The Broughton Audio P15 is a tube preamp based on the classic B15 bass amplifier. Broughton Audio calls it an exact recreation of the B15's preamp section, using one 6SL7 tube, with the topology of the later B15 models: the Volume control sits after the first gain stage, followed by the second gain stage driving the Bass and Treble equalizer1. It is a desktop or amp-top unit rather than a pedal, and it carries both an unbalanced line output and a transformer coupled balanced XLR output, so it can feed a power amp, a bass amp's return, or a mixing console.
Controls
The P15 keeps the control set simple: Volume, Bass, Treble, and a ground lift button1.
| Control | What it does |
|---|---|
| Volume | Controls the amount of signal transferred from the first gain stage to the second gain stage. It can be set to reach a line level output when using instrument level signals, and tube overdrive can be introduced at higher volume levels. |
| Bass | Standard shelving type equalization. With the knobs at noon, the frequency response is flat. |
| Treble | Standard shelving type equalization, matching the Bass control. |
| Ground lift | Connects pin 1 of the XLR to the chassis of the P15; releasing the button disconnects pin 1. |
The Volume control's ability to push the tube into overdrive at higher settings is the one place the P15 departs from a purely clean reproduction of the B15 preamp, and it is how the unit reaches line level from a passive bass1.
Inputs, outputs and power
The input is designed for mono instrument level signals via a 1/4" jack. A separate "Thru" jack passes the input signal unaffected to another device, such as a tuner or bass amp. The input is muted when neither jack is used1.
On the output side, the line output is an unbalanced mono signal from a 1/4" jack, capable of driving power amps or other equipment that accepts line level signals. The balanced output is transformer coupled and can drive long XLR cable lengths to feed a mixing console or other equipment accepting balanced signals, and it is stepped down from the line out signal. Both outputs may be used simultaneously. A high voltage MOSFET cleanly drives both outputs1.
The P15 runs on AC mains power, not a pedal supply: when ordering, you choose either the 115VAC model for North American voltage or the 230VAC model for European voltage1.
Tube, warranty and availability
The P15 uses a new production JJ 6SL7 tube. Broughton Audio states it chose this tube for all future P15 production because vintage tubes have become increasingly unreliable, and the company does not accept requests for different tubes1.
Broughton Audio products are covered for one year to the original owner, and tubes are guaranteed for 90 days. Warranty repairs are handled via sales@broughtonaudio.com1.
Players interested in Broughton Audio's other preamp designs can compare the Broughton Audio FlipTop, the Broughton Audio Super Stack DI, the Broughton Audio Messenger Pro and the Broughton Audio Archetype Tube Preamp.
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Questions
What tube does the Broughton Audio P15 use?
The P15 uses a new production JJ 6SL7 tube. Broughton Audio states it chose this tube for all future P15 production because vintage tubes have become increasingly unreliable, and the company does not accept requests for different tubes. The 6SL7 is the single tube in the circuit, which is an exact recreation of the B15 preamp section.
Is the Broughton Audio P15 based on the Ampeg B15?
Yes. Broughton Audio describes the P15 as a tube preamp based on the classic B15 bass amplifier, and calls it an exact recreation of the preamp section using one 6SL7 tube. The topology follows the later B15 models, which place the Volume control after the first gain stage, followed by the second gain stage driving the Bass and Treble equalizer.
Does the P15 have an XLR output?
Yes. The balanced output is transformer coupled and can drive long XLR cable lengths to feed a mixing console or other equipment that accepts balanced signals. It is stepped down from the line out signal. The P15 also has an unbalanced 1/4 inch line output, and both outputs can be used at the same time.
What does the ground lift button do on the P15?
The ground lift button connects pin 1 of the XLR to the chassis of the P15. Releasing the button disconnects pin 1, which can help with hum or buzz when the balanced output is connected to a mixing console or other equipment.
Does the P15 run on 115V or 230V power?
Both, but you choose when ordering. Broughton Audio offers either the 115VAC model for North American voltage or the 230VAC model for European voltage. Because the unit runs on AC mains voltage rather than a pedal supply, the correct model for your region matters.
How much does the Broughton Audio P15 weigh?
The P15 weighs 6 pounds. It measures 6 inches wide by 10.5 inches long, with an enclosure height of 4.25 inches; the handle extends another 1.75 inches for a total height of 6 inches.
What is the P15 warranty?
Broughton Audio products are covered for one year to the original owner, and tubes are guaranteed for 90 days. Warranty repairs are handled through sales@broughtonaudio.com.
Sources (1)
- P15 Tube Preamp, Broughton Audio
