New BFPR build..and Thank You!!

[Deric]

So I started lurking here a year ago or so.  Had already built several "D" style amps, various "18 Watters" and a couple o' Voxy things....but this place gave me the bug for a Princeton.  Finally found time to get it done.

Nothing really new here.  Mojo PR chassis, transformers and cab.  Had the baffle cut for a 12" speaker.  Used a Hellatone 30 'cause it was the only speaker I had lying around - sounds very nice!!  Added adjustable bias, a bias test point on the back panel, variable negative feedback (25k pot in line with the stock 2k7 mounted in the extension speaker hole),  25k pot in place of the "mid" resistor, selectable bypass caps for V1a via a toggle on the back panel ( 25u or 5u ).  Used Sozo "Blue" caps - sound good but have nothing to compare to..... 

Sounds Bad Ass!!!     So far, I LOVE everything about it - except the 'verb.  Never been a big fan of spring reverb.  I get that it's the "Bomb" for the surf-thing but that's not my bag.   With some help from the guys at Ampgarage I tried a few different things.  I've lowered the 3m3 resistor to 2m2.  Didn't help the reverb that much but did change the gain in a good way.  Tried a 12au7 for the driver and it helped but made the 'verb very dark.  I prefer the brightness of the 12ax7.  Put 100k resistor across the reverb pot which made the control much more usable - less touchy.  May try a 50k audio taper pot....   It sounds good but the decay is too long.  Going to leave it as is for now but will order another tank with a shorter decay...

Just finished this up Friday.  Luckily got snowed in today so I spent the day adding the neg feedback control and the switchable bypass caps as well as messing with the reverb.  Put it all back in the cab around noon and having been playing it non-stop (well almost non-stop) ever since.

What a cool amp.  Maybe it's just new but this may be the coolest amp I've ever played!!!   Been playing loud, quiet, with and without pedals.  Sounds great with my ZenDrive clone which I've never really used before...  Also fired up a Keeley comp.  Killer clean country-ish stuff..

Now I just gotta learn to play!!!!!!!!!!!!!!!!!!!!!

Big thanks to everyone here for the inspiration!!!!

[drumslinger2000]

Nice job on the build Deric!! 

[TubeGeek]

Nice build

Thanks for sharing.

[Fresh_Start]

Thanks for sharing the pics & tweaks. 

Did you change anything in the tone stack or coupling caps?

Chip

[sluckey]

Very nice. Welcome to the Fender side. Is your bias test point monitoring the negative bias voltage sent to the grids?

[Deric]

Tone stack and coupling caps are all stock values.  Only changes are listed above...

The bias jack is for checking cathode current via a 1r resistor.

Played this thing for at least 4 hours last night.  Time for some more!  

Edit:  It does have 1k5 grid resistors and 1k screen resistors on the power tubes.  Planned on using 470r for the screens but didn't have any.  Sounds fine the way it is.  Planned on changing them when I get some 470r but after reading the recent threads here about screen resistors I'll probably just leave them.  Also using 40u/20u/20u/20u cap can.

[zendragon63]

Neat as a pin Deric. Nice work! Regards

dennis

[Deric]

Faceplate's on and all buttoned up.  Swapped the reverb tank for a 9AB2C1B.  Much better.  No more "boing".  Swapped the 5u on the switch for V1a to a 1u.  Works great for tightening things up when cranked.

Everything else as posted above.

Thanks to the forum for inspiring this build and all the BFPR info posted here.  This one's a keeper!!

Faceplate from Amplates.com

[drumslinger2000]

very neat work Deric.  amp looks great!!  congrats on the build man!