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.


Not 100% clear, on the EXACT problem, specifically?

Perhaps some fellow owners will share their experience,

in this area.

Bottom Line: Something is NOT happy, in the loop.

If I had to guess, I would point to the pre-amp.

Power should not be an issue, the pre-amp is failing

to transfer the power cleanly to the speakers.

Elsewhere, there are several other forums about this

awesome pre-amp.

Give the fellow "Guru's" a chance to respond.

Be assured, help is on the way.

I Love My Music!
Maybe this can help.
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. ( ( Reproducing low freq rumble DOES use lots of power, and thus can easily cause your system to go into clipping, at any gain stage.

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
You're a little unclear, but it sounds like your turntable is not sufficiently isolated.
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.
It sounds like you have 2 problems...

1- not enough gain just for the system with that cartridge if you crank and don't get the volumes you want, but ....

2- You need to read this thread below and it will solve the woofers pumping basically guaranteed with no sonic effect, but again will not solve problem #1, your other preamp has a subsonic filter most likely, and the other does not, its basically just capacitors in a certain value directly connected at the phono input RCA's in most preamps with built in active phono statges that gets rid of the surface noise off an LP pumping the woofers, take it from experience.

Not sure but possibly the good outboard subsonic filters can add a tad of gain due to most of them are active designs, being it will need to be plugged into the wall I believe. If your really concerned I would call KAB acoustics U.S.A and see if they will let you try one, might be a restocking fee however. Its possible Mr. Doshi since being a custom preamp most likely hand built can put the cutoff Capacitors in the preamp for you on the phono inputs. But the value would have to be determined in order to get the right cutoff... Fact is most of this noise is likely down around 10 to 3 hz.. Were taking its the Wind blowing effect with the groove going thru your cart puffing away, the preamp is just amplifying it, no sonic benefit, nor is it a benefit to your woofers working out on a daily basis for nothing! And of course this is an in-efficient power loss too, so might up your dynamics in the real music eliminating it.

By the way your speakers obviously don't play that low, but this energy goes somewhere and its in a pulse effect causing your speakers to act this way, I have first hand experience and solution on this.See thread
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


Have you tried repositioning your turntable? You might have it placed in a room node peak.
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
Hi Audiotomb, What did Nick have to say about this?
Perhaps you are just listening too loud? How loud are you listening?
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.
If the amp or preamp were motorboating, as in the case of a power supply problem, it would not be restricting to phono playback.
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
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.