yvus

Re: 6N1P Bass DI - Revisited
« Reply #80 on: November 22, 2020, 05:54:42 AM »
Hello guys,

Thank you for this very useful thread. I built 2 units based on the scheme showed in the first message and they sound great. I used Carnhill transormers. Both units are in the same box and are powered by the same PSU.
When i test each unit individually, i get a B+ voltage of about 190 V with about 3 V on the cathode resistor (which is 220 Ohm as stated on the diagram). However, when the two units are feed in parallel from the PSU, the B+ voltage drops to about 150 V with a cathode voltage of 2,2 V approximatively and I can not figure out why ? The low voltage supply for heaters remains quite stable in both cases.

Do you have any idea ?

Thanks.


ruffrecords

Re: 6N1P Bass DI - Revisited
« Reply #81 on: November 22, 2020, 12:58:03 PM »
If the HT supply uses simple RC filtering then the additional current draw of two using will drop the HT and alter the operating point which is reflected in the cathode voltage.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

yvus

Re: 6N1P Bass DI - Revisited New
« Reply #82 on: November 22, 2020, 04:43:53 PM »
Since the HT supply in the build I'm testing indeed uses simple RC filtering, it makes sense. Thank you for your answer, I will check this out.
« Last Edit: November 22, 2020, 05:31:03 PM by yvus »