BX63A

[Zilch]

Notes to Ti Dome regarding and subsequent to the repair of his BX63A:

1) The use of an 18 VAC transformer overloaded the simple Zener shunt regulation power supply circuit, smoking 100-Ohm R10 and killing the +V. That likely took out the TL084C op amp, which also got pretty warm. :(

2) The Zeners had obviously been working really hard to compensate for the overvoltage before it died. I replaced them, as well.

3) The power requirements of BX63/A are very modest. A tiny 12VAC, 150 ma. transformer, the smallest typically made, would likely be plenty. It draws about 20 ma, only. I don't have the factory transformer myself, either. Perhaps someone who has one can tell us the actual rating.

4) The rear panel openings don't line up well with the RCA input jacks. This is an artifact of the way the board is mounted inside. On mine, the previous owner enlarged the holes. To do this properly, the unit must be disassembled, though that's not a terribly big task. The connectors don't seat completely, is all. It works fine with the ones I used.

5) A/B final testing of Ti Dome's was the first time I actually hooked my BX63A up to B380's. I was surprised to discover that there's no sub output in "Bypass" mode. I guess that kinda makes sense, but when Zilch rules the world, there'll be other options. ;)

6) The manual provides a method for determining the proper phase connection. Basically, it's get the system operating and then switch between the normal and inverted outputs to see which gives the most enhanced bass. That's the one to use.

7) Using B380 with 4430's, I think the lowest frequency setting (63 Hz) is optimum. No directionality, and just a bit of extra VLF boost for the 2235's already running.

8) RTA says I play the subs WAY too loud. :p

If they're just doing augmentation at the proper levels, I can hardly perceive them playing. They just kick in when the program material calls for it.

9) Enjoy your BX63A. It comes with Zilch's standard "30-30" repair warranty:

"30 feet or 30 seconds, whichever first occurs." :D

[Titanium Dome]

A big thank you to Zilch for his work on this. Next time I'm in the Bay Area, a few beers are in order and maybe an Afghani dinner or some sashimi. :cheers:

I'm eagerly awaiting the BX63A's arrival. Then it's lock and load!

Is that "30 feet or 30 seconds" from the time and place I pick it up? :confused:

[Zilch]

Is that "30 feet or 30 seconds" from the time and place I pick it up? :confused:Only if you gotta good lawyer.... :p

[leif]

[QUOTE=Zilch]Notes to Ti Dome regarding and subsequent to the repair of his BX63A:


8) RTA says I play the subs WAY too loud. :p


LOL, he have not seen that there are a knob to ajust the volume for the sub?
What level have you set your sub for on the volume?

I have a B460 with the Bx63a, and have mine turned up to about "11 O`clock"
I also prefer to use it at 63Hz, but when I want to have a good time playing real loud, I ajust it up, to take some preassure away from the main speakers and their amp. It rocks!

[Zilch]

Gain control on BX63(A) establishes the balance between the mains and subs. The relative loudness also depends on what amps are being used for each, and their gain settings.

I'm running the stereo mains on 6230 at 1:00, B380 subs on 6260 in dual mono at 12:00, and BX63A at 3:00. My preamp on this setup (liberally interpreted to include this Sony car amp/CD) controls the master volume.... :)

[Zilch]

I also prefer to use it at 63Hz, but when I want to have a good time playing real loud, I ajust it up, to take some preassure away from the main speakers and their amp. It rocks!
:scold:

God has given you fair warning.

Better supress that urge for right now.

[And get an SPL meter.... :yes: ]

[mrbluster]

I also prefer to use it at 63Hz, but when I want to have a good time playing real loud, I ajust it up, to take some preassure away from the main speakers and their amp. It rocks![/QUOTE]

Correct me if I am wrong......
I believe the adjustable crossover only effects the Sub output. The impedance matching switch determines the crossover point for the Mains.

[Zilch]

:hmm:

http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/UREI-%20BX63A%20ts.pdf

It's clear the frequency adjustment control has nothing to do with the HF output.

Regarding the impedance matching switch, manual says:

"The switch effectively adjusts the rolloff of the main loudspeakers. It is properly set when the sound at the corssover point is neither too 'thin' nor too 'full' -- in other words, when the subwoofer and the main loudspeakers are blending in the optimum way."

Also:

"The BX63A has a rear-panel 'Impedance Matching' switch. This should be set to correspond to the input impedance of the amplifier for your full range systems."

Choices are:

Low = 9-18 kOhm
Mid = 18-36 kOhm
High = 36 kOhm to infinity

My 6260 input impedance is 40 kOhms balanced, 20 kOhms unbalanced.

This is an unbalanced connection, so I should use "Mid."

Mrbluster is correct again.... ;)

[leif]

I will try to explain what I mean:
If the sub take more of the total job, the mains take less, right?
The main amp is 150 watt, while the sub amp is over 1.000 watt bridged.
So the main amp meet its limit while the sub amp is still "relaxing".
So to put a higher crossover point, the sub amp and sub get more to do, while the main speakers and amp get less to do. And therefore you can turn up the volume a little more. Understand what I mean?

[Zilch]

So to put a higher crossover point, the sub amp and sub get more to do, while the main speakers and amp get less to do.Apparently not. The crossover frequency control does not change the output to the mains. It's in the sub signal path only. See the schematic, above....

[leif]

As I understand from your posting, is that the sub only adds on in the bottom, and that both the mains and the sub is playing in the area below the crossover.
That can not be right. It is very easy to test that out. I put on some music, and feel the woofers on the mains with my finger. I push the "network in" button on the BX, and the woofers do a lot less excursion.

[Zilch]

Nope. Not saying that. A rudimentary passive filter comprising a 0.15 uF capacitor and the selected input resistance does kick in for the mains when the filter is engaged.

We're saying the frequency control does not alter that, is all. The impedance switch does change it.

On another subject of interest, please look at your power transformer and tell us what the output rating is.

[John]

I have 2 BX63A units and both power supplies are 12V 830mA

[Titanium Dome]

I have 2 BX63A units and both power supplies are 12V 830mA

Do you have those hooked to bridged stereo amps? Is so, can you share your configuration and wiring scheme? Thanks.

[Zilch]

I have 2 BX63A units and both power supplies are 12V 830mA
Closest I could find for Ti Dome here locally was 13.5 VAC, 800 mA. Sounds like he'll be fine with that, then.... :yes:

[John]

Hi One is for my B460 and the other was for my twin 2245 cabinet when I get around to constructing one!!!:o: I find it is easier to buy the parts lately, but harder to find the time to put it togeather?

I have all the manuals that came with the BX63A, if you need the info I will scan and send it to you Ti. Let me know?

[Titanium Dome]

I've got a downloaded copy of the Technical Manual, but that's it. Anything that will provide insight will be appreciated. :yes:

[Zilch]

This BX63A is drawing 39.7 mA at 13.82 VAC.

Call it a half-watt filter.... :p

[The cheapo transfomer's eatin' some, too, of course....]

[sanpablo]

After building my :banghead: :banghead: HARTSFIELD , my :D 4430 and before my B380 and my METREGON... I want to built my BX63A.

To do the board, who has a photo seen of over ? this will be easier to arrange the components.

Thanks

[Zilch]

Check back tomorrow. WAY past bedtime here now.... ;)

[sanpablo]

I construct a bx63a because it works well with the b380 but in 1985 the TL084 was a good technology.
Today, its not the same.

who know an bx63a equivalent shematic but whit a modern OPA ?

Thanks

[Lancer]

A rudimentary passive filterIt's a 100% viable 1st order line level high pass filter, cleaner than any op amp crap you can devise. It's too bad I really don't have the time to help you guys with this stuff anymore.

I construct a bx63a because it works well with the b380 but in 1985 the TL084 was a good technology.
Today, its not the same.

who know an bx63a equivalent shematic but whit a modern OPA ?

ThanksDon't waste your time. The BX63 is purpose-built for the B380 and B460. Carefull examination of the B380/B460 and BX63/BX63A designs along with a decent understanding of the publishings of Thiele, Small, and Keele will reveal what is going on. Don't blow wads of cash for one on eBay either. The nice chassis is the most expensive part of the whole mess. I collect them, rip the guts out and put whatever I feel like building at the moment in them. If you like building this stuff build one of Rod Elliots devices that offer greater flexibility.

[Ian Mackenzie]

Lancer,

Reminds me I must send you a discrete variable Q bass boost filter.

Don't be surprised if you blow more than your wad when you it!

Ian

[Zilch]

To do the board, who has a photo seen of over ? this will be easier to arrange the components.You are wise to attend to board layout, which matters in audio circuits. Not so much as with RF, but it matters. There have been failed attempts to build these here.

Power supply at lower left.

Interestingly, mine has TL074 in it, 12¢ more apiece than TL084, which cost me $1.39 for a pack of three in Jim-Pak at my local electronic parts store.

No doubt there are snazzier advanced-technology op amps now available to substitute, but we're talkin' 63 to 125 Hz here, remember?

Anybody know the difference between TL074 vs. TL084?

Ti Dome's unit had gold-plated I/O jacks. Mine's obviously El-Cheapo. Amp's not even socketed. :(

Note JBL standard "Gob o' snot" LED mounting technique.... :p

[Chas]

Quote: Anybody know the difference between TL074 vs. TL084?

Zilch, my memory cells suggest primarily offset, with the 074 being superior. Me thinks the pinouts are different too. I think the 084 is similar to the quad 741 (4741?) I do have the data sheets at home if you really want to know. :bouncy:

BTW: I am not up to date with the latest and greatest op-amps for audio and frankly for LF only, it's not an issue as far as I am concerned. Even a quad 741 would do the job!:p

[Zilch]

Yup, checkin' the specs here out of curiosity, and offset voltage and current are better on 071-074.

Pinouts are the same, TI just numbers the order of amps differently. Go figure.

[1992 TI Data Book. :p ]

Zilch will leave well enough alone and close this baby back up unmolested.... ;)

Requesting that Lancer forward all unwanted BX63A guts here for experimental use, please!

[Gonna make a dual-channel version....]

[Zilch]

I have all the manuals that came with the BX63A, if you need the info I will scan and send it to you....Maybe post them here?

"The [Impedance Matching] switch effectively adjusts the rolloff of the main loudspeakers."

Beginning at ~200 Hz, looks like:

[Titanium Dome]

Hi One is for my B460 and the other was for my twin 2245 cabinet when I get around to constructing one!!!:o: I find it is easier to buy the parts lately, but harder to find the time to put it togeather?

I have all the manuals that came with the BX63A, if you need the info I will scan and send it to you Ti. Let me know?


The scans were quite good and very useful. Now when the darn thing shows up, I'll have a better idea how to set it up.

I just PMed Zilch that the mailman left a slip in my box yesterday, so it should be waiting at the PO on Monday.

Fingers crossed :bouncy:

[Lancer]

Requesting that Lancer forward all unwanted BX63A guts here for experimental use, please!There's nothing to experiment with. You either understand what it is doing or you don't. I threw all those PC boards in the trash as they served no purpose.

Zilch, my memory cells suggest primarily offset, with the 074 being superior.The TL074 was better. Since the BX63 and BX63A didn't require the better TL074 JBL used the cheaper TL084 instead. With that saved expense JBL added in nice bypass caps and other stuff. Compare the schematics.

Like I said before, if you guys actually knew what was going on with the B380/B460 and BX63/BX63A then you'd know you had more options. For instance, you might not need, or want, to add excessive delay to the system. You might find in your room that you only need a few dB added at 25 Hz. If you were going to build your own BX63 or BX63A then you'd naturally build something a bit more versatile like perhaps http://sound.westhost.com/project84.htm. But hey, it's your time so feel free to waste it as you desire.

[Zilch]

I threw all those PC boards in the trash as they served no purpose.DRAT!

Now I'll HAVE to build somethin' better.... :p


For instance, you might not need, or want, to add excessive delay to the system. You might find in your room that you only need a few dB added at 25 Hz.That part I get. Frankly, B380 plays just fine here without the VLF boost, especially in pairs. Room gain seems to do the job instead.

This is the first time I've hooked up the BX63A. May have to go back now and play it with Sub1500's in B380 boxes, as earlier discussed. :D

[John]

[QUOTE=Titanium Dome]The scans were quite good and very useful. Now when the darn thing shows up, I'll have a better idea how to set it up.

I aim to please!!!http://audioheritage.csdco.com/vbulletin/images/smilies/biggrin.gif

[johnaec]

...build something a bit more versatile like perhaps http://sound.westhost.com/project84.htm. (http://sound.westhost.com/project84.htm. [/QUOTE) I'd love to modify something like that, to get 1/6 or 1/12 octave EQ for live bass guitar, (complete control note by note...).

John

[Titanium Dome]

...well, er, in the office anyway.

Thanks to Zilch's endeavors and the magic of the US Postal System I finally got the BX63A at the post office today. Took it to the office, hooked it up to the Carver pre and a couple of Soundcraftsmen amps, and woo-hoo! :homer: we were ready to rock.

The single B380 with a 600W push really brought the 4430s up to snuff. It filled in the bottom without being overbearing and let the 4430s stretch it out in that big space. As recommended, I ended up at 63Hz and barely cranked the gain, but the change was amazing.

Just what the doctor ordered. Thanks again, Zilch! :applaud:

[Zilch]

Hee, hee.

Geez, you didn't leave it plugged IN didya?

[Jus' kiddin'.... :p ]

[Titanium Dome]

Hee, hee.

Geez, you didn't leave it plugged IN didya?

[Jus' kiddin'.... :p ]

Everything is run through a power strip that gets turned off when not in use. The building is a historic landmark (old LA Library) so I don't want one of my toys to burn it down. :flamed: