Hi Andrej,
So finally, what is the ideal capacitance, per rail, for FO L ?
I had the impression of 10mF /rail. Is this correct or we need more ?
Thanks
Thanks Hose,
In the meantime I read to the the complete thread (yup. downloaded on e-reader, many evenings, interesting insights in social behavior, very low information denisity at times....)
What I picked up...
Higher supply voltages seem to make the modules run more stable
"When LC was demonstrating his prototypes we discovered that lower supply voltages made amp less stable than higher."
The modules seem to be moody/sensitive
- make sure the heat sink is grounded
- better instal speaker protection
Unregulated SMPS gives best sound
Lower PS impedance gives better sound (hence the hypex 3K preference+the 3K is rather a 1K continous PS)
Additional capacitance lowers the output imedance as seen by the module. Depending on the chosen PS, more or less capicitance can be added.
beyond a threshold, a softstart is needed.
FO L needs at least 0,33 K/W heatsink's thermal coefficient to set proper bias at +/-85 V SMPS. Fischer Elektronik SK159 or SK533
There are some confusing statements about the FO L to be fully differential (or maybe not). So I'm still not entirely clear on this one (i.e. can I feed it a balanced signal and/or a line signal?)
So a minimal implementation would be
SMPS+FO+heat sinks.
A minimum wise implementation would be
SMPS+FO+heat sinks+speaker protection.
From there capacitance, soft start can be added.
Having bought the last two L modules, and given that these modules are not meant to be repaired, I'm somewhat warry of investing in those 3k700 SMPS-es. I don't see where I could use them in case I blow a module and there's nothing to replace them... ..
Fingers crossed I guess. Time to work out a BOM
Simply not true.
At our premises we regularly connect/disconnect input cables to powered First One amplifier, meaning in vivo. Sound effects coming out of all kinds of loudspeakers are like this, with none, nada, zero devastating results. Think about correctness of your amp built's, regularity of associated equipment and possibly visiting some basic electronics training in the future.
OK. Thanks.
I only rewrote what other declared trying to explain accidents.
Mine are working flawlessly.
Cheers,
M.
I have also got an mail with the reasonable offer to the solution.
I'm glad I only have two channels
I haven't had an email.
I'm sorry to hear that... Maybe it's cause rest of us are having broken M modules and yours are L, and LC is currently working on new M modules.
Your L modules are waiting for repair at LC?
May-be the power supplies used (unregulated ?) by people with broken modules were sending a peak of too high voltage for the output Mosfets ?
It should be interesting to dig this point, listing all their configurations in a more precise way.
Well, the use of SMDs offer some advantages, like amp sizes and better HF performances (lengths of tracks) but, for sure, not the best for easy or cheap repairs ;-)
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In reality, the amplifier will not make large voltage variation at the SMPS output in music reproduction.
Also, during load / unload of the SMPS, the voltage at the output will remain the same, without increase.
Hope that helps
You have to use 2 soldering stations one at each end of the components. The 39 ohm resistors nearly burnt on one module ( 43 ohm) I bought New and will replace them.
As the schematic is not published, it would be interesting to know where are those resistances, to can imagine what caused their overheat.
Émitter of the input stage or second stage of diamond if any ?
Unscreened Duelund silver in silk I think and maybe momentary lost Gnd connection. I just mounted new R39 and R 40 resistors . The amp could be used without problems afterwards but I repaired it.
He have a total off 6 moduls in his system.
Been reading the posts of dying modules. Sadly one of my channels died too couple of months ago only been in use 100 hours or less. Very hard thumping noise with the dc module connected so glad there wasn’t a tweeter connected. No support or replacement available so I have a broken half year old 800 euro amp. Think I use the hypex power supplies and hifi2000 case for another project. Wasted time and money on this one in my case.
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If it's FO M module it will be easy fix, just module replacement with new one.
It is not a question of "speed". It is a question of stability margin.maybe you should slow-down your modules, sometimes ultra-fast is not best option
And, if the measurements of Lazy cat in the first posts of this thread are right, FO is rock stable. Even loaded with 1µF // with 6 Ohms.
So what ? It seems, indeed, there is a problem, as many amps seems to had burned away in several and various builds. Why ?
If i was L.C., i would try to figure-it out seriously.
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