I'm not sure what you are referring to?
The ammeter was in series with the +ve Voltage Supply. With the Amplifier Module ‘idling’, Input Shorted and No Load (none is shown in the instructions) exactly as the instructions.
The Ammeter read 47mA.
Adjusting Trimmer TR3 had the effect of increasing the Current flow to a maximum of around the 50mA mark or reducing it. I only went down as far as 30mA. I saw no point in reducing it further.
Please make sure that you understand how to measure, and how to setup the DMM(s)! If you are not familiar with that you can make serious damage or worse...
I don't have a FO Large but the procedure is described exactly as it is with the Medium Modules and I have adjusted those quite a few times now successfully.
It really does take 3 multimeters to do it without a lot of frustration. I soldered wires to the test points to make it easier to attach the multimeters without having to try and hold the probes to the test points.
The values are very interactive and if someone has twiddled the trimmers it might take a while to get it back into balance. The trimmers are multiturn if they have been set to the end of their travel and you are having trouble I would set them all back to the centre and try again.
The amp really does need to be warm left idling for at least 20 minutes after switch on.
Having the ammeter or multimeter set to amps in line with the positive power supply is the correct way to measure the idle current draw.
This is the setup image for anyone unfamiliar
It really does take 3 multimeters to do it without a lot of frustration. I soldered wires to the test points to make it easier to attach the multimeters without having to try and hold the probes to the test points.
The values are very interactive and if someone has twiddled the trimmers it might take a while to get it back into balance. The trimmers are multiturn if they have been set to the end of their travel and you are having trouble I would set them all back to the centre and try again.
The amp really does need to be warm left idling for at least 20 minutes after switch on.
Having the ammeter or multimeter set to amps in line with the positive power supply is the correct way to measure the idle current draw.
This is the setup image for anyone unfamiliar
Attachments
Done - many thanks everyone for your help and assistance. Perhaps for my first ever electronics project I should have picked something easier, but I’ve learnt a great deal! Now for the listening comparisons against my ncore mono blocks!
Attachments
Speaker protection board can be found here. BTW, great products offered by XRKAudio.
I think there was a comment earlier on in this thread about FirstOne amplifiers sounding ‘better’ than ncore. One reason why I took on the project.
My (now sold) ncore monoblocks where made by Nord, had the first generation of buffers in them and Sonic Imagery 994 opamps - they sounded real good, but apparently you can do better with the newer buffers and say Weiss opamps.
I only did limited comparison as I sold a fair bit of kit to fund further equipment to go with the First One amplifiers, however what I can say is that they have more of a class A sound to them (as you would expect since these are class AB), you can definitely hear the Mundorf caps as well. First One sounds analogue...smooth, detailed, palpable and just very enjoyable. They make ncore sound like class D, even though they’re very good (perhaps the new purifi modules will be better). Previously I had found ncore to sound better than Naim 250, quad, musical fidelity, Cyrus so I hold them in high regard.
If you don’t mind the higher heat output of class AB and the heat sinks that go with it then perhaps have ago a building Fabs new FSSA amplifier - might be the closest (or improvement on) First One since the modules are no longer produced. Fab is doing a GB for PCB’s at the moment. It is also an evolution of the VSSA concept - I think this is what I like. FirstOne has the best tonal quality I’ve heard.
Hope that helps. If the situation eases in the future I’m going to take the amplifier for others to hear in their homes, so might have more feedback then.
My (now sold) ncore monoblocks where made by Nord, had the first generation of buffers in them and Sonic Imagery 994 opamps - they sounded real good, but apparently you can do better with the newer buffers and say Weiss opamps.
I only did limited comparison as I sold a fair bit of kit to fund further equipment to go with the First One amplifiers, however what I can say is that they have more of a class A sound to them (as you would expect since these are class AB), you can definitely hear the Mundorf caps as well. First One sounds analogue...smooth, detailed, palpable and just very enjoyable. They make ncore sound like class D, even though they’re very good (perhaps the new purifi modules will be better). Previously I had found ncore to sound better than Naim 250, quad, musical fidelity, Cyrus so I hold them in high regard.
If you don’t mind the higher heat output of class AB and the heat sinks that go with it then perhaps have ago a building Fabs new FSSA amplifier - might be the closest (or improvement on) First One since the modules are no longer produced. Fab is doing a GB for PCB’s at the moment. It is also an evolution of the VSSA concept - I think this is what I like. FirstOne has the best tonal quality I’ve heard.
Hope that helps. If the situation eases in the future I’m going to take the amplifier for others to hear in their homes, so might have more feedback then.
In fact lazy cat said it himself on the second page of this thread
Class AB, double die mosfet pair 250 W-16 A continous, each.
THD10k 100 Wrms/4 Ohm only 0.004 %, IMD19+20k 80 Vpp/4 Ohm only 0.003 %, 200 kHz square waves on 4 Ohm, is that looks like PWM to you?
Maximal power is normally presented just before clipping with 0,1 % level. Every amp comes to clipp eventually, it is its natural limit.
Had NC400, NC1200 and they don't come no where near close soundwise, the First One is a very different kind of beast.
Hello, thank you for your reply. Yes, I have seen lazycat comments about his own amplifier, long time ago. But I wanted an opinion from another person. I have seen fabaudio fssa amplifier project. I will ask them about technical specs. Something that really impressed me about FO, among other specs, was the damping factor which I did not see it in fssa specs.
TP1 & TP2 and TP3 & TP4 23mV ‘’out of the box’’ so to speak - in the end I left them like that as the heatsink temperature using a dummy load was 55oC... and I guess this is the final determinant of what is safe.
Perhaps using a regulated connex power supply might be a better solution (something I am thinking about for my other builds).
DF of FFSA is in the 150 to 250 bracket, constant over the audio band as CFA topology.
IMHO and to my ears, over 100 it doesn't matter if DF is 100 or 1000...
A long time ago I really wanted to try FO 1.4, but I am glad I didn't given it would have never materialized for me, the very poor support, the reported failures and the complete lack of schematic+many SMD devices which all makes it very difficult to repair or reproduce. In short, I am put off because I may have a VG amp (so most they say) but something that might burst (destroying my precious LS) and that I won't be able to repair or replace with a like easily, not mentioning to tune.
And the came Fab's amps, on a F speaking Canadian forum, later here aswell. FABulous work and sound they all said it seems to be confirmed internationaly now. FABulous guy aswell, very very nice and wiling to help, and a real community behind so you are not alone.
I went for Fab's FFSA (I am part of the GB). Fab has been constantly fabulous over the years, the schematics and an excellent build manual are provided once you commit to the GB, all parts are known quantities and it is quite simple / non complex bard.
Just me, my humble opinion and my choices
Claude
IMHO and to my ears, over 100 it doesn't matter if DF is 100 or 1000...
A long time ago I really wanted to try FO 1.4, but I am glad I didn't given it would have never materialized for me, the very poor support, the reported failures and the complete lack of schematic+many SMD devices which all makes it very difficult to repair or reproduce. In short, I am put off because I may have a VG amp (so most they say) but something that might burst (destroying my precious LS) and that I won't be able to repair or replace with a like easily, not mentioning to tune.
And the came Fab's amps, on a F speaking Canadian forum, later here aswell. FABulous work and sound they all said it seems to be confirmed internationaly now. FABulous guy aswell, very very nice and wiling to help, and a real community behind so you are not alone.
I went for Fab's FFSA (I am part of the GB). Fab has been constantly fabulous over the years, the schematics and an excellent build manual are provided once you commit to the GB, all parts are known quantities and it is quite simple / non complex bard.
Just me, my humble opinion and my choices
Claude
I completely second that - I'm on the FSSA GB too, having built the FirstOne amplifers using prebuilt modules I feel as though I now have enough experience to stuff my own PCBs now. Fab has given me confidence with his superb manual.