Yes, easily changeable but feedback will be affected hence affecting sound. Settled on 2-3db less gain than spec and it sounds perf.
Thought I would share my build. I really over thought the whole balanced build and after getting feedback here from 6l6 and others I realized it was very simple.
I am using my dac that has coax, line input, optical, and usb as a volume control and adjusting the preamp to the desired level and leaving it.
I built a separate PSU. Two amb o22 power supplies, Antek 20V 50VA transformers, and a 6 pin umbilical with 18V for each board.
The preamp chassis has 2 Alps Blue velvet pots (one for each channel).
Really runs my Aleph j nicely. This gave me the confidence to tackle a BBA3 balanced once the boards are back in stock for a pair of F4s to pull 100 watts. I had a pair of F4 before and loved them but had very efficient speakers and sold them before trying them at full capacity with the right preamp.
I am using my dac that has coax, line input, optical, and usb as a volume control and adjusting the preamp to the desired level and leaving it.
I built a separate PSU. Two amb o22 power supplies, Antek 20V 50VA transformers, and a 6 pin umbilical with 18V for each board.
The preamp chassis has 2 Alps Blue velvet pots (one for each channel).
Really runs my Aleph j nicely. This gave me the confidence to tackle a BBA3 balanced once the boards are back in stock for a pair of F4s to pull 100 watts. I had a pair of F4 before and loved them but had very efficient speakers and sold them before trying them at full capacity with the right preamp.
Attachments
Thanks for sharing your BA2018 @SRMcGee. Im sold, yes, I do think this will make a lovely Wolverine companion. Thank you for the pointer. You may want to increase the cost of your opinions as $0.02 seams to be on the low side!
A few questions if I may please:
- i'm assuming you opted for the BA2018 SE/differential unbalanced + headphone configuration?
- am I correct in thinking that you purchased all of the the following AA modules that are within this kit (plus your mentioned modifications)?
- how did you tackle your 2nd box power supply (maybe used the AcademyAudio LPS/Reg + toroidal ,...) and would you be happy to also share a picture please?
Kind regards, JT
JT:
My BA2018 was a two-chassis single-ended project. I did not ramp it up for headphone capability. The Academy Audio kit I purchased was their "Complete Audio Preamp Kit" (and not the "Complete Balanced Audio Preamp Kit"). I don't recall if Academy Audio offered their LPS9 power supply board when I built my BA2018; in any event, I used three of Pete Millett's power supply pcbs for his LR Phono Preamplifier (http://www.pmillett.com/LR_phono.html). Gross overkill, to be sure, but the BA2018 was a "no holds barred" project for me, so separate power supplies for each channel plus a third to drive the Academy Audio boards and front panel LEDs.
Notably, Mr. Millett now offers another power supply design that might work well: http://www.pmillett.com/audio_power_supply.html. And there is also Mark Johnson's wonderful VRDN power supply to consider. For me, a key determining factor was pcb size -- all of the power supply components had to fit into a HiFi2000 2U 230mm x 280mm "Galaxy" chassis (available from the diyAudio store but, for you, perhaps more conveniently purchased from Modushop / HiFi2000). Although not cheap, Mr. Millett's LR Phono power supply pcbs fit very nicely.
I did a write-up of my BA2018 preamp project in the Pass Pictures thread and included some photos; see post #5270 (https://www.diyaudio.com/community/...y-pass-amplifier.166784/page-264#post-6264974). In that same thread there was also some discussion regarding the Chinese military/aviation Y2M connectors (inexpensive and highly recommended) used in assembling the umbilical cable connecting the two chassis.
If there is anything else I can do to help, feel free to reach out.
Good luck however you approach your BA2018 project!
Regards,
Scott
My BA2018 was a two-chassis single-ended project. I did not ramp it up for headphone capability. The Academy Audio kit I purchased was their "Complete Audio Preamp Kit" (and not the "Complete Balanced Audio Preamp Kit"). I don't recall if Academy Audio offered their LPS9 power supply board when I built my BA2018; in any event, I used three of Pete Millett's power supply pcbs for his LR Phono Preamplifier (http://www.pmillett.com/LR_phono.html). Gross overkill, to be sure, but the BA2018 was a "no holds barred" project for me, so separate power supplies for each channel plus a third to drive the Academy Audio boards and front panel LEDs.
Notably, Mr. Millett now offers another power supply design that might work well: http://www.pmillett.com/audio_power_supply.html. And there is also Mark Johnson's wonderful VRDN power supply to consider. For me, a key determining factor was pcb size -- all of the power supply components had to fit into a HiFi2000 2U 230mm x 280mm "Galaxy" chassis (available from the diyAudio store but, for you, perhaps more conveniently purchased from Modushop / HiFi2000). Although not cheap, Mr. Millett's LR Phono power supply pcbs fit very nicely.
I did a write-up of my BA2018 preamp project in the Pass Pictures thread and included some photos; see post #5270 (https://www.diyaudio.com/community/...y-pass-amplifier.166784/page-264#post-6264974). In that same thread there was also some discussion regarding the Chinese military/aviation Y2M connectors (inexpensive and highly recommended) used in assembling the umbilical cable connecting the two chassis.
If there is anything else I can do to help, feel free to reach out.
Good luck however you approach your BA2018 project!
Regards,
Scott
I want to run this preamp into a DC coupled amp, and would like to know what people think the max allowable DC offset should be.
I know that the proper answer is that there should be a cap between the two units.
But, if the voltage gain of the amp is ~28, then should I be okay if I can get the preamp offset to settle somewhere around +/-2mV?
I know there is risk involved. I would not leave the room with the two units connected this way.
Thanks in advance for your thoughts.
Regards,
John
I know that the proper answer is that there should be a cap between the two units.
But, if the voltage gain of the amp is ~28, then should I be okay if I can get the preamp offset to settle somewhere around +/-2mV?
I know there is risk involved. I would not leave the room with the two units connected this way.
Thanks in advance for your thoughts.
Regards,
John
Finished my assembly today and got a few hours this evening to give it a listen. Very nice preamp!
I checked the DC offset at the speaker terminals a few times during the evening just to be cautious. The offset actually went down a bit after playing music, and seemed to stabilize around ~85mV. A bit more than ideal, perhaps, but certainly not going to start any fires.
To start with, it is dead silent. It even makes my phono-pre sound quieter, if that is possible.
This pre has very good headroom. Nothing seems to make it sweat, and it absolutely refuses to get harsh. Listening to records, surface noise is almost unnoticeable-- which is interesting. I would have thought that to be more a function of the phono preamp.
Everything sounds very clear, with good dynamics, too. Instruments sound very distinct.
I have read other builders post comments that they found the BA2018 a bit strident or bright at first. Mine was mellow from the first note. If I had to give it a single descriptor it might be "caramelly", in a good way, of course.
I wonder if this difference in opinion has anything to do with the choice of output transistors. I opted to use the big outputs Q8 and Q10. I used the Toshiba TTA/TTC004. I wonder if it would be worth it to pull the big transistors (and associated resistors) and swap for the KSC1845/KSA992 (and associated resistors/capacitors) to see how the sound changes. Someone must have tried it both ways. No?
Regards,
John
I checked the DC offset at the speaker terminals a few times during the evening just to be cautious. The offset actually went down a bit after playing music, and seemed to stabilize around ~85mV. A bit more than ideal, perhaps, but certainly not going to start any fires.
To start with, it is dead silent. It even makes my phono-pre sound quieter, if that is possible.
This pre has very good headroom. Nothing seems to make it sweat, and it absolutely refuses to get harsh. Listening to records, surface noise is almost unnoticeable-- which is interesting. I would have thought that to be more a function of the phono preamp.
Everything sounds very clear, with good dynamics, too. Instruments sound very distinct.
I have read other builders post comments that they found the BA2018 a bit strident or bright at first. Mine was mellow from the first note. If I had to give it a single descriptor it might be "caramelly", in a good way, of course.
I wonder if this difference in opinion has anything to do with the choice of output transistors. I opted to use the big outputs Q8 and Q10. I used the Toshiba TTA/TTC004. I wonder if it would be worth it to pull the big transistors (and associated resistors) and swap for the KSC1845/KSA992 (and associated resistors/capacitors) to see how the sound changes. Someone must have tried it both ways. No?
Regards,
John
If anyone is interested in using the VRDN for their own BA 2018 build, there is a possible group buy being discussed here:
https://www.diyaudio.com/community/threads/vrdn-psu-boards-for-waynes-preamp.394449/
https://www.diyaudio.com/community/threads/vrdn-psu-boards-for-waynes-preamp.394449/
Moving the VRDN interest post above to a thread in the Group Buy forum instead.
Here:
https://www.diyaudio.com/community/threads/potential-group-buy-for-vrdn-boards.395582/
Here:
https://www.diyaudio.com/community/threads/potential-group-buy-for-vrdn-boards.395582/
If anyone's bewildered by the acronym "VRDN", I don't blame you. It happens to be the name of a power supply PCB with voltage regulators, that works well with Wayne's BA2018 linestage. Here's a link to the Forum thread about it. Voltage Regulator with De Noiser:
VRDN: bipolar regulator PCB for line level ckts: ±11V to ±20V @ 1.5A with "De-Noiser"
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VRDN: bipolar regulator PCB for line level ckts: ±11V to ±20V @ 1.5A with "De-Noiser"
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