JLM Baby Animal

[Greg]

I've experienced some oscillations with the Melcor at low gain settings; however, I have not tired it in the BA. I'm speaking in general terms here. Changing the feedback cap helped out with this. I wouldn't expect the 1731 to be a direct drop in replacement, but maybe.

 

[Baltimore]

I have a pair of original 1731s in some baby animals and they've been working with no problems for a couple months now. Sound great!

 

[Greg]

Nice !!! :thumb:

 

[mattmoogus]

You might have to play with the value of CL (in the BA) but that goes for all opamps and transformers.


M@

 

[Guest]

I'm finished stuffing the BA boards and the hybrid doa boards. Powered up the board - voltages seem ok so I put hybrids in - class a-a/b switch seems to work ok but the 2604 and transistors are hot - not cooking but uncomfortable to touch for more than 2-3 seconds - have not tryed passing audio yet - should they be this hot or have I done something wrong?

/Taz

 

[mattmoogus]

Yep that sounds about right, theyll get hotter in a class mode of course, but the OPAs are usually pretty warm. Does it sound and test ok?


M@

 

[Guest]

It passes audio!!! Just tried it with a line level signal - turned down and the it amplifies- yeah still though the opa and the bd transistors get very warm. I'll do some more testing.

 

[Guest]

He he it works fine :grin: :grin: :grin:

In fact both my BA's with hybrids work great.

the BD transistors get very warm as do the opa so i'm a bit worried by that but other than that they sound a LOT better than the mic pre on my joe meek tfpro p3 (which, ok is a budget unit) but the BA's have a much more detailed,clearer and strident sound when I did a quick comparison with my condenser mic. Noise wasn't too bad either considering I haven't put them in a box yet.

Couldn't hear much difference with the variable impedance but maybe that will be more noticable with my ribbon mic.

Thanks Matt and Joe!!!

/Taz

 

[therecordingart]

I thought everything was fine and dandy, but it isn't.

Two of the 10k rev log pots that I received are broken (i.e. they don't turn).

Anyone know where I can get these in the U.S.? I have a session next weekend and can't wait 2 weeks for them to come from Australia.

 

[mattmoogus]

[quote author="therecordingart"]I thought everything was fine and dandy, but it isn't.

Two of the 10k rev log pots that I received are broken (i.e. they don't turn).

Anyone know where I can get these in the U.S.? I have a session next weekend and can't wait 2 weeks for them to come from Australia.[/quote]


Are you sure there isnt just a nut or washer caught inside the pot? Weve had litterally thousands and only one failure so far appart from the ones that are mistreated. You cant get any similar pots easily in the states but if youre really stuck for your session you can use a log pot backwards, and gain will just be the wrong way round - when the knob is all the way down youre at full gain.


M@

 

[mattmoogus]

[quote author="tazwolf"]the BD transistors get very warm as do the opa so i'm a bit worried by that

Couldn't hear much difference with the variable impedance but maybe that will be more noticable with my ribbon mic.

Thanks Matt and Joe!!!

/Taz[/quote]


Depends how warm you mean, you should be able to touch the OPA but it will be quite warm and from memory the BDs are too warm to touch. If the pre seems to behave normally in every other way (no funny pops and scratches as you turn the pot, high output headroom, low distortion etc etc) then its probably ok.

Depending on what transformer youre using, what mic is plugged into it and what monitors youre listening on the variable can be quite subtle. Its pretty obvious on good monitors though and it is more or less pronounced depending on the mic and transformer. Maybe double check you have everything wired correctly - two wires coming from the pads for RL on the PCB, the appropriate resistor in series with one leg of the pot, wires going to the left and centre pins (when viewed from the top/front).


M@

 

[matta]

I thought everything was fine and dandy, but it isn't.

Two of the 10k rev log pots that I received are broken (i.e. they don't turn).

Anyone know where I can get these in the U.S.? I have a session next weekend and can't wait 2 weeks for them to come from Australia.

Just get them from Steve @ Small Bear Electronics in NY.

They are Taiwan Alpha, the same that Joe sells, they only difference is that it smooth shaft, not splined and is not detented. They feel smooth and work well, and are a quite a bit cheaper.

Cheers

Matt

 

[Adam]

Hi, i'm new here and very interested in the JLM stuff, also i'm a noob to DIY, so i have a couple questions...

whats the difference between the DUAL99v and the BA99v? is it just more gain? or is the sound completely different?

Is the dual99v much harder to build than a baby animal?

If i don't use an output tranny with the BA, will my signal be unbalanced?

thanks in advance for any help!

 

[greenmanhumming]

if fitting a screening can to an OEP transformer, should the can be soldered to the screen pin on the transformer to ensure connection?

 

[matta]

if fitting a screening can to an OEP transformer, should the can be soldered to the screen pin on the transformer to ensure connection?

You got it! Make sure you solder the can ALL the way around, for a good, solid connection.

If I don't use an output tranny with the BA, will my signal be unbalanced

No, depending on hwo you configure the PRE it will be either electronically balanced (if you use the IC opamp option) of Quazi Balanced via the Caps.

You wire it as balanced and as long as you are driving balanced +4dB lines you are A for away!

Cheers

Matt

 

[Lowfreq]

Um, a wee problem with my latest Baby A. :?
I'm doin another one with the cinemags, but i thought since I'd already got one goin with the 99v I'd try one with a 2520.

I've put in the BD681 and a 33v Zener diode, but i'm only getting 9.8v volts on the op-amp sockets......I'm looking for around 16v really......
My power supply is the 48v smaller one.

Anyone else had any problems like that?

Should I just change the zener diode to a higher value until I get a higher voltage??? Or what about the #10k? How does that effect things????

Everything else tests OK on the board.

 

[wiz1der]

Got my package yesterday, all complete, packaged very nice and orderly!

I am building my first unit (JLM 114 and opa2604) now and came across this:

[quote author="JLM Audio"]

Why does the parts list say 180pF. Is it supposed to be 220pF?

CL can be 180pF or 220pF. ][/quote]

I do have a 220pf in my kit BUT:

The table says that CL should be 390pf for jlm114 AND OEP.

What's up with that? I need the answer for jlm and oep as well (I'm building this one next), all I have is 220pf's!!

 

[JLM Audio]

or for simplicity I could install the regulator to set the voltage to 30v and just plug and play, the 2604 would then be close to its nominal voltage, which surely is not a bad thing?

Yep that will work.

There are 6 prongs on the power switch. Do I run pos and neg from pre to 2 prongs ,pos and neg from power socket to 2 prongs and , pos and neg to the green LED? What side do the red and black go?
What is the config on the rear power socket. There are 3 prongs. Do I bridge something? Also What is the right orientation for the red LED's that ge attached to the Phantom legs?

HI Nick did you get this all sorted from the email I sent you?

Does anybody here already tried the BA with some melcor 1731?
i'm willing to try given that i have few boards...
any comments?

Will work fine from the circuit I have seen for the 1731 with the opamp reg set with a 33v zener to give +/-16v.

There was some discussion about whether using Yamaha NE80200 opamp with the BA was feasible, a problem being the power requirement of the opamp. Have these been tested in the circuit?

They should work but I have not tested them. Also they are bigger than 1.1" so will only fit well on the BA but they will work and fit on the original JLM99*MB used for the Dual 99v.

I'm finished stuffing the BA boards and the hybrid doa boards. Powered up the board - voltages seem ok so I put hybrids in - class a-a/b switch seems to work ok but the 2604 and transistors are hot - not cooking but uncomfortable to touch for more than 2-3 seconds - have not tryed passing audio yet - should they be this hot or have I done something wrong?

The OPA2604 at idle on 48v is putting out about 0.5watt of heat. So yes it is hot. And each output transistor in Class A is putting out 0.75watt of heat. So yes they are hot as well.
Well at least hot to a humans touch :wink:. So yes all is fine.

Two of the 10k rev log pots that I received are broken (i.e. they don't turn).

Umm strange as the only time I have seen one these pots lock up is when the locating tab isn't cut off and the nut is done up tight on the bush and it bends the bushing as it is tightened because the pot will not sit flat against the front panel. Was there something stuck in the pots? or any other clues? As it is strange it is two pots that are faulty.

whats the difference between the DUAL99v and the BA99v? is it just more gain? or is the sound completely different?

Mainly the Dual 99v can do 80dB gain with ease and also can have a gain trim or fader inserted in between the two 99v's.

Is the dual99v much harder to build than a baby animal?

Yes as you have to build a power supply for the Dual 99v but the Baby Animal runs on a prebuilt 48v SMPS.

if fitting a screening can to an OEP transformer, should the can be soldered to the screen pin on the transformer to ensure connection?

Yes

If i don't use an output tranny with the BA, will my signal be unbalanced?

No it will noise cancel like a balanced output if it is going to a balanced input due to the XLR pin 3 sending a noise reference. The same idea is used on the output of a GML EQ and some modern Neumann Microphones.

I've put in the BD681 and a 33v Zener diode, but i'm only getting 9.8v volts on the op-amp sockets......I'm looking for around 16v really......
My power supply is the 48v smaller one.

Anyone else had any problems like that?

Should I just change the zener diode to a higher value until I get a higher voltage??? Or what about the #10k? How does that effect things????

Sounds like the opamp isn't fitted and your meter isn't drawing enough current to turn on the BD681 fully so you are getting a phantom low voltage which will go up when more current is drawn. Put a 4.7k resistor between _V and +V on the opamp pins and see if the volts comes right. If not either the zener or BD681 is faulty. The #10k value works for all zener voltages and doesn't need to be changed.

I do have a 220pf in my kit BUT:

The table says that CL should be 390pf for jlm114 AND OEP.

What's up with that? I need the answer for jlm and oep as well (I'm building this one next), all I have is 220pf's!!

The 220pF value is right for all transformers and opamps if normal RL from the tables is used but if you add variable impedance then CL will need to be changed to 390pF where shown for the BA to stay stable at full gain.

 

[Lowfreq]

Cheers for the guidance Joe. I'll try that out

Man you just answered a mountain of questions :shock:

AWESOME!!!

 

[Clevelandaudio]

Here's my finished BA4, and if anyone's ever seen a better use for a piece of b-ger gear, I'd like to hear about it. I had the pink vinyl stuff laying around from my buddy's sticker shop that closed, don't ask where I got the princess sticker, but it seems to fit the theme. I'm going to have my girlfriend hand letter the faceplate in a flowery font.

I got in a hurry after building three of these successfully and didn't check the fourth carefully before powering it up.... I'll be ordering another 99v because I bridged the output cap to ground... oops. All fixed now, but I've only got three 99v's; I tossed a 5532 I had laying around in the fourth one. They all sound great, I'm going to start using them this week to see what they're good for... my guess is that will be lots of stuff.

Nice kit, couldn't be happier. FYI, the OEP kits need another computer jumper to be totally complete. no biggie.