Amp Computer

The problem here was banana cables.   At some point, the ‘Asshole Audiophile’ community got a hold of banana connections and now it’s damn near impossible to get banana cables at a reasonable rate.   I wanted to use banana cables instead of say, posts and alligator clips.    These guys :  Circuit Specialists solved that for me.   I paid a buck and a quarter per 20″ cable.  Woot!  Back on that soon, but the first two parts are in fab now!    I haven’t decided on the mounting system yet, Cheap boxes or panel/rackmount.   Tough call actually.

Real McTube III

This got some love yesterday.   The power circuit is done but not boxed yet.   I am going to box it separately from the foot pedal part because hey, it’s 140/12 power supply and it’s not like I’m gonna take it on the road.   I wired up the heater stuff, LED and footswitch yesterday and may take a crack at the signal today.   More on that heater circuit later, but these are the first two amp computer style components.

Real McTube Calculations

This is gonna take a while, I did the numbers and they worked out, but now I can’t find the book I used and describing this stuff is really painful.   I’m back into the Rider book but that is the most annoyingly pedagogical book I have ever read.   I’d love to find a good clean book on tubes, with our without the math but it must have full data sheet reading info

SongBird

I’ve started buying parts and will rip the old stuff out of the chassis soon.   There may be some original Gibson Transformers on EBay soon.  Maybe I will recreate the Crestline in the amp computer style.  Maybe the 102C84 will get up there.  That would be ridiculously hard to find anywhere else.

Now many of the options that I was considering are simply to try them out, with all other things being equal.   I have no real idea what effect they would have…  I want to hear them for myself.

Here is a quick list of things I am considering :

Input

• Fender vs. Gibson style grid stoppers,  Old school cap and grid.

Pre-Amp Stage 1

• Switchable bypass cap, Tweakable bias voltage,  Bias negative warning light, The Dave Hunter small cap mod, Other plate voltages

Pre-Amp Stage 2

• Variable NFB, Switchable “Tone Expander Cap”

Output Stage

• Switchable Bias Cap, Master Volume Control, Triode/Pentode switch

Power

• Standby Switch, Hum balance vs. rectified heaters, choke vs smoothing resistor.

That’s a lot of options and I’m pretty sure I’ve missed some.   So my plan is now somewhat different.   I am going to build the amp as an analog computer first.   The person who gave this blog it’s name calls it bread boarding, but I think of that as using the board with all the little squares.

I will create component boxes for all the pieces I need.  I’ll put banana jacks on them for connections and wire them up as need to try things out.   I’ll have generic parts, like decade boxes, alligator clip leads,  octal and nine pin tube sockets, pots etc. and I’ll make up custom stuff like switch sets, and transformer holders.

I’d like to have them all sitting on something stable.   Maybe I’ll put velcro on the bottom of all these boxes.   I think I’ll do the Real McTube II like this first.   Woo hooo.. this sounds like fun

This is a Polish Model (from wikipedia, I think).   Could it possibly look any cooler?   That’s gotta be an old school desk for a base.

Look at that bad boy!

So you would program these by plugging single conductor phone jacks into the various on board components.   Although this one does look a bit different.   Normally it would look like a ’40s telephone switchboard with wires all over the place.   This one is probably transistor driven.   Heathkit made a 75 tube model that is a behemoth.

So… you probably see where I am going with this…   but I will save that for the next post.