Aleph 1.2 two new problems

[Steve Fay]

Frist I would like to thank everyone for their help with my problem with the LED. Two new prolbems thou I could use some help with.

1.I've have a ground loop hum. With the amp pluged in and attached to the speaker no hum at all, once I connect a RCA interconnect from the preamp I've have a really bad hum, if I incert a 3 to 2 ground elminating plug the hum is gone. What have I done wrong?

2. Last night I listen to my Aleph for about four hours. After 2 hours or so the amp would cut out breifly (may be a slight pop) almost like a bad spot on a CD surface. I kept listing, never turned it off and about every 10 to 30 minutes it would do the same thing and never got any worst or better???:any help?

Thanks
Steve

[kilowattski]

Go to PassDIY.com and look at the Penultimate Zen power supply schematic. You will see a bridge rectifier between the supply ground and earth ground. This is Nelson's ground loop buster. It helps allivate Ground Loops while maintaining the safety of having your chassis connected to earth ground.

[wuffwaff]

HI Steve,

when using an unbalanced input you MUST ground the -IN!

If you use an input cap you must use one on the -IN too and ground before that.

William

[highbias]

While input ground must obviously be connected be very sure that your input ground is in no way directly connected to the chassis... either through the pcb or though your wiring.

"Go to PassDIY.com and look at the Penultimate Zen power supply schematic. You will see a bridge rectifier between the supply ground and earth ground. This is Nelson's ground loop buster. It helps allivate Ground Loops while maintaining the safety of having your chassis connected to earth ground."


You can do the same isolation thing with a CL-60 as is done in Pass's production amps.



Also go here and read Nelson's excellent and easy to understand paper on ground loops.......

http://www.passlabs.com/downloads/ar...ound-loops.pdf

I recently built an Aleph 3 that had a slight hum in it..... never had this happen before after checking things out low and behold there input ground was connected to the pcb's ground plane and in turn to the chassis through the plated through pcb mounting holes. That caused the hummmmmmm. After grinding those points away in the pcb all is quiet.

Not sure on the popping sound, double check all your wiring and be sure you soldered everything really nicly. It might be a flakey device, or a static problem. I would reccomend that you fuse your speakers till you find the culprit though. That pop could be caused by almost anything in the amp.

BTW Steve, I am originally from St. Charles, IL. Been out here for almost 10 years now. The only thing I miss back there are the St.Charles and Sandwich flea markets .
I'm sure that you definately have the best amplifers in all of Sandwich though!!
Mark

[Steve Fay]

Thank you Guys (Kilowattski William and Mark), I did read those articles and had inplemented the use of a Cl-60,but I found a new way of screwing that up. Simple fix and the hummmm is GONE !!! and I learned something new.
On the other sebject of my bief power outage, I listened to music for about 5 hours last evening and 31/2 hours into it:it reared it ugly head as if someone had turned off the power switch and turned it right back on, no noise associated with it. Ten minutes went by and it did it again, I continued to listen, it didn't do it again for one hour, then about ten minutes later.
So I was thinking maybe the amp was right at that thresehold temp wise it would shut down. Into the kitchen I went and stole my wifes pampered chef thermoeter/timer and checked the heat sink temp it was at 122f (I may get the fring pan later today if i don't get back into the kitchen soon she is cooking the turky). Idon't know is that ok or not? Is that to hot?
The other thing I'm questioning my self about is I used .01 metal film caps to bypass the 600V 25A Hexferd Diodes in the power supply (which I shamless stole from W. Sankey nice boards I might add) the cap are rated 1200VDC I'm worried now because they're not rated VAC could this be a problem?
Mark funny you mentioned the Fea markets My wife and I go to all most every one and really have fun. I briefly lived in Salt Lake when I was young(only for about 2 mos.) it is truly beautiful.

Thank you,
Steve

[Nelson Pass]

Originally posted by Steve Fay
On the other sebject of my bief power outage, I listened to music for about 5 hours last evening and 31/2 hours into it:it reared it ugly head as if someone had turned off the power switch and turned it right back on, no noise associated with it. Ten minutes went by and it did it again, I continued to listen, it didn't do it again for one hour, then about ten minutes later.

Sounds like a connection is being made and broken thermally.
Starting by resoldering every connection in the amp. If it was
only one channel, switch input channels to make sure that its not
the source. If it's both channels, then its either the power supply
or the signal source.

[Steve Fay]

Thank you Nelson. I'll try that today.Do you think the caps I mention as bypass could be a problem or the temp on the heat sinks 122 F.??

Thanks
Steve

[Brian Donaldson]

122 deg F isn't anything. I had my Alephs up to 175 deg F with the help of a variac, a friend, and 12 fine ales

I did later have a few random fet failures. But up to 150 or so isn't a problem

[Steve Fay]

Brian
Great anwser! Thank you that relieves my mind. Any help on the last question about using the 1200 VDC rated caps to bypass the Hexfreds is that ok??

THanks Again
Steve

[highbias]

1200 volts is a pretty safe margin IMHO for bypassing. Half that rating would still be very safe!!

Mark