my displeasure with the marketing copy that Fosi Audio uses about the LC30, specifically:

Effortlessly Switch Between Two Sets of Amplifiers/Speakers
It streamlines the process of A/B comparison testing for two amplifiers or speakers

and

390Ω Load Resistors
Designed to prevent amplifier no-load conditions, guaranteeing stable operation and extending lifespan.

and:

Supported Amplifier Types: BTL, Class A, Class B, Class AB, Class D and tube amplifiers, etc.

But as https://www.audiosciencereview.com/...-amp-switcher-meter.57415/page-5#post-2110513 described here by LMac, and I confirmed it with my own digital multimeter, there is no load protection at all for the un-selected amplifier connected to the LC30.

I use the LC30 as an amplifier switcher so I can connect my home theater receiver and my separate hifi tube amplifier to the same speakers. Makes it a lot easier to manage, no cable swapping. The concern I had about amplifier switchers was the risk of running an open load on my tube amp. I bought the LC30 in part because to the promise that it is "designed to prevent amplifier no-load conditions" to quote their own product description.

But it falls short of that promise.

The only protection is if there is no speaker for the selected amplifier (A or B). The other connected amp is left with an open load.

So, if you are going to use this product and connect one or two tube amps to it, never use it to run A|B tests where you have both amplifiers powered on and switch back and forth. And, every time you turn on your tube amp, make certain the LC30 is switched to the amp you are going to turn on. Do NOT be lulled into a false sense of security that the LC30 is going to protect you from human error. IT WILL NOT.

Thankfully I haven't learned this lesson the hard way. I only discovered this flaw because I had a nagging worry about the LC30's "390Ω Load Resistors" boast and wanted to verify on my own. After I discovered the gap, I did some internet searching about that, and found this thread.

Fosi Audio should explain this common scenario more clearly and openly in their product description and literature.

 

[DrCWO]

never use it to run A|B tests where you have both amplifiers powered on and switch back and forth.

Hmm, never measured that but I have a Hypex NCx500 and a cheap Chinese pentode push pull tube amp.
Switching back and forth hasn't destroyed either of the two amplifiers so far. Lucky me

Thanks for your input anyway. I'll try to look into it and verify when I get the chance.

Best DrCWO

 

[darrylhopkins]

Hmm, never measured that but I have a Hypex NCx500 and a cheap Chinese pentode push pull tube amp.
Switching back and forth hasn't destroyed either of the two amplifiers so far. Lucky me

Thanks for your input anyway. I'll try to look into it and verify when I get the chance.

Best DrCWO

What LMac and I have both independently confirmed is the un-selected amplifier receives an open load. How the open load affects the amplifier can vary for each amplifier and its design. If in doubt, I wouldn’t hook up a tube amp to the LC30 unless you always make it the selected amp.

Here is an extract from a manual for one tube amp. Most tube amp manuals have similar cautions:

Never turn on your amplifier without speakers connected to the proper output load impedance terminals. Operation of the amplifier without a speaker load or an open circuited loudspeaker voice coil can permanently damage the output transformers as well as other major components. To be safe, always ensure your speakers are connected before plugging amplifiers into an outlet. Likewise, always unplug the amplifier from the outlet before removing the speaker load.

It’s good to hear your amp is fine. Maybe the transformer’s insulation margin wasn’t exceeded, or just didn’t hit the worst case moment (hard clipping at the instant of switching) yet. I’d treat “hasn’t happened yet” as luck rather than as evidence it’s safe.

 

[DrCWO]

Here is an extract from a manual for one tube amp.

I bought it used and for those cheap Chinese products there is no manual