Originally Posted by GYang
Many times I heard that replacing stock tubes in modern high-end compressors, mic-pres etc. (as rule, new production Dragons, Sovteks or cheaper Philips, RCA etc.) with proven originals from New Old Stocks (Telefunken, Miniwatt, Amperex etc.) can add that desired 'vintage' character and sonically improve it the quite significantly.
Can anyone share experience with 12AX7 and 12AU7?
Any drawbacks (excluding prices for NOS that elevated to over 800$/pair for excellent NIB Telefunkens)?
A big difference.
I have a micpre that uses 6072 / 12ax7 for the input and 5687 for the output.
I ended up buying several Telefunken ECC83, the European number for 12ax7.
These specific Telefunken are a special, select low noise, NOS tube.
They were tested by Telefunken for low noise to use in medical equipment
and each has its own low noise test print out. Each is also identified with a blue and yellow dot applied by Telefunken. These were made in the Berlin factory.
Before I knew how long these tubes would last, it turns out I bought toooo many for my needs.
These are very rare because of the extra low noise testing and I have seen them only at the one supplier. They have ran out and I haven't seen them elsewhere.
If you are interested, I can sell a matched pair for $250. I can put them on ebay if you like, but I will have to charge more for the ebay commission.
I bought them from Europe and I am in Canada.
This pair is the last I will sell. I will be keeping the rest as I can't buy them anymore.
Pictures are available.
Tubes were measured on a TV-7 where minimal good is 32.
They are 52/52 on each tube.
These are very strong tubes.
For your own search of tubes, here are tube numbers that will work in place of 12ax7's ...
12ax7a, Ecc83, E83cc, 7025, 6072(a), 12AY7 (for a softer sound) CV4004, M8137, 10M, 5751, Ecc803, b759, 7729, 5965, 12av7 (softer sound), 6829.
These are all the subsitiute numbers I could find. Within each number there is also a range of quality so the selection grows even larger.