Custom vs. Vintage

Which is best? New custom harp amps or tweaked vintage guitar amps?

I had an interesting conversation about harp amps recently with a good West Coast gigging blues harp player. He was very skeptical of harp-specific amps because of their one-trick nature. I think he preferred to start with vintage guitar amps and tweak them to his tastes, which include a broader tonal palette.

That frames the choice pretty well.

Getting good harp tone out of an amp can be a delicate balancing act. You need low-watt speakers that are always on the edge of breakup. You need to tame the input section of the amp to avoid screaming feedback. You want to tip the amp into overdrive when you put a tight cup on your bullet mic. And you want all of this to stay balanced at a variety of volumes and in different venues. Yikes!

People tend to defend their choices, especially if they shelled out a considerable amount of money on them. Owners of boutique harp amps often say they grew tired of trying one amp after another looking for good harp tone, and they finally ended their quest by spending a lot for a specialty amp. But my West Coast friend has a good point: Harp specific amps usually have one voice (usually tube overdrive), and they are tuned to the ear of the builder.

[To be fair, one harp amp builder who springs to mind hawks his 4x10 amp as versatile. He even ships extra tubes with the amp to vary the tone. But if you are jacking tubes in and out of an amp to sculpt the tone you are back to tweaking, same as the guy with the vintage guitar amp. What did you spend all that money for?]

Getting good harp tone out of an amp may be tricky, but it is not rocket science. There are a few basic principles to keep in mind:

-> A bullet mic puts out about fifty times more energy to the amp than a guitar. This exacerbates the fundamental feedback problem that stems from walking around on stage with an open mic in front of a powerful amp. You need to lower the gain of the amp input section. Guitar amps generally use 12AX7 tubes for this, but you should substitute lower-gain tubes such as the 5751 (my favorite tube for V1) or the 12AY7. Some harp guys use the 12AU7 tube but it is not truly interchangeable with the 12AX7 since it draws more current and using it may damage other components in your amp.

-> The lower-gain tubes should be used not only in the preamp sockets, but also in the Phase Inverter (if you have multiple power tubes in your amp). The PI has a gain component as well.

-> The 5Y3 tube is often standard as the rectifier tube, and it works well for harp.

If you buy a boutique harp amp the builder will have already made these choices for you, but the combinations and permutations of various tubes (and their effects on tone) are nearly endless. You will surely fined yourself tweaking your amp, whether it is a new custom or a smelly old vintage.

As I mentioned earlier, you will want to use low-watt speakers. You gotta resist the guitar player’s urge to go for speakers labeled as 100 watts, or other nonsense. Those speakers will be stiff and lifeless in your harp amp. 15 to 25 watt speakers work well, either alnico or ceramic. Ribbed cones sound cleaner; smooth cones break up earlier.

Harp amps with multiple speakers sound best with non-matched drivers. Use both alnico and ceramic speakers in the same cab. Use eight-, ten-, or 12-inch speakers in the same cab. Use speakers from different vendors, such as Jensen and Weber. And don’t spend a fortune on speakers… Harp amps often sound best with medium priced speakers, not elite guitar speakers. My favorite harp speaker is the Weber 10A125-0.

Some harp guys insist on using only expensive New Old Stock tubes, but I’ve found some newer tubes sound fantastic and cost a fraction of the price. Try the Tung Sol new production tubes in both the input and power sections. To my ear they produce excellent warm tone.

So which is best? A new custom harp amp or a tweaked vintage guitar amp? If your skills as a player are progressing (and your skills should always be progressing) you will eventually grow beyond the capacities of your amp, be it a custom or a vintage. Unless you are congenitally disinclined to tinker, you will likely start tweaking your amp to broaden its range of tones. You may start asking yourself why you paid all that money for a boutique amp in the first place.

[Note: The mods I have suggested do not include many other things you can do to improve tone, but those other changes usually involve a soldering iron and a multi-meter. The mods I have listed will have a dramatic and immediate effect on tone. As always, use care when modifying any tube amp. There are voltages that can kill you, even if the amp has been off and unplugged for some time.]