tunghaichuan
September 18th, 2008, 07:12 AM
The Brown Note 18W Lite IIB amp that I'm building and documenting in this thread (http://www.thefret.net/showthread.php?t=8502) is not the first 18 watt amp I've built. The first 18 watt project I built is detailed here:
http://www.diycustomamps.com/ef86_18w.htm
A couple of new pix showing the "updated" front panel:
http://www.diycustomamps.com/images/18w/ef86_18W4.jpg
http://www.diycustomamps.com/images/18w/ef86_18W5.jpg
This amp is not really an 18 watter, it is actually more like a simplified version of the Vox AC-15 with the pentode preamp tube and cut control. I hadn't played it in a while and after pulling it out and playing it a bit yesterday, I was surprised to hear how good it sounds. Very fat and chimey. It takes pedals very well.
The output transformer in that amp is very special: it was a NOS Bedrock Amps OT made to run in near Class A operation. It is a 20 watt unit. The power transformer is a Custom Coil unit. I'm using another just like it in the Brown Note 18W project.
On downside of this amp is that the preamp tube, a 6267 (industrial EF86), is microphonic. So cranking it up all the way only induces squeal. I can't use a clean booster to drive the front end either :( I'd like to try a few modern EF86 tubes, but these are pricey and there are no guaranties that they will not be microphonic as well.
The face and back plates are made of laminated paper. They look okay but are kind of cheesy. I plan on sending out the CorelDraw files to BNP Lasers to have proper plastic or metal plates made for the amp. I don't like the black writing on the white background so I think I'm going to go with a black face plate with white writing.
One thing that concerns me about this amp is the the a 6CA4/EZ81 tube rectifier shares the filament winding with the EL84s, 12AX7 and 6267/EF86. If the recto ever shorts, it will take out the tubes and the OT. I may pull the socket and put in an octal socket so I can run a 5Y3 or 5V4 off of the 5V winding on the PT.
The amp really needs a cabinet and I really need to acquire some woodworking skills :D
A very worthwhile project, and very Voxy tones out of it. With the right pedals, it will do a Marshall impersonation as well.
tung
http://www.diycustomamps.com/ef86_18w.htm
A couple of new pix showing the "updated" front panel:
http://www.diycustomamps.com/images/18w/ef86_18W4.jpg
http://www.diycustomamps.com/images/18w/ef86_18W5.jpg
This amp is not really an 18 watter, it is actually more like a simplified version of the Vox AC-15 with the pentode preamp tube and cut control. I hadn't played it in a while and after pulling it out and playing it a bit yesterday, I was surprised to hear how good it sounds. Very fat and chimey. It takes pedals very well.
The output transformer in that amp is very special: it was a NOS Bedrock Amps OT made to run in near Class A operation. It is a 20 watt unit. The power transformer is a Custom Coil unit. I'm using another just like it in the Brown Note 18W project.
On downside of this amp is that the preamp tube, a 6267 (industrial EF86), is microphonic. So cranking it up all the way only induces squeal. I can't use a clean booster to drive the front end either :( I'd like to try a few modern EF86 tubes, but these are pricey and there are no guaranties that they will not be microphonic as well.
The face and back plates are made of laminated paper. They look okay but are kind of cheesy. I plan on sending out the CorelDraw files to BNP Lasers to have proper plastic or metal plates made for the amp. I don't like the black writing on the white background so I think I'm going to go with a black face plate with white writing.
One thing that concerns me about this amp is the the a 6CA4/EZ81 tube rectifier shares the filament winding with the EL84s, 12AX7 and 6267/EF86. If the recto ever shorts, it will take out the tubes and the OT. I may pull the socket and put in an octal socket so I can run a 5Y3 or 5V4 off of the 5V winding on the PT.
The amp really needs a cabinet and I really need to acquire some woodworking skills :D
A very worthwhile project, and very Voxy tones out of it. With the right pedals, it will do a Marshall impersonation as well.
tung