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Mo-fi Ultradeck owners - popping noise from speaker upon power off

Guys, I got a mo-if ultradeck with mastertracker cartridge and I have a problem that I cannot figure out. When I turn the power switch off, I get a loud pop through my speakers. If turn the volume down or switch to another channel, then obviously I do not hear it.

I got the player replaced with another new unit and the same thing. I have tried everything - that I can physically do, replace power cord, hook up power cord to a different outlet, using different phono preamp, etc.

Does anyone else experience this? My other Project Classic SB TT does not have this at all in the same system.

I have searched the whole internet and found one post on Stevehoffman forum about experiencing the same and that person did all sorts of experimentation to no avail.

https://forums.stevehoffman.tv/threads/popping-on-power-down.1000508/

A $2500 player should NOT have issues like this. Period.
dandaroy
yogiboy's avatar
yogiboy
5,811 posts
 
@dandaroy
I had the same problem with my VPI HW-19. The capacitor between the switch and the motor was the culprit. The Mo-Fi deck that you have uses the same Hurst motor as the VPI. That loud pop could damage your tweeters!
This is the motor!
http://hurst-motors.com/documents/PA_PB_Synch_DD.pdf
oldhvymec
5,101 posts
 
The key is the little shock, when you touch the tonearm... the black wire mentioned was NEVER figured out... Where is it grounded.

TT pops can drive you nuts.. I thought it took a resistor to dump a cap to remove noise, when shutting down... Either the resistor is bad OR it doesn't have one hooked up, IN THE RIGHT path when shutting the switch OFF, It may be there in the on position, but gone when you flip the switch, to the OFF position. 

You follow my reasoning?It's there but need a jumper or maybe moved to a different common location, to dump the cap that's discharging.. when you flip the switch..

I don't turn switches off when I'm in concert, It just doesn't happen...
VERY bad practice. 30 min motor warmup, and the TT may not get turned off for a week at a time..

My units have platter breaks and litteral gear shifters, to engage and disengage, the platter or the motor.. 

Volume is always turned down...with an LP flip. ALWAYS.. Dual TT roll one down, and roll one up at the same time,  that is DJ 101. Blow the speaker up doing that.. Drop an arm with the volume up.. LOL BAMB... Folks will want their money back...

Regards
elliottbnewcombjr
5,733 posts
 
this unit is for sequentially timed turn on/off of amps/components, with 30 second intervals. 

adcom ace-515

https://www.usahifi.com/sites/default/files/product/494/manuals/Adcom%20ACE-515%20AC%20Enchancer%20Manual.pdf

it may solve your problem, avoid need to turn volume down.

I have one I am not using, I could put it up for sale here if you want, for what I paid, $60. or you can find them on eBay, ... they seem to be asking more these days

if it doesn't solve your problem, you can send it back, full refund, you pay return shipping.
builder3
771 posts
 
Never noticed that with mine. Then again I always turn the volume down to a low level at the end of the record. Love the TT, my only complaint is the cheesy plastic bumpers that continually fall off the dustcover.
dandaroy's avatar
dandaroy OP
21 posts
 
Unfortunately, I have to let go of this TT. I believe I have another defect in my turntable for which I will not be able to keep the TT. When the platter rotates, the center spindle sways or wobbles from side to side as it turns suggesting that there is some eccentricity. I took the platter off and reseated it several times with no luck. The platter seems to spin without any wobble. It is shocking to me that a $2500 table passed this quality inspection at Mo-Fi. I do not want to spend $2500 and have to worry about a warped table what it might be doing to sound quality.

https://www.youtube.com/watch?v=cve86r1Jkyk
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