NelsonVandal
1000+ Head-Fier
- Joined
- Aug 27, 2006
- Posts
- 1,023
- Likes
- 11
I've had my stripboard portable JISBOS for a while, modding it back and forth. From 3 ch JISBOS to 2 ch passive ground to 3 ch with opamp ground etc. I'm sorry I cut the board and removed the ground channel. The sound has been good all the time though, but it was best with JISBOS in all 3 ch. I fooled myself to believe that using the center point of the batteries was better for ground. The sound was more impressive and a bit "expanded stereo" but got tiresome in the long run.
My point is: first I made it to the spec's in the first schematic HeadWize: DIY Workshop > discrete buffer: jisbos (air wired), and I found that 12V supply was a minimum to get a good sound and if I added gain there was distrortion. Since amb lowered the bias to the input stage HeadWize: View Post [DIY Workshop > discrete buffer: jisbos (air wired)], the voltage swing seems to have improved and now I've finally added gain to it again. And it's playing loud and good. The gain is set with a 3.3k in the feedback loop and 1k from this to ground, not sure what the gain is exactly. Since I was stupid enough to cut the board and remove the ground channel I use this virtual ground circuit suggested by Nico Ras at Diyaudio.com for one of my other projects.
The amp is housed in a Hammond C1201 with 10 AAA's. I have the bias set to about 25 mA, so I still have a good run-time. It sounds very good. It has that "soul" opamp based amps are lacking. If it colors the sound, it's a bit warmer/fatter. It brings back this hobby to what it's all about - enjoying music.
I'm in the middle of making a BISBOS (all bipolar amp) - a combination of JISBOS and Hiragas le Classe A, with the help from Nico Ras. I'm still awaiting the parts (and time) to complete it, but I have one channel running. It's designed for 9V supply (8 AAA's) to make it portable. I'm planning on using a little bigger box this time, a Hammond J1201, so it will be easier to tweak and look nicer. Nick is laying out a nice PCB.
People here has always been saying it's impossible to make class A discrete portable amps, but I'm doing my best to prove you're wrong so I can step out of the opamp swamp
.
There's another a guy at Headwize.com, who has been making a battery powered JISBOS as well. The wheels are turning.
HeadWize: DIY Workshop > Little discrete portable amp (a bit less stupid than first time
)
My point is: first I made it to the spec's in the first schematic HeadWize: DIY Workshop > discrete buffer: jisbos (air wired), and I found that 12V supply was a minimum to get a good sound and if I added gain there was distrortion. Since amb lowered the bias to the input stage HeadWize: View Post [DIY Workshop > discrete buffer: jisbos (air wired)], the voltage swing seems to have improved and now I've finally added gain to it again. And it's playing loud and good. The gain is set with a 3.3k in the feedback loop and 1k from this to ground, not sure what the gain is exactly. Since I was stupid enough to cut the board and remove the ground channel I use this virtual ground circuit suggested by Nico Ras at Diyaudio.com for one of my other projects.
The amp is housed in a Hammond C1201 with 10 AAA's. I have the bias set to about 25 mA, so I still have a good run-time. It sounds very good. It has that "soul" opamp based amps are lacking. If it colors the sound, it's a bit warmer/fatter. It brings back this hobby to what it's all about - enjoying music.
I'm in the middle of making a BISBOS (all bipolar amp) - a combination of JISBOS and Hiragas le Classe A, with the help from Nico Ras. I'm still awaiting the parts (and time) to complete it, but I have one channel running. It's designed for 9V supply (8 AAA's) to make it portable. I'm planning on using a little bigger box this time, a Hammond J1201, so it will be easier to tweak and look nicer. Nick is laying out a nice PCB.
People here has always been saying it's impossible to make class A discrete portable amps, but I'm doing my best to prove you're wrong so I can step out of the opamp swamp
There's another a guy at Headwize.com, who has been making a battery powered JISBOS as well. The wheels are turning.
HeadWize: DIY Workshop > Little discrete portable amp (a bit less stupid than first time
)
