Feedback Judder - SuperLine?

LP12/cirkus/Trampoline 2/Lingo 3/Koetsu Red/1.7m T-Kable/SuperLine with HiCAP2/200/202 with HiCAP2 & NAPSC/PMC GB1i/2*10m NAC A5

I get a constant judder through my PMC speakers if put some volume through my 200/202 combo, but only when I listen to vinyl. I can only assume this some kind of feedback? When I first got my SuperLine, I used no CAP/RESI slugs at all but only had a 3m speaker cable run. Then moved system (speakers in same place) and now have a 10m speaker cable run. At first I noticed the judder at quite low levels, but found if I put the lowest CAP&RESI slugs into the SuperLine, judder went away unless I put much higher volume through the amp combo. At first I thought this the 10m cable run, but only affects vinyl. Then I thought LP12 position, so tried other locations/heights, no luck. However, I use a Quadraspire wall mounted shelf, in a cupboard (though in room corner) & used a software program to predict height of likely standing waves. Judder is present even when needle idling on the end grove (i.e. no music).

Any suggestions? Could it be my SuperLine has a fault? Before I had a Cyrus Phono X with no problems. Or just very poor room acoustics/turntable location?


What do you mean by judder ? If it’s the bass drivers flapping around due to subsonic frequencies on vinyl playback then your previous Cyrus X would probably have had a subsonic filter which reduced this ?

I also assume this is referring to woofer pumping. Subsonic filters are just a band-aide, masking the real problem, and are not a proper solution, IMO. The designer of my phonostage – Keith Herron – has also suggested not using them, stating they have adverse affect on sound quality.

I went down this road and the solution for me was to do a better job isolating my turntable. I have it on a wall shel, but also put the turntable itself on an isolation platform (isoAcoustics Delos). The other part of my specific problem is that I had a Clearaudio tonearm with magnetic bearings. Changing to one with mechanical ball-bearings finally resolved all feedback proiblems for me.

I can now play vinyl at ear-bleed volumes with lots of bass, free of any feedback that causes woofer pumping. No subsonic filter necessary.

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Had a very similar issue a couple of years ago…
No amount of isolation or caps across the speaker terminals / loading plugs on the phono stage sorted it for me …
Changed cartridge… problem gone …

I used to get woofer pumping when I had a Mantra, never with more solid decks, suspended decks seem more prone. Another possibility is an arm cartridge mismatch which seems likely. I can’t remember if the Koetsu compliance is quoted at 100 Hz or 10Hz but even at 100 the resonance is around 13Hz and even worse at 16 Hz if 10Hz and that’s before any possible hardening of the cartridge suspension with age. A hifi news test record can tell you what it is, look for the wobble, warbling can be confusing.

From what I can glean for 'tinternet, my Koetsu has Compliance: 5 x 10-6 cm/dyne at 100 hz!
So my theory of increased resistance due to cable length is not the issue, but likely turntable shelf coupling/isolation and/or arm/cartridge compliance mis-match (nice of the hi-fi retailer to advise me on that!)
So, solutions:
Step 1; borrow a decent isolation platform (wonder if said hi-fi retailer will loan me one?)
Step 2; sandwich material (sorbothane) between wall shelf and wall.
Step 3; invest in a new but compliant cartridge!

Hopefully not the latter!


Which arm is the Koetsu Red mounted on please?

His profile lists an Ekos 1

Yes Ekos mk1, silver wired by Audio Origami, Koetsu RED T.
Do you have any suggestions?

Question for Yeti;
Even if compliance resonance @ 13Hz or 16Hz is present, surely I shouldn’t be able to hear that? Rather just visually see the cones flapping? Or are the cones making the cabinet resonate at another frequency I can hear?

Thanks. I don’t have any suggestions because matching of arm and cartridge is not something that I have considered for many years and wouldn’t claim to understand. But someone here will understand it, which is why I asked.

Best, C.

Also, can anyone quote/convert a Koetsu Red T spec. stated compliance: 5 x 10-6 cm/dyne at 100 hz into nM? As that’s the units I am finding help tools use…

I’m not sure how much it matters but I’m also wary of the numbers. I recently bought the hifi news and record review test record because I have an SPU royal N lined up and was unsure of its match to my arm, even with a brass mount. The arm has a note in the box saying its effective mass is 13g with the supplied aluminium cartridge mounting plate which according to the calculations should give a resonance of an ideal 10Hz with my Proteus but with the test record the cartridge wobbles at 7Hz and the tone warbles from 16-14Hz all the way down The cartridge is a few years old now and has seen a lot of use so has it’s suspension gone soft, the the arm mass been mis quoted or am I doing it wrong. As far as I remember damping won’t change the resonance frequency, just affect the the amplitude. The proteus still sounds superb playing music.
The test record came with a warning from the dealer not to use it t set bias by the way, I tried it anyway and he was right, way too much bias results.

Sorry, I meant mN!

Well now I am confused.
I believe compliance 5 x 10-6 is 0.000006 cm/dyne which = 0.000006 mN. That is INCREDIBLY low compliance (perhaps I’ve got this wrong?). Ekos mass is rated at circa 11.5g so falls in the moderate mass cat according to Ortofon says low compliance cartridges matched well with moderate mass arm! Unless 11.5g mass is the lower end in which case I’ve in effect got low mass with low compliance as I definitely get “If a low compliance cartridge is used with a low mass tonearm, undesirable resonances can occur in the audible range…” quoted from the Orfoton page.

There’s a handy tool on Vinyl Engine for calculating resonance. It pretty much agrees with the equasion Ortofon give. Multiply the compliance at 100Hz by 1.7 to approximate that at 10Hz which the tool is designed for.

I still haven’t understood what you mean by judder and I suspect I’m not alone.

Ahem, I mean 0.000005mN!

A loud audible judder emanates from the speakers: da da da da da da!

But only when the needle is in a groove? How about if you play a 45rpm disc? Does the judder speed up or stay constant?

"Ich lieb’ dich nicht, du liebst mich nicht…"

Oops, sorry, wrong thread.