6V6 line preamp

[Salas]

Aha, you meen lower output in windows mixer so I get 1 VRMS out instead of 1,527?

I couldnt find out so instead I calibrated input with picoscopegen 1 kHz 1 V Pk-Pk instead of the Arta/soundcard gen. A more beleavable result in level I think?

Use RMS value level. Use the DMM on your pico ref, DMM reads RMS or just calc from pk-pk or ask pico software to advise RMS, all digital scopes do various.

 

[Salas]

Pico gen maybe means RMS already, just confirm.

 

[stajo]

Did a new try on calibrating.

1. Put the output level in windows mixer to 1 VRMS measured with Pico, it differs maybe some millivolts from the DMM.
2. Tried it on -3dB for input but it clipped
3. - 6 dB ok, set that for both channels
4. Input level as it was, on 100%
5. Take it down to 5%
6. New loopback measure

 

[stajo]

Pico gen maybe means RMS already, just confirm.

No I checked with DMM

 

[stajo]

Still my microphony is minimal.

Seems to come with inductors to the 6V6 in both anode and cathode applications. Vgeorge experienced the same. For some reason that I'm determined to find out

 

[Salas]

Don't reduce your input level so low, just calibrate it for reading 0dBV 1kHZ when you know you apply 1VRMS and notice your mixer levels for future use.

 

[Salas]

Defeat any input boost in the mixer, don't use mic input, use line input.

 

[flatheadmurre]

Seems to come with inductors to the 6V6 in both anode and cathode applications. Vgeorge experienced the same. For some reason that I'm determined to find out

Starve the heaters a bit more and check if that will calm down the ringing.

 

[stajo]

Don't reduce your input level so low, just calibrate it for reading 0dBV 1kHZ when you know you apply 1VRMS and notice your mixer levels for future use.

Ah. Thats what I told Iko a few posts ago. Arta guy says:

• Set the line-out volume for maximum output sensitivity
• Set the line-input volume near minimum output sensitivity

So I spoof that up. Have to figure out how to do this.

 

[iko]

Please do what Salas said. And PLEASE set averaging to linear!

 

[stajo]

Hold on guys, trying my best

ok now

1. Setting input to 1011 mVrms, as close as I could get, 78% in mixer
2. Enter 1000 mV Pk-Pk on input. DMM measure 680 VRMS on picos gen.
3. Graph with 100% input level

I couldnt find out how to calibrate for "0dBV 1kHZ when apply 1VRMS" so I pulled input to 100% istead. Sorry for my stupidity, first timer. Us oldies has to sleep on it sometimes

 

[stajo]

Anyways for you Iko

 

[Salas]

Use some number on Pico which it will yield 1V RMS Pico output on the DMM. Aplly to card's input, start reducing its sensitivity until ARTA says 0dBV RMS.

 

[stajo]

Use some number on Pico which it will yield 1V RMS Pico output on the DMM. Aplly to card's input, start reducing its sensitivity until ARTA says 0dBV RMS.

Thanks for your patience Salas. I will get around it. Im just a little slow

And if you guys hasnt gone drowned yourself over my stupidity heres now some measuremnts with the exact settings as last calibration, only now is the 6V6 on full volume setting inbetween instead of the dual female to female loopback adapter. Maybe that could give a compareness.

 

[Salas]

Its probably not too bad but the numbers are out as for dBV.

 

[stajo]

Its probably not too bad but the numbers are out as for dBV.

The "levels" ?

 

[Salas]

+26.4dBV is 20.9VRMS if real so get your levels right first so to read your hum right too.

 

[stajo]

Use some number on Pico which it will yield 1V RMS Pico output on the DMM. Aplly to card's input, start reducing its sensitivity until ARTA says 0dBV RMS.

+26.4dBV is 20.9VRMS if real so get your levels right first so to read your hum right too.

Ok, thanks. Picocrap only outputs max 1 V pk-pk (0,698 on DMM) so I will have to use old Wavetek for that.

 

[Salas]

Your SB card is capable of 1VRMS too. If you will use the Wavetek you are going to read no better than -50dB THD. Stick on the PC stuff for good THD. Take your time to understand and calibrate. These things are perplexing when new and trying on the fly. One step at a time.

 

[stajo]

Could we do it step by step cause I cant find out where I go wrong. I have now reduced SB output level to 79% and thats where Pico says 1,011 VRMS and DMM says 1,008 VRMS. I put 1011 mV at voltmeter (scope) value. Thats at -3 dB level which is the first.

Then I press accept and that value appears on the input sensitivity side.

If I then try to calibrate input with that output voltage I get the clipping warning so I change output level to -6 dB and get this value. Is that right so far? What now if so?