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The owner of the Sunn 300T I've been working on told me that his post-processing Line Out--which he wants to use--wasn't working, but unless I fixed it by accident, I found that it was actually working.
Since the post-processing Line Out is controlled by the Master Volume, I asked him where he normally kept the volume controls. He told me that he keeps the input volume around 2-3 and the Master Volume never higher than 3-4; he also keeps the -6dB attenuator switched in. So, I'm thinking that the Line Out signal was simply a lot lower in amplitude than he was expecting. I think I also know why the original 6550s still test like new :-)
I was wondering if anyone has ever tried a 12AU7 (or 12BH7) in place of the 12AT7 driving the 6550s for lower gain. (I'm not someone who runs around swapping 12A_7 tube types without thinking carefully about it first, so don't worry about that.) I do realize that you'd have to make sure you'd still get the necessary bias range since the bias of the 12AT7 controls the 6550 bias.
In other words, I'm thinking that a higher preamp level with lower power section drive might work better for his purposes. Or perhaps he should use the Power amp pass-through as his Line Out or run his regular Line Out into a ~mic level input.
Just thinking out loud....
Since the post-processing Line Out is controlled by the Master Volume, I asked him where he normally kept the volume controls. He told me that he keeps the input volume around 2-3 and the Master Volume never higher than 3-4; he also keeps the -6dB attenuator switched in. So, I'm thinking that the Line Out signal was simply a lot lower in amplitude than he was expecting. I think I also know why the original 6550s still test like new :-)
I was wondering if anyone has ever tried a 12AU7 (or 12BH7) in place of the 12AT7 driving the 6550s for lower gain. (I'm not someone who runs around swapping 12A_7 tube types without thinking carefully about it first, so don't worry about that.) I do realize that you'd have to make sure you'd still get the necessary bias range since the bias of the 12AT7 controls the 6550 bias.
In other words, I'm thinking that a higher preamp level with lower power section drive might work better for his purposes. Or perhaps he should use the Power amp pass-through as his Line Out or run his regular Line Out into a ~mic level input.
Just thinking out loud....