JLM Baby Animal

[JLM Audio]

The DC plug on the end of the small power supply is a 2.1mm x 5.5mm x 11mm which is usually easy to get the chassic mount mate for. Otherwise we have metal ones for $2AUD that fit a 8mm hole.

 

[Guest]

Hi
Regarding the hybrid opamp for the JLM BA
Could anybody tell me what the DC servo does?
And would it be possible/useful to be able to switch between class A and class AB operation.

Thanks
/Taz

 

[gevermil]

With 48v PS , Its possible to simply swap the 99v op amp with a hardy 990c or forssel 993 with no changes to the circuit correct ?
just want to make sure .

 

[jaygunn]

It's great to be able to hear WAV samples of peoples' projects.

In Matt's JLM1:4 and OEP samples and the difference is really clear. Of course it is hard to duplicate a performance, and I have noticed that the effect of moving a mic even 1/2" can sometimes be more dramatic than changing preamps. In this case, however, it's helpful that the differences we hear are consistent with the way JLM has already described the differences from these parts choices.

But here's the question: Can anyone, especially Matt or Joe (who have probably heard 'em all) give an opinion/guess about whether the difference in input transoformers would have a greater effect on the sound, or the difference in op amps?

 

[therecordingart]

Ok, my case will be here tomorrow and I want to make sure I have everything right before power up.

XLRs:
Pin1 - 0v
Pin2 - +
Pin3 - Neg

Power:
Positive wire to V+ on PCB
Negative wire to 0v on PCB
Then daisy chain the PCBs
Power switch breaks + from power supply

Pots:
Leg 3 to Gain on PCB
Legs 1 & 2 bridged and wired to 0v on PCB

Also...obviously the center pin on the plug from the power supply is + right?

One last thing....I didn't have to use any diodes, but I put in all of the 10k resistors. I read that there was one that I was supposed to leave out but I don't know which. Will leaving it in cause a problem?

 

[mattmoogus]

Hey recordingart,

That all sounds good but you havnt told us what config you have so we dont know if you need the all the 10ks or not.



M@

 

[mattmoogus]

[quote author="jaygunn"]But here's the question: Can anyone, especially Matt or Joe (who have probably heard 'em all) give an opinion/guess about whether the difference in input transoformers would have a greater effect on the sound, or the difference in op amps?[/quote]

Hey jaygunn, nice to see someone from India around here!

Thats a really difficult question and I think the answers are so subjective and case specific as to be useless.

I can say though that I think the input transformer (and how its loaded) usually has a more obvious tonal (eq) effect, as no transformer has a completely flat response. However their freq response with a given load doesnt tell the whole sonic story either.

For instance the JLM 1:4 tends to fatten the low end and low mids (particularly noticable on drums) even though there is no obvious change in its response curve in that area.

Also the OEP rolls off earlier down low (which you can hear easily) but it seems to add an emphasis to the upper midrange that doesnt show up on the freq graph. This is why its often the choice for vocals.

Every transformer has its own story and theyre all very different (to an audio engineer :wink: ).

I hear definite tonal differences in opamps aswell even though they rarely show up on a freq graph. In testing, usually the distribution of harmonics (especially the relative amount of 2nd and 3rd) in the THD test tells you more about the way it will sound. This is also very much load dependant with many opamps, tho there are a few that dont change tone much at all until they reach the limits of their specifications.

This is, of course, an oversimplification of a very complex topic and there are many many other factors that influence the way these parts change your signal, most of which I dont know anything about. Hopefully the things Ive mentioned make sense and if you get a chance to do lots of your own experiments you may observe similar things.

Really the only way is by DingIY and listening to the results!


M@

 

[mattmoogus]

[quote author="tazwolf"]Hi
Regarding the hybrid opamp for the JLM BA
Could anybody tell me what the DC servo does?
And would it be possible/useful to be able to switch between class A and class AB operation.

Thanks
/Taz[/quote]

Hi Taz,

This very question was asked a few pages back and I believe Joe answered.

The DC servo removes any DC offset from the output of the opamp, which enables you to use it without an output cap. I prefer the sound of the low end with a cap, but others seem to like servos.


M@

 

[mattmoogus]

[quote author="gevermil"]With 48v PS , Its possible to simply swap the 99v op amp with a hardy 990c or forssel 993 with no changes to the circuit correct ?
just want to make sure .[/quote]


Im pretty sure this is correct (the 990C is the 24v version right?) but youll have to wait for Joe to reply to be absolutely sure. Or if youre feeling adventurous you could just try it and see!


M@

 

[John Hardy]

(the 990C is the 24v version right?)

The 990C works with supplies anywhere from +/-12 VDC to +/-24 VDC.

John Hardy
The John Hardy Co.
www.johnhardyco.com

 

[therecordingart]

I have the JLM14 and OPA configuration

 

[Purusha]

Hey Joe and Matt,

I have a very nice suggestion, why don't you make a recording session with 5-6 different BA combos and a pro vocal and a great guitar and post it here plus on the JLM website. In this way everyone would get a first hand impression of what different combinations are all about. :wink:

And if you are confident that BAs can sound as other top notch preamps, put some hi-end pre next to the BA combos. :thumb:

What do you say?

 

[skipwave]

[quote author="JLM Audio"]

Do you omit the output coupling cap, since the 1:1:1 is gapped? I'd really like to use it that way in a BabyAnimal and maybe my Hampton-design JFet pres.

No. The Baby Animal has the opamps output sitting at half of the single 48v power rail so the output cap can never be left out. Otherwise the low DC resistance of the transformer would short the opamps output to the 0v and fry the output protection 51R resistor. This basically goes for all one power rail designs including the Hampton Jfet if it is the one I am thinking it is.
[/quote]

Many thanks Joe! Sometimes I need to be told things several times before they sink in. I just looked back at the Neev docs and it makes sense now.

 

[therecordingart]

I'd just like to thank you all for your help. I have 4 baby animal pres up n running as of 5 min ago. They sound pretty nice....now I need to do some recording!

My only mishap was grabbing the soldering iron by the element and not the handle!!!! I was trying to work too fast and burnt the hell out of myself.

 

[Purusha]

Question for Joe and Matt

I will be ordering some more stuff from JLM but before I do I would like to get some feedback of what would be the difference between these two combos:

LL1538 + Hybrid Opamp
or
LL1538 + 99V Opamp

Where would these two shine on?

So far I have these in working stage

4:1 + 99V + 1:1:1
OEP + 99V
2520 + Cinemag

so which of the two mentioned above would make more sense to add as a fourth combo?

 

[7s0und3studios]

Joe if you see this, check your email. I know you get tons but ive sent a few and havent got a reply. Messages are from [email protected] and are regarding repair and ordering. Thanks

 

[JLM Audio]

Regarding the hybrid opamp for the JLM BA
Could anybody tell me what the DC servo does?

The DC would normally keep the DC offset to close to 0v on a split +/-rail pre amp etc. But on a single rail pre like the BA it would only hold the output closer to the half volts rail (usually 24v) and since the hybrid has minimum offset already it is of no real use in the Baby Animal and should be left off.

And would it be possible/useful to be able to switch between class A and class AB operation.

Yes and has been covered earlier in this thread.

With 48v PS , Its possible to simply swap the 99v op amp with a hardy 990c or forssel 993 with no changes to the circuit correct ?
just want to make sure .

Yes

But here's the question: Can anyone, especially Matt or Joe (who have probably heard 'em all) give an opinion/guess about whether the difference in input transformers would have a greater effect on the sound, or the difference in op amps?

Both effect things greatly but the input transformer definitely sets the stage so to speak.

One last thing....I didn't have to use any diodes, but I put in all of the 10k resistors. I read that there was one that I was supposed to leave out but I don't know which. Will leaving it in cause a problem?

No just leave them in as it makes no difference.

I have a very nice suggestion, why don't you make a recording session with 5-6 different BA combos and a pro vocal and a great guitar and post it here plus on the JLM website. In this way everyone would get a first hand impression of what different combinations are all about.

And if you are confident that BAs can sound as other top notch preamps, put some hi-end pre next to the BA combos.

What do you say?

We are going to setup samples like you mention but there are several problems with samples in that they need to be made MP3 but even greater is the fact that for a sample to mean anything you have to have heard the original sound with your own ears so as to hear the tone difference. But I have a idea on how to get around this and once I have built a bit of test equipment needed Matt and I will try to make some files and see if it works.

I will be ordering some more stuff from JLM but before I do I would like to get some feedback of what would be the difference between these two combos:

LL1538 + Hybrid Opamp
or
LL1538 + 99V Opamp

Where would these two shine on?

The LL1538 is extremely clean and doesn't add much colour to the sound at all. So the tone gets down to the 99v and Hybrid. Both have silky class A high frequencies and the main difference is that the hybrid will be tight and fast in the low frequencies. Where as the 99v will be fatter in the low frequencies.

I would always prefer the LL1578 which has a great warm tone due to its higher ratio winding and which is the same pin out as the LL1538.

Joe if you see this, check your email. I know you get tons but ive sent a few and havent got a reply. Messages are from [email protected] and are regarding repair and ordering. Thanks

Hi Matt sent you a email today.

 

[yosh]

I just hooked up my finished BA kit. Everything sounds great if I leave the impedance pot still, but when I turn the pot it causes an extremely loud scratching sound. I took the pot out of circuit and checked it. I'm pretty sure I've got the wiring right. I'm using an alpha pot and as you look at the back of the pot with the terminals pointing up, I have ground connected to the right terminal and the other two terminals go to the RL terminals with the 4k7 resistor in series with one of the leads.

Any ideas on why I'm getting this awful noise? I've probably made an obvious mistake, I just can't think of what it would be.

One more question, earlier Matt commented that wiring a 100ohm 1W resistor across the output of the 99v causes the second harmonic to go way up. I'd like to hear how this sounds. To what pads or terminals exactly would I wire the resistor?

Thanks!!

-Josh

 

[yosh]

Ok, I'm stupid, I had the pot wired backwards. When looking at the pot as described above, the ground terminal is on the left.

So, my only question then is for Matt, about that 100ohm resistor.

 

[JLM Audio]

I just hooked up my finished BA kit. Everything sounds great if I leave the impedance pot still, but when I turn the pot it causes an extremely loud scratching sound. I took the pot out of circuit and checked it. I'm pretty sure I've got the wiring right. I'm using an alpha pot and as you look at the back of the pot with the terminals pointing up, I have ground connected to the right terminal and the other two terminals go to the RL terminals with the 4k7 resistor in series with one of the leads.

Any ideas on why I'm getting this awful noise? I've probably made an obvious mistake, I just can't think of what it would be.

The pot only wires to the 2 pads for RL in series with the fixed resistor value. The right terminal on the pot should be wired to the pots centre terminal and not ground. The whole RL floats at half volts so wiring it to ground will make a hell of a noise.

One more question, earlier Matt commented that wiring a 100ohm 1W resistor across the output of the 99v causes the second harmonic to go way up. I'd like to hear how this sounds. To what pads or terminals exactly would I wire the resistor?

Usually a 600ohm load is all that is needed across the +/-out terminals but the 99v can drive a 100ohm load if you as long as you don't then make it drive a 1:2 transformer and 600ohm load as well at the same time. It will drop the output level somewhat due to the 51R output protection resistors on the BA pcb. But yes it will make the 2nd harmonic go up but the 99v is fat sounding already so why you would want more I don't know.