JLM Baby Animal

[rodabod]

hey rodabod
Can the oep run at 1:2?
how about the output iron? needed?

There is a 1:2 OEP model. Otherwise, I think you can run the 1:6.45 at 1:3.2 as well (since it has split pri. and sec.) Not sure how well it performs in other configurations.

Output iron can offer +6dB gain and ground isolation but isn't necessary for shorter cable runs. You can run pseudo-balanced by tying pin 2 to ground via the same value of output resistor of the opamp.

Are you trying to keep to a budget?

 

[spyder_hobo]

Yeah, a bit of a tight budget. I could spring for the 990s but I'd like to get everything sooner than later so getting as much from JLM as possible would be best. Also, I'd like to stick to JLM's suggestions to keep troubleshooting to a minimum.

 

[buschfsu]

quick question.  looking over the schematic it looks like the V- pin on the opamp is tied to ground.  i though opamps had to have split voltage.  what am i missing?

 

[rodabod]

quick question.  looking over the schematic it looks like the V- pin on the opamp is tied to ground.  i though opamps had to have split voltage.  what am i missing?

From memory, Joe floated the ground up to +24V so that the rails ran at +24/+48V. Makes things simple.

 

[buschfsu]

beautiful

 

[spyder_hobo]

Got a BA (OEP/Hybrid/jlm OT) about 8 hours to build including the case (aluminum hammond enclosure) Lots of fun!
I wanted high gain for my B&0 ribbon so I went for
low ratio 1:6.45
RG = 22R
RL = 6.2k in series with 100k log pot. Range 150ohm to 2.4k
OT = 1:2

The only thing that confused me was, my hybrid kit did not come with any caps... I read about removing the cap opposite the BD140 so i left it NF but i threw in a 100uf 25v in the other spot. It seems to do the trick and everything seems to work the way it should. Also, I ordered a DC jack which is apparently .25mm or so to small. I had an extra here anyway. 

Turned it on, and wow!! a giant leap from my 003, I can finally put that sm7 to good use.

I just have one question aside from the hybrid cap confusion, when I do the voltage tests I'm getting 48v at +V but not getting 48v and 24v any where else more like 47.5 and 24.3 I'm relatively new to this and was wondering if that was normal or is something going on?

thanks

 

[roundhouse]

Is it possible to add an output trim knob to a BA, or can you only do it with a BAD?

Sorry if this has been discussed before, I've done my best to read through the 47 pages in this thread.

Thanks!

 

[rodabod]

Is it possible to add an output trim knob to a BA, or can you only do it with a BAD?

Yes, but it depends. Are you using an output transformer?

 

[roundhouse]

No, I would not be using an output transformer. 

Thanks for the reply!

 

[rodabod]

Well, you could probably use something like a 1K pot as a potential divider. This would be the crude way. For modern line inputs, your BA opamp would see ~1K which would probably work ok.

A nicer approach would be an attenuator, such as a switched attenuator, but this is something you'd need to probably make for yourself. There are 600R models such as those used in the 1176, but I'm not convinced about the power handling (even though they are commonly used with line levels).

 

[analogica]

Hi guys, im lost as always....help!!!

  1. How Can I wire a Jensen jt 16 b for ratio 1:2 ????

  2. Im looking for the changes I need to make (Rl, Cz, Rz...) for the Api 8pca + Fabios 2520

                                                                                  And jt 16 b + 990 C

  Could you help me???? thanks

 

[doncaparker]

Can anyone offer comments on how a standard BA sounds with a John Hardy 990c opamp (assume JLM 1:4 input trannie and no output trannie)?  I know from reading the prior several years of posts that it works fine, but I'm interested in some purely subjective sound comparisons from those who have heard the pre with this opamp.

Comparisons with the 99v, as well as with other pres with known characteristics, would be great.  Thanks.

 

[deuce42]

Perhaps a pretty lame question but....... I just built the FET DI for my Baby Animals.

There is a ribbon cable from the DI PCB which should attach to the BA's PCB. The BA PCB currently has a ribbon cable going to the XLR socket PCB. So where does the DI ribbon go on the BA PCB then?  Since there is only one ribbon cable socket on the BA PCB, am i missing a common ribbon cable that joins both the XLR board and the DI Fet board?

Thanks

 

[pietro_moog]

hi everyone!
i'm a total newbie in electronics.
i'm assembling my BA's and i've found i have not a 68r resistor (RG), but i have a 27k (i think it's for variable
impedence). what do i have to do?

does someone have some assembling pictures of the BA (2009)?

also, i have the jlm on/off switch. it has no diode, just a resistor. did i lost my diode, or it was never there?

thanks

 

[deuce42]

And now there is more to my woes. Please someone save me from my misery.

I realised the xlr board also had pads for xlr inputs. So I connected the ribbon cable to DI board and used standard wires from the pads on the xlr board  to the terminals on the ba board. Switched it on and noticed the smoke pouring out of my beloved BA2......

The DI board now has one fried resistor. Could I have the polarity of the electrolytic caps back to front? Thought I had checked with the picture first.

But its worse. I removed the DI board, reconnected the BA with the XLR board via the ribbon cable, resoldered the two links I put accross the back side of the BA board ribbon cable socket and turned the unit back on.  The BA2 works again, but whenever I switch the 48v/pad/phase switch I get this huge squeeling sound coming through my speakers for a moment,-  and the BA2 has lost its enormous tone it had. I know because I compared a track recorded before messing around with this and now and, other things being as equal as possible, a huge difference - lost that wide sound and the actual level appears lower on my input meter.

Where can I go from here??  

Am I

 

[deuce42]

Ok - so I have realised I have inadvertantly put the diode the wrong way round on the DI.

But now I appear to have ruined my BA. No signal passing through, squeals when flicking the switches, and and not getting 48v voltages measured across certain points in the PCB. Moreover, the 24v over the points of the input transformer dont read either.

How have I done this? Any help would be highly appreciated at this point

 

[rodabod]

Deuce, can you say what parts you have installed in your BA (there are many variants). Also measure voltages with the opamp removed.

 

[dude24man]

did you reverse the ribbon in assembly? Arty

 

[deuce42]

Thanks Rod and Arty.

This channel fo the BA has a jlm 1:4 and 99v combination.  I realised I needed a two way ribbon cable which goes XLR Board-DI Board-BA Board. Guess I will find one.

As for the BA itself -by tinkering it seems to now pass signal again but still this curious squeeling sound (imagine the sound a 80's digital watch made when its alarm rang but this squeeling is at extremely high volume)  whenever I flick the 48v switch or any of the other switches after that.

And I still notice that it seems to have slighly lost some top end. Just not as sparkly as it was at around the 12-15k area. 

 

[mac]

Quote: I have the BA4 'everything' kit.  The DI for the preamp all the way on the left won't fit because there's a threaded fitting in the way.  How do I get it in the case?

Hello all,
I'm into my BA4 everything kit build. All going well, two DI cards and first pre board stuffed.

I noticed this post from "bluemuse" a while back and see there was no response. I too have the same problem....
The DI card only fits if you rotate it about 60 degrees which means the components are almost touching the case. I re-read the forum pages but didnt see a solution  - any ideas?

Enjoying the reading and the soldering fumes....cheers....