DIY F2 clone

[Dennis Hui]

I just finished putting an F2J together. I used a modushop 3U/400 steel chassis. The transformer is an Antek AS-3218 and the bias current is about 2.7A per channel. Part subs were minimal (BC560C instead of ZTX550, R6=10k). I did not test the jfets before hand for gate leakage so I kept R6 relatively low. The trimmers for the channels were adjusted to minimize distortion at about 4W output into 8 ohms @1K Hz.

The PCBs were a generous gift from Twitchie.

Thank you Papa for sharing this design with us Greedy Boyz.

 

[chromenuts]

I’m surprised how much F2J love we’ve been seeing lately!

Enjoy!

 

[andynor]

I just finished putting an F2J together. I used a modushop 3U/400 steel chassis. The transformer is an Antek AS-3218 and the bias current is about 2.7A per channel. Part subs were minimal (BC560C instead of ZTX550, R6=10k). I did not test the jfets before hand for gate leakage so I kept R6 relatively low. The trimmers for the channels were adjusted to minimize distortion at about 4W output into 8 ohms @1K Hz.

The PCBs were a generous gift from Twitchie.

Thank you Papa for sharing this design with us Greedy Boyz.

Lovely!! How does it sound??

 

[Dennis Hui]

I've only tried it with test speakers since I finished the amp adjustments earlier today. I'll probably hook them up to the Zu's later today.

 

[andynor]

I've only tried it with test speakers since I finished the amp adjustments earlier today. I'll probably hook them up to the Zu's later today.

Lookig forward to your impressions

 

[Zen Mod]

F2J is for weaklingsesssss

 

[andynor]

F2J is for weaklingsesssss

Of course. We are self proclaimed god damn sissienezzezzzzzzzz.

 

[chromenuts]

Everyone else is just insecure…always having to strut around waving all their watts in the air 😉

 

[andynor]

Everyone else is just insecure…always having to strut around waving all their watts in the air 😉

My neighbour thought it wass a 200 watt amp at first listen…

 

[twitchie]

Looks great Dennis! Hope you find it to your liking!

Cheers,
Stephen

 

[BRN]

The F2J has been my favorite with my full range speakers.

 

[andynor]

I've only tried it with test speakers since I finished the amp adjustments earlier today. I'll probably hook them up to the Zu's later today.

No premature release I gather

 

[andynor]

 

[nicoch58]

frugly

 

[Zen Mod]

 

[ripson]

Hello guys, changing the subject: I am thinking about experimenting by adding some ribbon tweeters on top of my full rangers, so a new two channels of F2 (kind of) would be nice, but I do not want to burn another 130W or so... so I was wondering about lowering the current, using some "smaller" MOSFETs, much much smaller output caps (so they could form a HP filter with the tweeter impedance), smaller radiators Has anyone done something like that before?

EDIT: and because it's a current source amp using the same amp with the ribbon... not sure if Mr. Kirchhoff would be on my side...

 

[Zen Mod]

why separate amp for tweet helpers?

isn't approx. 1uF in series , connected in parallel with FR, just enough?

of course, if you feel as building another small amp, I have no objection

 

[ripson]

why separate amp for tweet helpers?

isn't approx. 1uF in series , connected in parallel with FR, just enough?

of course, if you feel as building another small amp, I have no objection

Hi ZM, with the voltage amp... no issue, but with CS I am stealing the current from the FR, and that's where my doubts are coming from.

 

[TroutBear]

Dennis - On your 3U/400 steel chassis - how's the thermal performance on those heat sinks? It's certainly not apples to, but I'm in progress of collecting parts for an F6 and would like to consider the 3U/400 instead of a 4U chassis. Thanks

 

[Zen Mod]

Hi ZM, with the voltage amp... no issue, but with CS I am stealing the current from the FR, and that's where my doubts are coming from.

dunno, you're stealing current from it where it is already doing squat