Search found 11377 matches

by Nick
Mon Dec 17, 2018 11:15 am
Forum: Valves
Topic: Finished and working - 12 valve all DHT PP 26-71a-45
Replies: 76
Views: 3040

Re: Finished and working - 12 valve all DHT PP 26-71a-45

But how do you measure the current in each valve?
by Nick
Mon Dec 17, 2018 8:52 am
Forum: Valves
Topic: Finished and working - 12 valve all DHT PP 26-71a-45
Replies: 76
Views: 3040

Re: Finished and working - 12 valve all DHT PP 26-71a-45

Or you could use the scope starting with no B+ and check the signal on the first two grids and work forward. I wouldn't have thought those DHT's would need grid stoppers, thats normally for RF, a squeal is in the audio band so more likely to be feedback of some sort. One thing that occurs, what opti...
by Nick
Sat Dec 15, 2018 10:48 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 195
Views: 3673

Re: The Nemesis 813 PP Amplifier

Yep,
by Nick
Sat Dec 15, 2018 10:46 pm
Forum: News
Topic: Sakuma
Replies: 5
Views: 89

Re: Sakuma

:-(
by Nick
Sat Dec 15, 2018 7:48 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 195
Views: 3673

Re: The Nemesis 813 PP Amplifier

The first gets my vote as its going to be simpler to adjust each valve on its own. You can make them failed pot safe by adding a 1M resistor between each wiper and the -ve rail. What the 180k resistor doing BTW?
by Nick
Sat Dec 15, 2018 10:21 am
Forum: General Vinyl
Topic: Latest vinyl 'finds'.
Replies: 426
Views: 51473

Re: Latest vinyl 'finds'.

Its got this nice thing to confuse HiFi folk at shows



Though the pressing is a real test of tracking, its recorded at a very high level.
by Nick
Thu Dec 13, 2018 10:26 pm
Forum: Everyones Projects
Topic: Remember These?
Replies: 216
Views: 4427

Re: Remember These?

Just FYI, I have used these in the past to disconnect HT. Specifically in the ref phono if someone unplugs the connection between the two boxes CE specifies how log a voltage can remain on the pins. I detect the removal and use these to isolate the caps in the power supply while they discharge. Just...
by Nick
Thu Dec 13, 2018 3:50 pm
Forum: Assorted Stuff
Topic: Nothing In Particular
Replies: 10068
Views: 588110

Re: Nothing In Particular

Well, I installed the xmas extensions for the rescue forum and though I would give you guys the benefit as well.
by Nick
Thu Dec 13, 2018 8:53 am
Forum: Everyones Projects
Topic: Remember These?
Replies: 216
Views: 4427

Re: Remember These?

Well, a DC detector and relay wound protect from a failed cap. Not sure how a zener will do any more than a cascode, but I probably don't understand how you suggest using it. I would have thought the rate of cap failure would be low as long as its rated properly. A fast blow Fuse in the B+ would add...
by Nick
Wed Dec 12, 2018 10:48 pm
Forum: Everyones Projects
Topic: Remember These?
Replies: 216
Views: 4427

Re: Remember These?

Mike H wrote:
Wed Dec 12, 2018 3:40 pm

One thought that occurs to me is you could use something that is based on a high Voltage MOSFET. Which won't care if its drain is taken up to HT level.
You could use a mosfet as a cascode above the CCS, but it will eat a bit of the headroom.
by Nick
Wed Dec 12, 2018 12:37 pm
Forum: Everyones Projects
Topic: Remember These?
Replies: 216
Views: 4427

Re: Remember These?

You could try taking the feedback from before the output cap and adding a blocking cap in the feedback loop (can be much smaller). Stops the feedback from working to correct the output cap low pass filter.
by Nick
Tue Dec 11, 2018 3:32 pm
Forum: Assorted Stuff
Topic: Nothing In Particular
Replies: 10068
Views: 588110

Re: Nothing In Particular

Its a Jpeg Image file being displayed on a browser.
by Nick
Mon Dec 10, 2018 1:53 pm
Forum: Assorted Stuff
Topic: Owston meet 2019 >1&2 June
Replies: 36
Views: 1472

Re: Owston meet 2019 >1&2 June

we've had them in November before now - would be much better for me.
Historically though those were less well attended, and the weather made them a bit less fun (IMHO).
by Nick
Mon Dec 10, 2018 12:02 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 195
Views: 3673

Re: The Nemesis 813 PP Amplifier

The fact that you are using a interstage helps a lot for fixed bias, so worth a try.
by Nick
Mon Dec 10, 2018 12:01 pm
Forum: Everyones Projects
Topic: The Nemesis 813 PP Amplifier
Replies: 195
Views: 3673

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 ...