I have a Crosley 6005a. In turntable mode - sound is tinny and needs to be turned way up to hear it and it is not in stereo. Is this just the way it is or can I fix it. I bought it second hand

My guess would be Old Receiver, Amp ... have a phono input what is in a simple way a pre-amplified input , newer receiver don't . You just need to buy a small Phono Turntable Preamplifier ( less then $20 on line) you are going to install between the receiver and the turntable and you should get some sound at the right level.
Good luck.

If it is not equipped with ground wiring and sockets etc., it dont need it..

Quite possibly the sockets you put the deck is not designed for the playback of phono signals. They should be marked "phono".
Other issues are earth connections.

If you're using an old-school turntable that doesn't contain a phono preamp that will happen.

A traditional turntable requires a Phono preamp inline with it to PRE amplify and frequency-balance the minute signal produced by it's cartridge for later amplification by a power amp. Most stereo receivers and preamps have Phono connections and internal preamplification strictly for that purpose.

Recent AV Receivers generally do not.

The result would be very low, tinny sound.

If so, you need to get an external Phono Preamplifier.

Some modern TT

I can't find a reference to the TT-01, but if it's an old school turntable you need to run it through a Phono preamp.

It would help to know what electronics you're using as THAT is where the volume comes from.

The TT should be connected to a specific PHONO input as it includes special preamplification for a Phono cartridge and frequency shaping for the way LP's are recorded (Google RIAA). I imagine it may sound pretty tinny as you have it now.

Seems like the wrong input source has been selected. The gain on the LINE input is much, much lower than the PHONO input. Try changing the source knob to PHONO. Dont forget to lower the volume before you do this.

Is this a sudden onset problem or has it always been like this?

A traditional turntable requires a Phono preamp inline with it to PRE amplify and frequency-balance the minute signal produced by it's cartridge for later amplification by a power amp. Most stereo receivers and preamps have Phono connections and internal preamplification strictly for that purpose. Recent AV Receivers generally do not.

You don't say what electronics you're running this through. I suspect you have it jacked into a Line Level input instead of a specific Phono input. The result would be very low, tinny sound.

If so, you need to get a Phono Preamplifier.

This could be an earth lead to the cartridge problem, or the cartridge itself. Check the connections.

my Crosley CR6007A-MA turntable's sound is very, very low. You can't even hear it barely. I haven't had it long at all and it wasn't broke due to any sort of abuse. I really have no idea why it would do this for no reason! Help!

1. Assuming there is no problem with your amplifier of input cable, the headshell/tone-arm needs rewiring. This is very thin flexible wire and not easy to do, but can be done if you are careful.

2. Turntables require a special input on your amplifier which has a frequency response that is suitable for them. If you connect a turntable to an ordinary input, it will sound tinny. If you don't have a turntable input (known as a phono input [from phonograph]) you will need to use a preamplifier with your turntable.