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First One - mosFET amplifier module

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#1,089
Great idea... let's do it right

Lazy Cat said:
No need to, chassis is still 100% earthed, fool proof. 😀
Click to expand...

With great respect, LC . . .

I'm a bit of a safety nut and would argue that nothing is 'fool proof', but we can require a bigger fool to prove us wrong 😀

Your earth-isolation networks back in #838 (?) are very similar to what I've adopted for years now - can really work magic at keeping ground-loop currents at bay. However, I would like to point out a couple of changes for your consideration:

1st - the diodes, these should be rated for a PIV well above the peak mains voltage with a current rating that at least betters the primary mains fuse (at the inlet) - and some might argue for better than the mains breaker rating. WHY? Simple, should there be some catastrophic failure in the PS and either mains or some other HV rail were to short to the PS-gnd with impunity, I for one would want to know there's a sturdy and capable path to the Earth line (okay, so maybe at 0.7V up) which would [functionally] guarantee a proper fail-safe shutdown scenario. In the grand scheme of things, chump change to implement and does not degrade the network's intended function.

2nd - in parallel with or in lieu of the 1k resistor, add a 1-22nF, 600v film cap to give stray RF currents in the PS-gnd conductors a low[er] impedance path to the Earth line.

3rd - I'd love to hear the debate as to why the 1k resistor is included, seems useless to me - assuming one isn't bothered by the potential for the PS-gnd to float 0.7V above the Earth line - hardly a danger or threat.

Cheers!
 
#1,090
lgo51 said:
1st - the diodes, these should be rated for a PIV well above the peak mains voltage with a current rating that at least betters the primary mains fuse (at the inlet) - and some might argue for better than the mains breaker rating. WHY? Simple, should there be some catastrophic failure in the PS and either mains or some other HV rail were to short to the PS-gnd with impunity, I for one would want to know there's a sturdy and capable path to the Earth line (okay, so maybe at 0.7V up) which would [functionally] guarantee a proper fail-safe shutdown scenario. In the grand scheme of things, chump change to implement and does not degrade the network's intended function.
Click to expand...

So something like MUR1560G?

Do
 
#1,093
Lazy Cat said:
Full balanced and bridge versions need good ballanced source, correct grounding and good interconnect cables. If any of these fails, sound's gone. One simple unbalanced interconnect cable makes a great difference, imagine all the rest.
Click to expand...
Would you provide the optimal modules/wiring layout for full balanced connection, including ground lifting ? (pair of FO with one smps1200a180 per channel)... should the modules be adjacent mounted on heatsink to minimize distance between input terminals? or minimize distance between speaker output terminals?
 
#1,094
SpyNet said:
The dc sense is only for first one?
Click to expand...

No, it's universal DC sense circuit with low pass filter -46 dB/10 Hz actuating opto darlington. The normally opened output serves to shutdown any power supply having input for this function. 😎

For example SMPS1200A400 connector J4 pin 9, pin 10 are the ones to be connected to DC sense. 😉

Below is how finished DC sense PCB looks like. 🙂
 

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#1,095
Dmitry Nevozhay said:
Would you provide the optimal modules/wiring layout for full balanced connection, including ground lifting ? (pair of FO with one smps1200a180 per channel)... should the modules be adjacent mounted on heatsink to minimize distance between input terminals? or minimize distance between speaker output terminals?
Click to expand...

Full balanced block sch is included in user's manual delivered by the modules.

GND lift is easy, the same DRD circuit used as with stereo block sch.

Modules are always mounted in a way that the power transistors are at the bottom edge of the heatsink, so the heat is coming from below to the top. In this way heatsink is maximally efficiently used for best thermal dissipation. Always use heatsink having 0,5°/K/W or better.
 
#1,096
Recommendation for Bridged mode PS ?

Lazy Cat said:
Hi Dominic
Now to the questions:
- in bridge mode min 4 Ohm impedance is recommended, meaning 4 Ohm in average if looking impedance curve, so it can also be less than 3 Ohm somewhere in the bass region, but that's OK if the average is still around 4 Ohm. The limit here is the output current which is 16 Amax and if looking to SOAR chart of the outputs, you can see these are very robust semis, at 100 Vdc they still easily sink/source 2,5 A 😱
- since the modules are calibrated at +/- 63 V, at +/-42 V idle current would be a little bit lower, but still recalibration back to 280 mA (complete module's idle current) can easily be readjusted by trimmer TR3
- definitely LL1540 Lundahl line input transformer

In bridge mode at +/- 42 V PSU voltage you would easily get 500 W/4 Ohm and still be well in a SOAR. 😎
Click to expand...

Hi LC,

Okay, so I get the impedance limitations in bridged mode (effective 2 ohm avg. per module, 250W, ~31.6Vpk ==> 15.8Apk)... great! What I don't know is what the sag is for either the SMPS1200A400 or the __A180 PS modules when delivering that sort of current. Reason is simple, I'd like to use the most appropriate PS module; and from the copious posts here I gather there's yet no contender to the SMPS1200's throne position. Thoughts?

Cheers!
 
#1,097
Lazy Cat said:
Full balanced block sch is included in user's manual delivered by the modules.

GND lift is easy, the same DRD circuit used as with stereo block sch.

Modules are always mounted in a way that the power transistors are at the bottom edge of the heatsink, so the heat is coming from below to the top. In this way heatsink is maximally efficiently used for best thermal dissipation. Always use heatsink having 0,5°/K/W or better.
Click to expand...
as well as I asked for the physical layout of two modules on the shared heatsink... should they be mounted as close as possible to each other, and which edges/sides? if +/- of balanced input terminals are too distant, the inducted parasitic errors may differ and will not cancel no more ... I always thought that optimal position for power transistors is at center of heatsink, not on edge, as heat transfers more even to all metal blades
 
#1,098
lgo51 said:
Hi LC,

Okay, so I get the impedance limitations in bridged mode (effective 2 ohm avg. per module, 250W, ~31.6Vpk ==> 15.8Apk)... great! What I don't know is what the sag is for either the SMPS1200A400 or the __A180 PS modules when delivering that sort of current. Reason is simple, I'd like to use the most appropriate PS module; and from the copious posts here I gather there's yet no contender to the SMPS1200's throne position. Thoughts?

Cheers!
Click to expand...

1200A180 is the one to go with balanced version of the First One, since it can deliver 13 Arms (18,45 Ap) at 46 V. In reality it would drop for a few volts but that's still aceptable. Two First One modules per channel in balanced version with 1200A180 would easily give 500 Wrms/4 Ohm load. :yes:
 
#1,099
Dmitry Nevozhay said:
as well as I asked for the physical layout of two modules on the shared heatsink... should they be mounted as close as possible to each other, and which edges/sides? if +/- of balanced input terminals are too distant, the inducted parasitic errors may differ and will not cancel no more ... I always thought that optimal position for power transistors is at center of heatsink, not on edge, as heat transfers more even to all metal blades
Click to expand...

First One modules have to be mounted as I already explained, power transistors side at the lower edge of the heatsink, laterally each one at third from the heatsink's lateral edges. And this is of utmost priority, cabling is in a second plan.

Input cabling for each module should be of the same lenght, routed at the upper side of the modules, where the input is located on PCB, to the input XLR connector.
 
#1,100
It occurs to me that for products such as this, it might be preferred to have two threads. One for build details/advice only. The other for listening impressions and comparisons to other components serving same purpose.

It gets very old sifting through posts for comparisons to similar type products.
 
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