Search found 11309 matches

by Nick
Fri Nov 16, 2018 1:45 pm
Forum: Assorted Stuff
Topic: ethan winer null box
Replies: 6
Views: 81

Re: ethan winer null box

by Nick
Fri Nov 16, 2018 12:25 pm
Forum: Assorted Stuff
Topic: ethan winer null box
Replies: 6
Views: 81

Re: ethan winer null box

Probably the same as if it was posted here. Is there a full circuit diagram of the thing anywhere? I use something similar (A distortion multiplier) to show the distortion component of power amps, but that assumes the DUT has gain and does allow for compensation of phase shifts. Personal, I am not s...
by Nick
Thu Nov 15, 2018 11:52 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

Am I being unrealistic on an amp like this?
IMHO, no, less than 10mv should be achievable with a SET, so I would expect a PP will be able to be much quieter,

Looking at the hum is the next step IMHO,
by Nick
Thu Nov 15, 2018 12:05 am
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

The next thing to address is more hum/buzz that appears without the HT on. It's now the most disturbing thing. I'm not sure where this comes from other than the obvious (the fils) but why? It's as if the fils couple into the plate and so the Opt. Quite how I fix this, I don't know. Any ideas? Cheer...
by Nick
Tue Nov 13, 2018 10:11 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

I have used these before

https://www.rapidonline.com/vishay-534b ... er-65-1020

You can increase the power rating by adding parallel resistors across the ends to the wiper.
by Nick
Tue Nov 13, 2018 4:23 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

It may not work, but if you have another hum pot it may be easy to try. As Mike said, something like this
by Nick
Tue Nov 13, 2018 8:56 am
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

Are the filament connections "in phase" ? There is some info here on PP filament heating. http://www.bartola.co.uk/valves/category/valves/push-pull-designs/ So, nice and clean (ish) 50Hz. Swapping one of the filament connections is worth trying. You can increase the effective power rating of the po...
by Nick
Tue Nov 13, 2018 8:54 am
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

Are the filament connections "in phase" ? There is some info here on PP filament heating. http://www.bartola.co.uk/valves/category/valves/push-pull-designs/ So, nice and clean (ish) 50Hz. Swapping one of the filament connections is worth trying. You can increase the effective power rating of the po...
by Nick
Mon Nov 12, 2018 11:11 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

So, nice and clean (ish) 50Hz. Swapping one of the filament connections is worth trying. You can increase the effective power rating of the pot by adding resistors to either end so it only covers a smaller area around the middle.

That does look like heater supply hum to me.
by Nick
Mon Nov 12, 2018 8:59 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

I have a question for the panel. Is it possible the hum could be an issue with cathode bias but maybe less so if the fils were grounded and I used fixed bias? I ask as it is something I tried in previous versions but not methodically. I have the transformers to do it but don't want the detour unles...
by Nick
Mon Nov 12, 2018 11:16 am
Forum: Assorted Stuff
Topic: Nothing In Particular
Replies: 9972
Views: 570249

Re: Nothing In Particular

jack wrote:
Mon Nov 12, 2018 10:52 am
Oh! No!

https://twitter.com/MaxFagin/status/1058062583511404545
Why "Oh! No!" ?

I thought the new definition made a lot of sense and was reproducible instead of one lump of metal being "it".
by Nick
Mon Nov 12, 2018 11:14 am
Forum: Speakers
Topic: DIY LS3/5a..."This is the BBC speaker-ing...."
Replies: 38
Views: 4279

Re: DIY LS3/5a..."This is the BBC speaker-ing...."

Dave the bass wrote:
Mon Nov 12, 2018 10:13 am
Thermionic Idler wrote:
Sun Nov 11, 2018 10:24 pm
I know Harbeths have come in for a lot of stick here ....
They do? That's news to me.
Yep, me too. You may be thinking of somewhere else?
by Nick
Sun Nov 11, 2018 9:42 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

Not sure why I would see 100Hz from the filaments as they are AC. I thought that would appear as 50Hz? Depends on if a induced voltage (50Hz), or a heating effect (100Hz) Just having a equal voltage on the transformer may not be ideal as you dont know what the resistance of the heater means WRT the...
by Nick
Sun Nov 11, 2018 7:16 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 77
Views: 999

Re: The Nemesis 813 PP Amplifier

50Hz may just be a earthing issue or the heaters, I would expect 100Hz from the power supply or the heaters (as well).
by Nick
Sun Nov 11, 2018 6:03 pm
Forum: Instruments
Topic: Any recommendations for an electro acoustic
Replies: 4
Views: 87

Re: Any recommendations for an electro acoustic

Do you mean something like a Ovation, an acoustic with built in pick-up, or a semi acoustic type?

Chris will know what the world of pick ups is like now, but I would have thought you can just fit a pick-up if she has an existing acoustic she likes.