Will Tung Sol 6550 Fit Ampeg SVT CL?

Yes they will fit. This tube store recommends this tube as part of their premium package: Ampeg Heritage SVT-CL - Ultimate Package (Heritage and CL are the same in terms of tube positioning).

Although they fit, because the tube is a coke bottle shape, there is less space between the tubes and this affects cooling. Many have used these tubes without any issues though.

The retainer springs are also tight against the tube. They can rattle with either tube type. If they do, slipping a length of high temp silicone tubing over the spring fixes it. Loud also sells the vintage style clamps that are used in the Heritage model. They can be retrofitted, there is also a Youtube video showing how to install them.

 

I did the retrofit power tube clamp on my CL-SVT, very easy upgrade, I personally would go with the Sovtec 6550's

20150525_131057 by Jessica Stacey, on Flickr

 

I'm happy with the JJ's in mine, personally. And not to brag, but my Heritage was the very first amp made using those newer low profile power tube clamps, and I would most definitely get some and swap out those weird spring contraptions.

 

on switching to tube base clamps. No more spring buzz either.

The Tung Sol 6550s worked fine in my SVT-CL and sounded great.