I have installed v3.0.0 on Win 10 Home and am impressed by the set of features.
Digitising classical LPs I am getting a tinny and slightly muffled result. Applying Effect > Bass and Treble to a selection failed to fix it. The twin audio cable output is available on the Ion Profile Pro turntable but not so far used. Output from the player is by USB cable. Any suggestions?
Are you listening to the LP while recording?
If so, check that you are actually recording from the USB and not from your laptop’s built-in mic. To test, just shout at the computer while recording. If your shout is in the recording then you are recording from a mic, not the turntable’s USB.
The recording input is set in the Device Toolbar.
(Ensure that the turntable is connected to the computer before you launch Audacity.)
Output from the player is by USB cable. Any suggestions?
I doubt this is the problem but make sure any/all [u]Windows “Enhancements”[/u] are turned-OFF. Audacity doesn’t mess with the digital audio stream but sometimes Windows does.
The twin audio cable output is available on the Ion Profile Pro turntable but not so far used.
Try connecting the analog output to your computer speakers or stereo system, etc., to see what the analog sounds like. You should be using the same speakers/system as your computer and at the same volume for an apples-to-apples comparison.
Some Ion turntables use a ceramic phono cartridge which is not as good as a magnetic cartridge. And, if you are not used to analog records your expectations may be unrealistic. 
Some older records were rather mediocre (even when new). And quality varied a lot, even near the of the analog era. The “rumor” was that classical records had better quality than popular records but I never owned any classical records.
Recording is from the turntable, which I set in Audacity. Listening is by headphones connected to the desktop PC.
Following DVDdoug’s suggestion I checked the drivers and searched on Ion’s site without finding any. It seems the motherboard/Windows defaults are used. It reported
Driver for USB Audio CODEC
No driver files are required or have been loaded.
HID-compliant consumer control device.
The turntable was used with more success a few years ago with an earlier version of Audacity and Windows. I am re-learning the procedure. So now have ordered an RCA Audio Cable 2 RCA Phono Male to 3.5mm Male Headphone Jack Aux Stereo to make use of the red and white audio connectors attached to the USB turntable.
If they are pre-1960 you may need a brand-specific de-emphasis equalization …
https ://wiki.audacityteam.org/wiki/78rpm_playback_curves
as the standard RIAA equalization built-in to your hardware is not going to match the recording.
The records are 33 rpm from the early 1970s onwards, eg. Deutsche Grammophon. I will experiment with others. Thanks.
When I did my vinyl transcription project (a few years ago now) I converted a fair few Deutsche Grammophon LPs from the early 1970s onwards - and I got excellent results when playing the digital WAV files on my hi-fi rig.
I used my old Technics SL-150 treated to a home-service and a new cartridge and SME 3009 arm
with an Artcessories pre-amp and an Edirol-UA-1EX USB soundcard (no longer manufactured).
If I was buying now I would get the Artcessories device that combine the pre-amp and USB sound card functionality (not available when I was working on this project).
I actually started out with an ION iTTUSB deck - but soon junked it as the platter was far too lightweight and I got far too much wow&flutter. The platter alone from my Technics weighs far more than the entire ION TT did! The ADC electronics in the ION were fine - but totally let down by the lightweight plastic construction.
Peter.
Instead of output to the PC via USB, I’m getting a much better result with the RCA Audio Cable 2 RCA Phono Male to 3.5mm Male Headphone Jack Aux Stereo, so making use of the red and white audio connectors attached to the USB turntable.
Using Line In to the Realtek high definition audio at first I thought I could output to Bluetooth headphones, but Realtek insists on handling both input and output. The connector supplies L and R signals to the single ‘Line In’ 3.5mm jack.
Thanks to those who contributed.