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Sub Sonic Filter
Sub Sonic Filter
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Old 18th July 2017, 06:25 AM   #1
gigigirl is offline gigigirl
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Default Sub Sonic Filter

Hi guys was going to buy this, got some good reviews,

DB Sub sonic
Filtershttp://store.acousticsounds.com/includes/image_browser.cfm?title_id=60042

at US$20 / pair it seemed worth while to try to stop a bit of cone flapping I have when playing vinyl. However they will not ship any order below US$50 (talk about old school)

So I thought I would ask here to see if anyone has any idea how to make one? Cheers
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Old 18th July 2017, 08:25 AM   #2
Zero D is offline Zero D  United Kingdom
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Hi, i see that one is a passive device.

If that's what you want i can design one for you, or an active type, but unless you are used to building electronic circuits, it might not be so easy for you.

The passive only consists of a few components & should cost about $10 including a small case to house them in. Trying to fit the components inside the RCA/Phono's would be a bit tricky.

Let me know where inbetween what & what you intend to insert the filter. Fitting it from the cartridge outputs would work, but not as effective as other methods.

Does your preamp etc you using to connect the cart to have a tape loop ? Exact model # required to design it properly.
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Old 18th July 2017, 08:28 AM   #3
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Formulae ;
3dB point is F= 1/2pi R C
Don't forget to factor in the load unless above 5times the value of R. For loudspeaker use, R is the load. For line level include R with the load.

A bit of theory for speaker frequencies. Crossovers: Basics
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Old 18th July 2017, 10:30 PM   #4
PRR is offline PRR  United States
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Quote:
Originally Posted by gigigirl View Post
DB Sub sonic
Filtershttp://store.acousticsounds.com/includes/image_browser.cfm?title_id=60042
Link could be
DB Systems-DB Systems Subsonic Filter-Turntable Accessories|Acoustic Sounds

" -3dB @ 25 Hz for input impedance of 47 Kohms
" 6 dB per octave"

These specs say it is a 0.135uFd capacitor. (Use 0.15uFd.)

I have seen some phono preamps make huge subsonic rumble when such a small cap is used to couple-in.

Poking a finger in the Web, I see that Small Bear will sell you two for a dollar (plus $5.25 shipping).
Panasonic ECQ-B/ECQ-V .15 mf - .39 mf (50V) - Individual - Small Bear Electronics
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Old 19th July 2017, 12:42 AM   #5
rayma is online now rayma  United States
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Quote:
Originally Posted by gigigirl View Post
it seemed worth while to try to stop a bit of cone flapping I have when playing vinyl.
What's your cartridge/arm/turntable and speakers? It's best to eliminate this problem
at the source if possible.
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Old 19th July 2017, 05:00 AM   #6
Shhh its me is offline Shhh its me
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Quote:
Originally Posted by PRR View Post
Link could be
DB Systems-DB Systems Subsonic Filter-Turntable Accessories|Acoustic Sounds

" -3dB @ 25 Hz for input impedance of 47 Kohms
" 6 dB per octave"

These specs say it is a 0.135uFd capacitor. (Use 0.15uFd.)

I have seen some phono preamps make huge subsonic rumble when such a small cap is used to couple-in.
What do you make of the reviews of the device on that link?

I get the impression the noise, audible rumble, is just that 'audible' and not strictly speaking 'sub sonic'.
If this is the case, then addressing the cause rather than affect will always be better. Yes?

Is it a case of true 'sub sonic' frequency transposed with vibration from turntable motors and disc signal, being in audible range?

My understanding of sub sonic signals loading Amps unnecessarily is to do with wind effects on microphones at outdoor performances. The sort of thing that a wide bandwidth Amp could be overloaded with when true audible signal like vocals or acoustic instruments are combined.
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Old 19th July 2017, 05:32 AM   #7
gigigirl is offline gigigirl
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Default Sub sonic filter

Hi guys, thanks for the input.
My equip is a Goldring Eroica H, a Temmad Tintaniyn 12" arm on a Lenco 75 into a clone 834.
The Lenco is where the noise is coming from and later in the year I intend to make new 2 tier plinth to isolate the motor noise.
These feeds a DCB1 pre which goes into a Snell electronic cross-over splitting the base from treble a 80hz. I would like to put the filter either before the Snell or after it put before it goes into my Shue Class D base amp.
I have a little ability with making circuits, and spending $10 yo $20 is no problem for the circuit, but $50 plus postage about $15 to NZ is to much for a temp fix. Cheers
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Old 19th July 2017, 08:52 AM   #8
Shhh its me is offline Shhh its me
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Will -3dB be effective?

From the 'Similar Threads' links below I see a very interesting thread. interesting to me because my principal interest in 'records' is towards the inherently damaged 78rpm format.

The ultimate rumble filter - far more effective than just a high pass filter!

Really worth a read of this. Maybe a better approach to not only 'rumble'.

I question the effectiveness of -3dB filtering, due to the levels considered in this thread.
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Old 19th July 2017, 09:29 AM   #9
Shhh its me is offline Shhh its me
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Quote:
Originally Posted by gigigirl View Post
I have a little ability with making circuits, and spending $10 yo $20 is no problem for the circuit, but $50 plus postage about $15 to NZ is to much for a temp fix. Cheers
It does seem to me these are expensive.... for whats involved, parts and time rigging them up.

What have we got there....
2x bipolar Caps, cheap,
2 male RCA + 2 female RCA, common as muck,
Scraps of braid and mylar shielding for Ground,
And a bit of lousy heat shrink.

Perhaps a bit of veroboard if you want to have both caps mounted on a common board with 4 moulded RCA leads soldered up, instead of 2 somewhat long rigid inline device hanging off the back of the Amp. [assuming the main amp has RIAA input].

I suggest save your NZ $$ and DIY.
Cheap and easy for a short term fix [re. address the cause].

I'm not 100% familiar with isolation mounting of the motor on a Lenco.
These use a horizontally mounted motor wheel with shaft mounted rubberised wheel acting on underface of platter don't they?
Platter speed variation being achieved by variation of wheel contact distance from centre of platter?
Tone arm mounted on sprung chassis as well as all that above?

I have similar rumble issues with an ELAC idler..... Replacement of the soft rubber motor mount is very much needed. A decent ancillary tone arm, isolated mounted, would help a lot.
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Old 19th July 2017, 09:34 AM   #10
AndrewT is offline AndrewT  Scotland
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3dB just defines the turn over frequency.

It's what happens below the turn over frequency that matters.

One could go a s single pole roll off giving 20dB of slope per decade.
Or go for multiple poles, allowing much steeper slopes.
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