Pics of Zen4

[Buhl]

Hi There !
Thinking that this forum lacked some hardware pictures, I scuffed up a digital camera, and snapped some shots of my unfinished Zen 4. I have a freind assigned to the task of finding me some bigger heatsinks, so I can run balanced with high BIAS - this is single board with 2 amp BIAS - final edition will be 2 boards / monoblock and hopefully 2,8 amp BIAS This is merely a testing of the boards/sound of the circuit, witch should excuse me for the messy wireing

The big Q's are IRF 240, Tranny is danish made and 750 VA - the caps are 47000 uF/63 Volts.

Thanx to everyone who helped me in here - my amp would be silent was it not for you !

Special thnx to "The old guy" for sharing his wonderfull designs with us - you're the man !

/Cheers !

Hans

[Buhl]

Another pic.....

[audioPT]

Looks great, but I think the wires used are not the best. You need lerger ones...

[Buhl]

Thanx audioPT - you're absoluteley rigth, but I did'nt want to use the best wire just for this teporary setup - the new heatsinks Im waiting for should make it possible to mount the boards directley on the heatsink, thus no wires to the FETS. I moved the 221 ohm gate resistor directley on to the FET Q1, and it made a lot in difference, so I think that moving the whole FET close should also improve the sound. I'm very happy with the sound, except I think it sounds a little dull in the high frequences - dunno if this is caused by the 240 indstead of 044, or the long wires to the FETS??

Cheers !
Hans

[Anorgan]

I think I read somewhere on this forum that 140 is better (I could be wrong). Can you use 054 instead 044, what about 250, what about 2 140's ???

[Buhl]

Originally posted by Anorgan
I think I read somewhere on this forum that 140 is better (I could be wrong). Can you use 054 instead 044, what about 250, what about 2 140's ???

Yes, the Z4 article reads that 140 or 240 is a good substitute for 044 if you want to cranck the regulated supply up above 50 volts - mine is 47 before and about 42 after the capaciance multiplier, so 044 should be enough - but the problem is that I cant get the "real" 044, but only the 044N, witch has other datas.
Talking data, the most important figure in the Zen4 should be the input capacitance, or Ciss, witch could be the cause of my problem with high frequency rollof - but the funny thing is that when I compare data, the 240 has very low Ciss compared to the 044 devices:

Ciss
IRFP240: 1300 pF - 150W, 20A, 200V
IRF044 : 2500pF - 180W, 57A, 60V
IRF044N: 1500pF - 120W, 53A, 55V
IRFP140N: 1400pF - 140W, 33A, 100V

The suggested 044 has the highest Ciss of them all, but of course, I migth not understand the Mosfet testing article from passlabs well enough - it states that the values in the datasheet is not always applyable to real life situations - hence the article about testing.....

I will order a couple of 044N, they are only 2 euro or 2½ dollar, so I think I can afford a try - though, I have the feeling that when I mount the boards directly on heatsinks I will get better high frequency performance.....

Cheers !

Hans

[Nelson Pass]

All these parts sound a little different, some having more
transconductqnce but with more capacitance, and so on. In
the case of higher transconductance, the amp specs better
at low frequencies and usually not as well at the higher. The
spectral balance shifts also, so it's worth trying different
devices out. Since I often tri or quad amplify, it's reasonable
to select devices for the different drivers, even with an
otherwise identical circuit.