Justin & Jerry's Hifi Blog

[jandl100]

Did he like it?
I just watched a few minutes of the start - no audio! That was enough. So I've no idea what he thought of the Q5 Pro.


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Anyway, I'd kind of set myself an expectation of re-inserting the 300wpc Apart power amp for Justin's planned visit chez-moi. That visit didn't happen cos I've come down with an 'orrible cold caught from my 9yo great nephew, curse him.
But that still set up an expectation for an amp change.

So I thought I'd try a spot of bi-amping - the Q5 Pro on the mid/top and the Apart on the bass.
Sounds like a good plan, but it didn't work out at all well. It sounded very strange indeed.

Going back to sole use of the Apart, I realised that the problem was a different tonal presentation of the two amps that just didn't gel together.
The Q5 Pro has a much 'whiter' tonality - which helps explain the amp's very noticeable openness and clarity, I think.
The Apart is richer, fuller, a bit slower-seeming.
And listening to the bass section of the MBLs on its own, the x-over is a slow one and it goes way up into the lower mids. So the tonality of the mids with the 2 quite different sounding amps substantially overlapping probably explains the sonic weirdness that I heard.

So the current setup is with the Apart amp on its own. It does sound yummy.

[Yomanze]

Horizontal bi amping, a poor solution for a non existent problem. [emoji14]

Sent from my SM-G920F using Tapatalk

[jandl100]

Horizontal bi amping, a poor solution for a non existent problem. [emoji14]

Really?

300wpc on the bass, 25wpc on the mids / treble -- instead of 25wpc covering the lot.

Would be expected to make some difference I would have thought?

[Yomanze]

Really?

300wpc on the bass, 25wpc on the mids / treble -- instead of 25wpc covering the lot.

Would be expected to make some difference I would have thought?

Like what you have found, I think that (passive) bi-amping results in a less cohesive sound, and comes across more "split up".

[Reffc]

Did he like it?
I just watched a few minutes of the start - no audio! That was enough. So I've no idea what he thought of the Q5 Pro.


___


Anyway, I'd kind of set myself an expectation of re-inserting the 300wpc Apart power amp for Justin's planned visit chez-moi. That visit didn't happen cos I've come down with an 'orrible cold caught from my 9yo great nephew, curse him.
But that still set up an expectation for an amp change.

So I thought I'd try a spot of bi-amping - the Q5 Pro on the mid/top and the Apart on the bass.
Sounds like a good plan, but it didn't work out at all well. It sounded very strange indeed.

Going back to sole use of the Apart, I realised that the problem was a different tonal presentation of the two amps that just didn't gel together.
The Q5 Pro has a much 'whiter' tonality - which helps explain the amp's very noticeable openness and clarity, I think.
The Apart is richer, fuller, a bit slower-seeming.
And listening to the bass section of the MBLs on its own, the x-over is a slow one and it goes way up into the lower mids. So the tonality of the mids with the 2 quite different sounding amps substantially overlapping probably explains the sonic weirdness that I heard.

So the current setup is with the Apart amp on its own. It does sound yummy.

Interesting observations Jerry but in reality, there may well be other reasons attributable to what you are hearing with this bi-amp solution. The first point of note is that 25wpc (if indeed it actually does produce this) might or might not be sufficient as those lower mids cross over at something like 170Hz but are drawing appreciable current an octave below that and those speakers draw a sizeable current demand up to above 1KHz, above which impedance falls off to something like 4 ohms. Rated as 83dB/1w/1m they are not especially sensitive hence I would have expected more power to be needed for any appreciable dynamic swings. Of course, you can, and probably have driven them with lowish powered valve amps but the way that they normally run into clipping tends to be more benign (not always, but more usually even order distortion). So it is possible that you could drive the little amp quite hard, even into clipping distortion. That's one possibility. The second point is that you are, in effect, slightly altering the crossover by losing some of the out of band damping that a single amp driving a crossover with all the tri-wire links in place would normally see. This does slightly increase measurable distortion unlike a true active solution driven by a single amplifier with the crossover within the preamp section.

Now it would be more interesting to hook up something like a beefier valve amp for the mids and HF which might be more tolerant of the impedance drop and see how that compares. Unless an amp is poorly designed and operates with a degree of audible distortion within its stated operating band, I would not expect to hear much, if any differences between them if operating below clipping levels (ie your current configuration as described) providing that they were both level matched. If you aren't able to level match them, then that on its own might account for the differences you hear. The input sensitivity and gain structures of the output sections of both amps will differ, one might reasonably assume, so driving each off the same preamp is still no guarantee of level matching them. Personally, with speakers of that calibre and at that cost, I wouldn't be messing about driving them with lower powered amps given the choice. Best I ever heard them I reckon was with the Parasound Halo up front

[jandl100]

Hmm - well, the problem with that analysis may be that I am much happier with the (alleged) 25wpc digital amp on its own than I am with the aforementioned bi-amp pairing with 300wpc taking care of the bass.

And, crazy dude that I am , I am actually quite happy with a 10wpc amp driving my speakers! - be it a Mini-T switching amp or the SET Jazz valve amp - both of which work very well, imo.

It's the bi-amping thing that went skewiff, not an under-powered mid/top amp.
And I like all the amps on their own - just not in combination!

Maybe it's the x-over damping/distortion thing you mention, Paul - but it was a very obvious and unpleasant effect so I doubt the issues you raise would be so catastrophic.

[User211]

I agree with Paul in the sense that I think your speakers need power, Jerry.

Amp mixing does lead to some really weird sounds sometimes, so I am not surprised, especially with such radically different amps. Paul is right.

Also, the Champ is great. I really like it and for what we paid it is out and out amazing VFM. But the MBLs could do with better.

Halo was very good, KSA 250a the best I've heard with yours IMHO (though defo the other way round on my speakers).

Just my thoughts.

[User211]

Oooops forgot the Graaf. That was my fave actually in valvesville. Only 50 Watts but that did things I really liked with the MBls. Loved it.

I regard that as sort of an equiv to my 211s. Ultimately lacking in power, but WTF who cares it works so well at anything but silly volumes.

[User211]

EDIT: Double post in weird non-responsive forum s/w blues.

[jandl100]

Hmm. yeah, while I certainly enjoyed the Graaf / MBL pairing I wasn't as keen on it as you, Justin.

Did you ever hear the 70wpc Ming Da KT90 amp (that Marco heard)? - I think that one would have ended up as your favourite valve / MBL pairing if you had. A very ballsy / controlled sound.
Ultimately that was a bit stark for me, and the NAD S300 stayed and it left.

You might be surprised at how well the Apart Champ amp works here - I suspect that with an easier load than your Aps it shines in ways that it doesn't quite manage in your system. It really does sound rather fine. Just as ballsy and detailed as the Krell 250a (you should hear it on Dream Theater) but warmer, without the Krell's upfront sound. Your choice would I think still be the Krell, but the Apart is more to my taste.