New DHT Line Stage

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Vinnie R.

Re: New DHT Line Stage
« Reply #340 on: 8 Jan 2019, 12:06 am »
Hi TimS,

Good question, but the VR MINI did not have enough continuous output current (especially not enough for a pair of 2A3 or SV811s).

Another thing that I have learned is that a floating supply for the filaments (like a battery, or isolated ultracap bank)
is not the best thing in terms of hum pick up.  Sure, the power itself is very clean, but it's a LOT more complicated with that
in terms of picking up 50/60Hz noise fields with the sensitive direct heated triode tubes themselves. 

With the L2 Preamplifier circuit, the way that I am referencing certain parts of the circuit to AC Ground and with the mesh tube covers in place (they also get tied to AC ground), there is no hum with any of the DHT tubes that I have tried!  It makes a big difference!  Certain tubes that I gave up on in the LIO DHT PRE (e.g. Psvane WE205-D Western Electric Replica) due to excessive hum are quiet in the L2 Preamp.  And the one switch filament selection on the back panel makes rolling tubes of different DHT families much easier.

Quote
Anything to squeeze the last ounce of goodness out of the already superb LIO DHT!

I'm investigating and highly considering things for LIO in 2019 - but I just can't go into any of it yet.  Sorry.  :shh:

In the meantime, keep those DHT tube sockets clean and tight - and enjoy it!  :singing:

Vinnie

TimS

  • Jr. Member
  • Posts: 92
Re: New DHT Line Stage
« Reply #341 on: 8 Jan 2019, 02:45 am »
Thanks Vinnie, look forward to any LIO upgrades this year.
Due to equipment changes I will soon have a spare output on my PH SR7 that I may try for the LIO DHT supply (@ 7.5v).  I'll update this thread when I've tried it.


Vinnie R.

Re: New DHT Line Stage
« Reply #342 on: 13 Jan 2019, 07:05 pm »
Thanks Vinnie, look forward to any LIO upgrades this year.
Due to equipment changes I will soon have a spare output on my PH SR7 that I may try for the LIO DHT supply (@ 7.5v).  I'll update this thread when I've tried it.

Hi TimS,

I do not recommend using an external supply for the DHT Filaments other than the LIO DHT Power Supply (which has an in-rush current limiter circuit to protect the Belleson super regulators used for the filaments.  The reason for this is that at time = 0 when you turn on the LIO, the tubes draw much higher current (in-rush current) than their normal steady-state current draw. 

Best regards,

Vinnie

TimS

  • Jr. Member
  • Posts: 92
Re: New DHT Line Stage
« Reply #343 on: 13 Jan 2019, 07:15 pm »
Ah, OK.  Thanks for that information Vinnie.  Don't want to damage the super regs!