Current amp vs Voltage amp

05-14-13: Hifigeek1
It might interest you to know that the Quad 405 current dumping solid state amp which was designed for use with the Quad 57 and later the Quad 63 actually damaged the speaker because is lacked a limiter. The amp was capable of producing to much output for either speaker. A limiter add on circuit board was designed for the 405-2 to stop the damage. Ten different iterations of clamp circuit boards were designed for the Quad 63 speaker so that when the clamp engaged, it didn't blow up the amp powering it. Quad had it right with their original QuadII amps which were tube. Quads prefer voltage amps not current amps. The Quad 57 wanted to see no more than 40 Vp-p or about 25Wrms across 8 ohms.

fwiw

I used the 405-2 with the limiter with my WPK Quad 57’s. It sounded ok. The 405 was bettered by the Music Reference RM10 which was also designed for the Quad 57’s and no fear of damaging them. Sold the 405.

Cheers.

Powered speakers can be sold with separate power units chosen specifically for the task at hand, the way some speakers are sold with separate cross-overs, or have upgradeable power modules. I typically (always?) prefer systems that have speakers with low impedances rather than higher impedances. Historically speakers with lower impedances are more likely to be able to produce wave form fidelity than speakers with higher impedances. There are many good reasons for speakers to have a low impedances and the market place has proven this for a long time now.

Unsound,
I believe the marketplace is a strong case for what's convenient and expedient but not for superior sound quality as the objective. I realize you and I are at different ends of the spectrum, but the introduction of low impedance speakers wasn't a direction chosen for improved music reproduction .These sre probably the easier design vs high impedance speakers Al and Ralph do make a more compelling argument in my opinion. I do appreciate your comments and contributions to the dialog here.Variety is the spice of life afterall.
Regards,

I suppose everybody thinks their way is best, when in fact there always turns out to be many ways to skin the cat, including the means to superior sound quality, though personal preferences always determines what happens in the end.

Economics, convenience and ease of use are real factors for most along with superior sound. So that largely determines what is best.

Each paradigm has advantages and drawbacks. Which matters most will determine the winners.

Regarding sound quality alone, I would guess power paradigm has advantage of lower risk of bad sound up front for many, while results with voltage will be more variable case by case. However voltage scales to larger applications more cost effectively these days I would think.

Again, the game changer on the scene of late are high performance, high efficiency switching amps, that take a lot of cost and risk out of the equation for voltage amp applications. In lieu of these, I personally would be more inclined to go the current/tube amp path I think. I had strongly considered it during last major upgrade phase but decided to give Class D amps a try first, and am glad I did.

Historically speakers with lower impedances are more likely to be able to produce wave form fidelity than speakers with higher impedances.

[facepalm]I can't let that one pass[/facepalm]. Its well known for decades that the Quad ESLs have had very low distortion (re.: 'wave form fidelity'[sic]), some of the lowest out there. Yet the ESL57 and 63s both have a fairly high impedance.

In fact impedance has nothing whatsoever to do with waveform fidelity in a loudspeaker. That is entirely a matter of design.

There are many good reasons for speakers to have a low impedances and the market place has proven this for a long time now.

The 'good reasons' are sound *pressure*, not sound *quality*. I recommend you reread my previous comments. Its one thing if I say it- I own a small company that makes tube amps. But its another thing entirely when transistor amp manufacturers say that, and especially when that is re-enforced by the distortion measurements. We are talking about distortion that is audible too. Go ask Paul Speltz to show you that letter from Steve McCormick.