JLM Baby Animal

[mattmoogus]

[quote author="greenmanhumming"]I am using Rode NT2000 on vox. Rode NT5's on guitar and bouzouki, sometimes the NT2000 on zouk too. AKG c451 on fiddle and viola. I'm saving up for a C414. Any comments or suggestions about that mic lineup?[/quote]


The way I pick my signal path, if im using a bright mic (like anything made by Rode) Ill use a smoother/slower sounding pre. Others have different methods but thats mine. You might be onto something with what you said about the mackie recordings, as a Rode into a Mackie pre would be a very bright combination.

Maybe do a few more songs and then see how everything stacks up. There will always be plenty of options for sound tweaking, even on the pres youve already built, with just a few part changes.


M@

 

[7s0und3studios]

So despite some setbacks with the other two baby animals, i found the problem. The 54v powersupply had been set to 48ish, and the trimpot is not functioning. I turned it to the right all the way untill it stopped, and ignorantly assusmed it was at 62v. Problem is i already fit the regulators. will work on that...

for the problem now. Pre sounds amazing on my high output blue mic, but everything else the gain is NOWHERE close to 60db. Using the gain pot will probably dim or boost by about 10db at the most. Could this be due only to the fact that i have regulators for 62v and powersupply is putting out just shy of 50? i went back with voltmeter on the ps and trim pot does nothing, turned both ways. Kind of at a crossroads here..

 

[7s0und3studios]

by the way..mics im referring to all use phantom power.

also, my DI with my guitar is distorted, no matter how quiet i play, and when i unplug the guitar it does not switch back to the mic. who votes i messed up that assembly?

 

[JLM Audio]

So with no pads jumpered hybrid should light the LED and operate in class A?

Yes

is there any way to test the output transistors?

Cheap in circuit transistor tester or multimeter.

what is the difference in sound? Joe?

The OEP running at 1:6.45 has 17dB of gain which is 5dB more gain than the JLM14 so can do 60dB of gain with a 99v and no output transformer. It can also be setup to run as 1:12.9 which gives 23dB of gain which is 11dB more gain than the JLM14 so can do 66dB of gain with 99v and no output transformer. The OEP with only a 27k load has a slight lift in the high freq to give a slight air but is darker or more coloured in tone in general when compared to the JLM14.

another idea i had when looking at the hybrid schema, is:
what about a version that doesnt have the DC servo, and has basically two channels of the basic class A only circuit. use the other half of the 2604 that was used for the DC servo, and add two more power transistors instead of the DC servo components, then it could be used in balanced mode, kind of like the 2604 in the basic BA.
would that work? would it sound good? would it be a total current hog? would there actually be any advantage?

I have some rough Dual hybrid PCB layouts that I have been working on that do just that. They have the second opamp run as a inverted unity amp.

The 54v powersupply had been set to 48ish, and the trimpot is not functioning. I turned it to the right all the way untill it stopped, and ignorantly assusmed it was at 62v

Make sure the large power supply is set to 110v/240v with the switch near the IEC socket on its side to match your mains volts. If you just turn the trimpot to full the voltage will go higher then 62v and bring in the overvoltage protection. To set it up read the alignment procedure at the bottom of the Baby Animal web page at this link. http://www.jlmaudio.com/Baby_Animal_Mic_Pre.htm

Pre sounds amazing on my high output blue mic, but everything else the gain is NOWHERE close to 60db

You don't mention what combo you are running but gain should line up with the table on the Baby animal page perfectly and remember 1.1" opamps will be 6dB less then stated.

Using the gain pot will probably dim or boost by about 10db at the most.

Gain should go from roughly 20dB to full gain so something is very wrong here as it should be about 40dB gain range.

Could this be due only to the fact that i have regulators for 62v and powersupply is putting out just shy of 50?

Tell us what combo you are running transformer and opamp wise and what regulators you have fitted as the voltage change from 50v to 62v will not change the gain range. Send me some clear in focus (macro) photo's to my normal JLM email so I can have a look at the PCB's and wiring. Sounds like a wrong resistor value on the PCB etc.

also, my DI with my guitar is distorted, no matter how quiet i play, and when i unplug the guitar it does not switch back to the mic. who votes i messed up that assembly?

This could be because your gain range on the mic pre seems to be wrong except for the bit about not switching back to the mic. Send me photo's.

 

[Schmilsson]

[quote author="JLM Audio"]
The OEP running at 1:6.45 has 17dB of gain which is 5dB more gain than the JLM14 so can do 60dB of gain with a 99v and no output transformer. It can also be setup to run as 1:12.9 which gives 23dB of gain which is 11dB more gain than the JLM14 so can do 66dB of gain with 99v and no output transformer. The OEP with only a 27k load has a slight lift in the high freq to give a slight air but is darker or more coloured in tone in general when compared to the JLM14.[/quote]

So a 99v with the OEP at 1:12 with a JLM111DC out at 1:2 should give me 72db?
I'm going for a stereo unit and want the 99v's but still need plenty of gain for ribbons and dynamics.

 

[mattmoogus]

That should work for ya, but if you need more you can use a Hybrid or get a dual 99V kit. Thatll get you up to 80ish, from memory.


M@

 

[rodabod]

[quote author="eskimo"]
So a 99v with the OEP at 1:12 with a JLM111DC out at 1:2 should give me 72db?
I'm going for a stereo unit and want the 99v's but still need plenty of gain for ribbons and dynamics.[/quote]

Just keep an eye on what the input impedances ends up being as this will affect the sound you get from your dynamics and ribbons.

 

[fatty]

hey matt, you guys rule! 11pm and you and joe are both still up working and answering emails and posts on here. respect!

looking forward to getting my 2 baby animals.. payment has been sent!!!!

 

[mattmoogus]

Hehehe thanks fatty. Its Joe that really rules though, hes doing the work. Im just throwing in the odd answer here and there while watching tv.

Im sure youll have a lot of fun with your BA pres. What config did you get?


M@

 

[fatty]

i got 2 channels, both the the jlm input tranny and the 99v. initially i was thinking of the oep but after reading your posts on here thought i'd try the jlm tranny.

i have some 1731 boards and some old 1970's british 1:10 trannys here...so i'm hoping to get a few more channels up and running on baby animal baords eventually. but it's taken me about 2 years to get around to fiinally ordering these first 2....so that might take a while :grin:

 

[Schmilsson]

[quote author="rodabod"][quote author="eskimo"]
So a 99v with the OEP at 1:12 with a JLM111DC out at 1:2 should give me 72db?
I'm going for a stereo unit and want the 99v's but still need plenty of gain for ribbons and dynamics.[/quote]

Just keep an eye on what the input impedances ends up being as this will affect the sound you get from your dynamics and ribbons.[/quote]

I realize I need a better understanding of impedance and what different transformer ratios does.

My idea has always been to go for a JLM14 - 99v - JLM111DC.
And I'd love two for stereo recordings.
The possible lack of gain is worrying me though.

Sure there's the hybrid, but my gut says 99v, and there's the dual 99v but my wallet and safety thinking says no, and since I'm new to this I believe the BA is just the best way to go.

 

[skipwave]

Roddy means calculate the impedance reflected to your mike.
Assuming your mikes are 150ohms output imp:

> 1:6.45 ratio, you want to load the secondary with about 65k, to reflect 1.5k to your mike.

> 1:12.9 ratio, load secondary with 250k.

Bridging the 150ohms output from the mike into 1.5k loading (as seen at the transformer primary) is for [EDIT] minimal loss (Roddy reminded me that the 1 to 10 loading is not optimal for power transfer or forward voltage transfer, but rather a compromise for minimal loss) [/EDIT]. Someone will correct me if I've buggered this explanation up.

Grab the super-handy Transformer Math Excel sheet created by FunkyDiplomat THREAD

 

[rodabod]

What he said!

Transformers "reflect" imnpedances across from the primary to the secondary and vice versa. Transformers with a turns ratio higher than 1:1 reflect impedances relative to the square of the turns ratio.

a 1:6.5 transformer will make the impedance connected to the secondary look like that impedance divided by 6.5 squared at the primary.

Hence, a 1:12.9 transformer will make the input impedance smaller, unless the load at the secondary is changed.

I haven't looked at the JLM page to see if they have already suggested values which they may have done.

Having the mic loaded with an impedance 10X that of the mic is a compromise - it is not maximum power transfer (happens when load is same impedance as source) and it is not completely biased towards maximum voltage transfer either, otherwise we'd make the load higher.

The Shure transformers guide on the net is a good beginners guide.

 

[Schmilsson]

Thanks a lot!
I'm getting some of it :wink:

http://jlmaudio.com/Baby_Animal_Mic_Pre.htm they have a chart there.

I'll start with the shure guide, good tip.

edit: Just checked and all my mics (421,408,m200,m260) happened to be 200ohms

 

[mattmoogus]

Eskimo, if your ribbon mics are Beyers, I can reccomend from personal experience using the little Beyer 1:10 mic input transformer (I can never remember the number). Load the secondary with 100k. I have an MCI pre with this arrangement and its probably my fave pre for my M200, except for not having quite enough gain.

Joe reckons you might run into trouble trying to get that much transformer gain with the 1:13 OEP. Remember youre feeding it with the output transformer in the ribbon mic which is already doing a massive step up. It might work but its something youd just have to try.

Id definitely reccomend either using the Beyer or 1:4 with a Hybrid and the 1:1:1. If you used the 1:4 you can add a variable impedance pot which will let you optimise the pre for your ribbons or for moving coil or condensor mics. This might work with the Beyer too but youd have to try it.

OR even better, getting a dual 99V kit as then you have heaps of options, but you said you cant afford that...



M@

M@

 

[Schmilsson]

How about stacking the pre's? Would that be a bad idea? Or perhaps a good idea with twice 99v-color and the possibility of gain staging?

I usually record one channel at a time, unless I'm recording drums but then gain won't be an issue.

I'm certain I'll have enough gain most of the time, it's just that ribbon miked acoustic every now and then that I'm concerned about.

Sorry to be such a pain in the ass, but on the other hand you'll be getting my money any day now. :wink:

 

[OverSound]

I picked up 4 of these babies a week ago and stuffed the boards over the last 24 hours. While looking at the chart on the jlm web site,
www.jlmaudio.com/Baby_Animal_Mic_Pre.htm
I noticed that you can add variable imp by adding "10k+100k Pot" instead of the fixed imp with just a 10k resistor.

How do I make this work? And should I really bother?

Sorry for the hurried and forward tone. I've inhaled so much solder smoke that I'm either High or temporarily retarded. So not the greatest first post but any light that can be shed on this would be of great help.

 

[unheardof]

Yeah, it was discussed over on this thread, where Matt suggests swapping out the 10k with a 5k in series with a 100k pot. This would allow you a lower impedance than what you get with a 10k, so I guess this would be preferable to a 10k+100k. That is, unless they tried 5k and it didn't work for some reason.

I am planning on adding this to my Baby Animal, but haven't found the 100k pot locally and I don't have anything else I need to order right now. I'll probably use a 4.7k resistor because that's what I have. If anyone has tried this yet, please share your results!! :thumb:

 

[OverSound]

Yeah I saw Matt's post, but when I saw the table on their site I assumed (dumb me, I know) that that would be the way to go. So how would you actually hook the 10k+100k pot to the circuit? Or more specifically what wires would go where? Of the 3 lugs and so on? I'm rather new to this so extrapolating from some of this has been a little tough. I suppose I might have brain overload from staring at those dang boards and schemo's for so long.

Thanks,

Brad

 

[unheardof]

What I'll probably do is replace the resistor on the board with two wires going to where the pot is mounted. I'll mount the resistor directly to the middle terminal of the pot and one of the wires to the other end of the resistor. Then connect the other wire to the left terminal (if you are viewing the pot from the front, knob side). The right terminal should not be connected. This will make it have the highest impedance at the full clockwise rotation of the knob, and the lowest at the full counter-clockwise. (or anti-clockwise for you folks that don't speak American) :grin:

You can think of a pot like a fader (and a fader is a type of pot). The terminals on each end are the top and bottom of the fader, and the middle terminal is like the fader knob. As you move the fader (or turn the pot), you are changing the resistance. You are basically splitting one fixed resistance (between the top and bottom) into two smaller resistances (one between the top and the fader, the other between the fader and the bottom). Since we are going for a single resistance that is variable, all we need is one of these, but which one depends on whether you want the resistance to increase or decrease as you turn the knob "up".

If you have never seen the inside of a pot, it might help you to visualize it if you can open one up and see how the wiper moves across the resistance. If this is too basic, sorry, I just thought if you were new to this it might make it easier to explain the whole thing.

Also note that there are linear and audio taper pots. I'm assuming we are supposed to use a linear pot, but I'm not sure. The taper refers to whether the resistance rises in an even, linear fashion, or in some sort of logarithmic curve. There are many other tapers, and they all basically just affect how effective the knob is throughout its travel.

Can anyone confirm that we are supposed to use a linear pot for the variable impedance? Now that I think about it, I think a log taper would make more sense... :sad: :?: