Merry Christmas everyone!! (pics of new build)

[Happy Ghost]

I think I finally get it.. Assuming a gain of ~ 53 DB, and with the controls set for -20 (Coarse+ fine), I am getting 33DB out.. And before the stepped attenuator, with the logarithmic volume pot at ~ 8 'o clock region, gain must be ~ 36dB. So quite close and i guess it was a false alarm Hope my math is alright..

[Paul Birkeland]

The attenuator takes away from what comes into the C2A.  Gain is what the circuit adds. 

If you have an extra step or two on the coarse attenuator you are miles from running out of gas.

[Sp33ls]

I'm at about -27dB right now using a Dragonfly Red (my workstation DAC) into my HD800S. I run the Dragonfly at max volume into the C2A, which is supposedly around 2.1V.

I don't think I want to really go any louder than this except for some classical tracks which are mastered with more dynamic range.

The -18dB mark would likely cause acute hearing damage when combined with this DAC lol.

But my goodness does this amp sound great with the 800S.

How much THD would you guesstimate is present with a Bendix 6080 & Telefunken 12AU7 @ 1mW? Think it's somewhere in the 1-3% range?

[Paul Birkeland]

I could take some measurements sometime of the C2A I have here.  I think I have that particular tube set as well. 

[Sp33ls]

I could take some measurements sometime of the C2A I have here.  I think I have that particular tube set as well.

Would be really interesting to know!

From a selfish perspective, it'd be interesting to get a rough feel on "okay, so this is what about 1% THD sounds like"... Of course, the distortion profiles vary, even from tube to the tube.

I'm assuming something like the BeePree 2 has a bit less of the tube sound than the C2A, but still shares the typical sonic benefits associated to tubes?

[Paul Birkeland]

The sonic signature of a 300B is a fair bit different than a 12AU7.  The 12AU7 somewhat intentionally a tubey sounding choice, as there's a reasonable amount of non-linearity, especially with the stock plate loading resistors.

The 300B is definitely not as tubey, as it's a very linear device.  It has a notable amount of weight and punch that I can't seem to get out of any indirectly heated tubes.  I wouldn't really want the 300B in front of the 6080 in a headphone amp though, as they aren't super duper quiet, and that's very important in a headphone amp.