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
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Showing 4 responses by audiotomb

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
audiotomb's avatar
audiotomb OP
1,112 posts
 
thanks guys

seems the record with the most trouble was a slightly warped one. I went back and lowered the volume a little and haven't had the pumping effect. It's mostly very demanding passages - doesn't get overloaded on jazz like it does on some rock records

I have a ZYX Artisian outboard phono pre and will try that in one of the line imputs on the doshi - perhaps there is a roll off in the low freq end of the phono stage

it doesn't do this with cds

I'll touch base with Nic Doshi and get his comments on gain and low end frequency

I believe I do have that test record

thanks

Tom
audiotomb's avatar
audiotomb OP
1,112 posts
 
woofers only seem to be over-extending on fairly loud playback or warped records

could be a room mode 15' depth - speakers 3
from back wall
audiotomb's avatar
audiotomb OP
1,112 posts
 
thanks for all the insight
my old phono pre (ZYX artisian) linestage (dodd and Audio Research LS5 linestages)

I've been very observant of when the pumping
very low modulation warpage - seems to be thinner early 80's japanese pressings and more obvious warped records

when at higher volumes even the quieter passages have speaker excursion. It's more pronounced on the outer record and I use my heavy Galibier anvil to lower the effect

real shame some of this very slight warpage may have been related to post Katrina with no power for three weeks in the mid 90s heat. One friend lost 6,000 records - 10ft of water - washed away and stuck in walls, so I feel blessed

I may plug my Artesian into a line stage on the Doshi to compare. The Doshi phone/pre goes a lot lower than my previous two.

I have a friend with a similar problem but woofer excursion all the time, I believe he has a scout, can''t remember the arm and cartridge. HIs may be isolation (wood floor and furniture) or the subsonic element - He has the Audio Research SP17 and VS60 amp.
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