JLM Baby Animal, how much gain?

I have built 16 Baby Animals, 8 API style (Cinemag CMI-8PCA, API 2520, JLM111DC) and 8 with all JLM parts. I also have 4 Neve 1290 preamps and I was thinking of finishing off my collection with something clean'ish but still with a little vibe.

I was thinking of using Jensen JT-16-B input transformer, 990c opamp and JT-11-BMCF output transformer.

How much gain could I expect to get from this combination as the input and output transformer are both 1:1

Probably a better question would be how do I work this out!!!

Anybody built a Baby Animal with this combination? Is there a better circuit for this combination?

Basic max gain should be ~ 20*log(10K/68) = 43dB. Then add your transformer gain which for 1:1s would be 0dB.

For a 990 opamp, you optimum source impedance for noise is higher than 200 Ohms, so IIRC either a 1:2 or 1:2.5 should prove to be a better idea in that respect.

Probably no harm in using a 1:2 on the output either; the 990 can drive lower impedance loads well.

That would total 55dB which is decent, and would still be "clean" if you stick with clean transformers like Jensens or Lundahls.

My BAs with 990s use LL1538s running at 1:2.5 with LL1517s running at 1:2 for the output. Changed the 51R output resistor to around half that value as the 1517 has fairly low primary inductance and I wanted very flat response.

Interesting, I did think about using the Lundahl 1538, certainly a cheaper option than the Jensen at around half the price.

With the output transformer that would give around 63dB of gain?

Did you get the shockmounts ok Rodabod?

TornadoTed said:

With the output transformer that would give around 63dB of gain?

Did you get the shockmounts ok Rodabod?

Click to expand...

It depends on your ratio configuration. Like I said, I'd aim for around 1:2 input for a 990 for noise reasons. 1:2 is a double of voltage, so 6dB gain.

Got the shockmounts! Thanks very much - I think I added a message to the Paypal payment.

Cheers,

Roddy

JT-16-B *is* 1:2. You should be able to run a 990C at up to 50 dB, see the John Hardy schematics.

Samuel