I see Fosi Audio have a new Kickstarter project which looks nice:
I already backed it - will be handy for some A/B Testing
I already backed it - will be handy for some A/B Testing
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Fosi Audio LC30 Dual VU-Meters
- Thread starter Jeromeof
- Start date
I don't have a use for it but looks cool. What calls my attention is that in the video it seems to have a remote control. Being capable of switching sources and speakers with a remote is not a common feature I would say.I see Fosi Audio have a new Kickstarter project which looks nice:
I already backed it - will be handy for some A/B Testing
I hadn't considered the A/B switching aspect. That's actually pretty neat feature.I see Fosi Audio have a new Kickstarter project which looks nice:
I already backed it - will be handy for some A/B Testing
staticV3
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Voltage and current can be measured without knowing the Amp, or the speakers. Then you just multiply the two to get power.
cool little gadget. I’m in.
Middle Earth
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I am in on the Kickstarter but for the black dials version
Nice way to set up two small form factor amps and switch them back and forth.
Not for everyone obviously, but I am a Fosi Fan Boy.
I believe that one may be closing soon.
There are three Kickstarters going.
Nice way to set up two small form factor amps and switch them back and forth.
Not for everyone obviously, but I am a Fosi Fan Boy.
I believe that one may be closing soon.
There are three Kickstarters going.
I didn't see dimensions listed anywhere but given the size of the amps on top I assume it's 8" wide.
Really resisting the urge to buy this just to stick next to my turntable for maximum nostalgia vibes (I wasn't even alive then....)
Really resisting the urge to buy this just to stick next to my turntable for maximum nostalgia vibes (I wasn't even alive then....)
Cawafuoshi
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Isn’t that just the same as one the already available Douk meters? What kind of engineering goes into the Fosi one?
rana_kirti
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using this device, can we connect a pair of speakers to used as front left right in an AVR (5.1) and also separately to a Stereo Amplifier for 2 channel audio listening....? essentially connecting the same pair of speakers to an AVR and a Stereo Amplifier?
OP
- Thread Starter
- #11
If your AVR has pre outs for the front / left channels then this would work - connect the pre-outs to one of the inputs and the Stereo amp to the other input.
grogi.giant
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Yes. You will be able to switch between amplifiers.
early rejecter
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This device takes speaker-level input — no pre-outs necessary for switching between amps.
OP
- Thread Starter
- #14
Yes sorry you are completely right - I was thinking of a different device
Bought one from Audiophonics. Seems to work fine but there are some reasons you probably won't want it.
When turned off, it automatically goes to input amp B and output speakers 2. You can keep using it when turned off that way but only in this configuration.
It does however remember the last inputs/outputs when turning it on. (you don't need power to use input B output 2, for all other configurations you need to power it on)
The VU meters are not buffered! Even turned off, VU meters keep on moving. One would think this is fine, but this means it does interfere in the signal path. It probably does not have a big impact but it might induce some distortion.
On the positive side, the remote did not interfere with my Topping D70s DAC.
The sensitivity of the meters actually is 250-300 watt-ish. That means you won't see much movement in normal use, unless you play loud or need a lot of power.
The sensitivigy-knob should be at max to give a more or less correct reading. Any lower setting and you won't see any reading at all. So the sensitivity knob is rather pointless.
Binding posts are ok but the holes are vertically. Diagonal would have been more easy.
So if you need a speaker/amp switch that can handle high power, it seems usable, but I would not use it in a critical listening environment.
If you want dancing VU-meters without using more than 25 watts, forget it.
When turned off, it automatically goes to input amp B and output speakers 2. You can keep using it when turned off that way but only in this configuration.
It does however remember the last inputs/outputs when turning it on. (you don't need power to use input B output 2, for all other configurations you need to power it on)
The VU meters are not buffered! Even turned off, VU meters keep on moving. One would think this is fine, but this means it does interfere in the signal path. It probably does not have a big impact but it might induce some distortion.
On the positive side, the remote did not interfere with my Topping D70s DAC.
The sensitivity of the meters actually is 250-300 watt-ish. That means you won't see much movement in normal use, unless you play loud or need a lot of power.
The sensitivigy-knob should be at max to give a more or less correct reading. Any lower setting and you won't see any reading at all. So the sensitivity knob is rather pointless.
Binding posts are ok but the holes are vertically. Diagonal would have been more easy.
So if you need a speaker/amp switch that can handle high power, it seems usable, but I would not use it in a critical listening environment.
If you want dancing VU-meters without using more than 25 watts, forget it.
Elgrosso
Active Member
Got one few weeks ago, idea was to test it and see if I could easily build something close to what @dualazmak did
Turned out I probably won't but I did something else.
But first I didn't have any of the issues you listed, my device didn't let sound pass though and needles didn't swing when off.
Maybe I wasn't in a similar configuration, I used only one speaker out with two amps and maybe it was A, don't remember.
I should retest but I can't anymore I'll explain later.
Otherwise build quality is pretty good, nice finish and feels solid.
A bit too bright even in 25% for me though, 10% would be great.
About the sensitivity range, I agree with you it is too short, makes it useless if you don't use big power.
I tried it in variable channels on my active system and only the woofers would make it swing a bit, but still off by 10-20db.
I know the voltage out of each of my amps at different levels as I worked around the real power usage to reduce amp power/size.
Woofers need at max 100w but mostly cruise between 1-10w for example.
My goal was both for fun and to learn about the dynamic use of power upon variable parameters like targets, eq, tracks of course etc
And observe especially the woofers and subs as they're all dipoles with potential big excursion, just wanted to learn more than with jus test tone here.
Anyway long story not so short, it wasn't working for the purpose so I started to browse and search for infos.
Thought about modifying it but once opened I realized it's only two pcbs with a bunch of smds and I don't know enough here.
Didn't find much but there’s a thread on Audiokarma I follow that could give us answers in the future.
But Z in his review proposed an idea to circle around the issue: use a dedicated amp only for the VU, with then adjustable levels independently of the speakers.
I tried and even with no speaker plugged it worked.
Had one channel left on one dsp so I just wired a spare V3 to it, but a simple Y rca from existing amp should work too.
This way with dsp level/amp volume level/sensibility knob you can adjust the needle 0db to what you need with test tones.
I was able to gain the missing 20db or even more (be careful as it could max out fast and maybe break the meter?)
I could use full range or even replicate the dsp settings of each channel (5 way setup) to follow them specifically.
Fosi said there is a minimum load of 390 ohms for the amp, I didn't test this but the amp doesn't heat up and consume almost nothing (few watts in input).
A bit silly of course to use all this material for just VU, but it's fun and I learned things.
And it gave another idea… the box is big and empty, so why not putting the little amp inside?
So I did it yesterday in few hours, more as a proof of concept.
The v3 board doesn't fit as is (maybe a smaller tpa3255 would?), I had to disassemble the lc30 rear pcb and place it on the bottom panel, with tpa on top, reversed.
Few holes to attach the tpa board for heat dissipation, one for the volume know on the side, and enlarge the rear ones for rca/power/usb pass through.
Had few brain farts on how to wire it all inside but got it right, it works, everything is functionnal.
I'll play with it few days and if I like it I will reopen and clean up the wiring etc.
Maybe adding a pass through/amp bypass controlled by the switcher + usb/power plug extension to the rear panel for a clean look.
Next time I'll take pictures inside, now it's a mess with too long wires, it was not easy to cleanly close.
Turned out I probably won't but I did something else.
But first I didn't have any of the issues you listed, my device didn't let sound pass though and needles didn't swing when off.
Maybe I wasn't in a similar configuration, I used only one speaker out with two amps and maybe it was A, don't remember.
I should retest but I can't anymore I'll explain later.
Otherwise build quality is pretty good, nice finish and feels solid.
A bit too bright even in 25% for me though, 10% would be great.
About the sensitivity range, I agree with you it is too short, makes it useless if you don't use big power.
I tried it in variable channels on my active system and only the woofers would make it swing a bit, but still off by 10-20db.
I know the voltage out of each of my amps at different levels as I worked around the real power usage to reduce amp power/size.
Woofers need at max 100w but mostly cruise between 1-10w for example.
My goal was both for fun and to learn about the dynamic use of power upon variable parameters like targets, eq, tracks of course etc
And observe especially the woofers and subs as they're all dipoles with potential big excursion, just wanted to learn more than with jus test tone here.
Anyway long story not so short, it wasn't working for the purpose so I started to browse and search for infos.
Thought about modifying it but once opened I realized it's only two pcbs with a bunch of smds and I don't know enough here.
Didn't find much but there’s a thread on Audiokarma I follow that could give us answers in the future.
But Z in his review proposed an idea to circle around the issue: use a dedicated amp only for the VU, with then adjustable levels independently of the speakers.
I tried and even with no speaker plugged it worked.
Had one channel left on one dsp so I just wired a spare V3 to it, but a simple Y rca from existing amp should work too.
This way with dsp level/amp volume level/sensibility knob you can adjust the needle 0db to what you need with test tones.
I was able to gain the missing 20db or even more (be careful as it could max out fast and maybe break the meter?)
I could use full range or even replicate the dsp settings of each channel (5 way setup) to follow them specifically.
Fosi said there is a minimum load of 390 ohms for the amp, I didn't test this but the amp doesn't heat up and consume almost nothing (few watts in input).
A bit silly of course to use all this material for just VU, but it's fun and I learned things.
And it gave another idea… the box is big and empty, so why not putting the little amp inside?
So I did it yesterday in few hours, more as a proof of concept.
The v3 board doesn't fit as is (maybe a smaller tpa3255 would?), I had to disassemble the lc30 rear pcb and place it on the bottom panel, with tpa on top, reversed.
Few holes to attach the tpa board for heat dissipation, one for the volume know on the side, and enlarge the rear ones for rca/power/usb pass through.
Had few brain farts on how to wire it all inside but got it right, it works, everything is functionnal.
I'll play with it few days and if I like it I will reopen and clean up the wiring etc.
Maybe adding a pass through/amp bypass controlled by the switcher + usb/power plug extension to the rear panel for a clean look.
Next time I'll take pictures inside, now it's a mess with too long wires, it was not easy to cleanly close.
Elgrosso
Active Member
Had to open it to re-tighten the RCA connectors so here some inside pics.
- Unit is laying on its top panel here, you see the TPA is too large for the rear lc30 pcb to fit back, so I placed it at now the bottom on the unit when closed. I will glue it later.
I kept most of the connectors on the board to reuse it later, but removing all this and optimising wire length should make everything cleaner.
- the holes for the heatsink/connector to the top panel, and the volume knob.
The shaft is protruding only 5mm outside so the knob doesn't fit tight, will have to find another one, or glue it.
Adding a new knob with some sort of extension to the front would be cool.
- the rewiring of the unit, blue/black for speaker out of the TPA to "speaker 2", black wires on "amp A" to the RCA on the TPA
Same here replacing the power plug and usb plug on their boards with an extnsion to the rear panel would be cleaner.
So I now have a standalone and adjustable all purpose db meter, adjustable in the way I can set the 0db reference to any need.
It can still be used as a neat little amp of course, and that might be its final use after I'm done testing my system.
When I initially checked the accuracy was good enough, I mean going down 10db on the input on the DSP would move the needle down by 10db.
I need to do more tests to see if it's still the case at all levels, don't need 100% accuracy but a just good ballpark.
I repeat, the goal here is to learn more about the power use and its distribution in my system in real life, even if I already have a good idea with test tones.
I won't trust the power readings on the meter as power here is just a tool to modify what @fosi picked as a rule in the unit, but the proportion watts/db should still be good so the db meter could be trusted.
An increase of 10db would mean 10x more watts, whatever the db level.
As a baseline I have some voltage readings with test tones in each bandpass at -30/-20/-10dbfs and only calculated the 0dbfs.
So the idea is to adjust the meter to the same step levels, and see the real life behaviour with music.
If the woofer only goes to let's say -6db with real music, this would mean it reaches 1/4 of my max power measurement.
Well that's what guess and expect
Also about the power consumption:
In the V3 case with the first 32v PSU tested: max possible is about 60 watts on 4 ohms, so around 15v.
But without any speaker plugged the amp would see 390 ohms (in theory).
So if I get this right, with the same tension pushed, with the help of the DSP boost on inputs, it would be about 0.5w.
That would explain why it's never even warm, and the very low added consumption of 3 watts at the input (with a plugged watt meter on the shared outlet).
I still don't understand why it works, the power/db reading in this case should be low, but it's high.
Maybe @fosi only used the voltage to define their meter law?
- Unit is laying on its top panel here, you see the TPA is too large for the rear lc30 pcb to fit back, so I placed it at now the bottom on the unit when closed. I will glue it later.
I kept most of the connectors on the board to reuse it later, but removing all this and optimising wire length should make everything cleaner.
- the holes for the heatsink/connector to the top panel, and the volume knob.
The shaft is protruding only 5mm outside so the knob doesn't fit tight, will have to find another one, or glue it.
Adding a new knob with some sort of extension to the front would be cool.
- the rewiring of the unit, blue/black for speaker out of the TPA to "speaker 2", black wires on "amp A" to the RCA on the TPA
Same here replacing the power plug and usb plug on their boards with an extnsion to the rear panel would be cleaner.
So I now have a standalone and adjustable all purpose db meter, adjustable in the way I can set the 0db reference to any need.
It can still be used as a neat little amp of course, and that might be its final use after I'm done testing my system.
When I initially checked the accuracy was good enough, I mean going down 10db on the input on the DSP would move the needle down by 10db.
I need to do more tests to see if it's still the case at all levels, don't need 100% accuracy but a just good ballpark.
I repeat, the goal here is to learn more about the power use and its distribution in my system in real life, even if I already have a good idea with test tones.
I won't trust the power readings on the meter as power here is just a tool to modify what @fosi picked as a rule in the unit, but the proportion watts/db should still be good so the db meter could be trusted.
An increase of 10db would mean 10x more watts, whatever the db level.
As a baseline I have some voltage readings with test tones in each bandpass at -30/-20/-10dbfs and only calculated the 0dbfs.
So the idea is to adjust the meter to the same step levels, and see the real life behaviour with music.
If the woofer only goes to let's say -6db with real music, this would mean it reaches 1/4 of my max power measurement.
Well that's what guess and expect
Also about the power consumption:
In the V3 case with the first 32v PSU tested: max possible is about 60 watts on 4 ohms, so around 15v.
But without any speaker plugged the amp would see 390 ohms (in theory).
So if I get this right, with the same tension pushed, with the help of the DSP boost on inputs, it would be about 0.5w.
That would explain why it's never even warm, and the very low added consumption of 3 watts at the input (with a plugged watt meter on the shared outlet).
I still don't understand why it works, the power/db reading in this case should be low, but it's high.
Maybe @fosi only used the voltage to define their meter law?
Elgrosso
Active Member
My mistake, I thought I saw some linearity in the way the needles move, when there isn’t.
I mean by playing with signal level and knobs I could find a point where the needle would react well.
A point where adding 10db on input would move the needle by 10db.
But if I add 10db more then the needle moves +40db for example.
The sensitivity knob changes the ratio, and the position of the needle on the scale seems to also change the ratio.
Sensitivity seems to go from 2db in / 10db shown on max setting, and something like 40+db in / 10db shown on lowest setting.
I can’t figure out the rules here.
So kind of useless, or I just don’t understand it.
I mean by playing with signal level and knobs I could find a point where the needle would react well.
A point where adding 10db on input would move the needle by 10db.
But if I add 10db more then the needle moves +40db for example.
The sensitivity knob changes the ratio, and the position of the needle on the scale seems to also change the ratio.
Sensitivity seems to go from 2db in / 10db shown on max setting, and something like 40+db in / 10db shown on lowest setting.
I can’t figure out the rules here.
So kind of useless, or I just don’t understand it.
Only if there in phase. Are theses meters fast enough to show clipping?
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