Are my speakers supposed to do this?

When I first put the Minimax preamp into my system there was a very loud hum and some static pops coming through the speakers

Amazing that the pre tested OK.
Re, testing: Rather than the speakers, shouldn't you be sending the amps for a check-up??

Ykm -

My speakers are middle of the road in terms of driving them (88db). They are basic 2 way monitors, nothing exotic. I've used different pres in my system and never had problems. I am convinced that the issue is with the pre, but I will be sending my amp for a check up just in case. What kind of speaker conditions do you think would cause the problems I'm experiencing?

Gregm -

It IS amazing that the pre tested ok. I have my doubts that this is really the case. My Belles amp will go back for a check-up soon. David Belles is out of town for a few weeks so until then ...

For those of you still following this thread my speakers checked out okay. No damage or problems.

Thanks to all for the suggestions.

Tooter, I was trying to find out any possible clue so to ask the speakers too. If the pre was "causing" your power amp motor boating, the amp is marginally stable. There are many thousand pres out there, the pres you used did not cause any problem with your power amp does not mean it was the EE MM if the power amp was marginally stable. This is not wrong because a hifi equipment designer would sometimes want his gear to deliver better sound with some trade off of slight stability or output power or heat generation or.... An engineer finds a power amp motor boating will first of all fix the power amp. Apologise if I have made some agressive assumption before knowing all the designs of your gears.

Regards,
Ykm

Ykm,

No offense taken! No need to apologize. I am just not clear on what you mean by power amp "motor boating" and "marginally stable". Can you elaborate? What part of the amp's design is deficient which would lead to it being "unstable." I'm not an engineer but Belles amps have gotten great reviews and I've used them with many speakers and pres without incident.

thanks.

Tooter, first of all gears got great reviews do not necessary mean their spec. are perfect. I understand EE MM also got many great reviews too. Motor boating is some low frequency oscillation and that you saw the woofer was pushed in and out. If the oscillation is "faster" and "louder" in your case, you would hear it like the sound of an old motor boat and that's how it came the term. A few things can cause such oscillation, incorrect amount of nfb, decoupling caps do not have enough value, bad design of the PS...I am not a real expert, but have diyed quite many amps. Audio gears are very different from other electric appliances, spec. is one thing, but sound performance is the most concerned. There many many many audio gears in the market. Every engineer does them in a different way. You cannot expect when EE made his gears and when Belle made his gears to be able to match the rest of the world. If you search around, there are many many many sayings such and such pres don't work with such and such amps etc. But when you check them, they are all fine. As soon as you connect them together, they are "loaded" and affected by each other, say DC leakage, impedance...etc. So at the end of the day, your sepckers, Belles and EE MM are all well checked okay. That's all the fun of playing with audio I look at it.

Regards,
Ykm