My Review of the Apex Pinnacle (and comparison to the 307a) - Page 7

Quote:

Originally Posted by DavidMahler 

It was my understanding that the 307a had a lower damping factor than the Pinnacle. Is this correct? Is the damping factor caused by the tubes?

I dont know if its correct.

Damping factor, or output impedance, in tube amps is a combination of the tubes and output transformers. Since the 2 amps use different output transformers its really hard to guess because there are several variables changing at once.

That being said, with most headphones I'd argue that it doesn't matter much either way and more often than many would admit defies common rules of thumb with higher output impedances (lower damping factor) sounding better! 

The biggest problem with high output impedance amps (low damping factors) and multi way speakers with passive crossovers is that speaker crossovers are designed around a specific amplifier output impedance - almost always ~0 ohms. When you change the output impedance of the amp you change the crossover frequencies and things get very weird very fast with crossovers that no longer line up and create funky peaks and dips in the overall frequency response. Nobody likes that, and high-output impedance amps get a bad rap.

With single driver speakers and headphones (neither of which typically have crossovers) you have tons of freedom to experiment and highish output impedances often sound much better than ~0ohm output impedances. 

Quote:

Originally Posted by DavidMahler 

It was my understanding that the 307a had a lower damping factor than the Pinnacle. Is this correct? Is the damping factor caused by the tubes?

Correct.  Same OPT impedance (roughly) in both amps, but the triode connected 307A has a bit higher plate resistance than the PX4.

As nikongod points out, this is not necessarily a good or a bad thing.  Depends on the headphones and listener preference.

For example, I can't stand Grados if driven from a high DF amp, but they are OK from a low DF amp.  On the other hand, K1000's seem to prefer a high DF.  But that's only to my ears...

Pete

 

fwiw, listening to the K1000 out of the 307a was the best I've ever heard those phones sound.  I thought the combo was amazing.

Out of curiosity, what other amps have you used with the K1K?

Cmoys.

Very interesting thread -- thanks to DM, PM and the others who added to our understanding of this SOTA amp. It's made me want to hear its little brother (the Peak). Gotta love trickle-down engineering.

best,

o