Tea-Bag

Got it!!

nope - that will increase negative offset what I said is " increase R26 for 220R" This still doesn't make sense to me. You mean R25 to 220R (max for it)?? My thinking tells me to use 1K instead of 680R, should get more wiggle room with R25 pot. 680R improved over 470R, which was improved over 390R original. OR I should try to swap R25 to 1K pot. This makes sense to me.... More resistance here has been dropping the offset, but not enough room to get near 0v.

These are simple things So I am at 680R for R26, and best offset so far is achieved with R25 at max, R12 at min. Are you suggesting I try 220R for R26? Sorry if I am coming across as dumbass. (true nature)

I lowered R25 pot, to 0, offset is -.760, turning higher lowers it down a bit to ~.5 to ~.4v.I checked R35, it is 220R.Before swap out of power resistors, both pots were near minimum.

No, it only went more negative on offset.

I am not sleeping! Working on this stuff like a good diy soldier.I tried R26 at 470R, brought down to -.500mv, then 680R, no down to four.So, try 500R or 1K pot for R25, or lower R35 to 100R?CNY pin 1 to 2 of DVM is 1.1vIt's like ZM says, R25 on max, R12 on min. Now Bias is higher, .640mv.

Well, Good Morning guys.I swapped some of the power resistors to Sp300's standards.So ~ .33, .66, .33 - using 1R/.5r 2R/1R, 1R/.5rBias sets around .562v across Upper and Lower, Middle set at 1.1, problem is offset is now -.640v, and wants to go in the direction of down, so I have no room on R12,25 (at min), so it looks like I got to lower R26 (390), R35 (220).Should I start by going half value on each?Other problem is CNY17 in both channels is 1.0v, so this seems to be another problem. Previous measurements were at 1.3v, no problem. So looks like I need to change something here. I assume R28 (200R) needs to be lowered or raised. So just putting this out here looking for encouraging ideas. I assume R28 would be better at 150R.Tea

Excellent, so leave bottom Q14 Sources alone?

Guys,I got lost on the upper lower source resistor thing, is that idea beaten down by offset problems?

I was talking about the BJ2. The F2J sounds a little 'cleaner and sweeter' on the top end, same with Mini-A with SemiSouth output.The BJ2 sounds a bit darker to me. So it doesn't have the 'house' SemiSouth sound I was expecting. I am of course wondering if mine is 'tuned' correctly. It certainly doesn't sound bad, just has a whiskey tone, not champagne.

Vlad has had opportinity to hear the FW J2 for longer periods than the two tracks that I heard with it. So dont take my opinion seriously at all. And I think the speakers there may have played a big part in it.Some other words to describe it. Organic, dark, dynamic (unexpected). The soundstage sounds a bit less precise than F5. More atmospheric and wider and deep soundstage than F5. It is not dry sounding. It sounds 'dirty' compared to F5 or F2J 'clean'More tone than F5, and tone is darker than F2J, and Aleph type with R100. I think Generg could make a comparison here with the latter as well.Keep in mind, I plan on using 100R gates, and adding in other LED or Diode into Vref to bring up Drain voltage on 2SJ's Changing the diode sounds easier. . This may change things for better or worse.

Listening to the BJ2......Also some 24/96/192k stuff.No vinyl today.

Generg, The BJ-2 sounds a lot like I remember the FW J2 sounding like at Burning Amp 2009. AR2 might be able to comment here. It appeared to have a little bit darker overtone than say my mini-A with R100 or the F2J, which to me sound a touch less dark and more of that clean upper mids and treble sound. Of course, I did not have much time to compare, it could be some component break-in that needs to go on. From the gate, it's a different sounding amp using SemiSouth's. Most of my future comparison will be from recent memory of tweaked out F5 clone, and then I can bring, Mini-AJ online to compare later.

The LED's are supposed to be 1.9v 20ma red one's. I believe I measured as such too. It does Vref a little low, around 10.5-11v.Latter I will add LED in to adjust to spec, change the gate resistors possibly.It's certainly reminiscent of the J2 at BAF09, and unlike the F2 and other SemiSouth contraptions with Aleph current source. Those devices have more upper mid - high clarity to it. More time will tell.

Finally got this boxed and starting to listen to it.Bias is .9v each side. One channel offset floats between .20mv and .70mv. The other is still near 0. Still need to play with it.There is a little 'buzz' you can hear up to 2feet away in both channels when the inputs are not shorted. Thinking I need to use some shielded wiring on input, but for now, just listening.You guys are more than welcome to comment on my primitive construction skills with aluminum sheets. :sarcastic_hand:The initial sound seems to have a mild velvet softness with no loss of detail, and control and quantity of the low end that I was not expecting.Gate resistors are 47RTomorrow I plan on letting it run all day, and turning off load stuff around the house for some serious listening.

thanks. I will stick with a CRC for now, and get some 4.7k resistors in route.

Okay dudes,Trying to get the ball rolling to get this boxed up. I don't have all the parts, so was thinking about how to do this.. So, if I get .6v across R23 - What's the benefit of going from 12k to 4.7k, is this a safer parameter, or a performance parameter? Tjat conversation was a bit lost on me. I was also thinking about a shunt Power Supply, supplying about 4A total I guess using a 22V transformer, or a traditional CRC like ZM used in his setup.

Well, The SemiSouth's don't seem to blow if you don't short them. That's been my problem on my channel 2 escapades. But hopefully troubles are settled.I've been using F5 without protection for a couple of years, and have been lucky I guess.I am looking into part substutes for this contraption you speak of.

off topic now..Looking at this.http://www.keith-snook.info/QUAD-405-2-Mods.htmlIt seems it wouldn't trigger until 8-10volts DC. That seems high to me.

Guys, I get a little cone exursion during power on/off (full power) with BJ2. Is this going to be a problem if using lowthers? If so, I can put a ground lift switch to the speakers. It does not 'thump'

I am able to bias it up to .910v no problem, and offset seems approachable.I am using BC560c - all I can seem to find @ digikey, I get around .61-62v there, okay, but 4.7k won't be big change.I put on the 13v protection diodes as well, mounted them on top. Have surgery next week (gall bladder gone ) hopefully I will be able to crap normally after that. :bathroom: So I don't think it will move into full system soon. Unless I get some duct tape and plywood like sp300. Which is a solid possibility.Still lots of work outside to do --- Snow is coming! Got all kinds of crap outside my house lying around, keeping up the white trash persona. Got to move it in to keep wife happy.

So after soldering out all transistors, replacing all new one's - using a brand name solder - swapped out all the caps - the second channel runs ! I have to blame Gerd for slapping me around off thread to get me moving on this.I suspect that the components were fine, just a marginal solder joint somewhere.With default resistors, 470R runs 9.4 , Source resistors run about .86v like channel one. offset is below .03v R12 and R25 like to run near 0R to keep offset the best. I will play with this more tommorow to bring the juice up if possible, although it did not seem to budge much after several turns.It looks sp300b has changed at least one of the 12k resistors to 4.7k. I also have to re-read a bit here as I believe swapping 220R resistors for 180R (I may have done that in other channel, it's been so long), may benefit bias procedure.Anyways, I am happy it's playing music. I will do my best to get it presentable in a chassis soon for some main speaker listening.

And PSM OB?

swapped out Q13 and Q14 for a better matching pair, and still no bias. Hmm.I think my next step is another analysis of continuity and cold resistance figures on both channels. If that provides nothing. I will overhaul the motorcycle.

Is this a question? I think your just telling me role of Q6. Not related to issue...