diytube.com

159M: 15H 100mA 256ohms 500V

The 100mA (as opposed to the 150mA of the 157Q) looks okay for the B+ of the pre and phase splitter tubes, but will I need to adjust the value of the Caps of the PI filter in which the choke is used?

About those filter caps in the PS, particularly int he Pi philter...what voltage rating should they be?

No, you don't have to adjust any capacitor values for the different choke.

The power supply makes almost 600 volts during warm up and then settles to ~535 volts, so any caps you use must be able to handle at least 600 volts. All the caps are 450 volts, in series the way they are, that gives them 900 volt rating.

I am about to start building another one and will arrange the filter caps very differently. I will keep everyone posted as to what I decide. The rule here is: more is more.

Don

dhuebert wrote:I am about to start building another one and will arrange the filter caps very differently.

Are you going to keep the 6SL7 PI? Have you had problems with microphonic 6SL7s in this amp?

Jim

Have you had problems with microphonic 6SL7s in this amp?

No. It sits atop an Ampeg 8x10 and has been running reliably since May. It is the house amp at:

http://www.highandlonesomeclub.ca/

It runs from ~10:30 PM till 2:30 AM Thursday thru Sunday every week, sometimes at full throttle. With every manner of bass and player. It's pretty satisfying to feel it thru the floor at the back of the room. I'll try and post some pictures.

Don

Don,
This is fantastic - just what I was looking for !

-Steve

Don,

Here may be an alternative to a stand-by switch.

http://www.sophiaelectric.com/pages/parts/delay_action_board.htm

Scott

Here are some snaps of the BFA in it's natural setting:





Don

A club environment is about the best long-term "life test" for any amp...
looks good!

/ed B in NH

That's convenient... without a protective screen on the front of the amp the bassist can keep his/her coffee hot for the whole night...



Chris

You don't notice it so much in the winter... but in summer the heat radiates off the amp in a way that is truly uncomfortable for the bassist. As I have said before it has been in service continuously since May of 07 and has yet to suffer a single failure. I am not trying to brag here, I am as amazed as anybody. I have had a few failures with other amps, most recently when one of the 6L6s melted itself on one of my eiclones. I have spare tubes handy for the BFA and am just waiting for the call.

Don

I am sure that the BFA is betterbuilt than were most commercially produced amps... It always helps to have extra margin designed into the circuit...

/ed B in NH

I've been reviewing this thread and have to say the BFA finally suffered a failure. It was a tough one to trace and a real learning experience. I had sized the voltage dropping resistor for the preamp power supply too small wattage-wise and it was running VERY hot. It melted the core of a piece of coax that was nearby shorting the signal to ground. The outside of the cable looked just fine so it took a fair amount of tracing to find the short. I installed a larger resistor and rerouted the coax and it's been fine since.

Don

Hi Don,

Hooray! My second post on this forum already! I am making progress. (Why on earth has it taken me so long to discover this place...?)

As both a bass player and valve equipment tinkerer, I've been really enjoying this thread. The BFA is a lovely looking piece of kit, and the fact that it's been working happily, night in, night out in a club environment is a testament to the quality of design and construction that has gone into it. I particularly like the 6SL7 phase-splitter.

What are we looking at power-wise, here? I'd gues around 220-250W, yes?


Finally, one thought...

I notice you mentioned that heat output/cooling is a potential worry in the warmer months. You could always move the handle(s) to the ends of the case and make a big, square mesh-covered hole in the top, over the output valves. There's nothing like old-fashioned 'chimney effect' convection for allowing those big bottles to cool themselves at their own best rate. Also, if you deliberately made the top of the case slanted or even domed, you could completely discourage the tendency for musicians to put their pint down on top of the amp! Yellow_Light_Colorz_PDT_07

It makes in the neighborhood of 160 watts (156 watts RMS into a 5 ohm wire wound resistor load). Since it's winter here 11 months a year, I don't really worry about cooling.

Don

I hear that in Winterpeg, there are 11 months of winter, and one month of bad sledding Yellow_Light_Colorz_PDT_08 Yellow_Light_Colorz_PDT_04 :o

Stay warm (more big tube amps, please)

/ed B

Great looking build .
Hi , my name is Cam , I am from Calgary , Alberta and I love to build amps . I am currently employed in the oil & gas industry as a Power Generation Project manager . I have afairly extensive background in controls , instrumentation and natural gas and diesel fired engines . I have played guitar for 30+ years ( yea ,i`m pretty grey) sorta gave it up to raise a family and have returned playing in recent years . I tried several different amplifiers but could not find the sound I like . Back in the 70`s , I used a Verlage 100watt with 4-6L6`s . Built in Humbolt Saskatchewan by Ken Verlage . Best sounding amp I ever owned , but good god it was too loud for what I need now .
I decided to build my own and with a lot of research I picked the Trainwreck Rocket - cathode bias 4 -EL84 . Turned out fantastic , so I built a Liverpool and then a 2 hole Rocket . Now I am definitly hooked . I want to build the BFA and have started to accumulate the parts needed . I would like to know what size chassis was used for the BFA , It looks a little small , I`m thinking 17 x 3 x 10 ?? any help here would be really great
Fantastic site with loads of helpful info , Thanx guys

Camster