Amp vs preamp question

Usually, its the bass at lower to moderate volumes that suffers driving speakers with difficult loads with amps that are not up to the task.

IF you're willing to live with that for some other aspect of a particular amps sound, then I guess you will be fine, but you may not be getting everything that your speakers are capable of delivering at lower to moderate volume.

In my case, I replaced a 360w/ch Carver amp that did not come close to doubling output with impedance with a ~100w.ch Musical Fidelity that does.

The Carver went louder and sounded fine at higher volumes, but the bass and dynamics were noticeably missing at lower volumes. The Musical Fidelity does not go as loud, and the sound is dynamic and balanced now at the volumes I more typically listen at.

09-27-08: Blindjim
...one of the two mainstays, either Mr. Conrad, or Mr. Johnson said a ratio of 10:1 is sufficient for preamp to amp matching. So if the preamp in question has an output imp of say 1000 ohms total, then the amps input imp needs to be 10,000 ohms or better…

My experience trying several tube preamps with Pass Labs solid state amps tells me the ratio rule-of-thumb is a only useful as a general guideline, and may not apply in the real world.

Recently, I tried an ARC REf 3 preamp (600 ohms) with Pass Labs XA-60.5 (30kOhms)...a ratio of 50:1. The match was not ideal. Not bad, but not ideal.

If one reads Stereopile's measurements section of their preamp reviews, one learns that output impedance changes with load. For example, the Audio Research Reference 3 has an output impedance spec of 600 ohms balanced, but in J. Atkinson's test of the preamp it's output impedance rose to 1437 ohms at 20Hz. This would indicate an early bass roll-off when used with some solid state amplifiers, and indeed when I tried the Ref3 in my system with the Pass Labs amps the bass was lacking some depth and control.

Atkinson wrote about the Reference 3:
"The output impedance was also to spec., at 635 ohms balanced and 326 ohms unbalanced in the treble and midrange, but rose to 1437 ohms and 625 ohms, respectively, at 20Hz."

So, the moral of the story is that output impedance specifications are only part of the tale. Test measurements are another part of the tale. Listening to the actual combination completes the tale.

Regarding VAC amps, it may be true that Kevin runs some of them on Thiel 2.6 speakers, but my experience with the 160wpc VAC Musicbloc monoblocks on Silverline Sonata III (5 ohm minimum impedance) was that the VAC amps produced an unbalanced sound lacking bass depth and definition, leading to an overall "tipped-up" presentation due to the lower power output into the lower impedance frequency region (bass) relative to the higher impedance frequency regions.

I absolutely agree that total WPC is not the most important criteria. However, the impedance issue is crucial, IMO.

Just curious about these impedence matching observations - BTW Tvad, I think your observations are good - how often do folks feel that impedence matching issues, which might be only marginal, if extant, are exacerbated by improper selection of long IC runs from pre-amp to amp.

For instance, using the same components and either 1, 2, or 5 mter IC's the sound doesn't differ much, perhaps a tad with the 5 meter cable, but not enuf to matter (to me). But put in an 8 meter IC of the same brand and type and the roll off is marked and not just in the bass.

Is it possible that much of which is charged to the consequences of impedence mis-matching might be laid at the foot of IC mis-matching as well? Seperaately and concurrently?

Just a thought............

I have to (mostly) agree with Tvad, here. The 10 to 1 ratio is only a guideline and there are many respected voices that disagree. Though a bit off topic, other considerations re: pre to power amp matching include output and input sensitivity, the potential for DC leakage and how it is tolerated, and single ended vs. balanced operation. And let's not forget sonic synergy.
If one reads through the archives here on Audiogon, one will find that some are satified will fairly low powered amps on their Thiels, but more often than not, those who have tried various quality amplifiers, find that the higher powered ones work best. While the majority of music played doesn't usually require gobs of power, the balance can suck up huge amounts very rapidly. With the Thiel's, I think the cost of appropriate high quality ss amplification can be a bit dear and the cost of high powered tube amplification can quickly come cost prohibitive. SS amps seem to offer a better value with Thiels(!). IMHO, ss amps sound best when they are not run into their limits... with ss amps, having some headroom is advisable.
BTW, I certainly hope that Ledenhheim doesn't have an "18 X 18" room!

Tvad
.... it never ceases to amaze me how much minutia compells some folks.

naturally there is more to preamp matching to amplifiers than simple impedance figures.... and just 'whose' figures should we use? Those claimed by the makers, or those claimed by the second party testers?

But I still hold to the "plug one in" notion. Despite Tvads notes, he admits he did just that in practice... as he's 'plugged in' several lately by my count alone. Tubed and Solid state as well.

The numbers alone, don’t tell the whole story sometimes.

Damping too, along with power reservoirs/storage account for something too. But as so much inference was being placed on impedance matching I felt compelled to throw that CJ bit in . IMO it might ought to be 100:1…. But my exp says there are exceptions to this rule.

BTW consistency doesn't seem a commonality in Silverline products from time to time... apparently either.

it's all just time well wasted, casting about this rhetorical note and system building philosophy back and forth here... the proofs in the pudding... if it were otherwise... we'd all go out and get the exact right amp the very first time as we or some of us do ijn fact 'know' by the numbers only which amp will work best.

Right?

You ask 50 audiophiles a question, you’re very likely to get 55 answers!

it's not a numbers game folks. you have to try some out for yourself. that's what most folks here did and do... so I'll just hang onto the more practical approach of just bust a move and throw something in there!

Ledinhhien

Some amps will surely surprise you, and some will (as Tvad pointed out via his own exp) be disappointing... despite their reps and numbers.

Ask the maker of the ??? item for some direction. That's a gooder place to start IMHO.

Look at what others with similar speakers are using in the virtual systems listings.

I’ve found scant little if any, perfection in this world and attempting to acquire it is a waste of time and energy…. Most quality amps will be capable of providing a good power source and no one here can say for you, just what that should be… but you… well and your wallet.

I’m sure, given the expense of the CS3.7s, you’ll acquire a commensurate amp…. But going back to the initial Q… I’ll always put more money into a preamp than into an amp… as a rule ‘cause you can’t make up for what you lost early on, downstream. You can only cover it up.