Audio Research CD7's 6H30 tube rolling

I've played around quite a bit with the NOS 6H30's and they do indeed sound noticeably different from the current production Sovtek 6H30. How much affect they have on the sound will depend upon the particular component they are used in. I would generalize and say that they sound richer in the midbass through the midrange and de-emphasize the highest treble and lowest reaches of the bass range a bit. They sound less sterile and thin but also a little less articulate than the Sovtek 6H30. I've used the NOS tubes in combination with the Sovteks to get the balance I want.

In the CD7 I would recommend not changing the power supply tubes, especially the two toward the back of the chassis because they are a closely matched pair. Pull the three power supply tubes and you will see that two of them have a matching color dot on them bottom. Leave those alone. I'd also probably leave the other supply tube alone too.

Conceptually it makes sense to leave the faster and tighter Sovtek tubes in power supply (non signal) locations and use the NOS tubes for signal. It also saves you a bundle of money.

As a possible alternative with many NOS flavors abundant , 6CG7/6FQ7 tubes are available. These tubes have the same pin out as 6H30, similiar GM and can handle 250v. Definitely don't sub 6922/6dJ8 in the CD7.

I thought that by the nature of what the 6H30 was designed for, tight tolerances were standard and that all 6H30DR tubes manufactured were already matched very tightly.

The tube store where I purchased the NOS 6H30DRs from has a matching service for some extra money. But I don't believe it's necessary for DR tubes.

With that said, it should be noted that the CD7 came with Sovtek tubes marked 1-7 with instructions to place them in their respective sockets marked 1-7. So perhaps there is some selection required in the standard 6H30 tubes.

Reb1208, have you tried 6CG7/6FQ7 tubes in the CD7 or to replace 6h30 tubes in CD players/amp before? During my research for 6H30 background info, I didn't find any mention that there were replacement tubes for the 6H30. Some people in Audiogon wanted to try but there were some comments that they should not be replaced. I forgot with what they wanted to use.

Is it only theoretically possible or is it practically possible? If so, with what results sound wise? Please share your experience.

Any of you guys still using a CD7 in 2016?

I've been using my ARC CD-7 since it was new. I sent it back to the factory several years ago to have it upgraded to the "SE" version that upgraded the power supply. 

Here's how to make an already great sounding CD-7 sound much better: 

1.  Get the "SE" version or send your CD-7 back to the factory for the "SE" upgrade.

2.  Swap out the stock fuses for Synergistic Research Black fuses.

3.  Swap out the stock tube dampeners on all of the 6H30's for Herbie's tube dampeners. 

I am NEVER going to sell my CD-7 SE.  Its not quite what we love about analog, but its darned close. 

That's it.