Humbucking pickups are certainly quieter, but there is general agreement they do not sound as good as single coil pickups. Usual comments are muddy lows, harsh midrange, dull highs, and so on. Single coils sound noticeably better, but always have some noise and can be noisy enough to be unusable in some locations.
Until now there was no other solution, but there is a way to get the best of both worlds –
The HSC Preamp
The HSC preamp addresses the major tonal issue with using humbuckers, which is the impedance of the two coils loads each other as the voltage from each coil is summed in the pickup.
The HSC preamp operates completely differently than other buffer preamps that are currently available. Using your existing humbucker pickup, the unique circuitry senses the voltage signal of each coil separately, then combines the signals electronically and provides a low impedance unbalanced output to drive the rest of your signal chain (volume pedal, amp, etc). This preserves the single coil tone, you get the sweet extended highs, smooth midrange, and tight lows that a single coil pickup provides, while maintaining all the humbucking action. In fact, the noise level will likely be even lower.
The HSC preamp is designed to work with any dual coil humbucker, George L’s, Bill Lawrence, Tonealigner, etc. With the HSC, the frequency response is extended in both the bass frequencies and the treble, and is much more faithful to the acoustic tone of the instrument. The response of the guitar is more even across the neck, no more overpowering muddy bass notes or harsh highs, just sweet clear tone up and down the neck.
The only disadvantage is a small wiring change on your guitar, specifically the output jack must be changed from a “mono” type to a “stereo” type. Note that the stereo jack is fully backward compatible and it does not prevent using the guitar without the HSC exactly as before installing the stereo jack.
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The Technical Background
Construction DetailsThe HSC preamp is built to last, and features the following construction details
• diecast aluminum enclosure designed for excellent RFI and EMI rejection
• Polyester and Polypropylene film capacitors in the audio path
• High quality opamps
The HSC is hand built in the USA, and every unit receives a detailed quality control check on the test bench and with a pedal steel and amplifier.
How It Works
The normal wiring scheme for guitars is unbalanced, using the familiar two conductor guitar cord as shown in this diagram:
One of the pickup wires is connected to ground by the mechanical mounting of the jack to the endplate, and the endplate extends the ground to changer, strings, etc. You can see that the current generated in each of the two coils by the string movement must travel through the other coil due to the series connection of the two coils. This is the major flaw with a typical humbucker setup, the coils load each other.
Pickups do not have to be wired unbalanced, however they normally are since historically the inputs of most amps are unbalanced. This is how it has been done, but there is a better way, the way that dynamic microphones and other similar devices have always been connected…Use balanced wiring, with the signal conductors floating, and the shield at ground.
Here is a diagram of the complete system:
By using this wiring scheme together with the unique circuitry of the HSC Preamp, the two coils of the humbucking pickup are sensed separately and tonal impact of one coil loading the other is eliminated. An additional advantage to the system is the floating balanced connection is more effective at rejecting noise pickup in the cable, which is why this system is used for microphones and other similar devices.
The strings, changer, endplate, etc are still grounded as before by the mechanical mounting of the jack, but the pickup wires are not grounded at the guitar as in the unbalanced setup.
Ah, there is the downside, it is necessary to use a balanced cable to connect the guitar to the HSC preamp, and the guitar is not set up for balanced cables either… Is this a big deal to change?
Actually it is pretty easy - Balanced cables with ¼ inch tip-ring-sleeve (TRS) connectors are readily available at any music store, and the only change at the guitar is trading out the ¼ inch mono jack for a ¼ inch stereo jack and reconnecting the two wires on the new stereo jack.
A nice bonus to this wiring scheme is that it is backward compatible by simply plugging in a normal two conductor guitar cord. The guitar cord will short the Ring and Sleeve of the jack, automatically changing the wiring back to unbalanced… How cool is that?
Another important but not so happy note is this system is not compatible with guitar mounted volume and/or tone controls. Neck selector switches are no problem, but the two wires from the pickup must connect to the tip and the sleeve directly as shown in the diagram above, and neither wire can be connected to ground at any point in the wiring.
How Does It Sound?
The technical information is interesting, but the most important thing about the HSC is the improvement in the tone over humbucking pickups used in the normal unbalanced arrangement. The sound files below clearly demonstrate the difference.
The files were recorded using an early 80s SD-10 Emmons push pull guitar with a George L E66 pickup adjusted to 3/32 inch below the strings. The two wires from the E66 pickup were soldered directly to the TRS output jack. The signal path was chosen to eliminate as many variables as possible, with the only difference being inserting the HSC into the chain.
For the E66 unbalanced files, the signal chain was output jack to a George L cable 24 inches long to a tube preamp with a gain of 8 and an input impedance of 1 megohm.
For the E66 with HSC files, the signal chain was output jack to a 36 inch long TRS cable to the input of the HSC. A George L cable 24 inches long connected the output of the HSC to the tube preamp with a gain of 8 and an input impedance of 1 megohm.
The output of the tube preamp connected to an A to D converter with a 36 inch long George L cable. The digital audio was routed from the A to D converter directly into Wavelab 6. There is no EQ, reverb, plugins, or processing of any kind on any of files. Also note that no volume pedal was used in the chain, eliminating that variable also.
The parts were purposely played with very little vibrato to allow the raw tonal differences to be heard more clearly. With the direct signal path, no processing, no volume pedal, and minimal vibrato, the overall tone of the tracks is probably not what would be desirable for a steel track on a typical recording. This was done on purpose, since the intent of these files is to show the difference as clearly as possible.
The sound files can be heard by clicking the wav or mp3 links below. File size is about 500 KB for each mp3 file and about 4 MB for each wav file. If you have a fast internet connection loading the wav files should be no problem, otherwise use the mp3 links. The files can also be downloaded by doing a 'right click, save as'. If the files are downloaded they could then be played back by using an iPod or CD player to hear the difference through your personal amplifier.
Track 1 - E66 unbalanced - wav - mp3
Track 1 - E66 with HSC Preamp - wav - mp3
Track 2 - E66 unbalanced - wav - mp3
Track 2 - E66 with HSC Preamp - wav - mp3
Track 3 - E66 unbalanced - wav - mp3
Track 3 - E66 with HSC Preamp - wav - mp3
The Emmons push pull and the E66 were chosen for the sound files since they are well known standards. The tonal difference using this setup will be similar to other guitar/pickup combinations, so if you own for example a Carter with a Bill Lawrence XR-16 pickup the change will be about the same. The bass will be deeper, there will be more high treble sparkle, and the nasal compressed quality and harshness in the 2-3 kHz range will be eliminated. Another benefit is the flatter frequency response when using the HSC will also allow you to use less EQ at the amplifier.