Thank you, Dirk! I will check out if my friend still can provide som aluminium sheets, and if so the plain 9» degree solution with holes on top should be an easy job. Btw, what are those series resistors you have stacked there for? Gain tweak?
^ Very well at least with a 4ohm (dips to 3 I think) pair. I did a 6 deep build with 24V rails to match well with those. I monkeyed around with various bias settings. I also used tightly matched MOSFETs and lowered the source resistors to 0R22.
I haven't measured the output impedance ... but I assume it's 'lower'.
I think you'll like it, but YMMV.
I haven't measured the output impedance ... but I assume it's 'lower'.
I think you'll like it, but YMMV.
Hello Andy,
i have built minimum 4 or 5 versions of the BA-3-frontend. That one on the pics was my 'testboard'.
I tested different transistors, different resistors in the outputstage (because of different Mosfets) and much more...
Greets from Dirk
I'm pretty sure I will be very pleased. I waited for this one. Would love to buy actual XA25, but this Babblefish version will do very nicely.
Nice description by one member here who has both. I'm getting close to finishing this one. Just finished, well, got playing at least, a new speaker build. Exciting together both done!
Russellc
Nice description by one member here who has both. I'm getting close to finishing this one. Just finished, well, got playing at least, a new speaker build. Exciting together both done!
Russellc
I have two BA3 front end preamps. Also have the BA3 amp, 3 pairs, 31 volt rails. Heatsinks are not that hot. It's been a while since checked/adjusted. Will see about upping the bias.
Russellc
In your chassis, and as long as it is placed in the open, 120 watts per sink with Kheratherm can work well. .645A and 0v645 drop over your 1R source resistors, can be worth a shot. Maybe start with 0v6. Currently 0V5?
If that is at me about BA3, it's been a while, I thought these were biased at 1 volt? I followed however 6l6 did his, I followed his build exactly. So whatever standard is. Mine is in Deluxe 5U case
Russellc
Russellc
Yes, it was directed at your comment about upping bias - but I was now talking about the output stage and not the front end 
Sorry.
Upping the front end Iq have proved perhaps the most positive results in my case, relatively speaking. 1v drop is spec, I am now at 1v8. But take care with higher rails.
Sorry.
Upping the front end Iq have proved perhaps the most positive results in my case, relatively speaking. 1v drop is spec, I am now at 1v8. But take care with higher rails.
I like mine fine. I built it years ago, still one of my favorite amps. My question came up because of the previously mentioned new speaker build. Designer says it will need amp capable into 4 ohms, and recommended 150 watts or more. BA3 seems not to have a problem!
Russellc
Addition: Vdrop still 1v, despite increased Iq, so I will not suffer voltage losses as a consequence of this. Iow the point of reducing source resistance.
