Firefly build

[M Fowler]

The yellow E-cap on the board is in backwards I believe.

[rbryerton]

Made in USA....hella cool LMAO

Well, when you have it dialed back (during the AC/DC stuff) it sounds really, really good!

The first part of your clip where you're increasing the gain and it starts cutting out, it sounds to me like blocking distortion. There's way too much signal hitting the grid of the tube following your gain/volume control I'm guessing.

If you can induce this condition by turning up the gain, then it only follows that you have too much gain, right? I'd try putting in a voltage divider after the gain pot....maybe a 470k (play with this value) to ground before the V2b grid and see what that does with the gain pot turned all the way up.

You've got several cascading gain stages with no inter-stage attenuation between them except for the gain pot, and they're slamming into the output tube...

Cool little amp! I'm sure someone else will listen to your clip and add some suggestions....

Good catch on that yellow cap Mark.

Check out this link http://www.aikenamps.com/BlockingDistortion.html

P.S. Seems you have quite the co-ax fetish

[selloutrr]

Did you modify the amp?

When I built the firefly it just fired up and worked and sounded fine I'm not sure why you are having problems.

[xtian]

The yellow E-cap on the board is in backwards I believe.

It's NP (non polarized).

If you can induce this condition by turning up the gain, then it only follows that you have too much gain, right?

Yes. Matches my thinking. I'll try adding the resistor as you suggested.

P.S. Seems you have quite the co-ax fetish

Was a PITA, no doubt. But this is my first tube amp build, so I went overboard.

Did you modify the amp? When I built the firefly it just fired up and worked and sounded fine I'm not sure why you are having problems.

I didn't modify anything except the layout. Like most folks, I left off C8 across the OT output.

[xtian]

I am smiling from ear to ear.

I added a 33K resistor in parallel with R12 which feeds the power section. This dropped the resistance to roughly 30Kohms, making the 12AU7 much, much happier.

The fizz is gone, and this amp is now super musical. I am amazed by the variety of tones from this simple circuit! As advertised, it's very bright, but it's very responsive to the tone control on my guitar.

In a week or so, I'll post a wrapup after I experiment with the ECC99 output tube and add the wire pull handles and wooden base.

Thanks again for all your help, team!

[rbryerton]

Good job, glad to hear you solved your issue! It seems the simple circuits always sound the best for some reason...

Enjoy your amp... it's very satisfying building something that sounds so good, isn't it?

Your amp looks like a good experimental platform for learning: nice simple circuit, and you can play around with changing values here and there to learn what each does to the sound. This is a great hobby, but if your not careful, you'll end up with a room full of amps before you know it!

[xtian]

If your not careful, you'll end up with a room full of amps before you know it!

You, sir, are very ill. That could never happen to me. I won't ever build another tube amp. Well, maybe just one…or two…

[selloutrr]

becareful you might end up like this. I have to rotate amps between the jam room and storage. my amp habit probably rivals whitney's crack habit The pink one is my daughters firefly.

[M Fowler]

Guys I have a 8' x 20' car hauler trailer that can fit all those amps and speakers in, when do you want me to roll by

Nice looking gear guys: G.A.S. I love it.

[rbryerton]

Wow, OK, I don't feel so "bad" now....looks like I still have 2 more walls to fill

[selloutrr]

don't feel "bad" at all unanounced to me.. lots of amplifiers is actually a turn off to most women. lol

[xtian]

Finished Firefly build photos! I used a walnut and maple base with 3/4" rubber feet. Sounds awesome with the vintage Packard Bell 12AX7's from the old console stereo, and a JJ ECC99 power tube.