Sorry for this post but....

[Manic]

I cant find a particular post that Im very interested in. I have searched and searched, for the life of Me I cant find it.

Details about the post are that someone purchased an SF amp of some sort that had the fixed/resistor bias setup. He also stated that the guy was desperate for money and that the purchaser of said amp found bags for dope in the amp. ie. crack, meth or coke. The purchaser of the amp posted pix of the said bags on another site. Another member here stated in a follow up post that the dope bags may indicate why he was in financial trouble.

Another member stated that a bias like that sounds fixed at lower volumes and sounds like a cathode bias at higher volumes.

And yet another member stated that it might be better left alone to preserve the history of the change over period from BF/SF.

Now im 90% sure it was here, but there is the off chance it was in another forum.

Im terribly interested in following this post because I to recently purchased a similar SF amp with the same bias setup. Mine is a SF Band Master.

Sorry for any inconvenience and any help would be most appreciated.

[stokes]

I do remember that thread,but cant say for sure but I think it was this forum.Dont know what category it may have been.I did some work on a SF Bassman that had the bias scheme you talk of.It looked interesting enough that I installed a similar bias set-up in a higher powered Champ type amp I built with a 6L6GC power tube and heftier trannies and I like it a lot.I dont remember exactly the value I settled on,but I tried different values for the cathode resistor.I think I ended up with about 100ohms or so.It does give you a nice mix,more fixed at low to moderate levels and the cathode bias tone really kicks in when cranked,but it still retains enough of the tighter fixed bias response when pushed.The SF Bassman didnt seem as noticeable with the stock resistor.This SF Bassman seemed to be one of the "transitional" amps.Had some BF circuitry.I was not able to find a schematic that showed that bias set-up,but it definately appeared to be stock.

[chocopower]

mmm.... are you talking about this?:

http://www.el34world.com/charts/pt_conversions.htm

[Manic]

mmm.... are you talking about this?:

Thnx for the effort. It wasn't that post, but that sure looks like the circuit. That may come in very handy. I might want to run a BF fixed bias at some point.

Stokes, thats cool that You like the sound of that bias setup. I tried the amp but one of the original GE 6l6's rattles, so I shut er down. The short time I did play the amp I thought it was super warm. I was diggin it. Possibly to warm, but friendly to the ear at the same time. I wonder if I can remove the nasty sparkle robbing caps with out changing the general bias setup. I like cathode biased amps too.

The JBL D120f's that came in the cab are working but crack under high volumes. I moved them into the double deluxe I built. Its a shame they arent up to snuff. They sure are zingy!

Still I feel it was a good deal for both amp and cab bone stock for $350.

I'll go ahead and post a couple few pix on this thread for now, until I can figure out where that other thread is.

[stokes]

I didnt like it in the Bassman.I liked it in the Champ type clone I made.That schem that chocopower posted doesnt look quite the same as the Bassman I saw.If you look at it closely you will see his shows pin 8 of the tube on the right grounded,that would defeat the purpose of the 150ohm res on that pin.I dont think mine had the cap from pin 8 to pin 8 either,but it has been a long time.The Bassman I worked on,the owner wanted a BF mod,but it turned out that being one of the "transitional" models it had the BF circuit already,except for the two resistors on the cathodes along with the true bias adjust as opposed to the bias balance.

[Manic]

I'll take a close look at that Stokes, thnx man.

I was browsing Regis's site http://www.regiscoyne.com/Blackface_Bandmaster/ checkin out his gear and He has some nice pics of His 65' Band Masters innards. I was pleased to see that My SF Band Master closely resembled His BF. I'm really lookin forward to puttin it to it at a show.