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In Reply to: RE: Enough Current? posted by Lt Einhorn on January 18, 2015 at 07:21:30
Perhaps I should post this in the amplifier section of this forum?
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I dont see any issues of instabilty from that stereophile test, even thou i find the tone burst test to be invalid in testing an amplfier drive ability into low-Z Loads. As to your ML , low-z is at high frequency , so drive into that load will not be an issue , instability into a capacitive load would be, again i dont see any instabilty issues ...Never tried that model on a CLS, i know The BAT VK500, did'nt like it so that one i can tell you to avoid ..i know its more money , but the magtechs are pretty good on ESL's
Regards ..
Edits: 01/18/15
I've never actually used the Rotel, but I distinctly remember checking out that model to power my Tympani IVa which also present a difficult load. Whatever it was I was reading at the time had me believing it would work for me. I ended up trying an Emotiva XPA2 that couldn't handle the speakers, and then a Sunfire Signature 600 that I am still using.
Speakers that present a difficult load to an amplifier have dips in the impedance due to reactance. Magnepan drivers are almost pure resistance with very flat impedance across the audio spectrum. Cone speakers have inductance which causes the impedance to rise with frequency and makes design of a crossover more difficult (hence a Zobel to flatten the response). Electrostatics OTOH have large capacitance and this causes a drop in impedance at higher frequencies making these difficult loads for amplifiers. Both component introduce phase shifts as well.
Magnepan's have gotten a bad rap as being hard to drive and this has been translated to "a difficult load". As pictureguy points out, they need a lot of power and many amplifiers, especially receivers are not up to the task. This is due to increased expense involved with a sturdy power supply. I am surprised however that your Emotiva was not able to drive the Tympani's but that Sunfire is a beast!
Neo,
It's a shame about the XPA2. As I've said in many a thread it sounds pretty good (aside from some grain on ribbons). But in my haste I neglected to try it with speakers other than my Tympani, so until someone else tries it I will not know if I simply got a defective unit. But it was actually the main guy at Emotiva who told me that the Tympani had severe impedance dips that the XPA2 couldn't handle, or at least that seemed to be what he was implying. Perhaps he was confusing it with an electrostat. Either way, I wanted the thing to work so much I actually did call Emotiva to about it for about an hour, at which point he agreed to take it back and refund me, less return shipping. Great customer service, I might add.
And yes, the Sunfire sure is a beast. I haven't yet met a speaker it couldn't drive. Not everyone digs the Carver sound, but I sure do.
Tympani? Difficult load? Why? It IS low sensitivity to be sure, but very low stored energy, too.
I'd be concerned if the Rotel has SAT UNUSED for several years.
Too much is never enough
I'm not worried. People pay big bucks for unopened vintage hifi. The materials they use now, stuff lasts a long time, used or unused. I still have my dad's vintage all tube Sherwood tuner. All original tubes, caps, everything. The thing works and sounds good.
UNUSED PS Caps tend to go south in a matter of years. They'll ZAP when hit with full line voltage and power. It is simply physics and chemistry.
Most techs recommend bringing amps which have SAT for years up on a variac. Those kinds of caps have NOT changed in Decades.
Pass is on record as saying how long PS caps last in regular use. 20 or 30 years, IIRC.
Just sitting? No Way.
Too much is never enough
I understand what your saying. However I don't think sitting for 5 to 10 years is going to be an issue for equipment that is of this quality. I have a laptop that has Windows 95 on it. The thing sat unused for over 10yrs and it runs fine. The laptop is 25yrs old. Its full of old crappy electrolytic caps.
Not saying this couldn't d be a problem but its highly unlikely IMO. Thankfully the amp is running great. Its dead silent. Only a short very quiet humm on initial power up as the caps charge up.
ALL those aluminum paste electrolytics are the SAME regardless of whatever.
They are up against some real physical limits and work best by being worked OFTEN.
Sitting is the WORST thing in the world for those big PS caps.
Don't believe me. Most techs would even recommend a piece of gear with such caps that has sat for YEARS be first energized with a variac so the caps have a chance to reform before getting hit with full line voltage.
Check out this link for info from prime manufacturers of Aluminum PS Caps.
Too much is never enough
You linked me to a "page that can't be found" and a .pdf that won't open LOL!
Thank you for your concern, but the amp works great. Rotel told me not to worry about the caps. Im not worried.
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