RCA BA71 project

[fum]

Well,

My project for the weekend was to work on some RCA BA71's. I've got the first channel up and running merrily.

I recapped this channel before firing up. The plan is to fire up the other ones, do a listening comparion to the first channel ( to compare recap vs. old cap), and then recap the other two.


Here's the progress:

 

[CJ]

Cool! How do those sound?
Any problems with those old PC boards when recapping, traces lifting, etc?
Lotta caps, eh?

I have a few waiting for the rack also. BA71 and 73.

I hope the transistors are ok, becuase those old metal cans are are hard to find.

 

[jensenmann]

Same with me. I have three BA71 lying around, waiting for recapping and racking. But I barely have time to make the frontpanel. Drilling in the garage in winter really sucks.
Let us know how the sounddifference between old and recapped is. Which caps are you using for recapping?
:guinness:

 

[fum]

Ok,

Things settled for a moment(but just a moment), and got these done real quick like:

For caps, I used the same sprague electrolytics that were in it, just new, the ones in it were date coded 1969. To my ears, the recap helped clear up the high frequency tracking a bit, the non-recapped seems a bit mushy. Not a total night and day difference, but worth doing.

This is a 46C microphone, about 3 feet back from the acoustic, all tracks were tracked with the guitar and microphone in the exact same position. I'm thinkin a little closer would have been better. Electric guitar, perhaps even better :twisted: :


The old cap version of the BA71:
http://www.shinybox.com/diy/BA71/46C-OldCapBA71.aif

The recapped version of the BA71:
http://www.shinybox.com/diy/BA71/46C-StockBA71.aif

Using my Melcor based API pre:
http://www.shinybox.com/diy/BA71/46C-API.aif

For a non ribbon mic reference, here's a 414EB P48 in the same spot as the ribbon:

http://www.shinybox.com/diy/BA71/414.aif

Regards

ju

 

[martthie_08]

hey ju, I had a short audition on those files, the recap did open up the top and low end as well, really brings out the belly on the lower chords, but to really find out what is "better" you would have to do more testing with voice and other instruments. I did find the old cap version to have something special, but maybe this could be replicated on the recapped version with a little filter roll off on highs and lows. The API is a different animal, the mids are situated lower, and the the 414 clip is a little lifeless, i.m.h.o.
To be honest I didn't "like" any of the recordings too much, what kind of guitar were you playing in what kind of room? It does though bring out the differences of your pres, which is what you were going for in the first place! Thanks for posting this, I always enjoy listening to this kind of stuff :thumb:
I would leave things the way you have them right now, if the old non-recapped modules aren't giving you any trouble. Sometimes it takes me weeks to find out what I really like, sleep it over...

 

[analag]

[quote author="martthie_08"]To be honest I didn't "like" any of the recordings too much...[/quote]
Is this what they call brutal honesty....well it's the best way, the ribbon mic sounds very real.

 

[jensenmann]

Thanks for those soundclips :thumb:
Recapping is obviously worth the effort. I´m looking forward to doing it on my BA71s.
Btw I´m kind of with martthie as I do not like the 414sound too much on this guitar (though they have a more sparkly top).
:guinness:

 

[Samuel Groner]

Thanks for the files!

Did you recap with the same values, or bigger ones?

Samuel

 

[fum]

[quote author="analag"][quote author="martthie_08"]To be honest I didn't "like" any of the recordings too much...[/quote]
Is this what they call brutal honesty....well it's the best way, the ribbon mic sounds very real.[/quote]

Brutal honesty doesn't bother me a bit. I'm not after "worlds best acoustic guitar sound" for these clips, it's more, make some noise in front of the microphone so that you can hear what the pre is doing or not doing.

so you either get an acoustic guitar, or some dink saying "ummm... test.... 1...2....3...." :grin:

[quote author="Samuel"]Thanks for the files!

Did you recap with the same values, or bigger ones?

Samuel
[/quote]

I used the same values as the original.

Regards

ju

 

[Bauman]

Can't wait to get home and hear those files!! :thumb:

 

[wilebee]

nice Jon looks good! remember those input transformers won't take more then -15 dbm so don't drop it a line level signal unless you pad it 20 db

Wil

Wilebee

 

[fum]

Good thing I built a 20dB pad into the unit, eh? :grin:

ju

 

[squib]

what are you doing to control the gain of these?
Or are you just letting them run at their fixed gain

 

[fum]

Yup, just running them at +46.

the 20dB pad sit's them perfect as makeup gain for the passive summing arrangement I have.

Regards

ju