ZEN noob question

[MEGA_amp]

I purchased the Zen board a while ago, and finally got around to populating the board. Everything is original with the exception of a 4.7uF film cap across C6, a 10uF cap across C3, and a .22R 10 watt for R1. I eliminated C1 and C2, because my supply consists of 392KuF with 2.2 mH coils, unloaded it provides 53 volts (I'm using very large heatsinks, hopefully it wont blow up). Now, I remember Nelson suggests setting P1 to half the rail voltage, what two points do I measure from?


Thanks
John

 

[Nelson Pass]

From Ground to V+, or between the Source Pins of the two
Mosfets (close enough).

 

[MEGA_amp]

Thanks Nelson!! Still waiting on the FETs, pics soon to follow.

 

[johndiy]

umm i am new here what was there i wanted to ask
umm Nelson Pass is this the guy who is got articles
published in magazines like audioxpress or is a fake
you guys made up!umm cause it would be awesome
you know chat with him about fusistors and stuff

john

 

[Sonusthree]

Yes John he is the real Mr Pass.

 

[Babowana]

umm i am new here what was there i wanted to ask
umm Nelson Pass is this the guy who is got articles
published in magazines like audioxpress or is a fake
you guys made up!umm cause it would be awesome
you know chat with him about fusistors and stuff

a-man . . . enjoy the meal . . .

 

[johndiy]

you know Zen is awesome!
umm what happens if i change the active load with
a passive one, will it sound better, what type of fet
is better for zen L-fet or V-fet?

john

 

[johndiy]

need help with zen attached
umm is feedback equal to r3/r1 or r3/r2
if it is r3/r1 r1 should be low value right? how low?

is this a good zen?

john

 

[Babowana]

need help with zen attached
umm is feedback equal to r3/r1 or r3/r2
if it is r3/r1 r1 should be low value right? how low?

It seems that all r1/2/3 are involved in the feedback . . .
Gain approximately (r2xr3)/(r1x(r1+r2)) . . . ??? hmm . . .

 

[MEGA_amp]

fired up the zen, sounded great for a few minutes...The solder from the Drain of Q2 keeps melting off, and R1 gave up the ghost. Could this happen if Q3 is in backwards. Q2 blew on the left channel as well, but R1 is intact. It worked fine yesterday, the only change I made was to the power supply; I paralleled the two 2.2mH inductors, in the series config, they nearly melted.

R1 .22 10W
Q1 IRFP140
Q2 IRFP9140
45V rails




John

 

[Babowana]

John

I wish you a solution.

 

[MEGA_amp]

After blowing up a few mosfets with my 53V rails, it worked one day fine, the next it blew up Did some digging and reading up about parallel/bridged schemes, i'd like to try it out...or at least parallel first, as I dont have my XBOSOZ anywhere near completion, so balanced is out for now. The parallel is fairly straight-forward, in the future i'd like to bridge it and drive it balanced, but i'm not quite sure how to connect it. I'm not very good with some of the nomenclature, and I couldnt find an actual schematic of what some of these threads were describing...so here you go.

 

[MEGA_amp]

??
Do I replace C3,C4 with resistors? What other changes to the original Zen need to be made to drive it balanced?

 

[Babowana]

Hi MEGA-amp,


I hope my example will help.
Mine has current bias of 1.32A.
If you want 2A bias, reduce R0, R14 and R15 down to 0.33ohms.
If you want 3A bias, down to 0.22ohms. As you know . . .


Enjoy!

 

[MEGA_amp]

Perfect JH!!

Thank You.

John H.

 

[Nelson Pass]

We can assume that the channel is drawing lots of current,
and since that depends solely on the current source Q2, you
can quickly narrow it down to Q2 blown or the drive for Q2
(the pnp transistor) is feeding it too much voltage.