Another Cygnus Amp

[Cygnus X1]

Is born.


Settled on a new name as well.
"Cygnus 7" for the max estimated 7 watts.
Similar to the prototypes (3 of them) it is
designed for full gain and tone at low volume.
Faceplate is being made, and I am working on the head cab.

Configuration is Gain 1, Gain 2 , TMB, Master Volume.
4, 8, 16 ohm speaker, and Line Out.
Cathode biased (self biasing) plug and play 6V6, 6L6,
KT88, 6550 family. 2 x 12AX7A preamp (3 gain stages plus
cathode follower tone stack).
Good cleans, great dirt tone.

(Whatever early 80's Scorpions used is what the dirty sounds like on this amp).
I run it through a Peavey 5150 block logo 4x12 and it sounds perfect.
Gets loud enough to rattle the windows at the other end of this 85 foot
long ranch style brick house, but sounds awesome as well at whisper level.

Here is a quick chassis shot:

[DonP]

Shit Cyg.

I wish I could get off my lazy ass and build one. I pulled apart a Marshall Micro Stack head to convert it into a tube amp, may years ago LOL! The thing holding me up - I need a new chassis because the 3005 chassis is upside down. Also, I'm not sure is I want Class AB or a simpler Class A.

What trannies did you use?

What's your B+?

I usually use a 2203 preamp circuit. You can't go wrong with that.

Are you using a negative feedback loop?

Got a Presence control in there?

[Cygnus X1]

Shit Cyg.

I wish I could get off my lazy ass and build one. I pulled apart a Marshall Micro Stack head to convert it into a tube amp, may years ago LOL! The thing holding me up - I need a new chassis because the 3005 chassis is upside down. Also, I'm not sure is I want Class AB or a simpler Class A.

What trannies did you use?

What's your B+?

I usually use a 2203 preamp circuit. You can't go wrong with that.

Are you using a negative feedback loop?

Got a Presence control in there?

Thank you Don.
You are one of my "go to" guys for tech I have been too lazy to study up on.
You have it in you!
Do it!!!!

Power transformer: a genuine oddball. No center tap, I use a full wave bridge 4 diode setup. I sincerely believe this contributes to the tight sound. I did not want any sag on this one. 150ma for an approx max 70ma draw.

B+ is around 365VDC.
That transformer has a lot of options-I have gone anywhere from 280 to 430. 360ish is the happy medium for all the tubes I have thrown at it.

No NFB, it doesn't need it.
Amazingly I have not ever had a problem with parasitic oscillation EXCEPT when I monkeyed with the grounding scheme. So I leave out the NFB altogether to let through that "raw" tone that I love.

Oh, and another detail.
The grounding.
I could build this amp in a cardboard or wood box.
The only grounding to chassis is for safety-the power ground and one for the filaments tied to the PT stud.
Everything else absolutely "floats".
Dead quiet!

I worked on the prototype both virtually and actual building/tearing down to alter it from the initial AX84 SEL
fuzzbomb to what it has become.
6-8 months of it.
And some improvements in baby steps along the way.

Also played with options (effects loop-didn't like it), Champ mode-it's OK but not all that usable. Channel switching-again, it sacrificed tone.
Everyone wants an amp that does everything well.
I just wanted to achieve that goal...do low volume very well and use techniques of top custom amp designers.

[rstites]

Looks good. It makes me want to get back to building. I have an amp I designed several years ago, order the parts for about 3 years ago, and then have proceeded to move twice with everything still packed in boxes....

[Cygnus X1]

It is addictive.
I have another side hobby of converting old tube gear into guitar amps.
Tweed Deluxe 5C3 (octal preamp tubes, 1952 style) from a cheap monoblock.
Matchless Spitfire from a small 50's organ amp stage.
I have a Masco PA just dying to become a JTM 45.

[Cygnus X1]

Update:
(Removed pic, updated Jan 2011):

[john.w.lawson]

Think you can make me a rattlesnake cage? j/k looks real nice!!