990 questions

[rhythminmind]

I have found six 990's laying around in the shop. Two are labeled 224, Two are labeled 134, one is labeled 140, & the oddball is unlabeled. I'm not sure what they came out of. I noticed one of them is structurally different. They all say 24v. Would these work with A12 or J99? Would i have to mod the design?

[tpryan]

You'll have to ask John Hardy about the labels, but assuming they're functional they'll work fine in either the A12 or J99. They won't be at their best in the A12, however, because of the large resistances around the op-amp.

[rhythminmind]

Thanks for the reply. I'm a novice in this area. What are the drawbacks of the large resistances if used with the A12? (lame man terms)

[tpryan]

Noise and DC offset voltages will be higher because of the large input bias currents.

[rhythminmind]

I would like to use them as dedicated drum pres, So i wouldn't be pushing the gain very hard. What would you expect the noise floor to be around? Would i be able to adjust the DC offset with the stock a12 design? A12 Coloration aside do you think i would be better off with the t15's