BFA Amp DIYTube

[sniper]

http://www.diytube.com/phpBB2/viewtopic.php?t=4353&start=15

Here is a little diddy  that a friend of mine Don Huebert built about three years ago and it has been the house bass amp for a club in Canada for the past three years. He finally got around to making a schematic to reflect the updates over the past few years. It handles about everything from Piezio's on up and has gone down only twice (minor stuff) since being installed. Bear in mind that it gets a workout with any band that plays there so its got a very good track record. Thought I would pass it on for anyone here that has an itchy soldering iron using cheap Hammond iron.

It RMS's about 160 watts with KT88's and a very simple preamp. Don has published these schemo's online and says anyone is welcome to them. It pushes an 8x10 cab 4 to 5 nights a week and doubles as a stage heater in Northern Canada. The PT runs a little warm but the OT stays really cool without a chassis fan.

[jumbodbassman]

i so wish i could read a schematic as i would love to build something like that

[Rob]

200S ?

[sniper]

Rob,

It is probably more like a single channel 2000S. The front section is very close to a Bauxandal pre amp being designed for a 12AU7 tube originally and the differential driver layout is close also. This amp doubles as the PA system in the club and plays upright bass mic pups as well. Don says it is very quiet and clean but very heavy. I know the iron in it is heavy as I have an exact set here at the house. This design has prompted me to start studying electronic symbols. I am of the opinion that the simpler the better when it comes to amp design. I'll post a 2000S schemo in a moment.



It should read at 150% sized up. I am also of the opinion the Sunns and Hi Watts are similiar (some anyways).

[Rob]

Thanks for posting this.  Sure looks similar.
I agree about the simplicity as long as they cascade properly. . . haven't had a tube head for years though.

[Psycho Bass Guy]

i so wish i could read a schematic as i would love to build something like that

You'd need the voltages and transformer specs to really do anything with that schematic. As an aside, the PT looks like a Marshall clone and the OT looks like the OT on a Sunn 2000S. I would expect a beefier PT could up the power and run cooler. Still, it works- nice looking booger.

[the mojo hobo]

The transformer part numbers are specified on the schematic and the specs are available on Hammond's web site.

Hammond 16540 T: http://www.hammondmfg.com/1608.htm

Hammond 278CX: http://www.hammondmfg.com/263.htm

[Psycho Bass Guy]

The transformer part numbers are specified on the schematic and the specs are available on Hammond's web site.

Hammond 16540 T: http://www.hammondmfg.com/1608.htm

Hammond 278CX: http://www.hammondmfg.com/263.htm

I didn't realize those numbers were Hammond parts ID's. Hammond is good iron, and those models are pretty much exactly how I described them. Based on that, I'm guessing a plate voltage on the 600 range and screens running a little more than half that. It's a nice amp.

If you wanted more power in that amp, you'd have to step up to a bigger PT than Hammond offers, probably go for Heyboer or wind your own. Hammond's only larger stock OT is their SVT copy. The OT from that amp is pretty much the equivalent of the lower powered Sunn 2000S' output trannies, which was rumored to ironically have been emergency re-sourced from Dynaco after Sunn unexpectedly sold out of all their parts for the first run of 2000S amps. There are two versions of that amp, but it's only the transformers that differ, so there are no schematic revisions or official acknowledgements of differing performance of which I am aware, but an early 2000S is good for about 30% more power than the later versions.

[sniper]

"Posted: Mon Jan 30, 2012 3:26 pm    Post subject:   

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Uhhh... Let's see, B+ is 535 volts, I remember that. What the rest are, I don't know.

Don"

Initially B+ come in about 600 but settles down to 535

[Psycho Bass Guy]

In general, the voltage drop on the B+ line is a good indicator of how hard the PT is working. Since you mentioned the PT runs a little warm, I'm not surprised that it's that relatively low on a PT with a 700v rating.