RCA BA71B Project

[idylldon]

Just thought I'd share a couple of pics since I finally had the time to finish this project up.  I've had one BA71 module for a few years now just sitting on my bench waiting for another to show up for a decent price, which it finally did a few weeks ago.  At that point, I dove in and put it all together.  I took the easy path by using a JLM PS and the Go-Between setup, and, frankly, I think I'll do this from now on since it saves time and the cost isn't much more than doing it all myself.  Anyway, thanks to EMRR and PRR (and others whose names I'm forgetting) for all the info on these over the years.  These things sound incredible!





Found the old meatball logo on ebay for cheap so I used it even though it's a bit large!  The box is from an old Heathkit signal generator.

Cheers,
--
Don

 

[mjrippe]

I love these pres too and I have to say that is a beautiful job you've done!  Although I would have used RCA knobs instead of Gates   

Can I ask how you managed the -30vdc for the preamps as well as +48vdc phantom from the JLM supply?  Did you have to do anything odd ground-wise?  Also are your attenuators on the output or in the feedback loop?

The last pair I built into a lunchbox (BA-31s actually) had no phantom and Daven attenuators on the outs. 

 

[idylldon]

I love these pres too and I have to say that is a beautiful job you've done!  Although I would have used RCA knobs instead of Gates   

I had the Gates lying around so I put them to use. 

Can I ask how you managed the -30vdc for the preamps as well as +48vdc phantom from the JLM supply?  Did you have to do anything odd ground-wise? 

I converted them to negative ground.  Here's some info:  http://www.jlmaudio.com/forum/viewtopic.php?f=2&t=217

I think PRR mentioned doing this in a thread on here as well.

The power supply has two adjustable rails, so one is for 48 and the other provides the 30.

Also are your attenuators on the output or in the feedback loop?

They're on the input.  The JLM Go-Between has a 20dB pad built in and I added a variable input attenuator as well, which is a sub kit to the Go-Between.  I can either use the variable or the pad or both.

Cheers,
--
Don

 

[mjrippe]

Ahhh, very simple!  I think I will be ordering some of their supplies soon too.  Thanks for sharing a cool project!

 

[emrr]

Looks good