Tube Guitar Amplifier Designs

Tube guitar amp designs & schematics

Read "Tubes Mechanics & Mystique" to understand a musician's love for tube amplifiers and why they are still used today.

For care and maintenance of your tube amplifier read "Tube Amplifier Care and Hygiene" and "Survival Tips for Tube Amps"

Here are the schematics to the greatest all-tube guitar amplifiers of all time. These designs are an inspiration to musicians and amp designers because of their simplicity and sound quality.

Fender "Champ" 5F1 schematic
Fender "Deluxe" 5E3 schematic
Fender "Twin" 5F8 schematic
Marshall 50W "Standard" 2204 schematic
Marshall 100W "Master Volume" 2203 schematic

Here are the schematics of great amplifiers from other web sites.

Ampeg	from Unofficial Ampeg Page
SVT power amp (6146)	SVT power amp schematic (6146)
SVT power amp (6550)	SVT power amp schematic (6550)
SVT preamp	SVT preamp schematic
V2 power amp	V2 power amp schematic
V2 preamp	V2 preamp schematic
V3 power amp	Ampeg V3 power amp schematic
V3 preamp	V3 preamp schematic
V4 power amp	V4 power amp schematic
V4 preamp	V4 preamp schematic
V4B power amp	V4B power amp schematic
V4B preamp	V4B preamp schematic
V9 power amp	V9 power amp schematic
V9 preamp	V9 preamp schematic
VT-40 power amp	VT-40 power amp schematic
VT-40 preamp	VT-40 preamp schematic
Fender	from Hoffman Amplifiers
5E3 Deluxe	5E3 Deluxe original schematic
5F6A Bassman	5F6A Bassman schematic
Marshall	from Joe Piazza's Backstage
Marshall 1986	Marshall 1986
1986 Bass Mk II	Marshall 1986 Bass MKII
1987	Marshall 1987 (plexi)
McIntosh	from Triode Electronics
MC-30	McIntosh MC-30 schematic
Stromberg-Carlson	Just because dad had one!
AP-80	Stromberg-Carlson AP-80
Vox	from Joe Piazza's Backstage
AC-50	Vox AC-50
AC-100	Vox AC-100
Vox	from Triode Electronics
AC-15	Vox AC15 schematic
Wurlitzer	from Triode Electronics
Model 680	Wurlitzer Model 680 schematic

Modern demands upon a musician's sound quality and flexibility have led to the following designs.

20 W Guitar Amplifier schematic
   - preamp gain (clean to distortion)
   - 3 band equalizer
   - stereo
   - effects loop (mono and stereo)

Guitar Preamp schematic
   - preamp gain (clean to distortion)
   - 3 band equalizer
   - line output

40 W Stereo Power Amplifier schematic
- perfect match for the Guitar Preamp
- hi-fidelity sound quality

EL34 & 12AX7 electron tube specifications

Why the Design

First of all, MOSFET amplifiers are a much better choice for high fidelity and power amplification. However, the tube amplifier provides a better tone and sound quality for instrument amplification. There are several reasons for this. The tube preamp is better suited for impedance matching of the guitar pickup. Transistors are noisier compared to tube circuits that can achieve a better signal to noise ratio. When the tube amplifier is "overdriven" by transistors, the transistors can really be heard. An all tube design is needed for a clean sound.
Thus, noise gates were invented. A simple straight forward tube amplifier design works best for guitarist. Multiple guitar sounds are needed especially during live performance. In a recording situation, a simple tube amplifier works great because effects should only be used during mix down. Multiple guitar sounds are needed especially during live performance. An effects loop is a necessity.

This signal path does the trick.

[guitar -- tube preamplifier -- digital signal processor (effects) -- tube amp/speaker combos]

PREAMP DISTORTION- Tube distortion has far better tone and sound quality than transistors or DSP (digital signal processor) distortion. When a tube amplifier starts distorting even order harmonics are introduced, smoothly squaring the signal. Distorting transistors add odd order harmonics to the sound. To simulate the tube distortion the signal is usually "clipped" abruptly to distort the signal. DSP distortion is achieved by adding a wave form to the original signal (usually a square wave). A tube preamplifier can be set so when you play a string soft there is a cleaner sound and when you pick hard there is distortion yielding more "human control" of the sound.

AMP/SPEAKER DISTORTION- Ah that blues sound. Listen to great blues musicians. There is distortion but not like killer heavy metal distortion. This is because the distortion is mostly from the power tubes being overdriven and the output transformer saturated. Preamp "clipping" distortion is kept at a minimum for a blues sound. The nice thing about power amp distortion is the compression and sustain that can be achieved.

TURN YOUR AMP DOWN- Sound engineers and band members have to compete with guitarist on a 100W Amp. Unfortunately, "cranked all the way up" is the range that tube amplifiers sound the best. This drowns out the vocalists and gives the sound engineers a bad hair day. Ideally the sound engineer needs to be able to control the levels of all the musicians during a live performance. When the guitar amp is cranked up the level at the mixing board is usually turned completely down. This is because the blasting guitar amp is being picked up by the vocalist microphones. The sound engineers have little control over the guitar "mix" and of course the producers hear all about it! In the studio, it is hard to record with the amp levels at "10", because it is difficult to record and hear the headphone playback. O.K I'll admit I have a 1989 Marshall 2203 100 W Master Volume and even pulled tubes out to get that sound at a lower volume.

CONCLUSION- Design a small all-tube guitar amplifier with a tube preamp for "clipping" distortion and an effects loop for today's sound requirements. Because digital rack mount effects are in stereo, a dual tube power amp with a guitar preamp is ideal.