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FS: First One M v1.4 power amplifier module

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First One L module

I am in for 2 modules as soon as possible.
According to the current plan First One L modules will be available in last week of August. :up:


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The result is amazing good soundwise

Hi Everyone,
in the past days I had the chance to test my dual FO 1.4M with 2 smps from audiopower.it version DPS-400/S1 and I thought I could share some info and picture.
I knew this supply from a previous project 2 years ago, and till then they have revised this smps with a new transformer and the overall power is said to be supporting 600watt and more than 600ma continuous current (bias) wihout any overload problem.
I wanted to keep the overall temperature of the amp below 50°C and then I have chosen a 2x52V version, which is 10V less than hypex, so the overall dissipation (without signal) is 29watt per heatsink instead of 35watts, reducing the heatsink temperature of about 3 degrees.

The result is amazing good soundwise. with the 2 smps, obviously the result is better than with 1 big hypex!. I can hear more séparation across the 2 speakers. for the bass, it is a mater of volume listening.

the SMPS is quite compact (105x105) and can be fixed on a standard 2U 300x80 heatsink, with the FO.

the only drawback I see is that the supply do not have the posibility to directly connect a DC current protection (as sold by LC) as its standby mode is not "latched" so if your concerned by DC protection you have to add a traditional relay based protection.

here we are with another alternative to make compact dual mono system, for example using the "mini dissipante" case.

Link to the original post here. ;)


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Stereo Amp finished

Hi Guys,

I have just finished my new First One 1.4M build with SMPS600 from Cresnet and some capacitor boards that I got very cheap from Taobao, 4400uF per rail extra United Chemicon KYB from Mouser, less than US$2 each when you buy 10, and very low ESR and high ripple when paralleled.

One thing for anyone who might want to add extra capacitance to an existing Cresnet supply. The extra capacitance tripped the Over Current protection at start up, with advice from Cresnet all it took was 1 resistor to be added in parallel and the problem was solved.

Next in line is the rebuild of my 1.2 modules into a 6 channel amp with individual power supplies.

I have found another SMPS from Taobao that is very well made for a very low price, I have tested them and so far work very well and sound excellent. They drop around 5V under load and on 240V AC give 55V when loaded with a First One at idle. These are strictly 220 to 240V only though.

As I needed to buy 6 the shipping was making other options very expensive.

Link to the original post here. ;)


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Never hear the speaker sing so well

I was using Teddy Prado 100w mono before this amp driving a pair of Genesis IM8300. Never hear the speaker sing so well before for the past 10 yrs.

Nothing really problem except the amp need few seconds to discharge after power down with some funny sound from the speaker and also after adding cap I encounter 2-3 times one channel not powering up when turning on the amp. I suspect the startup current too high and cause one of the psu shutting down. Randomly happen on either side. But a power down and up always works. Maybe my fault of shutting down too fast when changing cables or preamp. Not sure. Just know it's sounds great.

My friend came my office heard my amp ask me to diy one for him also. Another friend studying to make one too. I have reserved 2 FO M module previously please add 2 more FO M to my order. Also waiting for your dual mono chassis and FO L module also. Great job.


Link to the original post here. ;)


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when it comes to sound, this is just fantastic and clean

I ve been recalibrating my quad FO box this week so I can suggest the folowing
you can use a 0.22ohm resistor. I ve got a rectangular 10W but you can use a 3W (P=R.I^2 you are safe) and then you will read 62milivolt (U=R.I)

LC is right, adjusting the driver stage for reading 180mv has to be done when the temp is settled, and from my experience this is an iterative process over say 1 hour (after 1 hour of heating) . also you should do the adjustement in the same condition of the final implementation of your amp in a case with the cover part as this will change the inside temp.
Finally I d say do not uderestimate this topic, if you have less than 150mv (ish) the driver stage will leave class A and will produce lots of harmonics but once you are at 180mv the driver stage is cleaner than your bathroom and you're the king. If you have to make tradeoff with the offset adjustment then this is more important than few milivolt of offset on the output.
Link to the original post here. ;)


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we can choose the best

Oh I am honoured, but I would rather find a bigger chassis than to settle for less SQ with a lower bias current...

Thats the wonder of this DIY hobby.... we can choose the best all out design rather than settle for a compromise in commercial product due to costing.

and again... LC you are really guru in this. I was listening to my new active ATC SCM-50A for the past few days and when i turn on this FO-L with my IM-8300f I was shocked by the transparency and reality... makes me little regret buying the active version now. If this FO-L goes well, who knows maybe down the road I will get rid of the SCM-50 amp, get an electronics dac/crossover and powered the driver actively using FO-M and L :eek:)



Link to the original post here. ;)


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