Amplifier current vrs watts; why is current more important?
I have the so called "easy to drive" Legacy Focus speakers because of their high 98 db efficiency. But their low impedance (subsequent 20/20s were more difficult to drive) and 4 ohm preference make them difficult to drive. Maybe it's their 3 12" woofers. Anyway, an EAR 890 amp has great difficulty in driving them, lacking in bass and dynamics and just sounding pushed. It's a Class A 70 watt design. It sounds excellent on the Legacy Signature IIIs which have 3 10" woofers and slightly easier impedance curve. I can drive the Focus speakers with a highly modified 35 watt Dynaco 70 which has an electrolytic cap the size of the chassis underneath as opposed to the original. Lots of power stored in that cap. They're plenty the Sig. IIIs. For the Focus speakers, I use a pair of 130 watt tube monoblocks, custom made, with 2 3" X 7" storage caps, huge compared to the tiny row of caps found in the EAR 890. I bet my big amps could drive most any speaker despite the limited wattage (although tube watts are 2 to 2.5 times more than SS watts generally, not including Pass amps or other high current ones). |
The " tone control" effect you speak of is due to output impedance of the amp. Yes, this also as well on top of current starvation we’re talking about. Any amp that has low damping factor, (output impedance is that high) should not be considered as well if one wants an amp that will not sound "coloured" and stays flat in frequency response. Cheers George |
Even though the OP’s title is "Amplifier current vs watts; why is current more important?" Just to take it off topic as oddio did, with his (excuse me) even grosser misinformation. To show why output impedance (damping factor) is not the only cause for "tone control" behaviour, but also "available current" is just as if not more important. Here is a typical case where "current" ability is the factor to making a flatter frequency response, more so than output impedance (damping factor) Here are two very similar (save for their current ability) amps solid state linear each 60w into 8ohms, but their output impedance (damping factor) is more that 10 x different from each other, these are frequency response measurements (black trace) into exactly the same Kantor simulated speaker loads. NB: Make sure you see what the graph graduation scale is for both. 1: This Budget Schiit is the one with lowish current , but the "best" lowest output impedance ( best highest Damping Factor) of DF=226 Output impedance=0.03ohm It’s FR is +- 2db https://www.stereophile.com/images/416Schiitfig01.jpg 2: This Pass Labs one with high current but, worse 10 x higher output impedance and worse 10 x lower damping factor especially in the bass, and yet has far better control over the same simulated speaker load. It’s FR is only +- 0.025db!!!! https://www.stereophile.com/images/1116Pint60fig01.jpg As you can see the one, 1: with the "best" lowest output impedance (highest damping factor) is the one behaving like a "tone control" more that the other!!!!!!. This is because the Schiit is current is limited into the low impedance loads of the simulated Kantor speaker load compared to the Pass labs. Now back on topic, sorry hiendmmoe Cheers George |
Wow, what a rabbit hole you guys took this poor guy. His question was a simple one, one I try to answer from time to time, but within a couple of responses you guys were into slew rate, and it went down from there, with different people flexing their knowledge muscles. And I know you were trying but like a lot of forum questions it takes very little to take your eye off the ball. I thank you, for you enhanced my general knowledge but I'm not sure anyone answered his question. |
