kambo

Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #360 on: June 27, 2019, 02:14:30 AM »
maybe google
DC blocking caps on phantom power schematics


Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #361 on: June 27, 2019, 02:49:54 AM »
... readings between pin 2 and 1 on the input XLR are 44.6V. Same between pin 3 and pin 1. Any ideas? Is it too low?

44.6 Volts with a connected condenser microphone or without?
« Last Edit: June 27, 2019, 02:56:45 AM by rock soderstrom »

bernatvm

Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #362 on: June 27, 2019, 03:13:01 AM »
That's without a microphone pluged

bernatvm

Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #363 on: June 27, 2019, 03:15:28 AM »
maybe google
DC blocking caps on phantom power schematics

I understand you don't need DC blocking caps if there's an input transformer in the circuit...

Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #364 on: June 27, 2019, 03:37:12 AM »
That's without a microphone pluged

Measure it with a microphone pluged in. It is very possible that your Phantom Power will sag under load. How do you realize Phantom Power? Schematic?

bernatvm

Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #365 on: June 27, 2019, 04:05:24 AM »
With microphone pluged i get 1.8V, which i can see is a very bad reading  :o I'm using Bo-hansen phantom psu, attached. Also I have a resistor between the + on the psu and the two 6k810 to reduce voltage, because it was 52 V without mic plugged in.

Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #366 on: June 27, 2019, 04:17:55 AM »
With microphone pluged i get 1.8V, which i can see is a very bad reading  :o I'm using Bo-hansen phantom psu, attached. Also I have a resistor between the + on the psu and the two 6k810 to reduce voltage, because it was 52 V without mic plugged in.

1.8 volts is not enough for most condenser mics  ;)

Remove the additional resistor, 52 V unloaded is ok. Check again your voltage under load.  Thats important...
« Last Edit: June 27, 2019, 04:29:24 AM by rock soderstrom »

bernatvm

Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #367 on: June 27, 2019, 12:38:03 PM »
Removed resistor and now I mesure 38.4V and working!! Now I have to play with it a bit. What should I expect with the range knob, should de flavor of the tubes be more present in higher positions?

Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #368 on: June 27, 2019, 01:22:36 PM »
38,4V is still on the low side, some mics will not work with that. AFAIK, the Phantom Power standart is 48V +/- 4V.

Your PP circuit is pretty basic, there are better ones, with regulation and load independent 48V.

The MILA circuit sounds pretty clean, in my opinion the less negative feedback (=higher gain setting) the more tube "sound".  You can experiment wird other tubes as well.  There is version with 6CG7 (noval 6SN7) tubes...     

bernatvm

Re: NewYorkDave Mila Dual Tube Preamp Help Thread
« Reply #369 on: June 27, 2019, 07:03:43 PM »
Can you recommend me a better phantom psu circuit?




 

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