Analogue Turntables

Question 1

What are the two types of feedback that can be encountered when using analogue turntables and how are they transmitted?

Answer 1

Structure-bourne feedback are vibrations ocurring in the table (caused by the low frequencies coming out of loud speakers) and sound like a low rumble at around 100hz; airborne feedback is caused by vibrations transmitted through the air or frequency buildup in overly reflective/not acoustically-treated spaces

Question 2

How can low-frequency feedback be reduced/eliminated with a physical solution ?

Answer 2

Concrete blocks can be placed on top of frontennis balls cut in half to creat a base for the turntables that will stop most vibrations

Question 3

How can airborne feedback be eliminated?

Answer 3

By using a graphic EQ’s notch filter to find the offending frequencies and remove them using a narrow-Q cut - the sound engineer should be able to do this.

Question 4

What is the most important first step to take to avoid noise issues when using an analogue turntable?

Answer 4

Attaching the grounding cable to the grounding screw/hub on the mixer.

Question 5

What are two additional physical measures that can be taken to reduce low frequency feedback in cases of extreme inteference such as large festivals?

Answer 5

An aditional layer of concrete blocks can be placed under the frontennis ball/concrete block fix and additional ballast i.e. craets of beer or water can be strapped to the table to weigh it down further (they should be elevated from the ground when attached)

Question 6

How can you test for feedback in your turntable setup at a pre-gig soundcheck ?

Answer 6

First set the input gain with a quiet record playing against a digital record, with the input gain set (should be high) drop the needle on the silent locked groove at the end of the record and then tap the side of the turntable; if it is not properly isolated the amplified tapping with be accompanied by low-pitch swelling and/or a mid-range whinning/static frequency.

Question 7

Describe how to use the on/off light on an analogue turntable to check the pitch slider and turntable motor are correctly synchronised

Answer 7

Check the guide on the turntable to find out which row of dots relate to which speed setting, then move the pitch slider to each of the four settings and check that the appropriate row of illuminated dots on the edge of the platter remains stationary

Question 8

What are the two types of cartridge and what are the advantages/disadvantages of each?

Answer 8

Moving Magnet - this is the most common type of cartridge; the advantage is that the stylus is easy to replace the disadvantage is that the reproduction of sound is less accurate due to the weight of the magnets
Moving Coil - this less common type gives a better sound-reproduction due the coils being light enough not to affect the tracking of the stylus; the disadvantage is the sytlus is more difficult to replace.

Question 9

Explain the basic four step process of balancing the needle

Answer 9

(After removing the extra counterweight) First calibrate the counter-weight so that the tone arm balances perectly (i.e. floats in mid-air), next rotate the inner ring (without changing the counterweight) so that it shows ‘0’ at this setting; thirdly, adjust the counterweight using the inner ring’s number guide to be 3.5 i.e. 3.5 grams of weight at the needle; finally, adjust the height of the tone-arm at it’s base f needed so that the tone-arm is at a relatively flat level (not steeply inclined)

Question 10

What is the default setting for the Anti-Skating control and how should it be adjusted if there are problems with the needle skipping/skating towards the center of the record?

Answer 10

By deault the Anti-Skating should be set to 0, and increased (e.g. towards “3”) if there are skipping/skating problems with the needle

Question 11

what size of record might you use a turntable’s 45 adapter for?

Answer 11

A 7” vinyl with a large centre-hole

Question 12

How can you usually identify a breakdown/bridge section on a vinyl record?

Answer 12

A breakdown will appear visually as a lighter/lower-density of grooves

Question 13

What feature on a vinyl’s surface helps you to find where each track is (when there are multiple tracks)

Answer 13

A silence buffer should be visible as a light ring (i.e. no grooves) to show the seperation of tracks

Question 14

What speed does a 7” record play at and roughly how many minutes can it hold per side?

Answer 14

45rpm and 5mins per side

Question 15

Roughly how many minutes can a 12” record hold per side ?

Answer 15

22mins per side

Question 16

Why might a record be jumping when you attempt to cue it even though the tonearm is set correctly ? How could you fix it ?

Answer 16

The centre hole in the vinyl might not be snug around the platter spindle and therefore slipping; you can put a sticker over the hole (on the underneath side) and then put the spindle throughto add extra material inside the hole. You can do this multiple times.