Tweet
Short story:
Here is the schematic: http://pepeamps.com.br/conteudo/wp-c.../pepe_fk40.pdf
Here is a not-so-technical text where I talk about the circuit: The FK-40 Circuit | Pepe Tube Amplifiers
And here's a video where you can hear the functioning circuit : Haroldinho Mattos apresenta o HCA on Vimeo (My customer calls the amp HCA.)
Note: The fuses aren't shown, my mistake. There's a fuse for each secondary winding on the power transformer: 6 Amps sloblo for the power tube heaters, 500 mA for the HT, 100 mA for the bias, 1 amp sloblo for the preamp tube heaters(12v). Mains fuse 2 A @ 220 VAC.
----
So, the long story.
Earlier today I was chatting with fellow forum members about open projects and licensing our work through a protective yet permissive license such as Creative Commons Attribution. I believe in openness because it speeds up progress. Someone from Russia can use a project from the USA, improve upon it and release it once more to the public for further development, all this while hopefully everyone is able to make money from the project so it's not free as in beer, but free as in freedom.
I would love to see this become a tradition on the guitar world as well, instead of closing everything with patents and dripping black gook over components, why not license it openly and then require a citation if someone uses it?
So, in that spirit, I'd like to share with you a circuit I've been tweaking for some time now. Here included are links to a reference build using this circuit, to show the result in practice. I don't even know if this is relevant enough to warrant its own thread, I'm just sticking my head out there, hoping this is OK to do.
In May this year I developed this preamp circuit, I called it FK-40 because it was my fourth attempt at a two knob amplifier, so Two Knob TK-40 became Fourth Two Knob 40, or FK-40, which ended up having three knobs because I added a master volume. So much for my marketing talent.
Basically the initial idea behind this circuit was to digest the entire tone stack into one control. Then on its current incarnation I implemented an old idea, to reduce low frequency response as the gain was increased, so you can get clear power chords even with high gain and full body cleans with low gain - in a single channel amp, using a single knob for that as well.
The video above has some of that demonstrated, I think the idea works but may be improved upon, you can hear it get less bassy as the gain is dialed up. If you dial up both tone and gain, you get a very British distortion sound, if you have tone at max and gain at 40% you get a Texas Special tone. If you roll back both to around 40% you get a nice clean tone.
Don't mind the cookbook recipe for the output stage.
I used quality components to be sure any eventual mistakes were not the result of low quality material. The three of these amplifiers(four actually, one was a prototype) that I built were purchased from me by a friend here in town, the face design, logo, etc, belongs to him now along with the three amplifiers. But you can build this circuit in any style you like, I'd just like to disclaim ownership of that brand and looks, I don't own that.
A wonderful guitar player, luthier and friend Haroldo Mattos was kind enough to record that video for the amplifier. I can't thank him enough for all his help and feedback he gave me about that circuit. He speaks in Portuguese so if you'd like to skip the talk there are sound clips from 0:00 to 0:30, some more playing at 0:53, 2:00 minutes, 3:02 minutes, 3:15 and only short clips from then on.
Your criticism and ideas, both about licensing circuits via Creative Commons and about this example circuit, are welcome and very much appreciated.
Here is the schematic: http://pepeamps.com.br/conteudo/wp-c.../pepe_fk40.pdf
Here is a not-so-technical text where I talk about the circuit: The FK-40 Circuit | Pepe Tube Amplifiers
And here's a video where you can hear the functioning circuit : Haroldinho Mattos apresenta o HCA on Vimeo (My customer calls the amp HCA.)
Note: The fuses aren't shown, my mistake. There's a fuse for each secondary winding on the power transformer: 6 Amps sloblo for the power tube heaters, 500 mA for the HT, 100 mA for the bias, 1 amp sloblo for the preamp tube heaters(12v). Mains fuse 2 A @ 220 VAC.
----
So, the long story.
Earlier today I was chatting with fellow forum members about open projects and licensing our work through a protective yet permissive license such as Creative Commons Attribution. I believe in openness because it speeds up progress. Someone from Russia can use a project from the USA, improve upon it and release it once more to the public for further development, all this while hopefully everyone is able to make money from the project so it's not free as in beer, but free as in freedom.
I would love to see this become a tradition on the guitar world as well, instead of closing everything with patents and dripping black gook over components, why not license it openly and then require a citation if someone uses it?
So, in that spirit, I'd like to share with you a circuit I've been tweaking for some time now. Here included are links to a reference build using this circuit, to show the result in practice. I don't even know if this is relevant enough to warrant its own thread, I'm just sticking my head out there, hoping this is OK to do.
In May this year I developed this preamp circuit, I called it FK-40 because it was my fourth attempt at a two knob amplifier, so Two Knob TK-40 became Fourth Two Knob 40, or FK-40, which ended up having three knobs because I added a master volume. So much for my marketing talent.
Basically the initial idea behind this circuit was to digest the entire tone stack into one control. Then on its current incarnation I implemented an old idea, to reduce low frequency response as the gain was increased, so you can get clear power chords even with high gain and full body cleans with low gain - in a single channel amp, using a single knob for that as well.
The video above has some of that demonstrated, I think the idea works but may be improved upon, you can hear it get less bassy as the gain is dialed up. If you dial up both tone and gain, you get a very British distortion sound, if you have tone at max and gain at 40% you get a Texas Special tone. If you roll back both to around 40% you get a nice clean tone.
Don't mind the cookbook recipe for the output stage.
I used quality components to be sure any eventual mistakes were not the result of low quality material. The three of these amplifiers(four actually, one was a prototype) that I built were purchased from me by a friend here in town, the face design, logo, etc, belongs to him now along with the three amplifiers. But you can build this circuit in any style you like, I'd just like to disclaim ownership of that brand and looks, I don't own that.
A wonderful guitar player, luthier and friend Haroldo Mattos was kind enough to record that video for the amplifier. I can't thank him enough for all his help and feedback he gave me about that circuit. He speaks in Portuguese so if you'd like to skip the talk there are sound clips from 0:00 to 0:30, some more playing at 0:53, 2:00 minutes, 3:02 minutes, 3:15 and only short clips from then on.
Your criticism and ideas, both about licensing circuits via Creative Commons and about this example circuit, are welcome and very much appreciated.
), Gibsonman63. I was really aiming for simplicity on that circuit.
Comment