NOS Mullard 12AX7/ECC83 I61 vs I63

[SQUAREHEAD]

Mullard 12AX7/ECC83 I61 vs I63?
If you put each of these in a tube tester and they read EXACT readings in terms of strength and output, what is the tone difference?
I am using them in the front, V1 position in a few different guitar amps… I have never purchased I61 types, all of mine are I63's… which I really love…
I have a chance to buy 2 I61's that test at 122 per triode for each tube on a B and K 747 Dyna jet tester.
Those readings would be extremely high on my B and K 707 Dyna jet tester… that's the problem with buying tubes, everyone uses a different tester and none of them seem to line up. Ughhh
any advice would be greatly appreciated in terms of the tone of these things!
keith

[Roe]

I remember Larry describing these as blues vs rock

[danman]

I was actually trying out a 161 vs 163 Mullard in v1 of my 1986 build today. The only difference that I could tell was that the 161 seemed slightly smoother than the 163. The 161 was testing around 1300/1350 while the 163 tested at 1500/1525 on my Hickok 800, so the difference that I was hearing may be attributed to the lower trancsonductance. I did end up leaving the 161 in the amp because I preferred the sound slightly more. I think Larry's description is pretty accurate as the extra grit that I heard from the 163 would be better suited for rock.

[SQUAREHEAD]

Hey, thank you Dan… That's some good information, I have a few I61's coming and I'll have to compare them to my I63's that I have in my stockpile. I have heard that the I 61 is smoother, so we'll see… it's all so subjective at this point.

[danman]

I should have also mentioned that chords sounded slightly clearer with the 161 in V1. This may also be attributed to it having a slightly lower transconductance than the 163 I was using. In the end I left the 161 in V1, the 163 in V3 and a Raytheon blackplate in V2. A lot of guys have praised the Raytheon blackplates for their very neutral sound in the V2 spot, so I picked one up a couple of months ago and I must admit that it does sound very nice there!

[Roe]

I prefer the mullards in v2

[danman]

They sound great there also Roe! You just can't go wrong with a good Mullard in any of the positions!