Completed the preamp and installed it in the system. The final bias voltages for both channels were in the .985-.995 volt range. Offset for the right channel hit a range of .oooV to -.000V (got lucky in final settings). The left channel ended up at .002V to .004V. In my system the gain was still too high, and I would rarely increase volume beyond a quarter turn. I am thinking of adding the 330-ohm resistor I have in parallel with the installed 200-ohm resistor reducing overall resistance for R13 to about 125 ohms. I raised those resistors slightly off the board making axis to attach the extra resistors a breeze vs removing the board to pull the existing resistor and install new ones. Any issues with that approach? Other suggestions?
I am really pleased with the sound and my first impression was an improvement in the sound stage, both depth, width and placement of musicians and vocals. In addition, definition has improved with better focus. The example I will site is back-up singers were always there but now they are better defined as unique vocalists. Thanks to everyone beginning with Papa, 6L6 and all who had gone before me and shared their experiences for me to learn from and those who responded to my questions along the journey. The image below is the system with the preamp on the second shelf right side.
Thanks again,
Chris
I am really pleased with the sound and my first impression was an improvement in the sound stage, both depth, width and placement of musicians and vocals. In addition, definition has improved with better focus. The example I will site is back-up singers were always there but now they are better defined as unique vocalists. Thanks to everyone beginning with Papa, 6L6 and all who had gone before me and shared their experiences for me to learn from and those who responded to my questions along the journey. The image below is the system with the preamp on the second shelf right side.
Thanks again,
Chris
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If you keep the higher Iq you can consider reducing the 22R’s to for example 15R. 7R is also stable but is a minimum value. But remember decreasing this value will increase the gain (and Iq 😳 ) and it is not nescessarily worth it for such a small bias increase.
Paralleling R13 will reduce Iq, so you need to rebias and readjust anyhow, unfortunately 😅
Paralleling R13 will reduce Iq, so you need to rebias and readjust anyhow, unfortunately 😅
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Then my observations of lower Iq after paralelling were probably temp and not circuit related
Hi. I'm going to build ba-3 balanced preamp.
I want to make an option to switch between regulated 24-0-24V and unregulated approximately 27,5-0-27,5V.
My dumb question is: do I need to make adjustments to bias and offset when supply voltage is changed?
I want to make an option to switch between regulated 24-0-24V and unregulated approximately 27,5-0-27,5V.
My dumb question is: do I need to make adjustments to bias and offset when supply voltage is changed?
why doing that complication?
anyhow, I'm not expecting any significant change with 2V5 difference in rails
anyhow, I'm not expecting any significant change with 2V5 difference in rails
1. I'm not shure that regulated ps would sound better than unregulated C-R-C with huge caps.
2. Because I have arduino and some relays. I can do it.
2. Because I have arduino and some relays. I can do it.
A worthwhile improvement IMHO is to make the power supplies dual mono.
Ie. a separate power supply to each side of the Ba3 Pre (which is already dual mono construction.
Depending on what you use for C3 things can get a bit cramped Consider mounting them off the main board.
That's exactly what I'm planning to do, I read your collective minds here on the forum! However I will be building the balanced version, two BA-3 boards, and two power supplies/transformers, and the necessary modifications to the original circuit to make it balanced.
I have a pair of Auricap XO 10.0u 160v that seem to fit nicely.
Hi everyone, I just finished the ba3 preamp, the mosfets I have for q3-4 are irfp240 and irfp9141 from diyaudistore matched, could I mount these?? I'm waiting for the irf 610 and 9610 to arrive, thanks
After several month`s as a quiet reader I've started today to build a BA3 preamp. I'll use 22 VAC and a psu which might be a little bit too much. After the psu one needs to use a superreg, so will I. 😉 Will use 24 V rails, a DACT attenuator and a Elma source switch. Altogether will be housed in a Galaxy chassis. Of course one needs porn, here are the first pics I made from the progress I made today. It`s a lot of fun to build my own audio equipment based on such a huge knowledge base as can be found in this forum. What a great place! Cheers!
