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Are my speakers supposed to do this?

Hi all. Thanks for reading this thread. I just put a new preamp (Eastern Electric Minimax) into my system and am noticing some weirdness in my speakers. When everything is on but no music is playing I noticed that both the left and right drivers of my monitors (Tyler Acoustic taylos) are moving forward and backwards very slowly but at a very steady rhythm. Takes about a second for them to move forward and then another second to move back. They repeat this cycle until I turn the amp off. This doesn't seem normal to me. I never noticed this with my previous pre. When I play music through the system it seems okay, no obvious distortion although I do notice my drivers moving (from my listening position 7 feet away) in a similar way - slow in and out although it doesn't seem as cyclical.

When I first put the Minimax preamp into my system there was a very loud hum and some static pops coming through the speakers. I lifted the ground on the pre with a cheater plug and the hum & static went away.

Did I damage my speakers? I want to try and trouble shoot but am afraid that damage already may have been done and I don't want to make it worse.

Thanks.
tooter
smotyka
62 posts
 
Tooter,

I had a similair problem after picking up a defective BAT P5. I believe the problem turned out that it was generating a high frequency DC signal. When it was connected to my tube amp, it started over loading my power tubes. I then switched to a solid state amp and I noticed that my midrange drivers started pushing way in and out. The bass drivers were stable.

BAT put a filter in the circuit and that problem was solved.

I was told that it could be the tubes but in my case it wasn't. Hope you can either get some other tubes or find someone that can repair the preamp. I'm assuming that you tried disconnecting any inputs to the preamp. You made need to get the schematic.

Also, it didn't damage my speakers although I was concerned too.

Steve
tooter OP
85 posts
 
Hi Steve. Thanks for the reply. I haven't tried disconnecting inputs to the pre. What would this accomplish? Is this to eliminate my CD player as the possible source of the DC?
smotyka
62 posts
 
Yes.

Just to make sure & prove that the pre amp is the culprit. You never know how a combination of equipment can cause a problem.

Kr4 made an excellent point about both channels and that the problem could very well be DC leakage. That was the problem I had.
kr4's avatar
kr4
3,688 posts
 
What is high frequency DC, anyway?
zoya
120 posts
 
I think the problem is with the tubes, but not because the tube is going bad, but because it's a low quality brand.
When I got my tube amp, I've experienced similar problem, but I could also hear the modulation that appeared at approx 1 cicle per second. I replaced a pair of GE 6k7 tubes with a pair of RCA 6k7g and modulation stoped.
Try a different brand for a pair of 12au7.
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