Cyg amp makeover

[Devotee]

Awesome thread, really looking forward to seeing how this turns out!

[Cygnus X1]

Terminal strip risers are rough mounted on lexan.
Almost ready to start wiring those, still working out tube positions.

Also almost made a massive "boner" on orientation.
I'm used to making heads with the tubes upward, so everything is upside down and
reversed.
If I stayed with this layout then the power tubes and power transformer would be on the same side as that offset
speaker.
Bad idea on many levels...weight would be all on one side, and possible physical and
electrical (magnetic) interference with the speaker.

Good thing about building on lexan is I'm not committed, I can just flip it.

[Cygnus X1]

Another reason to use lexan instead of directly mounting the strips to the
chassis is for vibration.
Using nylon spacers will help absorb the shock of living in a combo environment.

[Cygnus X1]

Been busy with this all weekend.
No pix at the moment but the boards are built and soldered.

[Cygnus X1]

Ok, so this shot isn't very sexy but it represents a large portion of the work.
The boards are built and the leads are soldered in place.
Just making sure everything fits before I go ahead with the tube sockets and everything else.

For those who have no idea of what they are looking at, here's some explanation.
At the top of the picture you see the pots, and of course that will be the front.
Jacks, switches, and all of that will attach to the preamp an phase inverter on that top board.
Then the holes for the tube sockets in the center.
Chassis mount only for this dog.
I don't care who does it, or how many times it might just work, I will not mount pots, switches, lights,
etc. directly to boards.
I use the term "boards" loosely here.
It's all on terminal strips, true point-to-point wiring.
(Thank you John...JCable...but I'm quickly running out again!!!)
No circuit traces, printing and etching, or downsizing for savings.

But I'm not going to start arguments about whether printed circuits can be reliable (of course they can),
just showing how I build my amps.

The bottom section contains the power supply itself, bias section, and hookup for the output transformer.
I give it plenty of room for heat dissipation and for possible changes if I have to draw down some voltage
according to the double oversized power transformer I am using.
Never promised it was going to light!
Amp techs might observe the bias supply for the power tubes.
Yes, they are split, and yes they will be cathode biased.
Throw damn near any set of mismatched power tubes in there and they will at least work.
Mix and match for tone.
Don't adjust, there is no need or provision.
It ain't a hi fi amp...it's a guitar amp and believe or not mismatched power tubes can sound better
than a closely matched set in fixed bias.
Besides...from scope work the self biasing nature brings those two within 10% of each other regardless.
Sometimes we drink way too much kool aid (IMO).

So, there's the ugly shot, the leads are just tucked away all over the place.
Next will be installing the tube sockets and wiring the rest up.

[Cygnus X1]

Components are:
Minimum 1 watt metal film resistors.
Flame proof in the high voltage (plate) portions.
Ceramics 5W minimum for all of the power side and bias supply.
First filter cap is rated at 600V.
"Tone" including bypass caps are Mallory 150's or equivalent poly.
Silver mica treble cap (most use ceramic, yuk).
1000V dual diodes for rectification (most use 400V, singles).
Switches will be 10 Amp (again far over rated, most use 3 or 4 amp)
Metal jacks, not plastic.
What else?
I'll think of something.
Ceramic sockets (some builders hate them, they are kind of unforgiving)
Iron is indeed vintage, the power transformer came from a huge Baldwin organ running a dozen tubes.
Output transformer came from a 50 watt 50's PA amp.
I like old iron!

[Cygnus X1]

Removed my rambling thoughts and rants about amp designs.

Too distracting!



(OK, a little too much beer as well).

[straycat]

Very impressive Mr Cyg great work so far!!
Darn purty innards too.

[axe dude]

Awesome Stray! Looking good Buddy. Thanks for posting up the pics & keeping us informed Rich! \m/

[straycat]

Awesome Stray! Looking good Buddy. Thanks for posting up the pics & keeping us informed Rich! \m/

Cyg is posting the pics from somewhere in a secret amp lab up in the galaxy Cygnus X1.

[Cygnus X1]

It Is Working!


Now just to tidy up and fine tune.

[Cygnus X1]

[Cygnus X1]

TBH I can't believe it worked on first fire up.
Reversing everything was tough!
Even flipping the drawings in Autocad didn't help much,
because although it gets the layout right, the pots and tubes don't
really "flip".
They stay the same.
So each and every connection had to be planned out one at a time.

[straycat]

I'm happy for you Cyg good job!!
Looks great too.

[Cygnus X1]

Not so fast!
The tone stack isn't working right.
Mid acts like a funky tone pot.
Bass and treb have no effect.

I think I made a mistake!
The horror!





Back at it in the morning.
I'm working crazy early hours.