Jim
Do you have any idea when the store may be getting the boards? I guess mine got lost in the mail.
I also still haven’t received mine
My 2018 Burning OpAmp plays.. Just did a quick and dirty swap of my BA-1 FE built up as a preamp. The boards are just floating on some neoprene for now. 25 volt rails and Q8, Q10 do run quite warm. Output offset low and stable, P1 quite sensitive for sure. I have them setup for a balanced input, info on post #263. My hope is to do a proper rebuild with an upgraded PS that's almost ready. Will need to move to a larger chassis. And also try the autoformer idea I mentioned earlier for another 6 db of gain. Thank you Wayne and Jim for making the project possible.
First board built, so far only bench tested, works fine. Bandwidth from below 2Hz to over 2 MHz (my signal generator doesn’t go higher). Will assess square wave after I have a proper PSU, my lab supplies do cause ringing.
Have built it with the large outputs, mostly Beyschlag resistors (now also part of Vishal), and a 5 pF Silver Mica cap. The bias resistors for the outputs, for Q7 / Q11, and R17 are socketed to experiment with different values.
Q9 and Q14 do get warmer than Q8 and Q10. Offset and also bias current through the outputs varies little with rails between 18 and 24 V. Offset very sensitive to P1 here, as well.
Waiting for more parts and PSU. Build will probably continue after Easter Holiday ...
Best regards, Claas
Have built it with the large outputs, mostly Beyschlag resistors (now also part of Vishal), and a 5 pF Silver Mica cap. The bias resistors for the outputs, for Q7 / Q11, and R17 are socketed to experiment with different values.
Q9 and Q14 do get warmer than Q8 and Q10. Offset and also bias current through the outputs varies little with rails between 18 and 24 V. Offset very sensitive to P1 here, as well.
Waiting for more parts and PSU. Build will probably continue after Easter Holiday ...
Best regards, Claas
Last edited:
I bought 2SA1220 (Inchange Semi) from Kessler Electronics in Germany, along with the 2SC2690, also from Inchange Semi.
Working well (so far only bench tested with signal generator).
I was able to match hfe 144 one species to 181 the complementary species (forgot which was which).
2SA1220A-Q
2SC2690
The website seems only to be in German, unfortunately.
Hope this helps,
best regards, Claas
Working well (so far only bench tested with signal generator).
I was able to match hfe 144 one species to 181 the complementary species (forgot which was which
). 2SA1220A-Q
2SC2690
The website seems only to be in German, unfortunately.
Hope this helps,
best regards, Claas
KSA1220 in small quantities appear to be difficult to find. I’m looking into getting some when a kit is offered for the future store PCB. If there’s sufficient interest the transistors themselves or a small kit could be made that would have the transistors and the other associates bits. (Emitter resistors and feedback cap)
I have whatever extra parts from ordering your BOM from mouser, but used the "large" outputs and associated parts.....do I have an extra pair? (not home right now to see what they are, but I had some left over bits) Seems like there were 10 of some items but only needed 8?
Russellc
Yesterday, the case arrived that I intend to house Wayne's BA 2018 linestage in:
That case already comes as a passive preamp, with 128 step relay-based volume control and 4-way input switching, also remote-controlled via a supplied infrared remote:
I will use a separate PSU for this preamp. That will be configurable to also serve other future preamps. So, making room for the gain stage boards (relay board will also be moved closer to the back panel):
PSU build will commence once two more shipments from China have arrived. I also have to order a transformer from Toroidy and a case for the PSU from Modushop. After the Easter break ...
Best regards,
Claas
That case already comes as a passive preamp, with 128 step relay-based volume control and 4-way input switching, also remote-controlled via a supplied infrared remote:
I will use a separate PSU for this preamp. That will be configurable to also serve other future preamps. So, making room for the gain stage boards (relay board will also be moved closer to the back panel):
PSU build will commence once two more shipments from China have arrived. I also have to order a transformer from Toroidy and a case for the PSU from Modushop. After the Easter break ...
Best regards,
Claas
