JLM Baby Animal

[JLM Audio]

What about the cap? Don't want to get the wrong one.

Any 47pF small ceramic will work in there. If you are using a JLM99v only the top 47pF is needed on the PCB.

I'm making half rack panel design for a friend to cnc, is there any possibility of getting a blueprint or something of that front panel so I can snatch the exact spacing between toggles and so on? Would be stellar.

I will get the DXF hole punch files and Corel laser/screen-printing files up on the web site soon for both the BA2 & BA4. If you need a different output file type let me know and I will see what I can do.

What if, just to test it, elliminate the 10R's until I get a few of the carbon replacemnts? How much difference would 10 ohms make?

Depends on if you would prefer one dead resistor or several blown caps, dead opamp and maybe burnt out input transformer secondary if there is a fault. The 10R is there as protection and to add a bit more RC filtering to the power rail. It can be 10R to 47R without any problems. The trouble is the original metal film ones are failing on the surge current at power up occasionally even without a fault on the BA. When they fail there is no external sign and the value of the resistor will be random as the metal film is internally fractured. I recommend replacing them with a normal carbon type as they will survive the power on surge and if there is a real fault they will heat up and show signs of burning. If your BA doesn't work the 10ohm is the first thing to check.

 

[bluesgirl]

Depends on if you would prefer one dead resistor or several blown caps, dead opamp and maybe burnt out input transformer secondary if there is a fault.

Well of course I wouldn't that is why I asked. Didn't have to get snippy about it!

I would still appreciate an answer to this question:

Do the resistors read differently when on the board? Because I am getting weird readings for the 220k's at 9.8k and the RL is reading 470 ohm, two of the 6.8k's are reading 3.4k, and the 10k's are reading correctly but most take a long time to get the correct value. All the other values are reading correctly and get to their values quickly. These readings of course are all being taken with no power to the preamps.

I don't have any way of testing the capacitors.

Is this all normal?

Also I made this statement:

I used some extra 10k ohm's in place of the 10R just to see if it would work. It helped the one preamp to work, which was extremely distorted before. I also stuck a set of headphones on the output jack of that preamp and it sounds clean. But if I use the headphones on the output jack of the other preamp it is distorted but it sounds ok if it is ran through my soundcard. Nothing is different between the two except the one distorted thru the headphones has the DI on it.

Trying the 10k's in place didn't hurt it did it? I figured if the one read 2.2 meg 10k certainly couldn't hurt it. And is what I am describing normal for the 10r's not being in place with a 10k there (distortion out of the jack on the one preamp through headphones) or is something more wrong? Why would the one not be distorted and one be distorted all things being equal?

Hey I didn't do anything except put the power to the preamps and I have this issue that I was afraid that everything was fried. That was a bit worrisome. Especially since everything worked perfectly up until that point. So pls understand my concern here.

Thx,

Tammy

 

[matta]

Do the resistors read differently when on the board? Because I am getting weird readings for the 220k's at 9.8k and the RL is reading 470 ohm, two of the 6.8k's are reading 3.4k, and the 10k's are reading correctly but most take a long time to get the correct value. All the other values are reading correctly and get to their values quickly. These readings of course are all being taken with no power to the preamps.

Tammy,

You CANNOT test a component in circuit for the exact reasons you mention above, this is basic electronics 101. If you wish to test a component in circuit you need to lift the leg of the component in question and then measure across it, but once it is in circuit there is isn't away a check it at face values since the components in the circuit will affect the readings you are given.

Some may read correctly, but a lot won't, remember even with no power a capacitor will hold a charge and voltage will still be present in the circuit unless it is discharged somehow.

I hope this answers your question.

Trying the 10k's in place didn't hurt it did it? I figured if the one read 2.2 meg 10k certainly couldn't hurt it. And is what I am describing normal for the 10r's not being in place with a 10k there (distortion out of the jack on the one preamp through headphones) or is something more wrong? Why would the one not be distorted and one be distorted all things being equal?

Electronics is about playing around with the figures. If something calls for a theoretical value of say 1K82, using a 1K8 will prob be fine, a 10R to 10K is a 9,990 Ohm difference and that would make a SERIOUS difference on what is happening in the circuit.

It may have caused little to no permanent damage, I have not looked at the circuit in detail, but it may or may not have, I'll let someone more qualified answer that for you.

If in doubt, ask, don't just go plugging in parts, it will say headaches further down the line trying to troubleshoot damage.

Cheers

Matt

 

[mattmoogus]

Hey Tammy,

Like Joe said the 10ohm needs to be there and can be between 10 and 47 ohms without seriously effecting the circuit. 10k will definitely not work, its in series with the power rail so it must be low ohms or your pre wont get the right power.

Some parts will read differently but a resistor should never read higher than it is, only lower, although if there are large caps around it the voltage stored in them may confuse your multimeter. Thats why some of the values take a long time to get to a stable value, because your multimeter is charging a cap and you wont get a propper reading until its charged.

Its likely that the caps are fine if they havnt popped their tops, at least assume this until you have tested other things.

If the 10ohm had blown and gone to above 100k, your pre would be running with very low volts and so would likely sound distorted at any level. Sounds like you just need to replace it with a carbon 10ohm and try powering up again.

I wouldnt test with headphones, probably plug the pre into a higher Z input like a mixer just while youre testing. A 99V should be able to run phones down to 70ohms but Ive never done it so I would just use a mixer until you have your problems sorted.

Just to clarify, you have two BA pres, one is working and one isnt. Is that right?


M@

 

[bluesgirl]

Thanks Matt.

I never had electronics 101 and u r right I shouldn't be messing around without asking. But logically I figured if the bad one read 2.2 meg then 10k is a closer to 10R than the 2.2 meg. I haven't plugged it in since anyhow but when I did it cleaned up the really bad pre and the other one just stayed the same since the value of the blown 10R on that one reads 6.9k off the board.

I guess my question is that do the values I am getting on the board match other peoples values or the norm so I can judge if the rest of the components are ok without pulling all the resistors out to check them? I get these values on both boards so maybe that tells me something. :idea:

I can't get the 10R's until next week.

Hey when this happened other things such as my car having issues were happening so I was overwhelmed and a little ah! well you know neurotic!! :?

Thx,

Tammy

 

[bluesgirl]

No caps blew tops or anything. The resistor values are all either lower or the same as their normal value so that must say something.

I wouldnt test with headphones, probably plug the pre into a higher Z input like a mixer just while youre testing. A 99V should be able to run phones down to 70ohms but Ive never done it so I would just use a mixer until you have your problems sorted.

Oh but I tested both ways. Both pres work now (but they have th 10k's on them and I am not testing again until I get the 10R's as recommended) but the one that has the DI is distorted using the headphones off the jack but is ok through the the soundcard. The other is good both ways (Has no DI)

Thx,

Tammy

 

[mattmoogus]

Im surprised they work at all with 10k, but there ya go! Im guessing that the one with the DI is distorted because the opamp for the DI is drawing more current for that channel than the other, and trying to drive headphones is more than it can bare with 10k in series with the power.

We can send you some carbon 10ohm resistors if you like, just email Joe.


M@

 

[Schmilsson]

[quote author="JLM Audio"]

What about the cap? Don't want to get the wrong one.

Any 47pF small ceramic will work in there. If you are using a JLM99v only the top 47pF is needed on the PCB.

I'm making half rack panel design for a friend to cnc, is there any possibility of getting a blueprint or something of that front panel so I can snatch the exact spacing between toggles and so on? Would be stellar.

I will get the DXF hole punch files and Corel laser/screen-printing files up on the web site soon for both the BA2 & BA4. If you need a different output file type let me know and I will see what I can do.
[/quote]

Ah, didn't notice at first you didn't need the second 47pF, no worries then, I did solder two in the first pcb, I don't need to take the lower one out right?

I'm making the design in photshop/front panel designer, but I guess a simple hi res jpg would work, just to get me in the ball park, that's all.

 

[bluesgirl]

We can send you some carbon 10ohm resistors if you like, just email Joe.

Well I appreciate that. I found a place local that has them so I will try there first.

I am assuming they are 1/4w 5% tolerance carbon?

And thanks for all the support also.

:grin:

Tammy

 

[gevermil]

Im diggin the 1:4/99v the more I use it !
Its pretty cool on the drums

 

[3nity]

Looking comments at the Baby animal, somebody said they have the same topology as the apis 312s.
altough few people are using the BA without output trannie.
could this be feasable with the apis??
or this simply wont work within the 312???

thank you.

 

[mattmoogus]

You can run a 312 without an output transformer, you just miss out on 9db of gain and of course it will change a sound a little. I usually prefer output transformers on all my pres but thats not to say going without one wont sound as good, just a little cleaner, and unbalanced of course.


M@

 

[JLM Audio]

Do the resistors read differently when on the board?

Yes

I am getting weird readings for the 220k's at 9.8k

Yes that is right because it is in parallel with the 10k gain pot.

RL is reading 470 ohm

Yes that right as it parallel with the transformer secondary resistance which around 470R.

two of the 6.8k's are reading 3.4k

Yes that is right as the 2 x 6.8k resistors are in parallel due to the low ohms of the transformer primary.

Trying the 10k's in place didn't hurt it did it?

No but it will not run properly with resistors bigger then 47ohm in the 10ohm position.

Ah, didn't notice at first you didn't need the second 47pF, no worries then, I did solder two in the first pcb, I don't need to take the lower one out right?

No you can leave it on the board as it will just not be used with the 99v.

I am assuming they are 1/4w 5% tolerance carbon?

Yep that's the ones.

The more Im using it the more Im diggin the 1:4/99v
Im getting some great sounds on the drums.

:grin: :grin:

Looking comments at the Baby animal, somebody said they have the same topology as the apis 312s.
altough few people are using the BA without output trannie.
could this be feasable with the apis??or this simply wont work within the 312???

Yes will work fine but like Matt said you will lose 9db of gain.

 

[bluesgirl]

Thanks for the answers Joe.

Looking comments at the Baby animal, somebody said they have the same topology as the apis 312s.
altough few people are using the BA without output trannie.
could this be feasable with the apis??or this simply wont work within the 312???

Hmm! I thought a lot of people were using the BA's WITHOUT output transformers?

I understand some headroom may be lost and I know I am losing some gain but how much is the quality compromised? I'm getting (or I was getting until the resistors fried) some good quality sound. How much better would it be with the output trans?

(Or am I being silly and answering my own question by stating the gain and headroom loss) :?

Thx,

Tammy

 

[mattmoogus]

Just different flavours of good. Both ways have their advantages and disadvantages but the difference is subtle and certainly not 'make or break'. The only way to know what you prefer is to listen to both. I prefer transformers but sometimes Ill build gear without them (like my passive mastering eqs) because I want less color.


M@

 

[bluesgirl]

Thanks. I feel better knowing I am not at a great loss by not having the out transformers.

:grin:

Tammy

 

[OverSound]

After some really stupid mistakes and corrective measures I've got all 4 of my pre's up and running. Instead of testing the sound here at home I brought them to my real studio (not my crappy home studio with the M-audio FW410 and Alesis M-1 mII speakers :sad: ) and hot damn if they don't kick ass all over the Focusrite pre's we have used for years. We spent a lot of money setting this studio up and have actually got some of the best (Rock) guitar sounds in Minneapolis. I know this is presumptous but we are usually booked solid with work from musicians wanting to do their guitar overdubs with us. Now the guitars are even better. Our first paying customers since finishing the pre's are in studio this week and we'll see how they respond, but I think they'll love them. Thanks Joe for your help. You too Matt. I'm surely gonna be buying the dual 99v and the micro 1290 to flesh out the arsenal as soon as a few more jobs come in.

Awesome! :razz:

Brad

p.s. The pre's I bought are: 2 99v/JLM14; 1 99v/OEP; Hybrid(A/B)/OEP. I'm gonna do at least one more BA with a lundahl/oep combo in addition to the micro and dual 99v.

 

[mattmoogus]

Awesome! Good news and good reviews is what makes it all worth while.
If you could post some more opinions of what the different combos sound like once youve had a good chance to try them, Id be very interested to hear.
:grin:
:thumb:
:guinness:


M@

 

[OverSound]

Sure will Matt. As an overdub studio we don't get the chance to do drums often. I will try to get to another studio and try these on drums but for now I'll get you guys reports on Bass, Guitar and Vocals. I'll actually be recording folk instruments for my album real soon too. I'll Let y'all know how it goes... By the way, the 99v/oep and hybrid/oep worked great on my Crowley and Tripp Ribbon mic. Infact there was tons o'gain left. Awesome...

Brad

 

[Lowfreq]

Well, I finally got my ass round to finishing off my Baby A's. :roll:
No pics at this stage sorry folks, but hopefully soon.

Well, I've really only got one going at the moment , having a few issues on the second one at the moment due to my bad desoldering on a few components, but I will nut that one out eventually. :wink:

But, the main thing is I've got one going!!! :green: :thumb: :thumb: :green:

I've got the cinemag CM-75101APC in mine, and instead of goin the 2520 route, I got a bit lazy and went with an OPA2064 IC(is that the correct number?) as I had some lying around, and time to build the 2520's never seemed to present itself.

I like the idea of going the 24v way.....Less part's to use....Less for me to do. ha ha

Caps wises I found the the nichicon HE series from mouser were one of the only brands that fitted the dimensions of the baby A. I do like these caps in a lot of cuircuts tho.

Now I only had a quick muck around with some bongo's & percussion in my room with a couple of different mics, so I didn't get too much of a chance to form on opinion on this combo..............but so far to my ears, it sounds very quick and snappy, and It's gonna end up on snare when I do some drum recordings later this week. :thumb:

It's got stacks of gain too. Way more than i expected!!

As for the different parts I kinda went with similar stuff to what is on Joes page, but for the Lundahl 1578 as they're both a 10:1 ratio.
Not exactly a scientific approach, but hey it works, and it works well :green:

Only prob I found with the cinemag, is when I tried swapping out the IC for my 99v op-amp out of my other pre. Too tight a fit for a cinmeag & a 99v without bending the board too much.

Otherwise, another happy camper round here. :grin: :grin: :sam: :sam: