My BHK signature arrived yesterday. Compared to what it replaced, the BHK sounds more transparent. It definitely has a sound signature, but it conveys more of what the DS alone conveyed.
The solo horn that begins the Brahms piano concerto (Anna Malikova) can easily be placed in the rear of the stage to the right using DS direct to my amps. Through the DHK, the horn is a bit more diffuse and less easily placed on the stage – this was with an hour of burn in.
Has anyone noted a change in the BHK sound after significant breakin?
Three days in, the BHK Preamp sound is breaking in in the right direction. Before the BHK, my system had a huge bump in frequency response below about 100 Hz. I THOUGHT this was speaker/room interaction; so, I made adjustments to my bass panel level.
Turns out, the frequency bump was preamp driven (the bump never really went away but was slightly reduced). The BHK exhibits no such bump; so, I’ve removed the prior adjustment.
I really like what I’m hearing with the BHK. I’m not a bass freak; so I love the realistic rendering of bass. Acoustic piano bass notes sound like a hammer on strings, not buzzy or electric sounding.
This is fascinating. My BHK pre has also been breaking in for three days and I have noticed a similar reduction in bass. I never would have associated this with the preamp either.
But: with other components I have heard changes in the bass/treble balance during the breakin process, and the component sometimes came out sounding different in this regard than it did in the middle of the process. It will be good if the reduced bass remains in the end, but don’t throw away those bass panels yet.
Although I have a lot of time comparing sound DS direct vs DS through the BHK (it seemed the best way to determine the BHK’s fidelity – damn good!), I’ve started playing vinyl, and the sound is superb. I have a modest vinyl setup, and while I can hear vinyl’s limitations more clearly, i’m enjoying my vinyl more than I have in many years.
I may not start buying vinyl again (that ship has sailed). But I’m looking forward to playing my existing vinyl!
And just to clarify my earlier comment about the BHK Pre bass: my previous preamp (an all tube, including rectification, piece) deviated from flat response in that it produced a huge frequency bump around 100Hz. A bump that I assumed was speaker/room related. So, adjusting to flatter response is taking me a little while, but in the end, flatter and more detailed beats not flat and bombastic every time!
Jah said
. . . my previous preamp (an all tube, including rectification, piece) deviated from flat response in that it produced a huge frequency bump around 100Hz.
Very odd, I wonder why.
It must be a delight to hear your system without this anomaly with the BHK in place.
Paul McGowan said
I've not noticed anything of this sort and would be at a loss to explain it. Please do keep us informed.
I didn't take measurements with my old pre, unfortunately. But it is an all-tube unit (c-j Premier 14LS). Even though this pre (introduced about 2000, IIRC) is much more neutral than the c-j stuff from, say, the 1980s, bass control is usually not a tube unit's strong suit. So the improvement in bass shouldn't get a big surprise.
Question for the Group, Bascom and/or Paul in regards to rolling tubes in a BHK preamp. I understand rolling tubes may or may not improve sound quality. That said, would there be any output performance difference from the preamp when switching between the original 12AU7 tubes and PCC88/7DJ8 tubes? Best, Kevin
I may have spoke on this question before. Specifically, the Tungsram PCC88/7DJ8 tube sounds a bit better than the supplied 12AU7. However, the 12AU7 is close and is currently available and that is why we ship with that tube. We tried quite a few 12AU7s to find this one. The 6922 that we supply with the BHK power amps did not sound good enough in the preamp that is why we went on the 12AU7 hunt - and why we provide the option in the preamp to use the 6922 genre of tubes if one wishes to do so.
Oh! I guess the question must have been about output performance - meaning measurements? Not any significant difference.
Can the preamp run 6H30 tubes using the 5 ma bias current setting?
I had been meaning to test 6H30s when I was researching the use of 12AU7s. I will hook up my tube testing setup and see if the 6H30 can work with the constraints of a 120V plate supply, 10K plate resistors and 4 or 5 mA plate current. Before I do that, I will look at the plate characteristic curves for the 6H30 to see if it is feasible. I will report back on that first.
Well, I just did that and for one, the Mu (amplification factor) is too low meaning that the preamp gain would be down a few dB. The operating point would be closer to cutoff with 5 mA and distortion would suffer. But hey, that is all intellectual and it may sound fine. For those with more curiosity about this, look up the characteristic curves for the 6H30. Lay a straight edge on 120V on the horizontal axis and 12 mA on the vertical axis and draw a line between these two points. That is a 10K plate load line on these curves. Now where 5 mA hits this line, that would be the operating point. And in my opinion, that is too far to the right into the non-linear region of operation.
But what does a person do when the hiss is audible from 8 feet away from the speakers? My Signature preamp started to emit a hiss about a week ago, so I changed the tubes. It made no difference - the hiss is still there. I hear it as I type and there is nothing feeding the preamp; it’s merely on.
Yes, exactly the same conditions; new tubes or the old ones, the hiss is there. Granted I have very good hearing and the noise is white, but it is obvious to me from eight feet away. Being able to hear a hiss when I put my ear to the speakers is not unreasonable to me, but this seems out of the ordinary.