What Power Amplifier Should I Buy?

I'm not sure if anyone is still paying attention, but...

My time with the BP-17 has come to an end. I could not get rid of the sibilance that drives me crazy. The ergonomics are OK, but nothing like the Levinson 38s. I've listed it, but not on Audiogon yet.

Now I use my old, old Paragon System E as a line preamp and a phono preamp. I still use the 38s, but now it is relegated to volume control because it has a remote. The Paragon does not.

This is the best sound I have gotten so far. I have rebuilt the Paragon PSU, replacing all components except the transformer, so it should be good for a while.

The Paragon is a tube preamp with six 12AX7 tubes. I've got new tubes (JJ). It was sold in the late 70s through the mid 80s. I bought mine new.

I'm finished with this quest. Although I have not found the Grail, I am quite pleased with the relics that I have. I've firmly decided I don't need an amp with more power output.

Gotta go buy some records. My gear search has ended.

@kevemaher

Your Bryston 2.5B cubed specs show:

Power Output (per channel): 135W @ 8Ω | 180W @ 4Ω

However, Stereophile F208 review here suggests you need more current:

…. F208 will need to be driven by a good 4 ohm-rated amplifier…..

and that there was plenty of bass. Therefore a more powerful amp with adequate current is likely better than adding subs

Generally, a speaker rated at 8 ohms only hints at being average to easy to drive, while a 4 ohm is harder. But a further look into the frequency vs impedance/phase test/chart of the F208 reveals it needs more power

@kennyc 

Thanks for reminding me about this. I've seen the impedance plot on ASR. There is a dip to 3.7 ohms at about 100 Hz and 3 KHz.

I also measured the voltage into the speakers while I had the SPL at the listening position using pink noise. I found that I needed about 3 V, which is about 1 W for 8 ohms and 2W for 4 ohms.

I concluded that I have enough headroom to allow for a little higher SPL and for the low impedance at the above frequencies (100 Hz goes to my self-powered sub).

@kennyc 

Just looked at Bryston's published spec. It is rated at 180 W into 4 ohms. So it is rated at 4 ohms. However, I was cautioned that if the impedance was below 4 ohms for a large part of the spectrum, especially in the midrange, there could be problems.

I have never seen any of the overload lights turn red, although maybe that doesn't mean much.

I really haven't experienced anything audible or measured any parameter with REW that would indicate problems.

Am I thinking properly here?

Both Stereophile and ASR test show plenty of bass down to 30hz. Your 14x19x8h room looks fine, but the other impedance show the F208 is harder than average to drive. Conclusion is that you don’t have enough power. Also, if one defines “average” needed power to run most speakers, seems to be in the 150-300watt at 8ohms range, somewhat doubling down to 4ohms.

If you love your amp, I suppose you could try to fill in the missing bass, but my preference would be to get the bass from the speaker since it’s matched to the other transducers (mid treble).

Maybe you can test by borrowing a more powerful 4ohm amp?