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First One - mosFET amplifier module

First One L module price is 220 EUR. First One Cap Bank Positive or Negative module consisting of two four pin Mundorf MLytic 3,3 mF/100 V and two WIMA 0,22 uF/100 V, price is 68 EUR/pcs, including one DUELUND silver bypass 0,01 uF/600 V, price is 148 EUR/pcs. ;)
Hi LC,
for the L module price given above, does it include also 2 cap banks or they have to come on top ?
 
Hi Maxidcx,

I will let LC correct me if I am wrong, but my understanding of his narrative is:
- each L module "alone" = 220E
- each additional cap module, normal version = 68E
- each additional cap module, supaadoopa version = 148E

To build a L stereoamp you will need at least 2 L modules (440E), plus eventualy 2 cap modules if you go that route (either version).

I hope this helps

Claude
 
Hi Maxidcx,

I will let LC correct me if I am wrong, but my understanding of his narrative is:
- each L module "alone" = 220E
- each additional cap module, normal version = 68E
- each additional cap module, supaadoopa version = 148E

To build a L stereoamp you will need at least 2 L modules (440E), plus eventualy 2 cap modules if you go that route (either version).

I hope this helps

Claude

I have put 10000 uF in my FO medium amp. It calms the sound, gives more authority in the bass, with increased resolution. Simply, it has more boogie factor.
 
20170110_002233.jpg


First One L. Heatsink 160 mm High 300 MM Long and 75 deep. Should be ready for Higher bias?
 
Here is my iteration of FO 1.4M amps.

I used Hypex SMPS as recommended by Andrej, laser-cutted aluminium cases of my design (mostly 3mm aluminium + 8mm on front), huge and beautiful heatsinks from CoolTec Gmbh.

Among added features, trigger 12v in & out, temperature sensors on each heatsink, low voltage power push button (invisible, bottom), RGB led on front (used for status, colors + blinking for sleep/startup/temp warning/etc), controlled by an Arduino.

On the back, i used fully isolated binding posts (Cliff CL159825, rated for 60A), Amphenol RCA sockets, 2 minijack sockets (for triggers), and USB connector.

A small power supply with very low consumption powers the Arduino board, which controls 2x Solid State Relays, which controls power to SMPSs.
I used a medical-grade IEC filter with power switch and fuses to connect main line.

Control board & power supplies are enclosed in the middle of the case.


About the sound: well, i had more than 30 amplifiers during last 25 years, this one beats them all. It sounds very natural (clapping hands are just perfect for example), very fast (percussions are great), everything seems under control, clearly high end sound, i'm very happy with the result.

Drawback: input impedance is on the low side, my passive volume control doesn't work well (at all) with those amps (resistors/relays), that was expected, but it is even worse i thought ;) I had no issue with amps with 70kohms input impedance.
Distorsion suddenly appears at some point, i had to remove this element for now, still investigating for a solution.
With an input impedance >50k, FO amps would be perfect.

Conclusion: buy those, follow Andrej recommendations about power supplies, no surprise it will just work and sound great.

PS: i ordered capacitors to add caps banks, feedback soon.
 

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Hi Zas,

Great effort, congrats aswell, and thanks for sharing all this.

Regarding the low input impedance and the use of passive pre, that is something that bothers me aswell. I asked LC about it and my understanding was (back then):
- indeed FO has a low input impedace with low values resistors to reduce the noise
- it seems easy to alter this somewhat without being to detrimental to sound by just changing 1 resistor.
=> Perhaps worth asking LC?

What passive pre are you using? I figured out that a basic 10k log pot should do the trick though (as its worst case output impedance is likely to be in the 2.5k region, whereas FO 1.4M has about 10 times that input impedance). Please let us know what values you are using, interesting...

On an other note, you said you had more than 30 amplifiers, could you name a few of the best ones? What loudspeakers are you using? I have recommended FO to a friend of mine, but sadly somewhere direct comparisons with this little gem are scarse... making absolute evaluation not easy.

Many thanks

Claude
 
Hi Zas,

Great effort, congrats aswell, and thanks for sharing all this.

Regarding the low input impedance and the use of passive pre, that is something that bothers me aswell. I asked LC about it and my understanding was (back then):
- indeed FO has a low input impedace with low values resistors to reduce the noise
- it seems easy to alter this somewhat without being to detrimental to sound by just changing 1 resistor.
=> Perhaps worth asking LC?

What passive pre are you using? I figured out that a basic 10k log pot should do the trick though (as its worst case output impedance is likely to be in the 2.5k region, whereas FO 1.4M has about 10 times that input impedance). Please let us know what values you are using, interesting...

I was using a multichannel relay-based shunt attenuator from Khozmo Acoustic, with 10k impedance (see High Quality Audio & Industrial Attenuators)
Clearly not a good match for FO, but still an excellent device.


On an other note, you said you had more than 30 amplifiers, could you name a few of the best ones? What loudspeakers are you using? I have recommended FO to a friend of mine, but sadly somewhere direct comparisons with this little gem are scarse... making absolute evaluation not easy.

Many thanks

Claude

I used commercial amps from Electrocompaniet, Marantz, AudioAnalogue, Rotel, Bryston, etc, plus various chip amps (class AB, D, E, T), plus various DIY projects. Either in stereo or multichannels.

I'm now using DIY loudspeakers derived from Hestia V project, open baffles / full dipoles, requiring 4 channels (bass in H-frames up to 120hz with 4x30cm, actively crossed to a mid-bass/med/high "head" with 25cm + 10 cm + tweeter, passive crossing between those). All speakers have been chosen mostly for their low distortion and my use of them.

I would say the whole system has a very hard to beat quality/price ratio, and FO amps are just fitting very well in it (being very high quality and realisticly priced).

FO amplifier isn't as warm (sound-wise, not temperature-wise) as some amps, but i'm looking for natural & neutral sound (read high fidelity sound), bass is tight and here when needed, highs are clear, metalic sounds are ... metalic, horns sound like horns, air is vibrating, rythm is there, what more to ask ? FO amp is just a great amp, that let me concentrate on other parts, that is the source (bad source=bad sound, good source=possibly good sound), and the loudspeakers+room (which are by far the weakest point in any system).
I'm listening any kind of music, from classical, to the heaviest metal, FO amp just does it, whatever i play, it just sounds good.

Anyone looking for a good amplifier should consider First One, together with a very good power supply. Setting up FO according to LazyCat documentation, isn't hard at all (though it requires patience, mine were just off, now all have 280mA, 180mV, <+/-5 mV DC as recommended). I started the project in last october, designed cases, and control board, ordered heatsinks, etc... it would be much simpler to order assembled amps from LazyCat (and not expensive, if you consider the quality), especially if one isn't used to DIY electronics. I don't regret my choice, the result is fitting my expectations, dead silent amps (when no sound) with impressive dynamics and neutral sound.

@LazyCat: thank you.
 
Here's my new build coming along!

2017-01-04%2000.49.05_zpsmkdb6oug.jpg


2017-01-04%2000.48.58_zpsn4iazkdd.jpg


I will post more pictures when completed. So far it sounds quite good!
The SMPS are mounted on the front panel as you can see and the chassis kinda looks empty but it will eventually be filled with the FO L modules so it will leave room for the cap banks.

LC, just a quick question for you.. I biased the output stage idle current to 380mA instead of the 280mA but I wanted to know if I should keep the VAS current to 18mA or crank it up a little?

Thanks
Do
 
Wonderful job Do!

Best,
Anand.

Thx!

I'm waiting on my full speaker protection to arrive before I try it on my speakers. I don't want to use just an SMPS shutdown protection since I don't want to take any chances of damaging my speakers. If one rail fails there's a chance of 60Volts in the drivers, although not long I don't want to take a chance.

Ciao!
Do
 
We are looking at great builds here!

Dear Zas,

Congratulations for a beautiful case.

IF you prefer passive volume control, please consider Transformer based Volume Control (TVC) as it works great with the FO. It has various advantages like BAL/unBAL in/outs possible configurations, galvanic isolation, possibility of wiring as autoformer for claimed optimal linearity (which I have not used, as it defeats the former), very dynamic sound with high Vout sources as the EMF is conserved.

Amicalement,
M.
 
Thx!

I'm waiting on my full speaker protection to arrive before I try it on my speakers. I don't want to use just an SMPS shutdown protection since I don't want to take any chances of damaging my speakers. If one rail fails there's a chance of 60Volts in the drivers, although not long I don't want to take a chance.

Ciao!
Do

Wise plan.

With the "all floating" configuration I had bad experiences with another amp when the cheap interconnect used for testing loose the "return" or "ground" lead--> some power transistors (PNP; negative side) blew with an horrible noise. Fortunately the speaker protection system did its job.
Perhaps some expert would like to explain how this can occur as I recall one mate complaining about the same accident here.

Cheers,
M.
 
Hi Danny_66,
Could you please share what softstart module you used?

Hi Claude,
It's an ebay soft start module :)

Nice builds of Zas and Do!
Do, you have still plenty of room to add some caps, with the softstart it's not a problem for the Cresnet SMPS.

The FO 1.4M is indeed a very good amplifier, I have just replaced the 4 onboard power supplies of my Soekris DAC with muzgdiy regulators.
With the FO 1.4M I can clearly hear the added 3D, echoes of instruments, a holographic sound. A lesser amp would mask these.
 
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Hi Zas,

Your attenuator from Khozmo Acoustic is indeed a reputated good one.

I have checked y notes again and "non modified" the FO as indeed a very lowish 10k input impedance. With 10k impedance, yur attenuator (having less than 2.5k) should though still cope with limited connextions, but apparently it doesn't which is indeed a sad news.

Transformator based attenuators of course work like a gearbox re impedance and are inherently suited, whereas resistor based attenuators just dissipate energy. All have some pros and cons but given you have already a nice attenuator for sure there must be a way to increase the FO's input impedance as LC once suggested... while keeping your pot. Have you contacted LC?

It would be pity if the FO's low input impednce would rduce the field of affordable passive preamp...

On an other noten thanks for your feedback re set up and past components.

Good luck

Claude
 
Thx!

I'm waiting on my full speaker protection to arrive before I try it on my speakers. I don't want to use just an SMPS shutdown protection since I don't want to take any chances of damaging my speakers. If one rail fails there's a chance of 60Volts in the drivers, although not long I don't want to take a chance.

Ciao!
Do

Hi Pinnocchio,
By the sound of it, it appears you aren't using LC's DC protection device but an other, more complete solution perhaps? If so, which one?

On an other note, on all the nice builds I don't see any DC protection cap at the FO's input. As of me, I try to have as few DC caps as possible in my system, so I have none of them in my components bare only at my amp's entry, as you never know who might want to plug into (I have a passive pre).

How did you guys deal with that DC input problem, as I understand that the FO doesn't reject DC at the input...

Many thanks, interesting thread!

Claude
PS: to Pinnocchio, clever vertical SMPS implementation of yours, congrats
 
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