Premier 11 / KT120 tubes
Posted: Fri Apr 28, 2017 8:56 pm
I landed a Premier 11 today (not the 11A), at quite a good price. I gave it a good cleaning, touched up a few small nicks in the black paint, and polished the gold top and front panels. It's looking pretty much like new!
The tubes are of unknown age and origin--three of the four 6550s are missing the lettering, and the fourth is so faint that I cannot make out a manufacturer. The 6FQ7s are mismatched (two different brands), and the 5751s claim to be "JAN" tubes with green lettering, supposedly made in the USA. The amp is dead quiet, but I noticed that there is a channel imbalance--I had to adjust my CJ preamp so that the right channel is four stops less than the left, in order to center the image properly. I infrequently noticed a very slightly "ragged" sound on strong high frequency content, which also makes me believes the tubes may be past their prime. (Or maybe this thing is even more revealing than the Nelson Pass amp I had prior.
No problem, as I am already working on getting a new set of tubes. The KT120s have a sound that I like (I heard plenty of them at AXPONA last weekend), but they are a half inch higher than the 6550s and some of the other KT## tubes. I may have slightly less than half an inch of space between the bottom of the cage and the top of the 6550s.
So, here is the DIY part. I want to run the amp with the cage on it, mostly for safety reasons. I do not want to alter or bend the cage (it already has a slight warp to it, which I have mostly straightened). What I am thinking of doing is removing the side panels, and installing a black spacer of some sort underneath the side panels where they are bolted to the main part of the chassis. That would give the entire cage and side panels the needed lift, and should be stable enough depending on what kind of spacer I come up with. That gap will probably be mostly unnoticed, as the amp is on the large, open bottom shelf of my rack.
Has anyone attempted anything similar to this?
I will attempt to post photos once I get the new tubes and rig up some sort of spacer.
The tubes are of unknown age and origin--three of the four 6550s are missing the lettering, and the fourth is so faint that I cannot make out a manufacturer. The 6FQ7s are mismatched (two different brands), and the 5751s claim to be "JAN" tubes with green lettering, supposedly made in the USA. The amp is dead quiet, but I noticed that there is a channel imbalance--I had to adjust my CJ preamp so that the right channel is four stops less than the left, in order to center the image properly. I infrequently noticed a very slightly "ragged" sound on strong high frequency content, which also makes me believes the tubes may be past their prime. (Or maybe this thing is even more revealing than the Nelson Pass amp I had prior.
No problem, as I am already working on getting a new set of tubes. The KT120s have a sound that I like (I heard plenty of them at AXPONA last weekend), but they are a half inch higher than the 6550s and some of the other KT## tubes. I may have slightly less than half an inch of space between the bottom of the cage and the top of the 6550s.
So, here is the DIY part. I want to run the amp with the cage on it, mostly for safety reasons. I do not want to alter or bend the cage (it already has a slight warp to it, which I have mostly straightened). What I am thinking of doing is removing the side panels, and installing a black spacer of some sort underneath the side panels where they are bolted to the main part of the chassis. That would give the entire cage and side panels the needed lift, and should be stable enough depending on what kind of spacer I come up with. That gap will probably be mostly unnoticed, as the amp is on the large, open bottom shelf of my rack.
Has anyone attempted anything similar to this?
I will attempt to post photos once I get the new tubes and rig up some sort of spacer.