Audio Research CD7's 6H30 tube rolling

The CD7 uses 6H30 tubes - 3 for power supply and 4 for the output stage.

Presently there are only new 6H30 tubes from Sovtek and Electro-Harmonix and NOS 6H30-DR tubes from the Russian military from around 20 years ago.

Some people have commented that the NOS tubes are sweeter sounding and have more "air" extension with their CJ or ARCref3 preamp equipment and others have commented that the latest new tubes (around 2005+?) sound so good that there isn't any difference anymore in sound.

Has anyone done tube rolling for this CD machine with the NOS tubes? And with what results? Would it be better to change the 3 power tubes or the 4 output tubes? Or all 7 tubes perhaps?

Thanks in advance for any comments!
I had both Audio Research and Conrad-Johnson power amps with new production 6H30-EB drivers a few years ago. I replaced them with pricey NOS -DR versions and I couldn't tell much difference. Maybe it might make a difference in a CD player, but based on my experience, I doubt it would be worth the difference in price.
I went ahead and ordered 4 NOS tubes for the output stage. The seller was kind enough to confirm that I could return them in mint condition less a restocking fee should I find that there is no change in sound.

The CD7 (brand new) started by sounding extremely detailed but bright. Perhaps bright isn't the correct term - more like forward. To the extent that it was tiring to listen to for long periods. I attributed some of this sound to the tubes and thus the search of a solution.

But after burining in for 150 hours or so, it's much better. The detail remains but the sound is now rounder and sweeter. The treble performance of the standard new tubes is now outstanding and I'm wondering if the NOS can do any better. It's already pretty incredible as it is now.
You mean to say that your cd player only has 150 hours on it? That's early to tube roll. This player would need about 400 hours of playing before you can judge the sound. To try to alter the sound now seems like a bad idea to me.
Hello Flkin , after 2 years of use , I decided to rollout the current 6H30P-EB tubes by the DR version , I swapped all the 7 tubes . Result is that the NOS tubes sound better
in every aspect the AR is famous for . But I also have changed the clock with its own powersupply ) Tentlabs , a Dutch brand ).This makes the CD7 even a more better player ,bigger soundstage and more air .I think that in my situation the clock is responsible for 60 % and the tubes for 40 % for the better sound.
Greetings from the Netherlands Hans
I have also bought a quartet of -DR tubes, but still waiting for the Halo Tube dampers to install them (I should get them next week).

The brightness you expirienced is typical for an early stage of burn-in. It will go away after some 300+ hours. After that, the player needs some 100h additonal hours of break in to sound its best (400h+ total).

I have left the player for 3 weeks straight in repeat mode to speed up the burn in process. Befor the burn in process is completed, the player sound medicore IMO. At some point (after 200h) I even wanted to return it to the dealer ! But after 400h it really starts to sing. For me it is a keeper. I went through some 10+ players in the $9-22k range before I decided to get CD-7.
Hi all!

Thanks for detailing your experiences. The comments that I should wait longer before commenting on the sound is very valid. It's just that 400 hours takes such a long time to pass when you are burning new equipment!

And when the new NOS tubes come, it will probably take ANOTHER 400 hours before I compare the sound again!

Hansk46 - Greetings from Thailand! Interesting that you can update the clock - didn't know that. I'll have a look at that too.

Elberoth2 - you ordered the Ultrasonic 9s also? So did I and they too are on the way. I wonder if the metal construction will be problematic inside a high-voltage machine such as the CD7. The older versions were made of some form of plastic.

Having used the CD3 mk1 and mk2 for a long time, I didn't really have any choice but to get the CD7! I haven't heard any other CD player as engaging and real as the ARCs. Right now (170 hrs perhaps?), it's already very good but the soundstage is still smaller than the CD3mk2 and the sound is not quite out of speaker box yet. I can tell distinctly that my Watt Puppies are there whilst I couldn't with the CD3mk2.

After you get the NOS tubes and have burnt them in, please let us know your opinion. I plan to do the same.

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.
hi elberoth2:

i would be very interested to hear what players you owned before buying the arc.

i am considering a cd player and my short list includes the amr 77 and the marantz 7s1. i have heard the audio research player several times, but not in my own system.

i found the cd7 too focused for my taste, which is consistent with my impression of their preamps and amps, as well.
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.