We’re all familiar with software plugins to help us with our music production. They’re a powerful way to add flexibility to an otherwise limited set of options.
Well, the original plugins were hardware in nature, and allowed for easy repair of amplifiers. Tubes have traditionally been mounted in sockets that allow them to be plugged in and swapped out.
With the Sandpiper, there is no need to re-bias when switching output tubes, so the user can freely substitute different tubes in order to change the character of the amplifier to something familiar, or something completely unique.
Character Plugins
Input Tubes
The EF86 tube has been around for some time, but it’s had reliability problems and until fairly recently has been discouraged for use in combo guitar amplifiers. The biggest problem was that these tubes were susceptible to microphonics which made them unsuitable for use in combo amps.
Modern versions of this tube, known as the EF806, are much improved in regard to microphonics, and, as a result, are excellent candidates for combo amps. These tubes are well liked for their clarity and detail, and for a distinctly different sound than what can be acheived with a 12AX7 or 12AY7 as the first tube.
If you have an interest in NOS tubes, an EF86 will pop right in to this socket and work fine, unless you run into problems with microphonics. Do not plug a 12A_7 type tube in this socket! They are not pin compatible!
Modern versions of this tube, known as the EF806, are much improved in regard to microphonics, and, as a result, are excellent candidates for combo amps. These tubes are well liked for their clarity and detail, and for a distinctly different sound than what can be acheived with a 12AX7 or 12AY7 as the first tube.
If you have an interest in NOS tubes, an EF86 will pop right in to this socket and work fine, unless you run into problems with microphonics. Do not plug a 12A_7 type tube in this socket! They are not pin compatible!
Driver Tubes
The driver tube is uniquely configured to provide twice the current and half the noise as most guitar amplifier circuits. The Sandpiper ships with a very high quality 12AU7. You may use any of the popular 12A_7 tubes, and you might want to experiment to find one that sounds right for you.
Power Tubes
The swappable power tubes are where much of the versatility of the Sandpiper lies. Want it to sound more like a small Tweed amp? Use a 6V6. More like a classic large Tweed? Use a 6L6 or 5881. More like a British stack? Use an EL34 or KT66. More like an early British combo? Use an EL84 with pin adaptors. More like an American rock bass stack? Use a 6550 or KT88.
All without having to mess with re-biasing or any other complications. It really can become many different amps depending on the output tube used.
Due to the wide-open circuit design, the character of each tube comes through in dramatic fashion. These are not subtle differences we’re talking about here, and it’s why there are no tone controls built into the amp itself. The tubes themselves act as tone controls. And, using different tubes with different guitars is quite possibly the best way to match your guitar to your amplifier.
All without having to mess with re-biasing or any other complications. It really can become many different amps depending on the output tube used.
Due to the wide-open circuit design, the character of each tube comes through in dramatic fashion. These are not subtle differences we’re talking about here, and it’s why there are no tone controls built into the amp itself. The tubes themselves act as tone controls. And, using different tubes with different guitars is quite possibly the best way to match your guitar to your amplifier.
Some frequently asked questions about the Austin Sandpiper
Amplifier as instrument?
The goal is to create an amp that extends the expressive capability of the guitar.
To do this the tubes are pushed very hard in order to create a smooth, gradual, musical, dynamic transition that exploits the non-linear characteristics of tubes.
The guitar has to respond to dynamics in a musical way, particularly when what you are after is a clean sound.
What kind of speaker is used?
A single 12" Celestion Alnico Blue speaker in a compact cabinet.
This speaker is considered by many people to be the best guitar speaker ever produced.
Beam blocking is also used to avoid glare when the listener is in a direct line with the speaker.
There are three output jacks on the back of the amplifier at 4, 8, and 16 ohm taps. Feel free to use any one of these with the built-in 8 ohm speaker for slight tonal and volume changes. It also changes the impedance reflected back to the power tube, so you may want to experiment with different taps for different tubes.
Basically, plug into which ever jack sounds best.
There are three output jacks on the back of the amplifier at 4, 8, and 16 ohm taps. Feel free to use any one of these with the built-in 8 ohm speaker for slight tonal and volume changes. It also changes the impedance reflected back to the power tube, so you may want to experiment with different taps for different tubes.
Basically, plug into which ever jack sounds best.
What is the impedance of the guitar input?
10 MegOhms.
How many watts is it?
Never measured it. Research discovered that watts are meaningless for what this amp is trying to achieve.
What tubes ship with it?
Input: EF806
Driver: 12AU7
Power: KT66
Driver: 12AU7
Power: KT66
Haven’t there been other amps made with swappable output tubes?
Yes, there have. But none like this. This amp is designed as an integrated unit, all the way from the cabinet to the speaker to the transformer to the tubes. It is completely unique, there is nothing else like it. All of the parts combined in this way make something that is much more than their sum, and is distinctly voiced as a total package.
Does the amp have a Personality of its own?
This is a good question because there are some amps out there with swappable tubes that have been criticized for not having their own personality. This is not true of the Sandpiper because it’s an integrated design that starts from the cabinet and works its way back through the (beam blocked) speaker, transformer and tubes all the way to its very high impedance input.
You can’t have this kind of result if you are just making a head, for instance, because you would be trying to accommodate all manner of speakers. But knowing exactly what the (beam blocked) speaker is influences everything upstream, from the transformer, to the tubes used, and to the resistor and capacitor values, which ultimately leads to a distinctive personality. So, yes, there is a personality here, but a personality that can be more than a one-trick pony.
You can’t have this kind of result if you are just making a head, for instance, because you would be trying to accommodate all manner of speakers. But knowing exactly what the (beam blocked) speaker is influences everything upstream, from the transformer, to the tubes used, and to the resistor and capacitor values, which ultimately leads to a distinctive personality. So, yes, there is a personality here, but a personality that can be more than a one-trick pony.
What if I want more controls or features?
As a result of its wide-open design the amp works very well with guitar pedals.
Reverb, for instance, is a feature that is much better left to an external guitar pedal, since there are so many different reverb types, and the choices in reverb pedals are many.
The same is true for equalization, compression, and other common guitar effects. It's the rare guitarist these days that does not have a pedalboard.
The same is true for equalization, compression, and other common guitar effects. It's the rare guitarist these days that does not have a pedalboard.
