6V6 line preamp

[Salas]

That's only 0.66dB less than 2V. Very near to your goal considering you used what resistor values you had handy.

 

[merlin el mago]

Isn't measured, it's only calculate.

 

[Salas]

If you got 0dBFs test tones in file or CD you can playback and measure.

 

[merlin el mago]

Yes I have 1kHz 0dBFs DSD files ready.

 

[merlin el mago]

Gone where? What happened to the capacitor?

Attached pic.

 

[merlin el mago]

Salas attached pics with measurements. Left pic SG output, middle right channel output & right channel output.t It seems the gain x3.6 is OK.

 

[Salas]

Nice. Surely enough for the NoDAC. No volume pot in your case adds no series resistance to Ri so final gain is bit higher than my estimation that includes 50k volume pot output resistance.

 

[Salas]

Channel matching regarding gain reads excellent too. Depending mainly on Rf Ri value tolerances.

 

[Salas]

Brymen "no Disc" so KO.

The capacitor's leg internal connection maybe broken.

 

[merlin el mago]

Nice. Surely enough for the NoDAC. No volume pot in your case adds no series resistance to Ri so final gain is bit higher than my estimation that includes 50k volume pot output resistance.

As per your advice I added 1Meg across input.

 

[merlin el mago]

Channel matching regarding gain reads excellent too. Depending mainly on Rf Ri value tolerances.

Yes it's very close, also voltage for both heaters are very close.

 

[merlin el mago]

SSHV2 working hard to tame the high ripple coming from PSU, can't increase the resistor value between the CRC of PSU because I need each volt available, will do with the new transformer.

 

[merlin el mago]

The capacitor's leg internal connection maybe broken.

The BG are very old, when I left connected the BG to the Brymen a moment reads 220uF but prefer don't use it and left the big 820uF because when connected SSHV2 in problems to reach the 60mA...

 

[Salas]

You do well to avoid using it. Intermittent leg connection will bring sudden peak that will break something down the line.

 

[Salas]

SSHV2 working hard to tame the high ripple coming from PSU, can't increase the resistor value between the CRC of PSU because I need each volt available, will do with the new transformer.

Does good work. What the Brymen shows if you keep it connected to B+ but you power down the PSU? To see if its mainly general noise the test leads pick.

 

[merlin el mago]

Powered down the PSU letting to discharge to 3V, mesures 1.6mV residual noise very very near like powered!

 

[Salas]

Phantom noise it seems its the most part of reading!

 

[merlin el mago]

Yes I guess.

 

[vgeorge]

The BG are very old, when I left connected the BG to the Brymen a moment reads 220uF but prefer don't use it and left the big 820uF because when connected SSHV2 in problems to reach the 60mA...

Better safe than sorry with HV Felipe.

 

[merlin el mago]

Yes George first safe, thanks.