2. amps-preamps
  3. 1273520086

amp clipping or low freq causing pumping speakers

My cd source plays back fine at loud volumes with modest amplfication. My analog MC setup needs much more volume and until I switched out my premap from a Dodd battery powered to my present highly resolving
Doshi Alaap I had little to no pumping / displacement in my bass drivers (Salk HT3's).

Now they noticably vibrate in and out with some breakup distortion. Not as much with jazz but more so with dense rock music. Unfortunately quieter passages are too far in the background when played requiring higher volumes (perhaps I need more preamp gain). CD's with their higher compression sound fabulous on the Doshi and with less volume required

I have seen this once before when at an audiophile meeting a friend brought over an Infinity pre that went down to subsonic frequencies and my speakers were vibrating

my dilema is I need to turn my turntable up louder than my cds(which sound great and don't clip).

Could it be the added dynamic range and more low end of analog sending the speaker into viration mode

Or is the amp clipping not being able to reproduce the load sent to it?

I have a Moscode 401 HR amp, I have a higher powered BAT VK600 with a friend 1200 miles away.

thanks

Tom
128x128audiotomb
imhififan's avatar
imhififan
2,102 posts
 
Maybe this can help.
rodman99999
5,976 posts
 
The problems addressed by the site in the previous post are probably the issue, but- a filter such as that is a crutch that will cripple a high-end system(transparency/ambience/harmonics/timbre loss). Much better to actually address things like cartridge/tonearm mismatch(compliance and effective mass), platter rumble, acoustic feedback, possibly warped discs, etc. (http://www.gcaudio.com/resources/howtos/tonearmcartridge.html) (http://www.vinylengine.com/cartridge_database.php) Reproducing low freq rumble DOES use lots of power, and thus can easily cause your system to go into clipping, at any gain stage.
audiotomb's avatar
audiotomb OP
1,112 posts
 

thanks for the insight

that's along the two ends of the spectrum I was looking at

The cartridge/table is a very good synergy
Gavia Galibrier / Tripaner / ZYX Universe
many Galibier owners have this combo and it is stellar
and has always been great synergy with my more 'lower end rolled off" ARC LS5 and Dodd preamp

The Doshi plays fabulously at modest to mid high volumes and just glorious on cds. It is a step attenuator so it takes a while for the volume to ramp up on analog

I like to hear subtle things and therefore play analog at louder volumes from time to time getting the speaker cone movement

my previous preamp didn't go that low frequency wise
and a second preamp with very low frequency did the same thing

so yes sounds like subsonic problems

rumble or clipping
could be some of both

not sure I want to filter it - and if the amp which only balks at higher volumes is clipping, I can try more power with a different amp

unfortunately my second amp a Bat vk600se is at a friends 1200 miles away. Perhaps Richard Gray, our local superman electronics guy in New Orleans can lend me something for a while
onhwy61's avatar
onhwy61
5,133 posts
 
You're a little unclear, but it sounds like your turntable is not sufficiently isolated.
bombaywalla's avatar
bombaywalla
1,958 posts
 
Your TT looks to be pretty well isolated using the SRA platform. You rack looks OK too.
All-the-same, like Rodman99999, I believe that you have acoustic feedback when you play LPs. It could very well be the speaker design. It could also be a subsonic resonance w/ your tonearm.
If you can get your hands on the HiFi News & Record test LP you might be able to test @ what freq your tonearm-cartridge is resonant. Confirm that it is indeed resonant @ the freq you expect it to be.
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