This brief article is based upon my own personal experience with the Ultra Tonic V4 pickup.
I am not paid for my opinion on this product, nor has it been supplied to me for free. This is not an advertisement. I am sharing what I know as a courtesy to you, the reader.
When I encounter a quality product and am able to successfully demonstrate its value, I often become enthusiastic. Please don't mistake my genuine enthusiasm for some cheap attempt at marketing.
The James May Engineering (JME) Ultra Tonic Pickup (UTP) for steel string guitars has been updated to version 4. Like its predecessor, the Ultra Tonic V3, the Ultra Tonic V4 is a passive, bridgeplate-mounted, soundboard transducer (SBT) pickup with on-board feedback suppression and a soundhole-mounted volume control.
Version 4 of the Ultra Tonic adds a silver-nickel shield can over the volume control circuit to reduce susceptibility to EMI interference, a bonus for players who have to deal with light dimmers. For builders, the V4 includes an extra 2-position dip switch on the main circuit board for testing purposes. The 12-position DIP switch array, used to set the feedback immunity during installation, has been adjusted to accommodate more extreme guitar construction variations.
I like the Ultra Tonic V4 for all the reasons I like the Ultra Tonic V3. It is straightforward to install, requires no battery, sounds clean, has a "color-less" volume control, and provides unmatched onboard feedback suppression! The extra shielding added to the Volume Control on the V4 is a bonus.
If you are insisting on purely hearing your guitar, only louder (with NO hint of piezo "color" or "quack", or magnetic "electric" sound), you may want to start with a quality microphone, and learn to deal with the EQ and feedback issues. However, for many (if not most) performing guitarists, a microphone may not be practical.
Alternatively, you can train an "Impulse Response" or "WaveMap" on a specialty preamp such as the ToneDexter II, using your favorite microphone. Such a device can markedly improve the sound of most any piezo pickup, though you will benefit by beginning with a quality pickup source. With or without a ToneDexter, the Ultra Tonic V4 may be just the pickup you have been looking for.
You can read more about the Ultra Tonic Pickup on the James May Engineering website » James May Engineering.