Danger Will Robinson! Tube amps will kill you

Just the standard warning about high voltages. Tube amps have got really high voltages in them. Don't touch your computer screen while viewing this blog either. That could really zap you. But in all seriousness, tube amps can mess you up bad, including killing you, did I mention this? So please do not ever play with one or stick your finger in one, wondering whether I was kidding or not. Because I'm not.

Tube phase shifter!

ohhh.... ahhh.....

http://www.solorb.com/elect/musiccirc/liquidator1/

Interesting tube amp articles

Is the Vox AC-30 really a Class A amp?

• http://www.aikenamps.com/VoxAC30classA_2.html

Tremolo design options

1. Several different power-amp bias modulators: http://www.lynx.bc.ca/~jc/tremoloCircuits.html
2. Input stage bias modulator: http://www.lynx.bc.ca/~jc/supro_s6616.pdf This one is interesting because the LFO drives a source follower connected to the cathode of the input tube! Have to look at that carefully.
3. Typical Fender LDR tremolo. extensive analysis: http://terrydownsmusic.com/technotes/vibratocircuits/tremolo_circuits.htm

Building amp and speaker cabinets

Working with Tolex

http://steelguitarforum.com/Forum11/HTML/008611.html

Some plans for different cabinets

• AX84 1x12 speaker cabinet http://www.ax84.com/static/corecabinets/AX84_1x12_Cab_09.08.03.pdf
• AX84 head cabinet http://www.ax84.com/static/corecabinets/AX84_1x12_Head_Cab_090803.pdf

Tube amp resources and web pages

Comparison of various tone stacks

http://amps.zugster.net/articles/tone-stacks#BlondeTwin

Yet another guy who's made a bunch of different tube amps in his spare time.

http://www.naturdoctor.com/Chapters/Amps/

AX84 - the cooperative tube amp project

http://www.ax84.com/

Tube Amp Schematics and equations

http://www.aikenamps.com/Equations.htm

DIY Tube Guitar amps

http://www.diyguitaramp.com/

Tube guitar amp schematics

http://www.drtube.com/guitamp.htm

Fender and Ampeg schematics and layouts

http://www.turretboards.com/schematics_library.htm

MOSFET tremolo circuit

http://www.geofex.com/Article_Folders/sstremolo/sstremolo.htm

Terry Downs technical notes

http://terrydownsmusic.com/technotes/TECH.HTM

Digital effects unit for tube amps

OK, there's no such thing as a special purpose digital effects unit for tube amps.

First I need to find a place in the amp that can work as a mixer stage, as close to the power amp as possible. Then I need to attenuate whatever the signal is at that stage down to the correct level so as not to fry the input of the effects stage. Following the effects unit I will need a gain stage to take the effects level back up to whatever it was coming in from the previous gain stage.

Thinking about using simple resistor divider on the FX input and a MOSFET gain stage post FX.

Maybe this is best done with an amp using a long-tailed phase invertor since that can act as a mixer stage.

Speaking of the effects board itself I am considering the Spin FV-1:

http://www.spinsemi.com/knowledge_base/demo_board.html

Here's a page describing this board used in a guitar amp. I would prefer not to run the entire signal through it - just the effects send, keeping the dry signal intact.

http://www.spinsemi.com/guitar_amp_application.html