Horrible distortion when recording 12" singles

[steve]

I would be very interested in the diagram you offered for your DIY volume knob

Hardly worth a diagram -
On the dual gang 10k pot there are two rows of three legs.
Take one of the rows and we'll call the legs (A),(B) and (C)
We will connect the Left channel input and output to this row of legs:

10k pot.png (6.81 KiB) Viewed 4077 times

Important. Use shielded cable throughout.

(A) Connect the centre wire of the input (from the turntable)
(B) Connect the centre wire of the output (to the computer)
(C) Connect the shielding of both the input and output.

With the other row of legs, do the same for the right channel.

note 1
It does not matter which row you choose for left or right channels but you must connect both up the same way.

note 2
It is not too important which way round (A) and (C) are (as long as it is the same for both left and right). One way round will require turning the control clockwise to make it louder, the other way round and you will turn it clockwise to make it quieter.

[mikeymike]

edit: beaten by stevethefiddle. shoulda read the thread 1st before replying hehe!

hi guys, sorry late reply but in replying to ouddingen's question, here is how to wire things up:

assuming you have bought a 10K dual ganged linear potentiometer (with 3 posts for each channel - this is important as there needs to be an input, an output and a ground post for RCA, while linear is important for normal volume control but not essential)... wire it up as follows:


so for example the "white" RCA input gets wired up as the blue shown above, and the white RCA output gets wired up as the red shown above. they will both need to be grounded on the same post.

then you flip the potentiometer around, and wire up the other RCA channel - the "red" one, the same way. one for input, and one for output.

actually -- here's a good page with decent pictures and info.

http://scarvell.net/wiki/index.php?titl ... AND_WIRING

scroll to the bottom heading "connecting the potentiometer" ... i should probably have just pasted this in here in the first place.. anyway, enjoy your volume knobs and happy recording!

[kozikowski]

Please note that Mr. Mike has the blue and the red backwards.

The hot signal is applied to the two ends of the control. The middle is a slider (officially the "wiper" connection) and selects any value between the shield (zero) and the maximum signal from the turntable depending on rotation. Stop in the middle of the rotation and half the turntable signal will go on to the computer.

Two messy things happen when you do this. If all your cables are short, you will notice immediately that all the sound control happens jammed in at one end of the rotation and almost nothing for the rest. This is what happens when you use a linear control (easy to find and cheap) instead of one that has been designed for sound. Since you're not mixing sound for the Boston Symphony Orchestra, nobody cares, but that effect is perfectly normal.

If you try to run the cables any distance at all, you will find the system picks up much more noise than before. The volume control messes with the quality of the connection--OK if you don't have long cables. That's why this configuration isn't available as a commercial product without extra electronics and batteries in a nice shielded box.

Koz

[steve]

Please note that Mr. Mike has the blue and the red backwards.

Perhaps...
It depends on what is meant by "input" and "output".
This diagram makes it clear (from the link supplied by Mr. Mike)

If all your cables are short, you will notice immediately that all the sound control happens jammed in at one end of the rotation and almost nothing for the rest. This is what happens when you use a linear control (easy to find and cheap) instead of one that has been designed for sound

That is true, but as you say, is usually acceptable. "Log" pots are also quite readily available, but if I remember correctly will make the situation worse with the illustrated connections. However, if the pots are wired the other way round (common ground connected on the right when viewed from the knob side of the pot, "hot" on the left) then the rotation of the knob will cause a more gradual change in volume, the only downside is that it will then work the opposite way round from a conventional "volume" control (Clockwise rotation of the knob will cause a decrease in volume).

A "nice shielded box" is preferable - this can be any metal box with the common ground wire connected to it, but many pots already have metal cases, and simply connecting a short link from the common ground to the metal case of the pot will usually suffice. Note however that many all plastic pots will provide better performance (less crackle when you rotate the pot) than general purpose metal case pots. Fortunately the input signal is likely to be sufficiently strong that (with reasonably short leads) the increased hum will still be barely noticeable even with a plastic box, provided that shielded cable is used throughout (though a grounded metal case is preferable).

[bneptune]

well, pat marcus, you are correct in thinking a preamp, or cheap 2-channel DJ mixer, would solve the problem. after hours of searching the web and forums, this one was closest to the issue i'd been having for the past week. unfortunately i just *upgraded* to windows 7 from XP and have had a lot of problems recording in audacity, esp. vinyl. the other day i finally got CDs to record (so i could edit, etc.), and figured i was done, had it figured out, but when i went to record a recent techno 12", nothing but clipping, and like you experienced, even with the on-board sound card input turned all the way down.

and unfortunately i am not savvy enough to rig up my own gain electronic device.

so here's my equipment / basic setup (regarding this 12" vinyl issue):

1 Technics 1210 turntable (non USB turntable)
1 Numark 2-channel mixer (or you could say it functions as a preamp), i forget the catalogue no., but it's about 10 years old. probably ran me $120 back then.
1 Rotel integrated amp (purchased in the early '90s, still great)
1 dell laptop w/ Windows 7 and its on-board sound card IDT HD (used to be called something else)
1 set of RCA cables to go from your Mixer to your amplifier
1 standard mini jack to go from your mixer / preamp output to your line in on your computer

and i'm running audacity portable on a flash drive.

sorry to drag this out, but boy, i'm relieved to have figured this out. so, i plug the turntable into the Numark mixer, either of the two 'phono' channels. i plug the 'master' output from the back of the mixer to the 'tuner' jack in the back of the Rotel integrated amplifier. i plug another cable (L/R) into the 'record' output from the back of the Numark mixer to the mic/line in into the Dell laptop (one of those standard mini jacks with two leads on one end and one on the other, to plug into an ipod to play on your computer or to perform this function).

In audacity under Edit>Preferences>Audio I/O I first select the Speakers option (not the soundmapping option) under Devices i think (sorry my flash drive is not near me right now so i don't have audacity open) and in the second box, Recording, I think, i select the Microphone/Line in option and also choose 'stereo mix' or '2-channel' or whatever that option is below the second box.

Once opened, your Audacity 'Line in' option to the right of the mixer tool-bar (i always float my meter tool bar and stretch it out to get as close to 0 w/o clipping that i can) will still be permanently greyed out and non-functioning. BUT the mixer tool-bar does seem to play a role in all this still, and i found for the best sound recording to leave the mixer input all the way to the right (1.0 i think) while recording. when i messed with it, and brought it down (to the left) halfway or say, to 0.2, the recording wouldn't clip, but it would shrink the overall wave and distort the sound.

by going from the pre-amp / Numark mixer you can now record vinyl without clipping simply by being able to have more control of the input volume. after playing with it for an hour or so, it seems to sound best when you turn the recording function in the Windows 7 built in sound board (IDT HD) down near '0' and turn up the gain and channel volume on the Numark mixer or preamp as much as you can without clipping. (as opposed to the opposite - turning up the volume on the Windows 7 device and lowering the volume and gain on the mixer - which sounded close to the other way upon playback, but maybe missing some of the highs). and i also have my playback volume function muted while recording. i don't know if that matters or not, all i know is i can go to bed tonight and not wake up tomorrow to the nightmare that i'd been having for the past half week. hope this helps you, or someone else too.

upon playback, don't forget to un-mute your computer's volume or you might get re-frustrated and wonder why in the world you can't hear what you've seemingly recorded.

sorry to everyone about my lack of correct terminology about some of these devices and/or toolbars, etc. i can try to explain it better when i'm not so frazzled. and yet relieved.

in summation, the only way i am now able to record vinyl without clipping using audacity (portable) in Windows 7 and its on board input device (IDT HD) is to hook my non-usb Technics turntable into my Numark preamp/mixer whose output runs to 1) my integrated Rotel amplifier and 2) my PC's line in.

-bn

[waxcylinder]

Thanks for the use-case bneptune (and glad you got it working ok).

To summarize: it is usually better to have recording hardware that gives you somewhere in the recording chain a hardware device that offers control over the signal level.

This is because it is not always possible to control the signal level in software (either Audaity or the operting system's sound services) for some combinations of recording hardware and operating platform.

In particular many of the cheaper USB turntables and tape devices seem to suffer from this
1) they have no gain/volume control (don't buy one like this!)
2) the device drivers used for the USB device inhibit software control of the signal level

WC