Audio Research CD7's 6H30 tube rolling

I do not think that you have to burn in the new tubes as much. 24-48h should do. The parts that are most sensitive for break in are coupling capacitors - but you do not change them.

And do not worry about the long break in period. Try not to listen, as I did. 3 weeks of continous play is all it needs. Since you already did 170h, leave it for additional 10 days in reapeat and you will be done.

Elberoth2, have you had a change to try the CD7 with different feet? ARC states that the feet they use are balanced to the weight of the machine indicating that they have put some thought to using good feet.

However I notice that the rubber feet are the same as the CD3 mk1 and mk2. And in both of these machines, changing the feet produced an improvement in the sound.

I used aluminum pucks to support the CD3 on a Symposium Isis rack. If you are aware of how the Isis works, the top shelf is compound isolated with 2 sets of rollerblocks in the supports and the theory of the rack allows for the pucks to transfer vibrations within the cd player into the shelves.

In a blind A/B test using none vs 3 vs 4 pucks, I concluded that 4 pucks sounded the truest to the music.

Haven't tried changing anything on the CD7 yet but I'd bet the same will hold true as the construction of the machines look pretty similar.

I use a similar method with my CD3 MK2. I put 3 audio points under the player because my cabinet does not surpress vibrations very well. Wether or not it has made an improvement is hard to say but it gives me piece of mind.

I placed my CD-7 on 3 Vibrapods - it sounds much better this way.

Vibrapods sit on a Finite Elemente Master Pagode Reference stand, which in turn sits on 4 Finite Elemente Cerapucs.

It is a combination of stiff (Cerapucs) and soft (Vibrapods) couplers.

Right time for a quick update on the results of my tube changes for the CD7.

I've had a chance to install the 4 new NOS 6H30-DR tubes in the amp stage of the CD7 player and run it in for around 70+ hours.

Bottom line is that there is a change in the sound between the NOS tubes and the new Sovtek ones. Not a huge change but an identifiable one. With NOS tubes, you get more dynamics, air and detail over the new tubes. During the breaking in of the tube, the sound is harder but changes to tight and with plenty of details.

But the difference isn't in my mind worth all the trouble. You get much more change in sound playing with vibration and power control tweaks. So if I had to do it all over again, I would probably just stick with upgrading the tube dampeners and consider changing the player's rubber feet.

Not an easy test to perform actually as it involves cooling down the tubes, unscrewing the top (10 screws I think), removing the tubes and changing the dampeners, replacing the tubes, screwing back on the top and waiting for the warm-up again. So to hear the changes in the sound, required a dozen swaps or so (especially with changing the dampeners between the original double rings to Herbie's titanium single ring also). I used a number of tracks for the test but mainly piano music, Horowitz, Complete Masterworks Recordings Volume V, Clementi Sonata in E-flat major as the comparison track.

One thing to add is that the perceived changes are within my system only with my current setup. Overall I find the CD7 a highly optimized design as it stands and changes do not seem to make that much difference - the biggest being replacing the rubber feet with aluminum pucks to properly drain vibrations into the platform.

Also during the research stage for the 6H30-DRs, I found the following information scattered all over. For the record in case others are searching for the same info:

- Tube construction on bottom just after pins enter tube is different with Sovtek tubes. There is an extra square piece not found on Sovtek tubes. Tip of DR tube is red whilst Sovtek is gray/black.
- Reflektor Corp Saratov factory used to make the 6H30-DRs
- Victor Khomenko 06:35:16 12/19/06 (0)
I looked at some samples and I think I would be able to spot the NOS DR from that vintage. All the EB tubes I looked at - and they came from several totally unrelated lots, but all made after 1999 - have very pronounced tool marks on the plates, on the folds facing out, and they are also shiny in that area. By comparison that area on the NOS DR tubes is always smooth, satiny, not shiny and with no visible tool marks.
The tool marks are left by the break tool. Whether or not these are universal distinctions I can not tell you, but based on a small sample it seems so.
- Victor Khomenko 07:33:13 08/09/07 (0)
Given that you have that question, also given that the NOS tubes are still available at reasonable prices (probably not for too long), I would just buy it and try. Most people do agree the NOS version sounds better.
BTW, they both have that PI in them, which stands for miniature package. As far as I know, the current Sovtek tubes are 6H30PI-EB, while the only NOS I have seen were the -DR's.
- Victor Khomenko 16:18:13 08/09/04 (1)
Well, the sources are the original Russian books and discussions with the factory people and Russian designers. In the nutshell it is what I posted below, but if you have some more specific questions, please let me know. Normally there would be three versions - no suffix, the -EB and the -DR, in their order of ruggedness.
The tubes produced in the Soviet era were selected for some still classified but extremely important application (some say it was the REAL Doomsday machine, a radiation- and EMP- hardened central computer in charge of making nuclear retaliation decisions), and therefore went through the most stringent selection. Those tubes of course are in limited supply and their prices high. For most projects the new production tubes should be just fine.
- Victor Khomenko 16:12:52 08/09/04 (1)
The main difference between the NOS tubes, that went through the MOST stringent quality control in existence, and the lesser varieties is in quality. There are many more noisy ones in the new ones, and the microphonics and grid leakage are much more common. But in some applications those are not important.
- Victor Khomenko 07:26:49 10/30/02 (0)
It is the same tube, just the misinterpretation of the Cyrillic notation. The Russian lettering looks like 6H30n-DP, but its phonetic equivalent is 6N30P-DR, so some people "translate" it, other keep it original. Personally I don't like "translation", therefore we introduced that tube here in the US as simply the 6H30.
- Victor Khomenko 08:28:55 11/16/00 (4)
***Thought this was a BAT exclusive what gives.
As far as I know we purchased a complete stock (less perhaps few pieces here and there) of the 1980's and early 90's production of the highest grade - the DR grade.
Furthermore, to the best of my knowledge, as of the late 1999 the New Sensor had restarted the production of that tube at its Reflector factory, albeit the somewhat lower grade - the EV, and I would presume this is what is being sold and used now. That new production tube is now available to anyone for good prices from the New Sensor.