2. amps-preamps
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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
acoustat6
357 posts
 
Hi Audiotomb, What did Nick have to say about this?
Perhaps you are just listening too loud? How loud are you listening?
Bob
atmasphere's avatar
atmasphere
11,594 posts
 
The Triplanar and the ZYX is a good match- I use that in my own system and there are no pumping effects.

One thing that can effect this is low frequency bypass in the preamp or amp. An extreme example is when the filter caps are failing in the power supply, and the amp or preamp 'motorboats', which is a woofer-pumping phenomena. But if the amp or preamp is insufficiently bypassed in the power supply, this can still be a problem at higher volumes.

If this is what is going on, it points to the amp or line stage, not the MC preamp.

Improper tone arm setup can cause this too. The Triplanar is equipped with multiple arm weights, so you can choose a combination that allows the mass to be closer to the arm pivot or further away, which allows you to tune the effective mass of the arm a bit. If the effective mass is too high, woofer pumping can be a problem. The solution is to choose a heavier set of weights that can be used closer in to the arm pivot. I would not track the ZYX less than about 1.8 grams.
rodman99999
5,988 posts
 
If the amp or preamp were motorboating, as in the case of a power supply problem, it would not be restricting to phono playback.
casouza
239 posts
 
This is a very common issue with phono playback. I have seen it countless times at dealers, friend's homes and Hi-End shows.
There is nothing wrong with your amp, it is just amplifying subsonics from your phono rig.
You need a phono stage with a steep bass filter below 20 Hz. I suggest that you call the phono stage manufacturer.
Also, optimize the arm/cartridge moving mass as recommended by Atmasphere.
I have searched your arm and cartridge in the Cartridge Database, they seem to be compatible, the resonance falls in the good "zone", around 10 Hz.
A heavy peripheral record clamp (AKA platter ring) can also help reduce LP warp subsonics.
good luck
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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