How to Use a Solid State Amplifier & Tube Pre-Amp

Mixing a tube preamp with a solid state amplifier gives the musician the best of both worlds.

Guitar amplifying equipment comes in two different varieties -- solid state and tube. Guitar enthusiasts argue over the pros and cons of both types. According to "the Noisy Audiophile" at www.soundstage.com, "Tube amps produce "highs" that are smooth, floaty and pleasantly real, but re-tubing an amp can be expensive; while solid state amps don't have the hassle of tubes, but they lack a certain musicality." By combining a tube preamp with a solid-state amplifier, you get the best of both worlds -- the warm musicality of the tube amp and the clean, punchy bass of a solid-state amp.

Things You'll Need

• Clean dry cloth
• Amplifier manual
• Preamplifier manual
• RCA, XLR cables or 1/2-inch instrument cables

Instructions

1. Unplug the amplifier and preamp for at least 24 hours before connecting the two. Clean all posts and connectors with a dry cloth. Clean the exterior of the speakers and the back of the amplifier, freeing them from all dirt, dust and debris.

2. 

   Check the impedance of the speakers.

   Check the impedance of the amplifier speakers. Look for a label on the back of the speakers, inside the back of the amplifier or in the manual. Impedance is measured in ohms, and most amplifiers produce either 4, 8, or 16 ohms. Make sure the preamp emits the same impedance as the speakers on your amplifier.

3. Check the AC line-in voltage. This shows the voltage of the input power source. Flip the "AC Line-in" switch on the back of the preamp to the appropriate voltage setting.

4. Check the output of the preamp with the input of the amp. Look for the voltage levels on the back of the speakers or in the preamp manual. Make sure that the voltage matches the input voltage of the amplifier speakers. Most preamps give off 0.7, 1.0 or 1.25 volts; a preamp with too few volts produces a low volume or "weak" sound. Likewise, too many volts can damage your amp. A "line level" preamp emits a range of voltage that can accommodate voltages between 0.7 and 1.4 volts.

5. 

   Use 1/2-inch instrument cables for amplifiers.

   Decide on the cables. Use "XLR" cables for microphones, "TRS" cables for stereos and 1/2-inch instrument or "RCA" cables for amplifiers. To connect the preamp to an amplifier, make sure the preamp gives off an "unbalanced" signal. For stereos and microphones, check the device specifications on whether they require a "balanced" or "unbalanced" signal.

6. Connect the preamp to the amp using the required cable. Run one cable from the left "Preamp Out" post to the left speaker input jack.

7. Run a second cable from the right "Preamp Out" post to the right speaker input jack.

8. 

   Use the "Line Out" jack for CD players and stereos.

   Connect any exterior equipment to the amp. Run 1/2-inch instrument cables from the appropriate port to the corresponding device -- the back of the preamp contains several labeled ports. Use the "Line Out" jack for CD players and stereos.

Tips & Warnings

• Most guitar preamplifiers come from the factory set to connect with amplifiers.

• Follow all safety warnings and precautions when dealing with electrical equipment.

References

• Speaker Impedance Matching
• Users Guide for the Ampeg SVP-PRO Bass Preamp
• Guitar Amp Tone and Effects Placement
• Musical Instrument Tube Amp Building, Maintaining and Modifying FAQ