From S100 to 2203

[fusionbear]

Hello Guys, I wanted to share the transformation of my S100 clone into a 2203 clone. I don't have final pics, but I will post later today:

http://s169.photobucket.com/albums/u223 ... d%20Build/

There were a few bumps in the road. My last 2200pf Mustard was bad and I forgot to link the 100k feedback resistor to the PI network, but after that she worked and sounded like a charm. I did do a few mods:

Bright cap on gain knob: 1750pf
V1a Cathode cap 1uf Solen
V1b cathode resistor 5.6k

I will leave it this way for a while and play with the circuit later if need be...

[fusionbear]

All done now:

Album:

http://s169.photobucket.com/albums/u223 ... d%20Build/

[fusionbear]

Made a few more adjustments. Bright cap was 1750pf, now 1390pf.
V1a cathode cap was 1uf, now .68uf. I'm happy:

Clip:

http://www.youtube.com/watch?v=NLa0eMYc ... ature=plcp

[ampmike]

Wow,Nice work,Got to put that build on my list.Really nice!!!!!!!!!!Mikey
Thanks for the clip!Real cool.

[Colossal]

Two words!

Bad. Ass.

Well done! Another great amp roars to life.

[xtian]

Hey, Bear! Been watching your posts at thegearpage. Glad you're a member here. Keep it up!

[Structo]

Cool build!

Sounds like you really had it cranked!

That Splawn really sounded great too!

[fusionbear]

Thanks for the kind words. I have learned a lot from this forum. I experimented on this amp more than I ever have before I finalized it. I played with the B+ string voltages to hear what that would do, added bypass caps, removed them, played with the values. It is very fun. In the end I realized that I liked the tone almost stock with just a couple of minor changes. I really like the fact that it has the "authority" of the 2203 but not quite as ear blistering. Don't get me wrong, this amp is still really loud... I love that it is the size of an Express. I can't wait to take it over to some friend's house this weekend and see his expression when I crank it....

[fusionbear]

I made a few more adjustments to the amp. To be safe, I switched the 1.2K screen resistors on the KT88's to 5K. The voltages were just a bit too close to the 600v max on the screens. The amp still has a ton of headroom, but I think the KT88's will be happier in the long run. Also I switched the bright cap down to 750pf. This gives me less raspiness when I turn the gain down. I was going to sell this amp, but it sounds too good...

Update: 3:12pm Saturday

Messed around a little more this afternoon. Changed the circuit again. Changed bright cap to 390pf (maybe I just don't like the bright cap, LOL...). Also removed the 470/470pf from the first stage to the gain knob and replaced it with a 75k resistor. Changed the 470/470pf in the next stage to 340/470pf. I'll play with this a while. I'm having fun...

[fusionbear]

Some finalizations, I hope...

Went back to the stock treble peak circuit in first stage: 470k/500pf

Only deviations from stock:
1. V1b cathode resistor was 10k, now 5.6k
2. Second Treble peak stage was 470k/500pf, now 340k/500pf
3. Bright cap was 1000pf, now 750pf
4. KT88's instead of EL34's running at 560v with a 5K screen grid resistors.

Everything else is the bone stock circuit.

Here she is:

[IMG:640:480]http://i169.photobucket.com/albums/u223 ... G_1031.jpg[/img]

[fusionbear]

Final clip:

http://www.youtube.com/watch?v=JDl6OWm7 ... ature=plcp

Schematic:

[IMG791]http://i169.photobucket.com/albums/u223 ... titled.jpg[/img]

[fusionbear]

A little dress up. What do you think?

[IMG:640:480]http://i169.photobucket.com/albums/u223 ... G_1072.jpg[/img]

[xtian]

"shall"

It certainly begs the rest of the phrase…

"I shall F you up! A one, two, three, four--"