Search found 556 matches

by izzy wizzy
Tue Dec 11, 2018 4:35 pm
Forum: Assorted Stuff
Topic: Owston meet 2019 >1&2 June
Replies: 26
Views: 1216

Re: Owston meet 2019 >1&2 June

Any idea as to when things kick off Saturday? Thinking do I drive up Friday with potential horrendous traffic or leave early Saturday morning with potential for setup going a bit haywire? Driving from deepest Kent. This leads on to booking accommodation. Experienced comments welcome.

Cheers,
Stephen
by izzy wizzy
Mon Dec 10, 2018 10:08 pm
Forum: Assorted Stuff
Topic: Owston meet 2019 >1&2 June
Replies: 26
Views: 1216

Re: Owston meet 2019 >1&2 June

I'm going to stick it in the diary or calendar if I had a 2019 one yet. This will probably be my one and only chance to go ever so hopefully I can make it.

Cheers,
Stephen
by izzy wizzy
Mon Dec 10, 2018 2:26 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

Should have said Andrew not Mark. I know he is working (when he has time) on a high current variant, but not ready yet. 5A should be do able, I did 3A for a gm70 using a three pin reg as a current source, that worked ok, but did generate heat so needed a big heatsink. I had similar startup problems...
by izzy wizzy
Mon Dec 10, 2018 10:36 am
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

What I meant is that the SMPS may be injecting noice into the cathode because there will be effective capacitance between the SMPS output (cathode) and the mains input to the SMPS. Your 0v line in the amp will be refenced to the same mains lines, so will see that signal across the hidden caps. May ...
by izzy wizzy
Sun Dec 09, 2018 9:55 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

I've been reading Andrew's DHT reg thread. Skimming really as it's very long. I was hoping that maybe some of the participants could give me a management summary to a few questions. Is there a version that could do 10V @ 5A for the 813? It seems paralleling the filaments isnot such a great idea with...
by izzy wizzy
Sun Dec 09, 2018 8:22 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

Thinking about the hum pots not making a difference (evening dog walk), that may point to the problem being a signal introduced into the cathode WRT amp ground, via the SMPS input from earth and or line neutral. unlike indirectly heated valves, you can't just reference the output directly to 0v. OK...
by izzy wizzy
Sun Dec 09, 2018 6:42 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

Well that doesn't bode well. What did you do after that didn't work? I started using Andrews heater supply. I'm guessing that is probably the best solution. A proper DC supply be it Andrew's or Rob Coleman's. I should go and look at Andrew's thread again. The thing I'd really like to do is just use...
by izzy wizzy
Sun Dec 09, 2018 5:47 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

I did, at least according to my 100 MHz bandwidth 'scope. Altho I guess it helps to keep wiring out of the way of sensitive areas. See my PCL86 amp topic, I have separate SMPS units (1 heater, 1 HT), the filters are in the back of the amplifier case so it's filtered as soon as it comes into the box...
by izzy wizzy
Sun Dec 09, 2018 5:14 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

CMC will only take out the ultrasonic, but means the amp is not having to do something with it. :D And I guess it's that aspect that changes the sound so that will be interesting to try. I've yet to do a proper comparison between channels to see the sound difference. I never had much luck getting n...
by izzy wizzy
Sun Dec 09, 2018 3:17 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

Hum pot had no effect whatsoever. I guess it's a matter of filtering the output. Mike suggested the CM chokes. I would have thought some differential filtering would have helped too but not sure what to use. I'm guessing you just can't strap on some big ol caps to an SMPS without causing issues. Are...
by izzy wizzy
Sun Dec 09, 2018 1:29 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

Nick wrote:
Sun Dec 09, 2018 1:12 pm
Have you tried treating it like normal hum and tried to remove it with the hum pots?
No I haven't tried a thing yet other than starting to look at stuff on the web for inspiration. Not too hard to try I think. Thanks.

Cheers,
Stephen
by izzy wizzy
Sun Dec 09, 2018 12:29 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

This is what appears on the output terminals with no input connected. Looks to be directly related to the SMPS noise I think.
smpshumbuzzop.jpg

Cheers,
Stephen
by izzy wizzy
Sun Dec 09, 2018 12:25 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

It's about time to tear myself away from listening and do something responsible like try and troubleshoot the 813 filament noise. Overall, it isn't intrusive while music is playing that I notice at the moment but in between I can hear it. The amp is very addictive to listen to so would be nice if it...
by izzy wizzy
Wed Dec 05, 2018 10:38 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

This is starting to get exciting. The wierdness/volume clicking earlier has gone away. Might have had something to do with me mis reading the pin out for the input transformer. For some reason Lundahl show it looking down on the tx rather than the pin side. Although it's kinda symmetrical, something...
by izzy wizzy
Tue Dec 04, 2018 9:57 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 191
Views: 3235

Re: The Nemesis 813 PP Amplifier

Not much time tonight however I did stop the volume clicks by removing the earth on the screen of the interconnects :? This will require more investigation as I thought they were a screened twisted pair, earthed at one end. Previously when just driving the output stage, the earth was needed. Now not...