System Gain

[xcortes]

What output can I expect from a tube repro with, say, Flux Magnetics ER heads on the single ended output?

IIRC I should be getting "equivalent to CD" or 2V rms peaks, right? If so, why not just bypass the driver tubes in my amps? 2V rms is 2.8 peaks which after the BeePre become 11.2V. Assume 4x gain for a 300B output stage that's 44.8V at the plate. Using 3000:8 transformers the gain is -19.4x leading me to 2.3V at the 8 ohm tap. 800 milliwatts.

Are these assumptions correct?

If so I can get rid of one stage per amp and drive the output tubes with more punch from the large current of the BeePre vs the 3.5mA of the Paramount drivers?

Thanks a lot

[Doc B.]

Probably more like .6V rms than 2V rms.

[xcortes]

Thanks Doc. So if the rest of my calculations is right I'm getting a quarter of a watt. The least efficient transducers are the midbasses at 106dB per watt so I'll be getting 100dB on those. I'm tetraamping. Oversimplifying doubling the speakers and amps would give me 6dbs and doubling them again another 6dBs. That's 112 dBs. Of course the oversimplification is there since not all soeakers playi all frequencies but looks like i've gotta try.

[Paul Joppa]

Be careful about signal levels; tape and phono are usually quoted relative to typical peak VU, which for well-recorded typical orchestral music is ~14dB below clipping. CD and digital are quoted at clipping (FS = Full Scale). Much of the available low-grade pop recordings are done with as little as 1 or 2dB headroom instead of the traditional 14dB (or the 20dB typical of well-done THX movies).

Calibration tapes and phono discs are not necessarily recorded at a standard level so you must not only determine what level they are at, but also what the zero-VU and clipping levels may be. It's a jungle.

[xcortes]

Thanks Paul. I guess this is one where trying is the only way of finding out. I will do that.

Thanks!

[xcortes]

And of course the easiest way to try is see how much I attenuate when I attenuate the least. If it's always more than 31dBs (the paramounts driver gain with soft start) I'm ok getting rid of such stage.

[xcortes]

I found last night that with 5 extra dBs (after taking the driver stage out) I could get to a volume level that will get me to where I listen to 90% of the time.

So I'm skipping a stage and using the voltage and current headroom to sr and c4s!