Building an Aleph 5...two quick questions

GregH2 · 10th August 2010, 11:06 AM

So here they are:

1) For the 1 ohm (power mosfet source resistors) and 0.47 ohm ( x4 output resistors), is a 5 watt rating for each sufficient?

2) What kind of capacitor is recommended for the 680pf and 10pf caps? Silvered Mica, Ceramic?

Your advice is most appreciated.

Greg.

Bill Fuss · 10th August 2010, 11:47 AM

Hi Greg,
5W is plenty, I used 3W mil spec. Dissipation is less than 1W.

I can't remember any discussion about those caps, I used silvered mica.

GregH2 · 10th August 2010, 12:06 PM

Thanks Bill. My simple calcs using ohms law suggested the same thing but I found a design on the web that used 10W resistors so I thought I'd better check

galop · 10th August 2010, 01:07 PM

1.enough (maybe try metalfilm 2w)?
2.silver mica

Bill Fuss · 10th August 2010, 03:33 PM

Oh yeah, it will bias higher than your paperwork says so don't get nervous unless your heatsinks are marginal.

GregH2 · 26th August 2010, 01:21 PM

Hi Guys,

I actually am building an Aleph 2 now, but thought I would post this question here rather than start a new thread.

Just wondering if 0.5 watts is a high enough rating for the 9.1v zener diodes used to bias the input current source and protect the input fets from static?

Your advice is appreciated.

Regards,

Greg.

jacco vermeulen · 26th August 2010, 01:37 PM

Should be fine for rails under 2000Vdc.

boatbuilder · 17th March 2011, 08:09 PM

hello.

i am having problems with my Aleph-5.
actualy, it is the power suply what is giving problems.
i am using 2X30v what gives me 40.8v after reg.
is this a problem and if so, what can i do to get it right?

h_a · 18th March 2011, 07:18 AM

Sounds a bit like you bought a 30VAC toroid that gives 30xsqrt(2)=42.3 VDC as output voltage (minus 1.4 V of the recitfier bridge plus the voltage regulation of the toroid).

If so, you can either use the higher voltage to feed your Aleph5 (and lower bias to get power dissipation down, maybe not so nice option) or get a 21 or 22 VAC toroid.

Hannes

boatbuilder · 18th March 2011, 08:42 AM

the toroids do give 2 x 30v and i do whant to use them.
i bought it all together as a set from someone who did not have the time to finish the project.
so if it is possible to use the, then i would like to know how to lower the bias.
i am using the pcb from KK.

10th August 2010, 11:06 AM	#1
GregH2 diyAudio Member Join Date: Oct 2009	Building an Aleph 5...two quick questions So here they are: 1) For the 1 ohm (power mosfet source resistors) and 0.47 ohm ( x4 output resistors), is a 5 watt rating for each sufficient? 2) What kind of capacitor is recommended for the 680pf and 10pf caps? Silvered Mica, Ceramic? Your advice is most appreciated. Greg.

26th August 2010, 01:37 PM	#7
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, Rotterdam or Curaçao	Should be fine for rails under 2000Vdc. __________________ Not so much,.......if it says "ZM" in the corner.

18th March 2011, 07:18 AM	#9
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	Sounds a bit like you bought a 30VAC toroid that gives 30xsqrt(2)=42.3 VDC as output voltage (minus 1.4 V of the recitfier bridge plus the voltage regulation of the toroid). If so, you can either use the higher voltage to feed your Aleph5 (and lower bias to get power dissipation down, maybe not so nice option) or get a 21 or 22 VAC toroid. Hannes __________________ fresh matched IRFP240/IRFP9240 fets \|\| AlephJ/JX-kits F5 transistor kits \|\| Burning Amp BA-1/2 transistor kits

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10th August 2010, 11:47 AM	#2
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	Hi Greg, 5W is plenty, I used 3W mil spec. Dissipation is less than 1W. I can't remember any discussion about those caps, I used silvered mica.

10th August 2010, 12:06 PM	#3
GregH2 diyAudio Member Join Date: Oct 2009	Thanks Bill. My simple calcs using ohms law suggested the same thing but I found a design on the web that used 10W resistors so I thought I'd better check

10th August 2010, 01:07 PM	#4
galop diyAudio Member Join Date: Jul 2009	1.enough (maybe try metalfilm 2w)? 2.silver mica

10th August 2010, 03:33 PM	#5
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	Oh yeah, it will bias higher than your paperwork says so don't get nervous unless your heatsinks are marginal.

26th August 2010, 01:21 PM	#6
GregH2 diyAudio Member Join Date: Oct 2009	Hi Guys, I actually am building an Aleph 2 now, but thought I would post this question here rather than start a new thread. Just wondering if 0.5 watts is a high enough rating for the 9.1v zener diodes used to bias the input current source and protect the input fets from static? Your advice is appreciated. Regards, Greg.

17th March 2011, 08:09 PM	#8
boatbuilder diyAudio Member Join Date: Dec 2009	hello. i am having problems with my Aleph-5. actualy, it is the power suply what is giving problems. i am using 2X30v what gives me 40.8v after reg. is this a problem and if so, what can i do to get it right?

18th March 2011, 08:42 AM	#10
boatbuilder diyAudio Member Join Date: Dec 2009	the toroids do give 2 x 30v and i do whant to use them. i bought it all together as a set from someone who did not have the time to finish the project. so if it is possible to use the, then i would like to know how to lower the bias. i am using the pcb from KK.

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