New toy - JLM Audio Baby Animal

PRHunt

PRHunt

I void warranties
I finally found time to assemble my JLM Audio Baby Animal 2.

For this build, I used Joe's custom 1:4 input transformer, John Hardy 990c opamps, and Carnhill output transformers. Because of the high gain of the JH opamps, I was able to tweak the gain to achieve about 78dB.

I have only done very quick listening testing to confirm operation, but so far so good. This preamp has variable input Z which certainly influences the timbre of the input signal.

Must say that after a long DIY drought, it sure felt good to smell solder again :cool:

And no finger burns for a change :facepalm:

Here are some pics. (Apologies for the size. I thought that the uploader might resize them...)
 

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Actually, a minor correction. Gain is 76dB. (Seems I can't add up :o)

But yes, the gain seems good and clean, and should work nicely with the ribbons that I have just put together! Don't think I'm going to need a Cloudlifter after all.
 
Cool build. I had mine built awhile back. I too used Carnhill transformers (CA-18-VTB2280) on half of the build. I went with OEP A262A3E on the input transformers. Right now I have OPA2604AP-ND OpAmps, but I have plans to upgrade them to the JH 900c. I was going to go with JLM opamps, but between the exchange rate and shipping, the Hardy's will be more bang for the buck. I have used pres with JH 990c and do like their sound.
 
The JH 990C is excellent value. Be aware that supply can take a while, over six weeks in my case. John is lovely to deal with, but I think he just gets snowed under from time to time.

Joe Malone suggested that a full 60dB of gain was attainable from the JH990c by using a smaller gain resistor, Rg=10ohm, and JH seems to verify this. That is what I did.

I've just bought a pair of JLM25HV op-amps (Joe's take on the 2520), with which I am going to build a very simple API 312 styled single gain stage mic preamp, adding Joe's FET DI, and a separate line level input. I'm going to use Carnhills in and out, just because I have them, so this preamp will be something of a hybrid. I'll need to be more conservative with gain, maybe 60 to 66dB overall.

Anyway, it's all good clean fun!

Paul
 
I did not build mine so I am not sure about the size of the gain resistor, I assume they were the ones in the kits. Mine are BA Duals, so I hope that won't be that big of an issue. I actually had to have a custom Power Supply built because we could not get the one I bought with the kits to work. It powers up now, so I am happy. I did not go with any DIs. I was planning on doing an API/Neve mic pre combo; maybe the JLM cost will drop by the time I am ready to buy.

Your second build sounds like it it be sweet too.
 
I have to ask, what are the resistors you put on the 5 and 8 pins on your transformers?
 
Fishmed said:
I have to ask, what are the resistors you put on the 5 and 8 pins on your transformers?
Click to expand...

This is a Zobel network on the output to help ensure that the output doesn't oscillate. It is a 1.5kOhm metal film resistor in series with a 0.01uF cap across the output.

To be honest, I don't know if it is strictly required, but several schematics I have seen in which the Carnhill is used have a Zobel installed. I do have a o'scope, but haven't bothered doing much testing.

Some schematics also place a load resistor of 820Ohm across the output. I didn't bother with that.

Hope that helps.

Paul
 
JLM kits are probably not for the absolute electronics beginner, since the kits do not come with detailed assembly instructions. So, you need to have some idea about identifying components, soldering and desoldering, what order to install components, as well as access to basic testing gear and the know-how to use it.

That said, JLM hosts a forum which features construction threads for the major kit products, and Joe (Mr JLM) is one of the most helpful blokes around, who is always willing to provide assistance.

But I encourage everyone to build something, at least once!
 
PRHunt said:
The JH 990C is excellent value. Be aware that supply can take a while, over six weeks in my case. John is lovely to deal with, but I think he just gets snowed under from time to time.

Joe Malone suggested that a full 60dB of gain was attainable from the JH990c by using a smaller gain resistor, Rg=10ohm, and JH seems to verify this. That is what I did.

I've just bought a pair of JLM25HV op-amps (Joe's take on the 2520), with which I am going to build a very simple API 312 styled single gain stage mic preamp, adding Joe's FET DI, and a separate line level input. I'm going to use Carnhills in and out, just because I have them, so this preamp will be something of a hybrid. I'll need to be more conservative with gain, maybe 60 to 66dB overall.

Anyway, it's all good clean fun!

Paul
Click to expand...

Did you ever get your mic pre with the JLM25HV op-amps built? If so, how do they compare to the JH 990c?
 
Not yet built! Other projects and general family and work life invtervened. In the meantime, I revised plans and bought tranformers from Jeff Steiger (Classic Audio Products of Illinois - Classic API) which are close equivalents of the older transformers used by API. So the API-style project will proceed, but not just yet!
 
PRHunt said:
Not yet built! Other projects and general family and work life invtervened. In the meantime, I revised plans and bought tranformers from Jeff Steiger (Classic Audio Products of Illinois - Classic API) which are close equivalents of the older transformers used by API. So the API-style project will proceed, but not just yet!
Click to expand...

LOL, I understand completely!!!! I still have not upgraded the op-amps on my pres.
 
One thing I did build in the meantime is a 4 channel JLM Baby Animal Neutral preamp.

They sound wonderful - clean and clear and smooth and quiet.

I installed these in a 2RU case. If I can get the finger out, I'll put up some photos.
 
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